246 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
STAUROTHELE Norm. Nyt. Mag. Naturv. 7: 240, 252. pl. 2. f. 23. b, ec. 1853. 
The thallus is crustose and usually devoid of distinct differentiation into layers,but 
sometimes shows a poorly developed cellular cortex. It is usually quite thick and 
evident upon the substratum, on the whole rather more so than in the closely related 
Verrucarias, and is verrucose or rarely distinctly areolate. In some of the species it 
is small and more or less orbicular and in others it is widely spread over the substratum. 
The color varies from ashy to dark brown. The nature of the algal symbiont is some- 
what uncertain, being either Pleurococcus or Chroolepus. 
The apothecia are small or minute and entirely or almost. completely immersed in 
the thallus, being indicated at the surface either by dark spots with the ostiole at the 
center of each, or merely by the ostiole. The perithecium is well developed and 
dark in color, dark or blackish brown in section and darker macroscopically. Within 
this is the amphithecium, usually pale. The paraphyses are commonly gelatinized 
and coherent. The spores are muriform and commonly brown or brownish, though 
hyaline spores occur within the genus. 
The present genus seems closely related to Verrucaria, except for the spores, which 
are very different. Indeed, the genera are frequently united by lichenists, but 
evidently without propriety. The spores suggest a closer relationship with 
Endocarpon. 
Three species and subspecies occur in the State. On rocks. 
Type species Staurothele megalospora, Norm. loc. cit. 
KEY TO THE SPECIES. 
Spores eight in each ascus...............2...--.------------- 2. 8S. diffractella. 
Spores two in each ascus, 
Thallus thin, smooth or granulose, ashy-olivaceous or 
brownish..............0000 0000000 e eee eee eee eee eee L. S. umbrina, 
Thallus much thicker, roughened, verrucose or areolate, 
chestnut-brown or darker... .................-------e- la. S. umbrina clo- 
pima. 
1. Staurothele umbrina (Ach.) Tuck. Gen, Lich. 258. 1872. 
Lichen umbrinus Ach. Lich. Suec. 14. 1798. 
Thallus rather thin, smooth or becoming granulose, chinky or even subareolate, 
widely and irregularly spread over the substratum as a continuous or more or less 
broken layer, ashy-olivaceous to brownish in color; apothecia minute, immersed in 
the thallus and indicated by the ostiole or pore, the perithecium brownish-black, the 
amphithecium pale; paraphyses gelatinized and coherent; asci clavate or variously 
irregular; spores brown, muriformly many-celled, oblong, 2 in each ascus, 30 to 48 1 
long and 12 to 18 » wide. 
Collected in the Misquah Hills, about Snowbank Lake, at Mankato, and at Granite 
Falls. On various rocks. 
Elsewhere in North America in New England, Wisconsin, Iowa, and Nebraska. 
Known also in Europe, Asia, and New Zealand. 
la. Staurothele umbrina clopima (Wahl.) Tuck. Gen. Lich. 258. 1872. 
Verrucaria clopima Wahl. in Ach. Meth. Lich. Suppl. 19. 1803. Puate 50, B. 
Thallus much thickened, roughened-verrucose or becoming areolate, chestnut-brown 
or darker; apothecia often deeply immersed and the ostiole depressed. 
Widely distributed over the State, but probably not occurring in the southeastern 
portion. On rocks other than calcareous. 
Elsewhere in North America in the White Mountains (New Hampshire). Known 
also from Europe and Africa. 
EXPLANATION OF PLATE 50.—See page 244. 
