LICHENS. 113 
and minutest lichens. New modes of reproduction 
are superadded to the primary one; and all these 
kinds of fructification are sometimes found on 
one plant at the same time, each of them being . 
capable, under certain conditions, of producing 
perfect individuals similar to the parent plant. 
It must not be supposed, however, that they all 
exercise their functions at one and the same 
Fic. 8.—UMBILICARIA POLYMORPHA. 
ieee Section of a 
Ny Spermagone. 
ARNE Swot Ny, 
Section of apothecium and of thallus, Section of thallus, showing 
showing the rhizine. spermagone. 
time—for nature is never prodigally wasteful of 
her resources; but where situation, temperature, 
or other conditions interrupt propagation by one 
mode, another is developed more exuberantly 
than usual to supply its place. If there be not 
conditions to produce perfect apothecia, there 
will be soridia, pulvinuli, or cyphelle instead ; 
and just as the chances of failure are great, so are 
H 
