176 PHYSIOGNOMY OP PLANTS. 



phenomenon of the fever-heat, which in certain plants is 

 sensible by the thermometer during the development of their 

 inflorescence, and which is connected with a great and tempo- 

 rary increase of the absorption of oxygen from the atmosphere. 

 Lamarck remarked in 1789 this increase of temperature at the 

 time of flowering in Arum italicum. According to Hubert 

 and Bory de St. Vincent the vital heat of Arum cordifolium 

 in the Isle of France was found to rise to 3 5 and 39 E-eau- 

 nmr, (110.6 and 119.6 Fahr.) while the temperature of 

 the surrounding air was only J5.2 E. (66.2 F.) Even 

 in Europe, Becquerel and Breschet found as much as 1 7 J 

 difference, Eeaumur (39.4 Fahr.) Dutrochet remarked a 

 paroxysm, an alternate decrease and increase of vital heat, 

 which appeared to reach a double maximum in the day. 

 Theodore de Saussure observed analogous augmentations of 

 temperature, though to a less amount, only from 0.5 to 

 0.8 of Reaumur's scale (1.15 to 1.8 Fahr.), in plants be- 

 longing to other families ; for example, in Bignonia radicans 

 and Cucurbita pepo. In the latter plant the use of a very 

 sensitive thermoseope shews that the increase of temperature 

 is greater in the male than in the female plant. Dutrochet, 

 who previous to his early death made such meritorious re- 

 searches in physics and in vegetable physiology, found by 

 means of therm o-magnetic multiplicators (Comptes rendus 

 de Tlnstitut, T. viii. 1839, p. 454, T. ix. p. 614 and 781) 

 an increase of vital heat from 0.l to 0.3 Eeaumur, (0.25 

 to 0.67 Fahr.) in several young plants (Euphorbia lathyris, 

 Lilium candidum, Papaver somniferum), and even among 

 funguses in several species of Agaricus and Lycoperdon. 



