58 
INTERNAL TEMPERATURES OF 
established between the absorption of heat from without and the loss of heat 
by surface-evaporation. 
The difference between the temperatures of W and T at their maxima on 
December 18, i.e. before T was wounded, was 
December 20, they differed at their maxima by 9 C 
in this case being apparently entirely due to the 
On the following morning (December 21) at 
while W read 25 0- 5. T continued to fall until 9 
time reading 27°’2. After 9 o’clock both rose s 
2.45 P.M. when the last readings were taken, T st 
The effects of the wounding of T were then 
and for a long period and the recovery was very f 
fact that many years before, Aloe B had evidei 
wound near the base of the trunk (see Photogr; 
doubted whether complete recovery was possibl 
partial callus had formed, and to all appearance t 
it had never been wounded. 
A brief visit was paid to the locality on Ja 
exposed by the wound made on December 20 \\ 
The leaves were shrivelled and most of them han 
looked as if it was unlikely to survive. Rain had 
there was no reason to suppose that its appeara: 
prolonged drought. 
5. Discussion. 
In the Aloe, as in the Euphorbia, the infli 
followed by a lowering of the internal temperati 
fall commences after a considerable interval, it 
some hours when the wound is large. It is wit! 
evaporation at the surface and conduction throug 
the xylem. 
In the Euphorbia the effects of surface-wou 
They are complicated by the presence of large 
by the copious outflow of latex and by the rapi 
rubber over the surface of the wound. Here t 
perature is due only partially to surface-eva] 
enhanced by another cause which acts more quic 
distance than surface-evaporation. This cause is 
of the gases imprisoned in the pith. 
The exudation of latex 1 implies an internal 
1 This occurs even at the time of minimum air an 
