VEGETATIVE REPRODUCTION. 



225 



as homologous with a hair. Sometimes the sporangia, 

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



Fig. 225. — A lichen {P.innelia conspersa) growing on a sti.»ne, showing the leaf-Uke 

 thallus (mycelium*, witli many fructifications lapothecia'. Tlie older ones are more 

 or less in'egular 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 apotliecium of a lichen iAnaftychia ciliaris). h, 

 the hymenium ; y, the subhymemum, a layer of densely interwoven hyphse ; t, t, the 

 sterile hyphse which partially enclose the hymenium ; ??/, the loosely woven hyphse of 

 the thallus; a, the alga; 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. 



