10 TORREYA 



tion-division became associated with spore-formation — ." He then refers to the 

 "relegation of the reduction-division to the time of spore formation." Herein 

 is expressed a fallacy to which we readily fall heir when the alternating game- 

 tophytic and sporophytic generations are considered as being respectively sex- 

 ual and asexual ; a fallacy which is inherent in any theory of the homologous 

 origin of the alternating generations. This line of reasoning directly and pur- 

 posefully homologizes meiospores, which are always and only produced during 

 the series of processes involved in sexual reproduction, with the vegetatively 

 produced spores of algae. It postulates an origin of the meiotic processes in 

 connection with the vegetative production of spores rather than confining it 

 to the only conceivable place in which it could possibly have a function, namely, 

 as a result of the process in which the chromosome number is doubled. Meio- 

 spores can have no homologous identity with vegetative spores. The latter are 

 considered by many to< be homologous with gametes, since the usual theory 

 of the origin of sexual reproduction considers that gametes are modified vege- 

 tative spores. It is altogether logical that the cells produced as a result of the 

 meiotic processes following sexual fusion in various primitive plants should 

 simulate in appearance the vegetative spores produced by that particular plant, 

 since new genes for the production of somatic characters would not necessarily 

 be produced at the same time that sexual reproduction had its origin. But to 

 consider these cells as being homologous in origin would be comparable to con- 

 sidering as homologous the leaves of mosses and of lycopods, or root hairs of 

 vascular plants and rhizoids of fern prothallia. From the viewpoint of the pres- 

 ent paper, therefore, the alternating generations in a sexual life cycle such as 

 occur in all plants above the Thallophyta, and in many Thallophyta, could not 

 be considered as having had a homologous origin. 



This paper has thus far attempted to show that the usual textbook pre- 

 sentation of the "asexual" nature of the sporophyte should be corrected in 

 favor of considering the alternating generations in the life cycle of plants as 

 parts of the sexual life cycle. Although both viewpoints are to be found in 

 current texts, the former has the weight of numbers and the sanction of long 

 continued usage. Of even greater uniformity both from the standpoint of 

 unanimity of presentation and of admitted incorrectness is that part of most 

 botanical texts which serves, or should serve, the dual purposes of presenting 

 the groups of plants in an orderly sequence and of indicating the supposed 

 relationships between the groups, — the system of classification. The time-hon- 

 ored system of Thallophyta, Bryophyta, Pteridophyta and Spermatophyta 

 serves the first of these purposes but lacks woefully in serving the second, es- 

 pecially as between the groups included in the last two divisions. It has been 

 expressed as a truism that no morphologist considers the ferns, lycopods and 

 horsetails closely related. Yet, in the great majority of elementary texts the 

 lycopods and horsetails are "the allies of the ferns." The fact that this system 



