Classification of Umbelliflorae: 2 Families | Dicotyledonae

In this article we will discuss about the classification of Umbelliflorae. According to Engler, Umbelliflorae consists of two families:- 1. Araliaceae 2. Umbelliferae.

Family # 1. Araliaceae:

Araliaceae are perennial herbs or shrubs or trees, rarely lianas, very rarely scandent epiphytes; stem and branches often armed with prickles; profusely lenticelled. Leaves of Araliaceae are cauline or radical, simple or digitate or pinnate, often peltate, alternate or whorled near the end of branches; stipulate or exstipulate; stipules interpetiolar or intrapetiolar; petiole long, often prickly.

Inflorescence terminal or axillary racemes or umbels, or panicles of umbels, sometimes subcorymbose, often a head or capitulum if the flowers are sessile: bracts and bracteoles persistent or deciduous; pedicels articulated or not. Flowers of Araliaceae is small, regular, bisexual or polygamous, rarely unisexual epigynous.

Receptacular tube or hypanthium cupuliform or obconic or cylindrical. Calyx persistent, lobes or teeth short, 5-8, often represented by an undulate rim. Petals 3-10, valvate or imbricate, inserted on the margin of a fleshy disc, free or shortly connate and forming a calyptra. Stamens usually as many as the petals and alternating with them; anthers dorsifixed, often versatile, dehiscing longitudinally.

Disc annular, epigynous, fleshy. Carpels 1-5 rarely more, syncarpous; ovary inferior, 1-5-celled or rarely more celled, apex fused to the disc; style single, often 2-4-fld, rarely as many as carpels or wanting; stigmatic surface terminal or along the adaxial surface of the style; ovule 1 in each cell of ovary anatropous, pendulous from the axile placenta,, with ventral raphe.

Drupes often sulcate, with thin exocarp and fleshy mesocarp, both on drying form a membranous covering over the pyrenes. Seeds with a thin seed coat, usually laterally compressed, with minute straight embryo and copious fleshy endosperm; endosperm often ruminate.

Schizogenous resin passages occur in all vegetative parts. Vessels are disposed in groups, these are often ring porous, sometimes with spiral thickenings; intervascular pitting is usually scalariform. Medullary and cortical bundles are also reported in many genera. Fibres are simple pitted and septate; there is not much fibre in the pericycle.

Floral formula:

The family contains 63 genera and about 750 species in the tropical and temperate regions of the globe, with 2 main centres of distribution, one in tropical America and the other in the- Indo-Malesian region.

India has 64 species which are found to be growing more in the hills with a few occurring also in the plains. Hedera nepalensis Koch is the Himalayan Ivy, while H. helix Linn, is the true Ivy of Europe. The fossil records reveal that the family had a wider distribution in the Tertiary period parti­cularly in the northern temperate regions.

Harms divided the family into 3 tribes as noted below:

I. Schefflereae. Petals valvate, not clawed, wide at has

II. Aralieas. Petals imbricate, wide at base.

III. Mackinlayeae. Petals valvate shortly clawed, inflexed above.

A close relationship between Araliaceae and Umbelliferae has been recognised by most authors. Many workers trace the affinity of Araliaceae also with Cornaceae. Hut­chinson however considers Araliaceae to be related to Cornaceae and Alangiaceae as well as to Nyssaceae, Garryaceae and Caprifoliaceae, and these six families are included in his.

Araliales of Lignosae while Umbellifereae is in a monotypic order Umbellales of Herbacena.

The roots of Panax ginseng Linn, are the Ginseng of the Chinese used as medicine for various ailments. Aralia nudicaulis Linn, is a substitute for Sarsaparila. A few other species also possess medicinal properties. Hedera helix Linn.—the Ivy plant, and species of Acanthopanax, Panax, Polyscias, etc. are cultivated as garden-ornamentals.

Leaves of a few species are good fodder for cattle. Timber obtained from the short tree Schefflera elata Harms, is used to make soft planks for packing cases. Polyscias fruticosus Harms, is said to be an antidote of snakebite.

Family # 2. Umbelliferae (Apiaceae):

Umbelliferae are annual or biennial herbs or shrubs, usually aromatic, often rhizomatous or with tuberous roots; stem ultimately hollow at the internodes. Leaves of Umbelliferae is alternate; rarely opposite, pinnately or palmately compound or decompound, rarely simple, stipulate or not; petiole sheathing at the base; leaves are often basal and sometimes heteromorphic.

Inflorescence is a simple or compound umbel surrounded by an involucre of bracts, terminating the main stem and branches, often in compact head, very rarely solitary; umbels often heteromorphic.

Flowers of Umbelliferae is bisexual, rarely unisexual, monoecious or dioecious, or polygamous, actinomorphic, epigynous and pentamerous, small, white or yellow, rarely pink or violet. Calyx gamosepalous, 5-toothed or entire, often persis­tent. Petals 5, free, valvate or imbricate, often unequal in size.

Stamens 5, free, usually bent inwards in bud, arising from the epigynous disc and alternating with the petals; anthers basi-or dorsifixed. Carpels 2, syncarpous, forming a bilocular inferior ovary with one pendulous ovule in each cell; styles 2, surrounded at base by a 2 lobed nectar- disc or stylopodium; stigmas capitate.

Fruit is a schizocarpic cremocrp splitting into 2 mericarps which remain attached to a slender, often forked carpophore; each mericarp contains a seed, with five ridges or costae outside and the furrows or valecullae; the ridges contain vascular bundles and under .the furrows there are schizogenous oil ducts or vittae. Seed with copious endosperm and a small embryo.

A predominandy herbacious group of plants but a few genera are shrubs while Eiyngium bupleuroides, E. sarcophyllum and E. inaccessum are small trees with woody trunk. Hydrocotyle is a creeper and so is Lilaeopsis a rhizomatous herb of the muddy coasts. Azorella is a cushion-plant and Gingidia forms rosettes.

Schizeilema is stoloniferous. Damns has a thick taproot. Leaves are simple in Hydrocotyle, Bupleurum, etc. Vena­tion of leaves often parallel in Bupleurum resembling those of the Monocots. Eryngium has the leaf-margin spiny and looks like a spiny thistle with compact floral heads.

Aciphylla has also spine-tipped leaves and bract-segments. Umbels are usually com pound but simple umbels are found in Centella, Astrania as well as in most Hydrocotyle, rarely solitary flowers occur in Azorella and some Hydrocotyle. Flowers in Eryngium are sessile and crowded in dense heads surrounded by spiny bracts.

In Petagnia the in­florescence is of a dichasial type. In Eryngium and Bupleurum bracts are often large and coloured. In Mathiasella bupleurioides the involucre is composed of showy petaloid bracts. The flowers are usually regular but the marginal flowers in the umbels of Daucus carrota Linn., Turgenia latifolia and Artedia squamata and species of Heracleum are zygo­morphic having the anterior petal largest and the posterior pair the smallest.

Unisexual flowers occur in Echinophora, Arctopus, Mathiasella, etc. In Astrania the flowers are polygamomonoecious. In Mathiasella bupleurioides the pistillate flowers are apetalous. In the subfamily Hydrocotyloideae the vittae on the mericarps are absent or they are on the ridges.

The development of a flower in this family is peculiar. The stamens are formed first, next are the petals and then the sepals. The carpels are formed last and are dis­tinct at the beginning but ultimately fuse by their margins.

The roof of the rudiments of the carpels form the glandular disc or the stylopodium through which the styles come out. Flowers are protrandous but in case of Hydrocotyle and Sanicula they are protogynous.

The floral formula for a typical flower of this family is represented as:

Oil or resin canals are present in the inner cortex, pericycle and sometimes in secondary phloem. Pericycle is composed of strands of fibres; it is often a continuous ring of fibres. The fibres are simple pitted, vessels are often in clusters and have simple .perforations or rarely scalariform. Wood parenchyma is paratraoheal. Crystals of calcium oxalate are often present in the pericarp.

Umbelliferae is a large family of about 3000 species under 275 genera. It is distri­buted over almost all parts of the globe but more in the north temperate regions.

In India 180 species are found mostly in the hills. Centella asialica Urb. is quite common in the plains as well as on the hills up to a height of 1500 nt. Seseli indicum Wt. & Arn., Oenanthe benghalensis Benth., Pimpinella Ikyw.ana Wall. etc. arc other species that grow wild in the plains.

The family is divided by Drude into 3 subfamilies as noted below:

I. Hydrocotyloideae:

Stipules present; fruits with no free carpophore, and with hard endocarp; vittae absent or in the ridges only.

II. Saniculoideae:

Stipules absent; endocarp soft, exocarp rarely smooth, style long, with capitate stigma, surrounded by ring-like disc; vittae various.

III. Apioideae:

Stipules absent; endocarp soft or hardened by sub-epidermal fibre layers; style on apex of disc; vittae various.

Umbelliferae is closely allied to Araliaceae. That the affinity between the 2 families is close is also supported by pollen characters as well by chemical tests. The 2 families are included in the same order by most workers except Hutchinson who places Aralia­ceae in Araliales under Lignosae and Umbelliferae under Herbaceae.

According to him Araliaceae is a primitive family while Umbelliferae is much advanced. Umbelliferae resembles Compositae (Asteraceae) to some extent in the reduction of calyx, bicarpellate syncarpous ovary with 2 distinct styles. It is therefore presumed that Compositae originated from Umbelliferae through Rubiaceae.

Cornaceae and Alangiaceae although put in a distinct order other than Umbellifloreae (Umbellales) by Cronquist are Considered to be phylogenetically related to Umbelliferae by most workers; and these have been derived from Myrtales or from Rosales. Hutchinson considers that Umbelliferae is derived from Saxifragales while Cronquist expresses his opinion that Umbelliferae and Araliaceae originated from Sapindales.

The family Umbelliferae is very important for having many useful plants under it. A few are used as food and are cultivated, viz. Daucus carrota Linn.—Carrot, Apiumgra- veolens Linn.—Celery, Pastinaca saliva Linn.—Parsnip, Petroselinum crispum Nym.— Parsley, Anethum graveolens Linn.—Sowa or Sulpha, etc.

Ferula asafoetida Linn. F.foetida Regel and F. narthex Boiss. yield the gumresin Asafoetida (Hing), while F. rubricaulis Boiss and F. galbaniflua Boiss. give Galbanum gum. Trachyspermum ammi (L.) Sprague is the Ajwan, a source of thymol.

Coriandrum sativum Linn., Pimpinella anisum Linn. Foeniculum vulgare Mill., Cuminum cyminum Linn., Carum carui Linn, are the spice-plaitts. Conium maculatum Linn.—the Hemlock is a strong poison.