814 Irving.—Photosynthesis and 
when the shoots were some 4 inches high the tops which bore the unde¬ 
veloped leaves folded together were cut off about 1 \ inches long. About 
twenty of these, weighing about 14 grams, were used for each ex¬ 
periment. 
In this experiment the shoots were of a deep orange colour at the 
beginning, and a series of thirty two-hour estimations of the respiration was 
started, in the course of which there were three periods of illumination as 
shown in Table II. The temperature varied between 22*6° C. and 23° C. 
On inspection of Fig. 6 it will be seen that readings 5 and 6 in the 
light are lower than any of the four readings that precede them, but this is 
clearly not evidence of photosynthesis but only the result of the general fall 
of the respiration that accompanies starvation. In the second light period 
the readings are on the contrary higher than those just preceding them. 
While in the third light period the average output of C 0 2 is about the 
same as in the dark. Therefore these are merely chance variations. 
Experiment V. 
This was an experiment with similar material, i. e. etiolated shoots of 
Vicia Faba> but it was carried out at a much lower temperature, i2°-i2-6° C. 
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Time in Hours 
Fig. 7. 
The general decline in the respiration (see Table III) is therefore very much 
less, and, as shown in Fig. 7, the average C 0 2 production in the light is the 
same as that in the dark throughout the experiment. 
Experiment VI. 
The early part of this experiment proceeded just as in the previous 
ones, and there was no sign of photosynthesis up to the twenty-fourth hour, 
by which time the shoots had become grass green (Table IV). Then the 
chamber was taken out of the bath, and with the shoots still in it, was 
placed in an upright position close to a north window. Here it was left 
