28 LICHEN FLORA OF THE UNITED STATES 



H. Thallus greenish gray to ashy or darker; 



spores brown 44. Physciaceae 



G. Thallus small to middle-sized or larger, plainly 

 foliose 



H. Spores non-septate 39. Parmeliaceae 



H. Spores septate 31. Stictaceae 



F. Thallus plainly fruticose 40. Usneaceae 



E. Thallus crustose to squamulose 



F. Spores minute, many in each ascus . . . .36. Acarosporaceae 

 F. Spores usually 1-8 in each ascus, rarely more 

 G. Spores usually septate, with lenticular cells 



H. Spores hyaline 41. Caloplacaceae 



H. Spores brown 43. Buelliaceae 



G. Spores non-septate to septate with cubical or 

 rectangular cells 



H. Spores large, with thick wall .... 37. Pertusariaceae 

 H. Spores small to middle-sized or large, with 



thin wall 38. Lecanoraceae 



