Ranunculaceae: Characters, Distribution and Types

In this article we will discuss about:- 1. Characters of Ranunculaceae 2. Distribution of Ranunculaceae 3. Economic Importance 4. Affinities 5. Types.

Characters of Ranunculaceae:

A. Diagonostic Characters:

Herbs, leaves exstipulate, incised blades, sheathing bases, flowers hypogynous, spiral or spirocyclic; sepals often decidous, usually petaloid; calyx and corolla free; stamens indefinite, free; carpels polycarpellary, apocarpous; fruit aggregate.

B. Vegetative Characters:

Habit:

The plants are annual or perennial herbs or a climbing shrubs (Clematis, Naravelia), rarely trees. They perennate by means of tuberous roots (Aconitum) or rhizomes.

Root:

Tap root, adventitious or tuberous (Ranunculus spp. and Aconitum). The tap root system is in the initial stage but sooner or later replaced by the adventitious roots.

Stem:

Herbaceous, in some climbing (Clematis) or underground rhizome or erect, branched.

Leaves:

Generally simple, alternate, or opposite (Clematis) exstipulate rarely stipulate (Thalictrum), sheathing leaf base, petiolate rarely sessile (Delphinium). In some aquatic species leaves may show dimorphy (Ranunculus aquatilis); unicostate or multicostate reticulate venation.

C. Floral Characters:

Inflorescence:

Solitary terminal (Anemone), axillary (Clematis), raceme (Aconitum, Delphinium) and cymose (Ranunculus spp.).

Flower:

Pedicellate, ebracteate rarely bracteate, hermaphrodite, (unisexual in Thalictrum). Mostly actinomorphic (Ranunculus) rarely zygomorphic (Delphinium and Aconitum) hypogynous, complete, pentamerous.

Calyx:

There is no distinction of calyx and corolla in most of the flowers. Sepals 5, caducous, polysepalous, petaloid, imbricate or valvate aestivation.

Corolla:

Petals 5, polypetalous, variously coloured, caducous or wanting; nectaries present at the base of petals. Petals are united to form spur (Delphinium).

Androecium:

Stamens indefinite, polyandrous, spirally arranged on the thalamus, inferior; anthers dithecous, extrorse and adnate.

Gynoecium:

Polycarpellary (one carpel in Delphinium and 3 to 5 in Aconitum), apocarpous rarely syncarpous (Nigella), ovary superior, marginal placentation (axile in Nigella).

Fruit:

Aggregate, etario of achenes (Ranunculus), etario of follicle (Aconitum), follicle (Delphinium), septicidal capsule (Nigella) or berry (Actaea), etario of drupes (Adonis), etario of berries (Hydrastis) and simple pod (Xanthorhiza).

Seed:

Small, oily and endospermic.

Pollination:

Generally entomophilous (Delphinium, Aconitum, Aquilegia) and anemophilous in Thalictrum.

Floral formula:

Range of floral structure:

Three sub-families have been recognised on the basis of floral structure viz.:

(a) Helleboreae,

(b) Anemoneae, and 

(c) Paeonieae.

Rendle is inclined to believe that the Anemoneae is more primitive than the Helleboreae.

In the Anemoneae the flowers are actinomorphic. In Anemone, for instance, flowers are solitary with five or six or more perianth leaves which are petaloid. True petals are altogether absent and as many as 13 rows of stamens along with numerous free carpels are found.

In Thalictrum, the inflorescence is a corymb or panicle; the perianth consists of 4-5 sepaloid structures. Stamens are numerous but carpels may be few. In Clematis there are 4 or more petaloid sepals with several stamens and carpels. In all the above three genera there is a pendulous ovule while in Ranunculus the ovule is erect.

In this genus there are 5 sepals followed by 5 petals. The stamens and carpels are numerous and free. The arrangement of stamens and carpels is typically spiral. In Myosurus all the five sepals have a basal spur; the stamens are few but carpels are many. In Adonis five sepals are followed by 8-16 coloured petals. As many as 21 rows of stamens may be counted; carpels also numerous.

In the Helleboreae the perianth is spirally arranged in the primitive genera but in the advanced forms it is arranged in a cyclic manner.

Two distinct tendencies are noticeable in this subfamily viz.:

(i) With actinomorphic flowers-considered more primitive.

(ii) With zygomorphic flowers – considered more advanced.

In Helleborus the perianth has five members followed by a number of honey leaves. These are nothing else but modified stamens belonging to the outermost row. The number of stamens may be 100 arranged in 13 rows.

In Isopyrum and Coptis also there are 13-rows of stamens but their total number is decreased. In Aquilegia the number of stamens may be only 15 or sometimes 20-25; there are only five carpels. Xanthorhiza also has a typical pentamerous condition with 5-10 stamens and 5 carpels. In Cimicifuga the number of carpels has been reduced. In Actaea the reduction in carpel has gone further so that only one carpel is found.

Zygomorphic tendencies are found in Trollius, Nigella, Delphinium, Aconitum etc. In Trollius there are 5-15 perianth leaves, 21 rows of stamen and 5-10 carpels. In Nigella we come across 5-perianth leaves, 8 honey-leaves, 8 rows of stamens and 5-12 syncarpous carpels.

In Delphinium and Aconitum zygomorphy arises due to spur on the posterior side. Normally there are only three carpels but in D. ajacis only one carpel is found.

In the sub-family Paeonieae the flowers have become hemicyclic or acylic. In Paeonia the flower is pentamerous with 5 sepals and petals each, indefinite stamens but only two to three carpels. Definite nectariferous structures cannot be found but a disc or ring like swelling around the carpels may develop.

Distribution of Ranunculaceae:

It is commonly known as buttercup family. It includes 35 genera and 1500 species out of which 163 species are confined to India. They are chiefly found in temperate and arctic regions.

Economic Importance of Ranunculaceae:

1. Condiment:

The seeds of Nigella sativa (H. Kalongi) are used as spice in pickles.

2. Medicinal:

Aconitum hererophyllum and A. napellus yield a number of alkaloids specially aconitin. This is used in acute and inflammatory diseases. The roots of Thalictrum yields “mamira”, which is used in opthalamia. Anemone pulsatilla is mostly used in feminine diseases and in gastric derangements. Pulsatilla obtained from Anemone pulsatilla is a good medicine for menstrual disorder.

Cimicifuga racemosa gives the black Snake root containing resins. This has been recommended for treatment of cholera and nervous pain. Helleborus niger and H. foetida produce glycosides useful as purgatives in veterinary practices. Delphinium staphisagria is used as antiparasitic ointment.

3. Ornamental:

Some of the plants are cultivated in gardens for their beautiful flowers viz., Ranunculus, Delphinium, Naravelia, Clematis, Nigella and Caltha.

Affinities of Ranunculaceae:

The family Ranunculaceae is one of the most primitive of the dicotyledons. Hutchinson, Bentham and Hooker have placed the family in the class of very early dicotyledons. Engler, Rendle and others put the family under the archichlamydeae.

The family is in its close relationship with the monocotyledons due to the a following facts:

(i) Tubular cotylar sheath formation and union of two cotyledons in Ranunulus ficaria, the sheath during germination is pierced by epicotyl.

(ii) Leaf bases are broadened into sheath and rhizome formation.

(iii) The course of vascular bundles and scattered arrangement in the stem of certain genera, e.g., Cimicifuga.

(iv) The endospermous seed with apical small embryo and copious endosperm.

(v) Lastly the free carpels, the resemblance of flowers with Alismaceae.

The family can be linked with Rosaceae on account of free and numerous stamens and carpels. The dimorphic leaves and hypogynous followers of Ranunculaceae trace the relationship with the family Nymphaeaceae.

Primitive characters:

1. Perennial habit (Aconitum, Clematis).

2. Presence of tree or shrub (Paeonia).

3. Presence of stipules (Thalictrum).

4. Leaves with reticulate venation.

5. Flowers hermaphrodite.

6. Actinomorphic symmetry.

7. Large number of petals.

8. Calyx and corolla free.

9. Gynoecium polycarpellary and apocarpous.

10. Ovule anatropous.

Advanced characters:

1. Plants are generally herbs.

2. Leaves compound (Clematis).

3. Stipules are absent except in Thalictrum.

4. Zygomorphic symmetry (Delphinium).

5. Unisexual flowers (Thalictrum).

6. Petals fused and forming spur (Delphinium).

7. Gynoecium syncarpous (Nigella).

Common plants of the family:

1. Aconitum:

Herb with medicinal properties due to the presence of several alkaloids.

2. Clematis:

Climber.

3. Delphinium:

Ornamentanal, cultivated in gardens.

4. Ranunculus:

Annual or perennial herb.

5. Nigella:

The seeds of Nigella sativa are used as a condiment.

6. Thalictrum:

Perennial herb with medicinal properties.

Division of the family and chief genera:

Engler and Prantl have divided the family into three tribes viz., Helleboreae, Anemoneae and Paeoniaeae. According to Hutchinson (1923) the family Ranunculaceae is divided into two sub-families.

I. Helleboroideae:

Carpels with more than one ovule; fruit follicle or berry.

Tribe (i) Helleboreae – Flowers actinomorphic.

Nigella, Helleborus, Aquilegia.

Tribe (ii) Delphinieae – Flowers zygomorphic.

Delphinium, Aconitum.

II. Ranunculoideae:

Carpels with one ovule; fruit a bunch of dry achenes very rarely berry.

Tribe (iii) Ranunculeae – Leaves alternate, sepal imbricate, flowers are not subtended by involucral leaves, sepal mostly caducous.

Ranunculus, Thalictrum.

Tribe (iv) Anemoneae – Leaves alternate, sepals mostly coloured and persistent, flowers subtended by an involucral leaves.

Anemone, Hepatica.

Tribe (v) Clematideae – Leaves opposite, sepals valvate or imbricate; corolla absent or represented by staminodes.

Clematis, Clematopsis, Naravelia.

Important Types of Ranunculaceae:

1. Ranunculus scleratus, Linn. (Fig. 24.5):

Habit:

An erect, annual herb.

Root:

Tap root, replaced by adventitious branched roots.

Stem:

Erect, herbaceous, green, glabrous, solid or fistular, branched with distinct nodes and internodes.

Leaves:

Simple, trilobed, or tripartite, each lobe is further divided with ovate cuneate segments. Alternate, petiolate, sheathing leaf-base, exstipulate, venation is reticulate multicostate.

Inflorescence:

Cymose, biparous.

Flower:

Pedicellate, bracteate, hermaphrodite, actinomorphic, complete, hypogynous, yellow.

Calyx:

Sepals 5, polysepalous, petaloid, aestivation quincuncial.

Corolla:

Petals 5, Polypetalous, obovate with pocket-shaped nectary on the inner side at the base of each petal, yellow, aestivation imbricate.

Androecium:

Stamens indefinite, polyandrous, spirally arranged, anthers elongated, filament long, basifixed, extrorse.

Gynoecium:

Polycarpellary, apocarpous, ovary superior, unilocular, with basal placentation.

Floral Formula:

2. Delphinium ajacis, Linn. (Fig. 24.6):

Habit:

Annual herb.

Root:

Tap root, branched, fibrous and annual.

Stem:

Erect, branched, herbaceous, green, glabrous, solid and cylindrical.

Leaves:

Cauline, simple, much dissected palmately lobed, alternate, exstipulate, sessile, venation reticulate multicostate.

Inflorescence:

Typical raceme.

Flower:

Pedicellate, bracteate, bracteolate (two violet coloured) complete, hermaphrodite, hypogynous and zygomorphic.

Calyx:

Sepals 5, petaloid, polysepalous, posterior sepal produced into a long spur, aestivation quincuncial.

Corolla:

Petals 4, gamopetalous, the posterior two petals are fused to form spur and projected into the spur of posterior sepal, violet, imbricate aestivation.

Androecium:

Stamens indefinite, polyandrous, arranged spirally in 3 whorls of 5 stamens each alternating with the petals. Filaments are flattened, anthers basifixed.

Gynoecium:

Monocarpellary, unilocular, ovary superior, marginal placentation, pubescent, stigma simple.

Floral formula: