CHAP. VII. POLYGAMOUS PLANTS. 295 



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 how the 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 



Fig. 14. 



Long-styled 

 female. 



RHAMNUS CATHAKTICUS. 



son compared the pollen-grains from the two form.?, 

 and those from the long-styled flowers were to those 

 from the short-styled, on an average from ten measure- 

 ments, as 10 to 9 in diameter; so that the two her- 

 maphrodite forms of this species resemble in this 

 respect the two male forms of R. catharticus. The long- 

 styled form is not so common as the short-styled. The 

 latter is said by Asa Gray to be the more fruitful 

 of the two, as might have been expected from its ap- 

 pearing to produce less pollen, and from the grains 



