IN THE VEGETABLE KINGDOM. 189 



tion their mineral constituents. When we reflect that no plant 

 can exist independently of certain mineral constituents) and that 

 these occur only in certain definite quantities, and that some bases 

 only, such as soda or potash, lime or magnesia, occur in plants, 

 and when, finally, we observe that these mineral substances are 

 accumulated in very different proportions in the various organs 

 of plants, and in accordance with the different periods of their 

 development, although they present tolerably uniform relations 

 under similar conditions and in identical organs, we are necessarily 

 led to the idea that these substances exert a definite influence 

 upon the life of the whole plant, and upon the origin of its organic 

 constituents from carbonic acid, water, and ammonia. 



The bases we have enumerated are generally found in the ash 

 combined with carbonic acid, although in the living plant they 

 more commonly occur in combination with organic acids, as 

 neutral or acid salts. Liebig, in his notice of these substances, 

 has drawn attention to two much-disputed points of discussion : 

 whether one base may be replaced by another in a plant, and 

 whether the sum of the oxygen contained in the base is always 

 one and the same for each species of plants. Although we must 

 for the present regard these propositions as questions which still 

 require a more special solution, it must be admitted that within 

 certain limits they would appear to derive confirmation from 

 several established facts ; for although we find in the older experi- 

 ments of Saussure, as well as in the more recent numerous 

 analyses of vegetable ashes instituted by Emil Wolff,* by Wieg- 

 mann and Polstorf,f and by Staffel,j many facts which seem to be 

 opposed to these general propositions, it must be remembered 

 that even in vegetative life a number of relations present them- 

 selves to our notice, whose actions on these more general laws 

 cannot be wholly overlooked. It may perhaps be maintained that 

 these hypotheses of Liebig's have not been proved with sufficient 

 precision ; but, on the other hand, the few points in which they 

 admit of dispute are not of sufficient importance to warrant us in 

 regarding them as wholly controverted. We have still so imper- 

 fect a knowledge of the relations existing in the nutritive process 

 of vegetable organisms, that it is much less easy to establish a 

 convincing refutation than to adduce a strict proof. 



In addition to alkaline carbonates, we likewise find alkaline 



* Journ. f. pr. Ch. Bd. 44, S. 385-488, u. Bd. 52, S. 37-122. 



t Ueber die anorg. Bestandtheile d. Pflanzen. Braunschweig, 1842. 



J Archiv. d. Pharm. 2 R. Bd. 64, S. 26-47. 



