176 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
lighter-colored and sometimes more or less white-powdery; apothecia smaller, more 
inclined to immersed conditions, the exciple usually entire. 
Collected at Mankato and at Battle Lake. On limestones. No doubt occurs on 
the same rocks in other portions of the State, especially in the southeastern portion, 
Elsewhere in North America in Iowa, Nebraska, Missouri, Kansas, and Newfound- 
land. Known also in Europe. 
EXPLANATION OF PLATE 33.—Plant on rocks, showing the fairy ring formation characteristic of this 
subspecies. Natural size. 
2c. Lecanora muralis garovaglii (Koerb.) Tuck. Syn. N. A. Lich. 1: 184, 1882, 
Placodium garovaglit Koerb. Par. Lich. 54. 1865. 
Thallus lobes elongated, flexuous, convex, plicate-radious, normally colored. 
Collected at Koochiching on the northern boundry of the State. On rocks, 
Known elsewhere in North America in Nebraska, Nevada, and Newfoundland, 
Found also in Europe and Africa. 
2d. Lecanora muralis diffracta (Ach.) Tuck. Syn. N. A. Lich, 1: 184. 1882, 
Lichen diffractus Ach. Lich. Suec. 63. 1798,” 
Thallus darker, usually yellowish brown or reddish brown, central areoles scattered 
more or less and frequently black-margined, the lobes of the margin short. 
Collected at Grand Portage, on Mount Josephine. On rocks. The material referred 
to here is uncertain. 
Elsewhere in North America in California. Known also in Europe. ? 
3. Lecanora pallida (Schreb.) Schaer. Enum. Lich. Eur. 78. 1850. 
Lichen pallidus Schreb. Spic. Fl. Lips. 133. 1771. 
Thallus crustose, neither lobed nor in any degree foliose, but closely adnate and, 
like the other crustose species, attached by hyphal rhizoids, usually thin and smooth, 
but becoming thicker and chinky or somewhat verrucose, whitish or pale cream- 
colored and darkening, cortical layer scarcely developed, usually somewhat irregular 
in form and 5.5 to 10 cm, across, or even more widely spread; apothecia sessile or 
more commonly adnate, small to middle-sized, 0.7 to 3 mm. in diameter, the disk 
whitish buff and white-pruinose, flat, with a thick and entire exciple, or becoming 
convex and sometimes irregular, and the margin rarely disappearing or more com- 
monly becoming flexuous; hypothecium pale; hymenium pale throughout or some- 
what brownish above; paraphyses commonly simple and more or less gelatinized, 
frequently enlarged and brownish above; asci clavate; spores ellipsoid, 7 to 15 ue long 
and 5 to 8 « wide. 
Thus far collected only in the northern portion of the State, but the plant occurs 
in northern Iowa and doubtless also farther south in Minnesota, On trees. 
Generally distributed throughout North America. Known in all of the grand 
divisions. 
3a. Lecanora pallida angulosa (Schreb.) Koerb. Syst. Lich. 145. 1855. 
Lichen angulosus Schreb. Spic. Fl. Lips. 136. 1771. 
Apothecia becoming crowded with angulate and variously irregular exciple, the 
disk rather more darkly subpruinose, 
In our single specimen the exciple is persistent and the thallus rather thick and 
subverrucose or chinky-subareolate. The specimen was collected at Duluth by Anna 
M. Kimball and has not otherwise been reported from the State, On trees. 
Scarcely referred to in North America lists except in a general way in Tuckerman’s 
Synopsis, but no doubt quite widely distributed. Known also in Europe and Africa. 
4. Lecanora atra (Huds.) Ach. Lich. Univ. 344. 1810. 
Tichen ater Huds. Fl. Angl. 445. 1762. 
Thallus crustose and of moderate thickness, composed of granules which usually 
run together into a smoothish or more commonly verrucose or areolate crust, occurring 
