273 
resistant to Wart Disease is singularly fortunate for potato 
growers, as in the case of certain other diseases, Corky Seab for 
example, all varieties appear to be susceptible 
In spite, however, of the inestimable value of the immune 
variety it is important to combat the Wart Disease fungus in 
other ways. Many of the best and most popular potatoes, such 
as Up-to-Date and King Edward, cannot be grown at all in 
infected areas. In some districts it is not easy to obtain suffi- 
ficiently large quantities of resistant seed, whilst it is possible 
that disease-resistance in certain varieties may break down alto- 
gether after some years of cultivation. In addition to this the 
disease itself is slowly spreading. If it had not been for the 
vigorous measures enforced by the Board of Agriculture and 
Fisheries Wart Disease would almost certainly have been dis- 
tributed by this time throughout the whole of England, but in 
spite of all precautions it continues to break out in new locali- 
ties. Every research therefore which throws light on the biology 
of the fungus is important, as it is only by a complete an 
accurate knowledge of its life-history that means can be devised 
for destroying it. 
Unlike the ordinary Potato Blight fungus (Phytophthora in- 
festans) the Wart Disease organism is almost exclusively sub- 
as yet been discovered. The s ngia are nelosed in . v } 
thick coat and apparently retain their vitality for a _ er 0 
years. Many cases are known ere Wart Disease has re- 
possible. (1) The disease may have cer tape Ping 
, animals, water, or other agency. 
oy net alle : fter the 
m 
diti . have 
condition. (4) The fungus may, in the absence of potatoes, hay 
attacked sie plants and saneoul to maintain an existence 1m 
their tissues, : os 
Amongst other experimental work on Wart sapheg Ww —— 
Ing carried out at the Pathological Laboratory at nb ya 
Series of pot experiments designed to throw light on st GE 
Problems. The first explanation suggested above, nam ee 
introduction, is one for field observation, but for the secon 
¢ . ri ts 
third, material has been collected and a series of codageaiee 
