RANUNCULACEAE WEEK- MAY 02-08, 2011

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Nidhan Singh

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May 1, 2011, 2:26:35 AM5/1/11
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Dear Friends,

This is my privilege to discuss family of the week with a group where
putting up things is always learning rather than dictating anything. I
am hopeful to get enriched by valuable inputs from all the members of
the group. Here, to start with, general points to keep in mind about
the family Ranunculaceae are being discussed:

Ranunculaceae Jussieu

(The Buttercup Family or The Crowfoot Family)

A highly variable family of about 1900 species of dicotyledonous
plants that includes the buttercups, monkshoods, anemones, clematis,
delphiniums and hellebores, distributed mainly in North temperate and
arctic regions. Most members of the family are at least slightly
poisonous.

In India, this family is represented by 20 genera and about 150
species, mostly confined to mountainous regions.

Vegetative characters:

Nearly all the members of the family are herbaceous, except Clematis
the species of which are woody, generally climbing. Majority of the
Ranunculaceans are perennials, but for a few like Nigella being
annuals. Almost all of them love terrestrial, moist localities but few
species of Ranunculus are truly aquatic (e.g. R. aquatilis).

Rootstock sometimes becomes tuberous with age in perennials. Leaves
usually alternate (opposite in Clematis) with sheathing bases and
often very much divided, usually exstipulate but stipulate in
Trollius, Caltha, Thalictrum (leaf base is broadened into stipule-like
lobes) and Ranunculus.

Leaf shape variable, usually leaves are simple and palmately lobed (as
in Ranunculus) or decompound (like Delphinium), entire (Caltha) and
pinnately compound (Clematis). Aquatic species of Ranunculus show
heterophylly with submerged leaves finely dissected. Leaves are
modified into tendrils in Clematis aphylla.

Inflorescence and Flowers:

Inflorescence, though quite variable, is more often a branched cyme.
In Anemone, Nigella and Eranthis a single terminal flower is produced.
Elongated racemes can be seen as in Delphinium, Aconitum and also much
branched panicles can be found as in Clematis and Thalictrum. In
Nigella and Anemone, there is sometimes an involucre of green leaves
below the flower, usually alternating with the calyx.

The floral parts are free and spirally arranged upon a more or less
elongated receptacle, and their number varies considerably from one
genus to the other. Flowers are mostly bracteate, actinomorphic
(zygomorphic in Delphinium and Aconitum), hermaphrodite (except in
some species of Thalictrum), pentamerous and hypogynous.

The perianth may be distinguishable into calyx and corolla or it may
be undifferentiated. The innermost perianth segments often bear
conspicuous nectaries or very small and reduced nectariferous sacs or
scales.

The calyx consists of five to eight sepals which are distinct, usually
caducous, with imbricate or valvate aestivation. In Delphinium and
Aconitum, the sepals are petaloid and the posterior sepal is spurred.

The corolla is usually of five, free, symmetrical (Ranunculus) or
irregular (Delphinium, Aconitum) petals. In Delphinium, the posterior
pair of petals forms spur which projects into spur of the petal. In
Aquilegia all the five petals form a spur at the base. Ranunculus has
a pocket-like nectary at the base of each petal. In Caltha, Clematis
and Anemone, the petals are completely absent and sepals become
petaloid.

The androecium usually of many, polyandrous and spirally arranged
stamens (in some genera like Helleborus, Nigella and Aquilegia the
stamens are arranged in definite rings). Anthers are adnate,
dithecous, extrorse and dehiscing longitudinally. The filaments are
beautifully coloured in some species of Thalictrum. Flowers are
usually protandrous and the stamens after dehiscence bend outwards
from centre.

The gynoecium is usually of numerous free carpels arranged spirally on
a distinct thalamus, few taxa, of course, have a definite number of
carpels. Aquilegia has five carpels and Delphinium has 1-3 carpels. In
few others like Actaea and Cimicifuga, carpels are reduced to one
only. Not only in number, gynoecium shows variation in cohesion also.
In some species of Helleborus, the carpels are connate at the base,
whereas in Nigella the five carpels are completely united.

The ovary is superior, unilocular with one to many ovules. The
palcentation may be basal (Ranunculus), apical (Clematis) or marginal
(Delphinium) and in Nigella, where gynoecium is syncarpous, ovary is
pentalocular with axile placerntation.

Fruit usually a group of achenes or follicles (capsule in Nigella,
berry in Actaea). Seeds with small embryo and oily endosperm.

Well-known representatives of the family include:

Ranunculus (Buttercup), Clematis (Virgins-bower, Traveller’s joy),
Anemone (Wind Flower), Delphinium (Larkspur), Aconitum (Aconite),
Paeonia (Peony),
Caltha (Marsh marigold), Aquilegia (Columbine), Nigella (Love-in-a-mist),
Helleborus (Hellebore) etc.

I hope to see some of my “favorites” of the family from the group in
the coming week. The family is poorly represented in our area, and I
apologize that I won’t be able to upload many members.

Thanks and Happy Ranunculaceae Week.


--
Regards,

Dr. Nidhan Singh
Department of Botany
I.B. (PG) College
Panipat-132103 Haryana
Ph.: 09416371227

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