THE POTATO. 157 



immediately by the air of the atmosphere, the consequence of which 

 is, that they behave like all other vegetable juices left to themselves, 

 they become putrid. The putrid odor and the acrimony which are 

 developed in the frosted potato, are by so much the more remarkable 

 as a certain layer which exists immediately under the skin, and pre- 

 sents various shades of color, tawny red or violet, is more highly 

 develo})ed. The tissue of this layer, examined under the micro- 

 scope, was found by M. Payen to be totally without starch, but it 

 contains the greater part of the (strong-smelling) coloring principles.* 

 These principles, which give such unpleasant qualities to frosted 

 potatoes, appear to be soluble, or at least destructible by long expo- 

 sure to the open air. Thus, if frosted potatoes be spread upon the 

 ground and exposed to the weather, they dry spontaneously, become 

 hard, whitened, and they may then be preserved for a very long 

 time. This method of making use of frosted potatoes Jias been 

 several times employed in practice, and it might perhaps be recom- 

 mended for general adoption, were it only ascertained that by such 

 treatment the tubers did not lose a great proportion of their most 

 nutritive principle, viz. albumen. However this may be, it is by a 

 similar process that the natives of the Andes of Peru preserve and 

 render more transportable the tubers which form a principal element 

 in their food. In the steepest parts of the Peruvian Cordillera, 

 nearly at the superior limit of vegetation, where a miserable field of 

 barley and of Quinoa is only seen here and there, various tubers are 

 collected in the hollows of the surface, such as the Maca^ the Oca^ 

 the Ulluco. To preserve these they are exposed for several days to 

 the alternate action of the frost and of the sun. At these great 

 elevations, which are upwards, of 13,120 feet above the level of the 

 sea, it always freezes in clear nights when the air is moderately 

 calm. During the day the rays of the sun, which strike with great 

 force, dry the tubers rapidly, the watery juices of which have been 

 shed into the amylaceous tissue by the effect of the preceding night's 

 frost. Thoroughly dry, they may be kept for more than a year by 

 being stored and protected from moisture. Various other modes of 

 preparation are practised in regard to the other kinds of tubers which 

 have been mentioned. By previously boiling the common potato, 

 pealing it, and exposing it alternately to the frost of the night and 

 the heat of the sun, until it is completely dry, the Indians prepare 

 one of their most agreeable and wholesome articles of subsistence. 

 The potato thrives in soils of very various kinds, provided it be 

 sufficiently fertile, and the climate is favorable. This crop, like the 

 beet, is generally planted in freshly manured ground, and is suc- 

 ceeded in the autumn by a winter crop of corn — wheat or rye. The 

 potato is set when apprehensions of frost are no longer entertained .. 

 in the east of France the setting is generally ended about the mid- 

 dle of May. In Alsace the cuttings of the potato are dropped at 

 the distancB of about a foot from each other in furrows made by the 

 plough, the furrows being from 18 inches to nearly 2 feet apart* 



* Payen. Journril of Practical Agriculture, vol. i. p. 4S8, 



14 



