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Flower

Flower is a modified shoot meant for reproduction. It arises as a bud in the axil of a specialized leaf called bract.

A flower consists of a short stalk or pedicel which is swollen and convex at the upper end known as thala­mus. On the thalamus are inserted floral leaves in four whorls:

1. Calyx:

It is the outermost and lowermost whorl of green leaves called sepals. They protect the flower in the bud condition.

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2. Corolla:

It is the inner whorl of coloured floral leaves called petals. Because of the varied colours, this whorl attracts insects which bring about pollination.

3. Androecium:

This is the third whorl of floral parts and is called the stamen. It serves as the male reproductive organ and contains male gametes called pollen grains.

4. Gynoecium:

It is the innermost whorl of floral parts called carpels and serves as the female reproductive organ which bears female gametes called ovules.

Inflorescence:

The specialized branches which bear clusters of flowers are called inflorescences. The main axis of an inflorescence bearing a group of flowers is called rachis or peduncle. Inflorescence may be of two types:

1. Racemose:

In this type, the main axis of the inflorescence (rachis) grows indefinitely giving rise to younger and younger flowers in an acropetal order. The rachis never terminates in a flower, the apex being left for further growth.

2. Cymose:

The growth of the cymose inflores­cence is always checked vertically. In cymose, the apical bud is the oldest and younger flow­ers occur below it. Opening of flowers is basipetal (towards the base). Cymose inflores­cences are less common than racemose types.

Special Inflorescences

(i) Hypanthodium:

It is a closed capitulum in which receptacle becomes fleshy, hollow, and cup-shaped and opens at the top by a narrow opening, e.g., Ficus (Fig) and Banyan.

(ii) Cyathium:

It consists of a cup-shaped in­volucre formed by the fusion of bracts. In­side involucre are found unisexual flowers, e.g., Euphorbia (Dandathor).

(iii) Veriicillater:

This is a complex inflores­cence. There are two opposite leaves in these plants and one inflorescence develops from each of the two opposite axils, e.g. Ocimum (Tulsi) and Salvia.