VEGE TA TI VE REP ROD UCTION. 



225 



as homologous with a hair. Sometimes the sporangia, 

 although really free, are overgrown by adjacent parts, so that 



FIG. 225. A lichen (Parmelia co n spersa) growing on a stone, showing the leaf-like 

 thallus (mycelium*, with many fructifications (apothecia). The older ones are more 

 or less irregular and large with a narrow rim ; the younger are nearer the margin, cir- 

 cular, and nearly closed over at top. Natural size. After Frank. 



FIG. 226. A vertical section of an apothecium of a lichen (Anaptychia ciliaris). //, 

 the hymenium ; y, the subhymenium, a layer of densely interwoven hyphae ; t, t, the 

 sterile hyphae which partially enclose the hymenium ; i, the loosely woven hyphae of 

 the thallus ; a, the algae enslaved by the fungus. Magnified about 50 diam. After 

 Sachs. 



they are enclosed in a chamber, whence the spores escape 

 after they are set free by the bursting of the sporangium. 



