bloomed, a little earlier, and yielded more seed than their parents. The two parent plants, or animals, must not, however, be exactly alike. Since then, says Dr. Fletcher, endless observations have confirmed the accuracy of Darwin's law, and it has been found that, in the majority of plants, special appliances exist which will secure more or less frequent intercrossing.
Plants have various means by which they prevent self-pollination or self-fertilization. The more important ways in which this is accomplished is given as follows:
I. Separation of stamens and pistils by space.
1) Stamens and pistils in different flowers, but on thesame plant.
2) Stamens and pistils in different flowers and on differentplants.
3) Stamens longer than the pistils, or pistils longer thanthe stamens.
4) Stamens bent away from the pistils, or pistils bent away from the stamens.
II. Separation of stamens and pistils by time.
1) Anthers maturing before the stigmas.
2) Stigmas maturing before the anthers.
III. Mechanical separation of the stamens and pistils.
1) Absolute separation; anthers or pollen masses held in a fixed position, and never set free unless the flower is visited by insects.
2) Partial separation; self-pollination may occur during the latter part of the blooming period.
IV. Physiological separation of the stamens and pistils.
1) Stamens aborted in some flowers, pistils in others.
2) Pollen from a different flower prepotent over pollen fromthe same flower.