Potato Disease. 211 
That the microscopic observations made by me in the autumn of 
1845, and communicated then to the New York State Agricultural 
Society, at their own request, have been confirmed in 1846 and 
1847 by scientific commissioners and committees in almost every 
country in Europe. 
That a great many experiments have been tried with salt on 
large breadths of land, and in a large proportion of these, the 
potatoes have been completely saved, while all around were 
diseased. That this remedy has failed in some cases in being a 
complete protection, is all well known to me, but even here the 
proportion of diseased potatoes was much less than where salt 
had not been used. The cause of this is very evident; I have 
always stated that the salt must be in contact with the disease to 
effect its destruction ; now let any one consider in a tenacious clayey 
soil, or in one of a light gravely nature, how easily this contact may 
accidentally fail. My conviction is more firm than ever that the 
cause of this disease is a fungus, propagated by clouds of invisible 
spores, (seeds) wdiich settle in some places and not in others, just 
as the wind listeth or bloweth, and that wherever they come into 
contact with salt, when they settle down they cannot vegetate. A 
heap of diseased potatoes from two to three acres will give suf- 
ficient spores to infect a district five hundred miles square; these 
spores only ripen and become dry enough to live and float in the 
atmosphere towards the middle of the summer, and then take 
sometime to settle and vegetate; every fungus collector knows 
that the latter end of the summer is the most favorable period for 
these minute productions; from this we see the reason why the 
earliest planted potatoes are generally the freest from disease. 
A paper has appeared within the few last days from Dr. Klotsch 
of Berlin, Prussia, detailing a new method for strengthening the 
potato, and increasing its chance of escaping disease. This new 
method is the old practice called by gardeners stopping, and has 
been practiced by them time out of mind, on cucumber, melon, 
pelagoniura and almost all plants; it consists in pinching out the 
top of a shoot, thereby encouraging it to throw out lateral branches, 
and become strong, bushy and fertile. This is a dangerous process 
in unpracticed hands, as if the stopping is continued a little too 
long the potato would not ripen, and if begun too early would 
materially injure the plant, it would probably be much too ex- 
pensive in point of labor in this country. 
I hope this communication will answer your purpose, and I 
take the opportunity of stating, that 1 am quite tired of the sub- 
ject, and will not be moved by any consideration to engage in 
farther discussion thereon — let those who choose try salt as a 
remedy, and the other leave it alone. 
Boston, 8th April, 1848. 
