Question

What are different types of inflorescence seen in Euphorbiaceae? Give example for each.

Answer 1

Inflorescence: Type # 1. Racemose Inflorescence:

In this type of inflorescence the main axis does not end in a flower, but it grows continuously and develops flowers on its lateral sides in acropetal succession (i.e., the lower or outer flowers are older than the upper or inner ones). The various forms of racemose inflorescence may be described under three heads..

The individual flowers (florets) are bracteate. In addition the whole inflorescence remains surrounded by a series of bracts arranged in two or three whorls.

The capitulum inflorescence has been considered to be the most perfect. The reasons are as follows:

The individual flowers are quite small and massed together in heads, and therefore, they add to greater conspicuousness to attract the insects and flies for pollination.

At the same time there is a considerable saving of material in the construction of the corolla and other floral parts.

A single insect may pollinate flowers in a short time without flying from one flower to another.

Inflorescence: Type # 2. Cymose Inflorescence:

In this type of inflorescence the growth of the main axis is ceased by the development of a flower at its apex, and the lateral axis which develops the terminal flower also culminates in a flower and its growth is also ceased. The flowers may be pedicellate (stalked) or sessile (without stalk).

Here the flowers develop in basipetal succession, i.e., the terminal flower is the oldest and the lateral ones younger. This type of opening of flowers is known as centrifugal

(i) Uniparous or Monochasial Cyme:

Here the main axis ends in a flower and it produces only one lateral branch at a time ending in a flower. The lateral and succeeding branches again produce 

Inflorescence: Type # 3 Cyathium:

This type of inflorescence is found in genus Euphorbia of family Euphorbiaceae; also found in genus Pedilanthus of the family. In this inflorescence there is a cup-shaped involucre, often provided with nectar secreting glands. The involucre encloses a single female flower, represented by a pistil, in the centre, situated on a long stalk.

This female flower remains surrounded by a number of male flowers arranged centrifugally. Each male flower is reduced to a solitary stalked stamen. It is evident that each stamen is a single male flower from the facts that it is articulated to a stalk and that it possesses a scaly bract at the base. The examples can be seen in poinsettia (Euphorbia), Pedilanthus, etc.

Inflorescence: Type # 4. Verticillaster:

This type of inflorescence is a condensed form of dichasial (biparous) cyme with a cluster of sessile or sub-sessile flowers in the axil of a leaf, forming a false whorl of flowers at the node. The first of main floral axis gives rise to two lateral branches and these branches and the succeeding branches bear only one branch each on alternate sides.

The type of inflorescence is characteristic of Lamiaceae (Labiatae) family. Typical examples, are—Ocimum, Coleus, Mentha, Leucas, etc.