166 BOTANY. 
They abound almost everywhere—on tree-trunks, rocks, old 
roofs, and in many regions upon the ground. They are 
for the most part of a greenish-gray color, and hence are 
often called Gray-mosses. Other colors, as black, purple, 
yellow, and white, are also common. 
349. They are all of rather small size, varying from a 
millimetre or so to 20 or 30 cm. in length. For the greater 
Fie. 90.—A, a flat-growing (foliaceous) Lichen (Sticta Lael Bia 
stemmed (fruticose) Lichen (Usnea barbata); a, a, fruit-discs (apothecia). Nat- 
ural size. 
part the plant-body is flattish, and adherent to the surface 
upon which it grows (A, Fig. 90), but some species have 
more or less elongated branching stems (B). 
350. The plant-body of a lichen is composed of jointed, 
branching, colorless filaments similar to those in the pre- 
ceding orders. They obtain their nourishment from little 
green protophytes, to which they attach themselves parasi- 
