606 
ANNUAL REPORT OF NEW YORK 
wholly free from the curculio larvse and all other worms, it is obvious they 
are not the cause of their growth. Others have supposed they were anala- 
gous to the galls or swellings which we see on the limbs of oaks and other 
trees, and have even reported that a gall-fly is to be seen at times on these 
excrescences. But always in galls, one or more hard soed-like bodies are 
found in the centre, in which the young of the fly producing them is in¬ 
closed. Hence I know from their internal structure that these are not 
excrescences of that kind; and what the small fly is that has confirmed 
some persons in this error, wc shall shortly see. Others still have main¬ 
tained that it was a wound in the bark, made by the puncture of an insect, 
that caused this disease, some saying the remains of this puncture are often 
to be seen, when the first slight swelling in the bark begins. Yes, I have 
seen it. It is exactly as they state. Only it is not the puncture of an 
insect. It is one of the natural glands or pores in the bark, somewhat 
altered in its appearance, and rendered more conspicuous in consequence 
of the swelling. And it gives me the opinion that it is in this pore that 
the seeds of the disease are planted, or in other words, the contagion or 
poisonous matter which causes the disease here finds an entrance to the 
inner bark, which, thus tainted, begins to swell immediately around this 
pore. 
I will not detain you to notice several other conjectures that have been 
presented to the public respecting the cause of this disease. Suffice it to 
say, that having now carefully examined these excrescences, from their 
first commencement, onward through their subsequent growth, I am pre¬ 
pared to say, with the fullest confidence, that the microscope shows nothing 
whatever about them, externally or internally, indictating that an insect 
has anything to do with causing them. 
It has also been supposed that these excrescences were a peculiar species 
of fungus growing upon the limb; and there are some things about them 
which favor this view. But what is a fungus ? To express it in familiar 
language—it is a body which grows, and forms its own substance, distinct 
from and independent of the body in which it takes root and from which it 
draws its sustenance. Now these black-knots are not such a growth. 
They are merely a change in the texture of the natural parts of the limb. 
And thus we arrive at the conclusion, that these excrescences are not of in¬ 
sect origin, and are not a vegetable fungus, but are properly a disease of 
these trees, whereby the natural tissues, the bark and wood, become soft¬ 
ened and swollen, at the places affected. 
In many respects this disease appears to be analogous to the cancer in 
the human body. And the most approved remedy for it, is the same as in 
that disease. It is excision. Wherever one of these swellings is discov¬ 
ered upon a limb, the limb should immediately be cut oft', so far below the 
swelling as to be certain we remove every taint of the disease.* 
* It is worthy of note, that in tho discussion which ooourrod on the close of this looturo, 
Hon. A. B. Dickinson remarked that tho black-knot only attacks trees growing in a wet sub¬ 
soil, and if this soil be suitably undordrainod, whereby, to adopt his expressive phraso, the trees 
