Nov. 15,1925 
The Genetics of Sex in Hemp 
939 
to remain green long enough to properly mature seed. It will be 
recalled that the staminate type dies soon after the maturity of the 
pollen, while the carpellate type remains green and vigorous until the 
seed is mature. 
By carefully regulating the relative length of day and night, and 
making drastic mutilations, the writer has succeeded in causing hemp 
which was at first typically staminate to produce functional carpellate 
flowers. The effects of the manipulations on the vegetative develop¬ 
ment were so great, however, as to make the plants very small and 
weak. It was, therefore, not advisable to bag then!, and the seeds 
which they matured may have been the result of either cross or self- 
pollination. Only 11 seeds matured, and of these only 4 grew to the 
flowering stage. The sex distribution was 3 staminate and 1 carpellate 
Of course, these results are entirely too meager to warrant an ex¬ 
tended discussion. The only significant fact brought out is that the 
staminate type carries the potentialities of the opposite sex type. 
DISCUSSION 
In the foregoing presentation of data, relatively little attention was 
given to the details of “sex reversal” which occurred during the 
winter, for the simple reason that they do not directly concern the 
immediate problem. The question to be answered concerns the 
mechanism of sex determination in hemp and not the effect of envi¬ 
ronmental or other factors upon this mechanism. When this much 
has been answered, then the time will be ripe for further inquiry into 
the details of each individual case of sexual modification. 
The misinterpretation of the geneticist's conception of sex in 
dioecious plants has thrown some botanists into a chaos from which 
they have not yet emerged. It has been maintained that because a 
plant of one sex type develops some flowers of the opposite sex type, 
genetic factors are not concerned, and any question of homozygous¬ 
ness or heterozygousness is automatically ruled out. To substan¬ 
tiate such contentions abundant evidence is brought forth to prove 
that either sex type may produce flowers of the other type. With 
the facts shown by such data the writer agrees fully. The facts are 
fairly clear cut. There is a distinct vegetative dimorphism which is 
the same for both the sexual forms which remain pure and those 
which sooner or later show various sexual modifications. Under the 
ordinary cultural conditions found in the field these types occur in 
approximately a 1:1 ratio. The production of normal flowers of 
the opposite sex under such conditions, however, has been observed 
frequently. Among plants grown in the hothouse during the winter 
the sex ratio is approximately 1:1, but usually a large proportion of 
the plants develop flowers of the opposite sex. These flowers are 
usually abnormal. Such behavior is critical evidence that the normal 
development is being modified by environmental factors, but cer¬ 
tainly should not be interpreted as meaning that certain genes are not 
responsible for the normal development of the character. There is 
abundant evidence from the well-known genetics of certain vegeta¬ 
tive characters to show that the environment in which they develop 
may have such an effect as to prevent their expression at all. As 
Emerson (5) has pointed out, the mere fact that the expression of one 
character is influenced more by environment than is that of some 
