52 
INTERNAL TEMPERATURES OF 
side. If the fall in temperature in the wounded stem is in part due to 
evaporation, the fall should be more rapid in this than in the former case. 
The area wounded was as nearly as possible the same. 
Between 11 and 11.5 (i.e. before the wounding) P fell 0 o- 25 C. for unex- 
plained reasons. The results of the experiment are shewn on the chart and 
in Table I. The greatly increased fall at the wound (P) is doubtless due to 
the more rapid evaporation in the wind. The effect in each of the branches 
not wounded in this experiment (IF had been wounded in No. 1) is an arrest 
for a period closely corresponding with that of the fall at the wound. 
A second fall commences in P at 11.35 and in T at 11.39; the recovery in 
each case beginning at 11.45. This is certainly an effect of cloud. At 11.33 
the sun was partially obscured by a light cloud and remained so until 11.36. 
It was clouded again momentarily at 11.41, but before 11.45 was again shining 
brightly. The effects of this clouding are not shewn by BB which was not 
read between 11.30 and noon. 
No. 3. December 14. 
Chart IV. 
Plant. Euphorbia A . 
Thermometers. W, T, P all removed from the positions occupied on 
December 13, and replaced in fresh branches of the 
same plant. W, T were placed in the same furrow 
of the same branch ; P in a neighbouring stem. 
Immediately after the 10 o’clock reading, the stem P was wounded in 4 of 
its 5 furrows by a close series of crossed shallow diagonal cuts. In each 
furrow the wounded area was about 2 inches long and extended horizontally 
from ridge to ridge. The middle of each wounded area was level with the 
point of insertion of the thermometer in the fifth furrow which was unwounded. 
The wounding was therefore much more extensive than in either of the 
previous day’s experiments. 
Between 9.30 and 10 the temperature of P rose from 35 0- 5 to 39 0- 25. In 
the same interval both IF and T rose more rapidly than P. At 10.1 the 
temperature of P had not appreciably changed but immediately after the 
wounding it fell very rapidly — from 39°‘25 to 30°'75 in 11 minutes. The 
other two thermometers, both being in the second branch under observation, 
shewed a smaller but nevertheless distinct fall and recovery. 
The fall of temperature here is much greater and much more rapid than 
in the previous experiments. This, together with Experiment 5, leaves no 
doubt that the fall is definitely related to the extent of the wounded surface 
which would determine both the amount of the exuded latex and the expansion 
of the pith gases. 
