THALLOPHYTES 
79 
FIG. 188. Parmelia: an almost free foliose lichen 
on bark, showing cuplike apothecia. 
On the basis of habit, three types are recognized: (i) crustose lichens, with 
an undefined mycelium often penetrating the substratum; (2) foliose 
lichens, with a definite liverwort-like thallus, which has marginal 
growth and rhizoids (as 
Physcia, fig. 187, and 
Parmelia, fig. 188); and 
(3) fruticose lichens, 
which are erect and often 
branching (as Cladonia, 
the reindeer moss), or 
pendent and branching 
( Usnea, fig. 189). 
Vegetative multiplica- 
tion is secured by soredia, 
which are scalelike or globular bodies, composed of a little tangle of 
mycelium with some algal cells (figs. 1114-1116). The ascocarps are 
very conspicuous structures, usually being apothecia (disklike forms), 
but some are perithecia. The hy- 
menium is the usual mixture of asci 
and paraph yses, and the ascus pro- 
duces the usual eight ascospores. 
Sex organs. The sex organs of 
the lichen fungus are e vident in some 
cases. The antheridia occur on 
branching hyphae within a con- 
ceptacle-like chamber called the 
spermogomum. They are very small 
cells that bud out and become ab- 
stricted, suggesting conidia, as they 
have often been considered. These 
antheridia are cast off and function 
directly as sperms, as is true of certain 
of the red algae, and they are also 
FlG. 189. Usnea: a pendent and called spermatia. 
branching fruticose lichen, bearing con- The female SCX organ also suggests 
spicuously flaring apothecia. Al ,. ., T , . ,,. 
that of the red algae. It is a multi- 
cellular filament spirally coiled and terminating in a filamentous ex- 
tension to the surface of the thallus. The spirally coiled region has 
been called the archicarp, and the filamentous extension to the surface 
