70 HEAT OF THE ARUM. 



to heat which prove their vitahty, and that a forced 

 Peach-tree will in the following season expand its buds 

 prematurely in the open air, so as to expose them to 

 inevitable destruction. See/?. 50. A thousand parallel 

 instances may be observed, by the sagacious gardener, 

 of plants retaining the habits of their native climates, 

 which very often proves one of the greatest impedi- 

 ments to their successful cultivation. 



The most remarkable account that has fallen in my 

 way concerning the production of heat in plants, is 

 that given by Lamarck in his Flore Francoise, v, 3. 

 538, of the Common Arum macidatu??!, Engl. Bot. 

 t. 1298, (the w^hite-veined variety,) the flower of 

 which, at a certain period of its growth, he asserts to 

 be, for a few hours, " so hot as to seem burning." 

 The learned M. Senebier of Geneva, examining into 

 this fact, discovered that the heat began when the 

 sheath was about to open, and the cylindrical body 

 within just peeping forth ; and that it was perceptible 

 from about three or four o'clock in the afternoon till 

 eleven or twelve at night. Its greatest degree was 

 seven of Reaumur's scale above the heat of the air, 

 which at the time of his observation was about four- 

 teen or fifteen of that thermometer. Such is the ac- 

 count with which I have been favoured by Dr. Bos- 

 tock of Liverpool, from a letter of M. Senebier*, dated 

 Nov. 28, 1796, to M. De la Rive. I have not hither- 



* It is now published in his Physiologic Vegdale, v. 3. 314, where 

 nevertheless this ingenious philosopher has declared his opinion to be 



