248 Transactions British Mycological Society. 
The non-immune variety Up-to-Date was used and a single 
tuber planted in each pot, about the middle of April. The 
shoots from the potatoes appeared above ground in the usual 
time, except in the pots with 168 and 244 grams of soda. In 
the former of these the shoot from the germinating potato was 
somewhat later in pushing its way through the soil and in the 
latter the shoot failed to appear. The tuber when removed 
from the soil showed that the eyes had commenced to germinate 
but had failed to develop and had died off; the roots had also 
failed to penetrate the soil. This tuber was encouraged to 
germinate and was again planted in the same pot. Later in the 
summer, when the excessive rain had leached some of the soda 
from the soil, a very stunted growth was produced, with a few 
tubers ranging from the size of a pea to that of a bean. The 
old tuber did not decay in the soil. It may be assumed that the 
higher limit of soil alkalinity had been attained by the appli- 
cation of such a large quantity of soda. 
The following table shows the #H concentration at the com- 
mencement and at the conclusion of the experiment and also 
the occurrence of the disease. It will be noted that the wart 
disease did not appear in the pot with 168 grams of soda. 
pH concentration 
Pots Ee ASE 
Grams of soda Commencement Conclusion 
14 8 Fi Wart disease 
28 9 15 : 
56 9°5 8 
I12 Io 8°5 
168 II°5 9:2 No wart disease 
(168 grams on a ten inch pot would be approximately 2 ozs. per sq. yard.) 
The diminution of the H concentration would be due to 
the leaching action of the almost continuous rains during the 
summer of 1922. 
A parallel experiment, neutralising the soil with chalk, was 
also carried out. Two pots were employed filled with ‘soil 
similarly infected with wart disease, the one having {4 chalk 
and the other } chalk mixed with it. In the first the 6H varied 
from 10 at the commencement to 9:5 at the conclusion and in 
the other pot the same variation was from 11 to 10. In neither of 
these pots was any wart disease to be discovered upon the tubers. 
From these experiments it may be inferred that Synchytrium 
endobioticum is sensitive to a high degree of alkalinity and fails 
to attack the potato when the fH concentration of the soil is 
in the region of #H 10:5. 
The experiment was not designed to form any idea of the 
influence of soil alkalinity upon the yield of tubers, but it may 
be remarked that soil alkalinity, while preventing wart disease, 
has a tendency to diminish the crop. 
