In this article we will discuss about the classification of Rosales. According to Engler, Rosales consists of seven families:- 1. Crassulaceae 2. Cephalotaceae 3. Saxifragaceae 4. Hamamelidaceae 5. Platanaceae 6. Rosaceae 7. Leguminosae.
Contents
Family # 1. Crassulaceae:
Succulent perennial herbs or shrubs. Leaves simple or compound, opposite, alternate or whorled, exstipulate, more or less thick and fleshy. Inflorescence a dichasial or monochasial cyme or panicle, rarely raceme or spike. Flowers bisexual, rarely unisexual, actinomorphic, usually hypogynous, 4-5-merous. Sepals 4-5, usually free, valvate, persistent. Petals as many as sepals, free or united in a tube, imbricate.
Stamens as many as petals or twice as many as petals in 2 whorls; filaments free, inserted on a swollen or cup-like disc; anther bilocular, introrse, dihescing longitudinally.
Ovary superior or rarely semi-inferior, with free or almost free carpels, usually as many as petals or more, rarely carpels 3, styles free with small stigmas; each carpel is provided with a nectar secreting scale; ovules many in each carpel on marginal placentas. Fruit a cluster of follicles. Seeds small, with straight embryo and scanty fleshy endosperm or endosperm absent.
The floral formula is KnCn An+n Gn where “n” is usually valued as 4-5 but in some cases several and rarely upto 30. The genus Rhodiola has unisexual flowers in dioecious plants. The leaves are provided with hydathodes and often impregnated with silica. In some cases the leaves are cylindrical or subulate.
Adventitious buds develop on leaf- margin by which vegetative reproduction takes place. The leaves have sunken stomata. Water storage tissues are present both in leaves and stem. Xylem cylinder is usually continuous. The secondary vessels are with simple pits and reticulate thickenings. Perforations are simple.
The family consists of about 1,300 species in 29 genera distributed in comparatively drier parts of the world but absent in Australia. In India several species of Sedum occur in the Himalayas and Kalanchoe pinnata (Lam.) Pers. and K. laciniata Adams are common in the plains. Plants of this family have no economic importance but a few are cultivated as garden ornamentals.
The family is very much allied to Saxifragaceae having 2 whorls of stamens, bisexual flowers, fleshy endosperm, etc. It is also related to Rosaceae to some extent. It is, therefore, included in Rosales or Saxifragales by most authors subsequent to Engler.
Family # 2. Cephalotaceae:
Perrnnial herbs with short under-ground rhizomes. Leaves radical, crowded in a rosette round the erect flowering scape; these are of 2 kinds, the lower leaves bearing pitchers like those of Nepenthes, the upper leaves simple, with normal elliptic blades, entire, nerveless. The inflorescence is a thyrsus—a raceme of cymules, bracteate at the base.
Flowers small hermaphrodite regular and perigynous. Calyx gamosepalous, campanulate, coloured, persistent; lobes 6, valvate, hooded. Corolla absent. Stamens 12, inserted on the margin of a setose glandular disc at the top of the calyx; filaments free, 6 longer than the others; anthers 2-locular, dehiscing longitudinally; connective swollen at the top and glandular.
Carpels 6, free, or more or less united, hairy, in a single whorl, each 1-locular and with 1, rarely 2 basal erect ovules. Ovary superior. Style short, recurved, subulate with simple stigma. Fruit a cluster of follicles surrounded by the accrescent calyx, shortly stipitate and densely hairy, 1-seeded. Seeds with fleshy endosperm and small straight embryo’.
The small family with a single species Cephalotus follicularis Lab. is restricted to S. W. Australia. The plants are carnivorous and the pitchers for catching insects are borne by the lower leaves of the rosette.
The petiole is dilated at top to form the pitcher like that found in Nepenthes. The pitchers rest on the damp ground and have winged ridges on the outside which help crawling insects to easily climb up to the mouth of the pitcher.
The pitcher is provided with a lid which closes when an insect is trapped inside. The pitchers are most suitable traps for wingless creatures creeping on the ground although flying insects are also captured in the pitcher. The lid has brilliant purple veins and pretty white patches and serve to attract the insects.
Inside the pitcher there is a circular ridge projecting inwards; then a portion of the wall densely covered with little sharp papillae, pointed downwards, and on the involute rim round the mouth of the pitcher there is a ring of hooked de-curved spines.
Such contrivances efficiently stop the unfortunate insect from coming out of the pitcher as it enters the same in search of nectar or accidentally. An acid secretion from the special glandular cells on the wall of the pitcher kills and gradually digests the dead creature. The affinity of the family is disputed; probably it is distantly related to Saxifragaceae.
Family # 3. Saxifragaceae:
Perennial or rarely annual herbs or shrubs, rarely trees. Leaves simple, alternate, rarely opposite, with or without stipules. Inflorescence racemose or cymose or of a complex type, flowers usually bisexual, regular, usually 5, numerous with cyclic arrangement; receptacle flat or cupular or tubular so that the flower is hypo-, peri-, or even epigynous; bracts often present.
Sepals 4-5, free or united at base and adnate to the receptacular cup forming a hypanthodium, imbricate or valvate. Petals as many as sepals, usually free, rarely united or absent, imbricate or valvate, inserted on the hypanthodium. Stamens usually double the number of petals and in 2 whorls, often as many as petals and in 1 whorl, free, inserted on the hypanthodium; anthers bithecal, with longitudinal dehiscence.
Ovary superior, semi-inferior or inferior; carpels 2-5, united below with free styles; cells as many as carpels with rows of anatropous ovules on axile placentation; ovary is often 1-celled or rarely carpels may be free; often the ovary is obliquely placed. Fruit a capsule or berry. Endosperm, fleshy, copious, surrounding a small embryo.
Flowers are insect-pollinated and are protrandrous or protogynous. The typical floral formula is K5 C5 A5+5 G(2).
Plants are usually herbs but shrubs and trees are also found, e.g. Hydrangea, Philadelphus, Escallonia, etc. Leaves are simple but in Bauer a 3-foliolate leaves are produced. Saxifraga, Astilbe, Parnassia, etc. have alternate leaves but Hydrangea, Deutzia etc. have opposite leaves. Inflorescence may be a raceme or spike, or a cyme, often paniculate. Chrysosplenium has a biparous cyme.
In Hydrangea it is an umbel-like spreading panicle of biparous and uniparous cymes. Zygomorphic flowers are found in some Saxifraga, and in Hydrangea the peripheral barren flowers are so. Unisexual flowers are found in some Ribes and Astilbe. Ribes alpinum L. is dioecious. Petals are absent in Chrysosplenium.
In Parnassia the inner whorl of stamens are sterile and modified into palmately lobed staminodes. Ovary may be superior, semi-inferior or inferior even in the same genus, e.g. Saxifraga. In Ribes, Bauera, etc. ovary is 1-locular, while 2-5-locular ovary are found in others.
The family consisting of about 1,200 species in 80 genera occur usually in the cooler parts of the globe; many are alpine and some occur in the artic region. Some are xerophytic and a few are even hygrophilous. In India the family is represented in the Himalayas by Hydrangea, Astilbe, Ribes, Parnassia, Deutzia, Saxifraga etc. Vahlia viscosa Roxb. and V. oldenlandioides Roxb. occur in the plains of eastern India.
Currants are different species of Ribes and R. grossularia L. is the Goose-berry. Dichroa febrifuga Hk.f. of E. Himalaya is reputed to have medicinal properties, Philadelphus coronarius L. with fragrant flowers and Hydrangea hortensis are cultivated as ornamental plants. Otherwise the family is not of much economic value.
The family is subdivided into several sub-families by Engler as given below:
I. Saxifragoideae:
Herbs with alternate, exstipulate leaves; flowers hypo-, peri-, or epigynous; sepals and petals 5 or 4; carpels usually 2, rarely more. Saxifraga, Astilbe, Parnassia, etc.
II. Francoideae:
Herbs with radical leaves; flowers tetramerous with 4-celled ovary. Francoa, Tellima.
III. Hydrangeoideae:
Shrubs or trees with opposite leaves; flowers usually epigynous; sepals 5, petals 5, ovary 3-5-celled. Hydrangaea, Deutzia, Philadelphus.
IV. Pterostemonoideae:
Shrubs, leaves stipulate; flowers epigynous, 5-merous; stamens 10, ovary of 5 carpels, 5-celled. Pterostemon.
V. Escallonioideae:
Shrubs or trees, leaves gland-dotted, exstipulate; flowers hypo-, peri- or epigynous; stamens as many as petals, carpels 2-5. Escallonia, Itea.
VI. Ribesioideae:
Shrubs, leaves exstipulate; flowers epigynous; ovary 1-celled; placentation parietal; fruit berry. Ribes.
VII. Baueroideae:
Shrubs, leaves 3-foliolately compound; flowers perigynous; ovary 1-celled with parietal placentation. Bauera.
Saxifragaceae is related to Crassulaceae having usually 5-merous flowers and stamens in 2 whorls. In Crassulaceae endosperm when present is fleshy as in Saxifragaceie. This family is also allied to Rosaceae to some extent.
Variations in the floral structure prompted many authors to split the family into several smaller families, e.g. Saxifragaceae (sensu stricto), Eremosynaceae, Vahliaceae, Francoaceae, Parnasiaceae, Petrostemonaceae, Philadelphaceae Hydrangeaceae, Grossulariaceae and Escalloniaceae.
According to Takhtajan these are more or less closely related and are all included in his Saxifragales along with some other families while Hutchinson puts first five families in Saxifragales and the other five families in Cunoniales. The two orders are not close to each other and Cunoniales is one of the primitive orders among the Lignosae while Saxifragales is in the Herbaceae and is considered fairly advanced.
Cronquist does not recognize so many small families but has separated only Hydrangeaceae and Grossulariaceae from Saxifragaceae. His Hydrangiaceae includes Petrostemonaceae and Philadelphaceae and Grossulariaceae includes Escalloniaceae.
Family # 4. Hamamelidaceae:
Trees and shrubs; bark containing a bitter and acrid juice. Leaves simple, alternate, stipulate; stipules caducous. Inflorescence is a capitulum or spike. Flowers bisexual or polygamous or unisexual and monoecious or dioecious, actinomorphic or very rarely zygomorphic, perigynous or epigynous, rarely hypogynous, usually tetramerous.
Calyx of 4, rarely 5 sepals united at base in the form of a cup or tube; segments imbricate. Petals 4 or rarely 5, inserted on the calyx tube, free, usually valvate, linear and cercinate in bud, often petals absent. Stamens usually 8-10 in 2 whorls, the inner whorl often sterile, often stamens in one whorl and few or many; anthers bithecal, dehiscing longitudinally or by valves; connective prolonged to a horny tip.
Ovary inferior, semi- inferior or superior, of 2 united carpels, 2-locular, styles free, usually recurved, persistent ; ovules many or few in each cell, pendulous from axile placentation, anatropous. Fruit a loculicidal or septicidal capsule, 2-beaked, bursting, at top, with leathery’ or woody exocarp and bony endocarp, usually with 1 seed in each chamber. Seed with or without endosperm and a large straight embryo.
Plants are evergreen but deciduous trees are also found, e.g. Hamamelis, Parrottia, etc. Leaves are pinnately veined and with glandular toothed margin while Liquidambar has palmately lobed leaves.
Liquidambar and Altingia have unisexual flowers; the males are in dense spikes, the female flowers crowded in globose heads with rudimentary calyx and few staminodes. Here the flowers are epigynous and the floral heads often subtended by coloured bracts. Distylium, Hamamelis, etc. have hypogynous flowers.
This is a small family with about 100 species in 27 genera of which 14 are monotypic. Most of them are confined to Western and Central Asia while a few are found in distant countries so that the family has a wide range of distribution from N. America to Australia.
It is represented in Africa and Madagascar and also in S. Europe. In the Himalayas Exbucklandia populnea R.W.Br., Corylops himalayana Griff., Altingia excelsa Noronha and some species of Liquidamber are good timber trees.
Liquidambar orientalis Mill, of W. Asia and L. styraciflua Linn, of N. America are the source of storax—a fragrant balsam. Exbucklandia populnea R.W.Br., Altingia excelsa Griff, and some species of Liquidamber are good timber trees.
The family appears to be closely allied to Myrothaninaceae and Platqnaceae. The 3 families are placed under Hamamelidales by Hutchinson along with five other families. According to him Rosales and Hamamelidales are not very close but both are derived from same ancestral stock.
Tippo states that from Hamamelidales orders like Casuarinales, Fagales, Urticales and Juglandales originated: This view is supported by Cronquist according to whom Trochodendrales, Eucommiales, Leitneriales and Myricales are also derived from Hammelidales.
Takhtajan also considers these orders close to each other and includes them in his subclass Hamamelididae along with Cercidiphyllales, Eupteleales, Didym elales, Barbeyales and Balanophorales.
The family is subdivided into 5 subfamilies as follows:
I. Disanthoideae:
Capitula of 2 different flowers; petals long, narrow; ovules up to 6 in each locule.
II. Hamamelidoideae:
Flowers bisexual, rarely unisexual, usually superior, petals long, narrow; ovules 1-2 in each locule.
III. Rhodoleioideae:
Capitula axillary, pendulous, surrounded by many imbricating bracts; woody capsule; endosperm copious.
IV. Exbucklandioideae:
Capitula polygamo-monoecious; leaves palmiveined, simple or 3-lobed.
V. Liquidambaroideae:
Flowers unisexual and monoecious, males without perianth, females with rudimentary perianth; leaves glandular serrate or palmately lobed; ovules many in each cell.
The subfamilies Rhodoleioideae and Liquidambaroideae are raised to the rank of families by some workers as Rhodoleiaceae and Altingiaceae. Fossils of Liquidambar and Parrotia were discovered in upper oligocene belt; Hamamelis was found in chalk- belt.
Family # 5. Platanaceae:
Large deciduous trees, bark exfoliating in large flakes leaving a smooth trunk. Leaves simple, alternate, usually palmately lobed and palmately nerved, dentate, stipulate; stipules membranous, caducous, usually large and conspicuous and sheathing; the petiole is dilated at base enclosing the axlliary bud.
Inflorescence of globose heads or capitula several in a pendulous peduncle; each head wholly male or wholly female; bracts linear or scale-like. Perianth absent. Stamens in male flowers many, each subtended by a minute scale; anthers subsessile, oblong or obpyramidal with expanded peltate connective, bilocular, dehiscing longitudinally; pistillode often present in ♂ flowers.
Ovary of a single carpel, 1 -locular with 1 or rarely 2 pendulous orthotropous ovules; stigma unilateral on an elongated linear style; staminodes often present in female flowers. Fruit a globose head of ± turbinate achenes or caryopsis with persistent styles, surrounded by tufts of long bristle-like pappus or hairs, each with a single linear seed. Embryo straight and narrow; endosperm scanty.
The family consisting of a single genus with 10 species has a scattered distribution, from Tropical America, S. E. Mediterrnean region and W. Asia and in Indo- China. W. Asiatic species Platanus orientalis Linri was introduced into India and was naturalized in Kashmir.
This is a large tree often with a girth of 12 mtr. or more and lives to a great age. The timber obtained is used for manufacture of furniture although it is of a rather inferior quality. It is mainly planted as a shade tree or avenue tree.
The family is related to Hamamelidaceae through the genus Altingia or to Altingiaceae when considered as a distinct family having unisexual capitula, anthers with prominent connective and ovary with persistent style. It is placed in the suborder Rosineae of Rosales by Engler while Hamamelidaceae is placed in the suborder Saxifragineae.
Most of the subsequent workers including Hutchinson, Takhtajan and Cronquist recognise the close affinity of Platanaceae with Hamamelidaceae and place the family in Hamamelidales, an order distinct from Saxifragales or Rosales.
Family # 6. Rosaceae:
This is a large family of herbs, shrubs and trees; herbs may be erect or prostrate with runners; shrubs erect or scandent or climbing. Leaves simple or pinnately, rarely palmately compound, usually stipulate, mostly alternate. Inflorescence is a raceme or panicle, sometimes cymes, rarely solitary.
Flowers actinomorphic, very rarely zygomorphic, usually bisexual, perigynous or ‘hypogynous, rarely epigynous. Receptacle large, flat or cupular. Sepals usually 5, connate and adnate to the receptacle, lobes imbricate or valvate. Petals 5 or more, free, inserted on the receptacular cup or hypanthium.
Stamens many or sometimes 5 or 10; anthers 2-locular, dehiscing laterally; filaments in different whorls differing in length. A cushion-shaped or ring-like nectar secreting disc is present between the stamens and carpels.
Carpel 1 or more, often many, free or syncarpous in the cup-shaped receptacle forming a superior or semi- inferior or sometimes inferior ovary; ovule 1-few in each carpel, pendulous or ascending; styles free in case of syncarpous ovary. Fruit a drupe or berry or pseudocarp or an aggregate of achenes or berries. Seed with a, small straight embryo and usually no endosperm.
The family with about 2,000 species in about 100 genera is distributed mainly in the N. temperate regions of the globe. It is well represented in India, especially in the Himalayas where a large number of Rubus species occur, besides species of (tosa, Coto- neaster, Pyrus, Prunus, Eriobotrya, Spiraea, Potentilla, etc.
Much diversity of forms, vegetative as well as floral, is noticed in this large family. There are trailing or creeping herbs like Fragaria, erect, herbs like Agrimonia, some Potentilla, erect Shrubs like Spiraea, some Rosa, scrambling like most Rubus and a few Rosa species, trees like Pyrus, Prunus, Eriobotrya, etc.
Leaves simple in Prunus, Quillaja, Eriobotrya, etc., pinnate as in Rosa, Pyrus, etc., digitate as in Fragaria and Rubus. Stipules usually present but absent in Spiraea-, caducus in Prunus and adnate in many genera. Flowers bisexual but polygamous in Poterium.
Regular flower in all genera but in the subfamily Chrysobalanoideae the flowers are zygomorphic. In Potentilla a whorl of epicalyx is present. The receptacle shows much variation in shape and may be more or less flat or concave of varying depth, and in Chrysobalanoideae forms a tube; a convex receptacle is found in Fragaria.
The character of the receptacle forms the basis of the subdivisions of the family. Stamens are usually many but in Alchemilla arvensis Scop there is only one stamen while in Couepia (Chrysobalanoideae) there are as many as 300; stamens are free but rarely monadelphous, e.g. Acioa.
Carpels many or few, rarely 1 as in Prunus and Acioa, usually free, but connate and adnate to the receptacular cup as in Pomoideae and Neuradoideae; in Pqmoideae the united carpels form an inferior ovary; in other cases the gynoecium is superior or semi-inferior.
Style is usually terminal but lateral in Fragaria and basal in Acioa and Alchemilla. The style is often persistent, becoming feather-like in Dryas. The nature of fruit also varies1 from a cluster of achenes or follicles or berries to a pome or a drupe.
The typical floral formula would be:
K(5) C5 A∞ G1–∞ or G(∞)
The family is important not only for the ornamental plants cultivated in the gardens but also for many species yielding edible fruits. Roses of the gardens are different species of Rosa with hundreds of horticultural varieties.
The famous essence Oto is obtained from R. damascena Mill, much cultivated in Bulgaria, in Iran and in Gazipur in India. The cherries are different species of Prunus, much cultivated in Japan for showy flowers. Many species of Spiraea, some Pocntillla, a few Rubus are also cultivated for the same purpose.
Famous fruit trees are: the apple—Malus sylvestris Mill., the pear—Pyrus commumis Linn., the plum—Prunus domestica Linn., the peach—Prunus persica (L.) Batsch., the apricot—Prunus armeniaca Linn., the almond—Prunus dulcis L. the strawberry—Fragaria vesca Linn., the raspberry—Rubus caesius Linn., the loquat—Eriobotrya japonica Lindl., the quince—Cydonia oblonga Mill. etc.
A few have medicinal value. The petals of Rosa centifolia L. boiled in sugary solution is called Gulcand and is used as a rejuvenating tonic. Quillaja saponaria L. is the soap-bark tree, the bark of which contains saponin and is used for cleaning textiles.
The family is divided into 6 subfamilies by Focke in Pflanzenfamilien as given below:
I. Spiraeoideae:
Stipules usually absent; receptacle flat or slightly concave; stamens 10-co, carpels 12-1 (usually 5) in a central whorl, ovules 2 or more in each; fruit a cluster of follicles.
II. Pomoideae (Pyroideae):
Stipules present; receptacle deeply cup-shaped; stamens many; carpels 5-2, syncarpous and completely adnate to the inner wall of the receptacular cup forming an inferior ovary; ovules 2 in each locule; fruit apseudocarp or pome, seed 1 in each chamber.
III. Rosoideae:
Stipules adnate to petiole; receptacle a deep cup or convex and swollen, rarely flat; stamens ∞; carpels many, free on the flat or convex receptacle or at the bottom of the cup-shaped torus, ovules 2 or 1 in each carpel; fruit a cluster of 1- seeded drupelets or achenes, the drupelets may fuse to form a pseudocarp or berry; seed 1 in each chamber.
IV. Neuradoideae:
Stipules minute or absent; receptacle cup-shaped; stamens 5+5, filaments long; carpels 3-10, horizontal and verticillate, ± connate and adnate to the receptacular cup which enlarges and forms a dry covering in fruit, ovules 1-2 in each carpel, pendulous; seed 1 in each mature carpel.
V. Prunoideae:
Stipules small, often caducous; receptacle cup-shaped; stamens 10, 20 or more on the rim of the cupular receptacle; carpel 1, rarely up to 5, at the centre of the receptacular cup forming a superior ovary, ovules 2, pendulous in each carpel; fruit a one seeded drupe.
VI. Chrysobalanoideae:
Stipules present; flowers usually zygomorphic; receptacle saccate or spurred on posterior side; stamens 10, pushed to the anterior side and often monadelphous; carpel solitary, free from the receptacle and superior, ovules 2, erect, style gynobasic or lateral, often carpels 2 and united; fruit a drupe.
The last subfamily, i.e. Chrysobalanoideae is raised to the rank of a distinct family by most authors as Chrysobalanaceae. Heywood who recognises Chrysobalanaceae as a distinct family arranges the rest of the 5 subfamilies in 2 groups depending on the basic chromosome numbers as noted below:
Group I—basic chromosome nos. 7, 8, 9, Subf. 1 Sipraeoideae, Subf. 2 Rosoideae, Subf. 3 Neuradoideae, Subf. 4 Prunoideae.
Group II—basic chromosome no. 17, Subf. 5 Maloideae.
The subfamily Neuradoideae is also recognised by some as deserving distinct family status but most authors are in favour of retaining same under Rosaceae.
Hutchinson, however, treats the family Rosaceae in a broad sense and divides the family into 20 tribes, viz:
(1) Quillajeae,
(2) Spiraeeae,
(3) Neillieae,
(4) Gillenieae,
(5) Neuradeae,
(6) Osmaronieae,
(7) Pruneae,
(8) Chiysobalaneae,
(9) Ulmarieae,
(10) Rubieae,
(11) Holodisceae,
(12) Rodotypeae,
(13) Kerrieae,
(14) Potentillae,
(15) Dryadeae,
(16) Poterieae,
(17) Cercocarpeae,
(18) Adenostomateae,
(19) Roseae and
(20) Pomeae.
The characteristic anatomical features are the presence of tracheitis and fibre-tracheids with bordered pits, solitary vessels small as well as large, with simple perforations, often ring porous alternate intravascular pitting and apotracheal diffuse wood parenchyma.
The solitary vessels, trachleds and fibre-tracheids indicate that the family is primitive to some extent. This is supported by the morphological characters of flat or convex receptacle in some genera, many free stamens and free carpels. Fossil records also show that Kojaceae is one of the most ancient families among the Dicotyledons.
Engler included several families in his Rosales along with Rosaceae, e.g., Crassulaceae, Cephalotaceae, Saxifragaceae, Pittosporaceae, Brunelliaceae, Cunoniaceae, Myrothamnaceae, Bruniaceae, Hamamelidaceae, Eucorniaceae, Platanaceae, Crossosomataceae, Connaraceae and Leguminosae. But Rosales of others contains only few families and the order is considered to have given rise to many other orders of Dicotyledons.
Rosaceae is allied to Saxifragaceae. According to Hutdhinson it is derived from the same stock as Dilleniaceae. It is also related to Leguminosae, the flowers of Prunoideae and Chrysobalanoideae having monocarpellary pistil and in Chrysobalanoideae the flowers being zygomorphic.
Chrysobalanaceae as a distinct family may be described briefly in the following manner: Trees and shrubs. Leaves simple, alternate, stipulate, entire. Flowers bisexual or unisexual, usually zygomorphic. Receptacle very deep, prolonged to a tubular structure, in racemose inflorescence. Calyx of 5 sepals, +unequal or calcarate at base.
Petals 5, often unequal, shortly unguiculate, inserted at the mouth of calyx, rarely corolla absent. Stamens 2-many (300 in Couepia), filaments filiform pushed to anterior side, often monadelphus, anthers introrse.
Ovary superior or semi-inferior, of 3 carpels but only one carpel develops; ovules 2, basal, erect; style lateral or gynobasic. Fruit a drupe with bony endocarp, rarely a crustaceous berry. Seeds with fleshy cotyledons and without endosperm.
Family # 7. Leguminosae:
Herbs, shrubs or trees, sometimes climbers and lianas; trees are evergreen or rarely deciduous. Leaves simple or pinnately or digitately compound; alternate or opposite, stipulate; a pulvinus is often present at the base of the petiole or petiolules. Inflorescence racemose, often paniculate, rarely in globose heads or solitary.
Flowers zygomorphic or actinomorphic, bisexual, hypogynous, rarely perigynous. Sepals 5, rarely less, usually connate at base, imbricate or rarely valvate.; the odd sepal is anterior.
Petals 5, rarely less, usually free, unequal or equal, imbricate or rarely valvate. Stamens 10, often many, rarely less than 10, free or monadelphous or diadelphous, filaments equal or unequal; anthers dehiscing by longitudinal slits or by apical pores; pollens are often in tetrads.
Ovary superior or rarely semi-inferior, monocarpellary with posterior ventral suture, lateral at first but ultimately terminal; ovules on marginal placentation; funicle rather prominent; style usually bent; stigma simple.
Fruit usually a legume, the valves divaricating on maturity and usually twisting; or fruit is a lomentum or fleshy. Seed usually with shining testa, variously coloured or often mottled; cotyledons plano-convex; endosperm absent or in a very thin layer.
The large family is divided into 3 clear subfamilies, viz. Mimoseae, Caesalpineae and Papilionaceae the characters of which are given below:
i. Mimosae (or Mimosoideae):
Predominantly trees; bark exuding a gum. Leaves are usually bipinnate, sensitive or possessing sleep-movement character; in some Acacia modified into phyllodes; stipules usually represented by a pair of thorns. Flowers in compact globose capitula or in spikes, often paniculate, regular, hypogynous or perigynous, usually 4-merous.
Calyx gamosepalous. Corolla gamopetalous; aestivation valvate; corolla often absent. Stamens equal or double the number of petals or numerous, free or monadelohous, often adnate to the corolla; filaments much longer than corolla and often coloured; pollens in tetrads. Fruit a follicle or lomentum or nut. Seeds flat or compressed; embryo straight.
About 2,800 species in 38 genera; mainly tropical and subtropical; largest genus’ Acacia consists of about 750 species many of which are Australian.
ii. Caesalpineae (or Caesalpinioideae):
Trees and shrubs. Leaves paripinnate or bipinnate, rarely simple and bilobed. Inflorescence is usually a raceme rarely corymb or flowers solitary.
Flowers slightly zygomorphic, hypogynous or perigynous, 5-merous. Calyx gamosepalous” or sepals free, imbricate, usually 5, rarely less. Corolla of5 petals, imbricate in ascending order, the odd 5th posterior petal is innermost in bud enclosed by the lateral pair which are again enclosed by the 2 lowest anterior petals.
Stamens 10, free, rarely united below, often a few reduced to staminodes, filamens often unequal, anthers dehiscing lengthwise or by apical pores, rarely stamens less than 10 or very rarely 11-12. Ovary superior or semi-infetior, often stipitate, straight or curved.
Fruits dehiscent or indehiscent, with or without transverse septa. Embryo straight. About 3,000 species in 180 genera, mainly in tropical and subtropical countries. Cassia containes about 400 species.
iii. Papilionaceae (Papilionoideae or Papilionatae):
Mostly herbs, shrubs also common, trees and climbers frequent. Leaves pinnate, rarely digitate or ternate, sometimes simple. Inflorescence is a raceme or spike or capitulum, rarely an umbel. Flower strongly zygomorphic, 5-merous, hypogynous. Calyx gamosepalous and persistent.
Petals 5, very unequal and papilionaceous; the posterior is the largest covering the others in the bud, the laterals more or less lanceolate and slightly curved, covering the anterior pair in between them, the anterior petals usually asymmetrical in shape and more or less united to form a boat-shaped structure; the posterior petal is called the standard petal or vexillum, the laterals are called wings and the united anterior pair is the keel, the aestivation is vexillary i.e., imbricate in descending order; all petals have a claw at the base.
Stamens 10, diadelphous, 9 + 1 or 5+5; where 9 are united the free stamen is posterior; often the posterior stamen is sterile or altogether wanting and there are 9 monadelphous stamens. Ovary or the style only is curved. Fruit a pod or lomentum or nut, very rarely a drupe. Seeds curved with a curved embryo: endosperm absent.
Species about 10,000 in about 500 genera distributed all over the globe excepting artic region. The largest genus Astragalus contains about 2,000 species. The subfamily being very large, variation is noticed in vegetative as well as floral parts. In Carmichaelia australis R. Br. and Bossiaea rufa R. Br. the branches are flat while the leaves are scale like or without a blade.
The 3 leaflets in Desmodium motorium (Houtt.) Merr. are very unequal, the laterals very small and show a peculiar movement with rise of temperature as the day advances. In some genera e.g., Genista, Ononis, etc. the compound leaves are unifoliate. The persistent calyx of Anthyllis is membranous and bladder-like and encloses the nut and falls with it; the calyx helps in the dispersal of the fruit by wind.
Trifolium has a globose inflorescence and gamopetalous corolla. In Sophora and Ormosia stamens are free. The legume in Astragalus is incompletely 2-locular due to the formation of a septum by the incurved dorsal suture.
Dipteryx and Andira have drupaceous fruit Fruits are geocarpic in Arachis hypogaea L., Trifolium subterraneum L. Vicia amphicarpa Doroth. etc. where the stalk of the ovary elongates after flowering and pushes the young fruit into the earth and the fruit ripens underground. The embryo in the seeds of Cicer and Arachis is almost straight.
Typical floral formula:
The flowers are especially adapted for cross pollination by insects in the family Leguminosae. In Papilionaceae the structure of the flower, the coloured petals and presence of nectar in many are factors that are well suited to attract the insects.
In Caesalpineae the same factors are responsible while in some cases the long coloured filaments make the flowers more attractive. In Mimosae the flowers being crowded in the inflorescence and having long exserted coloured filaments produce the same effect.
There is not much difference in the wood anatomy in the three subfamilies. However in Papilionaceae the sieve tubes are as thick or slightly thicker than phloem parenchyma and have simple transverse plates; oblique and tangenital patterns of vessels are distinct: fibres are rarely septate, anomalous secondary growth occurs in the stem of twiners.
In Caesalpiniaceae the sieve tubes are much thicker and shorter and have inclined plates; vessels occasionally oblique or tangential; fibres commonly septate. In Mimosae the sieve tubes are very long and narrow; oblique and tangential patterns of vessels are not at all distinct; fibres commonly septate.
The large family includes many species which are economically important.
A few are named below:
Mimosae:
Acacia catechu Willd.—Catechu, Kattha, (India) used for colouring khaki clothes and taken with betel leaves. Acacia mearusii De Wild., A. pycnantha Benth. and A. dealbata Link (Australian)—source of Wattle bark. Acacia stenocarpa Hochst (Ethiopia) and A. Senegal (L) Willd. (Tropics) yield gum arabic.
Acacia melanoxylon R. Br., A. visco Lour. ex. Gris. Albizzia procera Benth. A. lebbek Benth. (India), Xylia doiabriformis (Burm.) Benth. supply useful timber. Acacia nilolica (L.) Willd. ex. Del. (India) is the Babul-tree, the timber of which is very hard and is used in various ways.
Prosopis juliflora (Sw.) DC (Mexico) is the mesquite tree with sweet pods, cultivated for fodder. Entada phaseoloides Merr. and E. pursaetha DC. (India) are lianes which have curved lomentum as long as 50 cm. or more have large seeds called “Gila” used to wrinkle fine clothing’s.
Adenanthera pavonina Linn. (India) yields a red dye from the heart.
Mimosa pudica Linn, (originally from Brazil) is the sensitive plant, a herbaceous climber growing wild in different parts of India.
Caesalpineae:
Tamarindus indica Linn. (India) is the Tamarind tree the fleshy indehiscent fruit of which has an acid pulp much used in curries and for preparing a soothing drink. The timber is also useful.
Hardwickia binata Roxb. is a good timber tree. Melanoxylon brauna Schoff. yields very hard and durable timber.
Cassia acutifolia Delile and (C. senna L.) are the source of Senna-leaves used as purgative. The pulp of the fruit of C. fistula Linn.—Amaltas of India has the same property.
Haematoxylon campechianum Linn, of Trop. America yields a blue, dye from the heart wood and the stain haematoxylin used in microscopic preparation is obtained from it, Caesalpinia sappan Linn (Malaya) yields a red dye.
Saraca asoca (Roxb.) De Wilde the famous “Ashoke” tree of India so often mentioned in Sanskrit literature is cultivated for the flowers which have a petaloid calyx–, the corolla being absent. The bark of this tree has medicinal properties.
Many are cultivated as ornamental plants or as avenue trees, e.g., Delonix regia Raf —the Gulmor, originally from Malagasi, Amherstia nobilis Wall, of Burma, Caesalpinia pulcherrima Sw, and several species of Cassia.
Caesalpinia crista Linn, a scandent shrub, spiny all over, found in the plains of India have seeds with medicinal properties.
Papilionaceae:
Economically this subfamily is more important than the other two. Here are included all the species of pulses, beans, some dye-yielding plants, a few medicinal plants, some fibre plants and many ornamental trees, shrubs and herbs. Leaves of a few are also used as pot-herbs and a few good fodder.
Pulses:
Pisum sativum Linn—the pea, Cicer arietinum Linn—the gram, Cajanus cajan (L.) Millsp. the Arhar, Vigtia mungo (Linn.) Hepper, the Urud or Mashkelai, V. ra- diata (L.) Wile, the Mung dal, Lens culinaris Medic, the lentil, Lathyrus sativus L. the grass pea, etc. Phaseolus vulgaris Linn, is the French bean, Vicia faba L. the broad bean, Dolichos lablab Linn, the lablab bean, Canavalia ensiformis (L.) DC. the Jack bean, Phaseolus lunatus Linn, the Lima bean, Glycine max (L.) Merr. the Soya bean, etc.
Indigsfera tine tori a Linn, and a few other species of Indigofera give a bide dye while Genista tinctoria Linn, yields yellow dye. Pterocarpus santalinus Linn, is the red Sandalwood. Trigonella foeruim-graecum Linn, the Methi, Glycyrrhiza glabra Linn., and Psoralea coiylifolia L. are important medicinal plants. Crotalaria juncea Linn.—the Sunn-hemp yields a strong bast fibre. Dalbergia sisoo Roxb. and Pterocarpus marsupium Roxb. and a few other species of these two genera yield good timber.
Abrusprecatorius Linn., the Gunja, has small scarlet seeds with a black spot which are used as weights by the goldsmiths; the seeds are strongly poisonous, while the root can be used as a substitute for the root of Glycyrrhiza glabra. Denis elliptica Benth. has poisonous roots from which “Rotenone”, an insectiside is obtained.
Pachyrhizus angulatus Rich, a climber has tuberous roots which are sweet and edible. Lathyrus macrorrhizus Wimm. also has tuberous roots and used similarly. Pueraria mirifica A. Shaw is the rejuvenating plant of Thailand, the tuberous root of which contains a oestrogenic substance.
Pueraria tuberosa DC. of India has root tubers also having medicinal properties. P. thunbergiana Benth. is the Kudzu-vine a valuable fodder plant, the root tubers of which yield starch.
Arachis hypogea L. is the ground nut, that sends its fruits below the soil after flowering. This is much cultivated for the seeds which are edible and yield an edible oil.
Aeschynomene aspera L. and A. indica L. have spongy wood used for manufacturing solar hats, toys etc. and as bottle corks.
Many species have large and showy flowers and are often cultivated. Bulea monosperma O. Ktz. and B superba Roxb. are the Palas and Lata Palas respectively. Erythrina uariegata Linn, and other species of the genus are the “Mandar” of Sanskrit literature. Sesbania grandiflora Pers. has large white or pink flowers.
Milletia ovalifolia Kurz. has beautiful mavue flowers in drooping racemes. Gliricidia maculata H. B. K. is common in gardens cultivated for white or pink flowers in short racemes. Crotalaria sericea Retz. a shrub with simple leaves and golden yellow flowers is a common garden plant. Lathyrus odoratus Linn, is the Sweet pea, a garden annual.
Leguminosae is closely related to Rosaceae. Both the families are considered to have been derived from a common ancestor. Ckrysobalanus and allied genera approach very near to the subfamily Caesalpiniaceae.
Floral anatomy reveals that there are 5 traces in the carpels of Mimosae as noted in Rosaceae. Many authors treat the 3 subfamilies as distinct families, e.g. Hutchinson who includes the 3 families in a new order as Leguminales which he places just after Rosales.
Hutchinson calls the families as Caesalpiniaceae, Mimosaceae and Papilionaceae. Takhtajam follows Hutchinson but instead of Papilionaceae he calls the family as Fabaceae and the name of the order is changed to Fabales. Recently Heywood keeps Fabales as a distinct order although he does not split Leguminosae into 3 families. Cronquist treats Leguminosae as a single family and keeps it in Rosales.
The distinguishing characters of the 3 subfamilies are quite clear but there is good reason to treat Leguminosae as a single family as there are several genera intermediate between the subfamilies.
Thus we have Brownea of Caesalpineae where the flowers are in dense clusters and are more or less regular with long exserted stamens, and by such characters approaching Mimosae very much. Cercis siliquastrum Linn, the Judas tree of the subfamily Caesalpineae has some what papilianaceous flowers.
The tribe Swartzieae is placed by some in Caesalpineae and in Papilionaceae by others; while some workers like to treat this group as a distinct subfamily of Liguminosae. Sophora, Ormosia and a few other genera of Papilionaceae have free stamens like the flowers of Mimosae. Cicer and Arachis of Papilionaceae have straight embryo as is found in Mimosae and Caesalpineae.
