178 REVIEWS. 



velop thorn. This tendril can do nothing with a smooth post, 

 fails to attach itself to a brick wall, but is well adapted to 

 climb trees with rough and mossy bark. 



The Virginia Creeper also turns its tendrils from the light, 

 and, although they will occasionally clasp a slender support, 

 iu the manlier of its relative the Grapevine, they uniformly 

 seek dark crevices, or especially broad flat surfaces, as a wall, 

 a rock, or the trunk of a tree. Having brought their curved 

 tips into contact with such a surface, these swell and form, in 

 the course of a few days, the well-known disks or cushions by 

 which they firmly adhere. Here is a tendril-climber which 

 emulates a root-climber, such as the Ivy, in the facility with 

 which it ascends smooth trunks, rocks, or walls. 



A very short chapter is devoted to Hook-climbers and Root- 

 climbers. The stems of the latter are said to " have usually 

 no power of movement, not even from the light to the dark. 

 But Iloya carnosa, which twines, also climbs by rootlets 

 spreading over the face of a damp wall ; and Tecoma radi- 

 oing (our Trumpet Creeper) exhibits in its young shoots 

 some vestiges of the revolving power with which its twining 

 relatives are endowed." 



In a dozen pages of Concluding Remarks, Mr. Darwin 

 gives much interesting matter in the way of deduction and 

 speculation, which it would be difficult to condense into an 

 abstract. 



Plants become climbers, he remarks, in order to reach the 

 light, aud expose a large surface of leaves to its action and 

 that of the free air. Their advantage is, that they do this 

 with wonderfully little expenditure of organized matter in 

 comparison with trees, which have to support a heavy load 

 of branches by a massive trunk. Of the different sorts of 

 climbers hook-climbers are the least efficient, at least in tem- 

 perate countries, as they climb only in the midst of an en- 

 tangled mass of vegetation. Next root-climbers, which are 

 admirably adapted to ascend naked faces of rock ; but when 

 they climb trees they must keep much in the shade, and fol- 

 low the trunk ; for their rootlets, can adhere only by long- 

 continued and close contact with a steady surface. Thirdly, 



