186 32. PELTIGERACEAE [118. Peltigera 



covered with minute hyphae; apothecia small to more commonly middle-sized or 

 large, borne on the margins of the lobes, the disk reddish brown to brown, the 

 exciple colored like the thallus, becoming more or less irregular; hypothecium 

 hyaline to brown; hymenium hyaline or brownish above; paraphyses commonly 

 unbranched; asci clavate to cylindrico-clavate ; spores 8, rarely only 6, hyaline 

 to brownish, fusiform or acicular, frequently more or less curved, 3-7-septate. 

 The algal host is Nostoc or Dactylococcus. 



A. Without trichomatic hyphae, smooth above 



B. Bearing irregular cephalodia above 1. P. aphthosa 



B. Cephalodia absent 



C. Lobes small, fan-shaped to triangular 2. P. venosa 



C. Lobes larger, broad and irregular 



D. Spores 3-septate, 30-48 /x in length 



E. Margins smooth 3. P. horizontalis 



E. Margins isidioid 4. P. ZopiVi 



D. Spores 3-7-septate, 60-100 fi in length 5. P. polydactyl i 



A. With trichomatic hyphae or granulose above 



B. Thallus brownish to dark brown or black below 



C. Uniformly covered with a dense nap below 7. P. malacea 



C. More or less reticulated or veined below 



D. Margins crenate and smooth 8. P. rufescens 



D. Margins irregular, often isidioid-granulose to sorediate . . 6. P. scutata 

 B. Thallus white to brownish below 



C. Thallus powdery or bearing coralloid branchlets or masses of 

 soredia above 



D. Thallus powdery 13. P. pulverulenta 



D. Thallus bearing coralloid branchlets 9. P. praetextata 



D. Thallus bearing masses of soredia 12. P. sorediaia 



C. Thallus uniform above 



D. Thallus small to middle-sized 11. P. spuria 



D. Thallus middle-sized to large 



E. Rhizoids running together into a conspicuous 



spongy nap 10. P. canina spongiosa 



E. Rhizoids scattered or absent 

 F. Thallus thinner, expanded 



G. Trichomatic hyphae very prominent . 10. P. canina leucorrhiza 



G. Smooth or minutely pitted ... 10. P. canina membranacea 



F. Thallus thicker, less expanded 10. P. canina 



1. Peltigera aphthosa (L.) Willd., FI Berol. Prod. 347. 1787. 



Lichen aphthosus L., Sp. PI. 1148. 1753. P. aphthosa var. minor Tuck. 



Thallus middle-sized to large, smooth, somewhat closely attached, sprinkled 

 more or less with small, irregular cephalodia, greenish gray to green or brownish, 

 the lobes broad, round, sometimes more or less imbricated, strongly ascending at 

 least toward the margins; white to blackening below, reticulated with whitish to 

 blackened veins, bearing scattered, black rhizoids; apothecia middle-sized to large, 

 4-8.5 mm. across, borne on somewhat extended lobules, rolled backward, the disk 

 reddish brown, the exciple thin, colored like the thallus, becoming crenulate; 

 hypothecium brownish; spores hyaline to pale brownish, 3-7-septate, acicular, 

 45-75 X4-7/X. (Plate 13.) 



On soil and over humus-covered rocks, throughout northern United States, and 

 occasionally occurring farther southward. 



2. Peltigera venosa (L.) Baumg., Fl. Lips. 561. 1790. 

 Lichen ve?iosusL., Sp. PI. 1148. 1753. 



Thallus small, composed of scattered to rarely confluent, fan-shaped to trian- 

 gular, smooth, ascending, greenish gray to ashy or brownish, marginally wavy 

 lobes; whitish below, reticulated with coarse brownish black veins bearing small 

 rhizoids and often spreading together into a close nap; apothecia middle-sized, 

 2-5 mm. across, borne on the margins of the lobes, superficial, round to horizontal, 

 the disk flat, reddish to blackish brown, the exciple becoming crenate or finely 



