Sexual Immobility as a Cause of the Development of the Sporophyte

Abstract

JN the Annals of Botany, August, i890, are to be found two very interesting papers on the alternation of generations in plants. One is by Professor F. 0. Bowers, who defends Alakovsky's distinction between antithetic and homologous alternation; the other by the late J. Reynolds Vaizey, who shows the impossibility of establishing homologies between sporophores and o6phores. Each of these papers presents somewhat more clearly than usual the problems which underlie all attempts at a general coordination of vascular plants, mosses, and the lower algae, 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 Archegoniatxe and the so-called sporophytic plants of Vaucheria, Mucor, or CEdogonium. These latter he conceives to be modified o6phytes,-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 Archegoniatae he ascribes change of habit from aqueous to subaerial 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 only in the Archegoniat.e, but wherever sporophytes are developed at all. In the first place, it should not be overlooked that in animals higher than the Medusae and Flat Worms (with rare exceptions, e.g., Salpa ?) ' there is nothing comparable with the alternation of