Biology Pages
Kimball's Biology Pages: Sexual Reproduction in Angiosperms (Flowering Plants)
This site, from retired Harvard professor John W. Kimball, provides a detailed but understandable explanation of sexual reproduction in flowering plants. Includes informative, well labelled illustrations.
Estrella Mountain Community College
Online Biology Book: Biological Diversity: Seed Plants
An in-depth reference explaining the role of seed plants in biological diversity. Photographs and labeled diagrams help learners with understanding.