. A textbook of botany for colleges and universities ... Botany. REPRODUCTION AND DISPERSAL 837 as protandry; both protandry and protogyny are seen in maize. The most special- ized means of preventing close pollination, namely, that in which the pollen is impotent on the stigma of the same flower, is illustrated in rye, though in wheat and barley, and probably in most monoclinous species, close pollination is not necessarily excluded. Miscellaneous features of wind- pollinated flowers. — Wind-polli- nated flowers usually contrast with those that are insect-pollinated in their lack of showiness
. A textbook of botany for colleges and universities ... Botany. REPRODUCTION AND DISPERSAL 837 as protandry; both protandry and protogyny are seen in maize. The most special- ized means of preventing close pollination, namely, that in which the pollen is impotent on the stigma of the same flower, is illustrated in rye, though in wheat and barley, and probably in most monoclinous species, close pollination is not necessarily excluded. Miscellaneous features of wind- pollinated flowers. — Wind-polli- nated flowers usually contrast with those that are insect-pollinated in their lack of showiness, odor, and nectar, though some of them are conspicuously colored (as in the Cottonwood and field sorrel). The perianth mostly is inconspicu- ous (either through its greenish or brownish color or its small size) and often it is absent; when pres- ent, it consists commonly of a calyx, the corolla being rarely in evidence. None of these features would occasion comment, but for the corresponding presence of showiness, odor, and nectar in insect-pollinated flowers and for the consequent assumption that in the latter these features prob- ably are advantageous. The dis- tribution of species with wind-pol- linated flowers has been thought to differ somewhat from that of other seed plants. For example, the percentage of the former is greater in windy habitats than elsewhere (as on small islands and along shores), while the flowers <n 0 r^ . 1. Fig. 1165. — Pollination in the tape grass (Vallisneria spiralis); s, staminate plant; p, pis- tillate plant; the staminate flowers are borne in a spike (k); upon detachment they rise (a) to the surface, open out (b), and float on the water; the pistillate flowers (/) are borne in spathes (d) on long scapes (e), just reaching the water surface, where the floating staminate flowers may come in contact with them (c); note also the vertical ribbon- like leaves (l) and the stolon (r), 0 representing a new potential plant or offset. — After K
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
