172 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. 



composed of slender sacs f^/.^/), having thread-shaped cells intermixed ; 

 and each ascus contains few or several spores, which are commonly douM,; 

 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 arc wholly pulverulent and nearly formless. But in several 

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



680 



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

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

 overhead. 



510. Fungi. For this immense and greatly diversilied class, it must 

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

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

 .slender cells \\liieli form what is called a M',<'. -Hum. These filamentous 



Fio. 575. A stone on which various Lichens arc growing, such as (passing from 

 left to right) a Parmelia, a Stieia. and mi the right, Leeidia .nengraphiea. so railed 

 frmn its patches resembling tin- outline of islands or continents as depicted upon 

 maps. 576. Piece of tliallus of I'armelia ronsprrsa, with section through an 

 apotheeium. 577. Section of a smaller apothecium, enlarged. 578. Two asci 



of same, and contained spores, and a impanvini: lilaineiits; more magnified. 



579. 1'ieee of thalhis of a Stieta, with section, showint; the immersed apotliecia; 

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

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



