CHANGES OF THE LEAF IN TROPICAL LANDS. 199 



or for men and the casting off of the foliage will 

 thus represent the putting off the garments of the day 

 preparatory to taking that rest which night was 

 intended by Nature to bring, with some exceptions, to 

 all animated nature. 



Of the sleep of plants we have spoken elsewhere, 

 and hibernation or winter sleep, which as we know is 

 sometimes found to occur in animals as well as in 

 plants, is merely another, though much more prolonged 

 form of sleep, during which the vital energies of deci- 

 duous vegetation are in a state of rest, preparatory 

 for the great awakening of Nature's functions which 

 occurs upon the advent of spring. This period of rest 

 is, as we believe, both necessary and common to 

 vegetation of every description and locality, though to 

 outward appearance such may not always be evident ; 

 the casting oif of foliage in like manner is common 

 to all sorts of trees and plants, though as in the case 

 of pines, and other evergreens, it is effected so gradu- 

 ally that it is the dead pine needles that cover the 

 ground beneath these trees which alone convince the 

 ordinary observer that the foliage falls at all. So, in 

 the great equatorial forests, the same phenomena 

 occur ; leaves are continually throughout the year, both 

 falling and sprouting, and there can be no doubt that 

 a period of rest takes place there also, though the 

 exact nature of it may not be apparent, nor well 

 understood. In tropical countries however, as we have 

 before pointed out, it is a well ascertained fact that 

 the rest of plants is often produced by intense solar 

 heat, very much in the same way as it is produced 

 in temperate regions by cold; leaves fall, and 

 growth is arrested, exactly as it is by winter and 



