No. 503] 



NOTES AND LITERATI' HE 



735 



Cryptogams." It may be said, however, that some remarkable 

 parallelisms, if not real homologies, are shown by the peculiar 

 Anthocerotes, and there is a progressive development of the 

 sporophyte in both liverworts and true mosses which hints at 

 least at the course of evolution which finally resulted in the 

 entirely independent sporophyte of the ferns. The evolution of 

 the sporophyte consists in a constantly increasing development of 

 sterile or non-sporogenous tissues, which assume the character 

 of green assimilative tissue, etc., and it may finally develop 

 definite external organs, roots and leaves, the former connecting 

 the sporophyte with the earth and making it quite independent 

 of the gametophyte. Finally, spores are produced, always in a 

 perfectly uniform manner in groups of four, and the life history 

 is complete. 



While only a relatively small number of forms have been 

 investigated, it is pretty certain that the sporophytic tissues 

 normally have nuclei with twice the chromosome number found 

 in the cells of the gametophyte, this being the result of the 

 doubling of the chromosomes due to the fusion of the gametes. 

 The reduction of the chromosomes occurs in the tetrad division 

 resulting in the spores, which therefore possess the normal 

 gametophyte number. 



The formation of the sporophyte by apogamy or direct bud- 

 ding from the prothallium. and the various buddings of the 

 gametophyte from the leaves of the sporophyte, are the strongest 

 arguments in favor of "homologous" alternation: but the facts 

 of apogamy and apospory may be explained as cases of adven- 

 titious budding analogous to so many cases found in the seed 

 plants, and much more evidence is needed to show that they are 

 normal rather than pathological. 



Comparing the sporophytes of the Bryophytes and Pterido- 

 phytes, the latter are distinguished by the development 

 of external organs. A more or less conspicuous central axis 

 has appendicular organs. leaves, roots and sporangia, the 

 latter being the characteristic organs which distinguish the dif- 



arisen from the n.on- or less eomplete segregation^ masses of 



such form as Anthoceros. The gradual evolution of the 

 sporangium from the large indefinite sporocysts like those f 

 Ophioglossum to the very definite sporangia of the highly 



