262 28. COLLEMACEAE [105. Leptogium 



G. Spores 3-5-septate transversely, 



15-22 X 7-9 n 17. L. juniperinum 



F. Lobes narrow, irregularly to radiately arranged . 16. L. apalachense 

 E. Thalloid body larger, lobes more or less folded 

 F. Apothecia 1 or more mm. across 



G. Thalloid exciple thick and more or less folded 

 H. Apothecia sessile, exciple folded and 



waV y 19. L. phyllocarpum 



H. Apothecia sessile to subpedicellate, 



exciple becoming lobed 18. L. bullatum 



G. Thalloid exciple thin, usually entire and 



often disappearing 22. L. pulchellum 



F Apothecia rarely more than 1 mm. across 



G. Spores 16-22 X 7-9 m 20. L. crenatellum 



G. Spores 20-30 X 10-12 m 21. L. marginellum 



C. Spores usually more than 30 /x in length 



D. Thalloid margins entire to crenate or rarely toothed 

 E. Apothecia 0.2-0.5 mm. across 



F. Thalloid body wrinkled and pitted 



G. Margins toothed 23. L. palmatum 



G. Margins entire to subcrenate 26. L. scotinum 



F. Thalloid body more or less pustulate 25. L. platynum 



E.' Apothecia 0.4-0.8 mm. across 24. L. californicum 



D. Thalloid margins much jagged and fringed 



E. Lobes large, not densely crowded 27. L. lichenoides 



E. Lobes smaller, crowded, with finely fringed _ 



e( j ges 27. L. lichenoides pulvinatum 



1. Leptogium byssinum (Hoffm.) Zwackh.; Nyl, Act. Soc. Linn. Bord. 21:270. 



1856. . t . 



Lichen byssinus Hoffm., Enum. Lich. 46. pi. 4, f. 7. 1784. Pannana byssina 



(Hoffm.) Nyl. 



Transforming the algal colony into a small, thin, rough, minutely squamulose, 

 ashy gray to blackening body, the squamules coralloid and passing into very 

 minute, scurfy granules, the internal structure plectenchymatous throughout; apo- 

 thecia small to middle-sized, 0.4-1 mm. across, immersed to adnate, the disk con- 

 cave to flat, brownish to reddish brown, the algoid exciple thin, colored like the 

 thallus, finally disappearing; hypothecium hyaline to cloudy; spores ovoid-ellipsoid, 

 3-7-septate transversely and 1-2-septate longitudinally, 19-31 X 7-13.5 /a. 



On soil, Massachusetts, New Jersey, North Carolina, and Illinois. 



2. Leptogium plectenchymum Fink, Ohio Biol. Surv. Bull. 5:57, 58. pi. 4, f. 13 g. 



1915. 



Transforming the algal colony into a small to middle-sized, round to irregular, 

 loosely adnate, irregularly lobed, lead-colored body, the lobes ascending, often 

 imbricated with entire, irregular, or minutely lobulate margins, more or less of the 

 internal structure plectenchymatous; lighter colored and bearing rhizoids below; 

 apothecia small to middle-sized, 0.5-2 mm. across, sessile, scattered, the disk flat 

 to convex, reddish brown, the algoid exciple colored like the thallus, entire or 

 irregular; hypothecium hyaline to cloudy; spores ovoid-ellipsoid .to ellipsoid- 

 pointed, 3-septate transversely and becoming 1-septate longitudinally, 22-30 X 

 8-14 fi. 



On damp clay soil, near Oxford, Ohio. 



3. Leptogium tenuissimum (Dicks.) E. Fries, Corp. Fl. Prov. Suec. 1:293. 1835. 



Lichen tenuissimus Dicks., Plant. Crypt. Brit. 1 :12. pi. 2, f. 8. 1785. 



Transforming the algal colony into a minute, minutely squamulose, digitately 

 and unequally cut-lobed, greenish gray to greenish brown, crustlike body, with 

 ascendant margins; apothecia minute to small, 0.2-0.6 mm. across, subsessile, the 

 disk concave to finally flat, dull reddish to brown, the proper exciple thin, lighter 

 colored than the disk; hypothecium hyaline to cloudy; spores ovoid-ellipsoid, 3- 

 5-septate transversely and 1-2-septate longitudinally, 24-36 X 9-15 fi. 



