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THE AMERICAN NATURALIST. [Vol. XXXVII. 



In none of the species studied is there the slightest tendency 

 shown to develop anything resembling the spores borne upon 

 the sporophyte. It is true that some leafy liverworts develop 

 single-celled gemmae from the leaf-margins, and multicellular 

 gemmae are formed in various species ; but these are not in any 

 way associated with lack of water, nor are they in the least like 



It is interesting to find that the gametophyte of some ferns 

 has also developed the power of resisting drought. In California 

 it is not uncommon to find large prothallia of Gymnogramme 

 triangularis which have survived the summer, and the sporo- 

 phyte of this fern, as well as that of various xerophilous species 

 of Selaginella, can absorb water through the leaves, very much 

 as is done by the leaves of mosses and liverworts. Goebel 1 has 

 called attention to the behavior of G. leptophylla, where the 

 gametophyte is perennial, and may develop tubers much like 

 those found in the thallose liverworts. In this species the 

 sporophyte is annual. 



The point which I wish to emphasize is this : that whereas 

 there are many cases where the gametophyte is subjected to the 

 conditions which according to Mr. Lang's hypothesis should 

 induce spore-formation, in no cases observed has this been the 

 result, but the devices for surviving drought have been of a very 

 different nature. 



Dr. Coulter 2 thinks that the determining factor in the devel- 

 opment of the leafy sporophyte has been photosynthesis or 

 "chlorophyll-work." He sees no reason why such a structure 

 as the leafy sporophyte may not have arisen non-sexually in 

 response to the need for chlorophyll activity, and quite apart 

 from the production of any form of reproductive bodies. 



In support of this view he instances the development of the 

 gametophoric branches in Marchantia, and the leafy game- 

 tophoric shoots of the true mosses. It is-hardly likely that Dr. 

 Coulter would derive the latter from the former, although such 

 might possibly be inferred from his statement. The accuracy of 

 his statement that " the erect structure laid hold of the game- 



