280 
astonished to find abundant Skin spot pustules throughout 
Series 1. The details of inspection of the whole of the series 
are given below, the pot which had been examined at harvest 
time and from which the photographs had been made being 
marked D in each series. 
Results (after storage of the potatoes). 
Series 1. Oospora inoculation. 
No. of Tubers No. of tubers per pot showing 
t 
Pot. per pot. ypical Skin spot pustules. 
A. 15 ll 
B. 13 6 
C. 20 0 
DD: 16 7 
The degree of infection on any one tuber naturally varied very 
much. Some showed 2 or 3 pustules only, but generally the 
infection was much greater, and on one tuber there were as 
many as 80 pustules. A feature of the infection was that in 
the great majority of cases, the pustules appeared mainly round 
and about the eyes of the tubers. The shoots from such eyes 
were markedly fewer and weak in growth, and in a few instances, 
the eye was killed outright. ’ 
This fact is of interest since it indicates that the eye of the tuber 
is the most susceptible spot to Oospora attack, and is in contra- 
distinction to the s atement of Melhus, Rosenbaum & Schultz(‘), 
that, in Corky Scab, “ the earliest infections on the tuber usually 
occur about the stem end ” and that, in one of their experiments 
“90 per cent. of the pustules on the infected tubers were about 
the stem ends rather than the eye ends.” This eye infection with 
. pustulans is also confirmatory of the observations of previous 
English workers on the injury caused to potato eyes by Skin 
spot disease. A photograph of two of the infected tubers from 
Pot A is shown in Fig. 3, and another of an injured and apparently 
dead eye from a tuber in Pot B in Fig. 4. Some of these 
artificially produced pustules were sectioned and showed abundant 
hyphae in the cells, together with the typical characteristics of 
the Skin spot pustules we had previously examined. It was 
finally necessary to recover the fungus from the pustules and 
identify it. This was done by sterilising the skin of the tubers 
and plating out sections of the pustules in the way already 
described. In every case a luxuriant growth of hyphae from 
the cells of the section into the surrounding media was obtained. 
These were apparently all of the same species and subsequent . 
cultures established this fact together with the identity of the 
fungus as O. pustulans without any difficulty. It may be added 
that no bacterial or other fungoid contamination appeared on 
=, of ae plates. A photograph of one of the latter is shown 
in Fig. 5. 
