100. Lichina] 27. LICHINACEAE 151 



27. LICHINACEAE 



Thallus crustose, foliose or fruticose, showing little or no differentiation, at- 

 tached to the substratum by a holdfast; apothecia immersed or superficial, 

 terminal or lateral, with a proper or thalloid exciple. 



The algal host is Rivularia, or Calothrix. 



A. Spores non-septate 100. Lichina 



A. Spores septate 99. Pterygium 



• 99. Pterygium Nyl., Bull. Soc. Bot. France 1:328. 1854. 



Thallus crustose to scaly or squamulose, granulose to coralloid, the margin 

 more or less lobed, showing poorly developed upper and lower cortices of longi- 

 tudinally extending, septate hyphae, and more or less distinct algal and medullary 

 layers between; apothecia minute to small, adnate to sessile, the disk flat to con- 

 vex, the exciple colored like the disk; hypothecium brownish; hymenium hyaline 

 or brownish above; paraphyses unbranched, septate; asci clavate; spores 8, hya- 

 line, ovoid to ellipsoid, 1-3-septate. 



The algal host is Calothrix. 



1. Pterygium Petersii Nyl., Mem. Soc. Sci. Nat. Cherb. 5:332. 1857. 



Pannaria Petersii (Nyl.) Tuck. Placynthium Petersii (Nyl.) Burnh. 



Thallus composed of minute to small, flat, clustered or scattered, radiately 

 lobed, greenish gray to brown or brownish black squamules, the central ones 

 often disappearing; apothecia minute to small, 0.2-0.4 mm. across, sessile, the 

 disk flat, black, the exciple thin, black, somewhat raised; hypothecium brownish; 

 spores ellipsoid, becoming 1 -septate, 12-20 X 4-6 /x. 



On rocks, New York, Alabama, Tennessee, Iowa, and Minnesota. 



100. Lichina C. A. Agardh, Spec. Alg. 1:104. 1821. 



Thallus minutely fruticose, more or less erect, composed of densely clustered, 

 slender branches, the cortex indistinctly plectenchymatous or of entangled hyphae, 

 or rarely absent, the algal layer more or less irregular, joining the cortex and the 

 central medullary tissue of thin-walled, septate, longitudinally extending hyphae; 

 apothecia minute to small, more or less immersed in the tips of the branches, 

 solitary or clustered, the disk closed to open, irregular, the exciple colored like 

 the thallus; hypothecium brownish; hymenium hyaline or brownish above; pa- 

 raphyses threadlike, sparingly branched; asci cylindrical; spores 8, hyaline, oblong, 

 non-septate. 



The algal host is Calothrix. 



A. Cortex poorly developed or absent 1. L. confinis Willeyi 



A. Cortex better developed 1. L. confinis 



1. Lichina confinis (Mull.) C. A. Agardh, Spec. Alg. 1:105. 1821. 



Lichen confinis Miill., Icon. PI. Danica 5:5. pi. 879, f. 121. 1782. 



Thallus moderately thick, composed of slender, erect, tapering, densely clus- 

 tered, dichotomously branched, greenish brown to black branches; apothecia 

 small, 0.3-0.5 mm. across, immersed in the enlarged tips of the branches, the 

 disk closed to slightly open, the exciple thick, prominent, colored like the thallus; 

 hypothecium brownish; asci cylindrical; spores ellipsoid, 22-29 X 11-15 /x, uni- 

 seriately arranged. 



On maritime rocks, Massachusetts. 



f. Willeyi Tuck., Syn. N. A. Lich. 1:133. 1882. 

 Thamnidium Willeyi Tuck., in Schwend., Agentyp. Flechtengon. 19. pi. 1, 



f. 4-10. 1869. 

 The cortex poorly developed or absent. 



On maritime rocks, near New Bedford. Massachusetts. The algal host is 

 unusual, apparently one of the Rivulariaceae with thin walls and no heterocysts. 



