HEAT DUE TO RESPIRATION. 



405 



be accomplished by means of the simple apparatus here figured. The bottle/" con- 

 tains a strong solution of potash or soda /, which absorbs the carbon dioxide liberated 

 in respiration. In the opening of the bottle a funnel r is inserted, in which a large 

 number of germinating seeds or flower-buds are contained. The bell-jar g is for the 

 purpose of preventing the radiation of the heat, without however excluding the access 

 of the atmospheric air, which can enter at the lower margin of the bell-jar, as well as 

 through the pad of cotton-wool w. A thermometer / is pushed through the latter, so 

 that its bulb is immersed among the respiring plants. For observation two such 

 pieces of apparatus should be arranged close together in a chamber, the thermometers 

 being previously compared. In the second apparatus, the funnel r is loosely filled 

 with moist filter-paper instead of with portions of plants, etc., in order to establish 

 similar conditions of evaporation and 

 radiation. In order still more to regu- 

 late the evaporation, a divided glass lid, 

 through the central hole of which the 

 thermometer passes, is laid on the 

 funnel r. The apparatus, as well as 

 the parts of plants experimented with, 

 should have been already exposed to 

 the temperature of the space in which 

 the observation is made for several 

 hours before the commencement of the 

 experiment. 



By these means, with temperatures 

 favourable for vegetation, I succeeded in 

 observing a spontaneous heating of i"5°C. 

 in the case of 100-200 germinating Peas 

 as their roots developed. The anthers 

 of a Gourd caused the mercury of a 

 somewhat large thermometer, the bulb 

 of which touched them on one side 

 only, to rise through o'8° C. A single 

 flower -head of Onopordon acanthium 

 showed a spontaneous heating equal to 

 o"72°C.j and the stamens of a single flower of Nymphaa stellata showed a rise 

 of temperature of o-6° C. Numerous flower-buds of Anthemis chrysoloica, heaped 

 round the bulb of the thermometer, were heated through i-6° C. during the unfolding. 

 In large, vigorously developing Fungi, it sufficed to push a thermometer into their 

 substance to observe the rise of temperature. 



The apparatus for observing respiration figured above (Fig. 252) may also 

 be employed for these experiments, if a thermometer is inserted in the bell-jar c, so 

 that its bulb is immersed among the respiring plants. 



The idea that the spontaneous heating of plants is a consequence of respiration 

 was expressed by Theodore de Saussure so long ago as 1822; although his own 

 thermometric observations on flowers afforded no very satisfactory results, because 

 they were made in the open air. 



Fig. 253. — Apparatus for observing the spontaneous heating 

 of germinating seeds and flowers. 



