1913] HERRE—LICHENS OF MT. ROSE 305 
30.5 # in breadth by 61-68 # in length; spores colorless, exceed- 
ingly numerous, short ellipsoid to subglobose, 1~2 # broad by 
2-4.5 & long. 
Common on rocks everywhere in the desert about Reno, Nev., at an alti- 
tude of 4709 to 6000 ft.; not rare on Mt. Rose at 8000 ft. and above, and 
abundant in the Sierras along the Truckee River near the Nevada-California 
state line at an altitude of 6000 ft. 
In a preceding paper (Bot. Gaz. 51:286-297. 1911) this plant 
was mistakenly called by me Acarospora thamnina. It is certainly 
the most successful xerophyte of the Nevada desert, growing in the 
driest places, where it is exposed to the most intense light and heat. 
The apothecia are rarely developed, but the scales are commonly 
covered with a parasitic fungus so that they appear fertile, but 
their true condition is readily shown by careful sectioning. 
g. Acarospora thamnina (Tuck.) Herre.—Leconora thamnina 
Tuck., Genera Lichenum, 120. 1872; L. cervina b. thamnina Tuck., 
Synopsis 1:202. 1882.—Thallus of small, dense irregular clumps 
8-15 or rarely 25 mm. or more in diameter, with domelike or irregu- 
larly rounded surface, or more or less flattened. On closer examina- 
tion the surface is seen to be made up of a great number of small 
to minute, closely appressed, and highly irregular, plicate, or even 
imbricate, lobulate squamules; these are continued downward 
into stems which coalesce to form finally flattened, rootlike stipes, 
the whole clump with its basal stipe reaching a height of 10-15 mm. 
in well grown specimens. Color various shades of brown; often 
gray or bluish-gray pruinose; usually more or less blackened by a 
parasitic fungus; the under surface dead black. No reactions 
observable. 
Apothecia rare, small or minute, o.2-0.8mm. in diameter, 
rarely more than one in squamule, immersed, their surface more or 
less roughened or gyrose; thalline margin entire, rather thick; 
much darker in color than the thallus; epithecium yellow; hypo- 
thecium pale; paraphyses simple, straight, their tips not enlarged, 
Oleoguttate, 1-2.7 " broad; asci cylindrical, 13-18» broad by 
48-55 « long; when treated with I the colorless thecium is first 
blue, then wine-red, and finally tawny; spores short ellipsoid to 
ellipsoid, o.75-1.25 » broad by 3.3-4.5 » long. 
