Traditionally, the flowering plants have been divided into two major groups, or classes,: the Dicots and the Monocots.
Many people take this separation into two classes for granted, because it is "plainly obvious", but botanists have not always recognized these as the two fundamental groups of angiosperms.
Although Theophrastus (circa 370 BC) is credited with first recognizing differences between the two groups, classification of plants was based upon overall growth form -- trees, herbs, vines -- until the 1600s.
Evolution Within the Flowering Plants
In 1682, John Ray published his Methodus Plantarum Nova, in which Dicotyledones and Monocotyledones were first given formal taxonomic standing.
This system was popularized by the French botanist Antoine Laurent de Jussieu in his Genera Plantarum of 1789, a work which improved upon, and gradually replaced, the system of plant classification devised by Linnaeus.
Linnaeus, in his ‘lapp phase’