A Disease of Tomatoes. 
13 
A DISEASE OP TOMATOES. 
By F. T. Brooks, M.A. 
(Senior Demonstrator of Botany, Cambridge University), 
AND 
S. R. Price, B.A. 
(Frank Smart Student, Cambridge University). 
[With 13 Text-Figs]. 
N October, 1911, some diseased tomatoes grown out of doors 
in the neighbourhood of Bristol were sent to one of us for 
examination. These fruits bore large diseased areas somewhat 
depressed below the surface of the healthy parts. On the diseased 
portions of the fruits three fungi were found, a species of Clado- 
sporium, a species of Macrosporium, and a fungus having pycnidial 
fructifications. These fungi were indiscriminately mixed for the 
most part, but on some of the diseased areas most recently formed 
only the fungus bearing pycnidia could be seen. It was thought, 
therefore, that the fungus with pycnidial fructifications might be 
the actual cause of the rot, the other fungi having appeared later 
as saprophytes. 
In order to determine which organism was the cause of the 
disease the three fungi were isolated in the usual way by means of 
plate cultures. Tomato fruits approaching maturity were inoculated 
with these fungi in the following manner, one kind of fungus only 
being inserted in each of the fruits:—in opposite sides of each of 
three fruits two slits were made with a scalpel, and mycelium taken 
from a pure culture of each fungus was inserted in them, the fruits 
being placed on glass plates and covered with glass dishes. Three 
days later a rot had begun around each of the two slits in which the 
fungus with pycnidial fructifications had been placed, whereas the 
tomatoes inoculated with Macrosporium and Cladosporium respec¬ 
tively remained unaffected. After a fortnight the one tomato was 
completely rotted, whereas the other two were sound. Hence this 
preliminary trial made it tolerably clear that the fungus bearing 
pycnidia was the cause of the rot, the Macrosporium and Clado¬ 
sporium being of no significance in this case, although it is well- 
known that species of both of these genera sometimes cause diseases 
of tomato fruits. Subsequent experiments with the three fungi 
confirmed the result of the preliminary trial, viz„ that the fungus 
having a pycnidial type of fructification was the cause of the 
disease. 
