THE AMERICAN NATURALIST. [Vol. XXXVII. 



it in the embryo, at least of the lower types, but nothing which 

 can be so interpreted is ever found, unless we might consider 

 the suspensor of the Lycopods as of this nature, which probably 

 no morphologist would be likely to do. 



The statement that it is no more difficult to imagine the 

 gametophyte producing spores, than the spore giving rise to the 

 gametophyte, can hardly be admitted. The spores of all Arche- 

 goniates, if we assume the antithetic theory of alternation, are 

 the direct descendants of those produced by the germinating 

 zygote in the ancestral forms, which on germination give rise to 

 the gametophyte. This is perfectly demonstrable, while any- 

 thing like the production of spores, at least of the type produced 

 by the sporophyte, is absolutely unknown in any gametophytic 

 structure. The supposed cases of the production of sporangia 

 upon the gametophyte have been shown to be merely a greatly 

 reduced case of apogamy. 



Of course, if we should admit that the sporophyte originated 

 apogamously in the first place, it would follow that foliage leaves 

 are older than sporophylls, and that Pteridophytes and Bryoph- 

 ytes have nothing to do with each other ; but the weight of evi- 

 dence is very much against such a supposition. 



That chlorophyll-work has been a very potent factor in the 

 evolution of the plant-body is of course beyond dispute; but its 

 bearing upon the origin of terrestrial plants is not so clear. All 

 green plants, whether aquatic or terrestrial, must make provision 

 for photosynthesis, and we find the arrangements for the most 

 favorable display of green tissue developed in various ways. 

 Leaves are by no means confined to land-plants, many Algae, 

 especially the larger Phaeophyceae, having foliar organs which, 

 although simple in structure, are often of great size, and effi- 

 cient organs for photosynthesis. There is abundant evidence, 

 also, that leaves have been developed -more than once among the 



the thallus of all the Marchantiacea? is greater than that in the 

 gametophores. It may also be questioned, moreover, whether 



