. Cyclopedia of American horticulture, comprising suggestions for cultivation of horticultural plants, descriptions of the species of fruits, vegetables, flowers, and ornamental plants sold in the United States and Canada, together with geographical and biographical sketches. Gardening. POLLINATION 1389. 1874. Structure of the Flower, to illustrate Pollination. 1. Top.—The structure of a plum blossom: se. sepals; p. petals; ; o ovary; s. style; St. stigma. The pistil is composed of the ovai-y, style and stigma. It contains the female part. The stamens are tipped %vith anthers in wh
. Cyclopedia of American horticulture, comprising suggestions for cultivation of horticultural plants, descriptions of the species of fruits, vegetables, flowers, and ornamental plants sold in the United States and Canada, together with geographical and biographical sketches. Gardening. POLLINATION 1389. 1874. Structure of the Flower, to illustrate Pollination. 1. Top.—The structure of a plum blossom: se. sepals; p. petals; ; o ovary; s. style; St. stigma. The pistil is composed of the ovai-y, style and stigma. It contains the female part. The stamens are tipped %vith anthers in which the pollen, or male part, is borne. The ovary, o, ripens into the fruit. 2. ovary at a, 3 stamens (one is removed) and the projecting style. 3. Buttercup, showing many small pistils in the center and stamens surrounding them. 4. Bottom.—Phlox, showing the 3-parted stigma, and the stamens included iu the tube. continued cross-pollination by the first two means, but there is little evidence that the self-sterility now noticeable in plants was developed in this way. Self-sterility is not usu- ally due to a deficiency in the pollen or to defective pistils. The pollen grains often germinate on the stigma, but fertilization does not take place. The embryological I'casons for this are not clearly understood. About sixty species of plants are known to be more or less self-sterile. (4) The separa- tion of the sexes in different flowers or on different individuals. It is thought by some that there is a gradual evolution among some kinds of plants toward uni- sexuality, and that adaptations for insect- pollination, dichogamy and self - sterility are steps in this process. Self-sterility is common in varieties of orchard fruits, particularly in pears and plums, and in grapes. Whenever isolated trees or large blocks of a single variety blossom full, year after year, but drop most of the fruit before it is half-grown, the trees may be self - sterile, provided the fai
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