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Bailey, Plant Breeding. The Macmillan Company.
Campbell, Lectures on the Evolution of Plants. The Macmillan Company.
Coulter, Barnes, and Cowles, A Textbook of Botany, Part II. American Book Company.
Darwin, Different Forms of Flowers on Plants of the Same Species. Appleton.
Darwin, Fertilization in the Vegetable Kingdom, Chaps. I and II. Appleton.
Darwin, Orchids Fertilized by Insects. D. Appleton and Company.
Müller, The Fertilization of Flowers. The Macmillan Company.