. A textbook of botany for colleges and universities ... Botany. 872 ECOLOGY flowers are more ephemeral than are diurnal flowers (as in the night- blooming cereus), but the flowers of evening primroses, although opening but once, remain open for some hours after sunrise; the flowers of some species of Silene open for at least three successive nights. Flowers often have a longer period of anthesis in spring and autumn than in summer; even ff "^'^'m^^^^ WiWi ^ ^^^^ ephemeral flowers as those of Hibiscus Trionum and Hemerocallis fidva may open toward the beginning or the end of the flowering
. A textbook of botany for colleges and universities ... Botany. 872 ECOLOGY flowers are more ephemeral than are diurnal flowers (as in the night- blooming cereus), but the flowers of evening primroses, although opening but once, remain open for some hours after sunrise; the flowers of some species of Silene open for at least three successive nights. Flowers often have a longer period of anthesis in spring and autumn than in summer; even ff "^'^'m^^^^ WiWi ^ ^^^^ ephemeral flowers as those of Hibiscus Trionum and Hemerocallis fidva may open toward the beginning or the end of the flowering period on three successive days. Flowers cannot be classed simply as diurnal or nocturnal, since most hours of the day and night are marked by the opening or closing of the flowers of some species. The opening and the closing hours of a given species vary widely with the lati- tude and the season, but in general the earlier diurnal flowers open about sunrise (as in the chicory and the morning glory) and the later about noon (as in Mesemhrianthemum). The nocturnal series begins about dusk (as in Silene) and closes about ten (as in Cereus). The times of closing are much less definite than are those of opening, and they extend over most of the twenty-four hours; this is partly because flowers open much more rapidly than they close, the former process sometimes being sudden, as in Oenothera. Begin- ning with the early forenoon (as in salsify and chicory) each hour until after sunset is marked by. Figs. 1193, 1194- — Floral opening and closing in the dan- delion (Taraxacum oifficinale): 1193, an open head as seen in full sunlight; 1194, the same head as seen at night; the invo- lucre (j) is double, consisting of short outer bracts (ft) and a single row of long inner bracts (6'); opening and closing are due chiefly to the movements of the inner bracts, the position of the outer bracts shifting but slightly. the closing of some diurnal flowers. Similarly nocturnal flowers may close
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
