350 The American Naturalist. [May, 



is larger than the oospore, breaks the enclosing wall, and the 

 cells escape as a number of zoospores in place of one. But in 

 this oospore are the stored products of carbon assimilation of 

 the parent chlorophyll phase of the plant, and this case only 

 differs from that of the Bryophyta, in that the sporophyte be- 

 comes separated, with stored products, from the gametophyte, 

 before the differentiation of the spores. 



In the higher plants many cases of bulbs, corms, tubers, etc., 

 might be cited to show that the development of the sporophylls, 

 and even fruit, might take place without the accompaniment 

 of chylorophyll bearing organs. But here also the bulbs, 

 corms, etc., represent, in the stored products of carbon assimila- 

 tion, the preceeding green leaves. In certain ferns, as Osmunda 

 cinnamomea, the sporophyll, which is completely differentiated 

 from the vegetative leaf, appears first in the spring, and could 

 mature its spores without the aid of the vegetative leaves of 

 that season, but the green leaves of the previous season formed 

 the necessary carbohydrates, which are stored in the rhizome 

 and rudimentary leaves during the winter and in fact the spo- 

 rophylls and sporangia are partly developed at the close of 

 the previous season. 



We might say, then, that in general, all spore production in 

 plants, which themselves assimilate carbon dioxide, is neces- 

 sarily preceeded by a greater or lesser development of chloro- 

 phyll bearing organs. This may appear to be a too well known 

 axiom for even the brief discussion here given, but it is neces- 

 sary in view of what is to come to have this axiom well in 

 mind. Chlorophyll bearing organs, or tissues, then, as com- 

 pared with sporogenous organs or tissues, are, in point of time 

 within the life cyle, primary, while the latter are secondary. This 

 proposition should not be regarded as opposed to the primary 

 evolution of the sporophylls as compared with the foliar organs 

 of the sporophyte. It applies only to a comparatively limited 

 extent of time; to the usual cycle between the vegetative 

 and fruiting phases ; to the ontogenetic, not to the phylogene- 

 tic, development. It applies with equal force to plants in 

 which either the gametophyte or the sporophyte forms the 

 chlorophyll bearing organ. 



