THE POTATO. 263 



The peculiar characteristic of this root is the quantity of 

 starch it contains. The quantity of dry solid matter depends 

 not only on tlie variety but also on the age and maturity, the 

 most mature often having 30 per cent, of solid matter. The 

 quantity of starch is at its maximum in the autumn and ear- 

 ly winter. As the winter advances the starch seems to be con- 

 verted into sugar, and prepared for the support of the grow- 

 ing buds. The nitrogenous, or muscle forming matter, in 

 potatoes, it will be noticed, is small. Hence potatoes should 

 never form the exclusive diet of man or beast. The great 

 value of this tuber is evidently to supply carbon, in the shape 

 of starcli, for the purpose of sustaining animal heat. At the 

 same time, in consequence of the great yield per acre, much 

 more nourishment can be produced from a given amount of 

 land by potatoes than by any of our common crops. Though 

 the nitrogenous matters in a pound of potatoes are small in 

 comparison with those in a pound of wlieat or corn, still an 

 acre of potatoes will furnish one and a half times as much 

 nitrogen as an acre of wheat and four times as much starch. 

 Thus after the introduction of the potato into Ireland the 

 land was capable of sustaining a much larger population, for 

 one acre of this root could form the chief sustenance of a 

 family, whereas it had previously required three or four acres 

 of grain. 



It is worth while to glance a moment at the analysis of the 

 inorganic constituents of the potato, as this will show us 

 what inorganic matters the crop will demand for its support. 

 The ash of this root varies with the different varieties, but 

 generally amounts to a little less than 4 per cent, of the 



