FINK—THE LICHENS OF MINNESOTA. 57 
Collected in several widely separate portions of the State and no doubt generally 
distributed. The plant resembles certain Lecideas externally and is easily overlooked. 
On trees, especially on poplars. 
The species is reported from widely separate portions of North America, but neither 
from the extreme north or south. Also known in Europe. 
2. Arthonia convexella Nyl. Act. Soc. Linn. Bord. 2:415. 1856. 
‘Thallus white, ashy, or greenish, partly epiphlaeodal but thin and smooth and fre- 
quently dying away, the patches in material examined scarcely exceeding 20 or 30 mm. 
across; apothecia black, rounded or rounded-oblong, convex and rugulose, minute, 0.2 
to 0.4 mm. in diameter; hypothecium heavy and blackish brown; hymenium brown 
or reddish brown; paraphyses usually branched and resembling the hyphe, the apex 
brownish; asci broadly clavate or subpyriform; spores 2-celled, hyaline to brown, 
solezeform, 11 to 14 » long and 4 to 6 ” wide. 
Differs from‘ours of the last in the brown spores and the smaller, more convex 
apothecia. 
Once collected in the State at Beaudette, along the international boundary, on 
balsam. 
The only other station for the plant found reported is in France. 
3. Arthonia dispersa (Lam. & DU.) Duf. Journ. Phys. Chem, Nat. Hist. 87: 203. 1818. 
Opegrapha dispersa Lam. & DC. FI. Fr. ed. 3. 2: 308. 1805. 
Thallus white or whitish, mainly hypophloodal, thin, smooth, occurring in patches 
from 6 to 70 mm. in longest dimension, or these running together and covering larger 
areas; apothecia punctiform, rounded, oblong, difform, or even branched, commonly 
more or less immersed in the thallus or the substratum, minute, the dimensions 0.1 to 
0.4 mm.; hypothecium thin, pale or pale brownish; hymenium pale or very pale 
brownish; paraphyses not distinctly seen, probably merely a mass of more or less gela- 
tinized hyphe; asci pyriform; spores 2-celled, solezeform, 11 to 16 long and 4 to 
5 p wide. 
The most commonand most widely distributed of the genus in Minnesota. On trees, 
especially common on Acer spicatum in the northern portion of the State. 
Apparently generally distributed throughout the United States, and extending at 
least as far north as Newfoundland. Known also in Europe. 
4. Arthonia lecideella Nyl. Mém. Soc. Sci. Nat. Cherb. 5: Suppl. 337. 1857. 
Thallus greenish to sea-green or lighter, rather thick, continuous or rarely subareolate, 
uneven and epiphleeodal, occurring in irregular patches 5 to 25 mm. in the longest 
diameter and sometimes running together and covering larger areas of the substratum; 
apothecia dark brown or black or frequently grayish- -pruinose, quite numerous, plane 
or convex, rounded, small, 0.2 to 0.4 mm. in diameter, immersed or adnate; hypothe- 
cium brown or dark brown; hymenium light brown or at least brownish; paraphyses 
short-jointed and freely branched, the apices of the branches sometimes enlarged and 
darker; asci clavate to subpyriform; spores solezform, 4-celled, 16 to 23 » long and 
5 to 6.5 » wide. 
Generally distributed over the State. On trees and old wood. 
A strictly North American lichen, common in the Mississippi Valley, ranging east- 
ward to the Atlantic and northward into British America. 
5. Arthonia punctiformis Ach. Lich. Univ. 141. 1810. 
Thallus mainly hypophleeodal and finally dying away, when present giving a whitish 
cast to the substratum, occurring in irregular patches frequently reaching 75 mm. or 
more in the longest dimension; apothecia oblong, sublinear or more commonly difform 
or even rounded, black, plane or slightly convex, adnate or immersed, minute, 0.1 to 
7920—10—\5 
