AS ILLUSTRATED BY THE POTATO MURRAIN. Igl 



actual variations. The amount in water and ashes in diseased 

 potatoes is absolutely more marked, in starch less so than in those 

 which are sound. The albumen is relatively more marked in 

 proportion as well to the starch only, as also to the collective 

 non-nitrogenous constituents. 



Most chemical analyses of diseased potatoes are useless inas- 

 much as they are made without any knowledge what is to be 

 gained by analysis, and what questions are to be answered by it. 

 One of the best and most worthy of confidence is that of Janssen 

 and Schacht, but, like all similar analyses of plants, is deficient 

 as regards the nitrogenous constituents. According to this the 

 proportion of albumen to starch in sound potatoes is as 1 : 31,8 ; 

 in diseased as 1 : 28,7 ; to starch, cellulose, gum and sugar col- 

 lectivelj^ — in the sound as 1 : 25,8, in diseased as 1 : 36,6. 



It is remarkable that diseased potatoes, according to this ana- 

 lysis, which in this respect is very careful, contain more cellu- 

 lose than those which are sound, and if the cellulose is set down 

 at unity, the following jiroportions are obtained, which perhaps 

 approximately correspond with the proportions in the single cells. 



In sound potatoes the starch is to the water as 1 : 3,5 ; in dis- 

 eased as 1 : 4,4. 



The best analysis of the ashes is that of Petzholdt. 

 In 1000 parts of fresh 



Waxy Potatoes.. Table Potatoes. 



Sound. Diseased. Sound. Diseased. 



Water . . 761' . . 778- 753- . . 7G0- 



In 1000 parts when dried at 100° C. 



The proportions of the particular constituents of the ashes are 

 more important here than the absolute quantities. These give, 

 when the alkalies are set down at unity, — 



o 2 



