No. 526] SEXUAL REPRODUCTION IN ANGIO SPERMS 605 



most important results of sexual reproduction, namely, 

 the transmission of parental characters. It will be 

 maintained also that the union of mere gametophytic 

 cells does not constitute fecundation, or a sexual process 

 in phanerogams, nor is parthenogenesis— if such really 

 exists in seed plants— to be confused with apogamy, nor 

 apogamy with the various sorts of vegetative propaga- 

 tion of the sporophyte. Lastly, it is likewise the duty 

 of the student of fecundation to consider the phenomena 

 of graft hybrids which have been reported in recent 

 literature, for such phenomena may have a profound 

 significance in the shaping of future theories of sex and 

 heredity, and on sex determination and control. 



The problem of sexual reproduction in higher plants, 

 and in lower ones as well, is complicated by the existence 

 of two distinct phases, or individuals, in a life cycle, 

 namely, the gametophyte and sporophyte ; for it is neces- 

 sary, in dealing with the role of the nucleus in sex, to 

 consider a complete life cycle. Now gametophyte and 

 sporophyte in phanerogams are fundamentally different 

 hereditarily, and this difference is due chiefly to the fact 

 that the former possess the haploid, or x number, of 

 chromosomes, and the latter the diploid, or 2x number. 

 Whatever respect or disrespect one may have for the 

 "sacred" x and 2x number of chromosomes, the fact of 

 their importance in any theory of sex and heredity re- 

 mains the same, and must be taken into consideration. 

 It is, of course, quite familiar to all that the change from 

 sporophyte to gametophyte occurs in the formation of 

 the spores, and that this change consists in the reduction 

 of the number of chromosomes from the diploid, 2x, to 

 the haploid, x number; that this reduction is accom- 

 plished during the first mitosis in the spore mother-cells, 

 this division of the nucleus being acknowledged as quali- 

 tative or differential. A detailed description of the 

 evolution and behavior of the chromosomes during the 

 tetrad divisions, and a discussion of controversies and 

 of the different views held in regard to this evolution, 

 or in regard to the differential character of any chromo- 



