GERM-CELL HISTORY IN THE BROOK LAMPREY 97 



Some further examples of mixed sex among plants may be 

 given. Among the flowering plants some species are hermaphro- 

 ditic, others dioecious, and still others produce three kinds of 

 individuals, namely, males, females, and hermaphrodites, as, for 

 example, the sweet pea. In the strawberry three kinds of flow- 

 ers are produced, staminate, pistillate, and perfect. Valleau ('16) 

 has investigated the inheritance of sex in grapes, and his results 

 are as follows : The wild grape develops two kinds of individuals, 

 staminate and pistillate, and both possess flowers of the opposite 

 sex in a suppressed condition. The grape, therefore, occupies an 

 intermediate position between purely dioecious plants, like the 

 willow, and purely monoecious plants, like the apple. On individ- 

 ual plants of the grape all gradations are sometimes found, from 

 staminate to functionally hermaphroditic flowers, and sometimes 

 only hermaphroditic flowers are produced. Certain clusters of the 

 vine may be entirely staminate, while other clusters on the same 

 vine contain all gradations from staminate to functionally perfect 

 flowers. In the grape, therefore, both staminate and pistillate 

 vines carry the determiners for femaleness and maleness, respec- 

 tively, but with one or the other partially suppressed. Valleau 

 draws the conclusion that, if the chromosomes carry the deter- 

 miners for sex, then in hermaphroditic plants the determiners for 

 maleness and femaleness must be carried in the same chromosome. 

 There are two possibihties, therefore, for the origin of functional 

 hermaphrodites. The maleness may express itself fully in one 

 of the chromosomes bearing the determiners for femaleness in a 

 pistillate plant and femaleness may express itself similarly in 

 staminate plants. 



Pritchard ('16) discusses the change of sex in hemp. Hemp is 

 dioecious, and the female plant is distinguished by its dense foli- 

 age as well as by the production of female flowers. The male 

 plants have very scanty foliage. The sex ratio is normally 1:1. 

 Hermaphroditic individuals appear in small numbers, but they 

 are of the female type and predominantly female in flower devel- 

 opment. Disturbances in the plant's physiological equilibrium 

 were induced by the removal of flowers and of vegetative parts, 

 as well as by the injection of various chemicals into the stem. 



