THE POTATO. 149 



to ripen will then tend to decay ; but if separated 

 before ripe from the stem or stalk which furnishes 

 it with blood or fruit-sap, descending from the 

 leaves, the circulation of the blood-sap is suddenly 

 arrested. The ripe potato, having performed all 

 its operations, becomes more inert ; but the circu- 

 lation of the sap in the unripe tuber having been 

 stopped, it starts more readily, and with greater 

 vigour, when planted ; the one appears to die, worn 

 out with age, the other seems accidentally to have 

 fallen asleep, and when awakened, possesses an un- 

 spent vigour and energy.' p. 317. 



That over-ripeness is the principal cause of the 

 disease, has been found by experience to be so much 

 the case, that out of the same potato it is possible 

 to make some sets that will, and others that will 

 not, produce the curl. The portion of the tuber 

 that is nearest to the cord by which it is fastened 

 to the plant, ripens first, as any one may observe, 

 especially in an elongated potato, where the root 

 end is often so mealy as to fall to powder, when 

 the top 'or thick end is soft and waxy. If such 

 a potato be taken when only the small end is ripe 

 enough to boil mealy, the eyes upon another of the 

 same parcel that are upon the waxy part, will all 

 produce sound plants, while curl may appear in 

 those which are taken from the mealy end. The soil 

 and mode of culture may have likewise some effect 

 in producing this evil. Experience has shown that 

 high culture and stimulating manure tend more to 

 produce curl than poorer treatment, that this dis- 

 ease is less frequent in new lands than in those 

 which have been long in culture, and that it seldom 

 appears in cold and upland places. 



The economy of this article of food, as compared 

 with wheat, is seldom questioned, although doubts 

 have been raised even as to its comparative cheap- 



VOL. xv. 13* 



