112 OUTLINES OF EVOLUTIONARY BIOLOGY 



the embryo sporophyte into the ovule of the preceding sporo- 

 phyte generation, with the gametophyte crushed in between 

 is the most characteristic feature of the life cycle of the higher 

 plants. 



From the homosporous ferns upwards throughout the vegetable 

 series it is obvious that the gametophyte is not nearly so well 

 adapted in its organization to the conditions under which the 

 higher plants have to live as is the sporophyte. There has 

 apparently been a kind of rivalry between the two alternating 

 generations, in which the gametophyte has had much the worst 

 of it. The sexual function itself, however, is far too important 

 to be altogether abandoned, and so the successful sporophyte has 

 finally taken over many of the responsibilities connected there- 

 with, while the poverty-stricken gametophyte has ultimately 

 become entirely parasitic upon its rival. 



