CHAPTER XVI 



THE PLANT WORLD CONTINUED 



THE THREE HIGHER GROUPINGS 

 BRYOPHYTES 



BRYOPHYTES are usually said to possess archegonia ( ), 



or primitive egg gonads, composed of many cells, as contradistin- 

 guished from the thallophytes which, when they possess gonads 

 at all, are practically always composed of single cells. 



Bryophytes are moss plants and liverworts, and their life cycle con- 

 sists of two stages, the sexual and the sexless. When these stages follow 

 each other, an "alternation of generations" occurs. The sexual plant, 

 or gametophyte, forms eggs and sperm which unite, while the asexual 

 plant or sporophyte is the plant which grows from the fertilized egg of 

 the sexual plant. This nonsexual plant forms asexual spores which, in 

 turn, grow into gametophytes. 



Bryophytes may be quite simple, resembling the thallophytes, or 

 they may form a leafy stem as in the mosses. 



There are some 12,000 different species of mosses or Musci, as they 

 are technically known. These are divided into three distinct orders : 



1. Sphagnales ( ). The peat mosses. (Fig. 



107.) 





Fig. 107. 

 The Peat Moss, 



Sphagnum. 



Fig. 108. Audreaea Petrophila. 

 A, plant with mature sporophyte. 

 B, longitudinal section of sporophyte. 

 Ps, pseudopociium; col., columella. 

 (From D. H. Campbell's "A University 

 Text-Book of Botany," by permission of 

 The Macmillan Co., Publishers.) 



