100 BIOLOGY. [BOOK n. 



is proportional to the growth. It is, for example, very consider- 

 able in germination. Thus seeds and buds absorb, in evolution, 

 many times their weight of oxygen. It is the same with flowers. 

 Mowers, like all the parts not green of plants, manifestly absorb 

 oxygen ; but they absorb it in great quantity, and, a curious 

 thing, in the monoical plants, the male flowers absorb more 

 oxygen than the female flowers. A fact deserving of remark is, 

 that in all the organic vegetal combinations, oxygen is always 

 in smaller proportion than would be needful for the complete 

 combustion of their carbon and of their hydrogen, for their 

 total transformation into water and into carbonic acid ; and the 

 fact is wholly in accordance with the theory of respiration. 



It is known well, that one of the constant effects of oxydation 

 is a certain production of heat, and that the oxydation of the 

 tissues is the principal source of animal heat. Though less 

 active, vegetal oxydation produces likewise perceptible calorific 

 effects, especially in germination and florescence. Barley grains 

 heaped up for the preparation of malt heat much. In the 

 spadix of the aroidese, at the time of fecundation, the excess of 

 temperature above the exterior medium may amount to 10 or 12 

 degrees. The same fact is observed, but in a less degree, in the 

 isolated flowers of the Cucurbita, Bignonia radicans, Victoria 

 regia, and so on. 1 



However, the respiratory oxydation, and the nutritive or 

 assimilative movement which results therefrom, are not effected 

 except within certain limits of temperature. The minimum is 

 variable as the species varies. According to M. Boussingault 2 

 the leaves of the larch decompose carbonic acid at 0, 5 to 

 2, 5 j those of the grass of the meadows between 1, 5 and 3, 5. 

 According to MM. Cloetz and Gratiolet, the carbonic assimilation 

 commences above 6 degrees in the Vallisneria, between 10 and 

 15 degrees in the Potamogeton. 



This absorption of oxygen is by no means comparable with 



1 J. Sachs, Traite de Botanique, p. 847. 



* Boussingault, Comptes Rendus de VAcad. des Sciences, LXVIII. 



