438 



BULLETIN No. 127. 



[August, 



For calculating total nitrogenous matter we have used Frisby's 

 and Bryant's (38) factor of 5.5 times the total nitrogen. The 

 proteid nitrogen is probably about 55 percent to 60 percent of these 

 numbers, but as it is still questionable as to 'what dietetic value 

 should be placed upon non-proteid forms of nitrogen, they were 

 not determined. The total nitrogenous matters are reported, cal- 

 culated to the water free material. The extremes are 6.63 percent 

 and 15.69 percent. 



TABLE 15. VARIATION IN TOTAL NITROGENOUS MATTER IN RURAL NEW YORKER 

 No. 2, CROP OF 1901. DRY BASIS 



This table shows a surprising variability in composition in 

 potatoes of the same variety. The extremely high percentage of 

 nitrogenous constituents shows that there may be a basis for the 

 origination of a variety equal in proteid content to a number of 

 the varieties of dent maize now grown, could a variety with the 

 composition of the highest fluctuations be perpetuated. Certainly, 

 in this variety at least, the tubers do not deserve to be ranked as 

 solely a starch food. 



A number of points were observed in looking over the complete 

 data which are too bulky to publish. 



1. The nitrogen content does not vary directly with the num- 

 ber of eyes. Therefore, in potatoes of the same size, many stems 

 have no greater amount of nitrogen to draw upon in sprouting, 

 than have a few. 



2. Variations in nitrogen content are not correlated with par- 

 ticular shapes. 



3. Smaller, younger tubers are richer in nitrogen; that is, 

 there is stored early in the formation of the tuber a relatively larger 

 proportion of the total nitrogen than of starch. 



4. The error in determining starch from specific gravity tables 

 is much greater than is generally supposed. For example, tuber 

 No. 82 contains 14.32 percent nitrogenous matter, specific gravity 

 1.090; while tuber No. 69 contains 7.39 percent nitrogenous mat- 

 ter, specific gravity 1.091. 



