From the preface: The method of slow improvement of agricultural varieties by repeated selection is losing its reliability and is being supplanted by the discovery of the high practical value of the elementary species, which may be isolated by a single choice. The appreciation of this principle will, no doubt soon change the whole aspect of agricultural plant breeding.

Contents: Preface. 1. Evolution and mutation. 2. The discovery of the elementary species of agricultural plants by Hjalmar Nilsson. 3. On corn breeding. 4. The production of horticultural Novelties/by Luther Burbank. 5. The association of characters in plant-breeding. 6. The geographical distribution of plants. Index.