2 Professor Gardner on the Influence of the Dew-point 



tion of the soil and surrounding air : to this we add, chemical 

 action increases with atmospheric temperature, &c. &c, and 

 consequently the amount of heat resulting therefrom. 



4thly. A review of the foregoing doctrine, with some re- 

 marks on apparent anomalies. 



§ I . That certain Vegetables are without any specific heat. 



A number of insulated measures of the temperature of 

 flowers has hitherto been admitted into the books on vege- 

 table physiology as the whole of our information on the sub- 

 ject of vegetable heat; and these measures have been re- 

 ceived with distrust or altogether denied. M. de Lamarck 

 observed an increase of temperature in the spadix of Arum 

 vulgare, which M. Sennebier afterwards measured and found 

 equal to 7° C. above the atmosphere. The German natu- 

 ralist Schultz found a flower of Calladium pinnatifidum at 19° 

 to 20° C. when the surrounding air was only 15° C. Messrs. 

 Hubert and Bory measured the temperature of the spadix of 

 Arum cordifolium in the Isle of France, and found it at sun- 

 rise 4"Jf° to 49° C. ; the atmospheric temperature being only 

 19° C. M. de Saussure carried his experiments further, and 

 with the differential thermometer ascertained an increase of~°C. 

 in the male flowers of the melon and other Cucurbitaceae. 



Hypotheses have not been wanting to explain the reason 

 why flowers should enjoy a more elevated temperature than 

 the other parts of the plant. Mr. Murray imagined it was 

 due to their colour. Brongniart ascribed it to the increased 

 action of the molecules interested in the process of fecunda- 

 tion. Others have adopted the more plausible idea, that it de- 

 pended upon increased chemical action, as the absorption of 

 oxygen by the petals, &c. of the flower. 



But Messrs. Treviramis, Goppert and Schubler, altogether 

 deny that flowers give any indications of an increase of tem- 

 perature. M. Aug. de Candolle ascribes this denial to the 

 erroneous conclusions at which these botanists arrived from 

 experimenting on imperfect plants ; since his experience at 

 Montpellier had led him to the same opinion as Saussure 

 and others. 



Placed in so embarrassing a situation, our only resource 

 was to undertake a new series of experiments upon the sub- 

 ject ; for although the mass of evidence appears to be in fa- 

 vour of the existence of a specific temperature in flowers, yet 

 the measures given are too dissimilar to prove satisfactory, 

 and the experiments appear to have been performed in too 

 loose a manner to silence opposition. The mere introduction 

 of a thermometer into a flower is a process undeserving any 



