THE STOMATA. 77 



is performed by them. It is from not lla^dng made this 

 distinction, that incorrect objections have been made 

 against this theory ; which Hedwig first indicated in 1793 ; 

 which I established in 1801 ; and which has been since 

 confirmed in 180^ by Sprengel, and in 1807 by Link 

 and Rudolphi. 



The contrary opinion has been maintained by Schrank, 

 who thinks that the stomata are employed to draw mois- 

 ture from the air. I believe that the absorption of 

 aqueous vapours by the leaves is a phenomenon either 

 rare, or contrary to the natural course of vegetation : 

 the plants where this is most striking are the aquatic 

 Algas, which evidently absorb the circumambient water 

 by their whole surface ; but these plants have no stomata, 

 and, consequently, this example would prove contrary 

 to this opinion. ' Among vascular plants, those in which 

 the absorption of water appears most evident are those 

 of a succulent nature, which, as we know, live for a long 

 time when separated from their root, seeming as if they 

 were nourished by the air. I am assured by expe- 

 riments, that these plants constantly lose weight when 

 they are suspended in a sheltered place, but that if they 

 are then plunged into water, or are exposed to rain, 

 they regain, in a very short time, all the weight which 

 they had lost : therefore the stomata, in their ordinary 

 state, do not abstract moistvire from the air ; but withered 

 or faded leaves absorb water which is in contact with 

 them. Is this by the simple hygroscopicity of the tissue, 

 or by the stomata ? There are circumstances which may 

 favour this last opinion. 



Bonnet has seen that certain leaves are able to live by 

 having water applied to one or both of their surfaces ; 

 and it seems evident, from these experiments, that they 

 absorb the water by the surface in contact with the 

 fluid ; for, in order that the leaf may live, the face which 



