KEY TO THE FAMILIES AND IMPOETANT GENERA 245 



Apothecia small, laterally compressed, with a narrow, elongated opening; dark- 

 colored and hard. Mostly bark- and wood-inhabiting. 



Order Hysteriales 

 Apothecia with no definite limiting border, the asci forming a hymenium with- 

 out paraphyses, usually with very limited hypothecial tissues. 



Order Taphrinales 



Key to the Families and Important Genera of Apothecial Lichens Occurring in 



the United States (Lecanorales) 



{Based on Fink and Hedrick, 1935) 



Asci disintegrating and the spores forming a powdery coat (mazaedium) on the 



surface of the hymenium. 

 Thallus crustose, without cortex. On trees or decorticated wood. 

 Apothecia borne on stipes. Family Caliciaceae 



Ascospores one septate; not parasitic on other lichens. Calicium 

 Ascospores not septate, not parasitic on other lichens. Chaenotheca 

 (Besides the foregoing, five other small genera, two parasitic on other 

 lichens.) 

 Apothecia not borne on stipes. Family Cypheliaceae 



Ascospores one septate. Cyphelium 



(Besides the foregoing two other small genera.) 

 Thallus foliose or bushy, with cortex. Family Sphaerophoraceae 



One genus in the U.S., mainly on soil or rocks, Sphaerophorus 



Asci persistent; no mazaedium. 



Apothecia irregular, linear or oblong. 



Thallus crustose, well-developed "proper exciple" lacking. 



Family Arthoniaceae 

 Ascospores transversely one to several septate. Arthonia 



Ascospores both transversely and longitudinally septate. 



Arthothelium 

 Thallus crustose, "proper exciple" present. 



Apothecia not seated in a stroma. Family Graphidaceae 



Ascospores hyaline or at most light brown. 



Ascospores not septate; on old wood. Xylographa 



Ascospores septate, paraphyses not branched. 



Cells of ascospores cylindrical or cubical. Melaspilea 



Cells of ascospores lenticular. 



Ascospores only transversely septate. Ghraphis 



Ascospores both transversely and longitudinally septate. 



Graphina 

 Ascospores septate, paraphyses branched and interwoven. 



Cells of ascospores cylindrical or cubical. Not longitudinally septate. 



Opegrapha 

 Ascospores both transversely and longitudinally septate. 



Helminthocarpon 

 Ascospores brown. 



Transversely septate. Phaeographis 



Transversely and longitudinally septate. Phaeographina 



Apothecia seated in a stroma. Family Chiodectonaceae 



Six genera in the U.S. 



