VARIATION OF CimOMOSOMES 



153 



chromosome is present that goes to half only of the spores. 

 Presumably then in liverworts, and mosses, also, there 

 is an internal mechanism for producing the two ''sexes." 

 The Marchals have worked both with species having 

 separate sexes and with hermaphrodites. We may con- 



xyizn) 



y(27U 



>T/m) ® x(nt 



Fig. 60. 



xy(4n) 



Fxa. 60. — Diagram illustrating the formation of £n individuals from the regeneration of 

 the sporophyte in a dioecious species. (According to Marchal.) 



Fia. 61. — Diagram illustrating the formation of 2n individuals from the regeneration of 

 the sporophyte in a hermaphroditic species. (According to Marchal.) 



sider the former first. If the sporophyte is removed and 

 cut across, its cells regenerate a tangle of threads (pro- 

 tonema), which is the beginning of a new moss plant (Fig. 

 60). Since the sporophyte had the double number (2iY) 

 of chromosomes, it is to be expected that the young moss 

 plant that regenerates from its tissue (sporophyte) will 

 also have the double number, and such proves to be the 



