FROM MIRBEL. 286 



out. The way that light acts upon this class of the 

 creation, is principally in separating the elementary 

 parts of the water and carbonic acid contained in them, 

 and in extricating the oxygen of the latter. The car- 

 bon of the acid, with the hydrogen and oxygen of the 

 water, form the bases of the gums, resins, and oils, 

 which flow in the vessels or fill the cells. Thes^ juices 

 nourish the membranes, and induce the woody state in 

 them ; and they do this in proportion as the light is 

 stronger and its action more prolonged. Thus we see 

 tha^ darkness and light have effects directly opposite up- 

 on "vegetables. Darkness favours the length of their 

 growth by keeping up the pliancy of their parts ; light 

 consolidates them, and stops growth by favouring nutri- 

 tion. It should follow that a fine race of vegetables, 

 one that unites in due proportion, size, and strength, 

 depends in part upon the proper reciprocation of nights 

 and days. Now in the northernmost regions, plants go 

 through all the stages of growth at a time when the sun 

 no longer quits the horizon ; and the light, of which 

 they experience the unremitting effect, hardens them 

 before they have time to lengthen. So their growth ie 

 quick, but of short duration ; they are robust, but un- 

 dersized. 



The same plants, when transplanted into milder re- 

 gions, where the atmosphere is moist, and light and 

 darkness follow in regular succession ; if they are but 

 endowed with a frame of sufficient pliancy to support 

 their new mode of existence, are seen to lengthen their 

 stems, expand their branches, as well as multipy, di- 

 late, and soften their leaves. 



Vegetation, in ascending above the level of the sea, 

 undergoes modifications analagous to those which attend 

 its progress from the line to either pole ; with this 



