82 THE JERUSALEM ARTICHOKE CROP. 



in the potato and the Jerusalem artichoke respectively, ap- 

 pear to be about the same. There is but little difference be- 

 tween these in the amounts of their nitrogen compounds, 

 but an important difference exists in the constitution of their 

 other substances; in the potato they exist chiefly in the 

 form of starch, while in the Jerusalem artichoke they are 

 represented by a peculiar form of sugar. This difference 

 in their proximate composition -no doubt has an influence 

 upon their keeping properties, and accounts for the fact 

 that the Jerusalem artichoke can stand the low tempera- 

 ture of the soil in winter better than the potato. When 

 potatoes are frosted the cells are ruptured by the expansion 

 of their contents, fermentation is at once set up, and the 

 starch becomes gradually changed into sugar, occasioning 

 that sweet taste peculiar to frosted or germinating potatoes. 

 In the Jerusalem artichoke the sugar particles are arranged 

 differently to the starch globules of the potatoes, and are 

 not susceptible in the same way to the influence of low 

 temperatures. Under a high temperature, again, the 

 saccharine compounds enter far more readily into fermen- 

 tation than those consisting of starch ; and even under a 

 moderate and dry temperature, the starchy tuber of the 

 potato would probably be preserved without injury for a 

 longer period than the saccharine tuber of the Jerusalem 

 artichoke. 



