224 RECENT EESEARCHES ON THE KESriRATlON OF PLANTS. 



What is more to the point still, is that the zoospores, actually 

 living and moving, but deprived of the cellular envelope, soon 

 become stationary, and cover themselves with a cell which they 

 secrete ; and though to all appearance dead under the veil wliich 

 hides them from our view, their vitality is still retained, for they 

 form a plant which again calls tliem into life. This curious fact 

 deserves a most careful examination by physiologists, as it might 

 lead to other circumstances throwing great light on the true 

 nature of plants. 



There is in truth an immense difference between algals and the 

 large majority of other plants ; but we must look for their 

 resemblances not to form or functions of secondary importance, 

 but to the movements and principal functions of their azotized 

 substances. 



Conclusions. 



From the facts which have been now mentioned, we may 

 conclude : — 



1. That buds when respiring consume more carbon than the 

 leaves, and less than plants themselves. That the quantity of 

 acid expired is great in proportion as the quantity of living proteine 

 matters contained in these organs is great, their weights and 

 surfaces being equal. 



2. That in the day time, both in the sun and in the shade, 

 leaves exhale carbonic acid, the quantity of which is great in 

 proportion as the temperature is high. 



3. That the acid found in the apparatus does not represent by 

 a great deal all the carbonic acid given off, the larger part of it 

 being reduced after being exhaled. 



4. That two simultaneous and opposite actions go on in the 

 leaves, both in the sun and in the shade ; one by which carbonic 

 acid is formed, the other by which it is decomposed, and that 

 the accumulation of carbon in plants is due to the excess of the 

 effects of the latter over those of tiie former. 



5. That these two acts being simultaneous, the former ought 

 to be considered as the respiration of plants, and the latter as 

 more especially connected with their nutritive functions. 



