8l2 
Irving.—Photosynthesis and 
The respiration fluctuates considerably, but obviously there is no 
marked lowering of the output of C 0 2 during the light periods. Fig. 5 
enables us to compare respiration in the dark and light more precisely, and 
the dark periods are indicated by the black bands along the bottom of the 
graphic. 
The dotted line indicates what would be the ideal form of the curve of 
respiration in continuous darkness, and it is clear that the fluctuations below 
this do not preponderate in the light periods any more than those above 
preponderate in the dark. 
As their distribution was entirely random there is not the slightest 
evidence of photosynthetic activity in the light, although at the third period 
of illumination the leaves were grass green. 
Experiment IV. 
The rest of the experiments were made with a very different material, 
etiolated shoots of Vicia Faba. The seeds were germinated in the dark, and 
TABLE II. 
Etiolated Shoot-tips of Vicia Faba. 
No. of 
Reading. 
Grams of CO a 
given out. 
Illumination. 
Colour of Leaves. 
1 
•0025 
Dark 
Orange yellow 
2 
•0040 
>> 
3 
•0033 
>> 
4 
•0029 
a 
5 
•0024 
Light 
6 
•0024 
yy 
Traces of green 
7 
•0022 
Dark 
8 
•0021 
» 
9 
.0019 
a 
10 
.0018 
a 
11 
•0017 
yy 
12 
•0015 
» 
13 
.0015 
yy 
14 
.0014 
yy 
15 
.0015 
»> 
16 
.0019 
Light 
Very pale green 
17 
.0019 
yy 
18 
.0018 
yy 
J 9 
• 0021 
Dark 
20 
•0020 
yy 
21 
•OOlS 
yy 
22 
.0017 
n 
23 
•OOl6 
a 
24 
• OOl8 
y 9 
25 
•OOI9 
Light 
26 
•0020 
>> 
27 
.OOI5 
a 
28 
.OOI5 
f> 
Grass green 
29 
.OOI9 
yy 
30 
.OOI9 
it 
