200 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
KEY TO THE SPECIES. 
Thallus becoming fruticose............2.0.2...2.2.---.2-222-- 1. C. islandica. 
Thallus foliose. 
Thallus usually straw-colored or greenish, 
Thallus straw-colored, varying toward sea-green; whit- 
ish below. ...2.-2..2..20-000.0 002222 5. C. aurescens. 
Thallus scarcely varying from straw-colored above; 
yellowish below.........2.2...0.00.0..00222-0--20--- 6. C. juniperina pi- 
nastri. \ 
Thallus neither straw-colored nor greenish. \ 
Thallus large, reaching 90 mm. in diameter. 
Thallus becoming brownish, inconspicuously lacu- 
nose; margins ciliate. ....2...2222-............ 2. C. ciliaris. 
Thallus sea-green, conspicuously lacunose; mar- 
gins not ciliate... .2...200200000.0.2........... 4. C. lacunosa. 
Thallus small, not surpassing 15 mm. in diameter...... 3, C. saepincola, 
1. Cetraria islandica (L.) Ach. Meth. Lich. 293. 1803. 
Lichen islandicus L. Sp. Pl. 1145. 1753. 
Thallus tufted, fruticose and subfoliose, rigid, variously laciniate, longitudinally 
grooved (canaliculate) or the margins here and there connivent or even uniting, 
bearing cilia or spinules at the margins, and more or less covered with impressed white 
soredia on the outer side of the longitudinal furrows, shining, pale chestnut to oliva- 
ceous or brown toward the top and frequently paler or sanguineous toward the base, 
3 to 8 cm. in length in ours (foreign specimens in the writer’s herbarium reaching 
12 cm.); apothecia reaching 1.5 to 14 mm., sessile at the tips of the lobes, the thalloid 
margin entire or crenulate, thin or disappearing, the disk brown or chestnut, concave, 
flat, convex or irregular; hypothecium pale or pale brownish; hymenium brownish 
above and pale or brownish within; paraphyses usually simple, brownish and some- 
what thickened toward the apex; asci cylindrical to cylindrico-clavate; spores oblong- 
ellipsoid, 6 to 10 u long, 3.5 to 5 » wide. 
Once recorded for the State from the palisades on the north shore of Lake Superior, 
where it occurs on humus over rocks. Noted in a depauperate condition on old wood 
at Grand Portage in 1902. Common on Isle Royale. The soredia are absent in the 
specimen in the writer’s herbarium from Minnesota, but are present in much of the 
material from Isle Royale. Agassiz and Macoun have both found the subspecies 
Cetraria islandica delisei Schaer.4 along the north shore of Lake Superior, and it may 
well be looked for in Minnesota. The writer has also a specimen of the species col- 
lected by Parry in Minnesota or Wisconsin in 1848. 
Distributed throughout all the grand divisions except possibly Africa. Common 
in frigid regions and reaching warmer territory in mountains or along cold coasts. e 
More or less common in such regions in North America.} 
2. Cetraria ciliaris Ach. Lich. Univ. 508. 1810, 
Thallus foliose, 25 to 90 mm, in diameter, sinuously or laciniately lobed, the lobes 
crowded and ascendant, often narrow and many-cleft, more or less lacunose, their mar- 
gin crenate and bearing scattered cilia or fibrils; sea-green to brownish above, 
or less fibrillose and of the same color or lighter beneath; apothecia reaching good 
size, 1.5 to 12 mm. or more in diameter, sessile on the margins of the lobes, commonly 
more or less concave, the disk chestnut-brown or paler, the margin crenulate; hypo- 
thecium pale; hymenium brownish above and pale or brownish below; paraphyses 
simple or branched, somewhat thickened and frequently brownish toward the apex; 
asci cylindrico-clavate; spores subspherical, 5 to 7 » long and 4 to 5 wide. 
more 
@Enum. Lich, Eur. 15. 1850, b The ‘‘ Iceland moss.’’ See p. 35. 
