122 



M. L. Gurreau on the Functions of 



of plants has its seat in the living nitrogenous matter which is 

 seen in circulation within the cells is the relation which exists 

 between the quantity of this matter contained in a living organ 

 and that of the carbonic-acid gas exhaled. 



The subjoined Table^ taken from our first memoir on the 

 respiration of plants (' Annales des Sciences Naturelles/ 1851, 

 p. 5) appears to bear out this assertion : — 



Matters examined. 



Observations. 



White pith of Elder 



Wood of oak, in fine chips 



Carrot 



Fresh alburnum of Elder 



Do. do. of Horse-chestnut... 



Root-fibres of Groundsel 



do. of Mercurialis 



Boletus aureus 



Yeast, of the consistence of paste 

 Yeast, washed with distilled water 



The yeast was 

 spread on unsized 

 paper, and suspend- 

 ed in the air of the 

 apparatus. 



According to these experiments (in which the volume of the 

 organ respiring is taken, for comparison sake, as the unit), 

 those portions of plants deprived of living azotized matter carry 

 on no respiratory act, whilst those which, like very slender 

 fibrils, alburnum, fungi, yeast, &c., are richly furnished with it, 

 fulfil that function the more actively in direct proportion with 

 the quantity secreted or deposited. It is worth remarking that 

 seeds and fruits, although rich in proteine matters, produce only 

 a minimum quantity of carbonic acid ; but this at the same 

 time is explicable on account of those substances being coated 

 by dense envelopes, rendering them scarcely permeable by the 

 oxygen, and of their relative volume as compared with their very 

 small surface. These obstacles to their respiratory activity are, 

 however, indispensable to their normal development ; for other- 

 wise neither starch, nor oil (so necessary to the germination of the 

 young embryo), nor pectine, nor sugar, nor the ligneous deposits 

 of fruits could be produced, if the carbon, the essential element 

 in their formation, were consumed. A proof that this assertion 

 is true is furnished by the analyses of M. Boussingault, which 

 prove that fruits and seeds so placed as to facilitate the action of 

 oxygen, and thereby to stimulate and promote the vital move- 

 ments of the nitrogenous matter, carry on a respiratory function 

 and are deprived of a great part of their carbon without any loss 

 of their nitrogen. 



The proteine material of plants exerts on the respiratory 

 pabulum laid up a similar action to that which animal substance 

 exercises on the same matter, and in such a manner that the 



