LECTURE XXXIX. 

 EVOLUTION OF THE HIGHER PLANTS. 



Pro/. Douglas PI. Campbell. 



Bryophytes (mosses and liverworts). Have prob- 

 ably been derived from the higher green algae. 



Mosses a sharply limited specialized group in con- 

 trast to the generalized class of the liverworts. The 

 latter show affinities on one hand to the algae, and on 

 the other to the ferns ; as well as having evident rela- 

 tionship to the mosses. 



Bryophytes show a well-marked alternation of a 

 sexual phase (gametophyte), and non-sexual stage 

 (sporophyte). 



In lower forms the sporophyte is insignificant, and 

 entirely devoted to spore formation ; in the highest 

 (anthoceros) the formation of spores is less important, 

 and the sporophyte has a well developed assimilative 

 system of tissues. 



Anthoceros leads directly to the pteridophytes (fern- 

 like plants) in which the sporophyte develops roots 

 and becomes an independent plant. Ophioglossum 

 among living seem to come nearest to anthoceros. 



In pteridophytes the germinating spore gives rise to 

 gametophyte (prothallium), which becomes more and 

 more reduced from the long-lived liverwort-like game- 

 tophyte of the lower homosporous ferns to the rudi- 

 mentary gametophyte of the heterosporous forms. In 



