182 THE COTTAGE 
were these insects, on one occasion, a few days since j 
collecting the honey-dew from some filbert’s leaves, 
that we were informed that a swarm was alighted 
upon them. This, however, continued only for less 
than a week, and now, though some few of the leaves 
are nearly as clammy as ever with this saccharine 
exudation, we do not see any bees visiting them. 
The honey-dew is not, like the potato murrain, a 
modern infirmity of plants; for it is mentioned by 
Pliny imder the fanciful designation of the ‘ sweat 
of the heavens,’ and the ‘ saliva of the stars,’ though 
he questioned whether it is a deposition from the 
air, purging it from some contracted impurity. 
More modern philosophers have been quite as erro¬ 
neous and discordant in their opinion relative to the 
disease’s nature. Some, with the most unmitigatable 
asperity, declare that it is the excrement of aphides. 
Others as exclusively maintain that it is an atmo- 
speric deposit, and a third party consider that it arises 
from bleeding, in consequence of the wounds of in¬ 
sects. That there may be a glutinous saccharine liquid 
found upon the leaves of plants arising from the first 
and third named causes is probable, or rather certain; 
hut this is by no means conclusive that there is not 
a similar liquid extravasated upon the surface of the 
leaves, owing to some unhealthy action of their 
vessels. It is with this description of honey-dew 
that we are here concerned. The error into which 
writers on this subject appear to have fallen, consists 
in their having endeavoured to assign the origin of 
every kind of honey-dew to the same cause. Thus 
the Rev. Gilbert White seems ( Naturalist’s Calendar,) 
to have had a fanciful and comprehensive mode of 
accounting for the origin of honey-dew, telling us, 
under the date June 4th, 1783, “vast honey-dews 
this week. The reason of this seems to he, that in 
hot days the effluvia of flowers are drawn up by a 
brisk evaporation, and then in the night fall down 
with the dews with which they are entangled.” The 
objection urged to this theory by Curtis (Trans. Linn. 
Soc. vi. 82) is conclusive. If it fell from the atmo¬ 
sphere, it would cover every thing on which it fell in¬ 
discriminately ; whereas we never find it but on cer- 
ain living plants and trees ; we find it also on plants 
in stoves and greenhouses covered with glass. 
Curtis had convinced himself that the honey-dew 
was merely the excrement of the aphides, and he 
supported his theory with his usual ability, although 
he justly deemed it a little ‘ wonderful extraordinary’ 
that any insect should secrete as excrementitious 
matter, sugar; he even thought it possible, if the 
ants, wasps, and flies, could be prevented from devour¬ 
ing the honey-dew, ‘ almost as fast as it was deposited,' 
to collect it in considerable quantities, and eon vert it 
into the choicest sugar and sugar-candy. 
The fact that honey-dew is n,ever found except 
upon the upper surface of a leaf, whilst the aphides 
GARDENER. July 
are as exclusively confined to the under surface, is 
fatal to the theory of Mr. Curtis. 
We have no doubt ourselves that lioney-dew is an 
unnatural exudation, caused by a heat of the air and 
dryness of the soil not suited to the habit of the plant 
on which the exudation appears. It is somewhat 
analogous to that out-burst of blood which in such 
seasons is apt to occur to man, and arises from the 
increased action of the secretory and circulatory 
system to which it affords relief. There is this great 
and essential difference, that, in the case of the plants, 
the extravasation is upon the surface of the leaves, 
and consequently in proportion to the abundance of 
the extruded sap are their respiration and digestion 
impaired. 
Azaleas sometimes, hut rarely, have the fine hairs 
on their leaves, especially on their lower surface, 
beaded, as it were, with a resinous exudation. It is 
never found but upon plants that have been kept in 
a temperature too high, and in a soil too fertile. This 
is a kind of honey-dew, and, like it, an effort to relieve 
the surcharged vessels; occurring also in various 
forms in other plants. 
This lioney-dew, or exudation of sap, may be both 
prevented and cured by mulching over the roots of 
the trees, and giving to them regularly and plentifully 
supplies of water. Where tins was done to one of 
three filbert trees, all affected by honey-dew, and its 
leaves had been well syringed, it left that one, though 
continuing for weeks after unmitigated on the other 
two. This, added to the successful application of 
other liquids to plants, in order to prevent the occur¬ 
rence of the lioney-dew and similar diseases, seem to 
substantiate the opinion that a morbid state of the 
sap is the chief cause of the lioney-dew; for it would 
be difficult to explain the reason why the use of a so¬ 
lution of common salt in water applied to the soil 
in which a plant is growing can prevent a disease 
caused by insects. But if we admit that the irregular 
action of the sap is the cause of the disorder, then w r e 
can understand that a portion of salt introduced hi 
the juices of the plant would naturally have a ten¬ 
dency 4o correct or vary any morbid tendency, either 
correcting the too rapid secretion of sap, stimulating 
the plant in promoting its regular formation, or pre¬ 
serving its fluidity. And that fiy such a treatment 
the lioney-dew may be entirely prevented, we have 
often witnessed in our own garden, when experiment¬ 
ing with totally different objects. Thus we have seen 
plants of various kinds, which have been treated with 
a weak solution of common salt and water, totally 
escape the lioney-dew, where trees of the same kind, 
growing in the same plot of ground not so treated, 
have been materially injured by its ravages. We think, 
however, that the solution which has been sometimes 
employed for this purpose is much too strong for water¬ 
ing plants. We have always preferred a weak liquid, 
and are of opinion that one ounco of salt to a gallon 
