THE HONEY DEW. 
41 
repletion, they sprinkle the lower leaves. Even when 
no Aphides are feeding above, myriads of the winged 
forms often fill the air of a hot summer’s day, and void 
their juices whilst on the wing just as we see amongst 
some of the Lepidoptera. 
Dr. Hooker, in the ^ Gardeners’ Chronicle ’ for July, 
1873, endorses Liebig’s opinion that the honey dew 
must not be ascribed to the agency of Aphides. The 
objections urged by him were combatted by the late 
Mr. Francis Walker, in one of his papers contributed 
to the ^ Entomologist ’ of the same year. 
The Abbe Boissier de Sauvage thinks that the 
secretion under consideration may have both an insect 
and a vegetable origin ; and Mr. H. Doubleday 
ascribes the dropsical condition which he has ob- 
served in some currant leaves to a disease which 
causes the transpiration of a fluid from their pores. 
M. Boussingault^ further denies that the saccharine 
matter found on lime leaves is the produce of 
Aphides. 
He states that whilst on a visit to Liebfrauenberg, 
on the 22nd of July, he found the secretion suffi- 
ciently abundant to fall upon the ground. He 
describes it, indeed, as a rain of manna.” This 
liquid thickened in the heat of the sun, and formed a 
sort of varnish on the upper surface of the leaves. 
He collected some of it by means of a moist sponge, 
and then diluted it with water. Subacetate of lead 
precipitated from the solution a quantity of albumen and 
mucilage, after which the clear liquid was allowed to 
stand. Small crystals were then slowly deposited, which 
he subsequently identified as those of cane sugar. 
Again, by an examination with polarized light he 
found, in addition to the above substances, the pre- 
sence of dextrine, and an intermediate or inverted 
sugar, which showed under the prisms an abnormal 
index of rotation. 
Boussingault, “ Observations sur line matiere sucree apper^ue sur 
les feuilles d’nn tilleul/’ ‘ Comptes Rendiis/ 1872, tom. 74, p. 87. 
