The Origin of Land Plants 95 



are also present in many of the true mosses, ex- 

 tremely specialized structures associated with the 

 opening of the sporogonium and the scattering of 

 the spores. These very highly differentiated struc- 

 tures indicate that the true mosses constitute a 

 very specialized class with little direct affinity with 

 any other plants. They may be said to bear some- 

 what the same relation to the relatively primitive 

 liverworts that red and brown seaweeds do to the 

 more primitive green algae. 



Anthocerotes. There is one family of liverworts, 

 now usually considered to represent a distinct class, 

 which is especially important in the study of the 

 evolution of the sporophyte. These are the horned 

 liverworts (Anthocerotes), which in the character 

 of their sporophyte approach more nearly the con- 

 dition found in the ferns than is the case with any 

 other bryophyte. The gametophyte of these An- 

 thocerotes is very simple in structure, and in the 

 character of the cell which contains only a single 

 chloroplast they resemble the green algae more 

 nearly than do any other liverworts. 



Sporophyte of Anthoceros. It is the sporophyte, 

 however, with which we are here especially con- 

 cerned. In its most highly developed form, i.e., 

 Anthoceros (Fig. 10, C), it shows a remarkable 

 power of growth. There is developed a basal zone 

 of growing tissue, which keeps adding to the size of 

 the sporophyte so that sometimes it may reach the 

 length of ten centimeters or more. To support this 



