THE BRYOPHYTA 131 



the leaf, but dies out in the cortex without reaching the 

 central cylinder. Consequently there is no complete 

 leaf-trace system in this Moss, though some of the more 

 complicated Mosses (such as Atrichum) have continuous 

 strands connecting the conducting tissue of the stem with 

 that of the leaves. We must remember that the whole 

 mode of life of a Moss plant, especially as regards its water- 

 supply, is very different from that of the higher plants. 

 Many Mosses, and Funaria, among them, often grow in 

 places such as the tops of walls, or in sandy soil, where 

 they are liable to be completely dried up in hot weather. 

 Yet they are none the worse, and revive as soon as rain 

 comes again. This rapid recovery is due to their power 

 of absorbing water by their leaves a power which is 

 either absent or which only exists to an insignificant 

 extent in most of the higher plants. Hence less work 

 falls on the conducting tissues of the stem than in the 

 latter, for only a small part of the water-supply is taken 

 up from below, though this part of the supply is important 

 as it carries with it the necessary mineral food-substance. 

 As we have said, a Moss possesses no true root. 

 The functions of a root are performed by the rhizoids, 

 as they are called, multicellular root-hairs springing 

 from near the base of the stem (see Fig. 59, r). These 

 rhizoids are very different from ordinary root-hairs, 

 which are generally unicellular, though multicellular 

 rhizoids occur on the prothallus of some few Ferns. 

 The Moss rhizoids consist of a single chain of very 

 long cells separated from one another by oblique walls. 

 They grow entirely by means of the apical cell at the 

 free end of each filament, and branch repeatedly, the 

 diameter diminishing with the successive orders of 

 branching, so that the final ramifications are very 



