Feb., 1923] 
STOUT — ALTERNATION OF SEXES 
63 
Discussion 
The alternative loss of maleness and femaleness in the flowers of Cleome 
spinosa and the recurring periodic changes in the sex of the flowers are to 
be regarded as phenomena of internal and biogenetic regulation closely 
related to those influences which determine the development of the plant 
as a whole. 
It is, of course, well recognized that in plants as contrasted with animals 
there is continually the formation of really new organs from a persistent 
embryonic complex of cells and that this continues until the maturity and 
death of the plant as a whole. Internal and biogenetic relations of corre¬ 
lation and self-regulation, operating independently or in response to external 
influences, are hence repeated successively in determining the character of 
the new organs in the same fashion as they operate once for all in the animal. 
When there is in addition a long flowering period which overlaps and is 
coincident with the period of the most vigorous vegetative development, 
as is the condition in this robust annual Cleome spinosa , the conditions are 
most favorable for a study of the factors influencing the differentiation 
of sex. 
The fact that the loss of sex organs in the flowers of the spider flower is 
very decidedly one-sided and qualitative is of special significance. When 
the stamens are aborted the pistil is as a rule functional, and in many cases 
it is well developed; when the pistil is aborted the stamens are often highly 
developed and functional. Here, as is the rule in plants, intersexualism 
does not lead to sterility of the plant or of a flower as a whole. Not a 
flower was found in which the pistil and all the stamens were extremely 
aborted, and rather rarely was the abortion of one sex accompanied by 
the decided abortion of the other sex in the same flower. Abortion 
of pistils was frequently accompanied by irregular abortion among the 
various stamens of a flower, but the same irregularity in maleness was also 
seen for flowers in which there was no abortion of the pistil (see the flowers 
of fig. 4). While the expression of sex in at least half of the flowers of a 
plant is decidedly one-sided and alternative, it is not mutually exclusive, 
for on every plant many bisexual flowers are produced. 
It should be noted that the influences operate primarily and almost 
discriminatingly on the organs of sex. The pedicels, sepals, and petals are 
often uniformly well developed for all the types of flowers; but undersized 
flowers were to be seen (c of fig. 3, and d of fig. 4) in which the flower as a 
whole is undersized. Such cases, if more general, would suggest a direct 
relation to waning vigor and decreased food supply such as may be con¬ 
sidered to be the direct cause of undersized flowers and of loss of sex in 
gynomonoecious forms at the end of a period of bloom. That the conditions 
are more intricate in Cleome is evident, for in a marked degree the extreme 
variations in sex are independent of any other visible change and the various 
grades of intersexes are present from the beginning of bloom. 
