CRYPTOGAMS 333 
that make up the lichen thallus would probably have to be 
classified separately, as alge or fungi, respectively, but as 
fructification is the generally accepted basis of classification, 
and the plant body is too intimately permeated with both 
kinds of tissue to be divided, each lichen body as a whole is 
classed with its particular kind of fungus. The entire group, 
on account of the distinctive characters that mark it, is 
473 A74 
Figs. 473, 474.—Fruticose lichens: 473, Usnea barbata, bearded lichen; 474, 
Cladonia rangiferina, reindeer moss: A, sterile; B, fruiting portion. 
placed in a separate order of its own. This includes three 
principal divisions, distributed according to the shape of the 
thallus, and its habit of growth: (1) Crustaceous, those that 
adhere closely to the substratum, as if glued or inscribed on 
it; (2) Foliaceous, with a broad, more or less lobed and leaf- 
like thallus that adheres loosely to the substratum by means 
of rhizoids springing from its under surface; (3) Fruticose, 
with branching, stemlike thallus attached at the base like a 
regularly rooting plant (Figs. 473, 474). Among these are 
the Iceland moss, used as an article of food by man, and the 
reindeer moss (Cladonia rangiferina), which is the chief sus- 
tenance of the reindeer. , 
