Chat. V. CONCLUDJNQ BEMABKS. 189 



Goncluding Bemarks on Climbing Plants. 



Plants become climbers, in order, as it may be 

 presumed, to reach the light, and to expose a large 

 surface of their leaves to its action and to that of the 

 free air. This is eifected by climbers with wonderfully 

 little expenditure of organized matter, in comparison 

 with trees, which have to support a load of heavy 

 branches by a massive trunk. Hence, no doubt, it 

 arises that there are so many climbing plants in all 

 quarters of the world, belonging to so many different 

 orders. These plants have been arranged under four 

 classes, disregarding those which merely scramble over 

 bushes without any special aid. Hook-climbers are 

 the least efficient of all, at least in our temperate 

 countries, and can climb only in the midst of an 

 entangled mass of vegetation. Koot-climbers are 

 excellently adapted to ascend naked faces of rock 

 or trunks of trees ; when, however, they climb trunks 

 they are compelled to keep much in the shade; 

 they cannot pass from branch to branch and thus cover 

 the whole summit of a tree, for their rootlets require 

 long-continued and close contact with a steady surface 

 in order to adhere. The two great classes of twiners 

 and of plants with sensitive organs, namely, leaf- 

 climbers and tendril-bearers taken together, far exceed 

 in number and in the perfection of their mechanism the 

 climbers of the two first classes. Those which have 

 the power of spontaneously revolving and of grasping 

 objects with which they come in contact, easily pass 



