Feb., 1923] STOUT — ALTERNATION OF SEXES 65 



purely staminate or pistillate, Cleome spinosa is like most species which are 

 in the transition stages toward dioecism. The alternate appearance of 

 male, female, and hermaphroditic flowers in a raceme of course favors cross- 

 ing, and when this alternation tends to be synchronous on all the branches 

 of a plant, selfing is largely prevented except in the case of the hermaph- 

 roditic flowers. 



In the spider flower, with its long flowering period and its alternation of 

 maleness and femaleness in the racemes, it is evident that practically the 

 whole vegetative feeding power of every plant is drawn upon for seed 

 production. The conditions are markedly different, and we may consider 

 them more highly adaptive to the demands of reproduction, than is the 

 case in strictly dioecious plants in which seed production is confined to one 

 of each pair of male and female plants. We may, perhaps, characterize the 

 sex conditions in Cleome spinosa as effecting a sort of super -dioecism in that 

 the conditions favor both reproduction and crossing for each individual. 



Certain points regarding the determination of sex in the flowers of 

 Cleome spinosa are clear. The conditions illustrate well the fact that the 

 morphological differentiations of sex are fundamentally an extension of the 

 phenomena of somatic differentiations. The expressions of differential 

 qualities in leaves, stems, and flowers, with further differentiation of calyx, 

 corolla, pistil, and stamens, with still further differentiations of tissue within 

 each, are all recognized as one-sided, qualitative, and alternative expressions 

 in protoplasmic units that are alike and which still remain alike in funda- 

 mental constitution. Even the physically qualitative division of germ 

 plasm in the reduction divisions is found in regeneration experiments and 

 in parthenogenesis not to be a direct and absolute condition in the alter- 

 nation of generations. The theory of sex chromosomes decidedly fails in 

 general application to plants, and even in animals, where its application 

 seems most marked, sex is often intergrading and reversible, showing that 

 there is alternative expression rather than alternative inheritance. 



In Cleome spinosa it is evident that there are rather special and perhaps 

 very specific stimulating and inhibiting influences which regulate the 

 development of the sex organs. Whether these influences are substantive 

 or more of the nature of stimuli, their action is cyclic and decidedly alter- 

 native. The results clearly show that sex of flowers is determined progres- 

 sively as they are formed in response to regulation by internal biogenetic 

 conditions. 



New York Botanical Garden 



LITERATURE CITED 

 Banta, A. M. 1916. Sex intergrades in a species of Crustacea. Proc. Nat. Acad. Sci. 



2: 578-583- 

 Goldschmidt, R., and Poppelbaum, H. 1914. Erblichkeitsstudien an Schmetterlingen II. 

 Zeitschr. Ind. Abst.- Vererbungsl. 11: 280-316. 



