. Elementary biology; an introduction to the science of life. Biology. CHAPTER LVIII POLLENATION 356. Function of poUenation. We have learned that flowers are seed-producing structures, and that seed production takes place only after fertilization. But in seed plants (most of which are land plants) the parts of the organism which bear gametes are so situated that fertiliza- tion is possible only after pol- lenation ; that is, the transfer of pollen from the anthers to the stigma. In these plants re- production de- pends in a rather peculiar way upon cer- tain external factors. 357. Self-pollen
. Elementary biology; an introduction to the science of life. Biology. CHAPTER LVIII POLLENATION 356. Function of poUenation. We have learned that flowers are seed-producing structures, and that seed production takes place only after fertilization. But in seed plants (most of which are land plants) the parts of the organism which bear gametes are so situated that fertiliza- tion is possible only after pol- lenation ; that is, the transfer of pollen from the anthers to the stigma. In these plants re- production de- pends in a rather peculiar way upon cer- tain external factors. 357. Self-pollenation. In many plants the transfer of pollen is brought about by the growth movements of the parts of the flower. The style, in elongating, may bring the stigma into contact with the anthers; a movement of the corolla may push the stamen against the stigma ; the stalk of the flower 304. Fig. 135. Dimorphic flowers of Chinese primrose {Primula) In these plants there are two forms of flowers (hence the term dmiorphk). In form A the anthers are high and the stigma is low ; in form B the anthers are low and the stigma i^ high. The pollen from form A is prepotent for the pistil of form B, and vice versa. That is, long-stamen pollen must reach long-style pistil, and short-stamen pollen must reach short-style pistil, to produce the best or the most seeds. This necessitates cross pollenation, or at any rate handicaps close pollenation. 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 Gruenberg, Benjamin C. (Benjamin Charles), 1875-1965. Boston New York [etc. ] Ginn and company
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