BOUSSINGAULT ON HONEY-DEW. 
5 
insect. This species of manna is produced by Tamarix mannifera^ 
Ehr. As with many other mannas it is the result of the punctures 
of an insect, which in the present case is Coccus manniparuSj 
H. & Ehr. (Berthelot, Ann. de CMm. et dePhys.^ ser. 3, Ixvii., 83.) 
The manna, consequently, collected in 1869 at Liebfrauenberg 
had not the same origin as the Sinai manna, though it had the same 
composition. At the time of its appearance upon the Lime no 
insects were observable. It was later that a few aphides were seen 
glued upon a certain number of the leaves. 
I have already stated that after having washed the extremity of 
a branch, glutinous points were seen gradually to rise ; at first 
scarcely perceptible, they increased each day, so as finally to cover 
the whole of the upper surface of the leaf. This slow and pro- 
gressive development of the honey-dew was clearly effected with- 
out the intervention of aphides, which did not make their 
appearance till subsequently, like the flies and bees, either to feed 
upon the secretion or to pilfer it. 
[In a subsequent number of the Comptes Rendus\(¥eh. 12) Harting 
states that honey-dew is produced by Aphis tilim^ which, living, on 
the under surface of the leaves of the Lime, drops its excrement on 
the upper surface of the leaves beneath. Analysed by Gunning 
at Amsterdam, it proved to consist of cane-sugar. Eoussingault 
remarked, in reply, that the manna of Liebfrauenberg, like the 
Sinaitic manna analysed by Berthelot, contained, in addition to cane- 
sugar, fruit-sugar and dextrine. He added, also, that the leaves of 
the Lime contain considerable amounts of cane-sugar almost pure, 
the origin of which could not be attributed to insects. 
A paper by Goethe {(Euvres d'Eist. Nat.^ par Martins, pp. 321 
— 328) contains a similar conclusion. He says (p. 324) : ''I have 
seen Limes, of which the leaves seemed varnished, but where not a 
single insect was visible. The juice is secreted by the plant itself." 
Mr. Hanbury informs me that he has noticed the exudation of a 
saccharine matter from a Canella, and that after repeated cleansings 
it still made its appearance. He has seen also the occurrence of 
minute crystals of sugar upon the corolla of the Azalea. De 
Candolle mentions the same thing in Rhododendron ponticum 
{Phys. Veg. i., 238). This is, however, different to the secretion 
which takes place on leaves, because it is probably merely due to 
the loss of water from the flower preparatory to fading. 
De Candolle remarks that granular secretions are found on the 
young shoots of the Larch, and are collected locally under the name 
of manna of Brian^on ; they also occur on Salix alha, and upon 
