FINK—THE LICHENS OF MINNESOTA. 201 
Occurs in all parts of the State; common in the northern part but rare southward. 
On trees, occasionally on old wood, and once on sandstone. 
The plant occurs throughout the United States, and also northward, but usually in 
a dwarfed condition tending toward the next species. The species is strictly Ameri- 
can, having been sent to Acharius by Muhlenberg. Nylander records it from Peru; 
otherwise only known in North America. 
3. Cetraria saepincola (Ehrh.) Ach. Meth. Lich. 297. 1803. 
Lichen saepincola Ehrh. Hannover. Mag. 206. 1787. 
Thallus foliose, small, scarcely exceeding 5 to 15 mm. in diameter (the plants 
usually densely clustered along small twigs, the limits of individual plants thus 
difficult to determine), the lobes few and short, prostrate or somewhat ascending, 
smooth or more or less rugose, their margins undulate, crenate, or incised; olivaceous 
or brown above and paler beneath, without fibrils; apothecia rather small, 0.7 to 4 
or possibly 5 mm. in diameter, sessile on the margins of the lobes, frequently numerous 
and almost completely obscuring the small lobes, the disk of the same color as the 
thallus or darker brown, usually concave, the thalloid margin entire or crenulate 
and usually disappearing; hypothecium pale; hymenium brownish above and 
gradually becoming pale or paler brownish beneath; paraphyses conspicuously jointed, 
simple or branched, pale or brownish, and usually thickened toward the apex; asci 
cylindrico-clavate; spores short-ellipsoid, 7 to 9.5 » long and 4 to 6 « wide. 
Once collected in the State, along the shore of South Fowl Lake, on the northern 
boundary. Also found on Isle Royale in 1902. On small twigs. 
Essentially an arctic plant, occuring in the northern portions of North America, 
and farther south in mountains and along cold shores. Also reported from the 
extreme southern portion of South America and in northern Europe and Asia. 
4. Cetraria lacunosa Ach. Meth. Lich, 295. pl. 5. /. 3. 1808. 
Thallus foliose, middle-sized or large, 5 to 14 cm. in diameter, the lobes crowded, 
quite wide and rounded, ascending, with crenate or lacerate margins, sea-green and 
reticulate-lacunose above, lighter-colored or sometimes blackening beneath, without 
marginal cilia; apothecia often quite numerous, reaching good size, 1 to 10 mm. in 
diameter, sessile or subpedicellate on the margins of the lobes, frequently perforate 
at the center, the perforation extending through the thallus lobe also, the disk chestnut- 
brown, concave, with a thin entire thalloid margin which sometimes finally disappears; 
hypothecium pale; hymenium brownish above and gradually becoming paler within; 
paraphyses simple or branched, pale or brownish, frequently somewhat thickened 
toward the apex; asci clavate or cylindrico-clavate; spores short, oblong-ellipsoid, 
5 to 8 » long and 4 to 5 » wide. 
Common in the northern part of the State, but not known to exist in the southern 
half or two-thirds. On trees. 
The plant is strictly North American and is common on trees and rails in the north- 
ern half of the United States, and found also in British America, Alaska, and farther 
south in the mountains. Not known to be confined to especially cold regions, though 
its distribution in Minnesota would seem to indicate this, it being especially common 
in the northeastern portion of the State. This distribution would seem to indicate 
that our plant might be the closely related Cetraria glauca (L.) Ach., though its 
characters are plainly those of the present species. 
5. Cetraria aurescens Tuck. Syn. Lich. N. E. 16. 1848. 
Thallus foliose, middle-sized or smaller, 15 to 60 mm. in diameter, the surface quite 
smooth, sinuously or laciniately lobed, the lobes many-cleft, the ascendant margins 
crisped; straw-colored varying toward sea-green above, beneath whitish and clothed 
more or less with whitish or pale brownish fibrils; apothecia of good size, 1 to 7 mm. in 
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