63 



No special non -sexual reproductive organs occur in 

 these plants, beyond the separation of small fragments, 

 usually nodes, which may, under proper conditions, de- 

 velop into new individuals. 



The sexual organs, antheridia and oogonia, are ex- 

 tremely complicated, especially the former, and differ 

 very much from those of all other algse. They show 

 certain analogies with the reproductive organs of some 

 of the lower mosses, this being especially the case with 

 regard to the spermatozoids, which are strikingly similar 

 to those of some mosses. A single large spore results from 

 the fertilization of the egg-cell, which is surrounded by a 

 protective covering formed by a series of cells about it. 



The spore on germination produces a simple conferva- 

 like filament, or " protonema," upon which the fully de- 

 veloped plant arises as a lateral branch. As this is 

 somewhat like the formation of the leafy stems in the 

 common mosses, it has been suggested that there may 

 be some genetic connection between the latter and the 

 Characese ; but this is highly improbable in view of the 

 great differences in the structure of the plants of the two 

 groups, although the analogies in the structure of the re- 

 productive organs may indicate a remote relationship be- 

 tween them. 



THE BROWN AND RED ALG.E 



While the green algse are for the most part inhabi- 

 tants of fresh water, the two other great groups of 

 Algse are mostly found only in the sea, where they con- 

 stitute the most conspicuous features of the marine 

 flora. Both classes include plants of much greater size 

 and complexity than any green algse, some of the great 



