Features of Equisetum (With Diagram)

In this article we will discuss about the external features of equisetum.

1. Plant body is sporophytic and the sporophyte is a well-branched perennial herb.

2. Size of the plant body ranges from a few centimeters as in Equisetum scirpoides to several metres as in E. giganteum (up to 13 metres). Most of the species are less than a meter in height.

3. Plant body consists of a long, horizontal, underground rhizome, from which arise many roots towards the lower side and many erect aerial shoots towards upper side (Figs. 235, 236).

4. Rhizome is long, creeping and well-branched. It is divisible into nodes and internodes.

5. Roots, which develop from the node of rhizome, are long, slender, well-branched and adventitious.

6. Aerial shoots, which arise from the rhizome towards upper side, are of two types, i.e., sterile or vegetative shoots and fertile or reproductive shoots.

7. Both the sterile and fertile aerial shoots are ribbed and divisible into nodes and internodes, but the former is well-branched and long-lived while the latter (fertile shoots) are generally unbranched and short-lived structures.

8. Aerial shoots as well as rhizome are articulated (i.e., jointed).

9. From the nodes of aerial sterile shoots arise two types of branches in whorls. Some are long, unlimited in growth, well-branched and contain the same structure as the main axis of aerial sterile shoot. Others are short, also bear nodes and inter- nodes but are limited in growth and unbranched (Figs. 235,236).

10. Fertile shoots are unbranched, colourless or pale- yellow coloured branches, each of which bears a strobilus at the tip.

11. On the nodes of rhizome, sterile shoot and fertile shoots are present many scaly leaves.

12. Scaly leaves are minute, thin, uninerved, present in the form of a whorl and vary in number from 3 to 40 in different species.

13. These leaves are green when young but become yellow or red-coloured at maturity.

14. The upper end of each leaf is free and pointed but all of them unite below at the base to form a sheath on the node.

15. The number of leaves represents the number of ridges on the internode.

16. Many round or irregular bodies are present on the rhizome. These are thick-walled and meant for vegetative reproduction. These are called tubers (Fig. 235).

17. Functions of various parts of the sporophyte are as follows:

(a) Roots – Absorption and fixation;

(b) Rhizome – Storage;

(c) Sterile shoots – Photosynthetic;

(d) Fertile shoot – Reproductive.

Thus, Equisetum shows an example of physiological division of labour.