534 EXPERIMENT STATION RECORD. 



A study was also made of the four physical divisions of the tuber, these being 

 designated from outside to inside as skin, cortical layer, outer medullary layer, 

 and inner medullary layer. The varieties used in this connection were Rural 

 New Yorker No. 2 and Carman No. 3. It was found that the dry matter is 

 quite variable and regularly decreases from the outside to the inside of the three 

 inner zones. The total nitrogen content is only slightly variable, although 

 showing a regular increase to the inner medullary layer on the dry basis. Ash 

 determinations varied little from 0.90 per cent on the fresh basis, indicating 

 a higher carbohydrate content in the cortical layer and a low one in the inner 

 medullary layer. This is considered as showing that there is a difference in the 

 lime of cooking i:i the different zones. A number of methods of sampling were 

 tried, and the most satisfactory results were secured by cutting a cylinder with 

 a ]2 mm. cork borer parallel to the long diameter but a little to the side. Varia- 

 tion in niti'ogen content did not show a noticeable effect on quality, although it 

 appears that extremely high nitrogen might make the flavor more in-onounced. 

 On the other hand, it was found that there is a lower limit in the amount of 

 diT matter or more probably of carbohydi'ates, below which tubers can not l»e 

 of good quality. In Rural New Yorker No. 2 it was found to be about IS per 

 cent, or probably about 15 per cent of starch. 



In observations to determine a correlation between physical structure and 

 quality it was found that anatomical difference is a varietal character, the 

 difference between varieties being very great. The difference in quality within 

 the variety, however, was found to be almost as great as the difference between 

 varieties. This method of determining the quality of the tuber through its 

 anatomical structure can not be used for selecting potatoes for the table because 

 it is necessary to cut the tubers. In enumerating and discussing other factors 

 influencing quality, it is pointed out that the number of eyes has a marked effect, 

 due to the fact that the internal medullary extends a branch to each eye. This 

 fact makes the quality vary inversely with the number of eyes. In a count of 

 219 tubers of Rural New Yorker No. 2 the number of eyes varied from 7 to 2S. 

 In connection with this work 189 tubers of this variety were analyzed and a 

 large number found to be of very good cooking quality, although the average 

 200, and 400 lbs. per acre. 



Investigations on the influence of fertilizers on quality showed that the 

 quality grew markedly better where potassium chlorid was applied at the i-ate 

 of 300 lbs. per acre, but apparently little difference resulted from doubling the 

 applications of phosphorus in the form of bone meal given at the rate of 100, 

 200. and 400 lbs. per acre. 



A microscopical examination in connection with a study of the influence of 

 maturity on the quality showed that the starch grains in the cells of the imma- 

 ture tubers are small in size and few in number. In the cortical and outer 

 medullary layers of mature tubers the starch grains averaged about 75/^ and 

 were found as large as 10.5/^, while in immature tubers under an ounce in 

 weight the starch grains averaged only 25;u. The composition of tubers of dif- 

 ferent degrees of maturity was determined and from the results it is concluded 

 that quality depends upon homogeneous anatomical structure, dry matter con- 

 tent, and degree of maturity. In general the quality increases with the thick- 

 ness of the cortical layer and decreases as the number of eyes increases. The 

 dry matter content must be such that the cooked starch fills the cells to the 

 bursting point. The degree of maturity is affected by all factors of soil physics, 

 soil fertility, cultivation, and climate during the growing period. 



In studying the variation of the potato in chemical composition as a basis for 

 its improvement it was found that the nitrogen content does not vary directly 

 with the number of eyes, that it is not correlated with particular shnpes, that 



