22 The American Naturalist. (January, 
SEXUAL IMMOBILITY AS A CAUSE OF THE 
DEVELOPMENT OF THE SPOROPHYTE. 
BY CONWAY MACMILLAN, 
es the Annals of Botany, August, 1890, are to be found two 
very interesting papers on the alternation of generations in 
plants. One is by Professor F. O. Bowers, who defends Ala- 
kovsky’s distinction between antithetic and homologous alterna- 
tion; the other by the late J. Reynolds Vaizey, who shows the 
impossibility of establishing homologies between sporophores and 
odphores. Each of these papers presents somewhat more clearly 
than usual the problems which underlie all attempts at a general 
codrdination of vascular plants, mosses, and the lower algz, and 
in each of them there is some effort to account for the origin of 
the phenomenon of alternation itself. Bowers is inclined to 
ascribe entirely different causes to the sporophyte of the Arche- 
goniate and the so-called sporophytic plants of Vaucheria, Mucor, 
or CEdogonium. These latter he conceives to be modified 
odphytes,—or gametophytes, to use his terminology,—while the 
former is an interpolated plant, altogether devoid of homologies 
with the gametophyte of its own species or that of any other. 
To the sporophyte of the Archegoniate he ascribes change of 
habit from aqueous to subaérial nutritive media as the producing 
cause, and proceeds to adduce morphological and phylogenetical 
evidence in support of the position. The purpose of this brief 
note is to indicate an opinion of the writer that something quite 
different, and not altogether overlooked by Bowers, is possibly 
the sufficient cause for the development of sporophytes, not 
wads in the Archegoniate, but wherever sporophytes are developed 
at 
In the first place, it should not be overlooked that in animals 
higher than the Medusz and Flat Worms (with rare exceptions, 
e.g., Salpa?)' there is nothing comparable with the alternation of 
1 The alternation in plant-lice (Aphidze) is a different matter entirely, and need not be 
considered here 
