SEX INTERGRADATION IN THE FLOWERS OF MERCURIALIS 
ANNUA 
Cecil Yampolsky 
The older observers have repeatedly called attention to various aber- 
rancies in plant structures, and these have been grouped under teratological 
phenomena. In this general category have been placed many unrelated 
phenomena as well as unexplainable ones. That has been particularly true 
with such occurrences as the appearance, upon a part of a plant which nor- 
mally bore the organs of one sex, of the sex organs of opposite character. 
In another paper (191 9) I have called attention to the fact that we may con- 
sider conditions such as the appearance of female flowers or branches on a 
male plant, male flowers or branches on a female plant, etc., as evidences of 
sex intergradation by no means uncommon in the plant kingdom. 
In continuing my studies on Mercurialis annua, especially on the so- 
called monoecious form, I have observed some very interesting phenomena 
which appear to shed further light upon the question of sex determination. 
Mercurialis annua is described as appearing in three forms, male, female, 
and monoecious. The flowers of the female are, as a rule, two-carpeled, 
although often three-carpeled, and they are borne in clusters in the axils of 
the leaves. The flowers of the male are borne in interrupted spikes which 
surpass the leaves. The flowers of the so-called monoecious form (male, 
female, and hermaphroditic flowers) are borne like those of the female in 
clusters in the axils of the leaves. 
The individual flowers of the three forms are minute and almost incon- 
spicuous. The female flowers are apetalous, green — each carpel with a 
single ovule — a two-parted stigma which is white, translucent, and with 
roughened surface. In the instances in which there is either only one 
carpel or more than two, the stigma is undivided or multipartite depending 
upon the number of carpels. The carpels have a rough appearance due to 
the presence of characteristic translucent hairs. There are also two nec- 
taries. The male flowers are apetalous with 8 to 20 stamens. Each 
stamen consists of a two-sacked yellow anther and a slender filament. 
The hermaphroditic flowers are like the female flowers with stamens borne 
from the bases of the carpels. 
In a preceding paper (19 19) I have reported upon the appearance of 
sporadic male flowers upon the female plants and of female flowers upon the 
male plants. Upon the female plants I have also noted and described 
various kinds of hermaphroditic flowers. Such flowers have also been 
observed on the so-called monoecious form but in much greater numbers. 
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