502 Drs. Will and Fresenius on the 



and amoDfT arboreous plants, the Coniferce, consist almost en- 

 tirely of the alkaline and earthy phosphates. They do not 

 effervesce with acids, they contain however variable quantities 

 of silica and sulphates, but chlorides are either entirely want- 

 ing, or merely traces of them exist. The ashes of the seeds 

 of the oak, of the chestnut and of the beech, and probably of 

 many other trees, effervesce strongly with acids; besides 

 phosphates they contain a considerable quantity of carbonates, 

 which have resulted from the salts of vegetable acids con- 

 tained in the seeds. The proportion of chlorides, sulphates and 

 silica to the other constituents, is also in these ashes but small. 



We conclude from these facts, that the salts of phosphoric 

 acid are indispensable mineral constituents of the Cerealia, 

 &c., and that the oak and the chestnut, &c. require, besides 

 these, alkalies not united with mineral acids. 



It would be very difficult at present accurately to distinguish 

 the so-called essential and non-essential constituents of ashes. 

 A plant requires for its different parts, and at different periods 

 of its growth, a supply of mineral constituents, varying both 

 in quantity and in quality. There is no ash-constituent which 

 we can as yet decide to be entirely unessential. We can how- 

 ever distinguish those which have been assimilated by the plant 

 and have formed a part of it from those which are within the 

 plant, without having been assimilated by it, but await, as it 

 were, their approximation in its future development and ma- 

 turation. Among the latter we may class the alkaline chlo- 

 rides and the sulphates, which are always present in vegetable 

 ashes ; they exist in the form of soluble compounds in the 

 juices of every plant, and are doubtless indispensable to it, 

 as yielding some of its elements ; we have however as yet no 

 reason for supposing that they themselves become constituents 

 of the organs of the plant. According to Guibourt [Journ. dc 

 Pharm. xxvi. p. 264'), the ashes of juicy saline plants contain 

 only 17 per cent, of chlorides to 69 per cent, of carbonates. 

 It would seem highly probable that the bases of salts of vege- 

 table acids are derived from chlorides; the chlorides in this 

 case suffer a decomposition, in which the electro- negative 

 element plays but a subordinate part. These chlorides, which 

 seem so necessary for saline plants, may probably be replaced 

 by other compounds of the same basyles, provided they be 

 not injurious to die plants, and that they be equally soluble 

 with the chlorides, and consequently existing as largely in the 

 juices of the plant. 



We have further reason for supposing these constituents to 

 be unessential, from the fact that their quantities from the same 

 kind of plants are variable, without there being evidence that 

 they are leplaced by any other body. The quantity of sul- 



