38 
Ohio JJiologjcal Survey 
what smaller; cortex thickened from 2 to several layers of cells around 
and below the apothecia, the whole area below the apothecia sometimes 
being- plectenchymatous ; the occurrence of the ])lectenchymatous cortex 
varying greatly, this structure being in some specimens thickened only 
under the apothecia, while in others it is thickened from 2 to 8 or 9 
layers of cells around the apothecia, the thickening sometimes passing 
outward 500 mic. or more in all directions from each apothecium; rhizoids 
numerous under the apothecia; apothecia middle-sized or large, sessile, 
scattered, 0.5 to 3 mm. in diameter; disk flat or convex, red-brown, sur¬ 
rounded by an entire or irregular thalloid margin, which often becomes 
concolorous with the disk and resembles in appearance a true exciple; 
exciple plectenchymatous, slightly tinged with brown, often passing im¬ 
perceptibly into the thickened plectenchymatous cortex about the apothe¬ 
cium ; hypothecium usually composed wholly of interwoven hyphse, but 
sometimes in part plectenchymatous below, 45 to 115 mic. thick; hy- 
menium 150 to 170 mic. thick; paraphyses narrow, 1 to 1.5 mic. wide; 
spores ovoid-ellipsoid to ellipsoid-pointed, longitudinally 4-celled, becom¬ 
ing transversely 2-celled, 22 to 30 mic. long and 8 to 14 mic. wide. 
See Fig. 13. 
Collected three times near Oxford, by Bruce Fink. On damp clay. 
Mallotium Ach.; S. F. Gray, Nat. Arr. Brit. PI. i: 399. 1821. 
Transforming the algal-host colony into a middle-sized or large, 
foliose, lead-colored to black-green body, which has large, often more or 
less granulate, sometimes rugose lobes, in which the algal chains are 
commonly more numerous toward the upper surface of the colony; 
thallus of a mycelial medulla and a plectenchymatous cortex; medulla of 
hyaline, usually densely and variously disposed hyphae, which are some¬ 
what uniformly distributed, straight or curved, more or less branched 
monopodially; cortex of one layer of cells, except around and below the 
apothecia where there may be two or more layers of cells, not so well 
developed as in Lcptogimn, and sometimes difficult to demonstrate over 
certain areas of the thallus; rhizoids numerous and strong, appearing 
as a dense, light-colored nap, which usually covers the whole lower sur¬ 
face and forms the chief differential character of the genus; apothecia 
scattered; the disk usually brown and commonly surrounded by a thalloid 
margin; exciple and hypothecium wholly or largely of interwoven 
hyplue, but both or the latter may be at least partly plectenchymatous; 
hymenium pale below and light-brown above; paraphyses hyaline toward 
