PERSPIRATION OF PLANTS. £ 



riments) to separate from their lower membrane j 

 which in this plant, as also in the leaves of Buxus 

 sempervirens, is found entirely detached by the 

 spring — a circumstance at no season incident to the 

 wall-rue. 



In cases in which it is difficult to perform the 

 operation, the following method succeeded best 

 with me : I introduced a very thin sharp-pointed 

 knife, its edge turned towards me, for several lines 

 beneath this tender membrane, and cutting it, I 

 took hold of the detached part with a pair of 

 small pliers, arid drew it softly upwards.-— If it still 

 proved inseparable, even by this method, or too 

 great a portion of the parenchyma of the leaf 

 adhered to it, recourse was had to maceration. 



The epidermis of some plants is so very fine and 

 tender, that, when detached, it collapses and ap- 

 pears a mucilaginous mass; in others, more elastic, 

 it rolls up immediately after separation. Frequently, 

 the membrane already detached, loosing its natural 

 means of expansion, becomes wrinkled, by which, 

 in addition to the moisture that usually remains, 

 the minuter objects contained in it appear but in- 



