'Recruited from the American Journal of Botany, X: 57-66, February, 1923.] 



LIBRARY 



NEW YORK 



BOTANICAL 



GARDEN 



ALTERNATION OF SEXES AND INTERMITTENT 



PRODUCTION OF FRUIT IN THE SPIDER 



FLOWER (CLEOME SPINOSA) 1 



A. B. Stout 



(Received for publication April 6, 1922) 



Irregularities in the formation of reproductive organs, such as are seen 

 in the phenomena of intersexualism in both plants and animals, have two 

 points of special interest. First, they involve a particular type of sterility 

 of various grades and degrees of expression, which in plants often affects 

 the production of fruit and seeds and becomes a matter of practical im- 

 portance in respect' to crop production and in the breeding of various 

 economic plants. A second point of interest is in the bearing which the 

 phenomena of intersexualism have on questions of sex differentiation, the 

 alternation of sex, and the evolutionary tendencies in reproduction. 



In its general significance, several points regarding sterility from inter- 

 sexualism are clear. In plants it tends to the alternative development of 

 one or the other kind of sex organs, giving, in comparison to the fundamental 

 condition of hermaphroditism, a one-sided sterility. There is incomplete 

 development or abortion of one or the other of the sex organs which is 

 discriminating and which results in alternative development, with, however, 

 many grades in the relative development. Thus, in plants, the so-called 

 "sterile" intersexes are, in general, individuals that are predominantly male 

 and often highly functional as such. These individuals are sterile only in 

 the sense that they are fruitless. Also the so-called "self-sterile " individuals 

 and varieties of plants, as is well shown in the cultivated grapes in which 

 sterility from intersexualism is well marked, are predominantly female and 

 able to function feebly or not at all as males. They are productive of fruit 

 only when properly pollinated from male or hermaphroditic individuals. 

 Very seldom, if ever, is complete sexual impotence for a plant as a whole 

 seen as a condition of intersexualism, as is frequently the case in sterility 

 from hybridity. 



But in many cases of intersexualism in animals, to which attention has 

 recently been especially directed, the complete sterility of individuals is 

 very frequent. Here, however, the condition arises in dioecious forms and 

 involves the partial change of an organ from one sex to the other after 



1 Contribution from the New York Botanical Garden, No. 239. 



57 



