FINK—-THE LICHENS OF MINNESOTA. 239 
Type species Pyrenula verrucosa Ach, loc. cit. But this plant is a Verrucaria, 
therefore the generic name Pyrenula is invalid. 
KEY TO THE SPECIES, 
Spores 2-celled. 
Apothecia usually depressed, completely immersed and 
indicated at the surface by rounded or oblong black 
spots. 
Apothecia always depressed and completely im- 
mersed; spores 12 to 18” long.....-------------- 4. P. thelena. 
Apothecia not always depressed and completely 
immersed; spores 10 to 18» long........-------- 1. P. cinerella. 
Apothecia partly immersed; spores 14 to 23 long... -- 2. P. nitida 
Spores more than 2-celled. 
Spores 4 to 8-celled, 14 to 30” long.......--------+-+-- 3a. P. leucoplaca pluri- 
loculata. 
Spores never more than 4-celled. 
Spores 3 to 4-celled, 10 to 18 » long; apothecia mi- 
nute or small, often depressed........-.-------- la. P. cinerella quadri- 
loculata. 
Spores 4-celled, 14 to 24 » long; apothecia globose 
or depressed-globose, minute......---------++---- 3. P. leucoplaca, 
1. Pyrenula cinerella (Flot.) Fink. 
Verrucaria cinerella Flot. in Zwackh, Exsice. no, 217. 1863. 
Thallus hypophloeodal and widely-spread when occurring on birch, but frequently 
on other barks, there more conspicuous, ashy; apothecia completely or partly immersed, 
minute, 0.1 to 0.3 mm. in diameter, or on birch often showing the oblong form, not 
always depressed, the perithecium dark brown in section and sometimes complete, 
the amphithecium pale or yellowish; paraphyses distinct, simple or branched and 
sometimes slightly enlarged and colored toward the apex; asci clavate or cylindrico- 
clavate; spores 2-celled, oblong-ellipsoid, 10 to 18 4 long and 5 to 9 wide. 
Throughout the northern portion of the State. On trees. 
Elsewhere in North America in Florida, lowa, Nebraska, and Ontario. Known 
also in Europe and South America. 
la. Pyrenula cinerella quadriloculata Fink, Minn. Bot. Stud. 2: 276. 1899. 
Thallus as above; spores perhaps smaller, passing from 2 to 3 and 4-celled condi- 
tions; apothecia also minute or small. 
A. Zahlbruckner regards the subspecies to be Polyblastia fallaciosa Arn.4 
Common in the northern portion of the State, and once collected as far south as 
Mankato, On birch. The plant reported from Mankato as Pyrenula glabrata does 
not show the spore characters distinctly in the herbarium specimen and is quite 
likely to prove to be a form of the present species. 
Not known elsewhere, unless Arnold’s plant is the same. 
2. Pyrenula nitida (Weig.) Ach. Ges. Naturf. Freund. Mag. 6: 211. 1812. 
Sphaeria nitida Weig. Observ. Bot, 4: 49. 1772. Fiacure 17. 
-Thallus hypophlceodal, but always apparent at the surlace and showing an ashy 
and often more or less shining surface, smooth and often varying toward olivaceous, 
forming more or less rounded areas upon the substratum or more widely spread and 
irregular; apothecia semi-immersed, middle-sized, 0.2 to 0.6 mm, in diameter, glo- 
bose, scattered or in clusters of two or three, the perithecium brownish black in 
@ Flora 604. 1858. 
