Classification of Myrtiflorae: 9 Families | Dicotyledonae

In this article we will discuss about the classification of Myrtiflorae. According Engler, Myrtiflorae consists of nine families:- 1. Lythraceae 2. Punicaceae 3. Rhizophoraceae 4. Combretaceae 5. Myrtaceae 6. Lecythidaceae 7. Melastomaceae 8. Hydrocaryaceae 9. Onagraceae.

Family # 1. Lythraceae:

Lythraceae are herbs, shrubs or trees, often with square stem. Leaves are simple, opposite or whorled, entire, exstipulate or with minute stipules. Inflorescence paniculate, racemose or cymose, or flowers solitary, axillary or terminal. Flowers are bisexual, actinomorphic or rarely zygomorphic, perigynous, subtended by a pair of bracteoles, large and showy or minute; receptacle cup-shaped.

Sepals 4, 6 or 8, rarely more, on the margin of the recep­tacle, free or united, valvate. Petals as many as sepals, free, usually crumpled, inserted on the margin of the receptacular cup and alternating with the sepals, usually clawed.

Stamens twice as many as petals in 2 whorls, inserted on the receptacular cup lower down, sometimes inner whorl absent, or stamens many with centripetal development, rarely stamen solitary; filaments unequal, bent in bud; anthers bilocular, introrse, dehiscing longitudinally.

Carpels 2-6; united to form a semi-inferior or superior, 2-6- chambered ovary; ovules usually many in each chamber, anatropous, ascending on axile placentas; style simple with capitate stigma; rarely ovary unilocular and the placentation is parietal. Fruit a capsule. Seed with a straight embryo and without endos­perm.

Plants vary in habit from tiny little herbs like Ammania, Rotala, etc. to tall timber trees, e.g. Lagerstroemia speciosa (L.) Pers., L. parviflora Roxb., L. macrocarpa Wall., etc. Hydrolythrum is a submerged herb while a few Ammania and Rotala species are also aquatic.

Woodfordia and Cuphea have tubular calyx, in the former the limb of calyx is oblique while in the latter the flower is zygomorphic. Lythrum salicaria Linn, has trimorphic flowers where stamens and styles are of different lengths in different flowers.

Lafoensia has 8-r6 segments or lobes in each perianth whorl , while in Peplis and some species of Ammania flowers are apetalous. Stamen is one in some species of Rotala. In Lagerstroemia the seeds are winged.

Formula for a typical flower of the family is:

Vessels are solitary or in multiples of 2-3 cells. Intervascular pitting is alternate. Fibres are with simple pits. Intraxylary phloem is almost always present.

The family comprises about 475 species in 23 genera found in the tropical and subtropical regions with a great majority occurring in tropical America. About 50 species are found in India in the plains while a few ascending to 1500 mtrs. in the hills.

Lagerstroemia speciosa (L.) Pers. yields hard and durable timber suitable for making boats. A few other species of this genus are also good timber trees and most have showy lowers and are planted as avenue trees. L. indica Linn, is an arboreous shrub much cultivated in gardens.

Lawsonia inermis Linn, also a large shrub is cultivated as a hedge of which the leaves yield a reddish orange dye known as Mehendi used to stain palms and finger nails by Indian ladies and for dyeing hair or beard by old men.

Leaves and barks have medicinal properties also. Ammania vesicatoria have leaves which are very acid and are used for raising blisters for relieving pain in rheumatism. The blisters are however too irritating and very painful.

The leaves of Ammania baccifera Linn, are also used in a similar manner. The leaves and flowers of Woodfordia fruticosa (L.) Kurz. are extensively used in tanning and in dyeing silk. Ctiphia platycentra and Lythrum salicaria Linn, are cultivated for their beautiful flowers.

Lythraceae is closely allied to Onagraceae, Melastomaceae and Myrtaceae, and also to Punicaceae and Sonneratiaceae which families were included in Lythraceae in the old system of classification by Bentham and Hooker.

Family # 2. Punicaceae:

Punicaceae are shrubs or small trees, sometimes armed with spines; young branches 4-winged. Leaves are simple, opposite or fasciculate, exstipulate. Inflorescence is a terminal few- flowered cyme, or flowers solitary. Flowers are regular, hermaphrodite, peri- or epigynous, with a tubular or urceolate hypanthium. Calyx lobes 5-8, fleshy, valvatc, persistent.

Petals 5-8, imbricate, inserted on the rim of the hypanthium, crumpled in bud. Stamens many in several whorls, inserted on the upper half of the hypanthium, free; anthers 2-called, dorsifixed, dehiscing longitudinally.

Carpels 8-12; ovary syncarpous, inferior or semi-inferior with 8-12 locules in 2 concentric rings at the early stage with axile placentation, gradually in course of development the outer series of 5-9 locules is carried upwards and ultimately superposed over the originally inner series of 3 loculei, and the placentas of the upper locules changed to parietal position; the ovules nuwer- out, anatropous; style simple; stigma capitate. Fruit a berry, crowned with persistent calyx lobes. Seeds with a fleshy testa, a straight embryo and without endosperm.

This.is a unigeneric family of western Asia with only 2 species of the genus Punica, viz. p. granatum Linn, and P. protopunica Balf. f. The former, the pomegranate plant is much cultivated for the edible fruit in almost all tropical and subtropical countries and has been introduced to tropical America. The edible part of the fruit is the sweet fleshy testa of the seeds.

This is closely related to Lythraceae in which it was formerly included. Hutchinson considers it closer to Myrtaceae than to Lythraceae and keeps Punicaceae in Myrtnlw while Lythraceae is in his Lythrales far removed from Myrtales.

Family # 3. Rhizoplioraceae:

Rhizoplioraceae are trees or shrubs; some are halophytic usually with pneumatophores and stilt roots. Leaves simple, coriaceous, opposite; stipule interpetiolar often caducous, or stipules absent. Inflorescence cymose, axillary, or flowers solitary. Flowers are actinomorphtc, bisexual or rarely unisexual, perigynom or cpigynousj reccptade cup-shaped or pitcher-shaped.

Sepals usually 4-8 or sometimes 3-16, valvate, more or less connate at base Mid adnate to the ovary, leathery and persistent. Petals as many as and smaller than the sepals, free, convolutcor inflexed, entire or fringed or flappy.

Stamens usually twice as many as petab, each petal embracing a pair of stamens, rarely stamens numerous, situated on the margin of a lobed disc, all in one whorl; filaments short or long; anthers 4-ceIled, dehiscing longitudinally, introrse, carpels 2-6, syncarpous; ovary 2-6-locular, inferior or seimi-inferior, usually with 2 pendulous, anatropous ovules in each cell on axile placentas, rarely ovary unilocular with parietal placeittas; micropyle directed outside and upwards; style short, one or more; stigma simple or lobed, usually persistent.

Fruit a berry or a capsule, rarely a drupe. Seeds with or without endospertn, rarely arillate; cotyledons 2 or more; embryo straight, small; if endosperm is present- elongated, if endosperm absent cotyledons often contain chlorophyll; usually the germination is viviparous.

Mostly the plants stand on stilt roots, the base of the stem having perished early; the stilt roots are provided with lenticels permitting communication of air through intercellular spaces. In some genera such communication is effected by the pneunoatophores. Viviparous germination of the seeds is another characteristic feature of this halophytic family.

The hypocotyl grows very long pushing its way through the open wide micropyle and piercing the fruit wall. It reaches a length of 20-30 cm. or more and hangs freely with the fruit which ultimately drops to the soil and the hypocotyl is embedded in the mud and a number of rootlets grows very quickly fixing the seedling rigidly to the soil. Carallia and a few other genera growing inland have seeds which are not viviparous.

Floral formula for the family is expressed as:

The flowers of Anisophylla and Gynotroches are unisexual. The ovary is superior in Gynotroches and Cassipourea. Anisophylla has the styles free. The epidermis of the leaves is thickly cuticiilarised having one- or more-celled hypodermal layer underneath. Stomata are deep-seated with well-developed front-cavity.

Vessels have simple and scalariform perforations and wood parenchyma is para- tracheal. The cortex of the stilt root is spongy due to the presence of a complex type of intercellular spaces. Tannin containing cells are present in almost all parts of plants and often H-shaped and branched idioblasts occur in leaves, roots and younger parts. These also contain tannin and mucilage.

The family contains 17 genera and about 120 species, a few genera growing on the sea-shores and near estuaries forming the mangrove vegetation. In India 9 species are found, 8 in the tidal forests on the coast and one viz. Carallia brachiata Merr. in the terai region of N. Bengal, Assam, Bangladesh and west coast of India.

The family is allied to Mytiacea and other families of the order, having inferior ovary and in the structure of ovule. The genus Cassipourta is placed by some workers in a different family Cassipemacea, Similarly Anisophylla is placed by some in Anisophylleaceae.

The family contains but a few useful plants. Umber obtained from Brugmtn gjfmnorhiia (Una,) Liamk. and from B. stxmgula Poir. is used in home-construction and also as fire-wood. Timber of Carallia brachiata Merr. is used in various ways and an edible oil is obtained from the seeds.

Family # 4. Combretaceae:

Combretaceae plants are trees or shrubs, often lianous; armed or not. Leaves are simple, alter­nate or opposite, entire, exstipulate. Inflorescence spicate or racemose or paniculate. Flowers are bisexual, rarely unisexual, actinomorphic or zygomorphic, bracteate; the tubular receptacle together with the adnate tubular base of the calyx forming a hypanthium. Calyx with 4-5 or more persistent lobes; lobes valvate.

Corolla lobes as many as calyx lobes, small, imbricate or valvate, free, often absent. Stamens 4-5 in one whorl, or double the number and in 2 whorls, inserted on the calyx tube; filaments inflexed in bud; anthers bithecal, versatile.

Carpels 4 or 5, or often less, syncarpousr; ovary inferior, unilocular, angular or ribbed, the ribs equal in number to calyx lobes; ovules 2-6, anatropous, pendulous from the apex of the ovary chamber by long funicles; micropyle directed upwards and outwards; style slender with a capitate or pointed stigma. Fruit a drupe, 1-seeded, with angled or winged pericarp.

Seed without endos­perm; embryo with convolute cotyledons or cotyledons often folded, rarely flat.

Floral formula is expressed as:

The family contains 600 species under 20 genera occurring in the tropical and subtropical countries of the world and a few genera are restricted to the mangrove forests in the sea-shores, e.g. Lumnitzera, Laguncalaria, Conocarpus, etc. which have the characteristic features of the holophyte plants. Lumnitzera littoria (Jacq.)Voigt. is found in the Sunderban and other tidal forests of India.

In the vascular bundles of the stem both intraxylary and interxylary phloems are present. Vessels have simple perforations; intravascular pitting is alternate and wood parenchyma is paratracheal.

The long fibres have simple pits. Tannin containing cells are found in every parts but more in the pericarp of the fruit. The family is closely related to Myrtaceae and Rhizophoraceae, and to the other families of the order to some extent.

Several species of Combretaceae are useful as timber, medicinal plants, source of tannin and as ornamental plants. Anogeissus latifolia (Roxb.) Wall., A. acuminata (Roxb.) Wall., Terminalia tomentosa W. & A. are important timber trees of India. Terminalia ivorensis A. Chev. is the Idigbo timber, T. superba is the Afara timber and T. sericea Burch. is the Asegai of commerce.

The bark of T. Arjuna W. & A. is highly valued as a cardiac tonic. T. chebula Retz. is the chebulic myrobalan and T. bellirica Roxb. is the beleric myrobalan. T. catappa Linn, a tall tree growing in coastal parts of India and Malaya is often planted as an avenue tree in tropical countries. Quisqualis indica Linn.—the Rangoon creeper is a favourite of the Indian gardens. A few species of Combretum are also cultivated in the gardens as ornamental plants.

Family # 5. Myrtaceae:

Myrtaceae are evergreen large or medium sized trees or shrubs. Leaves are containing oil glands, usually opposite, simple, coriaceous, entire, exstipulate. Inflorescence cymose or racemose or paniculate, rarely flowers solitary. Flowers are hermaphrodite, regular, usually epigynous, with a pair of bracteoles at base.

Sepals 4-5, connate at base and united with the receptacular cup to form a hypanthium, lobes free, quincuncially arranged. Petals 4-5 usually free, imbricate or connate to form an operculum.

Stamens numerous, rarely few, free or slightly connate at base, in several whorls on the edge of the hypanthium developed centripetally, sometimes in fascicles opposite to the petals; filament, often coloured; anthers 2-celled, versatile or dorsifixed, introrse, dehiscing longitudinally or sometimes apically, connective often conspicuous and gland-tipped.

Carpels 2-5, united to form an inferior or semi-inferior 2-5-locular ovary, often unilocular, rarely many-locular ovary; ovules 2-inany in each chamber on axile or rarely parietal pla­centas, campylotropous or anatropous, obliquely pendulous; the style simple, stigma capitate.

Fruit a berry or loculicidal capsule, rarely drupaceous or nut like. Seeds usually few; testa modified into wings or may be horny, leathery or membranous; embryo straight or curved, endosperm absent or scanty.

Myrtus and Psidium have solitary flowers. Sepals inconspicuous, or absent in Eucalyptus. Petals connate in Eucalyptus forming an operculum that falls off early and releases the stamens. The anthers are basifixed in Calothamnus. Stamens in Melaleuca are polyadelphous and in one whorl; the bundles are equal to the number of petals and opposite to them. Nut-like fruit is found in the Australian tribe Chamaelaucieae.

Lysigenous oil glands are present in stem and leaves as well as in floral organs and fruits. Tannin containing cells sometimes also occur. Vascular bundles are bicolateral; the vessels are usually solitary, of small dimensions and with simple perforations; intervascular pitting is alternate. Xylem parenchyma is both apotracheal and paratracheal. Fibres are borded pitted.

Floral formula is expressed as:

The family consists of about 3000 species under about 100 genera, with main centres of distribution in Australia and tropical America. The genus Eucalyptus with over 300 species is restricted to Australia and adjacent islands in the Pacific and Indian Oceans.

The species of this genus are lofty trees some attaining 150 m. in height. The family is represented in India by about 50 species of Syzygium which are indi­genous and a few species of other genera cultivated as ornamental trees or for their economic importance. Myrtaceae is allied to Rhizophoraceae, Lythraceae, Combretaceae and Onagraceae and to Sonneratiaceae and Melastomaceae to some extent.

The family is divided into 2 subfamilies as given below:

I. Myrtoldeae: Lvs. usually opposite; flowers epigynous; fruit fleshy, berry or drupe. Trop. America (mainly).

II. Leptospermoideae: Lvs. opposite or alternate; flowers epigynous or perigynous; fruit dry, capsule or nut-like. Australia (mainly).

The family includes many useful plants. Many species of Eucalyptus yield valuable timber, e.g. E. crebra F. Muell., E. paniculata Sm., E. punctata DC., E. leucoxylon F. Muell. etc. Oil of Eucalyptus is distilled from the leaves and younger parts of E. sideroxylon A. Cunn., E. leucoxylon F. Muell., E. elaeophora F. Muell., E. globulus Labill., E. dealbata A. Cunn. etc.

An astringent taniniferous substance called Kino is obtained from many species and many are planted in gardens for their grace and beauty. Many species have been introduced into India among which E. citriodora Hook is quite common.

Many species produce edible fruit, viz. Psidiumguajava Linn.—the guava, original of Brazil is now cultivated in many tropical countries. P. cattleianum Sabine is the Straw­berry guava. Myriciaria cauliflora Berg, is the Jaboticabo fruit. Eugenia uniflora Berg, is the Surinam-cherry.

Feijoa sellowiana Sabine is the Fekhow fruit. Syzygium cumini (L.) Skeels is the Jamoon of India, S.jambos (L.) Alston—the Rose apple growing in different parts of India, S. samarangense (Bl.) Merr. & Perry, is the Jamrool, indigenous to Malaya and S. malaccense (L.) Merr. & Perry, the Malacca Jamrool. S. aromaticum (L.) Merr. & Perry is the clove-plant of Zanzibar.

Pimenta dioica (L.) Merr. is the Allspice and P. racemosa (Mill.) Moor is the Bay oil tree, by distilling the leaves of which the oil is obtained. Melaleuca leucadendron Linn, yields the Cajuput oil. Leptospermum scoparium Forst. is the Tea tree or Manuka. Callistemon lanceolatus DC—the Bottle-brush tree of Australia with aromatic leaves is cultivated in many countries as an ornamental plant.

Family # 6. Lecythidaceae:

Lecythidaceae are trees, usually evergreen. Leaves are simple, whorled near the tip of the branches, exstipulate. Inflorescence a raceme, spike or small cymose clusters near the end of the branches. Flowers are hermaphrodite, regular or zygomorphic due to unequal development of stamens; the axis forms a flat disc to which the petals and stamens are attached.

Calyx persistent, of 4-6 or more sepals, united near base, often tubular, rarely the calyx splits irregularly into 2-3 segments, valvate. Petals 4-6 or more, free, imbricate, distinct or adnate at base to the staminal tube.

Stamens numerous united in several whorls, often unequally developed resulting in the zygomorphy of the flowers, often some stamens are sterile; the disc extends inside the androecium; the outer whorl often forms a corona; the stamens fall with the petals.

Ovary inferior, 2-6-celled; style simple with lobed or capitate stigma; ovules 1 ∞, anatropous on axile placentation. Fruit drupacious, berry-like or capsular, opening on top by a lid. The seed is more or less completely filled by the embryo; cotyledons obsolete; endosperm absent.

The family with about 220 species under 18 genera is distributed in the tropical countries of the world. In India it is represented by the genera Careya and Barringtonia while Couroupita guianensis Aubl. of tropical S. America is cultivated in parks and gar­dens in India. The fertile stamens are borne on a fleshy band on one side of the flower while the sterile stamens are grouped round the ovary forming a ring.

The band with fertile stamens curves over the ovary. This arrangement appears to the Hindus as a symbol of a cobra over the lingam-stone and the tree is called as the Naglingam tree. Lecythis zabucajo Aubl. is another curious tree having large woody gourd like fruits opening at the top.

The fruits are used to catch monkeys who insert their hands to get the content inside the fruit and are unable to withdraw the same and are captured. The tree is popularly known as monkey-pot tree or monkey-puzzle tree. In this family internal phloem is -lacking and the secondary phloem is stratified into fibrous and soft portions.

Lecythidaceae was formerly included under Myrtaceae from which it differs in the absence of oil glands in the leaves and absence of internal phloem.

Its affinity with Myrtaceae is recognised by most workers who place it in Myrtales. Cronquist while in­cluding Lecythidaceae in Myrtales remark that this family does not bear close relationship with any family of this order and would be proper to place it in a distinct monotypic order.

Economically the family is not very important. Barringtonia acutangula Gaertn.— the Hijal is common in lower Bengal and other parts of India. It yields valuable timber and the bark is used in tanning. The root is supposed to have properties similar to quinine.

The fruit is also medicinal. The bark is thrown in water to stupefy fish before catching. The timber of Careya arboria Roxb. is also used in different ways and the leaves are a food of Tassar-silk-moths. Timber obtained from other trees are also useful. Gustavia augusta Linn, and Couroupita guianensis Aubl. are often planted as orna­mental trees.

Family # 7. Melastomaceae:

Melastomaceae are herbs shrubs or trees, rarely epiphytes; a few are aquatic and some are root-clim­bers; the aerial root often swell to form tubers where ants take shelter, an example of myrmecophily.

Leaves are simple, opposite and decussate or whorled, exstipulate, with multicostate reticulate, convergent venation; the 2 leaves of a pair often unequal, the larger leaf frequently has a sac-like outgrowth having entrance on lower surface; such outgrowths or domatia are found sometimes on the petiole also; the domatia give shelter to ants.

Inflorescence cymose or corymbose or paniculate, or the flower solitary or in small clusters. Flowers hermaphrodite, actinomorphic or slightly zygomorphic, peri- or epigynous, 4-5 merous on a bell-shaped receptacle with coloured bracteoles. Sepals 4-5, united to form a tube, adnate to the receptacle, often forming a cap, or free from the receptacle and persistent; often reduced to a mere rim round the floral axis.

Petals 4-5, free, generally brightly coloured, twisted or imbricate. Stamens double the number of petals and in 2 whorls, sometimes one whorl reduced to staminodes or suppressed; filaments all equal or alternately long and short, usually geniculate; anthers 2- or 4-celled, rarely unithecal, dehiscing longitudinally or by 1 or 2 apical pores; connectives variously appendaged.

Ovary inferior or semi-inferior, carpels and cells usually 4-5, sometimes more or fewer, rarely up to 14 and very rarely only 1; ovules anatropous, usually many on axile or parietal placentas, rarely placentation is free- central; style and stigma simple. Fruit a capsule or a berry; seeds small, straight or curved; embryo small; cotyledons fleshy; endosperm absent.

Pachycentria is epiphytic, the aerial roots of which bear domatia. Memecylon is a genus of trees where the leaves are unicostate. The leaves of Mouriria are also unicostate. Sonerila, Gravesia and Bertolona have variegated or spotted leaves.

Sonerila has trimerous flowers. Memecylon has unilocular ovary and the placentation is free central. In Osbeckia the capsule opens apically by pores and the capsule of Sonerila opens by apical valves. The seeds of Osbeckia and Melastoma are curved. The cotyledons in Memecylon are convolute.

Floral formula:

Aerenchyma is formed in the submerged stem and root of aquatic species. Vascular bundles have internal phloem. Concentric cortical and pith bundles also occur. Vessels have simple perforations and alternate intravascular pitting. Wood parenchyma is usually para tracheal or sometimes mixed with Apo tracheal. Pericycle is not conti­nuous but made up of isolated fibres and sclerotic thickened cells.

Melastomaceae is a large family with about 4000 species under 240 genera. They are distributed in the tropical as well as temperate regions of the globe with a chief centre of distribution in S. America. The family is well represented in India with several species of Melastoma, Osbeckia, Oxyspora, Memecylon, Sonerila, etc.

Melastoma malabathricum Linn, has large mauve flowers and occurs in the plains as well as in the hills at low elevations. Memecylon has very small flowers in axillary or extra-axillary clusters.

Species of Memecylon grow in tropical region. M. edule Roxb. and M. capitella- tum Linn, are very common in the plains., Osbeckia nepalensis Hook, f., 0. crinita Benth, Oxyspora paniculate Hook. f. are common in the Himalayas and Naga hills at about 2000 m. Tibouchina semidecandra Linn, is cultivated in Darjeeling and other hill stations for its large purplish violet flowers.

Melastomaceae is allied to Myrtaceae and also to Lythraceae to some extent. According to Hutchinson relationship of Melastomaceae with Myrtaceae is not very clear although he includes Melastomaceae in his Myrtales and remarks that Lythraceae is not at all close to Melastomaceae.

Melastomaceae is Hivided into 3 subfamilies by Krasser, viz.:

I. Melastomatoideae:

Fruit many seeded capsule, embryo minute, ovules on projecting axile placenta. Melastoma, Osbeckia, etc.

II. Astronioideae:

Fruit many seeded capsule, embryo minute, ovules on basal or parietal placenta. Astronia, Kibessia, etc.

III. Memecyloideae:

Fruit 1-5 seeded berry, embryo large, placentation axile or free-central. Memecylon.

The genus Memecylon is placed by some in a family of its own, e.g. Memecylaceae.

Family # 8. Hydrocaryaceae (Trapaceae):

Hydrocaryaceae are annual herbs floating in fresh water pools. Leaves are dimorphic; the submerged pinnatipartite with filiform segments, opposite; the floating leaves rosulate, simple and rhomboid with rather long spongy petiole dialated near its apex. Flowers are solitary, axillary, regular and hermaphrodite, tetramerous, perigynous.

Sepals 4, connate in a short tube, adnate to the base of the ovary; lobes persistent, 2 or all becoming spine scent in fruit. Petals 4, small, white, inserted on the margin of the epigynous disc. Stamens 4 in one whorl. Ovary semi-inferior, of 2 united carpels, bilocular; ovule 1 in each cell, often abortive in one cell; pendulous from the top of the inner angle; style’ subulate; stigma capitate.

Fruit an 1-seeded drupe, obpyraimidal in shape with an fearly deciduous fleshy pericarp and a 2-4 horned stony endocarp (i.e. a pyrene); the horns represent the persistent sepals which are often barbed at the apex; persistent base of the style remains as a central apical beak.

Seed solitary, inverted, with 2 very unequal coty­ledons, one almost filling the seed and the other scale like; embryo small; endosperm absent; during germination the larger cotyledon remains in the seed while the smaller is carried up on the slender hypocotyl.

This is a unigeneric family of 30 species found in the Old World, while Trapa nutans Linn, has been introduced in tropical America. Fossil fruits of Tertiary period indicate that the family was more widely distributed in that period Trapaceae was included in Onagraceae from which it was separated by Engler for its perigynous, bilocular ovary and spiny fruit.

This treatment has been supported by most subsequent workers. Embryological and cytological data also speak in favour of segre­gation of Trapaceae as a distinct family.

The family is economically important for the edible fruit of different species of Trapa and for this reason different species are cultivated, T. bispinosa Roxb. is much cultivated in India and forms an important article of food in most parts.

Family # 9. Onagraceae:

Onagraceae are annual or biennial herbs, or shrubs, rarely arbore scent, often aquatic. Leaves are simple, alternate or opposite, rarely whorled, exstipulate. Inflorescence racemose or spicate, or flowers solitary and axillary, often pendulous. Flowers are hermaphrodite, acti­nomorphic, tetramerous and epigynous; the receptacle adhering completely to the ovary and produced above it forming the hypanthium or the so called calyx-tube.

Sepals, petals and stamens arise from upper edge of the hypanthium. Sepals 4, united near base and adnate to the hypanthium, valvate, usually persistent. Petals 4, free, imbricate, clawed.

Stamens twice as many as petals and in 2 whorls, free, the inner stamens shorter often sterile or absent; anthers bithecal, dehiscing longitudinally, often transversely divided in 2 or more stories by false partitions; pollens large, spherical, having 3 pores with protruding stoppers and are connected by viscid threads.

Carpels 4, united into a 4-celled inferior ovary with numerous ovules; style simple, long and filiform; stigma capitate, 4-rayed or notched; ovules anatropous, ascending, horizontal or descending on axile placenta.

A disc-like swollen structure is often present at the base of the style that secrete nectar or nectary is situated at the base of the calyx. Fruit a loculicidal capsule with a central column bearing the seeds, or a berry or 1-2 seeded and nut-like. Seeds with a small straight embryo and without endosperm.

Species of Hauya are trees and some Fuchsia species are climbing. Ludwigia is aqua­tic. Fuchsia and Circaea have small caducous stipules. Calyx in Fuchsia is petaloid, the petals small and in some scale-like. F. apetala has no petal as is the case in Ludwigia palustris. The central American genus Lopezia has strongly zygomorphic flower.

Here the petals are linear; the 2 anterior are turned obliquely backwards and bent like a knee with a nectary at the bend. Stamens only 2, the posterior is fertile and the anterior one reduced to a spathulate petaloid staminode.

Flowers of Circaea are dimerous with 2 stamens in one whorl. In Clarkia the antipetalous stamens are reduced to staminodes and in Eucaridium and Ludwigia these are absent. Pollens are in tetrads in Epilobium.

Circaea has 1-celled ovary with 1 ovule in each cell- Seeds of Epilobium are hairy on the chalazal end. Internal phloem is present in the stem. Vessels have simple perforations. Large aerenchyma occurs in the roots and submerged stems of Ludwigia. Raphides are also present.

The floral formula is represented as:

The family consists of about 800 species under 38 genera. They are distributed chiefly in the temperate and tropical regions of the northern hemisphere and more so in the New World. Epilobium with over 200 species are found in the temperate regions- all over the world.

Several species of Epilebium occur in the Himalayas and hills of Assam. Ludwigia perennis Linn. (Syn. L. parvijlora Roxb.), L. adscendens (L.) Hara (Syn. Jussiaea repens Linn.) and L. octovalvis (Jack) Raven (Syn. J. suffruticosa Hook, f) are found in the plains of E. India in marshy areas.

The family is allied to Melastomaceae, Myrtaceae and Lythraceae. Close affinity bet­ween these 4 families is recognised by Takhtajan and also by Cronquist while according to Hutchinson Onagraceae is closer to Lythraceae than to Melastomaceae and Myrtaceae. Hutchinson includes this family in his Lythrales with Lythraceae, Haloragidaceae, etc. while Myrtaceae and Melastomaceae are in his Myrtales.

The family is of little economic importance, except that the berries of some species of Fuchsia are edible and some plants with showy flowers are cultivated in gardens as ornamental plants. The family has become famous for Oenothera lamarckiana which was used by de Vries for his experiments on mutation.