GENERAL INFORMATION 21 



disease spores being- unable to germinate without 

 these. Unfortunately the farmer has no direct 

 control over the weather, but indirectly he can keep 

 the plants drier by giving them more space. The 

 effect of moisture is well seen in the case of a field 

 of potatoes ; the four rows next to the hedge, almost 

 without exception, suffer more from the Phytoph- 

 tkoJ'a disease than any other part of the field. 

 This is so marked that in certain districts the 

 farmers hold firmly to the opinion that the disease 

 comes from the trees which constitute the hedo^e. 



On the other hand lack of moisture may favour 

 some diseases, e.g. certain forms of leaf curl in 

 potatoes. Again, the moisture content of the soil 

 during the early stages in the growth of swedes may 

 profoundly influence the extent of finger-and-toe 

 disease in the subsequent crop, as is shown in the un- 

 dermentioned case which the author investio-ated : — 



Half of a large field sown 8th June, poor crop, 

 8 1 per cent diseased. 



Half of same field sown 15th June, good crop, 

 1 1 per cent diseased. 



The cultivation, manuring, and previous cropping 

 of the two halves, were the same, but thc^ wc^ather 

 about the time of the first sowing was dry while 

 immediately after the second sowing there were 

 heavy rainfalls on three successive days. 



2. Crowded Cropping. — Most plants are mor(i 

 susceptible to disease when grown closely together : 



