In this article we will discuss about the structure of Funaria with the help of a diagram.
External Features of Funaria:
The erect gametophytic plant (Fig. 6.47A) is about an inch high with an erect leafy axis or stem attached to the substratum by rhizoids. The axis is radial, often branched axillary or extra-axillary. The axis is covered with spirally arranged leaves which are more crowded near the apex forming a rosette.
Actually eight leaves are arranged in three complete spirals forming 3/8 phyllotaxy corresponding to the three cutting faces when young. The leaves are simple, sessile, ovate, with pointed apex, smoothed margin, attached to the stem by a broad base (Fig. &.47B). The mature leaves have midribs but younger leaves are devoid of midribs.
The rhizoids are strong, mu h-branched multicellular (Fig. 6.48B). They are characterised by the presence of oblique septa. Young rhizoids are colourless but become brown of black when mature. The branches of rhizoids often produce chloroplasts when exposed to sunlight. They function as anchoring and “absorbing organs.
Internal Features of Funaria:
Stem:
The transverse section of the mature stem shows three distinct regions viz., the outer epidermis, middle cortex, and the inner central strand (Fig. 6.47C).
1. Epidermis:
It is the outermost layer of the stem. The epidermal cells contain chloroplasts and have no pores or stomata.
2. Cortex:
It is a multilayered zone between the epidermis and the central cylinder and consists of large parenchymatous cells. The cells of the cortex contain chloroplasts when young but they are lost when the stem matures.
All cortical cells of a young stem are alike, but as the stem matures the outer cells of the cortex become thick-walled and reddish-brown. The cortex also shows isolated patches of small cells in the peripheral region, representing the leaf traces. However, these traces have blind ends and do not join the central cylinder.
3. Central Cylinder:
It is composed of long, narrow, thin-walled colourless cells. These are dead cells and devoid of protoplasm, possibly help in the conduction of water and solutes.
Leaf:
A transverse section of the leaf shows a well defined central midrib and the one- celled thick lamina (Fig. 6.48A). The midrib has a small strand of slightly thickened narrow cells, probably help in conduction. Lamina cells are elongated, thin-walled and rich in chloroplasts. The leaves are devoid of stomata or hairs.