144 ' Sex Segregation in the Bnjophyta 



spores of any moss capsule of a monoicous species produce monoicous 

 gametophytes. The further assumption, that maleness is recessive, 

 would mean the extinction of the monoicous habit. 



Again in dioicous species it is generally agreed that the spores of 

 any single capsule develop to give rise to either J^ or ? axes, but the 

 theory would lead us to assume, as with monoicous forms, the existence 

 of certain capsules, all the spores of which produce male axes exclusively, 

 and others whose spores produce monoicous axes in which maleness is 

 latent. 



Although the experiments upon which El. and Em. Marchal based 

 the theory of sex segregation have not been repeated, the theory has 

 been subjected to considerable criticism. Recently M. Wilson^ found 

 organs of mixed sex together with normal sex organs upon naturally 

 growing plants of Mnium hornum. A cytological examination was made 

 of this material and a normal antheridium which happened to be in 

 spermatogenesis showed the haploid number of chromosomes. From 

 this it was evident that meiosis had occurred, and it was not probable 

 that the plant had been produced aposporously as the theory would 

 demand. Also it was suggested that a low proportion of hermaphrodite 

 axes, such as was produced in aposporous cultures, might very well be 

 found in nature following a normal process of sporogenesis. 



My own experience relates to the well-known form Funaria hygro- 

 metrica which has been described by many competent observers as 

 monoicous, whilst others, equally competent, have described it as a 

 dioicous species. Under these circumstances Boodle ^ some years ago 

 undertook an inquiry into the question of the distribution of the sex 

 organs, and after examining material from many localities came to the 

 conclusion that the plant was monoicous, and dioicism, if it occurred, was 

 comparatively rare. It was found that the shoot which bore archegonia 

 terminally, arose as a lateral branch of the axis bearing the terminal 

 male "flower," and no instance was observed in which a female axis 

 produced a male branch. Boodle concluded that the dioicous habit was 

 attributed to the plant because young plants bearing the discoid male 

 " flowers " only were found, and that if female branches were gathered 

 they were generally torn from the male axis to which they were attached, 

 the presence of a basal tuft of rhizoids on the female branches giving 

 them the appearance of distinct plants. 



During the course of some experiments conducted for the purpose 

 of determining the best cultural conditions for the production of proto- 



1 Annals of Botany, 1915. ^ Annals of Botany, 1906. 



