150 



PLANT-LIFE 



stances in the latter are rapidly exhausted ; the growing 

 sporophyte first develops a root, then a leaf, and soon 

 becomes quite independent of its parent. 



Seeing that the gametophyte of a Fern is dependent 

 upon water in the process of fertilization, it may be 

 safely termed " amphibious "; to a certain extent it is 

 a creature of the water, but to a greater extent it is a 



FIG. 46 RIPE ANTHERIDIUM 

 OP MALE FERN. SPERMATO- 



ZOIDS ESCAPING. X 350. 



FIG. 47. ARCHEGONIUM OF MALE FERN 

 PREPARED FOR FERTILIZATION. X 350. 



p, Cells of prothallus; n, neck; m, mucil- 

 age extruded from canal; o, ovum. 



creature of the land. This particular water requirement 

 of a Fern indicates the aquatic ancestry of these land 

 plants, and the prothallus represents a stage through 

 which the Ferns have passed in the course of their evolu- 

 tion. The sporophyte, the Fern-plant, so soon indepen- 

 dent of the gametophyte, is a remarkable demonstra- 



