THE SP()RE-SA(; LK'HEXS 



607 





'Wms 



Fig. 335. — Iceland moss. A small part of the apothccium and thallus shown 

 in Fig. 334, magnified 400 diameters; showing the spore-saes or asci (a), 

 the paraphyses (p), the compact laj-er of mycelium (s) from which they 

 arise, the algas (Pleurococcus) known as "gonidia" (g). the cottony 

 mycelium (m), and the compact protective rind (r, r'). (Luerssen.) 



Fig. 336, I. — Beard-lichen (Usnea barbata, Beard-lichen Family, Ustrcacece). 

 Natural size. Granules often appearing on the surface are soredia. 

 (Baillon.) — Grayish or dull yellowish green throughout; often much 

 longer than shown, w'ith a tough central. Common on trees in various 

 parts of the world. 



finally, keeps them supplied with all the carbon dioxicl 

 they need as a raw material for their food. Dissimilar or- 

 ganisms living thus together with benefit to both are called 



