336 Proceedings of the Ohio State Academy of Science 



usually 8-12. Thenceforth so long as the cone continues to 

 grow during the remainder of that season megasporangia only 

 are developed. Here then sex determination goes parallel with 

 the seasons. And it is interesting to note that male and female 

 producing spores are developed in much the same way as the 

 alternate zones of sporophylls and foliage leaves in some 

 Lycopods. 



These examples show that sex determination goes on with- 

 out any reference to a reduction division or to the segregation 

 of sex-determining bodies. Either directly or indirectly the 

 control of sexuality may be dependent on the seasonal environ- 

 ment in exactly the same way as foliage leaves and scale leaves 

 are determined in harmony with seasonal conditions on a woody 

 twig. 



SEX CONSTANCY. 



In some organisms, it does not seem possible to change the 

 sex by any known manipulation when once determined. Sc 

 long as the individual continues, either directly or through vege- 

 tative propagation the sex remains the same. This has been 

 found to be the case in the gametophytes of Marchantia for ex- 

 ample. In these gametophytes the haploid number of chromo- 

 somes is present and they are always strictly male or female. 

 In related Bryophytes the gametophytes, also with the haploid 

 number of chromosomes, are hermaphrodite. Therefore the 

 haploid and diploid, or the x and 2x, condition of chromosomes 

 has nothing to do primarily with the determination of the sexual 

 condition. And because the sexual condition cannot be changed 

 means no more in the given case than that certain leaves have 

 lost the power of reproduction while others have not. There 

 is no structural difference in the hereditary apparatus so far as 

 our cytological knowledge goes but only a difference of condi- 

 tions.' The latency of the opposite hereditary tendency is to all 

 appearances complete. 



In some ferns the gametophytes, normally hermaphrodite, 

 can be kept as males or females by a proper control of the en- 

 vironment. In Equisetum arvense, the gametophytes are uni- 



