CK-12 Foundation
Ck 12: Biology: Flowering Plants
[Free Registration/Login may be required to access all resource tools.] Describes the parts of a flower and the classification and evolution of flowering plants.
BiologyWise
Biology Wise: Monocot vs. Dicot
One way plants have been classified has been based on the number of cotyledons in the seeds. The differences between monocots and dicots are listed along with some helpful facts.