376 FREAKS OF PLANT LIFE. 



31°, Fahr., above the temperature of the surrounding, 

 air. In 1 834 M. Brongniart observed the elevation of 

 temperature in Colocasia odora as 19/8° Fahr., above 

 that of the conservatory in which it was growing. 

 Van Beek and Bergsma examined the same species 

 in 1828, and found an elevation of 50°, Fahr., above 

 the surrounding air, by means of a thermo-electric 

 apparatus. 1 



In 1839 Vrolik and Vriese made numerous obser- 

 vations, and found that the maximum of several hun- 

 dreds of experiments was from 48 to 57° Fahr. 2 " 

 These bring us to the memoir of Dutrochet, in which, 

 after recounting the labours of his predecessors, he 

 narrates his own experiences up to 1840, chiefly on 

 the common wild Arum, 3 in which he found an ele- 

 vation of temperature of from 25 to 27 Fahr. From 

 all these experiments, made by different individuals 

 and in diverse ways, we ascertain that there is a great 

 elevation of temperature in the plants of the Arum 

 family at the period of flowering, but the precise 

 amount varies with the observers, the highest being 

 from 50° to 68° Fahr. for the larger species, and pro- 

 portionately less for the smaller ones. 4 The greatest 



1 Brongniart "Nouv. Ann. du Mus.," iii., 145. 



2 "Ann. des Sci. Nat.," 2nd ser., xi., p. 65. 



3 "Ann. des Sci. Nat.," 2nd ser., xiii., pp. 5 and 65 (1840). 



4 For a summary of these observations, see Balfour's " Class. 

 Book of Botany," p. 520. 



