10 MICROBES, 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 as of development: 2, 3, a vertical section showing 
the formation of the head. The hyphe of 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 
