246 Drij Midler and Nitrogen in the Potato Tuber 



The Distribution of Nitrogen. 

 Nitrogen determinations in the different zones of six tubers individu- 

 ally gave the following results: 



Table IX. Percentage of Nitrogen. 



Tubor 1 2 3 4 5 6 



Fresh Dry Fresh Dry Fresh Dry Fresh Dry Fresh Diy Fresh Dry 

 Zone basis basis basis basis basis basis basis basis basis basis basis basis 



Skin 0-4U 3-22 0-12 2-96 0-37 2-62 0-35 2-34 0-36 2-41 0-37 2-48 



Cortical, outer ... 0-38 1-53 0-35 1-39 0-39 1-55 0-36 1'52 0-36 1-52 0-33 1-41 



inner ... 0-33 M4 0-30 104 0-33 1-14 0-33 M3 0-32 1-10 0-29 102 



Medullary, outer... 0-37 1-43 0-32 1-24 0-36 1-40 0-32 1-24 0-36 1-39 0-27 1-07 



„ " inner... 0-40 1-96 0-32 1-57 0-40 1-96 0-31 1-69 0-37 200 0-31 1-66 



Determinations on two sets of six tubers gave the following averages : 



Table X. 



Six small tubers Six medium tubers 



Zone Fresh basis Dry basis Fresh basis Dry basis 



Skin 0-40 2-82 0-40 2-62 



Cortical, outer 0-41 1-63 0-35 1-49 



inner 0-29 1-00 0-33 M3 



Medullary, outer 0-34 1-30 0-33 1-30 



inner 0-38 1-89 0-34 1-84 



The variation of nitrogen in the fresh material of the different zones 

 is relatively small and is not always quite the same in different tubers. 

 On the whole the skin tends to contain the highest proportion and this 

 decreases to the inner cortical layer and increases again in one or both 

 medullary zones. Thus a tendency appears for the percentage of nitrogen 

 in the fresh material to vary from zone to zone in the opposite way to the 

 dry matter, so that the inner cortical, the zone richest in dry matter, is 

 also poorest in nitrogen. 



When nitrogen is calculated to the dry basis it follows that the 

 variation from one zone to another is much more markedly in the opposite 

 direction to the dry matter. 



The distribution of nitrogen in the zones of the terminal, inter- 

 mediate and umbilical sections determined un three groups of three 

 tubers whose perceiatage dry matter is given in Appendix Table III, was 



Table XI. 



Average of 3 small tubers Average of 3 medium tubers .Average of 3 large tubers 

 Section Section Section 



Zone 12341234123 



Skin 0-40 0-42 M3 0-42 0-26 0-40 0-45 0-45 0-45 0-36 0-51 0-54 



Cortical, outer ... 0-35 0-36 0-37 0-40 0-33 0-33 0-34 0-37 0-33 0-34 0-35 0-41 



inner ... 0-29 0-29 0-32 0-32 0-29 0-.30 0-33 0-35 0-32 0-37 0-35 0-38 



Medullary, outer... 0-30 0-32 0-34 0-29 0-30 0-34 0-37 0-38 0-30 0-35 0-44 0-40 



inner... 0-33 0-30 0-311 0-40 0-34 0-32 0-36 0-36 0-32 0-32 0-30 0-38 



