THE VEGETABLE (JELL. 103 



o'clock ia the evening ; in Golocasia odora, Brongniart found the 

 maximum at 5 A.M ; Vrolik and Vriese, as well as Van Beek 

 and Borgsnia, about S P.M. ; and Hasskoii, in Java, at 6 A.M. 

 (" Tldschr. V. naturl. Gesch." vii letterkund Berir/t 26) ; as also 

 Hubert found, probably in the same plant, the greatest heat after 

 sunrise, in Madagascar. 



In very few cases has evolution of heat been observed in the 

 blossoms of other families. Saussure, by means of an air-thermo- 

 meter, found tlie flowers of Gourds V to 3°, those of Bignonia 

 radioans V, of Polijanthes tuberosa J-°, and Mulder those of 

 Cactus grandifioTiis i° — 2° Fahr. warmer than the atmosphere. 



There can be no doubt that the evolution of heat frorti flowers 

 results from the respiratory process connected with the formation 

 of a large quantity of carbonic acid. Saussm^e found that a 

 blossom of Arum ^inacidatuon consumed in. twenty-four hours, 

 before its heating, or after it had ceased, five times its own 

 volume of oxygen, while a warmer blossom consumed thirty 

 times, its spathe five times, the bare portion of its spadix thirty 

 times, and the part covered with flowers 132 times its volume of 

 oxygen. Yrolik and Vriese (" Ann, d. Se, Nat sec. aer" xi. 62) 

 found the heat of a blossom of Golocasia odora increase about 

 9° to lO"", when brought into oxygen gas, while no evolution of 

 heat took place at all in carbonic acid. 



In like manner, there can be no doubt that in germinating 

 seed, the respiration of which is equally connected with the con- 

 sumption of oxygen and the exhalation of carbonic acid, the evo- 

 lution of heat stands in connection with the formation of carbonic 

 acid ; but whether this source furnishes all the liberated heat, or 

 a part of it depends upon the vegetative process of the germina- 

 ting seed, cannot be determined in the present imperfect state of 

 our knowledge of the chemical transformations of the substance of 

 the seed connected with germination. 



In vegetating organs the source of heat is evidently different. 

 It is true, as we have seen, that oxygen is consumed and carbonic 

 acid formed by all organs, but since on the whole a greater quan- 

 tity of carbonic acid is decomposed in the green- coloured organs, 

 than is formed in the remaining parts, more heat must be consumed 

 than produced in the respirating process of vegetating organs. 

 But evolution of heat must be connected with the nutxient process, 

 for the plant forms its organic substance, if not wholly yet in great 

 part, from gases and liquids. Since then the growth of the plant 

 exhibits a daily exaltation, occurring about noon, it is quite m 

 accordance that the evolution of heat also should occur in in- 

 creased degree at the same time. 



