CLASSIFICATION OF PLANTS. 201 
the Oak, the Box-tree, Maize, and Castor Oil-plant belongs indi- 
cates. They are monaceous, and form the twenty-first of the Linnean 
classes. 
The male and female flowers are found upon two distinct indi- 
viduals. There is a duality of habitation, as the name of the class 
Fig. 288.—Linneus. 
to which Mercurialis, the Date, and the Willow belong, indicates. 
This is the class Diece#, and the twenty-second. 
A class which is only a combination of the two preceding groups 
includes the plants which present upon one or many individuals 
male, female, and hermaphrodite flowers. This is the twenty- 
third class, said to be Polygamous, on which we find ranged the 
Ash, the Pelitory, and the Nettlé-tree. 
