A Study of Quality in Potatoes. 219 



As a result of these investigations we are led to believe that the 

 quality of mealiness of a potato when boiled, and, to a considerable 

 extent, the flavor, is influenced in the main by the following 

 considerations : 



1. The daily range of soil and atmospheric temperature during the 

 growing period. 



2. The degree of ripeness of the tuber when the plant dies. 



3. The physical condition and type of the soil. 



The first two of these considerations have been studied carefully 

 during the past two years, and studies along the same lines are 

 planned for several years to come. The third consideration has not 

 yet been studied experimentally, but is considered a factor at this 

 time, in influencing the quality of potatoes, from general experience 

 and observations. 



Parts of a Potato. 

 In these investigations, while cooking and tasting were the final 

 tests of quality, yet in order to 

 train the judgment and to ascer- 

 tain the physical features or 

 characteristics which might be 

 considered as factors regulating 

 this estimate of quality, the 

 tubers were examined both ex- 

 ternally and internally. If a 

 cross section of a tuber is made 

 and a slice about 2 mm. in 

 thickness from this section is 

 held up to the light, or even 

 carefully examined by reflected Fi«- 17 ^.-Cross-section of tuber showing 

 ,. , . ...the zones. The envelope or skm may 



light, four zones or areas wfll „,j j,, ,,,,^^,-,,d. 



be recognized. (Fig. 174.) Using 



the nomenclature followed by Coudon and Bussard, these are: 



1. The Envelope or Skin comprising the corky covering of the 

 tuber. 



2. The Cortical Layer which is just within the envelope and varies 

 from one-eighth to one-half inch in thickness. This part is generally 

 more dense than any other and is separated from the interior by a 

 well marked ring of fibro-vascular bundles. Within its substance 

 it also contains more fibro-vascular bundles than the other parts. 



3. Within the cortical layer is the External Medullary area which 

 comprises the main starchy part of the tuber. This part varies 

 considerably in uniformity. 



