28 CETRARIA. 



III. CETRARIA (Ach.) Fr., Miill. 



Apothecia scutellaeform, then often dilated, or peltseform, 

 affixed obliquely to the tips or margins of the thallus, from 

 which the disk differs in colour. Spores sub-ellipsoid, 

 simple, colourless. Spermatia oblong, either thickened at 

 one, or both ends, or cylindrical; or staff-shaped; upon 

 sparingly branched sterigmas. Thallus typically ascendant ; 

 either fruticulose, with now terete-compressed, now turgid, 

 or now channelled branches ; or expanded and foliaceous ; 

 cartilagineous or now membranaceous ; glaucescent, or 

 much more often brown, or yellowish ; the medullary layer 



cottony. Anatomy of the thallus of the first sub-section, 



and of the second and third sections, given in Schwendener, 

 Untersuch. I. c. 2, p. 149, t. 3,/. 30-33, t. 4,/. 1-12 ; and of 



the second sub-section in Nyl. Syn. I, p. 286. The type 



of Cetraria is to be looked for in its alpine species; and 

 especially in those of the second section, which are at once 

 fruticulose and yet sub-foliaceous. From this centre diverge, 

 on the one hand the two well-marked clusters with teretish 

 thallus; and, on the other, we find receeding the finally 

 quite foliaceous and Parmeliiform third section. 



* Thallus fruticulose, terete-compressed. 

 f Thallus slender, brownish, rigid. 



1. C. tristis (Web.) Fr. ; thallus tufted, fruticulose, erectish, 

 very rigid and tenacious, compressed-terete, divided sparingly 

 below, but the tips often passing into fastigiate branchlets; 

 brownish -black; apothecia middling -sized to ample, sub- 

 terminal, appendiculate by the deflexed tips, plano-convex, the 

 disk dark-chestnut, the margin entire or toothed, or now radiate. 

 Spores ellipsoid, 7 - 10 mic. Spermogoues and spermatia much 



as in the next. -Fr. L. E. p. 34. Scluzr. Spicil. p. 258. Pla- 



tysma, Nyl. Syn. I, p. 307. 



Alpine rocks. Arctic America (Richardson), Hooker in Frankl. 



Narr. 1823. Alpine region of Mt. Hood, Oregon, Hall. The 



quality and amount of anatomical difference in the thallus 

 (Schwend. I. c. p. 149) is scarcely sufficient to obscure the mani- 

 festly close relation of this lichen to Cetraria. 



