THE ARCHEGONIAT^E 



223 



At maturity the sporophyte splits into two valves, and the spores 

 are gradually thrown out as they mature. Owing to the formation 

 of new sporogenous tissue at the base of the sporophyte, spores in 

 all stages of development occur in the same individual. 



FIG. 185. Anthoceros Pearsoni. Development of the embryo (X300). A, C, I,, 

 median longitudinal sections. B, D, successive crt>ss-sections of embryos of about 

 the age of A, C. E, older embryo, showing the archesporium. 



CLASS III. Musci 



The true Mosses (Musci) are much more abundant than the Hepat- 

 icse, especially in colder regions, where they often constitute an 

 important feature of the vegetation. While the number of species 

 is much greater than that of the Liverworts, the general type is a 

 very uniform one, and were it not for the peculiar genera, Sphagnum 

 and Andresea, they might all be reduced to a single order. 



The Gametophyte 



Protonema. The gametophyte of the Musci always shows a pre- 

 liminary stage, the protonema, which is usually an extensively branch- 

 ing growth, resembling an Alga, or, less commonly, is a flat thallus 



