The Lower Plants 69 



stimulated into active growth and gives rise either 

 directly or indirectly to a peculiar structure known 

 as the " Sporocarp," from which the spores are 

 ultimately developed. The development of the 

 sporocarp is too elaborate to be given here in detail, 

 but the resulting structure may be compared in a 

 way to the spore-bearing structure or " sporophyte," 

 which arises from the fertilized egg in the mosses 

 or ferns, although there is not the least evidence of 

 any relationship between the latter forms and the 

 red algae. In both groups, however, the product of 

 fertilization is a spore-bearing structure, which to 

 a greater or less degree is parasitic upon the plant 

 which bears the sexual organs, and there is a more 

 or less well-marked " alternation of generations." 



Summary: The Fresh-water Algae More Primi- 

 tive than the Seaweeds A survey of the Algae as 

 a whole indicates that the main line of develop- 

 ment in the direction of the higher plants is through 

 the green algae, which give evidence of being a much 

 more primitive group than either the brown or red 

 algae. There is a fairly complete series of 

 forms leading from the free-swimming Volvocales, 

 through non-motile unicellular forms, to simple 

 filamentous or thallose green algae, which in their 

 turn lead toward the lowest of the land 

 plants, the simpler mosses. From this main line 

 there probably diverged several secondary de- 

 velopmental lines such as the Siphoneae and 

 Charales. The two other classes, the brown and 



