Glimpses of the animate world; or, Science and literature of natural history, for school and home . Tendril Coil. and, since the end of the tendril is fixed to a branch, it isobvious that the stem must be dragged nearer to the objectwhich its tendril has caught. Thus, if a shoot of bryonyseizes a support above it, the contraction of the tendril willpull up the shoot in the right direction. So that in thisrespect the power of spiral contraction gives a tendril-climber an advantage over leaf-climbers which have no con-tracting power, and, therefore, no means of hauling them-selves up to supporti
Glimpses of the animate world; or, Science and literature of natural history, for school and home . Tendril Coil. and, since the end of the tendril is fixed to a branch, it isobvious that the stem must be dragged nearer to the objectwhich its tendril has caught. Thus, if a shoot of bryonyseizes a support above it, the contraction of the tendril willpull up the shoot in the right direction. So that in thisrespect the power of spiral contraction gives a tendril-climber an advantage over leaf-climbers which have no con-tracting power, and, therefore, no means of hauling them-selves up to supporting objects. 15. But the spiral contraction of tendrils has anotheruse, and this is probably the most important one. Thisuse depends on the fact that a contracted tendril acts likea spiral spring, and is thus converted into a yielding instead 22 NATURAL HISTORY READER. of an unyielding body. The spirally wound tendril yieldslike an elastic thread to a pull which would break the ten-dril in its original condition. The meaning of this arrange-. Coil and Dish. ment is to enable the plant to weather a gale which wouldtear it from its support by snapping the tendrils, if theywere not converted into spiral springs. After the tendrilhas taken hold of a support, spiral coils can be made in itonly by the middle part of the tendril turning, and thiswill cause the coils to be turned one half in one directionand one half in the other. HOME PLANTS AND THEIR WAYS. %\ 16. As in the process of natural selection the hook-climbers appear to have grown out of the twiners, thequestion may occur, Why is hook-climbing a more perfectmethod of climbing than turning ? Why, when a planthad become a twining plant, did it not rest satisfied ? Thefact that leaf- and tendril-climbers had been developed outof twiners, and not vice versa, is a proof that climbing byleaves or tendrils is a more advantageous habit than twin-ing ; but we do not see why it should be so. If we incpiirewhy any plant has become a cli
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