76 LECTURE V. 



with free oxygen ; such as the Fungi which produce alcoholic 

 fermentation (e.g. Yeast) and putrefaction (e.g. Bacteria); but 

 these Fungi readily absorb free oxygen when they can ob- 

 tain it. 



We will now illustrate the absorption of oxygen by dif- 

 ferent plants and parts of plants, by reference to experiments. 



The most marked case of the absorption of oxygen by 

 plants is afforded by Fungi. Pasteur and others have found 

 that Fungi can absorb the whole of the oxygen present in a 

 closed space. 



Marcet obtained the following results with Boletus versicolor: four 

 specimens weighing 9 grammes remained for 12 hours in a receiver con- 

 taining 1 20 c.c. of air. 



Composition of the air, before the experiment, after the experiment : 



Nitrogen 94*8 c.c. 947 c.c. 



Oxygen 25-2 o'6 



Carbon dioxide ... 287 



120'oc.c. 1 24*0 c.c. 



It appears that the property of absorbing the whole of the 

 oxygen present is possessed by all plants. For instance, 

 Wolkoff and Mayer found this to be the case in their ex- 

 periments on seedlings (Polygonum Fagopyrum, Tropceolum 

 majus). 



Various observers (de Saussure, Oudemans and Rauwen- 

 hoff, Fleury) have found that germinating seeds absorb 

 considerable quantities of oxygen, and exhale carbon di- 

 oxide. 



De Saussure determined that one gramme of seed absorbed oxygen 

 and exhaled carbon dioxide as follows : 



Hemp, 43 hours at 22 C. 



absorbed 1970 c.c. of oxygen, 

 exhaled 13*26 c.c. of carbon dioxide. 



Colza, 42 hours at 2i'5C. 



absorbed 31*40 c.c. of oxygen, 

 073 c.c. of nitrogen, 

 exhaled 24-39 c - c - of carbon dioxide. 



