80 



14. ARTHONIACEAE 



[ 47. Arthonia 



H. Spores 16-22 fi in length 19. A. polygramma 



G. Apothecia round to irregular 

 H. Spore cells equal 



I. Apothecia 0.1-0.3 mm. across ... 28. A. chiodectella 

 I. Apothecia 0.2-0.9 mm. across . . . . 29. A. impolita 

 H. Spore cells unequal 



I. Apothecia often elongated 30. A. byssacea 



I. Apothecia not elongated . . . 33. A. Tuckermaniana 

 E. Spores constantly 3-septate 

 F. Disk not pruinose 



G. Apothecia round to irregular or elongated 



H. Thallus often intersected by black lines . IS. A. viridicans 

 H. Thallus not intersected by black lines 



I. Spores 12-17 X 4.5-6 n 20. A. varia 



I. Spores 9-13 X 3-5 /i 27. A. albofuscescens 



G. Apothecia round to irregular or elongated 



H. Thallus smooth, greenish gray . . . . 21. A.erubescens 

 H. Thallus smooth to powdery, ashy white 



I. Apothecia 0.09-0.3 mm. across . . i2. A. cinereopruinosa 

 I. Apothecia 0.3-0.6 mm. across . . . . 34. A. Eckfeldtii 

 F. Disk more or less pruinose 



G. Spores more than 16 fi in length 



H. Thallus becoming chinky and subareolate . 25. A. lecideella 

 H. Thallus often bearing mealy soredia . . 31. A. glaucescens 

 G. Spores less than 16 /x in length 



H. Apothecia round to slightly irregular . . 26. A. cupressina 

 H. Apothecia oblong to elongated .... 35. A. leucastraea 

 A. Apothecia black 



B. Spores 1- or rarely 2 -septate 

 C. On rocks and soil 



D. Thallus squamulose 36. A. glebosa 



D. Thallus crustose 



E. Spores with cells equal 



F. Apothecia 0.1-0.3 mm. across 37. A. lapidicola 



F. Apothecia 0.06-0.08 mm. across 38. A. terrigena 



E. Spores with one cell larger 39. A. rupicola 



C. On trees and old wood 



D. Apothecia round to irregular but rarely elongated 

 E. Disk commonly pruinose 



F. Apothecia 0.15-0.5 mm. across ... 40. A. patellulata caesiocarpa 



F. Apothecia 0.1-0.15 mm. across 44. A. pruinosella 



E. Disk not pruinose 



F. Spores with cells equal 



G. Disk flat to convex, smooth 40. A. patellulata 



G. Disk strongly convex and irregular or rough 



H. Thallus smooth to powdery 45. A. aleuromela 



H. Thallus smooth to chinky 42. A. convexella 



F. Spores with one cell larger 



G. Thallus dark gray, inconspicuous 43. A. exilis 



G. Thallus dull white or ashy white 



H. Spores 1-septate, 8-11 X 3-4.5 /j. .... 50. A.dispersula 

 H. Spores 1- or 2-septate, 10-13 X 3-4 /j. ... 48. A. Willeyi 

 D. Apothecia round to irregular and more or less elongated 

 E. Spores 1-septate 



F. Spores with one cell larger 



G. Spores 9-12 X 4^5 /* 41. A. subdispuncta 



G. Spores 7-9 X 2.5-3 fi 52. A. subminutissima 



F. Spores with cells equal 



G. Spores 19-26 X 7.5-9 fi 51. A. taedescens 



G. Spores 11-16X4-5/* . 47. A. dispersa 



E. Spores 1-2 -septate 



F. Apothecia more or less branched . . . 53. A. microspermella 

 F. Apothecia not branched 46. A. Rhoidis 



