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.