Nature and development of plants . so sharply characterized orders as incase of the monocotyledons, or in the following group of Sym-petalae. Furthermore, these orders doubtless represent manyparallel lines of development that are imperfectly this reason, the order of the presentation in the followingpages does not attempt to represent the real relationship of thegroups. 138. Salicales, the Willow and Poplar Order.—The willowsare almost universally distributed along water ways, apparentlydemanding for their existence only light and water. The poplarsare less restricted and some
Nature and development of plants . so sharply characterized orders as incase of the monocotyledons, or in the following group of Sym-petalae. Furthermore, these orders doubtless represent manyparallel lines of development that are imperfectly this reason, the order of the presentation in the followingpages does not attempt to represent the real relationship of thegroups. 138. Salicales, the Willow and Poplar Order.—The willowsare almost universally distributed along water ways, apparentlydemanding for their existence only light and water. The poplarsare less restricted and some can endure moderately arid condi- DEVELOPMENT OF PLANTS 397 tions. Few plants have greater vitality. A bit of a twig andoften a portion of a root is capable of developing buds and sostarting the shoot. Trees are often pointed out that have origi-nated through the careless sticking of a twig in the soil andseveral of the willows are naturally propagated by their twigswhich are easilv broken off bv the winds. Their unusual ability. Fig. 297. Flowers and seed of the willow (Salix) : A, winter appear-ance of a flowering twig, each boat-shaped scale concealing an , pussy willow stage of flowering, the aments emerging from the scalesand exposing the hairy bracts that conceal the flowers. C, ament of pis-tillate flowers in full bloom. D, pistillate flower, consisting of a compoundpistil of two carpels—b, bract; ;;, nectar gland. E, ament of staminateflowers. F, staminate flower of two stamens. G, ament of mature pistilswhich are opening to discharge the seeds. H-I, successive stages in theopening of the pistil. /, a seed with circle of hairs at base forming a para-chute for dissemination. to form numerous buds is well shown in the pollarded willowswhere the branches have been cut back and a large number ofshoots develop about the wound. Perhaps the stimulus of thewound also awakens some of the dormant buds (page 100). Theflowers, as in Typha, are arranged on an elongated ax
Size: 1741px × 1436px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectplants
