. Foundations of botany. nce it is essen-tial to the health and rapid growth of most plants thatthey should have free access ^_ ,^/f^^ to the sun and air, it is notstrange that many shouldresort to special devices forlifting themselves abovetheir neighbors. In tropi-cal forests, where the dark-ness of the shade anywherebeneath the tree-tops is sogreat that few floweringplants can thrive in it, theclimbing plants or lianasoften run like great cablesfor hundreds of feet beforethey can emerge into the sun-shine above. In temperateclimates no such remarkableclimbers are found, but manyplants raise
. Foundations of botany. nce it is essen-tial to the health and rapid growth of most plants thatthey should have free access ^_ ,^/f^^ to the sun and air, it is notstrange that many shouldresort to special devices forlifting themselves abovetheir neighbors. In tropi-cal forests, where the dark-ness of the shade anywherebeneath the tree-tops is sogreat that few floweringplants can thrive in it, theclimbing plants or lianasoften run like great cablesfor hundreds of feet beforethey can emerge into the sun-shine above. In temperateclimates no such remarkableclimbers are found, but manyplants raise themselves forconsiderable distances. Theprincipal means to which they resort for this purpose are : (1) Producing roots at many points along the stemabove ground and climbing on suitable objects by meansof these, as in the English ivy (Fig. 15). (2) Laying hold of objects by means of tendrils ortwining branches or leaf-stalks^ as shown in Figs. 40, 41. 1 See Kerner and Olivers Natural History of Plants, Vol. I, p. Fig. 39. —Lianas strangling a Palm. 74 FOUNDATIONS OF BOTANY (3) Twining about any slender upright support, asshown in Fig. 42. 89. Tendril-Climbers. — The plants which climb bymeans of tendrils are important subjects for study, butthey cannot usually be managed very well in the school-room. Continued observation soon shows that the tips of tendrils sweep slowly about inthe air until they come in contactwith some object about whichthey can coil themselves. Afterthe tendril has taken a few turnsabout its support, the free part ofthe tendril coils into a spiral andthus draws the whole stem towardthe point of attachment, as shownin Fig. 40. Some tendrils aremodified leaves or stipules, asshown in Fig. 104 ; others aremodified stems. 90. Twiners. — Only a few ofthe upper internodes of the stemof a twiner are concerned in pro-ducing the movements of the tipof the stem. This is kept revolving in an elliptical orcircular path until it encounters some roughish a
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