May, 1923] VALLEAU — INHERITANCE IN THE STRAWBERRY 
273 
In general, in Fragaria there appears to be a tendency towards femaleness 
in the earliest flowers which bloom; while the later flowers have a tendency 
towards maleness in the hermaphroditic varieties. A similar tendency 
with regard to increasing pistil sterility in the later blossoms is apparent, 
but to a lesser degree, in the cultivated females. The females of dioecious 
wild forms and all the plants of the wild hermaphroditic forms exhibit an 
extremely high degree of pistil fertility extending through all the flowers of 
a cluster. It is seldom that irregular berries are seen in wild forms, even 
under the most adverse conditions. 
The writer does not believe that the presence of other sex types of 
flowers on a plant, which is predominantly of one sex, necessarily means 
that sex is not determined by specific factors or that such a condition is an 
argument against a Mendelian interpretation of sex in plants. 
If it is assumed that dioecious forms have been derived from hermaph¬ 
roditic forms, and if we accept, for the present, the theory that in hermaph¬ 
rodites the two sex determiners are linked in one chromosome, then the 
production of males and females in such forms as Fragaria and Vitis, where 
the opposite organs are still present but not functional, must have come 
about by the partial suppression of one or the other sex condition in the 
chromosomes but not by its complete loss. Thus, in the female plant of 
F. virginiana two sex chromosomes would be present: one which carries 
the functional factor for femaleness (which is sufficient to produce functional 
pistils), and another which carries the functional factor for stamen produc¬ 
tion, but which, in the absence of another similar functional factor, is 
unable to produce functional stamens. Each chromosome, however, would 
carry the opposite factor suppressed. The males would then contain two 
like chromosomes, each of which carries a functional determiner for stamen 
production and a suppressed determiner for femaleness. It appears that 
no other assumption will meet the actual conditions. It is apparent from 
the facts previously given that the sex condition may be varied by varying 
the conditions under which the plants are produced. This may result by 
changing either the outer environmental factors of the plant or the internal 
factors of nutrition (?) due to the position of the flowers on the inflorescence. 
Such changes have been observed. It is not a far step, then, to assume 
that in certain parts of a plant conditions are set up which have a tendency 
to decrease the suppression of factors which are already present and to 
allow flowers or flowering parts of the opposite sex to be produced on a given 
plant. The determiners for sex in plants may be specific entities, but 
still their full or partial expression may depend upon the immediate condi¬ 
tions surrounding them at the time of flower production. 
LITERATURE CITED 
1. Dorsey, M. J. A study of sterility in the plum. Genetics 4: 417-488. 5 Pis. 1919. 
2. Richardson, C. W. Some notes on Fragaria. Jour. Gen. 10: 39-46. 2 figs. 1920. 
