. Essentials of botany. Botany; Botany. ECOLOGY OF FLOWERS; POLLINATION 175 Many flowers which appear to be designed to secure self-pollination are almost or quite incapable of it. Fre- quently the pollen from another plant of the same species prevails over that which the flower may shed on its own pistil, so that when both kinds are placed on the stigma together it is the foreign pollen which fertilizes. 209. Dichogamy; Movements of Stamens. — If the sta- mens mature at a different time from the pistils, self- pollination is as effectually prevented as though the plant were dioecious. This un
. Essentials of botany. Botany; Botany. ECOLOGY OF FLOWERS; POLLINATION 175 Many flowers which appear to be designed to secure self-pollination are almost or quite incapable of it. Fre- quently the pollen from another plant of the same species prevails over that which the flower may shed on its own pistil, so that when both kinds are placed on the stigma together it is the foreign pollen which fertilizes. 209. Dichogamy; Movements of Stamens. — If the sta- mens mature at a different time from the pistils, self- pollination is as effectually prevented as though the plant were dioecious. This unequal maturing, or di- c}ix)gamy, occurs in many kinds of flowers. In some, the figwort and the com- mon plantain for example, the pistil develops before the stamens, but usually the reverse is the case. The Clerodendron,^ a tropical African flower (Fig. 131), illustrates in a most strik- ing way the development of stamens before the pistil. Besides the slow move- ments which the stamens and pistil make in such cases as that of the Clerodendron, the parts of the flower often, as in the barberry and Kalmia, admit of extensive and rather quick movements to assist the insect visitor to become dusted or smeared with pollen. I C Fig. 131. Flower of Clerodendron in Two Stages. In A (earlier stage) the stamens are ma- ture, while the pistil is still undevel- oped and bent to one side. In B (later stage) the stamens have withered and the stigmas have separated, ready for the reception of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn
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