316 PYRUS MALUb. 
ture; and the remedy, or palliative, in such soils, is liming abundantly, to neu. 
tralize the oxide ; and planting on the surface, without digging the ground, but 
only hoeing, or keeping it entirely in pasture. The trunk and branches, in some 
soils, and in moist situations, are liable to be infested with lichens and moss, 
which must be scraped off; and in others, the mistletoe is apt to take root, which 
must be cut out. The fungus, iEcidium cancellatum, which also grows on the 
leaves of the pear-tree, and produces what is called mildew, is not unfrequent on 
those of the apple-tree. 
The leaves, flowers, fruit, and wood of the apple-tree are subject to the attacks 
of numerous insects, or their larvae, against which there are few or no remedies. 
One of the most common enemies to this tree, in Europe, particularly in England, 
is the cotton insect, or woolly aphis {Aphis lanigera, of Linnaeus, and Eriosoma 
mali, of Leach.) This insect was first described by Hausmann, in 1801, as infest- 
ing the orchards of Germany ; but it was noticed in England as early as the year 
1787, and has since acquired in that country, though improperly, the name of 
"American blight," from the belief that it had been imported from America. 
Although it exists in the United States, it is exceedingly rare; but it is thought 
not to be indigenous, but was brought to this country on fruit-trees from Europe. 
It appears to have been known, also, by the French gardeners for a long time 
previous to either of the above-named dates ; and according to Mr. Rennie, it is 
found in the orchards in the vicinity of Harfieur, in Normandy, and is very 
destructive to the trees in the department of Calvados. The eggs of this insect 
are so small that they cannot be distinguished without the aid of a microscope. 
They are enveloped in a cotton-like substance, furnished by the body of the 
insect, and are deposited in the forks of the branches, and in the chinks of the 
bark, at or near the surface of the ground, especially if there are suckers springing 
from that place. The young, when first hatched, are covered with a very short, 
fine down, and appear, in the spring of the year, like so many little specks of 
mould. As the season advances, and the insects increase in size, their downy 
coats become more distinct, and grow in length daily. This down is very easily 
removed, adheres to the fingers, when touched, and appears to issue from all the 
pores of the skin of the abdomen. When fully grown, the insects of the first 
brood are one tenth of an inch in length, and, when the down is rubbed off, the 
head, antennas, sucker, and shins, are found to be of a blackish colour, and the 
abdomen of a honey-yellow. The young are produced alive during the summer, 
are buried in masses of the down, and derive their nourishment from the sap of 
the bark and of the alburnum or young wood directly under the bark. The 
adult insects, it is said, never acquire wings nor honey tubes, but from time to 
time, they emit drops of an adhesive fluid from the extremities of their bodies. 
Although destitute of wings, they are conveyed from tree to tree by means of 
their long down, which is so plentiful and so light, that they are easily wafted 
by the winds of autumn, and thus the evil will gradually spread throughout an 
extensive orchard. The numerous punctures of these insects produce on the ten- 
der shoots a cellular appearance, and wherever a colony of them is established 
warts or excrescences arise on the bark ; the limbs thus attacked, become sickly, 
the leaves turn yellow and drop off; and, as the infection spreads from limb to 
limb, the whole tree becomes diseased, and eventually perishes.* A writer in 
the London " Entomological Magazine" describes the mode of propagation of this 
insect, and gives a method of destroying it as follows: " These blights wander 
wherever it pleases the wind to carry them; and, if bad luck should drive one 
of them against the branch of an apple-tree, there it will stick, creep into a crack 
in the bark, bring forth its young, and found a colony. The white cotton soon 
* See Harris' Report, p. 193. Also Illiger's Magazine, i., p. 440 ; and Rennie's Insect Miscellanies, 
p. 180. l 
