. A textbook of botany for colleges and universities ... Botany. 874 ECOLOGY than the closure of perianth segments is effected by low temperature, a few seconds commonly sufficing. Such closure is of direct value in protecting pollen from rain. It may be recalled, also, that in anthers, dehiscence generally is caused by desiccation, so that the first opening is unlikely to occur in wet weather. Many plants show movements of the flower axes (pedi- cels) or inflorescence axes (peduncles). In certain instances the buds are erect and the flowers pendent (as in AquUegia). More closely related to fl
. A textbook of botany for colleges and universities ... Botany. 874 ECOLOGY than the closure of perianth segments is effected by low temperature, a few seconds commonly sufficing. Such closure is of direct value in protecting pollen from rain. It may be recalled, also, that in anthers, dehiscence generally is caused by desiccation, so that the first opening is unlikely to occur in wet weather. Many plants show movements of the flower axes (pedi- cels) or inflorescence axes (peduncles). In certain instances the buds are erect and the flowers pendent (as in AquUegia). More closely related to floral movements are those cases in which the flower is erect by day and pendent by night and in rainy weather (as in Geranium and Anemone); in the um- bellifers there is a simi- lar movement of the entire inflorescence. Such movements are due to growth inequali- ties in the pedicels or the peduncles, and the advantages therefrom would appear to be in. Figs. 1195-1197. — Growth movements accompany- ing flower and fruit development in a wild onion {Allium cernuum): 119S, a flower bud, showing the nodding posi- tion of the young peduncle (p); b, spathe; 1196, a shoot in full bloom; note that the peduncle {p) has straightened out except at the tip ((); the flowers are arranged in an umbel, the pedicels {p') being oriented in various direc- tions; note the exserted stamens (j); 1197, a shoot in fruit, showing the conspicuous capsules (c); note that the pedicels (/»') have become erect or ascending. exposure to pollinating insects in sunshine, and in protection from rain and cold during the night or in rainy weather. In the poppy the buds are nodding, but the flowers are erect, the pedicels becoming apogeotropic. Movements of much complexity, but without obvious advantages, are seen in Allium cernuum (figs. 1195-1197), where the nodding bud becomes erect by differential growth in the peduncle, while later the fruits become erect by similar growth in the pedicels. Protection during
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