51 
EUPHORBIA V [ROSA AND ALOE DIOHOTOMA 
the fact that the internal temperature of an unwounded branch of the same 
plant almost invariably falls or ceases to rise in apparent sympathy with the 
fall in the neighbourhood of the wound. 
This was observed in the experiment under notice in the unwounded 
branches carrying the thermometers T and P. Thermometer P shews a 
distinct fall and recovery and T remains stationary ; the periods of these 
effects correspond vei’y closely with that of the fall and recovery at the wound. 
^Did fui ther, the fall m P and the retardation of the rise m 7 1 both commence 
5 minutes after the observed beginning of the fall in W. These effects cannot 
CHART III. December 13. 
Euphorbia A (Thermometers IF, T, P). 
possibly be connected with surface-evaporation at IF If they have a purely 
physical explanation the most natural would seem to be the expansion of the 
pith gases. This expansion would be practically instantaneous at the wound. 
It would, however, be delayed in the more distant parts of the plant owing to 
the more tardy withdrawal of latex and probably also to the resistance of the 
cellular diaphragms which cut up the pith into cavities. These conclusions 
are confirmed by other experiments. 
No. 2. December 13. 
Chart I. 
Plant. Euphorbia A. 
Thermometers. IF, T, P inserted as in No. 1. 
The wound inflicted on the branch IF at 9.10 was on the leeward side. 
At 11.5 the stem P was wounded in the same manner but in the windward 
