30 
CECIL YAMPOLSKY 
inflorescences of the two sexes may be considered as the secondary sex 
character of the two sexes, in the sense that the manner in which the in- 
florescences are borne is characteristic for each sex. No doubt a closer ex- 
amination of other dioecious forms will show differences in male and female 
pedicels, petals, and sepals, either by their presence or by their absence. 
It is interesting to note that in sex intergradation in Mercurialis annua 
there is no transition of a secondary sex character of one sex into that of the 
other. Those females which tended towards maleness by producing many 
male flowers and many seeds did not take on the general growth characteris- 
tics of the male. The same holds true for the males that tended towards 
femaleness — they too still maintained their characteristic form of growth. 
The Doctrine of Varying Potencies in Germ Cells 
Alternative inheritance of sex is the extreme of a series of intergraded 
variations. Hermaphrodites (with perfect flowers) and monoecious forms 
become dioecious not by the sudden development of heterozygosis in one 
sex and the separation of sex factors in the reduction division, but by the 
gradual development of sex purity (dioecism) through a long series of 
intergraded sex variants. The connecting links can all be found in the 
polygamous (mixed) species. If dioecism has arisen in this way, it is hardly 
likely that there is anything of the nature of fixed, invariable sex factors in 
the germ plasm. It is a matter of fluctuating tendencies. Male tends to 
produce male, female to produce female; sometimes one tendency is stronger, 
sometimes the other. 
Strasburger (19 lo) attacks Correns' view that one sex is heterozygous 
for a sex determiner on phylogenetic grounds. The evolutionary trend has 
been to make the egg and sperm different. Phylogeny points to the egg's 
being female-producing and the male gamete's being male-producing. 
It is certainly an awkward assumption that one half the male gametes, for 
example, must carry female determiners. In an earlier work Strasburger 
(1909a) concluded that the egg of the dioecious phanerogam tends to produce 
females only, while in the production of the microspores of a tetrad by 
division of the pollen mother cell two of the spores will have a stronger 
male tendency than the other two. Those with the stronger male tendency 
(which is transmitted to their descendants, the male gametes) will dominate 
over the female tendency of the egg and thus males will be produced, while 
the weaker male tendency of the other two will be dominated by the stronger 
female tendency of the egg and females will result. Noll (1907), from his 
studies of dioecious plants, was led to this view that there are pollen grains 
of two strengths as regards the male-producing tendency. 
While Strasburger's view explains the behavior of his selfed females and 
of his selfed males, and the sex of the progeny resulting from the fertiliza- 
tion of a female by a male, there is one difficulty that he overlooked. As- 
suming that the eggs are all of one kind, then the eggs produced on the 
