Page:Popular Science Monthly Volume 41.djvu/183

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By C. V. RILEY, Ph. D.

THE common belief, based upon the theological assumption that all things upon this terrestrial sphere are for man's especial benefit, was, and perhaps yet is, that flowers were endowed with beauty and fragrance for our particular pleasure. Let us look somewhat more closely into this matter, and see what modern science has to say about it. Ever since Linnæus used the sexual characteristics of flowers in classification, and Erasmus Darwin sang of the loves of the plants, the philosophy of fertilization in the plant kingdom has been fairly apprehended. It has long been recognized that plants are divisible into homomorphic or self-fertilizable, and heteromorphic or cross-fertilizable species. All diclinous plants, or those having separate male and female flowers, belong to the latter category, which is further classifiable according to the means by which cross-fertilization is effected. One class (termed anemophilæ) depend almost entirely on the wind, and in these, of which our pines and other conifers, our poplars, willows, grasses, etc., are examples, the pollen or male element obtains in enormous quantities, is easily detached, and is generally produced early in spring, when winds prevail, and frequently before the development of the leaves, which would tend to impede its dispersion. The flower is inconspicuous and the stigma or female organ generally branched or hairy, so as to increase the chance of catching the wind-borne pollen. Water is an agency in the fertilization of a few plants, of which the singular Vallisneria is a striking illustration; while a few are aided by birds and higher animals; but by far the greater number are fertilized, or, more strictly speaking, pollinized, by insects.

The most casual observer of Nature must have appreciated, years ago, the fact that flowers are very important to insects, furnishing the essentials of life to those of several orders, and especially to the Hymenoptera (bees, wasps, etc.) and Lepidoptera (butterflies and moths) in the form either of pollen or nectar. But that insects could be of any especial benefit to plants has only come to be acknowledged and fully appreciated of late years. Toward the close of the last century Christian Konrad Sprengel published an important work—Das entdeckte Geheimniss der Natur—in which he maintained that the color, form, odor, secretions, and the general structure of flowers had reference to insects which are essential as pollinizers. The importance of insects as

  1. Adapted from advance sheets of the Annual Report of the Missouri Botanical Garden for 1891.