On the Potato Disease. 
381 
but no farther. I had the whole of tlie haulm, except a small 
patch for observation, pulled up without delay, as 1 found the 
Botrytis infcstans, which is at least an infallible indication of the 
disease, had attacked some of the lower leaves slightly all over 
the field. On taking up the crops, the Shaw contained five pecks 
of diseased in 100 bushels. The blue, being later, contained 13 
bushels in 350 bushels, but 10 bushels out of the 13 came from 
the pit and the part immediately surrounding it. On the drier 
parts of the field there was scarcely a bad potato. It is also very 
remarkable that in the grounds of my neighbours, right and left, 
the disease commented in fiUed-up pits, and the tubers were in 
those parts much the worst. It was in a similar situation in the 
year 1841 that I observed my potatoes affected with the same 
disease ; and a very extensive grower has since informed me that 
previous to his draining his fields he has sometimes lost 20 tons 
by the same rot in wet autumns. The blotches on the stalks I 
find denote the second stage of the disease, and I was anxious to 
have my haulm pulled up before these appeared, — for which the 
weather was favourable. With much wet and a close atmosphere 
the gangrenous process is very rapid, and the botrytis multiplies 
greatly ; but during drying winds and bright sunshine the latter is 
not developed, except in very damp situations. I gathered during 
the dry warm weather a great number of blotched leaves, on 
which I coidd not discover the botrytis with the highest power of 
my microscope ; but on putting a drop of water into a wine-glass 
and inserting the petiole, and placing the glass in a close shady 
place, a crop of it was produced within two days. By this means 
I have raised finer specimens of it than ever I have found out of 
doors. I inoculated the leaves of several potatoes with the 
botrytis by scraping the underside with my nail and rubbing an 
infected leaf upon them, and, if the weather were gloomy and 
close, it would appear in two or three days, but if dry, and a brisk 
wind prevailed, in an open situation, it would sometimes not grow 
at all. 
Having kept two or three potato-plants in my greenhouse for 
experiment during the summer, which were pertectly healthy on 
the 13th of Aiigust, the atmosphere of the house being then moist, 
I inoculated two or three leaves of one of them, which I had also 
subjected io experiment in the spring, and set an infected plant 
taken up on purpose next to it, but up to this time, October 14, 
only five of the leaves and petioles, which are not more than three 
inches apart, are withered ; the atmosphere of the house having 
subsequently been kept drier for the purpose of ripening grapes, 
with good ventilation ; the vitality of the plant has a second time 
overcome this injury, and the rest of the foliage is quite green 
and healthy. Still I do not doubt that the botrytis is a very 
