A. B. Stour 127 
In hermaphrodites maleness and femaleness are both qualities 
possessed by all cells. Any nuclear organization or combination resulting 
after reduction division can become male or female according to whether 
the cell lineage leads through stamens or pistils. The obvious differen- 
tiation of the two sexes, morphological and physiological, may begin in 
the development of entire branches, or of flowers as wholes, or of stamens 
and pistils of the same flower, and is at first strictly a somatic differen- 
tiation of like diploid cells. The sexual nature of these sporophytic 
structures is however seen in the intimate part which they play in the 
production and function of the haploid sex generation. 
A self-incompatible plant is itself the result of a compatible fertiliza- 
tion. Cytoplasmic and nuclear elements of an egg and a sperm fuse to 
form a zygote highly vigorous and of high sexual potentiality, yet its 
sex organs fail to function together. The elements which were com- 
patible in the fertilization and in the life of the resulting zygote became 
incompatible during ontogeny. Yet the incompatibility does not arise 
simply because of the element of constitutional similarity involved in 
hermaphroditism, nor because of sex-differentiation as such, for a sister 
plant with the same parentage and ancestry may be highly self- 
compatible. 
Sexuality is a cyclic recurring condition which makes possible the 
fusion of cells and nuclei and the pairing of chromosomes. The incom- 
patibilities exhibited in processes of fertilization are due to physiological 
properties that are acquired during sex differentiation. 
Whether the most successful fertilization depends on some element 
or degree of similarity, or on some degree of dissimilarity, or on a proper 
balance of the two, it is clear that the behaviour of incompatibilities 
both self and cross gives no proof that unlikeness in the sex organs 
favours the union of gametes, or that some element of similarity leads 
to incompatibility. 
New York Boranitcat GARDEN, 
May 29, 1919. 
