Ohio Biological Survey, Bull. 10, Vol. 11, No. 6 | Page 9

8 in each ascus.
Collected in Lake County. On exposed igneous rocks. The type specimen is deposited in the writer's herbarium, and a cotype may be found in the State Herbarium.
This species is a coarser plant than Buellia turgescens (Nyl.) Tuck., with much stronger, darker thallus and apothecia on the whole larger.

Rhizocarpon Ram. in Lam. & DC. Fl. Fr. ed. 3. 2: 365. 1805.
Thallus usually verrucose, areolate or subareolate, tending toward squamulose conditions, better developed than in other members of the family, scarcely ever showing granulate conditions, and never disappearing entirely; apothecia also larger than in the other genera, adnate to immersed, usually black, but rarely white-pruinose; hypothecium usually dark brown; hymenium pale to light brown; spores 4-celled to muriform, and pale to brown, various conditions of septation and coloration sometimes appearing in the same hymenium.
KEY TO THE SPECIES OF RHIZOCARPON
On bark 2. R. alboatrum On rocks. Spores smaller and 4-celled 1. R. vernicomoideum Spores larger and becoming muriform 3. R. petraeum
1. Rhizocarpon vernicomoideum sp. nov.
Thallus of minute, rounded, scattered or sometimes clustered, straw-colored granules, covering small areas, and usually resting on and limited wholly or in part by a black hypothallus; apothecia minute to small, 0.2 to 0.6 mm. in diameter, black, semi-immersed to adnate, at first flat with a thin somewhat raised exciple, becoming convex with the exciple finally covered; hypothecium brown; hymenium pale or tinged brown below and light brown above; paraphyses coherent, distinct or semi-distinct; asci clavate; spores brown, 4-celled, becoming slightly constricted at the septa, 15 to 18 mic. long and 5 to 7 mic. wide, 8 in each ascus.
Collected at Cantwell Cave in Hocking County. On shaded sandstone, intermingled with an ash-gray, crustose thallus, which appeared like a sterile Pertusaria. The type specimen is deposited in the writer's herbarium, and a cotype may be seen in the State Herbarium.
The plant resembles Buellia vernicoma Tuck.
2. Rhizocarpon alboatrum (Hoffm.) Th. Fr. Nov. Act. Reg. Soc. Sci. Ups. III. 3: 337. 1861.
Lichen alboater Hoffm. Lich. Icon. 30. 1784.
Thallus ash-gray varying toward white, commonly spread widely over the substratum as a continuous or rarely scattered or disappearing, smooth, chinky, verrucose-areolate, or sometimes mealy crust: apothecia small to middle-sized, 0.35 to 1 mm. in diameter, adnate or immersed, dull black and often more or less white-pruinose, flat with the black exciple visible, or convex when the exciple often becomes covered; hypothecium brown to black-brown; hymenium pale or tinged brown; paraphyses distinct, but sometimes coherent; asci clavate; spores oblong-ellipsoid, brown, 4-celled to muriform, 12 to 22 mic. long and 4 to 9 mic. wide (Fig. 8), 8 in each ascus.
Collected in Butler, Preble, Ross, and Highland counties. On bark, especially elm bark. Also reported from Ottawa County. Rare but doubtless distributed widely in the State.
3. Rhizocarpon petraeum (Wulf.) Koerb. Syst. Lich. 260. 1855.
Lichen petraeus Wulf. in Jacq. Coll. Bot. 3: 4. pl. 6. f. 2a. 1789.
Thallus an ash or green-gray crust, or varying toward brown or brown-black, smooth to more commonly roughened, chinky to areolate, continuous or scattered, of moderate thickness, often widely and irregularly disposed on the substratum; apothecia small to large, 0.5 to 1.3 mm. in diameter, immersed to adnate, black-brown to black, flat with the concolorous exciple visible, or becoming somewhat convex, with the exciple often covered; hypothecium dark brown; hymenium pale, or tinged brown, especially above; paraphyses coherent, semi-distinct; asci clavate or inflated-clavate; spores oblong-ellipsoid, 4-celled to muriform, hyaline to finally brown, 15 to 40 mic. long and 7 to 18 mic. wide. 8 in each ascus (Fig. 9).
Collected in Lake, Hocking, and Ross counties. Also examined from Summit, Vinton, and Ashtabula counties. On rocks. Rare but widely distributed in the State.

EXPLANATION OF PLATE XIII
Fig. 1. Five paraphyses of Rhizocarpon alboatrum to illustrate types of simple and branched forms found in the same hymenium. X 450.
Fig. 2. A section of the thallus of Bacidia rubella and two cells of the woody substratum: a, the upper densely interwoven portion of the thallus; b, part of the less densely interwoven portion below; c, the algal-host cells; d, one of the cells of the woody substratum and three hypal rhizoids within it. X 450.
Fig. 3. Spores of Lecidea enteroleuca to illustrate the simple, hyaline type. X 760.
Fig. 4. Spores of Biatorina chalybeia to illustrate the 2-celled, hyaline type. X 760.
Fig. 5. Spores of Bilimbia trachona to illustrate the several-celled, hyaline, fusiform or dactyloid type. X 760.
Fig. 6. Spores of Bacidia fuscorubella to illustrate the several-celled, hyaline, acicular type. X 760.
Fig. 7. Spores of Bacidia umbrina to illustrate the several-celled, hyaline, hamate or spirally twisted type. X 760.
Fig. 8. Spores of Rhizocarpon alboatrum to illustrate the several-celled to many-celled and muriform, hyaline to brown type. X 760.
Fig. 9. Spores of Rhizocarpon petraeum of the same type as those shown in the last figure, but larger, and usually composed of more cells.