242 SCIENCE AND FRUIT GROWING 



of action which has already been taken, instead of determining 

 what that course shall be, must stand discredited, even before 

 being made. 



A blind advocacy of spraying is naturally accompanied by 

 exaggerated pictures of the advantages to be gained by it, and 

 exaggeration always ends in injuring the cause which it is supposed 

 to aid. In an habitually wet climate, such as that of Ireland, 

 where the potato disease is always more or less virulent, the 

 average benefit resulting from spraying is, no doubt, consider- 

 able ; but it is much less so in the drier climate of England, and, 

 indeed, spraying here is not always attended with any benefit 

 at all. It would be unsafe to draw general conclusions from 

 results obtained in any one locality, but, though those obtained 

 at Woburn must be open to the objection of localisation, they 

 are, in other respects, more varied than is generally the case. 

 They extend from 1895 to 1917, and, whilst many of the series 

 apply to crops grown on the heavy soil of the farm, which is not 

 favourable for potato growing, the more extensive series were 

 made on the light sandy soil at the adjacent farm of the Royal 

 Agricultural Society. The number of varieties examined in 

 any one season ranged from fifteen downwards, and the number 

 of sprayings applied to the various plots in each season were 

 generally one, two and three in the different plots. The nature 

 of the fungicide was also varied, being in most cases ordinary 

 Bordeaux mixture, Bordeaux paste or one of the forms of Bor- 

 deaux mixture sold in the dry form, whilst in a few cases Burgundy 

 mixture was used. The average percentage increase in the 

 yield of sound tubers produced by spraying was as follows 



1895 . . 12 1913 . . 8 



1896 .. 3 1914 .. 9 



1910 . . 29 1915 . . 20 



1911 . . 3 1917 . . - 4 



1912 . . 10 Mean 8*2 



In 1912 one of the three series which were made yielded the 

 high value of an increase of 150 per cent., but, as there were excep- 

 tional conditions applying to that series, it is safer to omit it, 

 and base the annual value on the other two series. The general 

 mean, as will be seen, is an increase of a little over 8 per cent, 

 in the crop, rising on occasions to nearly 30, but, on the other 

 hand, being often negligibly small, and sometimes even negative. 



These values are sufficient to show the necessity for not 

 drawing conclusions from the results of one year's trials only; 



