6 
BULLETIN 958, TJ. S. DEPARTMENT OF AGRICULTURE. 
individual hills had been completed and dividing the population into 
25-gram classes. 2 The results are shown in Tables I, II, and III. 
Table I. — Rate of development of potato tubers at Greeley, Colo., in 1916 and 1917. 
[Data from 200 hills of the Rural New Yorker variety dug at 1-week intervals during each season.] 
Time 
after 
plant- 
ing 
(days). 
Number of 
Marketable 
tubers 
(per cent). 
Weight (grams). 
Date of digging. 
tubers. 
Total/ 
Average. 
Largest- 
In- 
Total. 
Average 
per hill. 
Num- 
ber. 
Weight. 
Per 
tuber. 
Per 
hill. 
Tuber. 
Hill. 
per 
hill. 
Season of 1916: 
Aug. 24 
Aug. 31 
Sept. 7 
Sept. 14 
Sept. 21 
Sept. 28 
Oct. 5 
Season of 1917: 
Aug. 16 
Aug. 23 
Aug. 30 
Sept. 6 
Sept. 13 
Sept. 20 
Sept. 27 
Oct. 4 
Oct. 11 
Oct. 18 
72 
79 
86 
93 
100 
107 
114 
64 
71 
78 
85 
92 
99 
106 
113 
120 
127 
1,085 
1,151 
1,220 
1,169 
1,295 
1,125 
1,048 
863 
870 
922 
957 
960 
987 
928 
984 
935 
931 
5.4 
5.8 
6.1 
5.8 
6.5 
5.6 
5.2 
4.32 
4.35 
4.61 
4.79 
4.80 
4.94 
4.64 
4.92 
4.68 
4.66 
2.4 
34.8 
49.6 
•65.3 
66.4 
71.4 
75.5 

5.2 
33.2 
59.9 
70.0 
69.1 
73.5 
74.1 
79.4 
79.7 
7.1 
61.2 
80.-1 
91.7 
91.7 
94.1 
95.4 

14.7 
60.2 
87.0 
95.7 
96.2 
97.3 
97.0 
97.6 
97.7 
37,235 
79, 028 
114, 351 
150, 987 
179, 480 
193, 637 
197, 123 
10,843 
31, 579 
65,064 
107, 746 
142, 470 
162, 745 
186, 460 
218, 035 
222, 055 
228, 755 
34.3 
68.7 
93.7 
129. 2 
138. 6 
172.1 
188.1. 
12.6 
36.3 
70.6 
112.6 
148. 4 
164.9 
200.9 
221.6 
237.5 
245.7 
186.2 
395.1 
571.8 
754.9 
897. 4 
968.2 
985.6 
54.2 
157.9 
325.3 
538.7 
712.4 
813.7 
932.3 
1, 090. 2 
1, 110. 3 
1, 143. 8 
160 
299 
417 
715 
631 
852 
853 
55 
180 
255 
409 
735 
582 
815 
903 
991 
875 
418 
856 
1,135 
1,449 
1,861 
1,826 
2,079 
142 
366 
670 
1,105 
1,480 
1,745 
2,270 
2,100 
2,280 
2,020 
' '208.' 9 
176.7 
183.1 
142.5 
70.8 
17.4 
' "i03.*7 
167.4 
213.4 
173.7 
101.3 
118.6 
157.9 
20.1 
33.5 
A study of the data presented in Table I brings out many points of 
interest. It will be seen that practically the entire crop of tubers was 
set at the beginning of the period of tuber development, probably 
within the space of a very few days. The data, however, show a slight 
increase in the number of tubers up to and including the third digging, 
in September; also a decrease after that period, so that the numbers 
at the beginning and at the end of the sampling period are very 
nearly the same. A possible explanation of this fluctuation is that 
the numbers employed may not have been large enough to eliminate 
the so-called experimental error. On the other hand, it seems quite 
probable that the small increases indicated in the records as occurring 
early in the season were actual. Toward the end of both seasons it 
was observed while digging the hills for the statistical studies that 
some of the very small tubers slightly below half an inch in diameter 
had shrunk considerably, and occasional evidences of the almost 
complete disintegration of these small sizes were found. If this con- 
dition occurred in tubers originally above the half-inch size, which 
would have been saved and counted at the earlier dates of sampling, 
it would account for the apparent decrease in the number of tubers 
toward the end of the season. Further studies are needed to deter- 
mine whether this is the cause. 
In both years there was an increase in the weight per hill and in 
the average weight per tuber throughout the entire period of the 
2 Twenty-five grams are about equivalent to 0.88 ounce avoirdupois. 
