The following points highlight the sixteen orders under which bryopsida has been classified. The orders are:- 1. Tetraphidales 2. Buxbaumiales 3. Polytrichales 4. Dawsoniales 5. Archidiales 6. Dicranales 7. Fissidentales 8. Syrrhopodontales 9. Pottiales 10. Grimmiales 11. Encalyptales 12. Funariales 13. Eubryales 14. Isobryales 15. Hookeriales 16. Hypnobryales.
Order # 1. Tetraphidales:
In the Tetraphidales, consisting of the single family Tetraphidaceae (Georgiaceae), the peristome, as seen in Tetraphis (=Georgia), is formed of the entire tissue lying within the single layered operculum and remains adherent to the upper part of the columella. This mass of tissue splits into four thick triangular segments (Fig. 463) almost looking like the four valves of the Jungermanniale capsule.
The peristome is certainly more analogous to that of Polytrichum than to those with the articulated teeth of the Arthrodonteae. The protonema is partly thallose in this order.
Tetraphidales are not represented in India.
Cohort II. Buxbaumiidae (Buxbaumiinales):
These are peculiar mosses with a peristome differing much in its construction as described below.
Order # 2. Buxbaumiales:
The Buxbaumiales peristome is double, formed of 3 to 6 concentric amphithecial layers. The outer peristome (exostome) is formed of 1 to 4 series of slender teeth while the inner peristome is a thin tabular membrane resembling a truncated cone showing 16 or 32 folds or plicae. Both peristomes are formed of thickened cell walls only and not of entire cell groups which is the case in Tetraphidales and Polytrichales. Basic chromosome number n = 8 or 9.
Family 1. Buxbaumiaceae:
The protonema is filamentous, persistent and the gametophyte is extremely reduced (with scarcely any leaf). The exostome and endostome are as described above but in B. aphylla, the outer peristome is missing.
Genus 1. Buxbaumia (1 species—B. himalayana recently discovered by Udar et al from Deoban in U.P. Himalaya).
Family 2. Diphysciaceae:
The protonema is thallose shield-shaped and the gametophytic plant is normal. In the peristome the exostome is missing and the endostome is a pleated (16 plicae) asymmetrical tube which shows a spiral twist (Fig. 462).
Genus 1. Diphyscium (3 spp.)
Genus 2. Theriotia— found only in Kashmir (W. Himalaya).
Cohort III. Polytrichidae (Polytrichinales):
Mosses of this group differ from the common Eubryinales in the solid peristome teeth derived from several concentric layers of cells.
There are two orders:
Order # 3. Polytrichales:
Usually sturdy mosses of the hills. In Polytrichales the peristome is formed out of a single annular series of cells. In this layer curved dividing lines in the lower cells, form continuous bands of many cells (Fig. 464—I, II, III). The uppermost cells remain thin-walled and are ultimately resorbed (Fig. 464-IV) giving rise to 32 or 64 (rarely 16) separate solid teeth in a ring.
The tips of these teeth remain attached to the drum-top like tympanum formed out of the top cells of the columella. Leaves show longitudinal lamellae on the upper face of entire leaf or on vein only.
Basic chromosome number n = strictly 7.
Family Polytrichaceae:
Genera: 1. Atrichum (= Catharinaea) (6 spp.), 2. Oligotri- chum (1 sp.), 3. Lyellia (1 sp.—Fig. 465), 4. Pogonatum (34 spp.), 5. Polytrichum (5 spp.).
Genus Pogonatum:
Pogonatum and Polytrichum are the two dominating genera of the family Polytrichaceae. Dixon did not recognise Pogonatum as a separate genus and most British books include Pogonatum within Polytrichum although Pogonatum is internationally accepted as a separate genus.
Pogonatum is the largest genus with about 199 species all over the world of which 34 are known from the temperate hills of India and Ceylon. Of these, 28 species are known from Easteri) India, 10 species from the Western Himalaya and Kashmir and 10 species from South India and Ceylon.
Pogonatum is very common on rock soil in the hill- stations of India where 3 species—P. aloides, P. microstomum and P. junghuhnianum are common. Pogonatum microstomum, the common sturdy moss of the Himalayas and the Ghats, are referred to in the following descriptions.
The Gametophytic Plant:
The base of the erect Pogonatum stem (Fig. 466A) is usually described as rhizomatous. It is not a rhizome in the usual sense but is slightly stouter and stiffer (with more thick-walled tissue) than the stem above. Numerous rhizoids develop from this region. The individual rhizoid cell is thick-walled, elongated and with oblique walls.
The multicellular rhizoids occur as strands and a number of these occur twisted in a rope-like manner forming strong cable-like strings as shown for Polytrichum (Fig. 471D). On the upright stem the lower leaves are very small, scale-like and much paler in colour. The leaves grow in length by a two-sided apical cell. The upper leaves are crowded together spirally spreading out from the stem and are rather stiff.
The leaves are comparatively larger than in other mosses. The base of each leaf is broad, somewhat sheathing and paler in colour. The upper part is deep green to brown or reddish in colour, gradually tapering with a serrated margin. Most of the leaf is occupied by the thicker midrib (Fig. 466C), there being only a very narrow wing-like thinner lamina on the two sides.
The upper surface of this ‘midrib’ (i.e., most of the leaf) is completely covered by parallel longitudinal vertical plate-like structures called lamellae (Fig. 466C & E) somewhat like the gills of Agaric fungi. The top row of cells of these lamellae differ from species to species.
In Pogonatum microstomum each tip cell is split into 2- flask-shaped cells. A t.s. of leaf (Fig. 466E) shows the midrib with patches of thick-walled cells and sectional view of the lamellae—each 4 or 5 cells high.
The growth of the stem is by an apical pyramidal cell with 3 cutting faces. The anatomy of the mature stem of both Pogonatum and Polytrichum is rather complicated. Pogonatum is somewhat simpler. The stem (Fig. 467) is surrounded by an epidermis which gets broken up in the upper part where the stem outline becomes irregular due to the presence of a number of leaves.
Inside this is the zone of the cortex which is formed of living cells full of starch. The outer thick-walled, more deeply coloured, elongated cortical cells pass on to lighter, compact, parenchymatous cells of the cortex.
The innermost cells of the cortex contain more starch and have been likened to an irregular, rudimentary pericycle. The cortex shows here and there groups to cells representing the leaf traces. The leaf traces join the midribs of leaves to the central hydrom cylinder of the stem. Inside the cortex there is a zone of elongated cells with protoplasm but no starch which is likened to the sieve tubes and are called leptoids.
It has very recently been demonstrated that the leptoid cells are demarcated by oblique intervening cells which are nothing but porous sieve plates almost as in higher plants. The leptoid cells are interspersed with cells containing starch and this zone is called the leptoid mantle.
The centre of the stem is the central hydrom cylinder where there are two types of cells elongated thick-walled cells with living contents called stereides, and similar cells devoid of cell contents called hydroids. The hydroids are considered as the conducting strands by some but others doubt if there is any conduction of water at all. The leptoids and hydroids are much more clearly seen in Polytrichum (Fig. 472).
Vegetative Reproduction:
Pogonatum gametophytio plants are usually perennial. The vegetative shoots grow indefinitely, specially by proliferation of the male plant, and they may break apart to form independent plants. Another way of vegetative reproduction is by the development of bud-like gemmae on the rhizoids as seen in Polytrichum (Fig. 471D).
All gametophytic parts are also known to give rise to secondary protonemata behaving like the original one. This is called regeneration, a very common phenomenon in most mosses.
The original protonema is also known to divide into a number of protonemata or to give rise to gemmae on it. Protonemata are also known to develop out of sporophytic parts. This is apospory as the protonema is being developed on the sporophyte without the intervention of spores. A gametophytic plant developed on an aposporous protonema is diploid and not haploid like the normal gametophyte.
Sexual Reproduction:
Most Pogonatum species are dioecious, the antheridia and archegonia developing on separate plants.
In the male plant (Figs. 466B and 468), the top leaves are specialised, coloured red or orange and form something like an involucre which is called the perichaetium. This forms a flower-like head (Fig. 468A).
Inside this structure there is a cluster of plants antheridia and filamentous paraphyses at the base of each perichaetial leaf (Fig. 468B) so that the structure is compound and not simple as in the cases of Semibarbula and Funaria described later. This compound nature is not clear when mature.
The tip of the stem in the centre of this structure is left free for farther growth (proliferation) into a new shoot. Each antheridium is a club-shaped structure with a short stalk. In its development, the antheridium initial divides transversely into two cells the lower of which is the stalk initial and the upper the primary antheridial cell.
The stalk does not develop much but the primary antheridial cell elongates by a two-sided apical cell.
The latter first forms a filament, and then by periclinal divisions it forms a jacket of one layer enclosing androcyte mother cells. Each androcyte mother cell divides further forming androcytes or sperm cells within each of which develops a biflagellate, coiled antherozoid or spermatozoid (Fig. 468C). The androcyte also contains lot of mucilage. The mature antheridium (Fig. 468B) is a club-shaped structure with a short stalk.
The archegonial cluster (Fig. 468D) develops at the tip of the female plant. There are usually three archegonia in a cluster which are surrounded by filamentous paraphyses and then the perichaetial leaves. The apical cell of the stem itself is consumed in the development of the archegonia so that there may be no further proliferation.
The archegonial initial, which is the tip growing cell or a cell quite near it, divides by a transverse wall forming an upper primary archegonial cell and a lower primary stalk cell. The primary stalk cell forms the short stalk while the upper archegonial cell lengthens by an apical cell with three cutting faces.
This upper part ultimately organises the archegonium proper (Fig. 468E) with the venter and the neck containing the egg, the ventral canal cell and the neck canal cells inside. The top growing cell remains as the cover cell. Archegonia of mosses are longer than those of the Hepatics and that of Pogonatum shows a specially large (about 12) and variable number of neck canal cells.
Fertilisation:
When mature, and in presence of a film of water covering the plants at this time, the antheridia burst by the disintegration of the top cells. The neck and the ventral canal cells in the archegonia together with the top cover cell also disorganise leaving a free passage to the egg.
The decomposed substance coming out possibly contains some chemotactic substance like sugar attracting the swimming sperms which now get access to the egg. Ultimately, a single sperm fertilises the large spherical egg forming the diploid zygote.
Sporophyte:
The zygote invests itself with a cell wall, becomes brownish, enlarges and divides by a transverse wall into an epibasal and a hypobasal cell which divide repeatedly organising a young embryo (Fig. 469A) with two terminal growing cells at the two ends each with two cutting faces. The lower end forms the foot and the upper end the seta and the capsule.
The archegonial wall also enlarges simultaneously and becomes fibrous forming the calyptra (Fig. 466A) enveloping the young sporophyte.
As the sporophyte lengthens, the calyptra breaks, only its upper part remaining attached to the tip like a cap. A long, slender sporophyte is gradually formed (Figs. 466A & 469C). The lower part of this (formed from the hypobasal cell) burrows down into the tip of the gametophyte forming the foot.
The upper part elongates as a narrow slender structure bearing the calyptra at the tip. The capsule differentiates last in the region covered by the calyptra. In this capsule part an amphithecium surrounding an endothecium is organised. The amphithecium forms the multi-layered wall or jacket of the capsule while the endothecium forms the archegonium from its outer layers and the columella from the axial layers.
In the mature sporophyte (Figs. 466A & 469C), there is the foot, a sucking organ penetrating the tip of the gametophyte, the seta which is equivalent to the stem of the higher plants and the capsule completely covered by the fibrous calyptra.
The seta is green when young, reddish when mature and then turns deep brown. A t.s. of the seta (Fig. 469B) shows a strong epidermis of one layer, hypodermis of several layers of very thick-walled cells, a cortex of somewhat loose parenchymatous cells and a central strand of very small thin-walled cells.
An 1.s. of Pogonatum capsule (Fig. 469E) shows a wall several layers thick of which the one-layered epidermis with thick outer walls form the outermost layer. The inner cells of the wall are chlorophyllose and there are several layers of these. After that is a large cylindrical air space (outer lacuna) connected by string-like filaments of green cells with the outer wall of the internal spore sac cylinder.
The spore sac has an outer wall and an inner wall of 2 thin-walled cell layers each.
The spore sac contains the archesporium (usually two layers thick) when young and spores (developed as in other Bryophytes) when mature. After the inner wall of the spore sac there is another air space (inner lacuna) also traversed by green filaments.
Thus, the spore sac actually hangs free but bound down by the green filaments on both sides. The inner green filaments connect with the columella which is formed of colourless elongated cells (Fig. 469E). In Pogonatum, usually the columella is not cylindrical in cross section (Fig. 469F) but there are four wing-like expansions meeting the inner spore sac walls.
Thus, a longitudinal section of the capsule may be illusive if it passes through a wing.
The columella extends and swells upwards and forms a drum-like roof of the capsule called the epiphragm (also called tympanum) so that the spore sacs are not exposed (Fig. 469C & E). Above the tympanum there is a conical operculum which is usually beaked and is connected with the capsule by a ring-like diaphragm but there is no organised annulus.
Just above there is the peristome with a ring of 32 short teeth (Fig. 469C & E). These teeth (Fig. 469D) are solid, formed of bundles of fibrous cells (Fig. 464) and are different from the peristome teeth of the Eubryinales. Hence the name Nematodonteae.
The Pogonatum capsule shows no neck (apophysis) with stomata which is the case in Polytrichum. Stomata are not present on the capsule of Pogonatum.
When the capsule dries up, the operculum is broken loose by the pressure of the columella and the cells between the epiphragm and the teeth also break. The spores then come out of the cylindrical slit, the coming out being partially controlled by the hygroscopic teeth.
New Gametophyte:
The spore has a thick exine or exospore and a thin inline or endospore. The exine bursts at one point and the intine comes out like a green algal filament (Fig. 470B). This filament grows like a tube, cuts off cells and then becomes highly branched. The filament branches are green being rich in chloroplasts and form the chloronema.
Other filaments also develop from these which are thin and colourless and tend to go down and become the rhizoids. This entanglement of filaments is the protonema (Fig. 470G). Later, multicellular buds develop on the chloronema each one of which develops a new erect leafy gametophyte by a normal apical cell with three cutting faces.
Genus Polytrichum:
The genus Polytrichum is better known in the Western countries as it is so common and prominent there. It is, however, very rare and uncommon in India being found only in the comparatively inaccessible alpine regions’ of the Himalayas. All similar plants seen by the ordinary student on the hills belong to the genus Pogonatum.
Of the 111 species distributed over the frigid temperate regions of the word only five species (alpinum, densifolium, xanthopilum, formosum and juniperinum) are known from above 3600 metres in the Eastern Himalaya and only two species (alpinum and juniperinum) are known from the Western Himalaya.
The genus is not known in the warmer south of India or in the Khasia Hills or the extreme north-eastern India where alpine height is never attained.
Polytrichum generally resembles Pogonatum but differs in certain important characters pointed out below so that it is distinctly p different genus.
Gametophytic Plant:
The gametophyte plant (Fig. 471) generally resembles Pogonatum but is of a hardier nature. The stem anatomy is more developed and differentiated (Fig. 472). The leptoid and hydroid cells are more clearly developed (Fig. 472B).
The leptom mantle is demarcated on the inside by one or two layers of suberised cells full of staich and this zone is called the amylom layer or the hydrom sheath. Hydroids sometimes occur in groups of two and three when the cell walls between them are found to be very thin and delicate.
On the whole the central strand simulates some characters of a real vascular strand as seen in an 1.s. of the central strand of Polytrichum formosum depicted by Ruhland (Fig. 472B).
The rhizoids of the Polytrichum gametophyte show remarkable twisting and gemmae for vegetative propagation are very common on these (Fig. 471D).
Sporophyte:
It is in the sporophyte capsule that Polytrichum and Pogonatum differ very distinctly. The capsule in Polytrichum (except in Polytrichum alpinum) is usually angular (Fig. 473A) and not round. Unlike Pogonatum where there is no neck or apophysis with stomata, Polytrichum neck is generally marked off by a constriction from the main capsule’ (Fig. 473A & B).
This apophysis, internally, shows a central strand which is always (even in species where the apophysis is not prominently developed) surrounded by a mass of lax chlorophyllose cells and is surrounded by an epidermis with many stomata. The peristome shows solid teeth as in Pogonatum but the number of these teeth is 64 and not 32 as in the case of Pogonatum.
Order # 4. Dawsoniales:
The fourth order Dawsoniales of the Cohort Polytrichiidae comprises of the single family Dawsoniaceae with bristle-like (like a broomstick) peristome teeth.
Here the peristome forming amphithecial layer is broad and formed of a large number of cell layers. In this layer interspersed vertical rows of cells become thick-walled (Fig. 474-II), the intervening thin-walled vertical rows are resorbed so that thickened bands of cells stick out like bristles in several rings giving rise to a broomstick-like peristome (Fig. 474-I). The order is not represented in India.
Basic chromosome number n = strictly 7.
Section II. ARTHRODONTEAE
Cohort IV. EUBRYIIDAE (EUBRYINALES):
The Arthrodonteae peristome is formed of only 2 or 3 layers of amphithecial cells. The teeth are membranous or scaly being actually formed of the thickened walls of the cells which are like plates (called lepos in latin), the thinner parts being resorbed.
They are articulated or transversely barred showing the joined up walls of cells of which they are formed. The Arthrodonteae are divided into two series Haplolepideae and Diplolepideae.
Series I. Haplolepideae:
In Haplolepideae the teeth are placed in a single row. Each tooth shows a single row of external plates and, usually, a double row of internal plates as may be seen by looking at the outer and inner faces of the teeth. The two sets of plates or scales (lepos) come from two concentric layers of cells. But, these teeth may be differently split longitudinally in the different orders.
Order # 5. Archidiales:
The single family Archidiaceae with the single genus Archidium was formerly included within the next order Dicranales. But the sporophyte structure is so simple and different that Cavers raised it to a cohort and Reimers considered it as an order and placed it at the top of the Eubryiidae. The sporophyte is cleistocarpic without any columella or peristome.
At least in these plants it is not reasonable to consider this cleistocarpy to have arisen by reduction. It is therefore, better to consider it as a separate and problematic order. The capsule is a mere bag with a one-layer thick jacket enclosing a few large spores (Fig. 475B) and a short foot.
There is no columella and the endothecium is entirely sporogenous. 3 spp. of Archidium (indicum, microthecium & octosporum) are known from South India, 1 sp. (birmannicum) from near Calcutta (Fig. 475A) and from N. E. Assam and 2 spp. from Burma.
The position of the Archidiales is somewhat problematic. Archidium has a gametophyte which quite fits within the Dicranales. The chr. no. (n=13) also resembles the Dicranales. But, its sporophyte is unique, being as simple as the simplest Hepatics. There is little logic in supposing that it is a degenerate from the peristomic Dicranales as is the case with many other cleistocarpic species.
Its peristome differs so much from the other Bryidae that several Bryologists think that it deserves a rank even higher than an order to a cohort. Hence the name Class Archidiopsida by Cronquist, Takhtajan and Zimmermann. Although the arguments have weight, the taxon is kept only as a separate order here, pending farther ellucidation by farther work.
Order # 6. Dicranales:
The order Dicranales is acrocarpous, haplolepideous and usually with 16 dicranoid peristome teeth but in Ditrichaceae and some genera of Dicranales the teeth are more finely or irregularly split (ditrichocranoid) while in Pleuridium the peristome is missing.
Basic chromosome numbers n = 11, 12, 13.
Family Ditrichaceae:
Genera: 1. Pleuridium (3 spp.), 2. Pleundiella (1 sp.), 3. Garckea (2 spp.), 4. Ditrichum (12 spp.), 5. Ditrichopsis (1 sp.), 6. Ceratodon (2 spp.), 7. Distichium (5 spp.).
Family Dicranaceae:
Genera:
1. Bruchia (1 sp.), 2. Trematodon (13 spp.), 3. Wilsoniella (1 sp.), 4. Anisothecium(3 spp.), 5. Aongstroemia(2 spp.), 6. Aongstroemiopsis(1 sp.), 7. Microdus (7 spp.), 8. Dicranella (11 sp.), 9. Campylopodium (3 spp.), 10. Microcampylopus (1 sp.), 11. Campylopodiella (2 spp.), 12. Campylopus (including Thysanomitrium-4:6 spp.), 13. Dicranodontium (16 spp,) 14. Brothera (2 spp.), 15. Paraleucobryum (2 spp.), 16. Amphidium (1 sp.), 17. Atractylocarpus (2 spp.), 18. Rhabdoweisia (1 sp.), 19. Dicranoweisia (4 spp.), 20. Symblepharis (3 spp.), 21. Dicranum (14 spp.), 22. Oncophorus (4 spp.), 23. Holomitrium (1 sp.), 24. Oreas (1 sp.), 25. Oreoweisia (2 spp.), 26. Leucoloma (11 spp.), 27. Dicranoloma (7 spp.), 28. Cynodontium (2 spp.), 29. Dicnemoloma (1 sp. from Ceylon), 30. Braunfelsia (1 sp. from Ceylon).
Aongstroemia julacea (Hook.) Mitt, discovered at an elevation of 19,800 ft. in the Rongbuk Valley off Mt. Everest perhaps marks the highest limit of plant survival.
Family Leucobryaceae:
Genera: 1. Leucophanes (4 spp.), 2. Leucobryurti (17 spp.), 3. Ochrobryum (4 spp.), 4. Octoblepharum (1 sp.), 5. Arthrocormus (1 sp. from Ceylon), 6. Exodictyon (2 spp.).
Order # 7. Fissidentales:
The Fissidentales consist of a single family Fissidentaceae which includes four genera among which the genus Fissidens (Fig. 476) is predominating and only this is found in India. This is mainly a tropical genus although some species are found on the temperate hills. Most species grow on soil and as many as 83 species are recorded from India.
Basic chromosome number anomalous (n = 5 to 24 known).
The clear diagnostic feature of the genus is the pair of sheathing lamini of the distichous leaves (Fig. 476B). Plants are acrocarpous. There is one ring of 16 peristome teeth (haplolepideous), each of the teeth being split into two (dicranoid) almost to the base (Fig. 476E).
Order # 8. Syrrhopodontales:
Acrocarpous, haplolepideous, usually epixylic and often gemmiferous mosses. Peristome not split (16) or absent altogether (Monocrartoid).
Family Calymperaceae:
Genera: 1. Syrrhopodon (16 spp.), 2. Thyridium (9 spp.), 3. Calymperes (37 spp.), 4. Calymperopsis (1 sp.).
Order # 9. Pottiales:
Acrocarpous, haplolepideous mosses. Peristome teeth not split, split into filaments (ditrichocranoid) or missing altogether. A few genera (e.g., Phascum) are cleistocarpic (no operculum or peristome, capsule sunk within leaves).
Family Pottiaceae:
Genera: 1. Anoectangium (9 spp.), 2. Molendoa (3 spp.), 3. Merceya (including Merceyopsis—6 spp.), 4. Astomum (2 spp.), 5. Hymenostylium (7 spp.), 6. Hymenostomum (4 spp.), 7. Weisia (4 spp.), 8. Gymnostomum (2 spp.), 9. Reimersia (1 sp.), 10. Rhamphidium (1 sp.), 11. Oxystegus (6 spp.), 12. Trichostomum (8 spp.), 13. Pseudosymblepharis (3 spp.), 14. Timmiella (1 sp.), 15. Tortella (7 spp.), 16. Pleurochaete (1 sp.), 17. Chionoloma (I sp.), 18. Leptodontium (2 spp.), 19. Bryoerythrophyllum (8 spp.), 20. Hyophila (14 spp.), 21. Didymodon (14 spp.), 22. Barbula (22 sp.), 23. Geheebia (1 sp.), 24. Bellibarbula (1 sp.), 25. Semibarbula (2 spp.), 26. Hydrogonium (11 spp.), 27. Prionidium (1 sp.), 28. Weisiopsis (1 sp.), 29. Beddomiella (1 sp.), 30. Pottia (1 sp.), 31. Hyopliilopsis (1 sp.), 32. Desmatodon (8 spp.), 33. Syntrichia (7 spp.), 34. Tortula (1 sp.), 35. Cinclidotus (1 sp.).
Genera Barbula, Semibarbula and Hydrogonium:
The original genus Barbula Hedwig shows so many variations that it has been thought proper by Hilpert and Chen to divide it into seven independent genera, viz., Barbula Hedw., Streblotrichum P. Beauv., Bellibarbula Chen, Prionidium Hilp., Semibarbula Herz. ex Hilp., Hydrogonium (C. Muell.) Jaeg. et Sauerb. and Bryoerythrophyllum Chen. An eighth genus Geheebia Schimp. should be added to these.
All these genera, excepting Streblotrichum and Prionidium, are represented in this area but the three genera Barbula, Semibarbula and Hydrogonium are prominent.
Barbula proper is mainly represented on the Himalayas. 22 species are known here of which Barbula constrict (Fig. 477A) Mitten is the commonest. Barbula is of a very sturdy habit, the leaf is rough because of papillose development of the leaf and midrib cells. The peristome teeth are like long papillose threads which are twisted together and wound like a cork-screw.
Hydrogonium is found in the Indogangetic plains and also on the Himalayas and other high mountains in this area. Hydrogonium arcuatum (Griff.) Wijk. et Marg. (Fig. 477B—Syn. Barbula comosa and Barbula gangetica) is a common species in the Indogangetic plains. It grows on soil.
The peristome teeth are as in Barbula but the leafbase shows elongated pelluicid cells distinguishing it from barbula and the plants are not so stiff.
Semibarbula differs from these two other genera in having a reduced peristome represented by a number of short papillose threads, too short to be spirally twisted (Fig. 482F). The leaves resemble Barbula but the plants are generally shorter.
The genus is mainly represented by Semibarbula orientalis (Web.) Wijket Marg. (Syn. Barbula indica Brid.) which grows all over India and is perhaps the commonest species of this group of mosses in the Indogangetic plains, growing on old walls, bricks and mortar. Its complete life history has been worked out by Banerji and Sen (under the old name Barbula indica) and is being described here.
Gametophytic Plant:
Semibarbula orientalis is a calcicolous (growing on substratum containing lime) moss growing during the rains and maturing in the cooler months all over the tropics in the Eastern hemisphere forming dense, green to yellow-green gregarious patches on old brick walls, mortar, etc., where it may get sufficient moisture and partial shade. The erect shoots are usually un-branched (Fig. 478A).
The axis bears small, spirally arranges leaves (Fig. 478B) and at the base there are smooth-walled, multicellular rhizoids with oblique walls.
The rhizoids and the lower part of the stem becomes brown with age. The growth of the stem is by an apical cell with three cutting faces so that the original leaf arrangement is tristichous which arrangement loses clarity in some portions. The leaf shows elongated thin-walled cells at base (Fig. 478D) and smaller, coarsely papillose cells (Fig. 478C) above.
The vein back also is coarsely papillose and, therefore, rough. A transverse section of the stem (Fig. 478E) shows a thin- walled central strand of vertically elongated cells (hydroid) and a cortex surrounding it.
Outer cortical cells contain chloroplasts when young but become thicker walled and brown when mature. A t.s. of leaf (Fig. 478F) shows a prominent midrib with a row of larger cells (deuter cells) in the middle flanked by thick walled (stereid) cells.
Reproduction:
(A) Vegetative Reproduction:
Vegetative reproduction is common in Semibarbula.
It may take place in a number of ways:
(a) New branches develop from the apices (proliferation by innovations) of older decaying plants and may develop new independent plants.
(b) Protonemal threads are known to develop from different gametophytic parts. These develop buds and new plants in the usual way.
(c) Multicellular gemmae or brood-bodies develop in clusters in the axils of leaves (Fig. 479A & B) as- well as tips of shoots. These gemmae get detached and germinate, developing filamentous protonemata which give rise to new plants in the usual way.
(B) Sexual Reproduction:
Semibarbula is dioecious. Male (Fig. 480A) and female (Fig. 478A) plants usually grow intermixed.
The antheridia grow in antheridial clusters (Fig. 480B), intermixed with long, multicellular, filamentous paraphyses, in apparently axillary positions. The cluster is covered by a few short bract leaves and in its growth the apical cell with two cutting faces intermittently cut off segmental cells some of which act as the antheridial initial (Fig. 480G) while other develop the paraphyses.
Thus, a short head is formed in which the antheridia and paraphyses lie in a bud-like structure surrounded by small leaves. The original apical cell usually grows developing the shoot further so that the antheridial bunch, takes up a secondary lateral position.
The antheridial initial cell with two cutting faces develops a short filament which, later, forms a jacket layer, the androcyte mother cells and a few cells at the tip forming the cover.
The androcyte mother cells at first do not form all the partition walls so that they look multinucleate (Fig. 480D), but, ultimately, each androcyte mother cell is partitioned off by a wall and soon divides into two androcytes or sperm cells each of which develops a single biflagellate, coiled antherozoid or spermatozoid inside it.
The androcytes remain surrounded by a lot of mucilage. The mature antheridium (Fig. 480E) is a club-shaped structure with a short stalk.
The archegonial cluster (Fig. 481A) develops at the tip of the main stem or a branch. Here the archegonia are surrounded by the paraphyses which again are surrounded by leaves (perichaetial bracts). The archegonia develop as the antheridia but each archegonial initial grows by three cutting faces. The original apical cell, usually, does not grow further so that the archegonia are always at the tip.
The mature archegonium (Fig. 481B) shows a swollen venter with multi-layered wall containing the large egg and a ventral canal cell, a long neck containing up to 12 neck canal cells in a row surrounded by a. jacket of one layer and four cover cells at the tip.
Sporophyte:
Fertilisation takes place as in Pogonatum. The development of the sporophyte also is, on the whole, like Pogonatum. The sporophyte shows the foot, seta and capsule (Fig. 482D) as usual. The calyptra (Fig. 482D) is quite different from that of Pogonatum. It is hood-shaped, split and stuck to one side to the capsule like a cape.
The capsule (Fig. 482C & E) has on its top a conical lid-like structure with a long beak called the operculum. This operculum is exposed when the calyptra falls off as a result of mechanical jerking’s. The operculum is attached to the main capsule by a ring of thin-walled cells called the annulus.
This is a ring of weakness and the operculum breaks loose at maturity along this line. When the operculum is shed a ring of 32 thread-like papillose teeth (Fig. 482F) shorter than in the two previous genera, and too short for any coiling, are seen to cover the opening at the tip.
The base of the capsule is called the apophysis or the neck. The cells of the apophysis are green and show stomata on the surface so that the capsule is not completely helpless from the point of its nutrition.
The main body of the capsule shows a central axial columella of larger cells, spreading from the apophysis to the operculum and cylindrically surrounded by a single layer of archesporium which again is surrounded by two layers of sterile cells. All these inner tissues of the capsule develop out of the endothecium.
The single layer of archesporium then develops 6 to 8 layers of sporogenous cells. These cells round up and form the spore mother cells which again give rise to the spores by reduction division. These endothecial layers are separated from the amphithecial layers by a cylindrical air chamber. Outside, the amphithecium forms the jacket of the capsule several layers in thickness.
At maturity, the sporogenous region widens forming a cylindrical spore sac in which the loose spores lie. The capsule is red-brown at this stage. With the shedding of the operculum, the spore sac becomes exposed at the tip and the spores are dispersed mechanically, their release being controlled by the peristome teeth which open and close the opening by hygroscopic movement.
New Gametophyte:
Germination of the spore is generally as in Pogonatum. The spores are small, light brown, with a thin exine or exospore and an intine or endospore (Fig. 470A). It germinates when it falls on a suitable substratum. The endospore comes out through an opening in the exospore in the form of a filament (Fig. 470B). Cases are known where several filaments come out of the same spore.
The filament forms a multicellular thread and becomes branched. The cells contain numerous discoid chloroplasts and these filaments form the chloronema. Later, other thinner pale-green filaments also develop and the rhizoids develop on them. This entanglement of filaments is known as the protonema.
On the chloronema multicellular buds develop (Fig. 470C). Such a bud ultimately develops a new erect, leafy gamelophytic plant by a normal apical cell with three cutting faces. The protonema is formed of branched filaments.
The life cycle is shown in Figure 483.
Order # 10. Grimmiales:
Acrocarpous mosses growing on rocks with leaf cells showing sinuose walls. Haplolepideous. Peristome teeth irregularly split (platycranoid).
Family Grimmiaceae:
Genera: 1. Coscinodon (1 sp.), 2. Schistidium (2 spp.), 3. Grimmia (17 spp.), 4. Racomitrium (9 spp.) (Pleurocarpous).
Series II. Heterolepideae:
Order # 11. Encalyptales
Family Encalyptaceae
Genus: 1. Encalypta (5 spp.):
The family with the single genus Encalypta has proved to be of great interest. The calyptra of this genus is strongly developed, persistent and falls off carrying the operculum. While the genus is uniform in all other characters, the peristome is highly variable in the different species—two rowed, one rowed or missing. There are diplolepideous as well as haplolepideous species.
Some species may also be related to the Arthrodonteae. So, Philibert considered this as a synthetic group related to the Arthrodonteae and from which the Haplolepideae and the Diplolepideae had arisen. Cavers placed the family in a separate series in between Haplolepideae and Diplolepideae.
Dixon also followed this plan. Encalypta is not known from Eastern India but as many as five species are known from the Western Himalaya and Kashmir.
Series III. Diplolepideae:
In Diplolepideae the teeth are usually in two rows although, in some cases, one row (or even both rows) may be suppressed. The peristome is formed of three concentric layers of cells. The outer peristome (exostome) teeth (usually 16 in number) look similar to the haplolepideous teeth but the outer face is formed of 2 rows of plates (hence, diplolepideous) while the inner face is formed of a single row of plates.
The inner peristome ring (endostome) is formed of very indistinct plates of more or less hyaline cells and is usually united at base (basal membrane) and then split into segments above.
The segments may sometimes be uniform and completely free so that the endostome is formed of 16 free teeth (c.f. Funariaceae). Those endostome segments may have between them very thin or filamentous segments called cilia which latter again may be appendiculate or simple.
The Diplolepideae is divided into two subseries:
Epicranoideae (exostome teeth overlapping endostome teeth or segments c.f. Funaria) and Metacranoideae (exostome teeth alternating with endostome segments c.f. Bryum).
Subseries 1. Epicranoideae
Order # 12. Funariales:
Acrocarpous, diplolepideous mosses. Capsule not cylindrical and the operculum without beak. Peristome teeth usually in two epicranoid rings but may be in one ring or absent by reduction.
Family Ephemeraceae
Genus: Micromitrium (=Nanomitrium) (1 sp.).
Family Funariaceae
Genera: 1. Physcomitrium (15 spp.), 2. Entosthvdon (16 spp.), 3. Funaria (7 spp.). Family Splachnaceae
Genera: 1. Gymnostomiella (1 sp.), 2. Splachnobryum (5 spp.), 3. Voitia (1 sp.), 4. Tayloria (8 spp.), 5. Tetraplodon (2 spp.).
Funaria Hygrometrica:
Funaria hygrometrica Hedwig is a cosmopolitan moss known from all over the world and from all the major hills of India. It is a very common Himalayan moss thriving best in the temperate heights. Funaria leptopoda Griffith (with the capsules more erect) found in the Himalayas, though reported as a separate species, should be considered as a variety of Funaria hygrometrica.
It is commonly found on semi- exposed rocky ground, walls, etc. It is often found as the first vegetation on burnt up land in these areas, specially where ash is present.
Gametophytic Plant:
The erect gametophytic plant (Fig. 484A) is about an inch in height with an erect radial stem (growing by an apical cell with three cutting faces) and spirally arranged simple leaves. The leaves are more crowded near the apex where they appear like a rosette though actually arranged in three rows corresponding to the three cutting faces when young.
This arrangement is lost in the mature parts. Branches arise on the main stem from extra-axillary positions. Leaves (Fig. 484C) are sessile, attached to the stem by a broad base, ovate elongate, pointed at the apex and with a smooth margin.
All normal mature leaves show midribs but very young leaves and the sparsely arranged small leaves at the base of the stem are devoid of midribs. The gametophytic plant bears at its base a strong, much branched rhizoid system which becomes brown and cable-like when mature.
A t.s. of the stem (Fig. 484B) shows a small central strand of long, narrow, colourless, thin-walled cells devoid of protoplasm. This is surrounded by a cortex of larger cells which contain chloroplasts when young. In a mature plant this chlorophyll is lost and the outer cells become somewhat thick-walled and reddish-brown.
The cortex also shows, here and there, some smaller cells or cell groups which are termed leaf traces although they end blindly and do not reach the central cylinder.
The outermost layer of the stem is the epidermis and this also contains chloroplastids. There is no stomata. The leaf, in cross section, shows a well-defined midrib while the lamina is only one cell in thickness. The midrib has a small central strand of narrow, thin-walled cells surrounded by a sheath of narrower cells with thicker Walls.
Lamina cells are elongated, lax, thin-walled; rectangular or rhomboidal and contain chloroplasts which divide ever) in mature cells.
Reproduction:
The plants may propagate vegetatively by branching and being cut off from the mother plant by decay and also by the development of secondary protonemata as in Semibarbula. The secondary protonema develop from anywhere and are diploid or haploid according to the tissue from which they are developing.
Asexual regeneration by gemmae (Fig. 485) is also common. These commonly develop on the rhizoidal branches of the protonema and are multicellular, brown, bud-like structures.
The gemmae are useful for propagation during unfavourable periods. The normal method of reproduction, however, is sexual. Funaria is monoecious but autoicous, i.e., the antheridia and archegonia develop on separate shoots of the same plant. The main shoot of the plant bears the antheridia. The female branch develops as a side shoot but, it is more vigorous and soon becomes higher than the main shoot.
In the antheridial shoot (Fig. 490 D, E), a number of bract-like leaves form a rosette called the perichaetium. This perichaetium surrounds a number of club-shaped, stalked antheridia and multicellular hairs known as paraphyses. The paraphyses in Funaria have swollen tips.
The archegonia also are borne in clusters on the archegonial shoot (Fig. 489G) but no Perichaetium is differentiated here. The archegonia and the manner of development of both archegonia and antheridia generally resemble that of Semibarbula. Fertilisation takes place in the usual way.
Sporophyte:
The development of the sporophyte is as in Semibarbula but the mature capsule has a different appearance. The mature sporophyte shows a poorly developed conical foot embedded in the apex of the archegonial branch; a long seta which is reddish- brown in colour and often twisted; and a pear-shaped, asymmetrical, bent, often bright orange-coloured capsule at the tip.
The tissues of the seta (Fig. 486) show more thick- walled cells, than in the gametophytic stem.
The mature pear-shaped, nodding capsule (Fig. 487A & 1.s. in 487B) is asymmetrical. The lowermost part of it is the apophysis or the neck which connects it with the seta below. The axis of the apophysis shows in the lower part a central strand of thin- walled elongated cells connected with, the similar tissue of the seta below. Above, the axial strand disappears into the columella.
This axis develops out of the endothecium and it is surrounded by a green spongy tissue formed out of the amphithecium. This spongy tissue contains abundant chloroplasts and air gaps like the photosynthetic tissue of leaves and serves the same function.
The spongy tissue is surrounded by one compact layer of epidermis regularly provided with stomata. The stomata (Fig. 487C & D) develop as in the higher plants but, when mature, often the two guard cells combine to form a ring-like single annular guard cell (fig. 487D). The stomata are regularly connected with air spaces.
Above the apophysis, the main part of the capsule is a slightly bent, cylindrical structure with the central columella of thin-walled parenchymatous cells which is constricted at the base just above the apophysis.
The columella is surrounded by the archesporium (one-layered) which latter is the sporogenous layer, becoming a spore sac when spores are formed by reduction division of the spore mother cells organised out of the archesporium. The sporogenous layer has an inner wall of one layer of small cells and an outer wall of 3 to 4 layers of such cells.
The columella, the inner wall and the spore sac are developed out of the endothecium while the outer wall of the spore sac and the tissues surrounding it are formed out of the amphithecium. The outer wall of the spore sac is surrounded by a big cylindrical air cavity traversed by strings of filaments of elongated green cells which form the trabeculae bridging the air space.
Outside this air space is the wall of the capsule formed of 2 or 3 layers of compact, colourless, parenchymatous cells bounded down by the outermost compact epidermis of one layer, which is devoid of stomata, may be green when young but becomes bright-brown or orange when mature.
The tip of the capsule has a complicated structure. It is not exactly on the apex but on one side as the capsule is asymmetric (Fig. 487 A & B). The columella extends into this part but the cells are a bit larger here. This is the only tissue out of the endothecium in this region —all the outer tissues being formed out of the amphithecium.
There is a notch where this top part joins the capsule proper. At this notch (Fig. 487A) there is an annular rim (or diaphragm) of small cells edging the mouth of the capsule.
Above the rim is another ring of slightly extended cells called the annulus. The three innermost layers of the amphithecium forms two sets of peristome teeth—in the outer circle is one ring of 16 larger brown peristome teeth ornamented With transverse bars-—and in the inner circle are another 16 peristome teeth which are thinner and of a paler colour (Fig. 487A & 488B).
The two rings of peristome teeth are the outer and inner rings called the exostome and the endostome respectively. The whole structure is the peristome. The outer peristome teeth are superposed on the inner (epicranoid). The outermost cells of this capsule apex form a dome-shaped operculum (Fig. 487A & B) which keeps the teeth covered.
At maturity, the distended cell walls of the annulus break and the loosened operculum is shed leaving the peristome teeth exposed (Fig. 487A). The peristome teeth are twisted spirally appearing somewhat like an iris diaphragm and the tips of the outer peristome teeth are attached to a small circle of a few small cells.
This attachment soon disintegrates and the outer peristome teeth, which are hygroscopic, show movements according with the presence or absence of moisture—thus helping the dissemination of spores.
The calyptra develops out of the old archegonial ventral wall as in other Bryophytes. It is found attached to the top of the young capsule like a hood.
New Gametophyte:
The small round spores (Fig. 488C) containing chloroplasts germinate and develop a protonema (Fig. 489) composed of a chloronema and rhizoidal branches as in other mosses.
Detailed observation of this protonema shows that the first formed chloronema soon organises a more mature type of protonemal threads which have been named caulonema by Sironval (1947). Buds giving rise to new gametophytic plants develop on this caulonema. Others (viz. Alsopp & Mitra, 1958) did not note any distinct caulonema, the rhizoidal branches developing from the base of the chloronemal threads.
The partition walls are at right angles in the green chloronema threads which are full of chloroplastids and are lateral in the thinner, brownish rhizoidal branches.
Subseries 2. Metacranoideae:
Order # 13. Eubryales:
Both acrocarpic and pleurocarpic mosses are included in this large order but the acrocarpic forms predominate and only these are represented in India. The peristome is diplolepideous, but it differs from the Funariales in the peristome rings by being metacranoid.
Family Bryaceae:
Genera: 1. Orthodontium (2 spp. from Ceylon), 2. Mielichhoferia (9 spp.), 3. Pohlia (includes Webera) (21 spp.), 4. Mniobryum (3 spp.), 5. Epipterygium (2 spp.), 6. Brachymeniurn(29 spp.), 7. Anomobryum(13 spp.), 8. Leptobryum (1 sp.), 9. Plagiobryum (1 sp.), 10. Bryum (54 spp.—Fig. 491), 11. Rhodobryum (4 spp.).
Genus Bryum:
Bryum is a very large, genus with about 700 species distributed throughout the world. This genus has given the name to the order and the higher taxa. The species vary much from one another but are constant in leaf areolation and specially in the bryoid peristome.
More than 50 species of the genus are known in India. The commonest species in the plains is Bryum coronatum shown in Figure 491 which clearly shows the plant habit.
The sporophytes of Bryum coronatum are orange in colour and quite beautiful to look as the plants grow on soil or walls in large patches. The capsule has a swollen apophysis (Fig. 491C) and the peristome (Fig. 491D) is metacranoid with two rings of teeth of equal size. The outer ring is deeply coloured while the inner ring is hyaline and cilia are present.
The life history is as in other mosses.
Family Leptostomaceae:
Genus: 1. Leptostomum (1 sp. from Ceylon).
Family Mniaceae:
Genera: 1. Orthomnium (1 sp.), 2. Orthomniopsis (1 sp.), 3. Mnium (19 spp.).
Family Drepanophyllaceae:
Genus: 1. Mniomalia (1 sp. from Ceylon).
Family Rhizogoniaceae:
Genus: 1. Rhizogonium (1 sp.).
Family Hypnodendraceae:
Genera: 1. Hypnodendrori (1 sp. from Ceylon),
2. Mniodendron (1 sp. from Ceylon).
Family Aulacomniaceae:
Genus: Aulacomnium (2 spp.).
Family Meeseaceae:
Genus: 1. Meesea (2 spp.).
Family Bartramiaceae:
Genera: 1. Plagiopus (1 sp.),
2. Anacolia (3 spp.),
3. Bartramia (8 spp.),
4. Bartramidula (3 spp.),
5. Philonotis (18 spp.),
6. Breutelia (2 spp.),
7. Fleischerobryum (2 spp.).
Family Timmiaceae:
Genus: Timmia (3 spp.).
Most of the mosses of the pleurocarpic families that follow are long plants creeping along tree barks, rocks, etc., and are often seen hanging-down from trees in tropical, subtropical and temperate rain forests.
Order # 14. Isobryales:
Pleurocarpic (rarely acrocarpic), diplolepideous, metacranoid mosses but the inner peristome ring (endostome) usually not developed.
The pleurocarpous mosses are the most modern Bryophytes. They form a special feature of the tropical-subtropical rain forests. They form a thick-mat, creeping along (often covering metres) bark of tall trees and often hang down from the boughs (Fig. 493) giving a sombre aspect to the semidark interior-of the thick forests.
Family Erpodiaceae:
Genera: 1. Erpodium (1 sp.), 2. Aulacopilum (3 spp.), 3. Solmsiella (1 sp. from Ceylon).
Family Ptychomitriaceae:
Genera: 1. Ptychomitrium (3 spp.), Glyphomitrium (1 sp. from Ceylon).
Family Orthotrichaceae:
Genera: 1. Amphidium (2 spp.), 2. Zygodon (11 spp.), 3. Rhachithecium (1 sp.), 4. Orthotrichum (18 spp.), 5. Stroemia (1 sp.), 6. Ulota (2 spp.), 7. Drum- mondia (3 spp.), 8. Macromitrium (39 spp.), 9. Groutiella (1 sp.), 10. Schlotheimia (2 sp.), 11. Desmotheca (1 sp.), 12. Trigonodictyon (1 sp.).
Family Racopilaceae:
Genus: 1. Racopilum (3 spp.).
Family Climaciaceae:
Genus: 1. Climacium (1 sp.).
Family Hedwigiaceae:
Genera: 1. Hedwigia (1 sp.), 2. Hedwigidium (1 sp.), 3. Braunia (4 spp.), 4. Bryowijkia (1 sp.).
Family Cryphaeaceae:
Genera: 1. Schoenobryum (2 spp.), 2. Sphaero- theciella (1 sp.), 3. Pilotrichopsis (2 spp.), 4. Forsstroemia (4 spp.).
Family Leucondontaceae:
Genus: 1. Leucodort (3 spp.).
Family Ptychomoniaceae:
Genus: 1. Glyptothecium (1 sp. from Ceylon).
Family Trachypodaceae:
Genera: 1. Diaphanodon (2 spp.), 2. Trachypus (3 spp.), 3. Pseudospiridontopsis (1 sp.), 4. Trachypodopsis (2 spp.), 5. Duthiella (4 spp.).
Family Myuriaceae:
Genus: 1. Myurium (1 sp.).
Family Pterobryaceae:
Genera: 1. Trachyloma (2 spp.), 2. Penzigiella (2 spp.), 3. Osterwaldiella (1 sp.), 4. Endotrichella (2 spp.), 5. Garovaglia(6 spp.), 6.Jaegerina (1 sp.), 7. Ptero- bryopsis (21 spp.), 8. Symphysodon- tella (5 spp.), 9. Horikawaea. (1 sp.).
Family Meteoriaceae (Fig. 493):
Genera: 1. Papillaria (4 spp.), 2. Meteorium (4 spp.), 3. Meteariella (1 sp.), 4. Aerobryopsis (3 spp.), 5. Aerobryidium (1 sp.), 6. Barbella (13 spp.), 7. Floribundaria (10 spp.), 8. Pseudobarbella (4 spp.), 9. Chrysocladium{6 spp.), 10. Meteoriella (1 sp.), 11. Meteoriopsis (4 spp.), 12. Aero bryum (1 sp.).
Family Phyllogortiaceae:
Genus: 1. Orthorrhynchium (1 sp. from Ceylon).
Family Neckeraceae:
Genera: 1. Cryptoleptodon (3 spp.), 2. Calyptothecium (13 spp.), 3. Meeker a (10 spp.), 4. Neckeropsis (8 spp.), 5. Himantocladium (5 spp.), 6. Homaliodendron (13 spp.), 7. Homaliadelphus (1 sp.), 8. Handeliobryum (1 sp.), 9. Pirtna- tella (10 spp.), 10. Porothamnium (1 sp. from Ceylon), 11. Thamnobryum (7 spp.).
Family Lembophyllaceae:
Genera: 1. Isothecium (3 spp.), 2. Isotheciopsis (2 spp.), 3. Dixonia (1 sp.).
Order # 15. Hookeriales:
Soft, pleurocarpous, diplolepideous, metacranoid mosses from tropical, subtropical and temperate rain forests.
Family Hookeriaceae:
Genera: 1. Daltonia (15 spp.), 2. Distichophyllum (15 spp.), 3. Eriopus (4 spp.), 4. Hookeria (1 sp.), 5. Callicostela (2 spp.), 6. Hookeriopsis (3 spp.), 7. Lepidopilidium (1 sp.), 8. Actinodontium (2 spp.), 9. Pseudohypnella (1 sp from Ceylon), 10. Chaetomitrium (4 spp.), 11. Chaetomitriopsis (1 sp.), 12. Orontobryum (2 spp.).
Family Symphyodontaceae:
Genera: 1. Symphyodon (11 spp.).
Family Leucomiaceae:
Genus: 1. Leucomium (2 spp.).
Family Hypopterygiaceae:
Genera: 1. Lopidium (2 spp. from Ceylon), 2. Hypopterygium (5 spp.), 3. Cyatho- phorella (7 spp.), 4. Dendrocyalhophorum (1 sp.).
The Hyprobryales form a climax of moss evolution. The mats of pleurocarpic mosses specially abound in South-Eastern Asia (Indian and Pacific Ocean regions) pointing out the final cradle of their evolution.
Order # 16. Hypnobryales:
Pleucocarpous, diplolepideous mosses with metacranoid Bryoid type peristome.
Family Theliaceae:
Genus: 1. Myurella (2 spp.).
Family Fabroniaceae:
Genera: 1. Fabronia (12 spp.), 2. Anacamptodon (1 sp.), 3. Juratzkea (1 sp.), 4. Schwetschkea (2 spp.), 5. Schwetschkeopsis (2 spp.).
Family Leskeaceae:
Genera: 1. Regmatodon (4 spp.), 2. Lindbergia (3 spp.), 3. Leskea (3 spp.), 4. Leskeella (1 sp.), 5. Lescuraea (5 spp.), 6. Pseudoleskeopsis (1 sp.), 7. Okamuraea (1 sp.).
Family Thuidiaceae:
Genera: 1. Leptopierygynandrwn (3 spp.), 2. Haplohymenium (2 spp.), 3. Anomodon (4 spp.), 4. Herpetineuron (1 sp.), 5. Claopodium (3 spp.), 6. Haplocladium (5 spp.), 7. Thuidium (20 spp.), 8. Abietinella (2 spp.), 9. Actinothuidium (2 spp.), 10. Pelekium (2 spp.).
Family Amblystegiaceae:
Genera: 1. Cratoneuron (3 spp.), 2. Sciaromium (1 sp.), 3. Campylium (8 spp.), 4. Leptodictyum (1 sp.), 5. Hygroamblystegium (3 spp.), 6. Amblystegium (4 spp.), 7. Amblystegiella (1 sp.), 8. Drepanocladus (5 spp.), 9. Ilygro- hypnum (3 spp.), 10. Platyhypnidium (2 spp.), 11. Calliergon (3 spp.), 12. Ortholimnobium (1 sp.), 13. Calliergonella (1 sp.).
Family Brachytheciaceae:
Genera: 1. Homalothecium (7 spp.), 2. Brachythecium (37 spp.), 3. Bryhnia (3 spp.). 4. Rhynchostegium (11 spp.), 5. Rhynchostegiella (10 spp.), 6. Eurrhynchium (10 spp.).
Family Entodontaceae:
Genera: 1. Erythrodontium (1 sp.), 2. Pterigynandrum (2 spp.), 3. Trachyphyllum (4 spp.), 4. Campylodontium (2 spp.), 5. Orthothecium (1 sp.), 6. Rozea (3 spp.), 7. Entodon (19 spp.), 8. Levierella (1 sp.), 9. Nanothecium (1 sp.), 10. Pleurozium (1 sp.).
Family Plagiotheciaceae:
Genera: 1. Stereophyllum (13 spp.), 2. Plagiothecium (11 spp.).
Family Sematophyllaceae:
Genera: 1. Aptychella (5 spp.), 2. Clastobryum (5 spp.), 3. Clastobryopsis (2 spp.), 4. Chionostomum (1 sp.), 5. Hageniella (3 spp.), 6. Struckia (1 sp.), 7. Gammiella (1 sp.), 8. Pylaisiopsis (1 sp.), 9. Heterophyllium (2 spp.), 10. Wijkia (8 spp.), 11. Trismegeistia (1 sp.), 12. Meiothecium (4 spp.), 13. Pylaisiadelpha (1 sp.), 14. Brotherella (12 spp.), 15. Foreauella (1 sp.), 16. Rhaphidorrhynchum (2 spp.), 17. Warburgiella (5 spp.), 18. Semato- phyllum (13 spp.), 19. Acroporium (10 spp.), 20. Trichosteleum (8 spp.), 21. Acanthorrhynchium (1 sp.), 22. Taxithelium (7 spp.—Fig. 494), 23. Glossadelphus (7 spp.), 24. Macrohymenium (2 spp. from Ceylon), 25. Trolliella (1 sp.).
Family Hypnaceae:
Genera: 1. Bryosedgwickia (2 spp.), 2. Platygyrium (3 spp.), 3. Pylaisia (3 spp.), 4. Hypnurn (16 spp.), 5. Ectropothecium (19 spp.), 6. Trachythecium (1 sp. from Ceylon), 7. Isopterygium (17 spp.), 8. Isopterygiopsis (1 sp.), 9. Taxi- phyllum (3 spp.), 10. Vesicularia (13 spp.), 11. Dolichotheca (1 sp.), 12. Ctenidium (3 spp.), 13. Ptilium (1 sp.), 14. Neodolichomitra (1 sp.), 15. Leiodontium (2 sp.).
Family Rhytidiaceae:
Genera: 1. Rhytidium (1 sp.), 2. Rhytidiadelphus (1 sp.), 3. Gollania (3 spp.). Family Hylocomiaceae
Genera: 1. Hylocomitim (3 spp.), 2. Macrothamnium (4 spp.), 3. Leptohymenium (3 spp.), 4. Stenotheciopsis (1 sp.), 5. Macrothamniella (1 sp.).
Taxithelium Nepalemse:
Taxithelium is a tropical and subtropical genus belonging to the family Sematophyllaceae and occurring on tree barks in wet forests. It occurs extensively in India, Burma, Ceylon and the islands spreading to Australia.
It is also known in Africa and Central America. 9 species are known in India of which Taxithelium nepalense (Schwaegrichen) Brotherus is found extensively on tree trunks in tropical and subtropical regions. It is briefly described here as an example of hypnoid (i.e., belonging to the Hypnobryales) pleurocarpous moss.
The gametophytic plant grows during the rains on tree trunks. The stems are creeping, branching profusely and pinnately (Fig. 494A), forming a dense yellowish-green mat on the tree. The small leaves are deeply concave, broadly ovate and bluntly acute, uniformly and densely surrounding the branches (Fig. 494A) so that the branches do not appear flat.
The leaves do not show any vein and are one cell thick. The leaf cells (Fig. 494C) are papillose, elongate rhomboidal except at base on two sides where there are two patches called alars (Fig. 494D) each composed of a few quadrate cells.
The plants are monoecious but the antheridia and archegonia are borne on separate small side shoots. Such a plant is called autoicous. The spornphytes develop during the winter and occur in large numbers on each plant. There is a small foot, a long (up to 1 inch) seta and an oval, asymmetrically bent (almost horizontal) capsule.
The operculum (Fig. 494E) is short conical. When the operculum is shed, the peristome is exposed and two metacranoid rings of peristome teeth are seen. The peristome teeth curl out exposing the spores when dry (Fig. 494F).
The spores are soon discharged by the hygroscopic movement of these peristome teeth. Each spore germinates forming a filamentous protonema in which the new gametophytic plants develop in the usual way.
