144 25. EPHEBACEAE [ 90. Leptogidium 



90. Leptogidium Nyl., Flora 56:195. 1873. 



Transforming the algal colony into a minute to small, slender, densely branched 

 body, the branches showing a thin cortex of many, thin-walled, septate, longitudi- 

 nally extending hyphae, and a poorly developed, central cylinder of more or less 

 septate, longitudinally extending medullary hyphae, surrounded by the algal layer; 

 apothecia minute to small, terminal, adnate to sessile, the disk flat to convex, 

 the exciple colored like the thallus or lighter; hypothecium hyaline; hymenium hya- 

 line or brownish above; paraphyses more or less coherent, unbranched, septate; 

 asci clavate; spores 8, hyaline, oblong-ellipsoid to fusiform, non-septate. 



The algal host is Scytonema. 



1. Leptogidium dendriscum Nyl., Flora 56:195. 1873. 



Leptogium dendriscum Nyl., Syn. Lich. 1:135. 1858. L.byssoides (Carr.) 

 Zahlbr. 



Transforming the algal colony into a minute, slender, dichotomously much- 

 branched, pale green body, the branches very slender, cylindrical or obscurely 

 flattened and interwoven; apothecia minute, 0.25-0.35 mm. across, adnate, the disk 

 flat to slightly convex, pale to brownish red, the proper exciple thin, lighter colored 

 than the disk; spores ellipsoid, 10-16 X 6-8 /x. 



On trees, Florida. 



91. Polychidium Mass.. Mem. Lich. 88. 1853. 



Transforming the algal colony into a small to middle-sized, irregularly lobed, 

 smooth to rough, rarely ciliate body, plectenchymatous throughout or showing 

 plectenchymatous upper and lower cortices with indistinct algal and medullary 

 layers; apothecia minute to small or middle-sized, scattered or terminal, adnate to 

 sessile,, the disk flat to more or less convex, the exciple thin, colored like the disk 

 or lighter, often disappearing; hypothecium hyaline to yellowish; hymenium 

 hyaline; paraphyses unbranched; asci clavate; spores 8, hyaline, oblong-ellipsoid 

 to ellipsoid or fusiform, 1 -septate. 



The algal host is Scytonema. 



A. Thalloid body small, not bearing marginal cilia 



B. Thalloid body irregularly much-branched, greenish brown 



to olive-black 1. P. muscicola 



B. Thalloid body minutely lobed, greenish to lead-colored . . . . 2. P. rivale 

 A. Thalloid body rather large, bearing minute whitish 



marginal cilia 3. P. albociliatum 



1. Polychidium muscicola (Swartz) S. F. Gray, Nat. Arr. Brit. PI. 1:402. 1821. 

 Lichen muscicola Swartz, Nov. Act. Acad. Upsal. 4:248. 1784. Leptogium mus- 

 cicola (Swartz) E. Fries. 



Transforming the algal colony into a small, irregularly much-branched, greenish 

 brown to olive-green body, the branches densely interwoven and more or less 

 longitudinally striate; apothecia small to middle-sized, 0.3-0.8 mm. across, adnate 

 to sessile, round to irregular, the disk flat to slightly convex, reddish brown, the 

 proper exciple thin, lighter than the disk, rarely disappearing; spores oblong- 

 ellipsoid to ellipsoid, 18-28 X 5-8 /x. 



On soil and mossy rocks, New Hampshire, Vermont, Alabama, California, 

 Idaho, and Washington. 



2. Polychidium rivale (Tuck.) Fink n. comb. 



Leptogium rivale Tuck., Proc. Am. Acad. 12:170, 171. 1877. 



Transforming the algal colony into a minutely and tufted-lobed, greenish to 

 lead-colored body, the lobes crowded, imbricated, narrow, and flexuous; apothecia 

 minute, 0.15-0.25 mm. across, immersed and indicated by an ostiole; hypothecium 

 hyaline; spores oblong-ellipsoid, 16-23 X 5-8 /x. 



On pebbles, in a brook, California, growing with and on Hydrothyria. 



