NUCLEAR PHENOMENA OF SEXUAL REPRO- 

 DUCTION IN GYMNOSPERMS 1 

 CHARLES J. CHAMBERLAIN 

 University of Chicago 



To the cytologist the most interesting phases of a 

 plant's life history are fertilization and the reduction 

 of chromosomes, processes which initiate the sporophyte 

 and gametophyte generations and which are of the ut- 

 most importance in any cytological theories of heredity. 



We shall not attempt to define fertilization, but shall 

 simply state that, in our opinion, the process is essen- 

 tially uniform from its first appearance in the fusion 

 of equal gametes in the lower algae, up to the heterog- 

 amy of the angiosporms and, in our opinion, this fusion 

 of gametes, whether they be the equal gametes of the 

 lower alga? or the unequal gametes of the higher plants, 

 always initiates a sporophytic phase in the life history, 

 a phase which normally continues until the reduction 

 of chromosomes brings it to a close and initiates the 

 gametophytic phase. 



The gymnosperms have as yet only a single well-es- 

 tablished case of apogamy and not even a single case 

 of apospory, and. consequently, their only mode of re- 

 production, aside from occasional budding, is that re- 

 sulting from fertilization. 



Since the significance of fertilization becomes more 

 iutcll'm-ible with increasing knowledge of the partici- 

 pating gamete-, it is of prime importance to know the 

 structure, evolution and behavior of the sperms and 

 eggs. 



Spermatogenesis 

 The sperms of fossil gymnosperms are almost un- 



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