468 



Potato Leaf-curl. 



[NOV., 



seriously as it deserves. From the first re -appearance of 

 curl some ten years ago, growers have suspected over ripeness 

 as being largely responsible, but it did not occur to them at 

 once to make comparative tests. When these were carefully 

 conducted it was found that immature seed gave more vigorous 

 plants than did ripe seed. In point of fact, there can be very 

 little doubt but that a considerable measure of the success 

 of Scottish seed is due to absence of complete ripeness. In 

 Scotland, with its comparatively cool and humid climate, the 

 plants continue growing until they are cut by frost, and it 

 frequently happens that the first visitation of frost comes 

 while the leaves are still green. Those who have had oppor- 

 tunities of going over the seed potato stores of some of the 

 principal Scottish dealers will have observed the great pro- 

 portion of rubbed tubers, which give clear evidence of the 

 fact that when they were taken up they were unripe and the 

 skins unset. It would not be safe to argue from this that 

 immaturity is everything, and that south of England growers 

 have nothing to do but to lift a portion of their crop for seed 

 purposes while still in full growth in order to secure heavy 

 crops. They would certainly be wise, however, to make 

 experiments. A few trials conducted with care might give 

 convincing proof of the real value of immature seed. 



The Soil. — We may now turn to the question of the soil. 

 This is of almost equal importance with the seed. That a 

 fresh, vigorous stock may give fairly satisfactory results, 

 even where the ground is not of the best, and where the general 

 circumstances are unfavourable, is acknowledged. But if 

 such unfavourable conditions are maintained year after year 

 the stock will lose its vigour much more rapidly than it would 

 do if proper conditions were provided for it. Unquestion- 

 ably the first essential in the soil is an adequate supply of 

 moisture, but if a site is chosen which would be saturated 

 in a wet season the potatoes will be liable to disease in the 

 form of Phytophthora infestans, which will cause the grower 

 a loss quite as severe as that accruing from curl. The moisture 

 of a wet site is not the moisture which is required in order 

 to keep potatoes free from curl. It is rather the moisture 

 of the deeply worked, well-tilled soil. Land that is thoroughly 

 prepared and regularly cultivated throughout the growing 



