72 AGRICULTURAL RESEARCH AND THE FARMER : 



is available our knowledge of spraying must necessarily be 

 empirical and little real progress can be made. The work 

 naturally takes time, but the twelve months so far devoted to it 

 have thrown much light on the fundamental nature of the 

 disinfection process. The object is to find out exactly what 

 happens when the poisonous substance actually meets the fungus 

 spore; what are the effects of varying external conditions; 

 what strength of solution is required under particular conditions ; 

 how many spores are killed and in what -time, &c. The fungus 

 so far used has been Botrytis, and the work is now being extended 

 to include killing by heat as well as by poisonous re-agents. 



Wart Disease of Potatoes. — This disease is so widespread and 

 disastrous that a special grant for its investigation has been 

 made by the Ministry to the Rothamsted Institute. The question 

 is being attacked in various ways at several centres ; at Rotham- 

 sted, prevention by means of soil sterilisation is the main subject 

 of study. The necessary field and glasshouse trials are being 

 carried out at the Potato Testing Station at Ormskirk and at 

 Rothamsted. A wide range of poisons and other sterilising 

 agents are being tested, to find out their effect upon the wart 

 disease fungus in the soil, the object in view being to discover 

 some economical treatment which will kill the fungus without 

 adversely affecting the soil. In this connection it is important 

 to have rapid laboratory methods for examining the soil and 

 finding whether or not the fungus has been killed. The present 

 methods are being improved upon, thus speeding up the work 

 (considerably. Experiments are in progress to see how far the 

 progress of the disease is affected by such factors as the age or 

 3ize of seed, time of planting, conditions of the weather and soil, 

 manurial treatment, and so on. The question of a possible 

 " alternative host " on which the fungus may spend part of 

 its life history is also being examined, for the fungus has been 

 found on toma'toes and woody and black nightshade. A further 

 very important aspect which is being actively studied concerns 

 the nature of immunity from and susceptibility to the disease, 

 and the differences in quality, &c., which exist between immune 

 and susceptible varieties. 



The above indicates briefly certain of the main lines of work 

 on fungi and algae in progress at the Institute The question 

 of insect pests is dealt with by another Department of the 

 Institute, and before dealing with it we will refer to the investiga- 

 tions into fungus diseases which are taking place at other centres. 



