1873.] THE POTATO DISEASE. 493 



its development were favourable, in the same way that mildew can be 

 produced upon the Vine by certain treatment, and made to disappear 

 when that treatment is altered. I confess to having little or no hope 

 that we shall ever be able to eradicate the disease altogether, though we 

 may check it ; but who can say that such a mysterious disease may not 

 disappear eventually in the same mysterious manner that it came 1 



It is certainly not a little humbling to tliink that the painstaking 

 investigations and discoveries which have been made on the subject 

 should have led as yet to no practical results. 



The disease was at first attributed to the cold and wet by every 

 cultivator of the potato ; and although that may be only the indirect 

 cause, it has always appeared to practical minds as the evil against 

 which all preventive measures must be directed ; and no discoveries 

 which have been made, though they have made us more familiar with 

 the characteristics of the disease, have altered this view of the case. 

 If the rainfall is above the average at a certain time of the year, the 

 farmer knows by sad experience that all hopes of a sound crop are at 

 an end, and vice versa, if the summer is warm and dry. We never 

 knew of an instance in which protection from the wet was afforded, 

 either accidentally or otherwise, but the crop was good. The first 

 instance of this kind which came under our notice was remarkable, 

 as showing that dryness of the soil, whether that is secured by drain- 

 age or otherwise, is a preventive. In a quarter of potatoes which 

 I had to do with, there grew a tree — an ash, if I recollect aright. It 

 was a round headed tree, with a stem about 8 or 9 feet high, so that 

 the ground could be cropped very nearly up to the stem. When the 

 potatoes were taken up, they were very badly diseased, except those 

 under the tree ; and they, though smaller, were nearly every one 

 sound. What with the shelter afforded by the branches, and the 

 absorption of the moisture from the ground by the tree-roots, which 

 were massed near the surface so thickly that a fork could scarcely be 

 used, the soil was as dry and mealy as possible. Now there was no 

 shelter here to speak of from anything but the wet, for owing to the 

 height of the stem, the potatoes under the tree were exposed fully to 

 the blast from the south, east, and west. I attributed the dryness of 

 the soil chiefly to the roots of the tree. It is well known how 

 surface-rooting trees rob the soil of its moisture. Since then, many 

 instances of the same kind have come under our observation, as they 

 must that of others. Last year, a farmer in this neighbourhood 

 planted a quantity of Irish Eocks in a field where the soil was thin 

 and dry. In October they turned out a sound and excellent crop. 

 Part of the same lot was planted on the same formation, but in the 

 hoUow, where the soil was deeper and wetter, and they turned out 



