DISENGAGEMENT OF HEAT. 211 



degree of development of caloric has been observed. Senebier 

 found that the bulb of a thermometer, applied to the surface 

 of the spadix of Arum maculatum, indicated a temperature 7 

 higher than that of the external air. Hubert remarked this, 

 in a still more striking degree, upon Arum cordifolium, at 

 the Isle of France. A thermometer placed in the centre of 

 five spadixes stood at 111, and in the centre of twelve at 121, 

 although the temperature of the external air was only 66. 

 The greatest degree of heat in these experiments was at sun- 

 rise. The same observer found that the male parts of six 

 spadixes, deprived of their glandular part, raised the tempe- 

 rature only to 105; and the same number of female spadixes 

 only to 86 ; and, finally, that the heat was wholly destroyed 

 by preventing the spadix from coming in contact with the 

 air. 



Similar observations were made by others, with corre- 

 sponding results; but, nevertheless, as many persons at- 

 tempted in vain to witness the phenomenon, it began to be 

 doubted, especially after Treviranus added his authority to 

 that of those who doubted the existence of any disengagement 

 of heat. The truth of the statement of Saussure and others 

 has lately, however, been placed beyond all further doubt, 

 by the experiments of Adolphe Brongniart upon Colocasia 

 odora. (Nouv. Ann. du Museum, vol. iii.) From the period 

 of the expansion of the spathe, he applied to the middle of 

 the spadix a very delicate and small thermometer, which he 

 fixed to its place by a piece of flannel rolled several times 

 round it and the spadix, so that the bulb of the thermometer 

 touched the spadix on one side ; and on all others was pro- 

 tected by the flannel from contact with the air. All this 

 little apparatus covered so small a portion of the spadix, that 

 it was left in its place without interfering with the functions 

 of that part. On the 13th of March, the spathe not being 

 open, the flower diffused, notwithstanding, a fragrant smell. 

 On the 14th it was open, and the odour was much increased. 

 The emission of pollen took place on the 16th, between 8 

 and 10 A.M., and continued till the 18th. On the 19th the 

 flower began to fade. From the 14th to the 19th the 

 temperature increased daily, during the night and in the 



p 2 



