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1907] DOUGLAS—INTUMESCENCES ON POTATO 247 
time sufficient to bring it to the shade of a painted standard. The 
time which is necessary to produce the given shade may then be 
compared with the time taken to make the standard, which in this 
case was two to three seconds in bright sunlight at noon. In these 
experiments four seconds were necessary to produce the standard 
shade directly under the glass in sunlight, fifteen seconds under the 
whitewashed glass, and forty seconds in the shade. If the light 
value of the standard is represented by 1, the proportional light 
values under the three conditions given would be as follows: 
meng Shade Whitewashed glass 
13-33 5.00 
This ettod of obtaining light values is described by CLEMENTS 
(2, pp. 49-64). In order to test the power of new shoots from fresh 
potatoes to form intumescences, a new set of thirty-six potatoes was 
pene June 5; and June 25 the shoots were covered by the bell jars. 
EXPERIMENT XVIII 
In sunlight with an average temperature of 79° F. 
Pot 48. Three shoots (from a whole potato), 240, 150, 150™™ high, with large 
leaves, 
Pot 49. Four shoots (from a cut potato), 320, 340, 300, 280™™ high, with 
large leaves. 
Pot 50. Three shoots (from a whole potato), with large leaves, 280, 230, 
230™™ high. 
Pot 51. Two shoots (from a whole potato), 200 and 240™™ high, with large 
leaves. 
Pot 52. Four shoots (from a whole potato), 200, 240, 200, 220™™ high, with 
large leaves. 
After two days intumescences had begun to form, and in three days they had 
formed on all the plants excepting no. 52. Although this was left covered for a 
few days longer, intumescences did not form. 
EXPERIMENT XIX 
Five plants were placed in the shade, with an average temperature 
of 73°F 
Pot 53. Four shoots (from a cut potato), 240, 280, 210, 260™™ high, with 
large leaves. 
Pot 54. Three shoots (from a whole potato), 260, 230, 270™™ high, with large 
leaves. 
Pot 55. Three shoots (from a whole potato), 120, 130, 150™™ high, with large 
leaves. 
