LICHENS. II 
Besides these true organs of fructification, the 
lichens are furnished with other parts which pos- 
sess the power of reproduction. A great many 
species, placed in unfavourable circumstances, 
seldom or never produce proper receptacles of 
seed; but this is no obstacle to their propaga- 
tion, as their whole surface is covered with collec- 
tions of free powdery grains, which germinate 
into new plants wherever they are carried by the 
winds. There are also present on some lichens 
spongy excrescences which resemble minute trees; 
and one peculiar genus is possessed of tubercles 
which occur on the back part of the frond, and 
are lodged in little cups which appear empty as 
soon as they have fallen out. The recent re- 
searches of the French lichenists, Tulasne and 
Itzigsohn, have discovered another kind of fructi- 
fication which is very common and exceedingly 
interesting. This consists of minute, blackish, 
elevated, somewhat gelatinous points called sper- 
mogonia, occurring on various parts of the upper 
surface of the thallus. These resemble, in ex- 
ternal appearance, the tubercular apothecia of the 
Lecideas ; but their internal structure, as shown 
in Fig. 8, is quite different. They consist of 
little cavities or utricles opening on the summit 
by a tiny orifice, and filled with a thin transparent 
mucilage, in which is contained a number of 
