214 



their heat quickly disappeared, but again returned, 

 in 25 or 30 minutes, on their being withdrawn. 

 When they were covered with oil or honey, the pro- 

 duction of heat in the spadkes was suspended for 

 about an hour; and a spadix covered with starch 

 gave no indication of increased temperature till its 

 covering dned and fell off in small portions. Other 

 species of the same genus were found to possess si- 

 milar properties of producing heat ; and it is con- 

 cluded, that this property is confined to the outer 

 surface of the spadix, that it is independent of light, 

 but that the contact of air is necessary to its produc- 

 tion. It was moreover proved, that the air in which 

 th se fiowers had grown, had suffered considerable 

 changes : for it extinguished a lighted taper, and a 

 chick was suffocated in a closed jar in which several 

 fpadices had remained five hours, but recovered on 

 b ing withdrawn *. Th< se facts, in connection with 

 those before related, sufficiently prove that vegetables 

 possess, during their growth, a temperature above 

 that of the ambient air, and that the contact of this 

 air is essential to its production ; and, since it has 

 been shewn, that the oxygen gas of the air is con- 

 verted (38 ) into carbonic acid, by carbon exhaled 

 (141.) by the living plant, whereby the greater part 

 of the specific caloric (166.) of that gas is disenga- 

 ged, it is to this change of composition in the air, and 

 consequent extrication of its heat, that the increased 

 temperature observed in plants, during their vegetar 

 tion, is to be ascribed. 



* Voyage dans les Isles dt-s mers d'Afiique, par M. Bory de St 

 Vincent. 



