106 The Ohio Journal of Science [Vol. XVIII, No. 4, 



and femaleness of the gametophyte. The determination of the 

 sex takes place in the vegetative tissues of the sporophyte. 

 Whatever it is that determines that the given tissue shall 

 develop as a megasporophyll or a microsporophyll also deter- 

 mines absolutely the sex of the following generation of game- 

 tophytes. We are dealing with the establishment of a state 

 in the cells of a vegetative tissue. A moment's reflection 

 will show how extremely inappropriate is the application of the 

 terms, homozygous and heterozygous in relation to sex indivi- 

 duals. Sexuality is just as pronounced in haploid gameto- 

 phytes as elsewhere. The males, females and hermaphrodites 

 of the higher plants can not be "zygous" at all in the normal 

 life cycle. They are the results of segregation rather than of 

 conjugation. The vast majority of sporophytes are bispor- 

 angiate and are of course homozygous or heterozygous in their 

 chromosome condition, but here the sex is determined in the 

 vegetative tissue before spores are produced. 



In some species of Bryophytes it has been claimed that two 

 of the cells of the reduction tetrad normally give rise to males 

 and the other two to females. In such cases the sex must be 

 determined in the spore mother cells (daughter cells of the 

 sporocyte). But a sexual state might be influenced by unequal 

 distribution of the cytoplasm. In great numbers of Bryophytes, 

 however, the gametophyte is hermaphrodite and the establish- 

 ment of the sexual state necessarily takes place in the vegetative 

 cells of the gametophyte. Recently Allen* has reported a 

 difference in size in one pair of chromosomes in the spore mother 

 cells of Sphaerocarpos. Even if such a difference can be 

 associated with a specific sex difference, it does not necessarily 

 follow that the sex condition is determined by an irreversible 

 sex factor in the given chromosomes. However, in this case 

 where the sex individuals are haploid, such a hypothesis would 

 be much more convincing than in the case of the diploid animals. 



In dealing with sexual phenomena in plants, the problem is 

 always complicated by the presence of an antithetic alternation 

 of generations. Because of a confusion in terminology coming 

 from a past period w^hen the nature of the plant life cycle was 

 unknown, it is often difficult to correlate the meaning of expres- 

 sions used by different writers, especially of those who disregard 



*Allen, Chas. E. A Chromosome Difference Correlated with Sex Difference 

 in Sphaerocarpos. Science 46 : 466-467. 1917. 



