In this article we will discuss about:- 1. General Features of the Ranunculaceae 2. Floral Range in the Ranunculaceae 3. Divisions 4. Position and Affinity 5. Number and Distribution 6. Economic Aspects.
General Features of the Ranunculaceae:
Habit – Erect or climbing herbs or shrubs.
Leaves – Alternate or radical, simple or compound, often with a twisted sheathing base.
Inflorescence – Cymose or racemose.
Flowers – Bisexual, regular, acyclic or hemicyclic.
Calyx – Sepals 5, petaloid, imbricate.
Corolla – Petals 5 or more, sometimes spurred.
Androecium – Stamens many, free; anthers extrorse.
Gynoecium – Carpels many, free; ovary superior; ovules few to many.
Fruit – 1-seeded achene or many-seeded follicle.
Seed – Embryo small; endosperm oily.
Floral Range in the Ranunculaceae:
Deviations from the normal type of flower occur in the Ranunculaceae. The flowers are frequently regular, but irregular in Aconitum and Delphinium. Although the calyx and corolla may be generally found, petals are sometimes lacking (Nigella). The segments of the perianth are alike in Helleborus and differentiated into the calyx and corolla.
The perianth is followed by a varying number of honey leaves which are regarded as metamorphosed stamens or petals. In Helleborus, there are 13 rows of stamens and the first component of each row is transformed into a honey leaf; here the honey leaf is the progenitor of the stamens.
In Isopyrum, the honey leaves are in a whorl of 5 alternating with 5 sepals and hence may be regarded as definite petals. In Trollius, the first members of the staminal row become converted into small narrow honey leaves each of which has a short claw and a small flat blade at its base.
In Caltha, there is no separate nectary and honey is secreted by the carpels. In Eranthis, the nectary is absent and honey is secreted by the petals. Definite nectariferous bodies are not even seen in Paeonia, but a ring- or disc-like swelling of the receptacle developed at the base of the carpels takes over the function of the nectary.
As regards the number and arrangement of carpels, various types are encountered. Generally, the carpels are numerous, but 5-10 in Trollius, 5-12 in Nigella and 1 in Actaea. The carpels are free in many cases, but spiral in Myosurus and Ranunculus and somewhat united to form a compound ovary in Nigella. In Coptis, the carpels are often stalked.
Divisions of the Ranunculaceae:
The Ranunculaceae is divided into three tribes:
Tribe (i) Anemoneae:
Ovules solitary, arising from base of ventral suture. Examples: Anemone, Clematis, Myosurus, etc.
Tribe (ii) Helleboreae:
Ovules arranged in two rows along ventral suture of carpels. Fruit a berry or follicle. Examples: Aconitum, Caltha, etc.
Tribe (iii) Paeoniaeae:
Ovules arranged in two rows along ventral suture of carpels, but outer integument well developed. Example: Paeonia.
Position and Affinity of the Ranunculaceae:
The Ranunculaceae is usually accepted to be among the most primitive of the dicotyledons. Hutchinson as well as Bentham-Hooker placed the family in the class of early dicots. In Engler’s arrangement, the family appeared under the advanced Archichlamydeae. But Rendle and others relegated it to the early Dialypetalae.
The floral parts of the Ranunculaceae are similar in structure and arrangement to those of the Magnoliaceae, but the latter can be separated by the possession of woody habit and distinct stipules. Another relationship can be traced to the Cabomboideae (Nymphaeaceae), the items of common interest being the dimorphic leaves and small hypogynous flowers.
On the basis of the structure of essential whorls, such as stamens and carpels, the Ranunculaceae shows resemblance to the Papaveraceae; the latter is characterised by the presence of milky sap, dimerous calyx and syncarpous ovary. Though the family can be linked with the Rosaceae on account of tree and numerous stamens and carpels, the latter stands out prominent by virtue of the general perigynous flowers and cyclic arrangement of stamens.
An affinity with the Berberidaceae is indicated by the single carpel of Actaea, while the enormous development of the outer integument of the ovule is a characteristic feature of the Berberidaceae. “The Ranunculaceae and Berberidaceae are also phytochemically related in the possession of the alkaloid berberine”.
Number and Distribution of the Ranunculaceae:
The Ranunculaceae covers about 50 genera and over 1,800 species. The plants of this family grow largely in the temperate and Arctic regions.
Commonly Occurring Plants of the Ranunculaceae:
Monkshood (Aconitum napellus L.) and Larkspur (Delphinium ajacis L.) are garden plants.
Virgin’s Bower (Clematis gouriana Roxb. ex DC.) is a herbaceous plant which climbs by means of tendrillar petioles.
Coptis teeta Wall., a stemless herb, occurs in temperate regions of Arunachal.
Traveller’s Joy [Naravelia zeylanica (L.) DC] is a climber with alternate leaves, the terminal leaflet of which turned into a tendril.
Black Cumin or Fennel Flower (Nigella sativa L.) is raised by farmers for its seeds.
Indian Buttercup (Ranunculus scleratus L.) is an erect herb, thriving in marshes and river banks.
Meadow Rue (Thalictrum javanicum Bl.), found mainly in hilly spots, is a slender plant with decompound leaves.
Economic Aspects of the Ranunculaceae:
Economically, the Ranunculaceae is of domestic importance for the large number of ornamentals. Aconitum napellus and Delphinium ajacis are commonly cultivated as garden plants.
The plants of this family are rich in alkaloids which have medicinal uses. The notable examples are Anemone Pulsatilla, Cimicifuga racemosa, Delphinium staphisagria and Hydrastis canadensis.
The seeds of Nigella sativa are generally used as a condiment, but also employed as a preservative of woollen garments against the attacks of insects.
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