172 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. 



composed of slender sacs {Asci), having thread-shaped cells intermixed ; 

 and each ascjjs contains few or several spores, which are commonly double 

 or treble. Most Lichens are flat expansions of grayish hue ; some of them 

 foliaceous in texture, but never of bright green color; more are crusta- 

 ceous ; some are wholly pulverulent and nearly formless. But m several 

 the vegetation lengthens into an axis (as in Fig. 580), or imitates stem 



and branches or threads, as in the Eeindeer-Moss on the ground in our 

 northern woods, and the Usnea hanging from the boughs of old trees 

 overhead. 



516. Fungi. For this immense and greatly diversified class, it must 

 here suffice to indicate the parts of a Mushroom, a Sphseria, and of one or 

 two common Moulds. The true vegetation of common Fungi consists of 

 sleuder cells which form what is called a Mycelium. These filamentous 



Fig. 575. A stone on which various Lichens are growing, such as (passing from 

 left to right) a Parmelia, a Sticta, and on the right, Lecidia geographica, so called 

 from its patches resembling the outline of islands or continents as depicted upon 

 maps. 676. Piece of thalUis of Parmelia conspersa, with section through an 

 apothecium. 677. Section of a smaller apothecium, enlarged. 578. Two asci 

 of same, and contained spores, and accompanying filaments; more magnified. 

 579. Piece of thallns of a Sticta, with section, showing the immersed apothecia; 

 the small openings of these dot the surface. 580. Cladonia coccinea; the fructi- 

 fication is in the scarlet knobs, which surround the cups. 



