142 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Thallus thin, suborbicular or irregular and frequently more or less scattered, rather 
small, 25 to 60 mm. in diameter, or the scattered lobes extending over larger areas, 
becoming densely isidioid-granulate, the lobes more or less imbricate and ascending 
with crisped, undulate, or lacerate margins, or the margins produced into isidioid 
lobules, the marginal lobes, in the more continuous forms, somewhat more expanded; 
lead-colored, varying toward greenish or olivaceous, scarcely differing in color below; 
rhizoids and attachment of thallus as in the last; algal chains not so distinctly more 
numerous toward the top, and medullary and algal layers rather less distinct than in 
any of the above species; apothecia small in ours, 0.5 to 1 mm. in diameter, sessile, 
the disk brown and flat, the margin thalloid in structure, granulate, irregular, or more 
rarely entire; hypothecium pale; hymenium pale below and brownish above; paraphy- 
ses simple or rarely branched, frequently thickened and brownish toward the apex; 
asci clavate; spores ovoid to ellipsoid-pointed, pale, becoming muriformly many- 
celled, 15 to 32 » long and 8 to 13 » wide. 
Collected at Taylors Falls and at Mankato. On sandstone. Perhaps most of ours 
should be referred to subspecies conchatum Tuck.a 
North American range scarcely differing from that of the last foregoing. Also 
quite as various in form as the last and known in some form in all of the grand divisions. 
5. Leptogium myochroum (Schrad.) Tuck. Gen. Lich. 99. 1872. 
Lichen myochrous Schrad. Journ. Bot. 1799!: 18. 1799. 
Thallus suborbicular, or irregular, somewhat closely attached to the substratum, 
small, and only slightly lobed or becoming larger and more lobed, 25 to 80 mm, in 
diameter, the lobes more or less ascending and imbricated, wide, rounded, subentire, 
undulate; lead-colored varying toward olivaceous or blackish, smooth or more or less 
rugose, somewhat granulate, clothed below with whitish rhizoids, composing a deli- 
cate nap; algal chains more numerous toward the top, a fairly well-developed medul- 
lary layer below, though containing scattered algal chains; apothecia middle-sized, 
1 to 2 mm. in diameter, subsessile, the disk flat and reddish brown, the margin thal- 
loid and more or less irregular and granulate; spores pale, ellipsoid, becoming some- 
what muriform, 23 to 30 ” long and 7 to 9 » wide. 
Ours sterile, and the spore and apothecial characters taken from Tuckerman. 
Frequently excluded from the present genus. 
Generally distributed over the State. On trees and rarely on rocks. 
The plant is generally distributed over North America. Known also in Europe. 
5a. Leptogium myochroum tomentosum (Hoffm.) Schaer. Lich. Helv. Spic. 
534. 1842. 
Collema tomentosum Hoffm. Deutsch. Fl. 2: 99. 1795. 
Thinner, darker, usually narrower-lobed, more imbricated and having sinuate 
margins, velvety below. 
The lobes tend to be normal in ours, however, and perhaps our plants should not 
be referred to the subspecies. 
Collected on Carlton Peak and along the international boundary from Harding to 
Warroad. On trees. 
Elsewhere in North America known only in the Rocky Mountains and Alaska. 
Known also in Europe 
Family PYRENOPSIDACEAE. 
This family is a small one, represented in our flora by only two genera and a few 
species. The thallus is crustose or foliose, or may even exhibit a fruticose tendency 
as in the Omphalarias. A cellular cortex is present in Pyrenopsis, but not in Ompha- 
aSyn. N. A. Lich. 1: 163. 1881. 
