No. 438.] ORIGIN OF THE SPOROPHYTE 



4J5 



preparatory to the formation there of the characteristic group of 

 four spores. 



It will thus be seen that there can be no genetic relationship 

 between the reduction phenomena of higher plants and animals. 

 They are not found at the same points in the life history and 

 there are also fundamental differences in the details of the pro- 

 cess that cannot be considered here. 



With these points understood the sporophyte generation takes 

 on new interest in relation to sexual processes in plants for it 

 appears to be a development peculiar to this group of organisms 

 and probably related to a form of sexuality that differs from 

 that of animals in important respects. These differences con- 

 cern the maturation of the gametes which in animals takes place 

 with a very characteristic process of chromosome reduction 

 and in plants without this phenomenon. 



So little is known about the origin of sex in animals that sat- 

 isfactory comparison with the much better understood history 

 for plants, is not possible. We have already discussed that topic 1 

 and also sexual evolution. 12 



As there is no reduction phenomena in plants at the time 

 when sexual cells are formed perhaps we find in this fact a clue 

 to the reason of the sporophyte generation and its origin. It 

 must be clear that the most promising line of investigation 

 would deal with the doubling of the chromosomes at the sexual 

 act and the later reduction to the gametophyte number at the 

 end of the sporophyte generation. 



The final explanation of the problems can only come through 

 the study of plants below the Bryophytes, that is among the 

 Thallophytes, and we have had as yet very little detailed research 

 on this point. So this paper must deal largely with speculations. 

 We know positively the main facts of sexual processes and chro- 

 mosome reduction in groups above the Thallophytes but for this 

 group almost nothing. 



Nevertheless, we are justified in considering an hypothesis of 



