30 Outlines of Horticultural Chemistry. 



a blow, or the erosion by a ladder, or the contact of two 

 branches. The wounds in such cases, as in the animal frame, 

 are long in healing ; the extravasated sap and contused vessels 

 speedily decompose : and how this spreads by contact, in all 

 organised bodies, is too well known to need to be here insisted 

 upon. The complete removal of the affected part by the 

 knife, and then covering the wound by a plaster to exclude the 

 air, is the best remedy ; and if, from long neglect, it has been 

 allowed to spread itself from branch to branch, until the whole 

 tree has become infected, remedies are then of no avail, and 

 the tree had better be removed. 



The chemical phenomena of the disease appear to be the 

 complete decomposition of the vegetable fibre, which passes off 

 in the form of carbonic acid and carburetted hydrogen gases, 

 whilst the friable matter which remains behind consists of some 

 foreign vegetable principle, the result of decomposition, and 

 an excess of saline and alkaline matters. 



Vauquelin analysed the sanious discharge from an elm, and 

 found in it nearly 40 per cent of alkaline and saline consti- 

 tuents, which is about three times as much as the sap contains 

 when in a healthy state, if compared with the amount of its 

 vegetable constituents. Then, again, the saline matter in the 

 sap of the elm consists chiefly of acetate of potash and car- 

 bonate of lime : those in the sanious discharge, of carbonate of 

 potash and carbonate of lime. Decomposition has here, there- 

 fore, been effected as well as in the carbonaceous matter of 

 the tree : a decomposition, too, aggravating the disease ; for 

 woody matter, macerated for some time in a solution of car- 

 bonate of potash, is decomposed and converted into ulmin : 

 and that this effect is produced in the progress of the disease 

 was demonstrated by Vauquelin, who found that the brown 

 matter discharged by the elm consisted of ulmin and carbonate 

 of potash. 



Sir Humphry Davy detected carbonate of lime on the edges 

 of the cankered parts of apple trees. The above facts de- 

 monstrate that an excess of alkaline matters occurs in vegetable 

 ulcerations ; and, guided by this, the last-named chemist re- 

 commended diluted acids to be applied to the wounds, and 

 even poured about the roots, in case the tree is of sufficient 

 value. The topical application would doubtless check the 

 corrosion of the ulcer ; but it admits of doubt whether the ad- 

 ministering an acid to the roots would be of benefit, unless it 

 were one that is not with facility decomposed, as the sulphuric, 

 or muriatic : for, previously to arriving at the wound, it would 

 have to be elaborated in organ which no vegetable acid, as 

 the acetic or tartaric, would pass through unchanged. Muri- 



