10 MICKOBES, FERMENTS, AND MOULDS. 



This function is not, as it was formerly erroneously 

 supposed, a respiration in the inverse form from that 

 of animals. All plants without exception breathe 

 like animals by absorbing oxygen. The assimilation 

 of carbon is a true nutrition, and as the decomposition 

 of the carbonic acid gas which results from this assi- 

 milation sets free a much larger quantity of oxygen 

 than the plant requires for itself, it was for a long 

 while believed that- plants really breathed the car- 

 bonic acid gas of the air, in the inverse method to 

 that of animals. 



Fig. 1. Agaricas in different stages of development : 2, 3, 3 vertical section showing 

 the formation of the head. The hyphse f the mycelium are shown in the lower 

 part of the figure. 



The assimilation of carbon is effected by the leaves 

 and green parts of plants ; the green, granular sub- 

 stance termed chlorophyll, which solely gives them 

 this colour, as may be shown by the microscope, and 

 which alone subserves this function of nutrition. 

 Fungi, however, have no leaves nor other green parts ; 

 that is, they have no chlorophyl. They derive the 

 cellulose which they contain, as well as all the sub- 

 stances by which they are nourished, either from 



