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CECIL YAMPOLSKY 
female; specific crosses 4.3 males to I female; racial crosses 1.9 males to i 
female. The normal sex ratio for any of these species when they are crossed 
inter se is i :i or at most not higher than 1.3 males to i female. Riddle con- 
firms Whitman's conception that width of cross in doves and pigeons is of 
first importance in determining sex ratios. In general, the wider the cross 
the higher is the proportion of males. The proportion of males to females 
reported by Riddle ranges from 15 males to i female to as low as .78 male to 
I female. 
The true relation of the sexes in plants is made specially clear by the 
occurrence of the variously graded forms, sex intergrades, that are found 
between the pure female and pure male extremes as I have described them. 
The sporadic appearance of male flowers on the female plants has been es- 
tablished for hemp and Lychnis, as well as for Mercurialis. 
Shull (1914) in a cross between his broad and narrow-leaved forms of 
Lychnis dioica secured 96 plants, 95 of which bloomed and proved to be all 
females. In matings between F2 narrow-leaved males and numerous fe- 
males he secured a total of 2741 males and 14 females. An hermaphroditic 
specimen when used as pollen parent produced 276 females. 
The Mendelian hypothesis of sex in itself cannot account for the pre- 
ponderance of one sex to the exclusion of the other. Other ancillary hypo- 
theses must be assumed, such as selective fertility of sperm or egg, selective 
viability, and lethal factors, in order to explain the results. 
Inheritance of Femaleness 
The history of the work on the inheritance of sex in Mercurialis is of 
interest. Kriiger (1908) reported that what he thought were partheno- 
genetically produced seeds on female M. annua plants, upon germination 
gave only female plants and thus confirmed Strasburger's observation. 
Bitter (1909) first showed that seed production on female plants of M. annua 
is due to the presence of isolated male flowers on the female plants. His 
work showed definately that in this case the seeds do not arise partheno- 
genetically. Bouche (1881) had observed the appearance of isolated male 
flowers on female plants of M. annua. 
Bitter (1909) began his studies in 1903. In a series of experiments he 
obtained a total of 723 female to 21 male plants from a number of parents 
which he calls females. However, it is to be noted that not all the plants 
were grown in sterilized soil, and as we cannot be certain that no seed from 
males was present, the females in all probability were not all pure females — 
in one case he describes one as having ''many male flowers, " and we have 
no indication as to whether the males were growing near by and from what 
plants the females were pollinated. 
Strasburger (1909a) reports on his female cultures of M. annua and con- 
firms Bitter. He secured 907 seeds from his female plants. These he 
sowed. 148 germinated, only 16.3 percent, and all were females. He also 
