200 



BOTANY 



The germinating spores produce in turn the gametophyte. The 

 latter, in abnormal cases, may arise as a direct outgrowth of the 

 sporophyte (Apospory), and conversely the sporophyte may develop 

 as a vegetative growth from the gametophyte (Apogamy). 



THE MUSCINE^E (BRYOPHYTA) 



The Archegoniates fall into two series of equal rank, the Bryo- 

 phytes or Mosses in a wider sense, and the Pteridophytes or Ferns 



and their allies. 

 In the former 

 group, the gameto- 

 phyte is the pre- 

 dominant phase ; 

 in the latter, the 

 sporophyte, which 

 becomes an in- 

 dependent, long- 

 lived plant. 



The Bryophytes 

 are usually di- 

 vided into two 

 classes, Liver- 

 worts (Hepaticse) 

 and Mosses (Mus- 

 ci). It seems 

 best, however, to 

 add a third class, 

 Anthocerotales, to 

 include certain 

 forms which have 

 hitherto usually 

 been united with 

 the Liverworts. The Anthocerotales are, to some extent, inter- 

 mediate in character between Bryophytes and Pteridophytes. 



Gametophyte. The gametophyte in the Bryophytes may be a 

 delicate thallus, not essentially different from that of some Algae, or 

 it may be highly differentiated, showing well-developed stem and 

 leaves, as is seen in the higher Mosses. These structures differ, 

 however, from the similar parts of the sporophyte of the vascular 

 plants (Ferns and Seed-plants). 



The Sporophyte. The simplest sporophyte is that of Riccia, which 

 consists of a globular body, all of whose cells, except a single super- 

 ficial layer, produce spores. In all other Bryophytes a greater or 

 smaller part of the sporophytic tissue is sterile, and is connected with 



Fio. 161. Riccia trichocarpa. A, sporogenous cell under- 

 going the first nuclear division (X 600). B, section of 

 young spore-tetrad (X 300). C, section of a ripe spore. 

 D, surface view of the epispore. 



