FERNS. 



271 



the plant is the prominent one, and that which characterizes the plant. It 

 also leads an independent existence, and, with the exception of a few cases, 

 does not die after the development of the spores, but lives from year to year 

 and develops successive crops of spores. There is a distinct advance here in 

 the size, complexity, and permanency of this phase of the plant. 



562. On the other hand the sexual phase of the ferns (gametophyte), while 

 it still is capable of leading an independent existence, is short-lived (with very 

 few exceptions). It is also much smaller than most of the liverworts and 



Fig- 313. 



Embryo of fern (Adiantum concinnum) still surrounded by the archegonium, which has 

 grown in size, forming the " calyptra." L, leaf ; S, stem ; R, root ; F, foot. 



mosses, especially as compared with the size of the spore-bearing phase. 

 The gametophyte phase or stage of the plants, then, is decreasing in size and 

 durance as the sporophyte stage is increasing. We shall be interested to see 

 if this holds good of the fern allies, that is of the plants which belong to the 

 same group as the ferns. And as we come later to take up the study of the 

 higher plants we must bear in mind to carry on this comparison, and see if 

 this progression on the one hand of the sporophyte continues, and if the 

 retrogression of the gametophyte c "tinues also. 



