on Vegetables, with reference to their Temperature. 5 



of native soil around their bulbs, shortly after sun-rise, placed 

 in a wooden box and carried at once to the place of destina- 

 tion about 200 yards distant ; after having been left a suffi- 

 cient time to allow the soil to radiate any excess of heat, or 

 about two hours under any circumstances, the measures were 

 commenced, and recorded at the time. Other examinations 

 of the same group of plants took place however at different 

 periods in the day, the plants being uninjured and vigorous. 



It is necessary I should observe here, that all attempts made 

 to examine plants in situ failed from various causes ; the dif- 

 ference of temperature between parts exposed to the sun and 

 those in the shade ; the impossibility of managing the delicate 

 thermoscope in the open air ; the disturbing effects of cur- 

 rents, gusts of wind, &c. ; nor does it appear to me at all 

 necessary that such examinations should be made, even if the 

 results could be depended upon. The measures derived from 

 a vigorous plant removed under the foregoing circumstances 

 are fully as trustworthy; and when the great deviations of the 

 needles come to be considered, even the most sceptical will 

 allow that the difference of situation would not have influenced 

 the result beyond a few degrees ; in which I may possibly be 

 in error ; but upon the general fact there cannot be any dis- 

 pute. 



So far the tables introduced may be regarded as exhibiting 

 the measures made upon one species ; but although it has not 

 been considered necessary to tabulate the other results, yet a 

 similar series of experiments were made on the undermen- 

 tioned plants, as far as it was found practicable, but none of- 

 fered the advantages possessed by Arum. 



The examination of these plants gave the same general result, 

 and they may therefore be dismissed, after simply stating that 

 they corroborate in all respects the observations hereafter to 

 be made on the subject of vegetable temperature, &c. 



Symphytum officinale, Pastinaca sativa, Cicuta maculata, 

 Asclepias obtusifolia et syriaca, Arctium Lappa, Sagittaria sa- 

 gittifolia, Rumex crispus, Lobelia cardinalis, Daucus Carota, 

 Datura Stramonium, Delphinium consolidum, Cynoglossum offi- 

 cinale, &c. 



The botanist will recognise in this list, plants of sufficient 

 bulk to allow of the introduction of the thermo-electric pair. 

 They are also very frequently met, and were chosen partly 

 from this cause, as well as from their proximity to the labora- 

 tory. The list could be elongated indefinitely if a smaller pair 

 were used, but it is unnecessary to introduce other cases, as 

 each observer can modify his apparatus as to the fineness of 

 the elements according to his pleasure. 



