DISEASES. 189 



ally perishing by it ; but in Southern Ohio, as I am told, 

 the Black-knot is never met with. In the Eastern States 

 it has been observed from time immemorial, and various 

 contradictory opinions have been broached as to its real 

 nature and origin. 



" In 1865 I watched the Black-knot carefully through 

 all its stages, from its earliest commencement to its com- 

 plete maturity, experimenting at the same time on numer- 

 ous specimens collected week after week, so as to ascertain 

 what insects bred in it. The practical conclusion I have 

 arrived at, is simply this : — If the diseased twigs are all 

 cut off and destroyed early in July in the latitude of New 

 1'orJc, or a little earlizr or later according to the latitude, 

 taking care to cut a few inches below the affected part, the 

 £lack-knot can be checked and probably entirely eradicat- 

 ed/ but if this operation is delayed till August, it will be 

 nf no benefit whatever. Hence we can easily account for 

 a circumstance which has puzzled many men wonderfully, 

 viz. : That cutting off and burning the diseased twigs is 

 pronounced by some to be a sovereign remedy, and by 

 others to be a delusive humbug. Those that do this 

 eai-ly enough, find it effectual ; those that delay it till too 

 late, find it of no use. 



" This perhaps will be sufficient for some few impatient 

 souls, who take everything upon trust that they see in 

 print, and care nothing about the rationale of a mode of 

 treatment, so long as it be practically available. But for 

 the benefit of that large class of intelligent agriculturists, 

 who have been deluded by too many quack prescriptions 

 to place much faith in any man's ipse dixit, and who in any 

 case like to understand the principle of a remedy before 



