32 
BULLETIN 1248, TJ. S. DEPARTMENT OF AGRICULTURE. 
A more striking comparison of the two sets of data relating to the 
Irish Cobbler in Virginia and Maine is found by placing in parallel 
columns (Table 16) the average performance of 300 sets, during the 
4-year period from 1915-1918 as regards the total number of stems 
and tubers. The average number of stems and tubers produced by 
the individual set is also given. A study of these data shows, as in the 
data previously presented, a distinct and progressive ratio of increase 
of both stems and tubers by the large over the small set and of the 
whole tubers over the cut seed. One of the most interesting features 
of these data is found in a comparison of the relative number of 
stems and tubers produced from sets of the same size in the Virginia 
and Maine experiments. Those grown in Maine averaged 42 per 
cent more stems but not quite 12 per cent more tubers than those 
grown in Virginia. This difference in behavior may have been due 
to the longer period of storage to which the seed planted in Maine 
was subjected. The average planting period at the Virginia Truck 
Experiment Station was from February 27 to March 7, whereas the 
planting at Presque Isle, Me., occurred usually between May 15 and 
25, or from 8 to 10 weeks later. The Virginia experiment, in other 
words, was planted with seed stock which had just completed its 
deep-rest period; whereas the stock planted in Maine was m a more 
active stage physiologically, which induced a larger number of eyes 
to germinate and produce stems. There is, of course, another factor, 
that of the temperature of the soil. During March it is usually too 
cool to stimulate the development of sprouts from weak or more or 
less dormant eyes. 
Table 16. — Relative influence of the size of set on the production of stems and 
tubers, as shown by the record of 300 plants of the Irish Cobbler potato in Vir- 
ginia and Maine for the 4-year period, 1915-1918. 
Weight 
of set. 
Norfolk, Va. 
Presque Isle, Me 
Kind of set planted. 
Total number. 
Average per set. 
Total number. 
Average per set. 
Stems. 
Tubers. 
Stems. 
Tubers. 
Stems. 
Tubers. 
Stems. 
Tubers. 
Whole: 
2-ounce...: 
Ounces. 
2 
3 
4 
5 
6 
1 
1* 
U 
1* 
833 
95S 
1,216 
1,378 
1,566 
554 
663 
753 
824 
876 
489 
497 
524 
584 
2,778 
3,174 
3, 571 
3,912 
4,131 
2,104 
2,227 
2,492 
2, 674 
2,658 
1,571 
1,862 
1,999 
2,141 
2.78 
3.20 
4.05 
4.59 
5.22 
1.85 
2.21 
2.51 
2.75 
2.92 
L63 
1.66 
1.75 
1. 95 
9.26 
10.58 
11.90 
13.04 
13.77 
7.01 
7.42 
8.31 
8.91 
8.86 
5.24 
<>. 2 1 
(i. 66 
7. 11 
1,162 
1,500 
L845 
2,010 
2, 239 
418 
942 
1,137 
1,242 
1,318 
630 
697 
739 
789 
3,040 
3,495 
3, 938 
4. 204 
4,546 
2, 250 
2,583 
2, 945 
3,113 
3,317 
1,827 
2, 098 
2, 199 
2,113 
3.87 
5.00 
6.15 
6.70 
7.46 
1.39 
3.14 
3.79 
4.14 
4.39 
2.10 
2.32 
2. 4('» 
2.63 
10. 13 
3-ounce 
1 1. 65 
4-ounce 
13. 13 
6-ounce 
14.01 
6-ouncc 
15. 15 
Halved: 
2-ounce.. 
7.50 
3-ounce 
8.61 
9 82 
5-ounce 
! I . 38 
6-ounce 
11. 00 
Quartered: 
3-ounce... 
6.09 
4-ounce 
5-ounce 
7. 33 
6-ounce 
7.01 
FREQUENCY CORRELATIONS OF STEMS. 
A study of the occurrence of the same number of stems from sets 
of given sizes based on the average performance of the number of 
[risn Cobbler plants studied at the Virginia Truck Experiment 
