Classification of Rubiales: 3 Families | Dicotyledonae

In this article we will discuss about the classification of Rubiales. According to Hutchinson, Rubiales consists of three families:- 1. Rubiaceae 2. Caprifoliaceae 3. Valerianaceae.

Family # 1. Rubiaceae:

Rubiaceae are herbs, shrubs or trees, rarely climbing. Leaves are simple, opposite cy rarely whorled, Stipulate; stipules interpetiolar or intrapetiolar.

Inflorescence a cyme or cymose panicle or umbel or a compact globose head. Flowers are hermaphrodite, actinomorphic, epigynous or semiepigynous, 4-5-merous. Sepals 4-5, valvate, often united, persistent. Petals 4-5, connate in a tube below with funnel-shaped, salver-shaped or rotate limb, valvate, imbricate or contorted.

Stamens as many as petals and alternate to them, epipetalous; anthers 2-celled, introrse. Carpels 2, united to form a 2-celled inferior or semi-inferior ovary; ovules 1-many in each cell, anatropous, on axile plancenta; integument one and thick; style filiform with a bifid or multifid stigma; ovary is crowned by a fleshy disc.

Fruit a capsule, berry or drupe, sometimes an aggregate. Seeds often winged, with copious fleshy or cartilaginous endosperm and straight or curved embryo: endosperm absent in some genera.

The large family varies much in habit from prostrate or trailing herbs like Dentella, Spermacoce, Galium, etc., to shrubs, e.g. Ixora, Gardenia, etc. trees, e.g. Anthocephalus, Adina, etc. and climbers like Uncaria, Paederia, etc.

In Uncaria some branches are modi­fied into hooks that help the plants to climb. Some are epiphytes, e.g. Myrmecodia, Hydnophytum, Hymenopogon, etc. Myrmecodia and Hydnaphytum are myrmecophilous, that shelter ants in hollow tuber-like swellings at the base of the stem.

Stipules are interpetiolar in most genera, while intrapetiolar stipules occur in Gardenia, Randia, Paoetta, etc. In Gardenia the stipules are connate and cover the growing apical bud of the shoot and are deciduous. In Adina, Nauclea, etc. the stipules are very large, while in Galium and Rubia they are like ordinary leaves.

Solitary flowers are often found in Gardenia; in Rubia a perfect dichasial cyme occurs while In Hamelia the inflorescence is 2-3-chotomous subscorpioid cyme. The dichasial cymes are condensed into heads in Anthocephalus, Nauclea, Adina, etc.

In Morinda and Sarcacephalus the flowers are also aggregated and basally connate. Cinchona has a paniculate inflorescence. Flowers are more or less zygomorphic and bilabiate in Henriquezia and Posoqueria. In Coprosma and Anthospermum the flowers are unisexual.

One of the calyx segment is much larger than the others and petaloid in Mussaenda rendering the flower very attractive. In Nematostylis the calyx lobes enlarge in fruit. Ovary is half inferior in Synaptantha and superior in Pagamea and Gaertnera. In Gardenia ovary is unilocular and the placentation is parietal. Hamelia and Hamiltonia have typical 5-merous flowers with 5-celled ovary.

In Vangueria the ovary is 3-6-celled and in Lasianthus 4-9-celled. In Morinda, Sarcocephalus, etc. the basal parts of the densely aggregated flowers fuse to form a syncarp. The seed is winged in Cinchona.

The floral formula of Rubiacea is represented as:

The family consists of about 7000 species under 500 genera, occurring in the tropics and subtropics and extending to the temperate and even to the frigid zone. About 550 species are found in India mostly in the plains and at lower elevations in the hills.

Rubia cordifolia Linn, grows in the Himalayas up to an elevation of 2500 mtr. Species of Galium are often found at an altitude of 4000 m. Luculia, another Himalayan genus, has beautiful mauve flowers in terminal corymbs. In the plains trees are Anthocephalus chincnsis A Rich.

Adina cordifolia Hook. f., Mitragyna parvifolia (Roxb.) Korth, etc. Gardenia, Ixora, Pavetta, Coffea, etc. are shrubs, while a large number of herbs like 01- denlandia, Hedyotis, Borreria, Anotis, etc. are quite,common. Uncaria and Paederia are climbers or twiners occurring in foot hills of the outer Himalayas and Assam.

In this family presence of raphides in the cells is a characteristic feature. Crystal sands are also present in the cells of many genera. Vessels are solitary or in multiples of 4 or more.

Perforations are simple, rarely scalariform, and the intervascular pitting alternate. Wood parenchyma is apotracheal. Fibres are usually simple pitted. In some genera fibres are present in the pericycle. Anomalous secondary thickening is met with in Basanacantha and Rhabdodendron.

The family is divided into 3 sub families as noted below:

Subf. I Rubioideae:

Calcium oxalate crystals present in leaves, hairs on stem and leaves often with transverse walls, heterostyly is common; stipules often with several long slender teeth, seeds without endosperm, (usually herbaceous).—11 tribes.

Subf. II Cinchonoideae:

Calicium oxalate crystals absent, hairs without trans­verse walls, heterostyly usually absent, stipules usually entire, seeds with plenty of endosperm (Woody plants).—17 tribes.

Subf. Ill Guettardoideae:

Calcium oxalate crystals absent; hairs without transverse walls, heterostyly absent, seeds without endosperm (Woody).—1 tribe.

Affinity of Rubiaceae is rather controversial. It has much in common with Logania­ceae, such as opposite leaves, well developed stipules, tycarpellate ovary, etc; both families contain similar type of alkaloids.

But in Loganiaceae the ovary is superior and there is internal phloem in the vascular bundles. Rubiaceae comes closer to Capri- foliaceae both having opposite leaves, cymose inflorescence, stamens as many as petals, bisexual and tetracyclic flowers, inferior ovary, etc.

In Caprifoliaceae stipules are absent and no alkaloid is present in any part of the plants. With Cornaceae and Umbelliferat it seems to be related also having epigynous flowers and an epigynous disc and the dense cymose inflorescence, bicarpellate ovary and integument one only.

The family Rubiaceae includes several species economically important. Anthoce­phalus chinensis A. Rich.—the Kadamba tree, Adina cordifolia Hook. f.—the Haldu, and a few other trees yield timber which is light and strong and suitable for making tool- handles, toys, picture-frames, etc.

Species of Cinchona is the source of the alkaloid quinine. This genus is indigenous to Brazil and Mexico and a few species are cultivated in different tropical countries. In the E. Himalaya there are a few plantations where C. officinalis Linn. C. succirubra Pav., C. calysaya Wedd. and C. Ledgeriana Moens. are cultivated.

A factory for the manufacture of quinine has been established at Mungpoo. Another important medicinal plant is Cephaelis ipecacuanha (Brot.’) A. Rich.—Ipicac plant, a native of Brazil is the source of the alkaloid emetine obtained from its gnarled roots.

Paederia foetida Linn.—Bhadali, growing in the Terai region is recommended in indigestion and stomach troubles. Oldenlandia corymbosa Linn.—Khetra parpati, is much used by the Indian Vaids. Coffea arabica Linn, is an important beverage plant of N. Africa and W. Asia.

It is much cultivated in S. India, Java, Ceylon, Brazil and W. Indies. Coffee-powder is obtained by grinding the roasted seeds of this plant and of C. liberica Linn. Rubia cordifolia Linn.—Manjistha, growing in temperate Himalayas, and R. tinctoria Linn, of Europe yield a red dye.

Uncaria gambier Roxb.—an Indo-Malayan plant yields gamber-catechue which is used medicinally and also as a dye. A yellow dye is obtained from Morindn tinctoria Roxb.

A few shrubby plants are cultivated for the showy flowers, e.g. Gardenia jasminoides Ellis, Lucutia gratissima Hook, f., Hameha patens Jack, Ixora arborta Roxb. ex Smith. I. coccinea Linn., Mussaenda glabra Vahl., etc. Anthocebhalus chinensis a timber tree is also cultivated in parks and gardens. Vangueria edulis Vahl. has edible fruits.

Family # 2. Caprifoliaceae:

Caprifoliaceae are erect shrubs, often attaining tree-size, rarely twiners. Leaves are simple, rarely com­pound, usually opposite, exstipulate or with reduced stipules. Inflorescence cymose in 3- or 2-flowered dichasia; cymes are often grouped in an umbel-like arrangement.

Flowers are fragrant, bisexual, regular or irregular, epigynous, usually pentamerous. Calyx 5-lobed, valvate. Corolla 5-lobed, rotate or salver-shaped, or bilabiate; lobes valvate or imbricate. Stamens inserted on corolla tube and alternating with corolla lobes; anthers 2-lobed, introrse.

Carpels 2-8, syncarpous; ovary inferior, 1-8-celled; style one or as many as carpels; ovules 1 or more in each cell of ovary on axile placenta. Fruit a berry or drupe.

Seeds with fleshy endosperm and straight embryo. The opposite leaves in some Lonicera unite and form a broad collar encircling the stem. Stipules are present in Sambucus. In Viburnum and Lycesteria the stipules are modified to extra floral nectaries.

In Symphoricarpus and Diervilla the inflorescence becomes racemose. In Sambucus and some Viburnum the small flowers are massed together in an unibellate inflorescence. In V. opulus Linn, the marginal ray florets are much larger than the others making the inflorescence conspicuous and attractive.

These ray florets are barren. In Dipelta and Linnaea stamens are 4 in number and, didynamous. In Leycesteria and some Sambucus carpals are 5 and in Diervilla carpels are only 2.

In Symphorycarpus carpels are 4 and the ovary is 4-celled; the median cells have many ovules in each in 2 rows, all of which are abortive while the lateral cells have solitary ovules which develop into seeds.

In Einrwea ovary is 3-celled with several abortive ovules in 2 of the cells while the third cell has a single ovule which develops into a seed. The fruit in Linnaea is a nut which remains enveloped by pair of large persistent bracteoles.

The typical floral formula is:

The family with about 270 species under 17 genera is found mainly in the north temperate region with a few in the tropics. Several species of Lonicera, Viburnum and Sambucus are found in the Himalayas and Assam. S. javanicus Bl., a large shrub, grows in Bengal and at low elevations in Assam.

Caprifoliaceae is allied to Rubiaceae having cymose inflorescence, tetracyclic, epigynous flowers and fleshy endosperm. It is also related to Loganiaceae, Cornaceae and Umbelliferae to some extent.

The family is divided by Fritsch into 4 tribes as noted below:

I. Sambucieae:

Leaves pinnately compound or 3-foliolate; anthers extrorse; fruit drupaceous or berry.

II. Viburneae:

Leaves simple; anthers introrse; fruit drupaceous; ovary 1-5- celled with 1 ovule in each cell.

III. Linnaeae:

Leaves simple; anthers extrorse; ovary 3-celled, 2 cells with many abortive ovules, 3rd cell with one ovule; fruit a nut.

IV. Lonicerae:

Leaves simple; anthers extrorse; ovary 2-8-celled, ovules several in each cell; fruit a berry.

Economically the family is not very important. Ripe fruits of Sambucus are made into wine and those of Viburnum are edible. The leaves of some species of Sambucus, Viburnum, Lonicera and Triosteum are strong purgative and emetic. A few species of Lonicera, Viburnum, Sambucus and Symphoricarpus are cultivated for the beautiful iragrant flowers.

Family # 3. Valerianaceae:

Valerianaceae are annual and perennial herbs with aromatic rhizome, rarely undershrubs. Leaves are simple or compound, opposite, exstipulate, often radical. Inflorescence a dense panicle of cymes, or the cymes often condensed into a head; bracts and bracteoles present.

Flowers are small, more or less zygomorphic, bisexual or unisexual, epigynous. Calyx in flower represented by an epigynous ring, persistent and later developing into pappus or plumose outgrowths or a 4-5-toothed structure.

Corolla tubular, slightly irregular above with 5 unequal lobes or bilabiate, saccate or spurred at the base; lobes imbricate. Nectar is secreted in the sac or spur. Stamens 1-4, epipetalous; anthers bilocular, in­trorse.

Ovary 3-carpcllary, syncarpous, 3-celled, inferior; style with a bipartite or simple stigma; ovule 1 in one of the cells, pendulous and anatropous, and develops into a seed, while the other 2 cells of the ovary are empty. Fruit an achene; seeds without endosperm.

The family consisting of about 350 species under 10 genera distributed in the north temperate zone of the globe; a few are found in the high mountain of S. America.

There are 16 species in India all being in the hills. Valerianaceae is placed in Rabiales by Engler and its affinity with Rubiaceae and other families of the order has been recognised by most workers in taxonomy. It resembles Composite by the compact type of inflorescence, formation of pappus in some genera and epigynous ovary.

The family appears to be much advanced as is evident from the following characters:-

1. Predominantly herbaceous.

2. Aggregation of small flowers in dense inflorescence.

3. Reduction of calyx which is modified into pappus or scales.

4. Ovary inferior.

5. Special adaptation for cross pollination by insects, e.g., nectar secreted and stored in sac or spur, and protandrons androecium.

6. Distribution of fruit over wide area with help of pappus.

The family includes a few plants reputed for medicinal value. Valeriana officinalis Linn, yields the Valerian root. Nardostachis jatamansi DC. is an Ayurvedic drug available in the Himalayas. Leaves of Valeriana olitoria Linn, are used as salad. A few are culti­vated as ornamental plants among which Centranthus ruber DC is very popular.