194 
mr. Norton’s letters.—no. 5. 
iillr. Norton's Cutters.—No- 5- 
I have found here a series of researches upon the 
nature and causes of the potatoe disease, which is, 
in many respects, very complete and valuable. 
These researches are by Professor Harting, Profes¬ 
sor of Microscopy in the University of Utrecht. 
His paper upon the subject is full of interest; hut, 
although published in French, seems to have shared 
the common destiny of Dutch works in being little 
known out of the Netherlands. 
Professor Harting’s researches were, for the most 
art, microscopic, and for such he has every faci- 
ty, his rooms being furnished with at least a 
dozen microscopes of the best quality. He has col¬ 
lected potatoes, diseased and healthy, from all parts 
of Europe, and even from America. Guided by 
these specimens, he has traced the progress of the 
disease from its very commencement, both in the 
leaves and stalk and in the tuber. All of his con¬ 
clusions seem reasonable and not improbable. 
The disease in the tuber always commences by 
the appearance of a brown matter in the cells 
which contain the starch. Each of these cells in¬ 
cludes a little bag filled with grains of starch, and a 
liquid, having in solution albuminous substances, 
dextrine, and a little sugar; by the decomposition 
of these substances is produced the brown color 
which, in a more advanced stage of the disease, 
becomes black. On chemical examination, these 
colored substances have all the properties of humus 
and ulmin, two bodies which, under the form of 
humic and ulmic acids, occupy a prominent position 
in the organic part of the soil. As the disease ad¬ 
vances, the walls of the cells are destroyed, and 
finally large cavities are formed where the potato 
is exposed to drying influences. At, or sometimes 
before, this stage of the malady, parasitic fungi be¬ 
gin to appear, generated within the cells. Of these 
plants, Professor Harting has figured and described 
no less than nine varieties. 
It has been said that these are the cause of the 
malady; but the most powerful microscopes show 
nothing of them until an advanced stage of disease, 
and sometimes not even then ; instances are not un¬ 
frequent when the whole tuber is destroyed without 
their appearance. Another very conclusive reason 
against the fungus theory, is the fact that infection 
is with difficulty, if at all, transmitted by these 
plants. When they were placed in contact with a 
freshly cut surface of a healthy tuber, and allowed 
so to remain for a month, in no instance was the 
same species reproduced in one case, or fungus ap¬ 
peared on the cut surface, but it was of another 
species. The brown and black matters, on the con¬ 
trary, are infectious, when allowed to remain in 
contact with a healthy cut surface, but not when 
the skin of the healthy tuber is unbroken. 
From the above facts, Professor Harting draws 
the conclusion that these parasitic fungi are not a 
cause but a consequence of the disease. The same 
thing is his opinion with regard to insects, and 
here he seems to be still more obviously right. 
Some persons in England, with singular pertinacity, 
yet insist upon this explanation; but a microscope 
of 500 linear magnifying power, shows neither 
eggs, larva), nor insects, until an advanced pe¬ 
riod of the disease, and often they do not appear 
at all; this is the case both in the leaves and tubers 
If we ascribe the malady to either an insect or 
parasitic fungus, it will be very difficult to fix upon 
the real culprit, as sometimes one, sometimes an¬ 
other appears alone, sometimes three or four species 
together are observed in the same tuber. 
It is easy to see from the above, that Professor 
Harting considers the commencement of the disease 
to be a chemical change. For the causes of this 
change he looks to the atmosphere ; and in sup¬ 
port of his views has collected a great number 
of thermometrical and barometrical observations, 
made during the year 1845, and several of the pre¬ 
ceding years. These tables certainly show a sin¬ 
gular state of the atmosphere during the summer 
of 1845. Ordinarily the pressure of watery vapors 
in the air diminishes towards midday; but then it 
increased, and the generality of vapor in the air 
was also unusually great. The temperature at the 
same time w T as elevated. This would hasten the 
movements of the sap from one cell to another, and 
increases the evaporation from the pores of the sur¬ 
face ; but this evaporation, and, consequently, the 
general movement, would be checked by the unu¬ 
sual moisture and pressure of the atmosphere ; at 
such an elevated temperature the decomposition of 
some of the albuminous matters would soon com¬ 
mence. In June, July, and August, when the tem¬ 
perature of the air is most elevated, the leaves and 
stalk were first attacked. Later in the season, 
when the ground was warmer than the air, the 
commencement was in the tubers. 
Professor Harting only gives this as a probable 
explanation, and it has many strong points ; but 
there are yet numerous questions occurring to me 
w T hich it does not sufficiently explain. Why is it, 
for instance, that of two varieties, scattered 
through the same neighborhood, and in the same 
circumstances, one is scarcely at all, and the other 
almost invariably affected ? Perhaps the solution, 
to this and many other like objections may be 
found as we have further experience; in the mean¬ 
time, Professor Harting has accomplished a valuable 
investigation in an unprejudiced spirit, and has add¬ 
ed greatly to our knowledge of the phenomena of this- 
disease, and gives at least much authentic negative 
information as to its causes. John P. Norton. 
Utrecht, Netherlands, April 8th, 1847. 
Wool-growing in South Carolina. —Through 
the kindness of a friend, we have received a Report 
of the Proceedings of the Union Agricultural So¬ 
ciety, of South Carolina, by which we are rejoiced 
to learn that our Southern brethren are becoming 
more and more awake to their interests, and conti¬ 
nue to direct their attention to those prQductions 
necessary for clothing and provisioning themselves- 
and servants. Among other things particularly re¬ 
commended in this report is the growing of wool 
and mutton. To those who are not familiar with 
the different breeds of sheep, we would recommend 
the South Downs as the most suitable for general 
purposes in that region. Their wool is quite good' 
enough for all ordinary uses, and their mutton sur¬ 
passes, perhaps, that of every other breed for sum¬ 
mer slaughtering,being better marbled, less fat than 
the Bakewells, Leicestershires, or Cots wolds, and yet 
fat enough to give richness and fine flavor to the meat 
