BULLETIN 958. U. S. DEPARTMENT OF AGRICULTURE. 
with the White Star variety in 1893, harvested at 10-day periods 
from August 2 to September 22, and with the White Star and Dela- 
ware varieties in 1898, harvested at the same intervals from August 
4 to October 6. There was found to be an increase in yield up to the 
time of the last harvest. A considerable part of the yield of tubers 
of marketable size developed after the 1st of September. 
Kohler (7. p. 109-111), in experiments with the Early Ohio variety 
in 1909, by digging tubers at 7-day intervals from July 31 to August 
30 obtained an in- 
crease in weight at 
the rate of 7.18 bush- 
els per acre each day. 
The gain was also 
found to be very uni- 
form throughout the 
period, with the ex- 
ception of a slight 
drop at its end, which 
was attributed to the 
loss of foliage as the 
result of disease. 
Werner (11, p. 20- 
21) in 1917 found 
that tubers of the 
Green Mountain va- 
riety harvested Aug- 
ust 10, 20, 30, and 
September 8 and 11 
showed daily in- 
creases of 2.34 bush- 
els per acre during 
the first 10-day inter- 
val, while the in- 
creases for the last 3- 
day period were at the 
^J 
- 
'■ f * 
*> m 
31- 
— ~~ 
* 
i* 
rate of 
bushels. 
Fig. 1.— Plant of the Irish Cobbler variety of potato, showing the 
tubers borne on short stolons. 
Wilfarth, Romer, 
and Wimmer (12) 
found, in both field and pot experiments with the Geheimrat Theil 
variety, a fairly constant rate of increase in the weight of tubers 
during the four periods of growth which were studied. Analyses 
showed comparatively small changes in the percentages of the min- 
eral constituents throughout the season, though there was a slight 
trend toward a decrease until the fourth period, when a very small 
increase was indicated. 
Experiments conducted in boxes with the Up-to-Date variety, by 
Ramsav and Robertson (9), where four harvests were made at inter- 
