326 



DISEASES 



Sect. XIV. i. 7 



trees; and which fhews, that its exfudatlon mufl be confiderably 

 injurious to the tree, as before mentioned in Sed. VL 6. 3. 



In a paper written by the Abbe Boiffier de Sauvages, he defcribes 

 two kinds of honey-dew ; one of which he concludes to be an exfu- 

 dation from the tree, and the other he alTerts to be the excrement of 

 one kind of aphis, which the animal proje6ls to the diftance of fome 



* F 



inches from its body on the leaves and ground beneath it ; and which 

 he believes the animal acquires by piercing the fap-veffels of the 

 leaf. This paper is detailed in Wildman's work on Bees, p. 46. 

 The circumftances are diftindlly defcribed, and by fo great a philofo- 

 pher as Sauvages of Montpellier, that it is difficult to doubt the au- 

 thenticity of the fadl. But that a material fo nutritive fhould be pro- 

 duced as the excrement of an infecl is fo totally contrary to the 

 {Irongeft analogy, that it may neverthelefs be fufpeded to be a mor- 

 bid exfudation from the tree ; though thefe infe6ls might' occalion- 

 ally prey upon it, and void it almoft unchanged at thofe feafons, be- 

 caufe the infedts continued fome months after the honey-dew ceafed, 

 and before it commenced, as mentioned belo.w ; and the upper fur- 

 faces of the leaves became covered with a black powder, which had 

 before been covered with the honey-dew. And laflly, becaufe on 



oth 



the peach and neS. 



other feafons of th 



year, no honey-dew is perceived, though the aphis much abounds to 

 the great injury of the trees. 



Early this morning, June 18, 1798, I obferved a remarkable ho- 

 ney-dew on an extenfive row of nut-trees, corylus avcllana, which 

 o-row by the fide of a pond of water ; the fun (hone bright, and the 

 uppeY furface of every leaf, which was illumined by the fun, was 

 covered with a vifcid juice, which tafted as fweet as diluted honey. 

 From many of thefe leaves large drops hung from the point, and dur- 

 ing that daiy and the following one much of this honey dropped down 

 fo as to moiften the gravel walk beneath the branches of every tree, 



ne became warmer ; and the 



leaves, 



and feemed more fluid 



the funfh 



