4 TORREYA 



vegetative spores are produced by both generations, those produced by the 

 haploid generation producing haploid plants and those produced by the diploid 

 generation producing diploid plants. 



Of an entirely different nature are those cells (meiospores) produced by 

 vascular and non-vascular plants as a result of meiosis. These are not vegeta- 

 tively produced ; they are produced only by organisms having sexual reproduc- 

 tion and their production represents a continuation of the sexual process. They 

 do not produce the generation from which they originated but having been 

 formed as a result of a reproductive process in a diploid generation, the product 

 of their growth is a haploid generation. In some cases (diatoms, Siphonales) 

 they may be the only haploid cells ; they are, functionally, gametes. They are 

 fundamentally different from vegetative spores (zoospores, aplanospores, etc.) ; 

 in no sense are the two kinds of so-called spores homologous. How then can 

 the term asexual reproduction be used to refer to reproduction by these en- 

 tirely different methods? 



That it is so used is evident from the treatments in most of the numerous 

 current textbooks covering the field of Elementary Botany. In almost all of 

 these that the author has examined, no clear distinction is made between the 

 actual nature of vegetative spores and meiospores. The production of both and 

 the initiation of a new individual by their growth is generally included under 

 the term asexual reproduction. These two kinds of reproductive structures, 

 one strictly vegetative and the other associated with sexual reproduction are 

 homologized either directly or by inference. In most cases the gametophyte is 

 described as a sexual generation because it produces gametes and the sporo- 

 phyte as an asexual generation because it produces spores and the same termi- 

 nology is used to describe vegetative spores and meiospores. In one of the more 

 recent texts (Smith et al., 1942), the term asexual reproduction is entirely 

 eliminated but even here the reader is led to infer that the spores produced by 

 meiosis are in the same category as the vegetatively-produced spores of green 

 algae, since no effort is made to distinguish between them. 



Although the author has not attempted to be exhaustive in his review of 

 the numerous current elementary textbooks, a majority of those published in 

 the United States have been examined. In only three of these is sexual repro- 

 duction used in the sense of referring to the complete reproductive life cycle. 

 In the relatively brief and elementary textbook by Chamberlain ( 1930) "gamet- 

 ic reproduction" is considered as including the complete reproductive pro- 

 cess, consisting of the fusion of gametes and the consequent production of the 

 original plant by meiospores (Fig. 147). Even here, however, the same term, 

 zoospore, is used to denote both vegetatively produced spores and meiospores 

 so that confusion between the fundamentally different reproductive processes 

 by which they are produced is made easy in the mind of the student. 



