In this article we will discuss about Lyginopteridaceae. After reading this article you will learn about: 1. Features of Lyginopteridaceae 2. Nomenclature of Lyginopteridaceae 3. External Features 4. Anatomy 5. Reproductive Organs 6. Some Other Genera.
Contents:
- Features of Lyginopteridaceae
- Nomenclature of Lyginopteridaceae
- External Features of Lyginopteridaceae
- Anatomy of Lyginopteridaceae
- Reproductive Organs of Lyginopteridaceae
- Some Other Genera of Lyginopteridaceae
Contents
1. Features of Lyginopteridaceae:
Taylor and Millay (1981) and Stewart (1983) listed following distinguishing features of family Lyginopteridaceae:
1. Members have been reported from both the Upper and the Lower Carboniferous periods of Palaeozoic era.
2. The plants were not very large and attained a maximum height of two metres.
3. Several plants were lianes or vine-like in their general habit.
4. They had axillary branching fronds with bifurcate rachis (Stidd & Hall, 1970).
5. The leaves were highly dissected and produced along the stem at widely separated intervals.
6. Fronds usually had a bifurcate rachis.
7. Petioles had a V-or W-shaped trace, formed as a result of the fusion of several smaller traces.
8. A large amount of secondary xylem was present in the stems.
9. Cauline vasculature was generally monostelic.
10. Due to the monostelic stems, it was always difficult for the stems to support the weight of their large fronds, and, therefore, the plants must have had a straggling growth habit.
11. The tracheal pitting was usually of the multiseriate, elliptical bordered type.
12. A “dictyoxylon cortex” was present in some members, i.e. anastomosing longitudinally oriented bands of sclerenchyma were present in the outer cortex.
13. Often one or two massive traces were seen into the leaves.
14. Ovules were radially symmetrical (radiospermic), small, attaining a length of 3-5 mm. They were borne in cupules.
15. The cupules were small and uniovulate in some while large and multi-ovulate in other members.
16. The integument of the ovules was simple and relatively thin.
17. The nucellus was fused with the integument of the ovule.
18. A structurally complex pollen chamber or pollen-receiving device was present Many members showed a mechanical method of sealing the pollen chamber.
19. Only the integument of the seed had a vascular supply and that too also by radially arranged strands
20. The apex of the nucellus elaborated into a lagenostome or salpinx.
21. Pollen-producing organs were small, laminar, or terminal in position and present in clusters on the branches of fronds.
22. Symmetry of the synangia or pollen-producing organs was radial to bilateral.
23. Pollen grains had a structurally homogenous exine. They were small and of trilete type.
A detailed discussion of Lyginopteris oldhamia is given in the forthcoming account.
2. Nomenclature of Lyginopteridaceae:
Lyginopteris oldhamia (=Calymmatotheca hoeninghausii) is one of the best known of Carboniferous fossil plants of Pteridospermales. It occurred in abundance in the coal ball horizon of Lancashire and Yorkshire. For several decades the roots, stems, leaves and seeds of this plant were independently known to the botanists but it was not realised that these all were the parts of a single plant.
Various parts were discovered and named as under:
Leaves: Sphenopteris hoeninghausii
Stems: Lyginopteris oldhamia
Petioles: Rachiopteris aspera
Roots: Kaloxylon hookeri
Seeds: Lagenostoma lomaxi
Jongmans (1929) reported the presence of capitate glands on the cupulate envelope enclosing the seeds. Similar type of glands were reported on the stem, leaves and also on rachis, and this became the basis of the fact that all these structures, described under different names, belonged to one and the same plant, i.e. Lyginopteris oldhamia.
3. External Features of Lyginopteridaceae:
The plants were probably climbers. The stem was long and aerial varying from 2 mm to 4 cm in diameter. Branching in the stem has been reported in a few cases, and Walton (1940) reported axillary branching, at least in one case. The weak stem had adventitious roots, probably prop roots (Fig. 4.3).
The leaves were many and spirally arranged. Characteristic spines, perhaps helpful in climbing, were present both on stem as well as leaves (Fig. 4.4). The leaves were bi-pinnate to tri-pinnate. The pinnae had pinnules or leaflets, and were present at right angles to the rachis. The rachis and the petiole were fixed or attached with capitate glands.
4. Anatomy of Lyginopteridaceae:
1. Stem:
The stem pieces are seen beautifully preserved in the European and American coal balls in the form of petrifactions and large compressions. A reconstruction of the transverse section of the stem shows the presence of a mesarch siphonostele with a well-developed centrally located pith.
There are separate regions of secondary’ wood and thick cortex. The latter is clearly differentiated into outer and inner cortex regions (Fig. 4.5).
The outer cortex contains radially broadened fibrous strands which form a net-like structure (Fig. 4.6). The inner cortex consists of parenchymatous cells. The pericycle, present just inner to the cortex, consists of many short cells and some sclerotic cells.
Five mesarch primary vascular bundles, separated by parenchymatous areas, constitute the primary structure of the stem. The primary phloem, consisting of small cells, is present towards the outer side in each vascular bundle. The cambium is also seen preserved in between phloem and xylem in some specimens. The xylem consists of tracheids.
The protoxylem tracheids have spiral thickenings. Centripetal tracheids of the metaxylem have multiseriate bordered pits while the centrifugal tracheids (Fig. 4.7) are scalariform. The pith is large and parenchymatous. Some thick-walled cells, called “sclerotic nests”, are scattered throughout the pith.
Several distinctly mesarch leaf traces are quite prominent. One leaf trace traverses through the petiole and branches into two parts to supply to the forking rachis. The secondary structure of the stem exhibits the presence of periderm just inner to the two cortical layers.
The primary phloem gets crushed and inner to this is present the cylinder of the secondary vascular tissue, which surrounds the primary xylem (Fig. 4.8). Several secondary medullary rays are present in this region. The leaf traces interrupt the cylinder of secondary vascular tissue.
Many large and small cells are alternately present in the secondary phloem. The cambium and then secondary xylem are present inner to the secondary phloem region. The secondary xylem consists of large tracheids with multiseriate bordered pits arranged on the radial walls.
2. Leaf:
Prior to the discovery of the connection between the stem and leaf, the leaf of Lyginopteris oldhamia was described as Sphenopteris hoeninghausii. As is clear from the impressions of Sphenopteris, the rachis was forked and had strong pinnae, which were again divided pinnately.
The leaves were as long as 50 cm. They were circinately rolled with their petiolar base somewhat swollen. Hairs and glands were present on the entire leaf. These hairs had round tips. Histologically, the leaf epidermis was cutinised on the adaxial surface. Mesophyll was differentiated into palisade and spongy parenchyma (Fig. 4.9). The stomata were present only on the abaxial surface.
3. Root:
In transverse section the cortex of the root is differentiated into outer and inner cortex (Fig. 4.10). The outer cortex is made of 2 to 3 layers at thin-walled cells while the inner cortex is 4-6 layered and contains many cells of mucilaginous nature. The outer cortex of-Lyginopteris root has been compared with the velamen of orchid root by Scott.
The stele may be tetrarch to starch with each arm of xylem having a small amount of protoxylem towards the outer side. Rootlets show diarch condition. The protoxylem consists of spiral tracheids. The phloem groups alternate with the xylem. In the prepared sections the endodermis and pericycle are clearly observed. The secondary wood develops in the larger roots. No distinct pith is present.
5. Reproductive Organs of Lyginopteridaceae:
Lyginopteris oldhamia was heterosporous, and its ovules and seeds were enclosed within well- protective cupules. Kidston (1905) discovered the impressions of Crossotheca in connection with the leaves of Sphenopteris hoeninghausii, and thus it was concluded that Crossotheca is the microsporangium of Lyginopteris because the leaves of Lyginopteris were described under the name Sphenopteris hoeninghausii.
The ovules and seeds of Lyginopteris were described under the name Lagenostoma lomaxi. Arnold (1947) stated that the microsporangiate structures of Lyginopteris belong to Telangium. Some other workers have also shown doubts on the validity of Crossotheca being the microsporangium of Lyginopteris.
(i) Microsporangium:
Crossotheca hoeninghausii has been described as the microsporangia-bearing member of Lyginopteris. Six to seven bilocular, pendant microsporangia were present on more or less peltate fertile pinnules called microsporophyll’s (Fig. 4.11).Each microsporangium was about 3 mm. in length and its dehiscence was longitudinal.
Microspores were present in the cavities of microsporangia, sometimes even in tetrads. Each microspore had a thick rough exine and attained a diameter of 50 to 70 μ. Chamberlain (1935) opined that these pollen grains must have shed in a fashion similar to that of Isoetes, Selaginella and other water ferns.
In the recent past, Stidd et al. (1985) described Schopfiangium having synangia similar to the pollen organs of Lyginopteris. Taylor & Taylor (1987) described a new pollen organ, Phacelotheca. Some other microsporangiate organs attributed to Lyginopteridaceae are Feroxotheca, Telangiopsis and Telangium.
(ii) Ovule and Seed:
Oliver and Scott (1903) described Lyginopteris oldhamia seeds as Lagenostoma lomaxii. Seed was a small, barrel-shaped structure measuring 5 to 6 mm. in length and about 4 mm in width. Each seed was surrounded by a cupule present at the end of the slender rachis.
Rachis was also covered by glands and hair-like leaves and stem. The seeds and the cupules are known only in a petrified condition. Single vascular bundle of the rachis divided into about 10 vascular strands which traversed laterally into the cupule. Several glands were present on the outer surface of the lobed cupule (Fig. 4.12).
The seed in Lagenostoma lomaxi was orthotropous. The nucellus was free at the tip (Fig. 4.13). In the later stages of development it was surrounded by a bell-shaped pollen chamber (Fig. 4.14) or lagenostome. The ovule was surrounded by an outer hard stony layer and an inner fleshy layer. It resembled with a Cycad seed to some extent.
(iii) Heterangium:
It is another important member of Palaeozoic Cycadofilicales belonging to family Lyginopteridaceae. It occurred in Upper and Lower Carboniferous beds and the best known species is Heterangium grievii. This stem genus is found in the form of compressions and petrifactions.
The largest stem of this genus was approximately 4 cm in diameter. It was rarely branched. In a transverse section the longitudinal ribs of sclerenchyma are present in the outer cortex (Fig. 4.15). Many stone cells are embedded in the parenchymatous inner cortex.
Numerous strands of tracheids separated by the parenchymatous bands are present in the vascular column. The stele is thus solid in Heterangium. One protoxylem is present in the leaf trace. The plant body of Heterangium ghevii resembles greatly with that of Calymmatotheca hoeninghausii.
(iv) Tetrastichia:
Tetrastichia was a monotypic genus of Lyginopteridaceae represented by only T. bupatides (Fig. 4.16). It has been reported from the Lower Carboniferous of Scotland along with another monotypic genus (Tristichia ovensii; Fig. 4.16B) of the family.
Its primary stem structures had close similarities with the ferns but its cortical bands of sclerenchyma and its secondary wood resembled very closely with the stems of Pteridospermales.
In transverse section the stem was less than 1 cm in diameter. It was branched in an opposite decussate manner. The protoxylem primary xylem was usually four-armed but also sometimes five-armed. It was made of a solid protostele. Reticulate or scalariform pitted tracheids were present in the protostele. Parenchyma cells were completely absent.
A mesarch protoxylem group was present in the middle region of each branch of the stem. From this protoxylem group originated several branch-trace protoxylems. The basal part of each of the lateral branch of the stem was swollen.
The shape of the vascular bundle which entered in this basal part was like a butterfly. The lateral branches of the stem were considered as “petioles” by some botanists. However, it could not be clearly established by the botanists that which type of the fronds were present on these petioles.
A narrow zone of secondary wood was present in some of the branches while in other branches the secondary thickenings were absent. The tracheids had reticulate thickenings. The rays were both uniseriate as well as multiseriate. “Sclerotic nests” or group of stone cells were present in the inner cortex. A network of plates of fibres was present in the outer cortex.
6. Some Other Genera of Lyginopteridaceae:
Stems:
Callistophyton, Rhetinangium, Schopfiastrum and Tristichia are some of the stem genera of Lyginopteridaceae. Stems of Callistophyton poroxyloides attained a diameter of over 2 cm and had well-marked axillary branching with fronds arranged in spiral sequence. It had a very compact secondary wood. The young leaves on the stem apex were circinately coiled in this genus.
Rhetinangium aberi stem has been reported from Lower Carboniferous of Scotland. It had a diameter of about 2 cm with a central stele of about 7 cm. The exarch protoxylem was made of many strands of tracheids along with a meshwork of parenchyma. The outer cortex had interconnected plates of fibers while the inner cortex had no sclerotic nests.
Schopfiastrum decussatum stems have been reported from US coal balls. Some parenchyma cells were present along with exarch rods of tracheids. The leaf traces developed in an opposite decussate manner. Several fibrous strands were present in the outer cortex.
The primary wood of Tristichia ovensii stems had triangular shape (Fig. 4.16 B) instead of quadrangular shown by Tetrastichia. The butterfly-like traces were received by its petioles. The radial walls of the secondary wood had multiseriate pits. Its cortex had sclerotic nests.
Fronds:
Sphenopteris (Fig. 4.1B, Fig. 4.9), Sphenopteridium (Fig. 4.1C), Alethopteris, Odontopteris, Diplopteridium (Fig. 4.1 A), Adiantites (Fig. 4.1D), Eremopteris, etc. are some of the frond-genera of Lyginopteridaceae.
Pollen-bearing Organs:
Crossotheca (Fig. 4.11) and Telangium are the pollen-bearing organs of Lyginopteridaceae.
Seeds:
Some of the seeds belonging to Lyginopteridaceae and reported from Lower Carboniferous period of Palaeozoic era include Calathospermum, Camptosperma, Dolychosperma, Eosperma, Genomosperma, Geminitheca, Lyrasperma, Salpingostoma, Sphaerostoma and Stamnostoma.
(i) Medullosaceae:
General Characteristics:
1. Members of this fossil family of Palaeozoic Pteridospermales were present between Upper Carboniferous and Permian periods.
2. Plants were larger and more massive than Lyginopteridaceae members. They had trunk-like stems and massive pollen-bearing organs and seeds.
3. All members were polystelic, and as much as forty steles were present in the stems of some of the species. Basmger et al. (1974), however, put forward convincing evidence that stem of Medullosaceae were monostelic. According to them, the so-called separate “steles” have evolved from the dissection of a single protostele.
4. Each of the many steles of the stem had the ability to undergo secondary thickening, and surprisingly the intervening tissues were without any disruption.
5. Meristematic parenchyma cells were present between the xylem tracheids of both primary and secondary woods.
6. It has been suggested by Delevoryas (1955) that in these plants the primary wood at any particular level continued to increase with age.
Medullosa and Sutcliffia are the examples of the stem-genera, while Myeloxylon is the petiole- genus of family Medullosaceae. The seed-genera are exemplified by Codonospermum, Stephanospermum, Polylophospermum and Polypterospermum while the examples of pollen- bearing organs include Aulacotheca, Codonotheca, Potoniea and Whittleseya.
Questora, a genus with only one vascular segment in its stem, has been included under Medullosaceae by Mapes and Rothwell (1980).
Only some details of Medullosa are mentioned below.
Medullosa:
Medullosa, a stem-genus of family Medullosaceae, is known by over 40 species or varieties. M.primaeva has been reported from an American coal-ball. It had a stem of about 2 cm in diameter and possessed as many as 23 steles showing polystelic condition. Out of so many steles, about half a dozen were larger than the others.
The central region of the stem had thicker secondary wood than the peripheral region. The leaf traces, made of stelar branches, continued to anastomose towards the leaf base. In M.anglica, the secondary xylem was present only in some of the leaf traces, and therefore this species was more advanced than M.primaeva.
Only 3 or 4 main steles were present in M.anglica. A periderm surrounded these vascular bundles. Along with these main bundles, some accessory strands of secondary origin were also present. Comparatively smaller number of steles were present in species such as Medullosa centrofilis, M.olseniae and M.noei.
The secondary xylem was absent in the leaf traces of these species, and such species were the examples of the extreme end of the evolution within this genus.
In some other species (e.g. M.stellata and M.leuckartii) there was a lateral fusion of the outer rings of steles, and such species represented the examples of another line of evolution, which continued even into the Permian period of Palaeozoic era. There was a complete lateral fusion of steles in M.stellata, and this resulted in the form of a ring of primary wood along with the secondary wood, both outside as well as inside.
As many as 43 central steles have been reported to be present in one such trunk. Rings of centrifugal secondary xylem and secondary phloem were present in M.solmsii var. lignosa. The complex stelar arrangement of Permian Medullosaceae has been compared with the present day Cycads by some botanists.
Wesley (1963), however, did not agree with the view that present day cycads have been originated from the Medullosaceae.
(ii) Calamopityaceae:
General Characteristics:
1. This fossil family of Palaeozoic Pteridospermales is represented by seven stem-genera (Bilignea, Calamopitys, Diichnia, Endoxylon, Eristophyton, Sphenoxylon and Stenomyelon) and a petiole-genus (Kalymma).
2. Manoxylic wood (i.e. scanty, loose with medullary rays) was present in Calamopitys, Diichnia and Stenomyelon while pycnoxylic wood (i.e. compact with narrow medullary rays) was present in Bilignea, Endoxylon, Eristophyton and Sphenoxylon. Lacey (1953) and Sporne (1965), however, proposed to transfer pycnoxylic genera to Cordaitales.
3. The stems had a varied anatomy from solid protostele to a system of circum-medullary strands.
4. A well-developed sporangium-system of fibres was present in the cortex.
5. Probably, the leaves were large and frond-like. No reproductive organs or even leaves have been found attached with stem and petiole remains.
(iii) Glossopteridaceae:
General Characteristics:
1. These plants occurred widely during Upper Carboniferous and Lower Permian times (i.e. as far back as 280 million years ago) in Indian peninsula, Antarctica, South America, South Africa and Australia. Since all these regions together represent a hypothetic continent, Gondwanaland, separated from the other continents by Tethys Sea, the flora which occurred there is also called Gondwanaland flora.
2. Since the most abundantly occurring leaf-genus of Gondwanaland flora is Glossopteris (Fig. 4.2B), this flora is also called Glossopteris flora. Over 50 species of Glossopteris have been reported till now.
3. The leaves were generally tongue-shaped.
4. The length of the leaves varied from a few centimeters to several decimeters.
5. The leaves had a reticulate venation (Fig. 4.2B) and are believed to belong to some ancient ferns by some botanists.
6. A midrib was present in the leaves of most genera (e.g. Glossopteris). In Gangamopteris, however, the midrib was absent. In Palaeovittaria, the midrib was present only in the proximal half of the leaf.
7. The stems were probably delicate and the leaves were borne in whorls.
8. Scaly leaves with retirulate venation were also present in some members.
9. The pittings of the tracheids of stem resembled more with conifers than cycads.
10. Several microsporangia and seeds have also been observed to be attached with Glossopteris- like leaves.
11. In Lanceolatus, of which two species have been reported by Sen (1955) from India, the seed- bearing valve was fused completely with the leaf.
12. In Lidgettonia africana, the reproductive organs were stalked peltate bodies attaining a diameter of about 5 mm. In this case the fertile leaves were much smaller than the sterile leaves. Pant (1958) and Pant and Nautiyal (1960) also reported many seeds and sporangia of Glossopteridaceae from India, Australia and Tanganyika.
13. According to Plumstead (1958) members of Glossopteridaceae might have been the ancestors of flowering plants. But Spome (1965) stated that this statement “seems to be singularly premature and ill-advised”.
Pant (1977) and Gould and Delevoryas (1977) have reconstructed the Glossopteris plant (Fig. 5.1). It was a large tree with a high trunk of about 6 metre. A Vertebraria-type of root system supported the plant. Its trunk had Araucarioxylon-type of gymnospermous wood.
The leaves were arranged either spirally or in whorls. It is not yet known whether Glossopteris trees were monoecious or dioecious because all fructifications have been reported in detached state. Surange and Chandra (1976), however, opined that Glossopteris plants were dioecious in nature.
According to Pant (1977), Vertebraria was a stem system but Gould (1977) opined that it was a root system.
Glossopteris leaves (Fig. 5.1 B) were tongue-shaped with a prominent mid rib. The venation was reticulate. The leaves were generally sessile and rarely petiolate.
According the Pant (1958) Glossopteris leaves were typically dorsiventral and hypostomatic, and the stomata were haplocheilic and sunken. Mesophyll was divided into palisade and spongy parenchyma.
Several male, female and bisexual fructifications have been reported. All these are leaf borne and hence occupy unique position among gymnosperms. The leaf or bract associated with fructifications have together been termed as “fertiliger” by Pant (1987).
Eretmonia, Glossotheca and Nesowalesia are the names of male fructifications of Glossopteridaceae. Whorls of microsporangia were present on two branches on the upper half of the lamina of Eretmonia. The pollination was probably anemophilous according to Pant (1987).
Many female fructifications have been reported, and nearly all of them have been studied as compression-impressions only. Denkania indica, Parthaarid Mooia are the female fructifications described by different workers.
Pant and Nautiyal (1987) reported the rare occurrence of dicotyledonous seedlings in Glossopteris.
Glossopteris is a member of gymnosperms because of the following similarities given by Pant (1977, 1987):
1. It possesses gymnospermous wood as in Vertebraria.
2. It possesses gymnospermous type of axis on which leaves have been found attached.
3. Similarity in stomata, cuticle and xylem in the leaves.
4. Presence of exposed seeds found attached to leaves.
5. Similarity in pollination.
6. Seeds had bisaccate pollen.
(iv) Peltaspermaceae:
1. Plants of this fossil family occurred on the earth in the Triassic period of Mesozoic era, and were first reported by Thomas (1933) from Natal in South Africa.
2. These fossils have now been widely reported from Sweden, Greenland, Argentina, Australia and China.
3. Frond-genus Lepidopteris (Fig. 4.2D), seed-bearing organs Peltaspermum (Fig. 4.2E) and pollen-bearing organs Antevsia are some of the reported members of the family. Much is not known about the general growth habit and the stems bearing these reported organs of the family.
4. Leaves (Lepidopteris) were lanceolate, bi-pinnate or tri-pinnate and had un-branched rachis. They attained a length or about 30 cm.
5. Antevsia, the pollen-bearing organs, were bi-pinnate bodies with alternate primary branching. The ultimate branches possessed 10-12 pollen sacs. Each pollen sac was about 2mm long. The wall of pollen sac possessed stomata. The pollen grains were un-winged and each had a longitudinal furrow.
6. The seed-bearing organs (Peltaspermum thomasii) were present on the leaves, and had several stalked, peltate heads of a diameter of about 5 mm. Each head contained two seeds. In P rotula, however, as many as 10-12 seeds were present in each head (Fig. 4.2F).
Peltaspermaceae represents probably a “link between more primitive ferns and angiosperms” according to Bierhorst (1971).
(v) Corystospermaceae:
General Characteristics:
1. Thomas (1933) created this family on the basis of some fossils collected from Triassic period of Mesozoic era from the molten beds of the upper part of Karro formation in Natal (South Africa). Members have later been reported from Australia, Argentina, India and some other places.
2. Reported genera of this family include fronds (Xylopteris, Fig. 4.2I; Dicroidium), pollen- bearing organs (Pteruchus, Fig. 4.2K; Pterorachis), and seed-bearing organs (Umkomasia, Fig. 4.2J; Pilophorosperma, Spermatocodon).
3. In frond-genera (e.g. Xylopteris, Fig. 4.2I) the rachis divided into two equal parts near the base. Open venation is present in the pinnae. Dicroidium feistmantelii was bipinnate and quite large reaching up to about 1 metre in length
4. The pollen-bearing organs (Pteruchus, Fig. 4.2K) had a central axis having short lateral branches. At the tip of each branch was present a peltate head bearing up to 30 or more sporangia. Each sporangium was about 3 mm long.
5. In seed-bearing organs, the seeds were borne singly in helmet-shaped cupules as in Umkomasia (Fig. 4.2J). Small bracts and bracteoles were also present, and because of these the entire structure has been termed as inflorescence by Thomas (1933). The cupules splitted into two halves in Umkomasia.
6. A long and bent bifid micropyle was present in seeds
(vi) Caytoniaceae:
General Characteristics:
1. Fossils of this family have been reported from the rocks belonging to Upper Triassic, Jurassic and Lower Cretaceous periods of Mesozoic era. Plants of this group were discovered first by Thomas in 1925 from Middle Jurassic rocks of Cayton Bay in Yorkshire (England).
2. Leaves are present in the form of Sagenopteris, seed-bearing organs in the form of Caytonia and pollen-bearing organs as Caytonanthus.
3. Sagenopleris (Fig. 4.2L) had a slender petiole terminating into four leaflets. The leaflets were arranged in two pairs. A prominent mid-rib was also present. The veins were forking with anastomosing lateral connections.
4. The seeds (Caytonia; Fig. 4 .2M) were found attached on a rachis in the form of small, fruitlike structures resembling present-day currants. Each seed was enclosed in a cupule. Harris (1951) called these structures as “fruits”. In each “fruit” these were about 8 seeds in C. sewardii, 15 in C. ncirthorstii, and about 30 in C. thomasii
5. Pollen-bearing organs (Caytonanthus) had a dorsivental rachis possessing somewhat opposite pinnae. A synangium was present on each terminal branchlet of the irregularly branched pinnae (Fig. 4.2 O). Each synangium possessed four loculi (Fig. 4.2N).
6. Thomas (1925) opined that Caytoniaceae had definite relation with the origin of plants but later workers criticized and rejected this opinion.
Angiospermic Characters of Caytoniaceae:
1. The curved cupules had stalked, orthotropous ovules. Since these ovules closed after pollination, they resembled closely with that of angiosperms.
2. Reticulate venation of leaves.
3. Development of abscission layer.
4. Presence of bud scales.
5. Presence of microsporophyll’s possessing tetralocular synangia.
Gymnospermous Characters of Caytoniaceae:
1. Male fructifications were radially symmetrical.
2. Filament and connective tissues absent in the male fructifications.
3. Presence of winged pollen grains.
4. Leaves had no blind vein ends.
5. Megasporophylls were pinnate in nature.
6. Pollen were discovered inside the micropyle as well as at the tip of the nucellus of the ovules.