58 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
differentiation has been partly achieved. This often results in a more or 
less complete sexual impotence or sterilization, a condition which has 
naturally been very generally regarded as abnormal and pathological. This 
is, however, not the case in those species of plants which are prevailingly 
dioecious or monoecious, for here, as well shown in the muskmelons, there 
is a tendency to produce flowers that are fully functional as hermaphrodites. 
Whether, however, intersexualism results in complete sterility, as it 
frequently does in dioecious animals, or in one-sided sterility, as is the rule 
in hermaphroditic plants, the physiological basis for these variations in sex 
is to be regarded as most fundamental in the determination and expression 
of sex. 
It is, furthermore, to be recognized that the mixture of sexes, with 
blending and changes in the character of the organs, often results in a wide 
range of variation in the morphological character of the different sex organs 
produced by a single individual. In many plants, the flowers on a single 
individual may be staminate, pistillate, and hermaphroditic, with also many 
intergrading types, thus exhibiting many grades of sexual impotence with 
marked differences in the ability to produce fruit. 
These cases of partial variability in sex are of special interest, for here 
the various conditions of alternative impotence with corresponding irregu¬ 
larities in the production of fruit are all seen among the flowers of a single 
individual. In such cases there is also opportunity to observe whether the 
variations are irregular and sporadic or whether they are related to a 
definite period in development or are otherwise periodic. It is with special 
reference to these questions that the changes in the character of the flowers 
of Cleome spinosa L. are here reported as decidedly alternative and re¬ 
peatedly cyclic, resulting in the intermittent production of fruit. 
Observations on Cleome spinosa 
This species is most favorable material for a study of variation in the 
sex of flowers in relation to the development of the plant as a whole. It 
has long been known as having mixed flowers, yet the species has not 
become dioecious. All the individuals of the species are apparently quite 
alike in respect to the general range of variations in the sex of the flowers. 
The species is a quick-growing herbaceous annual. The first flowers open 
on the main raceme when the plant is relatively small—about two feet tall 
—and while the lateral branches are scarcely visible. The main raceme 
continues to elongate, producing flowers daily, often for a period of from 
eight to twelve weeks. Meanwhile a dozen or more lateral branches develop, 
and these may in turn branch. All the branches grow rapidly and produce 
flowers in abundance. When autumn arrives, well-grown plants are five 
or more feet tall with a spread of branches of as many feet in diameter. 
There has been a long period of bloom, often covering as many as ninety 
days, and this has been for the most part coincident with the period of 
