The natural history of plants, their forms, growth, reproduction, and distribution; . ove the ground from their subterraneanperennial portions several shoots. If these find no support in the ordinary way,they wind round one another, and a regular coil or cable is produced (cf. p. 364).These cables often rise without any foreign support to a considerable height abovethe ground, and thus single nutating apices are afforded the possibility of graspinga support which otherwise might have been denied them. Should all these methods prove of no avail the twisted stem takes up itsposition on the groun
The natural history of plants, their forms, growth, reproduction, and distribution; . ove the ground from their subterraneanperennial portions several shoots. If these find no support in the ordinary way,they wind round one another, and a regular coil or cable is produced (cf. p. 364).These cables often rise without any foreign support to a considerable height abovethe ground, and thus single nutating apices are afforded the possibility of graspinga support which otherwise might have been denied them. Should all these methods prove of no avail the twisted stem takes up itsposition on the ground; its growth is retarded, and it has the appearance of astunted, sickly plant. This fact is in so far interesting because it seems to indicatethat the pressure experienced by a twining stem adhering to a supporting prop has 688 CLIMBING PLANTS. a favourable influence on the growth of the shoot as a whole. This pressi^e mustbe regarded as a stimulus, just like the pressure which incites the tendrils, to bedescribed below, to luxuriant growth. We may therefore conclude that twining. Fig. 160.—Twining Hop (Humulus Lupulus). > Free end of a shoot recently emerged above the ground. * Shoot of Hop twining round an elder-stem; natural size. « Aportion of the Hop stem magnified. *, s Single, anvil-shaped climbing-hooks detached from the stem; more highlymagnified. stems are irritable, although the irritability in this case is not so conspicuous as intendril-forming structures. In the temperate zones the majority of twining stems have only a short twining Polygonum is an annual; hops and bindweeds are indeed perennial,but their stems sent up fresh each year from the underground stock always perish I CLIMBING PLANTS. 689 in the following autumn. Only the Bitter-sweet (Solanum dulcamara) and severalspecies of honeysuckle { Lonicera caprifolium and Periclymenum), which existin comparatively inclement regions, possess twining stems which increase in thick-ness from year
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1902
