MOSSES 



351 



high up on the stem. Numerous leafy stems arise from the 

 protonema, thus making dense tufts. The protonema usually 

 disappears soon after the moss stems arise.* Certain species of 

 the mosses often multiply by branching, by the growth of new 



Funaria hygrometrica. A, germinating spore; v, vacuole; w, rhizoid; s, exosporium. B, 

 portion of a developed protonema, about three weeks after germination; A, a prostrate 

 primary shoot with brown wall and obliquely transverse septa, from which proceed the 

 ascending branches with limited growth; at K the rudiment of a leafy axis with rhizoid W. 

 (After Sachs.) 



protonemes from the moss plant, and sometimes by bulbils f or 

 by brood buds. After the development of the sexual organs, 

 fertilization is brought about by the sperm passing down the 

 canal of the egg case, and fusing with the nucleus of the egg. 

 The fertilized egg then divides and elongates downward to form 

 a foot, which wedges its way into the upper end of the moss stem, 

 while the upper part elongates upward to form the stalk and 

 capsule. At the same time the egg case enlarges to form a pro- 



* In one genus, Pogonatum, the protonema exists for a long time, even 

 until the fruit of the moss appears. Here the protonema is more con- 

 spicuous than the moss plant and covers extensive patches of the ground 

 along the roadside in woods. The protonema in a few of the higher mosses 

 is partly thallose, as in Tetraphis. 



f In the mosses these " bulbils " are small, rounded masses of cells 



