FINK—THE LICHENS OF MINNESOTA. 135 
4. Synechoblastus nigrescens (IHuds.) Stizenb, Ber. St. Gall. Ges. Naturw. 1861- 
62: 144. 1862. PLATE 20, A. 
Lichen nigrescens Huds. Fl. Angl. 450. 1762. 
Thallus foliose and commonly orbicular, middle-sized, 30 to 75 mm, in diameter, 
closely adnate, rather thin, closely beset with pustules on many of which are com- 
monly situated apothecia, or the pustules largely absent and replaced by radiating 
ridges, the short, rounded marginal lobes entire and usually more or less raised; 
olivaceous-green and blackening, below lighter and marked by depressions corre- 
sponding to the pustules or ridges of the upper surface, algal cells rather more numerous 
toward the upper surface, rhizoids few and weak and scarcely of use as attaching 
organs; apothecia small, 0.5 to 1.25 mm. in diameter, sessile, frequently numerous 
and nearly obscuring the thallus, the disk brown or reddish brown, becoming convex, 
the thin margin sometimes disappearing; hypothecium pale; hymenium pale below 
and brownish above; paraphyses simple, or rarely branched toward the frequently 
enlarged and brownish apex; asci clavate; spores long-fusiform and acicular, several- 
celled, 50 to 72 » long and 4 to 6.5 » wide. 
Confined to the northern portion of the State. On trees, especially poplars. 
Widely distributed in North America. Known in all the grand divisions except 
South America. 
Collema nigrescens of the preliminary reports. 
EXPLANATION OF PLATE 20.—A, plant of Synechoblastus nigrescens on poplar, showing the foliose thallus 
and the rather inconspicuous apothecia. B, plant of Ephebe pubescens on rocks, showing the fruticose 
thallus, whose form is determined by the algal symbiont Sirosiphon.« A and B enlarged 2} diameters. 
4a. Synechoblastus nigrescens leucopeplus (Tuck. ) Fink. 
Collema nigrescens leucopepla Tuck, Gen. Lich. 92. 1872. 
Apothecia white-pruinose, said to be smaller, as also the whole plant. Ours scarcely 
distinct and possibly not the subspecies. 
Frequent in the northwestern portion of the State, along the boundary especially. 
On trees, 
A North American form, previously reported from several southeastern States. 
Ours quite as distinct as the material distributed in ‘‘Lichenes Boreali-Americani,”’ 
number 114, from South Carolina. 
Collema nigrescens leucopepla of the preliminary reports. 
5. Synechoblastus ryssoleus (Tuck.) Fink. 
Collema nigrescens ryssoleum Tuck, Lich. Calif. 34, 1866. 
Thallus commonly orbicular, less closely attached to the substratum than the last, 
in the material at hand 20 to 45 mm. in diameter, rather smooth above, the rounded 
lobes ascendant with plicate-undulate and crisped margins, rugose-papulose above; 
olivaceous or at length blackish brown, beneath paler and reticulate-lacunose; algal 
cells rather more numerous toward the upper surface; rhizoids few and weak, and 
the gelatinous thallus here and there directly adnate to the substratum; apothecia 
small, 0.5 to 1.5 mm. in diameter, sessile, scattered or crowded, the disk brown or 
reddish brown, flat or convex, the thin entire margin sometimes disappearing; hypo- 
thecium pale brownish; hymenium pale below and brownish above; paraphyses 
simple or branched toward the apex, there also frequently thickened and brownish; 
asci clavate; spores ovoid and becoming subacicular, 4 to 8-celled, 22 to 26 » long 
and 5 to 7 » wide. 
Collected on poplar at Bemidji. The material was scanty and the habitat unusual 
for the species, but the plant was more like the present externally, and the spore 
measurements preclude its belonging to the last above. 
Otherwise known throughout the eastern United States and as far west as Ohio. 
Not found recorded for any locality outside of the United States. 
Collema ryssoleum of the preliminary reports. 
= a ana 
_—— ors 
aSee footnote, p. 23, 
