524 Townsend . — The Correlation of Growth 
of longer duration than two hours usually caused either 
a continuous retardation or death. 
Older Plants. Stems . — Satisfactory results were obtained 
in studying the growth of the stems when the roots were 
injured in plants of Phaseolus multiflorus about two weeks 
old. In the experiments with these older plants a single root 
was allowed to pass through the bottom of the flower-pot in 
the manner already described. This root was then allowed 
to attain a length of from thirty to forty centimeters below 
the bottom of the flower-pot before cutting away, but no 
Table XII. 
Growth of stem after a number of secondary roots were removed. 
Series I. t a . — About two-thirds of the secondary roots removed 2 cm. from base. 
Phaseolus. ( b. — Control. 
Temperature 22 0 (constant). 
Series. | 
Average 
original 
length 
of stem 
of ten 
plants. 
Average 
normal 
rate of 
growth 
of stems. 
Average 
growth 
of stems, 
1 st period 
after 
injury. 
Average 
growth 
of stems, 
2nd period 
after 
injury. 
Average 
growth 
of stems, 
3rd period 
after 
injury. 
Average 
growth 
of stems, 
4th period 
_ after 
injury. 
Average 
growth 
of stems, 
5th period 
after 
injury. 
Average 
total 
growth 
of stems 
after 
injury. 
P. 
24 hrs. 
12 hrs. 
12 hrs. 
24 hrs. 
24 hrs. 
120 hrs. 
192 hrs. 
I. 
a. 
149 mm. 
27 mm* 
17 mm. 
19 mm. 
41 mm. 
33 mm. 
149 mm. 
259 mm. 
b. 
147 „ 
26 „ 
12 » 7 
13 „ 
2 9 » 
3i „ 
I7 2 » 
257 „ 
appreciable variation in the rate of growth of the stem could 
be detected. Subsequent experiments showed that the injury 
in this case was not strong enough to produce any decided 
change in the rate of growth. However, when a large 
number of the secondary roots were cut off at a distance 
of about two centimeters from the main root, as in Table XII, 
a decided acceleration in the growth of the stem took place 
within twelve hours after injury, and continued for about 
forty-eight hours. This was followed by a period of normal 
growth lasting about twenty-four hours, after which came 
a period of retardation lasting about five days, at the end 
of which time the stems were again practically equal in 
