148 VEGETABLE SUBSTANCES. 



its remedy. The old tuber has been too compact 

 for yielding to the vegetative powers of the plant. 



The curl first made its appearance in this country 

 in the year 1764, in Lancashire, r where potatoes 

 had been first introduced into British field culture, 

 and had been propagated without any change of seed. 

 From Lancashire this disease spread over all the 

 potato districts of Britain, and as the cause and 

 cure were equally unknown, there was a general ap- 

 prehension that the plant would be exterminated. 

 Premiums were offered by different agricultural so- 

 cieties to those who should point out a remedy for 

 a disease so destructive ; in consequence of which 

 many speculations and theories were raised, which, 

 however, led to very little practical utility. 



The discovery of at least a temporary preventive, 

 and therefore of the probable cause, was made, as 

 is believed, more from accident than design, in the 

 neighbourhood of Edinburgh. Some of the growers 

 in that situation were in the habit of procuring seed 

 potatoes from the cold moorland districts, and fields 

 planted with these were free from the curl. Upon 

 inquiry it was found that in those bleak and humid 

 situations, the potato crop was so late that the 

 frost came on and blackened the leaves, while they 

 and the stems were still green, and the tubers of 

 course not ripe. The change of climate was there- 

 fore not the sole cause of prevention, if indeed it 

 was the cause at all, for when the full ripened 

 potatoes were planted in the moors, the curl ap- 

 peared in them, in situations where there was none 

 in the native potatoes. 



It was thus found that the curl could be prevented 

 by using tubers that were not quite ripe. 



A writer in the Gardener's Magazine for May 

 1827, thus ingeniously accounts for this fact : ' The 

 potato tuber is a perfect organized system, in which 

 the circulation regularly proceeds, and if suffered 



