FUNGOID DISEASES OF PLANTS 135 



be quite wrong. It was P. infestans, the author of the 

 Irish potato famine of 1845, and the consequent Corn 

 Riots took the matter at once beyond the pale of pohte 

 debate. When people cried out, " The Hunger is upon 

 us " it was time to drop talldng. The famine was caused 

 by'p infestans alone, which swept hke a scourge through- 

 out Ireland and reduced the late crop of potatoes to 

 one mass of putrefaction in two short weeks, leaving six 

 milUons of people to face the winter on practically nothing. 

 No such deadly warning had ever occurred before ot 

 the dangers of leaving a large population almost solely 

 dependent for their food upon a risky exotic plant. At 

 that time very httle was known of the nature and cause 

 of the Blight, but to-day, by the aid of sprayers and 

 Bordeaux mixture, we may claim to a large extent that 

 the " bhghter " is bUghted. No country, however, should 

 at any time be entirely dependent for its sustenance 

 upon the potato, excellent as its food value is. The 

 only food-plant which we should pin absolute faith upon 

 is wheat, which Homer calls " the marrow of men." 

 If that ever fails us on a grand scale, the position of the 

 human race at large will be precarious indeed. 



With regard to the use of Bordeaux and Burgundy 

 mixture for potato disease, it should be pointed out that 

 these remedies cannot cure, they are only a protection 

 against attack. Hence the crop must be carefully watched 

 and the spraying must be done in time. It should be 

 started at the end of May for earhes in the West of 

 England, in the middle of June for late crops there and 

 in South Wales. In a word, follow the season wherever 

 you are. The *' Riviera " counties and the Sunny South 

 want it before the end of June, London and the Home 

 Counties by the middle of July, and further north before 

 the end of that month, in aU cases as soon as the leaves 

 and haulms are well developed. It must be repeated 

 at times in the event of heavy rains. 



■The Wart Disease or Black Scab of potatoes is mor^ 



