126 = Self-Incompatibility in Hermaphrodite Plants 
with hybridity. It is well known that hybrids exhibit all grades of 
vegetative vigour and sexual potency. Here the wide variations in 
either vegetative or sexual development, or in both, indicate that 
certain incompatible combinations of protoplasmic elements fail to give 
harmonious development of the zygote. In a few cases and especially 
where a character is vitally concerned with nutrition (as for example the 
non-chlorophyll condition) there is evidently a selective death of zygotes 
homozygous for this character (see Belling, 1918) but as a rule de- 
generation and impotence in hybrids seem to result from degrees of 
dissimilarity in the relative constitutional organization and development 
inherent in the respective parents. 
It is to be recognized that various grades of impotence may develop 
in a good species through such variations in morphological sex differen- 
tiation as are described by the term intersexualism. Intersexualism 
differs from impotence in hybridity in that it exhibits a tendency to be 
one-sided. Indeed dioecism may be described as a complete one-sided 
and alternative impotence that has arisen out of hermaphroditism. 
Intersexualism may occur in all grades or degrees as is shown by 
Goldschmidt (1916, 1917), Banta (1916, 1918), and the writer (1919) 
and is of course a widespread developmental process leading to 
a complete sex differentiation of individuals as contrasted with the 
differentiation of sex organs in a single “individual. In respect w 
specialization of the individual as a whole intersexualism is a period 
of progressive variation. 
In intersexuality various grades of maleness and femaleness may 
develop for individuals as wholes, or for particular sex organs as such. 
What is perhaps the best analysis of such phenomena in Mendelian 
terms (by Goldschmidt) recognizes that the assumed factors involved 
are themselves variable, that maleness and femaleness are properties 
of all cells, that the factors for sex are the same as factors for general 
growth, and that these are subject to much variation in relative potency: 
There is therefore a decided analogy between the variations in the 
physiological condition of sex organs as revealed by their relative fune- 
tioning in incompatibilities and those variations in the development of 
sex organs that are recognized under the term intersexualism. 
Sex differentiation is hence widely variable in both its morphological 
and its physiological aspects. 
4. Sex-determination and sex-differentiation in hermaphrodites are 
fundamentally a process of ontogenetic development, and may occur at 
various stages in ontogeny. 
