(6.) The Direction of the Embryo as respects the Pericarp.
Ascending, pointing to the apex.
Descending, pointing to the base.
Centripetal, pointing to the axis.
Centrifugal, pointing to the sides.
BOTANICAL CLASSIFICATION OF PLANTS
The living plants may be divided into two grand divisions—Flowering Plants and Flowerless Plants—with five main subdivisions, according to the complexity and structure of their reproductive organs, or seed structure. The scientific names of these groups are the Thallophyta, the Bryophyta, the Pteridophyta, the Gymnosperms, and the Angiosperms.
Each of the five main groups is divided into a number of lesser subdivisions, sometimes called phyla, orders, each of which is composed of several families.
Most systematic botanists begin the study of plants with the lowest forms of plants and proceed to the highest. In the following classification, however, the usual order has been reversed because of its greater interest for a large majority of readers; the highest division is placed first and the lowest last.
In the earlier days of the science of botany nearly every botanist’s energies were devoted to this branch which we now call systematic botany. There are now named and described close on a quarter of a million of living species of plants altogether, including the lower and often nearly invisible forms, and of this vast number about one hundred and thirty thousand belong to the highest group of all—the Angiosperms. With nearly a quarter of a million described forms to deal with the value of such keys will be recognized.