FINK—THE LICHENS OF MINNESOTA. 167 
black, and gray. The lower surface is commonly black and is usually roughened or 
ciliate. In some of the species longitudinal or vertical plates for support replace the 
rhizoid-like cilia of the lower side of the thallus. 
What is commonly considered an apothecium seems rather to be agroup of (usually 
elongated) apothecia closely clustered upon a very short dichotomously branching 
pedicel. This. peculiar structure is very apparent as seen in sections, and even with a 
hand lens the individual apothecia may usually be plainly distinguished. The 
apothecia sometimes occursingly. There isa thalloid exciple, usually blackened and 
devoid of algal cells. The paraphyses are simple or branched. The spores are simple, 
ellipsoid in form, and pale or hyaline. 
The genus is peculiar in many ways, as appears from a study of the above brief 
description, and is not very closely related to any other genus except Umbilicaria, 
which is commonly included with Gyrophora. The two genera show forms with thalli 
closely resembling Endocarpon externally. 
Four species of the genus occur in Minnesota, all in the northern portion of the State, 
Ours are always found on the igneous or metamorphic rocks. 
Type species Gyrophora arctica Ach. op. cit. 106. 
KEY TO THE SPECIES, 
Thallus ash-colored above, rhizoid-bearing below......-------- 3. G. vellea, 
Thallus brownish, ashy brownish, or blackish above, with or 
without rhizoids. 
Thallus clothed below with long, dark rhizoids.........--- 4. G. dillenini, 
Thallus without rhizoids below. 
Thallus more or less pitted and lacunose below....---- 1. G. hyperborea. 
Thallus reticulated with plates below......-..-------- 2. G. muhlenbergi. 
1. Gyrophora hyperborea Ach. Meth. Lich. 104. 1803. PLATE 31, 
Lichen hyperboreus Ach. Vet. Akad. Handl. 15: 89. 1794. 
Thallus rounded or irregular in form, the edges more or less jagged and irregular, and 
sometimes even irregularly lobed, small or middle-sized, 30 to 75 mm, in diameter, 
papulose-roughened, sometimes sparingly perforate, usually occurring singly but 
sometimes several thalli more or less imbricated in a cluster; olivaceous or blackish 
brown, beneath brown to blackish, smooth and more or less pitted and lacunose; apo- 
thecia sometimes single but usually in groups, the groups considerably raised and black, 
more or less rounded and convex, 0.5 to 2.5 mm. in diameter and sometimes containing 
100 or over more or less elongated and variously curved apothecia, each apothecium 
having a black thalloid exciple; hypothecium dark brown; hymenium pale to light 
brown; paraphyses simple or branched, commonly thickened and brownish toward 
the apex; asci clavate; spores pale, ellipsoid, 12 to 17 » long and 5 to 8 1 wide. 
Collected only in the extreme northern portion of the State, the only undoubted 
specimens thus far from the shores of Lake Superior. On rocks. 
Found in the United States only in the eastern and western mountains and along 
the north shore of Lake Superior, but extending northward into arctic regions. Also 
frequent in northen Europe and Asia. 
Umbilicaria hyperborea of the preliminary reports. 
EXPLANATION OF PLATE 31.—Plant on high rocks, showing the irregularly lobed and jagged thallus. 
Natural size. 
2. Gyrophora muhlenbergii Ach. Lich. Univ. 227. pl. 2. f. 11. 1810. 
Thallus usually more or less irregular in outline or even lobed, the margin more or 
less jagged and irregular, middle-sized or large, 5 to 17,5 cm. in diameter (in some speci- 
mens found in the State even exceeding 30 cm, in the longest diameter), sometimes 
more or less perforate, the smooth upper surface more or less reticulately pitted, brown 
