FINK—THE LICHENS OF MINNESOTA. 141 
Tuckerman considered the North American plants to belong to the present sub- 
species or to Leptogiwm lacerum lophaewm (Ach.) Nyl.¢ Possibly the last named 
subspecies, also a small form with long ciliately dissected lobes, may exist in the State. 
Both subspecies are recognized in Europe and Africa. 
2. Leptogium pulchellum (Ach.) Nyl. Syn. Lich. 1: 123. 1858. 
Collema pulchellum Ach. Syn. Lich. 321. 1814. 
Thallus suborbicular, middle-sized to large, 5 to 12.5 cm. in diameter, closely 
adnate, but the marginal lobes commonly free and more or less raised, as are fre- 
quently some of the more central ones also, the upper surface thrown into delicate 
plicate wrinkles, and the lower surface more or less pitted and similarly wrinkled, 
the lobes somewhat imbricated, rounded with entire or slightly undulate margins; 
commonly lead-colored above, lighter-colored beneath, for most part adhering directly 
to the substratum, the rhizoids few and, as in other species, only to be seen in sec- 
tions; algal chains more numerous toward the top, but quite numerous toward the 
lower side also, the central portions having few algal cells and representing a 
more or less distinct medullary layer; apothecia small to middle-sized, frequently 
subpedicellate, 0.7 to 2 mm. in diameter, the exciple thalloid with usually entire 
margin, the disk commonly flat; hypothecium brownish; hymenium pale below and 
brownish above; paraphyses simple or rarely branched; asci clavate; spores pale, 
becoming more or less muriform, ellipsoid, 18 to 30 » long and 9 to 16 » wide. 
Collected in widely separate portions of the State and no doubt generally distrib- 
uted, though rare. On trees and once on rocks. 
Doubtless generally distributed over North America, except in arctic regions; 
little known, however, in the West. A strictly American plant. Known also in 
South America. 
3. Leptogium tremelloides (L.) S. F. Gray, Nat. Arr. Brit. Pl. 2: 400. 1821. 
PLATE 22, 
Lichen tremelloides L. {. Suppl. Pl. 450. 1781. 
Thallus suborbicular, middle-sized, 30 to 75 mm. in diameter, rather less closely 
adnate than that of the last and somewhat thinner, the lobes more or less imbricated, 
smooth, of somewhat similar form, but smaller, with commonly more ascending and 
entire margins, but sometimes finely dentate or undulate, crisped and irregular; 
beset more or less with isidioid granules, which may pass into minute lobules, lead- 
colored, frequently somewhat lighter below; rhizoids very rare and only seen in 
sections; algal chains more numerous toward the upper surface, but a medullary 
region scarcely to be distinguished in the thin thallus; apothecia sessile or subpedi- 
cellate, somewhat smaller than in the last, 0.5 to 1.7 mm. in diameter, the disk brown 
and flat, or somewhat convex and sometimes overgrowing the entire or irregular 
thalloid margin; hypothecium commonly pale; hymenium pale throughout or 
brownish above; paraphyses simple or very rarely branched, frequently enlarged and 
brownish toward the apex; asci clavate; spores pale, ovoid-ellipsoid, becoming 
muriformly many-celled, 18 to 27 » long and 8 to 12 » wide. 
Throughout the northern portion of the State, extending as far south as Taylors 
Falls. Commonly on rocks. 
Throughout the portion of North America east of the western Cordilleras and also 
in Alaska. There are several subspecies, and one or more forms are known in all of 
the grand divisions. 
4. Leptogium chloromelum (Sw.) Nyl. Syn. Lich. 1: 128, 1858, 
Lichen chloromelos Sw. Fl. Ind. Occ. 3: 1892. 1806. 
aSyn. Lich. 1: 122. 1858. _ 
