ON VEGETATION. 357 



them ; the blossoms had long before fallen off: no 

 aphides frequent this plant, nor were there any 

 trees near them from whence any sweet matter 

 might have fallen ; we have no honey-dew upon our 

 fruit-trees, and an aphis is scarcely to be found. 

 Has any saccharine matter fallen, or been emitted 

 by the plant to entice these insects to harbour about 

 them? It clearly appears that honey-dews arise 

 from two causes ; that a large portion of it is the 

 discharges from insects of the genus aphis, has long 

 since been manifested by the Abbe Sauvages, 

 Mr. Curtis, and others ; insects discharge in all 

 days and hours during the warm months of the 

 year. But there is another kind which we find 

 only at particular times, and in certain states of the 

 atmosphere, lodged on certain plants during the 

 night in such quantities as to hang occasionally in 

 drops from the points of the leaves. The foliage 

 of the oak is at times lucid with this sweet liquor, 

 and this the bees are soon acquainted with, and 

 eagerly collect it, which they only partially do when 

 spread upon the leaves on the wall, the evident dis- 

 charge of aphides. Some of my neighbours who have 

 hives will occasionally observe, " A heavy honey- 

 dew last night, and the bees are hard at work ;" 

 this cannot proceed from insect discharges. That 

 some foliage may condense any matter that may 

 fall upon it, is not improbable ; or even excrete it 

 from their pores by the impellent power of the air 



