270 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
determiner is ever completely eliminated, since abortive organs, either 
stamens or pistils, are often present in flowers of the opposite sex in sup¬ 
posedly strictly dioecious forms, and occasionally even perfect reproductive 
organs of the opposite sex are found in such “strictly” dioecious forms as 
Acer Negundo. 
‘ In the strawberry the assumption of partial suppression of the female 
determiner is necessary in both the sex chromosomes of male plants of 
F. virginiana. Femaleness is still present and functional to the extent of 
producing apparently normal pistils, which, however, prove to be sterile. 
In the hermaphrodites of the cultivated varieties (derived from dioecious 
wild species) suppression of femaleness is very slight but is still present to 
a degree in many cases, as shown by the decreased fertility of such forms 
when compared with pistillate varieties (7). In some hermaphrodites there 
is apparently no suppression of femaleness, since they may be completely 
fertile. The pistillate plants of F. virginiana we could assume to contain 
two sex chromosomes which are different. One of these would be identical 
with the two found in wild staminates, i.e., male (+ female suppressed), 
and the other bearing the normal female determiner linked with a suppressed 
male determiner. Cultivated pistillate varieties would then be of the 
constitution female (+ suppressed male), and hermaphrodite. In other 
words, we should assume that a single dose of femaleness, if carried as an 
F factor, is sufficient to produce fertile pistils in the pistillate plants, while 
two doses of maleness are necessary for the production of functional sta¬ 
mens. If only a single dose is present, staminodes are produced. On the 
other hand, if there is present a single dose of femaleness linked with a 
normal male determiner, thus forming the recessive II factor, it may or 
may not be sufficient to produce functional pistils. 
An interpretation of the data presented on the basis of these assumed 
chromosome conditions leaves little doubt that the males and hermaphro¬ 
dites are homozygous for sex chromosomes bearing functional male deter¬ 
miners. The females, on the other hand, must be assumed to possess one 
sex chromosome carrying a male or hermaphrodite determiner, and another 
chromosome carrying the female determiner. In other words, we have a 
condition similar to that existing in pigeons and cultivated fowl in which 
the males are apparently homozygous and the females heterozygous for the 
sex determiners. The condition is opposite to that which has been found 
to exist in the females of Bryonia, Lychnis, sweet pea, and Vitis. In view 
of the fact that either males or females may be heterozygous in the animal 
kingdom, it is not surprising that both types should be found in plants. 
The writer has not attempted to give a review of the literature on sex 
inheritance and sex determination ;n plants, since this has recently been 
done rather comprehensively by Yampolsky (8, 9, 10). 
Although a factorial basis for sex determination is rather generally 
admitted to be correct for explaining inheritance of sex in animals, Yampol- 
