CIIAP. VII. POLYGAMOUS PLANTS. 295 



the pistils in the males. The pistil varies consi- 

 derably in length in the female plants, so that they 

 may be divided into two sub-forms according to the 



Fig. 14. 



Long-styled Short-styled 

 female. female. 



RHAMNUS CATHARTICUS. 



length of this organ. Both the petals and sepals ara 

 decidedly smaller in the females than in the males ; 

 and the sepals do not turn downwards, as do those of 

 the male flowers when mature. All the flowers on the 

 same male or same female bush, though subject to 

 some variability, belong to the same sub-form ; and 

 as my son never experienced any difficulty in decid- 

 ing under which class a plant ought to be included, 

 he believes that the two sub-forms of the same sex 

 do not graduate into one another. I can form no 

 satisfactory theory howihe four forms of this plant 

 originated. 



Rhamnus lanceolatus exists in the United States, 

 as I am informed by Professor Asa Gray, under two 

 hermaphrodite forms. In the one, which may be called 

 the short-styled, the flowers are sub-solitary, and in- 

 clude a pistil about two-thirds or only half as long as 

 that in the other form ; it has also shorter stigmas. The 

 stamens are of equal length in the two forms ; but the 

 anthers of the short-styled contain rather less pollen, 

 as far as I could judge from a few dried flowers. My 



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