June 14, 1924 
Influence of Environment on Sex in Hem'p 
1069 
such cases vary all the way from pure staminate to pure carpellate. The writer 
has observed flowers containing two anthers and a rudimentary ovulary with 
one, two, or three stigmas; an apparently normal ovulary and two or three rudi¬ 
mentary anthers; three normal stamens and one terminated with a stigma; two 
ovularies, each with three stigmas; and many others. Of course, many of such 
abnormal flowers are not functional and therefore the highly intersex types seldom 
produce much pollen and set few seeds. Such behavior in the greenhouse during 
the winter when the daily period of light is relatively short indicates, as Schaffner (6) 
has already shown, that sex in hemp is largely under the control of environ¬ 
mental factors. If this is true it should be possible to obtain almost any desired 
degree of “sex reversal” by regulating the environmental factors. 
PLAN OF THE EXPERIMENTS 
For the purpose of producing different lengths of daily exposure to light, a 
series of ventilated chambers were used from which light could be excluded at 
will by means of sliding sashes upon a glass roof. The walls of each chamber 
were covered with black paper to prevent any light which might gain entrance 
from being reflected. Observation showed that when the shutters were closed 
these rooms were dark even at noon and gave a sufficiently good imitation of 
night for the purposes of this experiment. In the discussions which follow these 
chambers will be spoken of as the dark house. With such an arrangement, the 
large amount of labor connected with the daily moving of plants in and out of the 
house was eliminated and the effects of adverse weather conditions, such as high 
winds and rain, were reduced to a minimum. 
The maximum difference in the temperature of the rooms did not exceed 3° C. 
during the course of the experiment. Although the difference between the 
temperature of the outside air and that inside the house was much greater than 
this, such differences are not of importance to this investigation, since adequate 
control plants were grown in one of the rooms. In work where the control plants 
were grown in the open it would, of course, be necessary to take into consideration 
the difference in temperature of the inside and the outside air. 
The plants for this experiment were obtained from seed sown in flats in the 
greenhouse. As soon as the seedlings were well up, the flats were removed to 
the dark house and the different exposures to light were started at this time and 
continued until the maturity of the plants. At the time of potting, all of the 
seedlings were saved. 
Inasmuch as soil and size of the pot have a marked effect on plant growth, 
great care was taken to keep these two factors constant for all lots of seedlings. 
Sufficient soil was thoroughly mixed at the start to last throughout the experi¬ 
ment. The potting of all lots was always done on the same day so that the plants 
in each house would have the same chance in this respect. The seedlings were 
first placed in 2-inch, later in 3-inch, and finally in 5-inch flower pots. To further 
prevent differences due to nutrition, all pots were placed on wooden benches so 
that the roots could not go through the bottom of the pots into soil. 
Water was applied during the course of the experiment in such quantities as to 
keep the moisture content of the soil practically the same in all pots. Moisture 
tests were not made because it was believed that fluctuations in water supply 
within the limits present in this experiment have no effect upon sex in hemp. 
The lengths of exposure used were 5 hours, 7 hours, 10 hours, and the normal 
length of day for this latitude. By reference to figure 1 it is seen that the period 
from sunrise to sunset during the course of the experiment was from 12 to slightly 
over 15 hours daily. The sashes were removed from all compartments at 7 a. m. 
and replaced as follows: In the 5-hour exposure at 12 m., in the 7-hour exposure 
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