114 MENDELISM chap. 



Sex also occurs among plants but the conditions 

 here are more complicated. Generally speaking, 

 the higher plants are hermaphrodites, both ovules 

 and pollen occurring on the same flower. Some 

 plants, however, like most animals, are of separate 

 sexes, a single plant bearing only male or female 

 flowers. In other plants, as in certain Begonias 

 for example, the separate flowers are either male 

 or female, though both are borne on the same 

 individual. In others, again, the conditions are 

 even more complex, for the same plant may bear 

 flowers of three kinds, viz. male, female, and herma- 

 phrodite. Or it may be that two or three forms 

 occur in the same species, but in different individuals 

 — females and hermaphrodites in one species ; males, 

 females, and hermaphrodites in another. In com- 

 parison with animals, little experimental work has 

 been done with plants in connection with the nature 

 of sex, and we can hardly be said to have begun 

 to understand the relation of the different forms 

 to one another. A few well-established facts, 

 however, are not without interest. In many plants, 

 nominally hermaphrodite, individuals occur in which 

 the anthers are more or less aborted and fail to 

 form pollen. Experimental investigation has shown 

 that in such cases there may be a simple Mendelian 

 relation between the hermaphrodite form with fertile 

 pollen and the female form. In the sweet-pea, and 

 probably in the carnation, the female behaves as a 

 simple recessive to the hermaphrodite ; in the 

 potato, however, the evidence points to the herma- 

 phrodite condition being recessive. 



In the sweet-pea there is another feature which 



