THE SPORE-SAC LK^HENS 505 



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I I 





Fig. 332. — Iceland moss (see also Fig. 161). A, tip of thallus-lobe bearing 

 two fruit-patches, called apothccia, and along the edge a number of 

 projections, known as spcrmagoiies, which contain dust-spores, i. 

 B, edge of thallus bearing four spermagone-projections, Y-. (Luerssen.) 



Fig. 333. — Iceland moss. A spermagone-projection, cut vertically to show 

 the cavity (sp) from which dust-spores arc discharged. (Luerssen.) 



consisting entirely of hypha; fused into a uniform ti.s.sue. 

 Layers of spore-sacs arise near the tips of tlie thallus-loljcs in 

 Cetraria, and numerous projections inclosing dust-spores ap- 

 pear along the margin. 



A singular method of reproduction very common among 



