416 PHARMACEUTICAL BOTANY 
Repropuction.—Lichens reproduce either by producing 
spores or by detaching scale-like portions of their bodies. In 
the Asco-lichens (which make up the majority) either saucer- 
shaped structures called apothecia (sing. apothecium) occur on the 
upper surface or dark-colored, spherical structures called peri- 
theca somewhat embedded in the upper surface, arise. In either 
type of structure asci and sterile hyphz (paraphyses) arise. Each 
ascus usually contains eight spores. The. spores_upon_maturity _ 
are liberated, each germinating in the presence of moisture into a 
Fic. 310.—Roccella tinctoria, a dye-yielding lichen. (From Strasburger after Wiesner.) 
hypha. The hypha, upon coming into contact with an alga cell, 
grows around it to form a lichen. ~~ > 
Seales or soredia aré found on many lichens. These consist 
of a network of hyphze enclosing algal cells. By becoming 
detached from the parent plant, they develop new lichens and so 
constitute a means of vegetative propagation. 
Usrs.—To the pharmacist and chemist lichens are chiefly of 
interest because of the coloring principles which they contain. 
Species of Lecanora and Roccella tinctoria yield, when subjected to 
fermentation, the dyes orcein and litmus. Litmus is one of the 
best indicators in volumetric analysis. Cudbear, a purplish-red 
powder, used extensively for coloring pharmaceutical prepara- 
tions in the form of tincture, is prepared by treating species of 
Roccella, Lecanora or other lichens with ammonia water. Other 
