Allen, Grant: The Colour of Flowers.

Aveblry, Lord: Flowers, Fruits, and Leaves.

Beale, W. J.: Birds.

Behrens, W. J.: Blumen u. Insekten.

Darwin, C: Cross- and Self-pollination.

Darwin, C: Fertilization of Orchids.

Darwin, C.: Forms of Flowers.

Guppy, H. B.: Studies on Fruits and Seeds.

Henslow, G.: The Making of Flowers.

Hildebrand, F.: Die Farben der Bliiten.

Kerner von Marilaun, A., and Oliver, F. W.: The Natural History of Plants.

Kerner von Marilaun, A.: Flowers and their Unbidden Guests.

Knuth, P.: Flower Pollination.

Muller, H.: Fertilization of Flowers (full Bibliography).

Riley, C. V.: Monograph on Yucca Pollination.

Sprengel, C. K.: Entdecktes Geheimnis der Natur.

Trelease, W.: Fertilization of Flowers by Humming Birds.

Wallace, Sir A. R.: Darwinism.