298 EXPEEIMENTS ON POTATOES WITH DIFFERENT MANURES. 



A word may perhaps be said concerning the diseased potato, 

 (C.) The great difference between the composition of this and 

 that of any other, but healthy tuber, appears to be in the amount 

 of water and starch present, the former in much larger, the latter 

 in much lesser quantity. The nitrogenous matter does not seem 

 to be in higher quantity, but consists almost wholly of coagulable 

 albumin. Of course, the higher ratio which the albumin bears- 

 to the starch in this than in a healthy potato accounts in part for 

 the peculiar character possessed by diseased tubers. 



It remains now, after having discussed the merits of the 

 various manures, as affecting the composition of the tuber, to 

 examine the value of the total crops which they have produced. 

 In Table IV., Part I., the value of the crops are there calculated 

 from a definite fixed standard of £3 per ton, no allowance being 

 made for the quality. I have therefore prepared the following 

 somewhat similar Table (VIII.), in which the market value of the 

 average yield is affected by the quality ; the standard employed 

 is Id. for each pound of starch present in the whole crop. 



Table VIII. — Showing the Value of the Experimental Crops as 

 calculated from the Percentage of Starch. 



It will be noticed that the two tables agree remarkably well^ 

 when we remember that the points from which the calculations 

 start are so widely different. 



