May, 1923] VALLEAU-INHERITANCE IN THE STRAWBERRY 
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sky and others are not inclined to believe that it will also explain the con¬ 
ditions found in plants. This is due primarily to the fact that an individual 
may during its life or during the flowering of a single cluster appear to 
change its sex. In other words, there may be “a periodic alternation of 
sex.” Yampolsky (10, p. 99) holds that “a factorial hypothesis for sex 
can not explain these results.” In his work on sex intergrades and sex 
inheritance he worked primarily with Mercurialis annua. The material is 
unfitted for a study which will readily produce accurate results because of 
the mechanical difficulties encountered in making the crosses necessary for 
a proper interpretation of the genetic constitution of the several plant 
types. His conclusion that males when selfed tend to produce males or 
plants predominantly male, and that females selfed tend to produce females 
or predominantly females was based on the results of selfing a large number 
of flowers on female plants, of crossing females with males (which produced 
a 1 : 1 ratio of males and females), and of selfing female flowers on male 
plants. His results obtained by selfing female plants would seem to show 
conclusively that the females are homozygous for sex determiners, if we 
attempt to explain the results on the factorial basis. Females X males 
produced a 1 : 1 ratio of females and males, as would be expected, and the 
results suggest, in view of the results obtained from selfed females, that the 
males are heterozygous for the sex determiners. Although self-pollinated 
males produced only males, the statement (8, p. 434) that “the selfed males 
of Mercurialis annua may be said to record their own gametic constitution” 
is not based on sufficient evidence to warrant discarding the chromosome 
hypothesis of sex inheritance in plants. Yampolsky does not take into 
consideration the possible effect of lethal factors on sex ratios. There is 
abundant evidence from his results to indicate that the sex ratios of the 
progeny of his selfed males may have been influenced by lethal factors 
which inhibited the normal development of the embryos or which later 
affected germination either by weakening it or by destroying it completely. 
From a total of 156 female flowers on one lot of male plants he obtained 
283 seeds. Of these, 31 were immature. He explained immaturity as the 
result of one seed developing faster than the other in two-seeded ovaries, 
so that in gathering the seeds the immature one is likely to be gathered 
with the mature one. Of the 283 seeds obtained from this lot of male 
plants, 219 were sown. Of this number 75 seedlings only developed. These 
were all male plants. It is obvious that something interfered with the 
normal development of the other seeds. Certain ones developed slowly; 
others germinated weakly and then died; while o'thers did not germinate 
at all. Horticulturists are generally aware of the fact that slightly immature 
seeds germinate nearly as well as, and often better than, mature ones. 
There is a question as to whether immaturity can be correctly assigned as 
the cause of failure of any of the seeds to germinate. Yampolsky (8, 
p. 432) has used the work of Shull (4) on irregular sex ratios in Lychnis 
