LICHENS UNDER THE MICROSCOPE. 613 
great importance in the determination of species, so that 
the study of lichens cannot now be successfully or thor- 
oughly prosecuted without an acquaintance with them. Their 
general form and Fig. 150. 
color being constant 
in each genus and 
species, they have, 
as Professor Tuck- 
erman observes (Li- 
chens of California), 
“added a new con- 
tent to the conception of species.” While their study opens 
fresh difficulties and perplexities to the student, it affords 
him a deeper insight into the inscrutable mysteries of nature, 
who, whatever we 
Spermatia, 
Fig. 151. à 
may strive to ascer- 
tain, ever holds some 
secrets in reserve 
which are beyond 
our grasp. 
In its earliest 
stages the spore-case 
appears filled with 
small globular gran- 
ules, in which lines 
of division appear, 
and the spores grad- 
ually assume their 
regular form and 
number. The spores 
are at first colorless 
Section of pyenide or Biatora Heer. s, tylosporesz £ thal- and simple, and their 
cy: pipes internal divisions 
all gradations in the 
ed with a mass 
d in à linear 
and vdd of color may be seen in 
same hymenium.. They frequently remain fill 
of oil globules: They are sometimes arrange 
AMER. NATURALIST, VOL. IV. 85 
