28 Meyen's Report for 1839 on Physiological Botany, 



half an hour exhibited a temperature 4° higher than the one 

 in the air. Oxygen was passed into the apparatus from time 

 to time ; it was confined by means of water, which also ab- 

 sorbed the greater part of the carbonic acid produced by the 

 inflammation (verbrennung) of the spadix. In nitrogen no 

 rise of temperature was observed, and it could not be seen 

 that any gas was absorbed ; all vital activity, and even the co- 

 lour, were lost. 



M. de Vriese* has also communicated some observations 

 made by a M. C. Hasskarl, in Java, on the spadices of Colo- 

 casia odora ; he found 22° Fahr. as the greatest difference be- 

 tween the temperature of the spadix and that of the external 

 air, and this in the morning at eight o'clock ; the next morn- 

 ing there was only a difference of 10° Fahr. 



M. Dutrochetf observed the evolution of heat in the spadix 

 of Arum maculatum by means of a thermo-electric instrument, 

 which MM. van Beck and Bergsma (vide former Report, p. 

 83) also employed ; he found the highest temperature ex- 

 actly at the time when the spatha opens, and this exceeded 

 the temperature of the air by from 11° to 12° C. In another 

 note % of the 1 1th of May, M. Dutrochet mentions, that during 

 the night the temperature of every part of the spadix of Arum 

 maculatum decreases, and increases again by day ; it reaches 

 its maximum early in the day, then diminishes, and disappears 

 altogether in the night. 



In the sitting of the Parisian Academy § of the 10th of June, 

 M. Dutrochet's researches on the temperature of plants (which 

 had been delivered in on the 1st of July, 1838) were read. He 

 says — plants possess a peculiar warmth; but this is com- 

 pletely absorbed by the evaporation of the sap, by the evolu- 

 tion of oxygen by day and of carbonic acid by night. It 

 rather seems that, in the natural state, plants possess the pro- 

 perty of producing cold, for they almost always have a lower 

 temperature than that of the surrounding air. If however the 

 evaporation is prevented, it becomes easy to observe the pro- 

 per temperature of plants ; for this purpose M. Dutrochet 

 used a thermo-electrical apparatus. For the sake of compa- 

 rison the experiments were made both with living and dead 

 plants ; the latter acquired the temperature of the surrounding 

 medium, the former the same, with the addition of that which 

 was hindered or destroyed by the evaporation ; the latter M. 

 Dutrochet reckons in maximo at \° Cels. ; it is often only £°, 



* Tijdschrift, &c, 5. iii. pp. 230—233. 



t Comptes Rendus de 6 Mai 1839, p. 695. J Ibid., p. 74J. 



§ Ibid., 10 Juin 1839, pp. 907—911. 



