32 



In each zone the proportion of dry matter is higher towards 

 the umbilical than the terminal end of the tuber. 



The percentage of nitroj^en in the fresh material tends to de- 

 crease from the skin to the inner cortical layer and to increase in 

 the medullary zone. Thus it increases from zone to zone in the 

 opposite direction to the dry matter. 



Nilroi^-en tends to increase Avith dry matter from the terminal 

 to the innbili(\'il end. The results are : — 



Skin . 



Cortical, outer . 



,, inner 

 Medullary, outer 

 inner 



Average of 3 Medium Tuber 

 Section 



Average of 3 Largi: Tubers. 



Section 



. . --^ 



Microscopical examination shows the starcli j^rains densest in 

 the region of the vascular system, and decTeasinj^- t(n\ards the 

 centre and surface of the tuber. 



A hij^-h ^Q<^r^(t of correlation is found between the specific 

 gravity and percentaL(e of dry matter of whole tuin-rs. 



Vor purposes of samjjlino the method of taking two radially 

 opposed sectors, or diaj^^onally opjiosed eij^hlhs, was far more 

 accurate than the c^orini,'- method. 



