FINK—THE LICHENS OF MINNESOTA. 87 
genus. They are most commonly adnate, though sessile or somewhat immersed con- 
ditions are not unknown. The exciple is strictly lecideoid and frequently disappears. 
The disk is most commonly convex and varies in color from flesh color through various 
shades of brown to black. The hypothecium and the hymenium are usually more or 
less brownish, and the former may become quite dark. However, both may be pale 
in color. The paraphyses are essentially like those of the closely related genera, 
being commonly more or less coherent and simple, though branched forms may be 
looked for in any of the species. The asci differ slightly in that they are usually 
long-clavate or cylindrico-clavate. The spores are of the long slender form called 
acicular and are from 4 to 16-celled. Possibly the cells may rarely exceed this num- 
ber, but the septa are frequently difficult to distinguish. Curved or twisted spore 
forms are common, and one end of the spore is usually wider and more rounded than 
the other. The species are very variable and difficult to determine or to differentiate 
in descriptions. 
The spore characters relate the present genus most intimately to Bilimbia, while 
Lecidea, with its simple spores, stands at the opposite end of the series of closely 
related forms, with Biatorella, Biatorina, and Bilimbia as intermediate forms. And 
the external resemblance is so close in all of these genera that one can not always be 
sure even of the genus until the spores are examined. 
A dozen species have been found in the State. On trees, and more rarely on rocks, 
' moss, or earth. 
Type species Bacidia rosella (Ach.) De Not. loc. cit. 
KEY TO THE SPECIES. 
Apothecia reddish brown to brown, never black............-- 2. B. rubella. 
Apothecia always or finally black. 
Apothecia always black, minute, flat or finally convex.... 8. B. akompsa. 
Apothecia becoming black. 
Apothecia at first reddish, 
Apothecia not flexuous, small, sessile, black....... 1. B. atrosanguinea. 
Apothecia often flexuous. 
Plants on trees; thallus of rather coarse 
greenish or brownish granules... ....-.--- Ll. B. chlorantha. 
Plants usually on mosses; thallus a minute 
sea-green or whitish crust .......---------- 9, B. muscorum. 
Apothecia at first lighter or darker brown. 
Apothecia at first pale brown. 
Apothecia small or minute; plants com- 
monly on rocks. 
Spores hamate or spirally twisted. . ....- 10. B. umbrina. 
Spores not hamate nor spirally twisted... 6. B. inundata. 
Apothecia middle-sized or larger; plants 
usually on trees. 
Apothecia often with pruinose exciple... 3. B. fuscorubella. 
Apothecia having the whole disk pru- 
INOSC.......2--- eee eee eee eee eee eee 3a. B. fuscoru bella 
suffusa. 
Apothecia at first dark brown or darker. 
Apothecia frequently flexuous. 
Apothecia middle-sized, sessile or ad- 
nate, flattish, dark brown or black.... 4. B. schweinitziv. 
Apothecia small or minute, commonly 
flat and adnate, black or blackish... . - 7. B. incompta. 
