220 Bulletin 230. 



4. The Internal Medullary area occupies the central part of the 

 tuber and often having branches permeating the external medullary 

 area. This area is usually more or less translucent, inasmuch as it 

 contains mostly water and but little starch. 



According to Coudon and Bussard, these parts are divided in the 

 potato body in the following percentages: 



Envelope (av. two varieties) 8 . 79 per cent. 



Cortical layer (av. two varieties) 36 . 19 per cent. 



External medullary area (av. five varieties) 34 . 17 per cent. 



Internal medullary area (av. five varieties) 14 . 96 per cent. 



In our examination the following features were noted: 



1. Surface and texture of skin — Surface uneven with deep eyes; unde- 

 sirable for market considerations. Texture of skin: Netted, indi- 

 cating a degree of maturity, and, as a general rule, good quality. 

 Smooth, indicating a degree of immaturity, hence poor quality and 

 tendency to undesirable flavor. Scabby, often mealy and of good 

 color, but undesirable for market considerations. Exposed, heavy 

 and soggy in cooking and of poor color with undesirable flavor. 

 Compound, indicating non-uniform growth and development; non- 

 uniform in cooking quality and often of poor flavor. 



2. Cortical layer — Thick and dense (Fig. 174); tubers of poor 

 quality, indicating that they grew near the surface where the temper- 

 ature and moisture conditions ^^■ere more variable. Thin and more 

 translucent, indicating soil and climatic conditions more favorable 

 to development. Density in this portion is due, to some extent, 

 to the presence of fibro-vascular bundles and cellular contents 

 other than starch; but we believe it is brought about in a greater 

 measure by the thickness and opacity of the cell walls. The con- 

 tents of the cells of this portion as compared with that of the cells 

 of other portions has not been worked out, but according to Coudon 

 and Bussard* not only are fibro-vascular bundles more abundant, 



, but this portion is richer in nitrogenous matters. 



Just how far thickness and coarseness in this portion may be due 

 to the influence of moisture and temperature in the soil cannot be 

 stated at the present time. 



3. External medullary area — Uniform, indicating an even distribu- 

 tion of starch in the cells and also of the starch-containing cells 

 throughout the part. Non-uniform, indicating an uneven distribu- 

 tion of starch cells interspersed with water areas. It was generally 

 observed that uniformity in this part of the tuber was found in 

 tubers which seemed to have grown in favorable conditions of tem- 



* Annales, etc., pp. 257 and 269. 



