292 INSECTS 



Another use that has been proposed for the acid is 

 to paint a band around the trunks of fruit trees with 

 the idea that it would be absorbed by the bark and 

 carried into the circulation, poisoning the sap to such 

 an extent as to kill all the scales and other insects feed- 

 ing on the tree. The theory is a very plausible one at 

 first sight, but unfortunately the acid as it penetrates 

 strikes first the down-current that carries it to the 

 roots, and when there is enough of it to get into the 

 active cells, these promptly die and refuse to do any 

 carrying. If the acid gets still further and really does 

 strike the up-current, then the girdling is complete 

 and the tree itself dies. Rarely, however, is there 

 enough acid applied to cause this mischief. 



This suggests the fact that there are always a num- 

 ber of philanthropic gentlemen ready to aid the farmer 

 for a consideration and willing to insert into his 

 trees a compound of which they only possess the secret, 

 which will infallibly kill all the insects infesting the tree 

 and cure all its diseases. They are even willing to give 

 a written guarantee to that effect. Many a farmer 

 and tree owner even in cities and towns falls victim 

 to the persuasiveness of these benefactors, who bore 

 holes two inches deep into the wood, fill them with 

 their compound and fasten it in tightly with a wooden 

 plug, absolutely beyond reach of those cells of the 

 tree engaged in carrying sap. Even were the material 

 soluble and active, it is imbedded in tissue which serves 

 only as a support to the tree, and has absolutely nothing 

 to do with its nourishment. Its absorption into the 

 surrounding cells would therefore mean precisely as 

 much as if it were absorbed into the tissues of the 

 nearest fence or hitching post. 



Caustic potash and caustic soda have a limited use 

 on the farm, but in the orchard and garden are fre- 



