BRYOPHYTES 87 



loss of water by evaporation. Not only are the working 

 bodies protected, but the sexual-cells are jacketed, so that 

 the sex-organs (antheridium and archegonium) are many- 

 celled. ^ 



The most significant result of the land habit was the es- 

 tablishment of an alternation of generations, so that sporo- 

 phyte and gametophyte alternate regularly in the life-history. 

 Among Bryophytes the gametophyte is the conspicuous 

 generation, because it manufactures food in addition to pro- 

 ducing sex-organs, and the sporophyte is dependent upon it. 

 In one group of Bryophytes (Anthoceros) the sporophyte is 

 green, so that the possibility of an independent sporophyte is 

 evident. 



The further progress of the plant kingdom is dependent 

 upon an independent sporophyte, because the free display of 

 green tissue by a gametophyte means conditions unfavorable 

 for the swimming of sperms necessary to fertilization, while 

 the free display of green tissue by a sporophyte means con- 

 ditions favorable also for the dispersal of spores. 



