14 
TIIE C U L TIV A T 0 R 
The Potato Disease. 
In the Dec. No. of The Cultivator, we published 
an article from J. C. Cleveland, on the Use of Salt 
in Potato Culture. From a reply to this article, by 
Prof. S. W. Johnson of Yale Analytical Laboratory, 
published in the Country Gentleman of Dec. 10, we 
make the following extract, which will be read with 
interest:— 
Without going into a discussion of the potato dis¬ 
ease, it may be stated that it has been satisfactorily 
proved that not an insect, nor a fungus, not the want of 
any fertilizer or soil-ingredient, is the cause of the rot, 
but that the weather, i. e., atmospheric changes, lie at 
the bottom of the difficulty. So much is proved, or at 
any rate, is supported by such an amount of well- 
weighed evidence, that we must accept it as Droved for 
the present. 
Besides the weather as the exciting cause, it is often 
assumed that a predisposing cause exists in the plant 
itself, viz., a constitutional weakness induced by bad 
culture ; but this is still an assumption at least in the 
form in which it is almost invariably set forth. 
1. It is a fact, as far as I can learn, that there is no 
variety of potato that has been subjected to field cul¬ 
ture for several years, which has not been more or less 
affected by the disease, and there is no variety that has 
not been grown without being attacked by it. It is also 
a fact, 2, that the same variety is unequally affected in 
localities but a few miles distant from each other. It 
is true, 3, that in some localities and seasons early po¬ 
tatoes, or those early planted, are more affected than 
late ones ; and again, elsewhere or in other years the 
early potatoes escape while the late ones suffer. Gen¬ 
erally, as far as the facts in my knowledge warrant a 
conclusion, very early or very late potatoes are unaf- 
rected while those whose period of ripening falls about 
the middle of August or the first of September are 
most liable to attack. 
Now the first fact shows that there is no potato pos¬ 
sessed of such strength of constitution as to be able 
always to resist the disease, but that the rot falls indis¬ 
criminately upon all kinds, although it rarely destroys 
or affects all the tubers of any kind. 
The second fact admits of explanation if we remem¬ 
ber how locality affects the weather, particularly sum¬ 
mer weather. 
I know a region where beautiful farms lie on natu¬ 
ral terraces that form the great steps up the side of a 
long hill-range, at the base of which runs a wide river. 
At a certain point, the first terrace is a wide alluvial 
flat of soil, vieing with the richest western bottom-land 
in beauty and productiveness, and so nearly on a level 
with the river that it is often overflowed. Here, years 
ago, I have helped gather the superbest crops of huge 
healthy potatoes. Now they are never planted there, for 
the crop can’t be depended upon. A mile back from the 
river oomes the second terrace, 30—50 feet higher. The 
soil is poorer though still good, and of the same general 
character. On this terrace last summer, the potato 
disease began its ravages about the 20th of August, 
while two miles back on the next terrace, they were 
srill unaffected. Here the potatoes were of the same 
kinds, were planted about the same time in a soil of 
nearly uniform character. None of them had any salt, 
and yet. why these differences—could the weather va¬ 
ry at points so near to each other 7 I am of opinion 
that the whole trouble was in the weather, i. e., in the 
state of the atmosphere. The blight appears to attack 
the potato tops, when the sun rises into a clear sky and 
shines down with its fullest force upon fields covered 
with fog, or which are in an atmosphere saturated with 
moisture. Of those terraces that have been mentioned, 
the lower ones are often covered with heavy hanging 
fogs, while the higher ones are surrounded by a clear 
breezy air. In the lower terraces, the circulation of 
the juices of the plants, which depends greatly upon 
evaporation, is checked, and the juices putrify instead 
of being elaborated ; while on the hillsides the pro¬ 
cesses of vegetation pursue more nearly their normal 
course. 
The 3d fact would almost warrant the assumption, 
which is sustained by many analogies in vegetable 
physiology, that there is a period in the development 
of the potato, when more than at any other it is sub¬ 
ject to the blight. This period is most naturally sought 
for at the time when the plant is undergoing the most 
rapid vegetative changes, viz., at or about the time of 
flowering. 
If this be true, we can understand that those pota¬ 
toes, of whatever variety, which arrive at the critical 
period of growth, at such times and in such localities 
as are visited by the atmospheric conditions that have 
been mentioned, would be struck with blight, while 
other potatoes which have passed or not reached the 
critical period of growth, would escape. We can fur¬ 
ther understand that salt when applied in contact with 
the seed potato, may, by virtue of its hindering the 
development of the germs, have the effect to keep the 
plants backward until the bad weather has passed, and 
thus save them. It may also retard the growth of 
very early varieties, so as to bring them into unfavora¬ 
ble weather at the time when they ; re most susceptible 
to atmospheric disturbances, and thus destroy a crop 
that otherwise would have been good. 
The fact that salt ascends from the sea in the spray, 
and is thus distributed in enormous quantities on the 
land contiguous to lee-shores, and this without at all 
hindering there the ravages of the potato disease, is a 
strong fact against Mr. C.’s conclusion, that salt will 
prevent if not cure the disease entirely at no distant 
day. 
Mr. C. says that “from all quarters reports come to 
us, too numerous to detail, in favor of the use of salt 
this season, for growing potatoes upon a dry or sandy 
soil.” Will Mr. C. have the goodness to inform us the 
source of these reports, or where they can be found I 
So important facts ought to be detailed until they are 
well established. 
In “axiom” 12 occurs the following sentence:— 
“ Plant the genuine old-fashioned Blues from which to 
obtain balls to renew and improve the seed.” In axiom 
28 it is said—“The white varieties rot the worst, be¬ 
cause they are the class that have been subject for the 
longest period to bad cultivation.” 
Here we have the view which seems to have origina¬ 
ted with Parmentier, who introduced the potato into 
France, and has been so loudly advocated by writers 
on this subject, viz., that the potato has deteriorated by 
long or bad cultivation, i. e., reproduction from the 
tuber, and can only be reclaimed by raising new plants 
from the seed. 
Why, let me ask, does a plant deteriorate if it be 
not raised from the seed 7 Is not reproduction by bud, 
