CLASSES. 301 



22. DIOECIA. Stamens and Pistils not only in separate 

 flowers, but those flowers situated on two separate 

 plants, as in the Willow, Hop, Yew, &c. 



These two last Classes are natural when the 

 barren flowers have, besides the difference in their 

 essential organs, a different structure from the fertile 

 ones in other respects ; but not so when they have 

 the same structure, because then both organs are 

 liable to meet in the same flower. In some plants, 

 as Rhodiola, Engl. Bot. t. 508, each flower has 

 always the rudiments of the other organ, though 

 generally inefficient. 



23. POLYGAMIA. Stamens and Pistils separate in some 

 flowers, united in others, either on the same plant, 

 or on two or three different ones. 



This Class is natural only when the several flowers 

 have a different structure, as those of Atriplex\ but 

 in this genus the Pistil of the united flower scarcely 

 produces seed. If, with Linnaeus, we admit into 

 Polygamia every plant on which some separated 

 barren or fertile flowers may be found among the 

 united ones, while all agree in general structure, the 

 Class will be overwhelmed, especially with Indian 

 trees. I have therefore proposed that regard should 

 be had to their general structure, which removes all 

 such inconvenience, and renders the Class much 

 more natural. 



