674 LICHENS UNDER THE MICROSCOPE. 
series in the spore-case, sometimes irregularly grouped, and 
sometimes spirally twisted around a central (ideal) axis. 
When ripe they are expelled from the spore-case by the 
pressure of the paraphyses, which 
when moistened, absorb water co- 
piously. Many observations have 
been made as to the manner of the 
development of the thallus from 
the spore, but the matter is still in- 
volved in a good deal of obscurity. 
On the thallus of most lichens 
are to be seen a number of small 
P more ily magni, showing te black dots , either scattered irregu- 
larly over its surface, or along the 
margin. These are the spermogonea (Fig. 148), and they 
contain, in great numbers, the spermatia, which are ex- 
tremely minute, cylindrical, or needle-shaped bodies, situ- 
ated on the extremities of simple or branched filaments, 
called sterigmata (Figs. 149, 153). Their forms appear to 
be constant in each species, but are much less diverse than 
those of the spores, and they are always colorless. They 
have been supposed to be the male 
organ of reproduction, but nothing 
is certainly known of their functions. 
Nylander, who attaches much import- 
ance to the spermatia in his Syn- 
opsis, distinguishes five forms of 
them. Ist, the acicular slightly swol- 
len at one end, as in Usnea; 2d, 
acicular slightly swollen near the ex- Spores (a), sterigmata and sper- 
tremity, as in Evernia; 3d, straight ual hres ma NEA 
acicular or cylindrical, as in most Lecanoras; 4th, bowed 
acicular, or cylindrical, as in some Lecanoras ; 5th, ellipsoid 
or oblong, as in Calicinm, which last, he says, approach rather 
too near the short cylindrical spermatia. There are no 
spherical spermatia. But he is not fortunate in attempting 
