90 The Living Plant 



same power, which depends on the energy released by the oxida- 

 tion of carbonaceous food. And it may interest the reader hav- 

 ing a turn for figures to know that the energy released by the 

 respiration of sugar is just about half of that released by the com- 

 bustion of an equal weight of the best coal. 



These matters though clear on reflection, are hard to grasp in a 

 first presentation; and I suggest that we rest a little by consider- 

 ing an incidental matter of interest. In the foregoing paragraph 

 I impUed that the energy of respiration is not released as heat, 

 and thus differs from combustion. But the implication is not 

 strictly correct, as is easily proven. If one takes two handfuls 

 of seeds, soaks them, and starts them growing and therefore 

 respiring, kills one set by hot water, places them both in good 

 non-conducting chambers provided with thermometers, and leaves 

 them some hours, he will notice a remarkable result. The ther- 

 mometer in the living and respiring seeds will soon read several 

 degrees above that in the others, which are obviously similar in 

 all ways except that they cannot respire. And further experi- 

 ment shows that this release of heat by these respiring seeds is rep- 

 resentative of all respiring parts, and that the release of heat is a 

 constant accompaniment of respiration. Although usually small 

 in amount this heat sometimes becomes readily recognizable. 

 Thus the rapidly-opening flowers of Aroids (our Jack-in-the-Pulpit 

 and its relatives) often show by the thermometer a temperature 

 several degrees above that of the air; some alpine flowers can melt 

 their way up, by aid of this heat, through the snow; grain germi- 

 nating or fermenting in large masses becomes often noticeably 

 warm; the warmth of hot beds derived from fermenting manures 

 has the same origin, though here the respiration is that of bac- 

 teria or molds; and various cases of spontaneous combustion, 

 where correctly reported, must have the same origin. It does not 

 appear that this heat, in plants at least, secures any physiologi- 

 cal advantage but is rather an incidental result of the physical 

 forces at work, very much as incandescent electric lamps made 



