UNITED STATES DEPARTMENT OF AGRICULTURE 
AJt^wil 
BULLETIN No. 958 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. 
August 22, 1921 
DEVELOPMENT OF TUBERS IN THE POTATO. 
By Charles F. Clark, Horticulturist, Office of Horticultural and Pomological 
Investigations. 
Scope of the experiments 
Work of previous investigators 
Description of the tuber-bearing parts 
Details of the experiments. 
Summary 
Literature cited 
Page. 
4 
25 
27 
SCOPE OF THE EXPERIMENTS. 
The conditions which attend the setting and subsequent develop- 
ment of the tubers of the potato (Solanum tuberosum L.) are of 
interest not only to the plant physiologist but also to the practical 
grower, as a knowledge of the relation of these factors to crop pro- 
duction may, to a certain extent, be put to practical use. 
The experiments described in the following pages were conducted 
at the Colorado Potato Experiment Station, Greeley, Colo., during 
the seasons of 1916, 1917, and 1918. A few minor observations were 
also made in Maine in 1919 for the purpose of verifying the conclusions 
previously reached relating to the time of the beginning of tuber 
formation. 
While these studies could profitably be extended to cover a longer 
period and include a greater number of varieties and a wider range 
of environmental conditions, it is deemed advisable to place on 
record the results obtained up to the present time, since these lines 
of investigation have been temporarily suspended. 
WORK OF PREVIOUS INVESTIGATORS. 
While very extensive studies of the potato plant have been made, 
the development of tubers has received comparatively little atten- 
tion. Jones and Orton (5, p. 155-156) 1 report results obtained 
1 The serial numbers in parentheses refer to 
47473°— 21— Bull. 958 1 
Literature cited" at the end of this bulletin. 
