422 FIRST FORMS OF VEGETATION. 
fungi connected with the more remarkable kinds 
of vegetable epidemics, a few words regarding 
their mode of increase and dispersion may not be 
uninteresting. It is a well-known physiological 
axiom, that the simpler an organism, the more 
bountifully is it furnished with the means of propa- 
gating itself. Exposed to numerous contingencies, 
failure of reproduction by one method is compen- 
sated by the development of another. Accord- 
ingly, fungi are provided with two, three, and in 
some cases even with four, modifications of repro- 
ductive power, all equally effectual, though not 
all developed at one and the same time. Every 
filament or cell may contain its germs, and each 
germ spring up into new forms equally fitted for 
propagation in the space of a few hours; nay, 
some may pass through the course of their exist- 
ence in a few minutes, and give birth to thousands 
even under the field of the microscope. In truth, 
the common reproductive bodies called spores do 
not directly propagate the fungus. They germi- 
nate, however, at definite points, and after a time 
produce on their filaments secondary and even 
tertiary spores, which are the true organs of 
reproduction. These, by their minuter size and 
the more delicate spawn which they produce when 
germinating, enter the breathing-pores of the stem 
and leaves, and the tender tissue of the spongio- 
