166 



M0TAN7. 



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 



Fio. 90.— A a flat-^owinpr (foliaceous) Lichen (Sticta pulinonaria); B, a 

 stemmed (trutlcose^ Lichen (Usueabarbata); 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- 



