M. V^an. Beck on the Temperature of Plants. 331 



fov other mixtures, and they consume a good deal of the petals 

 for the conserve of roses, or Goolcund, as they call it. There 

 are several kinds of essential oils produced from the strong 

 scented flowers in this district, which I will prociu*e and send 

 down to you. 



Observations on the Temperature of Plants. By M. Van 



Beck.* 



I have repeated the interesting experiments of M. Du- 

 trochet, respecting the proper heat of plants, with complete 

 success, by means of M. Gourjon's gah'anometei", and the 

 physiological needles of MM. Becquerel and Breschet. 



I selected for my experiments two plants in pots, viz. Sem- 

 perv^oum sputulatum and Seclum cotyledon, sheltered from the 

 direct action of the solar rays in an apartment of which the 

 ordinary temperature was from 15'".75 to 1G'.75 centigrade, 

 and not subjected to any great or sudden changes. 



The soldered point of one of the physiological needles, 

 covered with several layers of gum-lac, was inserted into a 

 young leaf of the plant, while the point of the other needle 

 M-as' placed in a similar leaf of the same plant, but dead, its 

 vitality having been destroyed by means of water at a high 

 temperature. 



The apparatus being thus disposed, and the needles united 

 by means of conducting wires to the galvanometer, the variable 

 motions of the magnetic needle usually indicating, although in 

 a very irregular manner, the lowest temperature on the side 

 of the living plant, evidently shewed that the phenomenon of 

 the inherent heat was obstructed by the anomalous action of 

 external causes. 



The plant was then placed, with a vessel liUed with water, 

 under a large glass receiver, having its inside moistened. 

 From the time that a psychrometer placed under the bell- 

 glass, by the side of the plant, indicated that the air was sa- 

 turated Avith humidity, the phenomenon of the proper hea 

 manifested itself continually during the whole day. 



* Comptcs llendw. No. I. 6tli Janvier, p. 3C, 



