ichen 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