With flowers of one petal.
XX. Trees with a regular or irregular corolla of one piece; as the lilac.
With regular flowers of several petals.
XXI. Trees or Shrubs with rosaceous corolla; as the apple-tree.
With irregular flowers of several petals.
XXII. Trees or Shrubs with papilionaceous corolla; as the laburnum.
Each of these classes is subdivided into various sections or orders, founded upon modifications in the form of the corolla, the nature of the fruit, the figure of the leaves, &c. The sections contain a greater or less number of genera, under which are disposed all the species known to the author.
This classification was of the greatest service to botanists; though it was, like every other method that had been proposed, defective in many respects. A great objection to it is, that it separates the herbaceous from the woody plants, thus tearing asunder the most natural connexions; nor is the form of the corolla always so determinate, that one can say whether it be bell-shaped, funnel-shaped, or salver-shaped,—a point which it is necessary to decide before the species can be made out. Various changes were soon proposed, and new methods planned, so that the science was again falling into confusion, when Linnæus published his system, which was presently adopted by many teachers, and long before his death was in general use.
He made the stamina and pistils the basis of his arrangement, which he was induced to do from the consideration of their great importance, as the parts most essential to fructification. These organs being analogous to those distinguishing the sexes of animals, the Linnæan method is sometimes called the sexual system. It consists of twenty-four classes. The first ten are determined by the number of the stamina.
Class I. Monandria, containing all plants of which the flowers have only one stamen; as the mare's tail.