the Orchis family. The Passion-flower is wrongly put by Linnæus and others into this Class, as its stamens merely grow out of an elongated receptacle or column supporting the Germen.
21. Monoecia. Stamens and Pistils in separate flowers, but both growing on the same plant, or, as the name expresses, dwelling in one house, as the Oak, Hazle, and Fir.
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.