Nov. 15,1925 
The Genetics of Sex in Hemp 
937 
The intersex types (Table I) which occurred in the Chington 
variety were of various kinds, corresponding in general with those 
described by Schaffner (5, 10, 11, 12). In this connection it may be 
well to recall the fact already indicated that the growing of hemp in 
a hothouse does not, in itself, tend to bring about “sex reversal.” 
Only one of the 382 Chington plants which were grown in a hothouse 
during the summer produced any flowers of the opposite sex. The 
proportion in the open plats was about 1 in 800. Both of these pro¬ 
portions are of relatively little significance, except that they demon¬ 
strate that “sex reversal” may occur during the long daylight period 
of summer. Although it is quite clear that relative length of day 
and night is an important factor in bringing about “sex reversal,” it 
is not the only factor causing such changes. 
BREEDING EXPERIMENTS 
The general plan of the experiments was to make self and cross 
pollinations among the extreme intersex types in order to ascertain 
whether the tendency toward sex reversal was inherited. When the 
staminate buds were observed growing on what had been previously 
classed as pure carpellate Simple Leaf plants, the plats were visited 
several times daily, and when the buds were nearly ready to open 
each was removed, carefully brushed to remove foreign pollen and 
placed in a stoppered vial. These were kept in the laboratory until 
the anthers opened and liberated the pollen. This pollen was then 
transferred to stigmas of carpellate flowers which had been bagged 
for some time previously. Both pure carpellate and monoecious 
individuals were used. Three types of pollinations were made, 
namely, self-pollination, pollination of a pure carpellate with pollen 
from an intersex type, and cross-pollination of Chington stock plants 
as a check. From this series of pollinations a total of 326 seeds was 
obtained. When these seeds were planted in the greenhouse the 
results shown in Table II were obtained. 
Table II .—First generation of crosses between intersex types 
Variety 
Number 
of seed 
planted 
Carpel¬ 
late 
Stami¬ 
nate 
Total 
Simple Leaf intersex selfed_ 
100 
71 
0 
71 
Simple Leaf carpellate X Simple Leaf intersex_ 
64 
56 
0 
56 
Simple Leaf carpellate X Chington intersex... 
37 
31 
3 
34 
Chington carpellate X Chington staminate__ 
148 
46 
42 
88 
It is at once obvious that there is a difference between the sex ratio 
of the check and that of each of the three other lots. The 88 plants 
in the check plat happened to give almost exactly a 1: 1 ratio of the 
sexes, but of the other 161 plants, representing 3 series of pollinations, 
all except 3 were carpellate. The appearance of the 3 staminate 
individuals among the progeny of the Simple Leaf carpellate X Ching¬ 
ton intersex cross is not in accord with the results of the other crosses. 
The probable cause of this, however, is not difficult to find. The 
enormous amount of pollen which is produced by a single staminate 
hemp plant makes the elimination of contamination very difficult; 
