HOME PLANTS AND THEIR WAYS. %\ 



16. As in the process of natural selection the hook- 

 climbers appear to have grown out of the twiners, the 

 question may occur, Why is hook-climbing a more perfect 

 method of climbing than turning ? Why, when a plant 

 had become a twining plant, did it not rest satisfied ? The 

 fact that leaf- and tendril-climbers had been developed out 

 of twiners, and not vice versa, is a proof that climbing by 

 leaves or tendrils is a more advantageous habit than twin- 

 ing ; but we do not see why it should be so. If we incpiire 

 why any plant has become a climber, we shall see the rea- 

 son. Light is a necessity for all green plants ; and a plant 

 which can climb is enabled to escape from the shadow of 

 other plants with a far less waste of material than a forest- 

 tree, which only pushes its branches into the light by sheer 

 growth. Thus, the weak, straggling stem of a climbing 

 plant gets all the advantages gained by the solid, column- 

 like tree-trunk. If we apply this test — which is the most 

 economical plan of climbing, twining or leaf-climbing — we 

 see at once that a plant which climbs by seizing wastes far 

 less material than one which twines. Thus, a kidney-bean, 

 which had climbed up a stick to a height of two feet, when 

 unwound from its support was found to be three feet in 

 length, whereas a pea which had climbed up two feet by its 

 tendrils was hardly longer than the height reached. Thus, 

 the bean had wasted considerably more material by its 

 method of climbing . by twining round a stick, instead of 

 going straight up, supported by its tendrils, like the pea. 



17. There are several other ways in which climbing by 

 tendrils is a much better plan than twining. It is a safer 

 method, as any one may convince himself by comparing 

 the security of a tendril-bearer in a heavy wind with the 

 ease with which a twiner is partly blown from its support. 

 Again, by looking at those leaf-climbing plants which still 

 possess in addition the power of twining, it will be seen 

 how incomparably better they grasp a stick than does a 



