416 BOARD OF AGKICULTURE. 



all that part of the branch and trunk below depended upon the elaborated 

 sap of the leaves above, shrunk, turned black, and dried up."— p. 261. 



Lindley, in his worlc on Horticulture, p. 42-40, has detailed experi- 

 ments illustrating vegetable perspiration, from which we may form an 

 idea of the amoimt of fluid which these "very minute, brown colored 

 aphides" would have to drink. A sunflower three and a half feet high, 

 perspiring in a very warm day thirty ounces, nearly two pounds; on 

 another day twenty ounces. Taking the old rule, "a pint a pound," 

 nearly a quart of the fluid was exhaled by the sunflower in twelve houi's, 

 and the vessels were still inflated with a fresh supply drawn from the 

 roots. Admitting that the leaves of a fruit tree have a less current o^ 

 sap than a sunflower, or a grapevine, yet in the months of May and June, 

 the amount of sap to be exhausted by these brown aphides 

 would be so gi-eat that if they drank it so suddenly as to cause a tree to 

 die in a day, they would surely augument in bulk enough to be discovered 

 without a lens. If some one had accounted for the low water in the 

 Mississippi in 1843 by saying that buffaloes had drunk up all the upper 

 waters of the Missouri and cut off the supply, we should be at a loss 

 which most to pity, the faith of the narrator, or the fate of the buffaloes 

 after the imbibition. 



But the most curious results follow these feats of suction. The limbs 

 and trunk below shrink and turn black for want of that elaborated sap 

 extracted by the aphides. And yet, every year we perform this operation 

 in ringing or decortication of branches for the purpose of accelerating 

 maturation or improving the fruit. Every year the saw takes off a half, 

 and sometimes more, of a living tree, and the effect is to produce new 

 shoots, not death. Is an operation which can be safely performed by 

 man. deadly when performed by an insect? Dr. Mosher did not detect 

 the insects without extreme search, and then only in colonies on healthy 

 branches. Do whole trees wither in a day by the suction of such Insects? 

 Had they been supposed to poison the fluids the theory would be less ex- 

 ceptionable, since poisons in minute quantities may be very malignant. 



While we admit a limited mischief of insects, they can never be the 

 cause of the prevalent blight of the Middle and Western States, such a 

 l)light as prevailed in and around Cincinnati in 1844, nor of that which 

 prevailed in 1832. The blight-beetle, after most careful search and dis- 

 section, has not been found, nor any trace or passage of it. Dr. Mosher's 

 insect may be set aside ♦ithout further remark. 



I think that further observations will confirm the following conclu- 

 sions: 



1. Insects are frequently found feeding various ways upon blighted 

 trees, or on trees which afterward become so. 



2. Trees are fatally blighted on which no insects are discerned feed- 

 ing, neither aphides nor Scolytus pyri. 



