5 1 8 Townsend . — The Correlation of Growth 
same table shows a constant retardation, although the retarda- 
tion during the first period of twenty-four hours was no 
more marked than in Series I and II, in which the degree 
of injury was much less. 
Table III shows the same general results with Helianthus 
as those shown in Table II with Hordeam and Metis. The 
Table V. 
Growth of leaf after leaf-tip was injured. 
Series I ( a ' — IO mm> reinove d from leaf-tip. 
Avena. | Control. ” 
Series II ( a ‘ — 5 mm - removed from leaf-tip. 
Zea Mats, j ('Zcontrol. ” 
Temperature, 2 2° (constant). 
Series. 
Average 
original 
length of 
leaf of 
ten 
seedlings. 
Average 
normal 
rate of 
growth of 
leaf. 
Average 
growth 
of leaf, 
1st period 
after 
injury. 
Average 
growth 
of leaf, 
2nd period 
after 
injury. 
Average 
growth of 
leaf, 
3rd period 
after 
injury. 
Average 
total 
growth 
of leaf 
after 
injury. 
P. 
24 hrs. 
24 hrs. 
48 hrs. 
72 hrs. 
144 hrs. 
I. 
a. 
36 mm. 
12 mm. 
12 mm. 
61 mm. 
54 mm. 
127 mm. 
b. 
35 „ 
13 „ 
13 ? » 
61 „ 
63 „ 
137 » 
c. 
36 „ 
13 » 
13 0 
58 „ 
33 ,» 
104 ,, 
P. 
24 hrs. 
24 hrs. 
48 hrs. 
3 68 hrs. 
240 hrs. 
II. 
a. 
18 mm. 
10 mm. 
11 mm. 
25 mm. 
93 mm. 
129 mm. 
b. 
2° „ 
9 » 
11 „ 
33 » 
135 » 
J 79 » 
c. 
19 » 
10 » 
11 
29 „ 
7i » 
111 » 
periods of variation in the rate of growth, however, were 
longer in the experiments with Helianthus . 
According to Table IV even one millimeter cut from root- 
tips produced an acceleration in the growth of the shoots, 
although the growth of the root was of course retarded. 
During the first twenty-four hours after cutting no change 
