INHERITANCE OF SEX IN MERCURIALIS ANNUA 
439 
The hermaphroditic offspring may be considered as graded females. When 
A was used as a female parent and pollinated by a male the resultant off- 
spring may be regarded as graded females; they were, according to Shull, 
hermaphrodites and males. Shull's work does not seem to strengthen 
Correns' assumption that the pollen in a dioecious form is of two kinds. 
In crosses between female Fragaria virginiana and male F. chiloensis, 
Richardson (1914) secured 16 female, 12 male, and 6 hermaphroditic off- 
spring. From another cross he secured 49 females, 27 males, and 16 her- 
maphrodites. In a cross between female F. virginiana and hermaphroditic 
F. grandiflora as male parent, he secured 20 females, o males, and 14 her- 
maphrodites. In a cross between female F. virginiana and hermaphroditic 
F. visca, he secured a few fertile males, very few fertile hermaphrodites, 
sterile females, and some apparent males. A cross of the nearly pure 
male F. chiloensis (hermaphrodite) and F. grandiflora (hermaphrodite) 
used as the male parent, gave a minority of hermaphrodites, a majority of 
males, and no females. 
I have discussed the relation of the foregoing data and theoretical con- 
siderations to the general question of sex intergradation in another paper 
which is to appear soon. 
Summary 
1. Female plants of Mercurialis annua show gradations in degree of 
femaleness from pure females, which have no male flowers and never set 
seed when isolated, to those which produce a considerable number of male 
flowers and seeds. 
2. Offspring of selfed plants which are prevailingly female are female and 
prevailingly female, showing similar variations in the number of male 
flowers and seeds produced to those displayed by the parent plants. 
3. Male plants of M. annua show gradations in maleness due to the 
sporadic appearance of female flowers and the subsequent production of 
seed on the male plants. 
4. Offspring of prevailingly male plants are male or prevailingly male 
5. While the tendency for females to produce females and for males to 
produce males is obvious, the sporadic occurrence in varying numbers of 
flowers of the opposite sex on either form makes it clear that sex intergrada- 
tion is a condition to be recognized in the plant kingdom. The rather 
sporadic appearance of flowers of the opposite sex upon a plant points 
also to the fact that sex determination is not absolute. 
6. The condition of sex intergradation points to the fact that a theory 
of inheritance of sex which assumes fixed sex factors segregated at the time 
of the reduction division, cannot account for the production of sex inter- 
grades. 
7. In a discussion of sex determination in plants in which alternation 
of generations regularly occurs, both generations must be borne in mind. 
