BOTANY. 27 



object of the investigation being to establish the fact of a rise in tem- 

 perature, if any followed wounding of the plant tissues; and in the 

 second place to determine the curve of the change of temperature. The 

 principal apparatus used in this experiment was the thermoelectric; 

 element in connection with a mirror galvanometer. The apparatus and 

 details of the experiment are fully described. 



Numerous precautions were found necessary to avoid error, and care 

 was taken to eliminate as far as possible all sources of error. All the 

 plants were kept in a saturated atmosphere to prevent wilting and also 

 to avoid changes of temperature due to evaporation. 



As a control for the thermo-electric method, experiments were also 

 carried on with a simple form of calorimeter by which the temperature 

 curve of most of the plants could be determined. The results secured 

 with this apparatus were of a confirmatory nature. 



Most of the author's experiments were conducted with potatoes, and 

 it was found that there was no difference in temperature between the 

 cut surfaces and the uninjured potato immediately after injury ; but 

 about two hours after wounding there was an indication of a rise in 

 temperature, which steadily increased until the maximum was reached 

 in the injured plant. 



An important source of error which must be guarded against in such 

 experiments is the use of unhealthy potatoes, it having been found that 

 a very small rotten spot which had no inlluence on the general temper- 

 ature of the tuber would, under the conditions of the experiment, affect 

 the temperature very sensibly. The greatest difference between injured 

 and uninjured potatoes found was 0.-4° C. It was also found that old 

 potatoes showed a greater difference between living and dead tissue 

 than the new ones only recently taken from the ground. This is readily 

 explained by the fact that the old potatoes are just einergirg from 

 their resting period, while the new ones are entering a period of quies- 

 cence, when the metabolic processes are very low. 



It was shown that the influence of the wounding in the case of the 

 potato extends to a very little distance from the point of irritation. 

 The generalization just given applies equally well to the radishes, the 

 kohlrabi, the cucumber, and the carrot, but for onion bulbs the effect 

 of injury was more widely distributed. 



The experiments with leaves, which were made in a bell glass calo 

 rimeter, showed that the maximum increased temperature was reached 

 much more readily than in the experiments with fleshy objects. In four 

 and one half hours after injury the leaves of Liriodendron were 0.75° O. 

 warmer than the uninjured ones. On the next day there was but little 

 difference in temperature, shortly after which time the injured leaves 

 died. 



From these experiments it would appear that plants, like animals, 

 respond to the stimulus of injury by an attempt to rally from it, and 

 the rallying is accompanied by somewhat the same symptoms. The 



