38. Mycocalicium ] 11. CALICIACEAE 71 



7. Calicium populneum De Brond., in Duby., Bot. Gall. 2:638. 1830. 



Thallus grayish white, very thin, smooth, or obscurely scaly, often disappear- 

 ing; stipe very short and slender, blackish; apothecia minute, 0.1-0.2 mm. across, 

 subcylindrical to top-shaped, the disk convex to flat, black, the exciple black; 

 spores 11-14 X 5-7 /*, showing a very obscure septum at maturity. 



On trees, Illinois and California. 



8. Calicium pusillum (Ach.) Floerke, Deutsch. Lich. part 10.6. 1821. 



Thallus evanescent, often showing as a whitish coloration on the substratum; 

 stipes slender, of medium length, black; apothecia minute, 0.1-0.2 mm. across, 

 subspherical to top-shaped, the disk convex, brownish black, the exciple usually 

 darker; hypothecium brown; asci cylindrical; spores ellipsoid, 6-10 X 3-5 ^t. 



On decorticate trees, New York, Minnesota, and California. The algal host is 

 rarely seen, and in this respect the plant resembles species of Mycocalicium. 



9. Calicium roscidum Floerke, Deutsch. Lich. part 3.3. 1821. 



Thallus greenish gray, very thin, often scarcely visible; stipes rather short, 

 black; apothecia small to middle-sized, 0.2-0.4 mm. across, lens-shaped, the disk 

 convex, black, the exciple powdery and yellowish green above or throughout; 

 spores brown to blackish, 9-18 X 4-8 /x. 



On old wood, Massachusetts, New Hampshire, and Illinois. 



var. trabinellum (Ach.) Schaer., Nat. Anz. All. Sch. Gesell. Nat. 5:36. 1821. 



C.xylonellum var. trabinellum Ach., Meth. Lich. 91. 1803. C . trabinellum Ach. 



Thallus ashy, whitish, thin, smooth to granulose, often disappearing; stipes of 

 medium length and stoutness, brownish black, or at first partly bluish green pru- 

 inose; apothecia minute to small, 0.2-0.4 mm. across, globose to top-shaped, the 

 disk flat to convex, brown or obscurely whitish pruinose, the exciple at first bluish 

 green, becoming dark brown; hypothecium dark brown; asci cylindrical; spores 

 oblong-ellipsoid, 8-12 X 2.5-4.5 tt, uniseriate. 



On old wood, Massachusetts and Minnesota. The synonymy of this lichen is 

 uncertain. 



38. Mycocalicium Vainio, Etud. Lich. Bres. 2:182. 1890. 



Thallus usually inconspicuous and often within the substratum; stipes well 

 developed; apothecia borne on stipes, the disk commonly blackish, the exciple 

 colored like the disk; paraphyses disappearing; asci cylindrical; spores 8, non- 

 septate, ovoid to ellipsoid, uniseriate. 



The algal host is Cystococcus, rarely seen. 



Calicium polyporeum Nyl., Flora 58:7. 1875, is closely related but without algal 

 host; hence not a lichen. 



A. Spores 6-8 X 2.5-3.5 ^ 2. M. albonigrum 



A. Spores rarely less than 8 m in length 



B. Spores oblong or oblong-ellipsoid to ellipsoid 

 C. Thallus greenish to greenish gray 



D. Apothecia 0.15-0.25 mm. across 6. M. disseminatum 



D. Apothecia 0.3-0.5 mm. across 4. M. Ravenelii 



C. Thallus whitish or inconspicuous 



D. Spores 6-11 X 3-6 fi 1. M. parietinum 



D. Spores 9-15 X 4-7 ai 3. M. fuscipes 



B. Spores subspherical to ovoid-ellipsoid 5. M. microcephalum 



1. Mycocalicium parietinum (Ach.) Vainio, Etud. Lich. Bres. 2:182. 1890. 



Calicium parietinum Ach., Vet. Akad. Handl. 260. pi. 8, i.l.a-b. 1816. Cali- 

 cium subtile Pers. 



Thallus very thin, indicated by whitish patches of substratum, usually eva- 

 nescent; stipes rather short and slender, brownish black; apothecia minute to small, 

 0.1-0.35 mm. across, top-shaped to lenticular, the disk convex, blackish brown, the 

 exciple usually darker; spores oblong-ellipsoid, 6-11 X 3-6 /jl. 



On wood, throughout the United States, rarely parasitic on other lichens. 



