GEOLOGY OF LA SALLE COUNTY. 



145 



O. atra, Pers., Nyl. Thallus thin or wanting-, 

 apothecia sessile, black, simple, flexuose, disk 

 open, canaliculate, proper marg^in thick, elevated 

 wavy. Throug'hout our territory on oaks, hick- 

 ories, cherries, etc. 



O. varia, Pers., Pr. Thallus white, pulverulent, 

 apothecia prominent, elong-ate, oblong-, elliptical, 

 attenuate at the ends, brownish-black, dilated in 

 the centre, margin inflexed. On various trees. 

 GRAPHIS, Ach., Nyl. Thallus crustaceous, uni- 

 form, apothecia mostly lirellaeform, and branch- 

 ing-, but in some species rounded, difform, the 

 proper exciple colored or black. Differentiated 

 from Opeg-rapha by the spores. 



G. scripta, L., Ach. Thallus thin, whitish, even 

 or rug-ose, sub-tartareous, apothecia immersed 

 or half immersed, slender, width uniform, sim- 

 ple or branched, obtuse at ends, proper margfin 

 narrow, wavy, thalloidal margfin tumid. Spores 

 colorless. Common everyw^here on oaks, hicko- 

 ries and other trees; apothecia variously 

 branched. 



G. dendritica, Ach. Thallus white or yellowdsh, 

 thin, pulverulent, apothecia brownish black, 

 immersed, broad, flexuose-branched, forked, disk 

 broad, often caesio-pruinose, marg-in thin. On 

 oaks and various trees within our limits. These 

 two species seem to be the only ones of this 

 g-enus in Northern Illinois. One other can be 

 added for the southern portion of the State. 



GLYPHIDEI. 



ARTHONIA, Ach., Nyl. This g-enus, containing- a 

 g-reat number of species mostly tropical, is one 

 of the most perplexing-. We have several spe- 



