Thallus foliose, with plectenchymatous cortex above (Fig. 5), or both above and below (Fig. 2), with medulla of loosely interwoven hyphae, trichomatic hyphae, usually present, attached to the substratum by compound rhizoids; apothecia of considerable size, commonly on extended lobes, usually imbedded in the tissues on the upper side, or more rarely on the lower side; exciple inconspicuous; hypothecium usually light or darker brown; hymenium usually pale below and brown or tinged brown above; paraphyses simple or branched, distinct, seldom gelatinized or coherent; spores hyaline or brown, 4- to several-celled, elongated.

KEY TO THE GENERA

Peltigera Willd. Fl. Berol. Prodr. 347. 1787.

Thallus foliose, usually adnate toward the center, with the lobes more or less ascending at the margins, green-gray varying toward brown, the upper surface sometimes bare, or again clothed with trichomatic hyphae, giving it a downy appearance, or bearing cephalodia or isidioid branchlets, the lower surface usually conspicuously veined, with tufted rhizoids descending from the veins, color of these light or dark; cross section showing two distinct layers, the upper plectenchymatous cortex composed of 2 to 4 layers of meshes, and the medulla, composed of densely interwoven and irregularly disposed hyphae; lower cortex lacking, but the hyphae of the lower portion in some instances more or less horizontally arranged and produced into hyphal rhizoids, thus serving for support and protection much like a true plectenchymatous cortex; apothecia usually orbicular, frequently revolute, imbedded in the upper surface of the lobes; exciple plectenchymatous (Fig. 4); hypothecium of interwoven hyphae, usually tinged brown; hymenium commonly pale below and brown above; paraphyses usually simple, but some branched ones present in all of the species, hyaline in the main, but usually enlarged and tinged brown at the apex; asci usually cylindrico-clavate; spores hyaline, fusiform to acicular, sometimes curved, 4 to 8-celled, 8 arranged parallel in the asci.

The algal host cells lie in the medulla, just below the upper cortex.

KEY TO THE SPECIES OF PELTIGERA

1. Peltigera aphthosa (L.) Willd. Fl. Berol. Prodr. 347. 1787.

Lichen aphthosus L. Sp. Pl. 1148. 1753.

Thallus closely attached to the substratum at the center, the lobes ascending, 6 to 8 cm. in diameter, smooth and devoid of trichomatic hyphae above, cephalodia more or less rounded and irregularly scattered over the surface (Fig. 3), the lobes broad and rounded with crenate margins, brown above, the lower surface having numerous veins, these forming a dark brown nap at the center, the veins distinct and light toward the margin, dark rhizoids extending from the veins; medulla composed of thick-walled, densely interwoven hyphae, irregularly disposed; apothecia on extended lobules, orbicular and frequently revolute, the disk red-brown, 2 to 5 mm. in diameter, the margin entire or crenulate; hypothecium pale brown; hymenium hyaline to pale brown above; asci cylindrico-clavate; spores acicular, straight, 4- to 6-celled, 47 to 66 mic. long and 4 to 5 mic. wide (Fig. 8, d).

Examined from Clark County. Also reported from Champaign County. On earth and often on humus-covered rocks. Rare in Ohio.

2. Peltigera praetextata (Sommerf.) Fink. Proc. Ind. Acad. Sci. 1918: 267. 1918.

Peltigera ulorrhiza praetextata Sommerf. Lapp. Suppl. 123. 1826.

Thallus adnate toward the center, more or less ascending toward the margins, 7 to 15 cm. in diameter, the upper surface having isidioid branchlets or lobules scattered more or less thickly, the lobes broad, wavy, crenate, with frequently isidioid, lobulate margins, trichomatic hyphae often present, usually green-gray toward the center, becoming brown toward the margin, the lower surface light with numerous dark veins and bearing rhizoids of the same color, the veins and rhizoids becoming light colored toward the margin; medulla of densely interwoven and irregularly disposed hyphae; apothecia on narrow, somewhat extended lobes, the disk brown to brown-black, revolute, 2 to 5 mm. in diameter, hypothecium light to darker brown; hymenium pale below and brown above; asci cylindrico-clavate; spores sub-fusiform to acicular, usually straight but sometimes slightly curved, 4- to 6-celled, 42 to 56 mic. long and 3 to 5 mic. wide.

Examined from Franklin, Adams, Butler, Marion, Jefferson, and Preble counties. On soil, old logs, and moss in woods. Not previously reported from Ohio, but included under Peltigera canina and Peltigera rufescens. Evidently widely distributed and frequent in the State, but seldom fruited.

3. Peltigera sorediata (Schaer.) Fink comb. nov.

Peltigera canina spuria sorediata Schaer. Enum. Lich. Eur. 21. 1850.

Thallus small, composed of scattered lobes, these 1 to 4.5 cm. in length, adnate with slightly ascending rounded, and crenate margins, the upper surface usually deep gray at the center, becoming lighter toward the margin, thickly covered with trichomatic hyphae, orbicular sorediate areas scattered over the upper surface, the lower surface ash-white to cream-colored, with a network of veins of the same color, with similarly colored rhizoids extending downward; medulla of small, densely interwoven and irregularly extending hyphae; apothecia somewhat digitately clustered on the narrow lobes, small, 1.3 to 3 mm. in diameter, orbicular, flat or semi-revolute, dark brown; hypothecium light brown; hymenium hyaline below and brown above; asci long-clavate; spores acicular, 6- to 8-celled, 53 to 66 mic. long and 3 to 3.5 mic. wide (Fig. 8, b).

Examined from Butler and Lake counties. On damp earth and mossy rocks. Not previously reported from Ohio, and probably not widely distributed in the State. Surely rare.

4. Peltigera canina (L.) Hoffm. Deutsch. Fl. 2: 108. 1795.

Lichen caninus L. Sp. Pl. 1149. 1753.

Thallus closely adnate toward center, the lobes more or less ascending, 6 to 15 cm. in diameter, the upper surface for the most part thickly covered with trichomatic hyphae, generally giving it a downy appearance under the lens, the lobes numerous and usually broad and rounded, with entire or crenate and much crisped margins, usually green-gray but sometimes becoming brown, below almost white, netted with light brown or gray veins, these bearing rhizoids of the same color; medulla (Fig. 5) of densely interwoven and irregularly disposed hyphae; apothecia on narrow, extended lobes, often erect, orbicular, usually revolute, 2 to 7 mm. in diameter, the disk dark brown; hypothecium (Fig. 7) pale brown; hymenium (Fig. 6) pale below and brown above; asci long-clavate; spores acicular, straight or sometimes curved, 4- to 8-celled, 30 to 65 mic. long and 3 to 5 mic. wide (Fig. 8, d).

Examined from Butler, Franklin, Ashtabula, Green, Seneca, Summit, Lorain, Preble, Brown, and Adams counties. On soil or mosses in woods. Generally distributed and frequent in Ohio.

5. Peltigera rufescens (Neck.) Hoffm. Deutsch. Fl. 2: 107. 1795.

Lichen rufescens Neck. Meth. Musc. 79. 1771.

Thallus closely adnate at the center with ascending lobes, 5 to 15 cm. in diameter, the upper surface smooth and devoid of trichomatic hyphae for the most part, but the margins sometimes sparingly covered with them, green-gray to brown, the lobes crowded, rather small with crenate, much crisped, elevated margins, the lower surface usually becoming dark brown except at the margins, and thickly reticulated with brown veins, from these numerous rhizoids of similar color extending; medulla of densely interwoven variously disposed hyphae; apothecia numerous on narrow, extending lobes, the disk brown to black-brown, revolute, 4 to 7 mm. in diameter; hypothecium pale brown; hymenium hyaline to pale brown below and dark brown above; asci long-clavate; spores acicular, straight or curved, 4- to 8-celled, 45 to 68 mic. long and 3.5 to 5 mic. wide.

Examined from Butler, Preble, Clark, Adams, and Summit counties. Also reported from Champaign County. On earth and mosses, commonly about trees. Widely distributed in Ohio, but infrequent.

6. Peltigera polydactyla (Neck.) Hoffm. Deutsch. Fl. 2: 106. 1795.

Lichen polydactylon Neck. Musc. 85. 1771.

Thallus adnate at the center with ascendant margins of the lobes, 6 to 11 cm. in diameter, the upper surface smooth and shining, devoid of trichomatic hyphae, the lobes broad with crisped, crenate margins, except those bearing the apothecia, these much narrower and more elongated and usually digitately clustered, brown in color for the most part, the lower surface showing through a reticulation of dark veins as small light-colored spots, numerous dark rhizoids extending downward from the veins; medulla of densely interwoven and irregularly disposed hyphae; apothecia orbicular, and usually revolute, the disk dark brown, 3 to 10 mm. in diameter; hypothecium pale brown; hymenium pale below and dark brown above; asci clavate to cylindrico-clavate; spores acicular, straight or slightly curved, 4- to 6-celled, 42 to 70 mic. long and 3 to 4 mic. wide.

Examined from Clark, Fairfield, and Morgan counties. On earth. Rare in Ohio.

7. Peltigera horizontalis (L.) Hoffm. Deutsch. Fl. 2: 107. 1795.

Lichen horizontalis L. Mant. Pl. 2: 132. 1771.

Thallus mostly adnate, the margins scarcely ascending, 6 to 20 cm. in diameter, the upper surface smooth and shining, devoid of trichomatic hyphae, green-gray to brown, the lobes broad and rounded with entire or crenate margins, the lower surface covered with numerous veins, these giving a dark coloration toward the center and becoming light colored toward the margins, numerous dark rhizoids extending down from the veins; medulla of thick-walled, densely and irregularly disposed hyphae; apothecia on somewhat narrowed lobes, transversely oblong or infrequently orbicular, the disk red-brown, concave, 2 to 4 mm. in diameter; hypothecium light brown; hymenium pale below and dark brown toward the upper surface; asci cylindrico-clavate; spores fusiform to long-ellipsoid, straight to curved, 4-celled, 26 to 40 mic. long and 5 to 6.5 mic. wide. (Fig. 8 a).

Examined from Lake and Fairfield counties. On earth and mossy rocks. Rare in Ohio.

Nephroma Ach. Lich. Univ. 101. 521. pl. 11. f. 1. 1810.

Thallus foliose, but smaller and thinner than that of Peltigera, and devoid of trichomatic hyphae, more or less closely attached to the substratum by rhizoids; cortex well developed on both upper and lower sides; medulla well developed (Fig. 2); apothecia confined to the lower side of the thallus, marginal on narrow, slightly elongated lobes, thalloid margin persistent and crenate; hypothecium usually some shade of brown; hymenium usually pale below and brown above; paraphyses simple or branched; spores brown, 4-celled, 8 in each ascus.

The algal-host cells occur as in Peltigera.

1. Nephroma helvetica Ach. Lich. Univ. 523. 1810.

Thallus adnate, rather closely attached to the substratum by numerous short, hyaline, thick-walled rhizoids, irregular or sometimes orbicular in form, 6 to 10 cm. in diameter, green-gray to brown above, smooth or bearing tooth-like branchlets, narrowly and laciniately lobed, the margins of the lobes serrate or crenate, slightly ascending, beneath finally tomentose, and brown or black-brown; plectenchymatous cortices well developed above and below; medulla of narrow, thin-walled, densely, variously disposed hyphae; apothecia numerous, the disk red-brown to almost black, 1.3 to 3 mm. in diameter; hypothecium of interwoven hyphae, pale brown; hymenium pale brown below and darker above; asci clavate; paraphyses simple or branched, slightly swollen and brown at the apex; spores brown, ellipsoid, 4-celled, 15 to 21 mic. long and 5.5 to 8 mic. wide.

Examined from Butler and Champaign Counties. On trunks and mossy rocks. Rare and usually sterile in Ohio.

EXPLANATION OF PLATE XIV

Fig. 1. A section through the thallus of Peltigera canina, showing the cortex above and the medulla below, the medullary hyphae of the lower portion running in a somewhat horizontal direction. The algal cells shaded. X 380.

Fig. 2. A section through the thallus of Nephroma helvetica, showing the cortices, upper and lower, and the mycelial medulla within. The algal cell shaded. X 760.

Fig. 3. A section through a cephalodium of Peltigera aphthosa; a, the surrounding cortex; b, the internal hyphae and the cells of the algal host; c, the supporting hyphae from the thallus below. Partly diagramatic. X 48.

Fig. 4. A small portion of a section through the exciple of Peltigera canina, showing the plectenchymatous structure. X 380.