FINK—THE LICHENS OF MINNESOTA. 51 
reaching 5. Considered by Nylander to be a subspecies of the last, and certainly very 
near. 
Collected in northeastern Minnesota at Two Harbors, Ely and about Snowbank 
Lake. On decorticated coniferous wood. 
New Bedford, Massachusetts, is the only other North American locality. Known 
also in Europe. 
Calicium brunneolum of the preliminary reports. 
ACOLIU®™ S. F. Gray, Nat. Arr. Brit. Pl. 1: 482. 1821. 
The thallus is crustose and verrucose, or more commonly more or less distinctly 
areolate, with the areoles usually forming a continuous crust. There is no cellular 
cortex and no algal nor medullary layers, yet the thallus is rather thick and much 
better developed than in either Calicium or Coniocybe, and more like that of Chaeno- 
theca. The thallus seldom or never becomes inconspicuous or disappears, except in 
a few parasitic species, from which it seems to be entirely absent. The algal sym- 
biont is the form of Cystococcus usually found in members of the present family. 
The apothecia are borne upon a very short stipe, and both stipe and apothecium 
are frequently embedded in the thallus, so that there seems to be simply the immersed 
apothecia, the peculiar structure in such instances only appearing in vertical sections 
through stipe and apothecium. In all of the species is found the dark proper exciple, 
and in those having the stipe and apothecium immersed in the thallus it is usual to 
think of the surrounding thallus layer as a thalloid exciple. The disk is more or less 
concave, even reaching cup-shaped conditions. Both simple and 2-celled spores are 
found in plants commonly admitted to the genus, and not infrequently the whole 
range of forms from the simple spore to the muriform condition is included in the one 
genus. This mass of forms is in need of careful revision, but our flora presents no 
difficulty in this regard, as we have but two species, these with the usual 2-celled 
brown spores. The asci dissolve while the spores are quite immature. 
The close relationship of the present genus to Chaenotheca, Calicium, and Coniocybe 
is apparent enough in species of Acolium, having the short stipe exposed above the 
thallus, and is just as apparent in such species as ours when studied in section. 
Two species are found in Minnesota. On old pine boards, posts, and trees. 
Type species Acolium tigillare (Ach.) 8. F. Gray, loc. cit. 
KEY TO THE SPECIES. 
Stipes very short and apothecia immersed............-..---+-- 1. A. tigillare. 
Stipes longer and apothecia sessile or slightly elevated......... 2. A. lucidum. 
1. Acolium tigillare (Ach.) 8. F. Gray, Nat. Arr. Brit. Pl. 1: 482. 1821. 
Lichen tigillaris Ach. Lich. Suec. 67. 1798. 
Thallus yellowish green or lemon-yellow, crustose, and usually quite prominent, 
chinky and soon becoming areolate, or rarely granular, commonly widely spread 
over the substratum as a continuous or more or less broken layer; apothecia smail, 
0.3 to 0.6 mm. in diameter, on very short stipes, both apothecia and stipes being 
immersed in the thallus in areolate thalli, one or more apothecia in each areole, or 
rarely more or less superficial, the disk dull black and flat or somewhat concave, the 
proper exciple black; hypothecium dark brown; hymenium pale or slightly colored; 
paraphyses rather short and slender and commonly simple, with scarcely enlarged or 
colored apex; asci long, cylindrical, soon dissolving; spores blackish brown, 2-celled, 
constricted at the septum, 12 to 20 » long and 7 to 10 » wide. 
Widely distributed in the State, and to be looked for wherever boards or posts of 
pine fences have stood long enough for the plant to become established. 
Throughout the eastern portion of North America from the Gulf of Mexico to the 
Arctic Ocean. Known also in Europe. 
