396 Trite.— On the Influence of Sudden Changes of 
a radicle from one of these temperatures to the other, the 
growth-rate at both being assumed to be the same, any change 
regularly accompanying such transfer would be regarded as 
referable to this change for its cause. It would be expected 
a priori that such growth-changes would be slight and possibly 
less conspicuous than those due to internal stimuli. It is well 
known that normal growth from time to time makes very 
considerable changes of rate. Hence, as in this experiment, 
where the factors are so nearly balanced, the one evidence 
that a given change in the rate of growth is due to the 
TABLE XXII. 
Period. 
Growth per \ hr. 
Temperature. 
IO.30-II.30 
i*o units 
17-9-18. 2°C. 
II.30-II.45 
i-o „ 
l8*2°C. 
II.45-12 
o -5 ,, 
l8-0 „ 
I 2 -I 2 .I 5 
2-5 „ 
30-0 „ 
I 2. T 5-1 2. 30 
1-0 
30-2 „ 
I2.3O-2.3O 
2*7 «■ 
29 - 9 - 30 -I », 
2.3O-2.45 
2.5 » 
30.0 „ 
2 . 45-3 
i -5 
18.2 „ 
3 - 3-15 
2-5 
18-2 „ 
3 . 15 - 3.45 
i-8 „ 
i 8-3 „ 
i unit = 0*0429 mm. 
temperature- change, is the constancy with which the variation 
of temperature is accompanied by the change of growth-rate. 
This, however, may not always apply, especially when internal, 
spontaneous stimuli act in opposition. The growth-rate then 
seen would indicate the resultant. 
Under the conditions above described, a root of Vicia Faba 
about 30-0 mm. long made the record shown in Table XXI. 
Table XXII gives the record of a similar experiment with 
a root of Vicia Faba . 
Inspection of Tables XXI and XXII shows that every change 
from 30° to 1 8° is followed by a reduction of the growth-rate 
