62 THE POPULAR SCIENCE MONTHLY. 



respiration. But, notwithstanding the discovery of a number of facts 

 which tended to enlarge the province of this so-called nocturnal respi- 

 ration, it was far from attaining the importance of the diurnal, which 

 all the botanists held to be the true respiration of plants, and which, 

 as compared with the other mode, clearly deserved this distinction, 

 owing to the number, the duration, and the extension of the phenomena 

 which it represented. 



One might wonder at this strange duality of respirations in a sin- 

 gle being respirations that were antagonistic in their very essence ; 

 especially might one ask how plants could be deprived, during one- 

 half of their life, of that physiological function, the unceasing perform- 

 ance of which would seem to be the most indispensable of all, to wit, 

 the respiratory function for this was held to be identical with the 

 diurnal respiration ; it might even be observed that certain plants, 

 grown in the dark, perform this function very seldom ; but, for all 

 that, the facts all seemed to require the acceptance of the current 

 theory. 



These preliminary remarks will enable the reader fully to see the 

 importance of the researches recently explained to the Lille Society 

 of Sciences, by M. Corenwinder, of whose paper we propose to give a 

 summary. The author, who has for twenty years pursued in one di- 

 rection his studies of vegetal physiology, has proved that the noctur- 

 nal respiration of plants, though supposed to be exceptional, is in fact 

 perfectly continuous, and constitutes their only true respiration. What 

 hitherto has been called diurnal respiration, viz., the absorption of 

 carbonic acid, the seat of which is the chlorophyll, instead of being 

 the true respiratory phenomenon, is a phenomenon of assimilation and 

 digestion, as pointed out by Claude Bernard. Plants and animals 

 respire both in the same way. This is the grand fact, the proofs of 

 which are given by Corenwinder. 



II. 



Buds, young shoots, and nascent leaves, discharge a function hith- 

 erto insufficiently considered, but yet this function is of such a nature 

 as to elucidate the most important laws of vegetal physiology. It 

 may be readily shown by very simple experiments that, in this first 

 period, and for a certain length of time, plants absorb oxygen unmis- 

 takably and uninterruptedly, exhaling carbonic acid. Nor is it only 

 in the dark that they discharge this function ; indeed, it is not very 

 apparent during the night, when the weather is cold, as is often the 

 case in spring. It is during the day, and when the sunlight is strong- 

 est, that this function becomes characteristic, and especially when the 

 temperature is rising. 



This is easily shown by placing delicate plants, gathered in the 

 early stages of their growth, under a close bell-glass, connected with a 

 receiver holding concentrated baryta-water, the receiver in turn being 



