FINK—THE LICHENS OF MINNESOTA. 97 
hymenium also commonly dark in section; paraphyses not distinctly seen in ours; 
asci clavate; spores 4-celled, brown, oblong-ellipsoid, 21 to 28 » long and 7 to 9 » wide. 
Collected along the northern boundary at Warroad. On Pertusaria sp. on birch. 
Elsewhere in North America in Greenland. Known also in northern Asia. 
12. Buellia badioatra (Floerke) Koerb. Syst. Lich. 223. 1855. 
Lecidea badioatra Floerke in Spreng. Neu. Entd. 2: 95, 1821. 
Thallus verrucose or more commonly chinky-areolate, the areoles usually convex 
and wart-like, scattered upon the black so-called hypothallus or crowded and forming 
a continuous crust, varying in color from gray to brownish or reddish brown, irregu- 
larly and often widely spread over the substratum; apothecia small, 0.3 to 0.75 mm. 
in diameter, immersed and adnate, the disk flat or slightly convex, black, the exciple 
black, hardly raised above the disk and scarcely noticeable except in section; hy- 
pothecium dark brown; hymenium pale below and dark brown above; paraphyses 
coherent or becoming semidistinct, simple or rarely branched; asci clavate or inflated- 
clavate; spores brown, ellipsoid or oblong-ellipsoid, often somewhat constricted at the 
septum, 25 to 38 » long and 11 to 17 » wide, surrounded by a halo. 
Collected on Blueberry Island in Lake of the Woods. On rocks. Externally quite 
like Rhizocarpon petraeum, of which it may yet prove to be but a 2-celled condition. 
Elsewhere in North America in Greenland and Newfoundland. Known also in 
Europe. 
The position of the species after the 4-celled species may well be questioned, but on 
the whole it seems nearest to Rhizocarpon. 
RHIZOCARPON@ Ram.in Lam. & DC. FI. Fr. ed. 3. 2: 365. 1805. 
The thallus is commonly crustose, though tending toward squamulose conditions 
in one or two species, on the whole better developed than in Buellia, as shown in 
the more conspicuously verrucose and areolate conditions and the absence of granu- 
lose forms, but scarcely showing cellular cortex in any of the species, nor with dis- 
tinguishable algal or medullary layers. It lies plainly above the substratum, to which 
it is attached by hyphal rhizoids, is on the whole considerably thicker and more 
conspicuous than the thalli of Buellias, and never entirely disappears, at least not 
in any of our species. The algal symbiont is as in Buellia. 
In form, position relative to the thallus, color, and nature of the disk and exciple, 
the apothecia are much the same as in the Buellias and Lecideas, but they are on the 
whole rather larger. The spores are peculiar in that, while they usually become brown 
or blackish brown, they are often persistently colorless, so that we find the colorless 
and the brown spores in the same species and even in the same section, and often 
apparently the colorless ones quite as mature as the brown ones. The mature spores 
are 4-celled and muriform and usually surrounded bya halo. It remains to be dem- 
onstrated that the spores pass from a 2-celled condition to the muriform condition in 
any of the species placed here. 
The present genus is closely related to Buellia, from which it has been separated 
on account of the spore characters, this being the more common method of European 
lichenists. The close relationship of the two genera is perhaps best seen in Buellia 
badioatra, which shows quite as many characters of the present genus. We have 
admitted to the genus Buellia two species with 4-celled spores rather than recognize 
as a third genus Dactylospora Koerb. ® ; 
Nine species and subspecies occur in the State. On rocks. 
Type species Rhizocarpon geographicum (L.) DC. loc. cit. 
aThe original spelling is followed. bSyst. Lich. 271. 1855 
