June 14,1924 
Influence of Environment on Sex in Hemp 
1077 
THE EFFECT OF MUTILATIONS ON SEXUAL DEVELOPMENT 
The two factors which other investigators think are the most important in 
bringing about a modification of sexual expression in hemp are short daily ex¬ 
posure to light and flower removal. Schaffner (5, 6 , 7 ) has been able to obtain 
various degrees of “sex reversal” by growing hemp in the greenhouse during the 
short days of winter and Pritchard (4) has shown that a certain amount of 
modification of the sexual state is apparently caused by removing the flower buds 
as soon as they appear. If such factors as length of day and flower removal 
influence the sexual condition of hemp, it seems reasonable to suppose that the 
two factors combined might have a decisive influence in causing “sex reversal.” 
To test out this assumption, several plants were selected in each of the light 
exposures used in the dark house and their flowers were systematically removed 
during the flowering period. 
From 16 staminate plants in the 5-hour exposure a total of 1,832 buds were 
removed but only two of these plants later developed any carpellate flowers. 
The hemp in this room was so weak that very few flowers were produced after 
the operation of flower removal, so that no very definite conclusions can be 
drawn from this experiment. The carpellate flowers that were produced were 
very abnormal and occurred in hermaphrodite buds. 
From 14 staminate plants in the 7-hour day a total of 5,083 buds were removed. 
Subsequently, all but one of these plants developed carpellate flowers of various 
degrees of perfection. Many of these carpellate flowers were abnormal and such 
forms as a three or four-styled flower, anthers terminated by a style, and mixtures 
of stamens and carpellate flowers in the same bud, were very common. A certain 
number of functional carpellate flowers were produced and several seeds were 
matured. 
From six staminate plants in the 10-hour exposure a total of 3,555 buds were 
removed but only three of these plants later developed any carpellate flowers. 
A few of these flojvers were functional and matured a few seeds. From eight 
carpellate plants in this day length a total of 260 flowers was removed but only 
one of the plants so operated on later developed any staminate buds. Since, as 
already mentioned, one of the carpellate plants in this room developed some 
staminate buds without having had its flower buds removed, the above cited case 
of modification of the sexual expression by mutilition does not seem important. 
The removal of flowers from hemp which was grown in the open during the long 
days of summer was without effect in causing modifications of the sexual state. 
From seven staminate plants a total of 16,425 buds was removed but none of 
these plants later developed any carpellate flowers. If the removal of the flowers 
was a determining factor in causing sexual modifications in this species, as Prit¬ 
chard has suggested, some of these plants should have shown a tendency to 
develop carpellate flowers but their behavior in this experiment indicates that 
the mere removal of the flowers will not necessarily cause “sex reversal.” In this 
connection the occasional spontaneous production of normal staminate flowers 
by carpellate plants in the field should be mentioned. Occasionally carpellate 
plants of any of the varieties of hemp will produce a few perfectly normal stami¬ 
nate flowers. This is especially true of the Simple Leaf variety. This fact makes 
the occasional production of a staminate bud by a mutilated carpellate plant 
entirely without significance and until more positive results are recorded we can 
conclude that the systematic removal of flowers from hemp which is grown in the 
field during the long days of summer does not affect the sex of the subsequent 
flowers. 
To obtain more evidence on sexual modification in short days, additional 
experiments were conducted in the greenhouse during the winter with plants 
