Frequent rotations seem to be the rule for many plants, when left to themselves in a state of nature. Confining to a permanent spot invites parasites and other enemies, and a depleted soil, while health and vigor are secured by frequent migrations. The more we study in detail the methods of plant dispersion, the more we shall come to agree with a statement made by Darwin concerning the devices for securing cross-fertilization of flowers, that they "transcend, in an incomparable degree, the contrivances and adaptations which the most fertile imagination of the most imaginative man could suggest with unlimited time at his disposal."[6] [Footnote 6: _Fertilization of Orchids_, p. 351.] Let no reader think that the topics here taken up are treated exhaustively, for if he will go over any part of this work and verify any observation or experiment, he will be sure to find something new, and very likely something different from what is here stated. BIBLIOGRAPHY. Means of Plant Dispersion. By E. J. HILL. _Am. Nat._ Vol. xvii, pp. 811, 1028. 1883. Why Certain Kinds of Timber Prevail in Certain Localities. By JOHN T. CAMPBELL. _Am. Nat._ Vol. xix, p. 337. 1885. Report of the U. S. Commissioner of Agriculture for 1888. Article on the "Food of Crows." By W. B. BARROWS. p. 498. Report of the U. S. Secretary of Agriculture for 1890. Article on "Seed Planting by Birds." By W. B. BARROWS. p. 280. Report of the U. S. Secretary of Agriculture for 1893. Article on "Food Habits of the Kingbird, or Bee Martin." By W. B. BARROWS. p. 233. Bulletin No. 6, U. S. Department of Agriculture. Division of Ornithology and Mammology. "The Common Crow of the United States." By W. B. BARROWS and E. A. SCHWARZ. 1895. Bulletin No. 7, U. S. Department of Agriculture. Division of Ornithology and Mammology. "Food of Woodpeckers." By F. E. L. BEAL. Causes of Forest Rotation. By JOHN T. CAMPBELL. _Am. Nat._ Vol. xx, p. 521. 1886. Seeds of the Violet and Other Plants as Projectiles. By MOSES N. ELROD, M.D. _Am. Nat._ Vol. xiii, p. 93. 1879. The Natural History of Plants. By KERNER and OLIVER. Henry Holt & Co., New York. 1895. Flowers, Fruits, and Leaves. By SIR JOHN LUBBOCK. Macmillan & Co., New York. Origin of Cultivated Plants. By ALPHONSE DE CANDOLLE. D. Appleton & Co., New York. Distribution of Weed Seeds by Winter Winds. By H. L. BOLLEY. Bulletin No. 17. Fargo, North Dakota. Weeds of California. By E. W. HILGARD. Report of the Experiment Station, pp. 238-266. 1890. Migration of Weeds. By L. H. DEWEY. Yearbook of the U. S. Department of Agriculture, pp. 263-286. 1896. Washington, D. C. Squirrels Carrying Nuts. _Nature_. Vol. xv, p. 117. Macmillan & Co., New York. Natural History of Plants. By KERNER and OLIVER. Distribution of Species. Vol. ii, pp. 790-885. Henry Holt & Co., New York. 1895.