108 
ON THE FUNGOID DISEASES OF THE TOMATO. 
By Mr. C. B. Prowricur—Read October, 1881. 
Dunrine the autumn of last year (1880) I carried on a series of investigations con- 
cerning the various fungi which deleteriously affect the tomato, having the oppor- 
tunity of examining any and every diseased specimen of tomato which occurred in 
a large tomato growing establishment near King’s Lynn. 
Tomatos grown in the open air in this country are a very uncertain crop, 
sometimes proving a very profitable venture, but not unfrequently the reverse. 
The tomato disease is almost as well known to gardeners, and as much dreaded by 
them, as the potato disease is. A very large number of out-door diseased tomatos 
were examined by me last year. The appearance of diseased tomatos is so well 
known that it is almost unnecessary to give any description of it beyond stating that 
they have a peculiar bruised look, and are more or less mottled with black or dark 
brown patches of disease. These patches increase in size after the fruit has been 
gathered, to such an extent as to render it valueless. If the tomato be examined 
in this state, he must indeed be an acute mycologist who could demonstrate the 
fungus which has caused the disease, for, barring a few hyaline mycelial tubes 
permeating the substance of the fruit in and towards the margins of the spots, 
nothing adventitious can be detected. At any rate, I was quite unable to find 
any perfect fungus upon the numerous specimens I then examined, which could 
with certainty be credited with causing the mischief. This is not to be wondered 
at when it is remembered how rarely we are able to discover the perfect Perono- 
spora infestans upon the diseased tubers of the potato. On September 10th of this 
year, a specimen of a typically diseased tomato was brought to me, with the 
information that although the tomato was diseased the plant which had produced 
it was healthy. I at once visited the spot, and examined the plant in question. 
Sure enough the tomatos on it were diseased to a large extent, but the plant looked 
healthy. A few dead-looking spots were observed upon the lower leaves, which 
were examined with a pocket lens, but not very thoroughly, as it was raining at 
the time. When, however, these dead-looking spots were examined microscopi- 
cally, they were found to be due to the presence of Peronospora infestans. The 
fungus was not producing its conidiophores very abundantly, but still there it was 
without doubt. The central portion of the spots where the Peronospora first made 
its appearance were now nearly free from it, it being more or less confined to the 
circumferential portions of the spots. The appearance of these spots was quite 
unlike the spots produced by the same fungus upon the potato leaf. On the tomato 
leaf the spots lack the black rotting look which is so characteristic of the potato 
disease. The tomato leaf is larger and harder, so that instead of putrefying it rather 
dries up; the spots themselves look more like the sun-scalds one sees upon the leaves 
of plants grown under glass. After diseased tomatos have been gathered a short 
time, decomposition rapidly sets in, and they then harbour an incredible quantity 
