130 



GEOLOGY OF LA SALLE COUNTY. 



the most common species of the o'enus, occurs 

 everywhere on oaks, hickories and other trees. 



P. tribacia, Ach., Tuckerm. Thallus smallish, 

 membranaceous, sub-stellate, g-laucescent, be- 

 neath white, fibrillose, lobes short, appressed, 

 margins erose, granulate, apothecia small, ses- 

 sile, black or pruinose, margin sub-entire. Le- 

 canora, Ach. On hickory and oak. Common. 



P. obscura, Ehrh., Nyl. Thallus stellate, orbicu- 

 lar, appressed, epruinose, glaucous, fuscescent, 

 benealli black, fibrillose, lobes many-cleft, flat- 

 ish, ciliate, apothecia rather small, disk nigro- 

 fuscous, margin entire. Spores bilocular. On 

 trees, basswood, etc., and on moss}^ rocks. Bai- 

 ley's Falls. Variable. 



P. granulifera, Ach., Tuckerm. Thallus glauces- 

 cent and white, pruinose, besprinkled w^ith pow- 

 dery g'ranules, beneath pale, corticate, fibrils 

 black, lobes niultifid, dentate-crenate, apothecia 

 small, inflexed margin crenate. Barmelia, Ach. 

 Occasional on oaks. 



P. comosa, Eschw., Nyl. On juniperus. Not 

 common. 



PKLTIGEREI. 



STICTA, Screb., Fr. Thallus frondose-foliaceous, 

 villous beneath, marked with cyphels or bare 

 spots, apothecia submarginal, scutellseform. 



S. quercizans, Mx., Ach. On oak. Deer Park. 

 Rare as yet. Infantile. 



S. pulmonaria. Is probably found within our limits. 



P. adglutinata, L., Nyl. Thallus often slightly 

 olivaceous, also cinerascent and brown, ad- 

 heres closely to substrate, small, lobes thin, flat, 

 compaginate, apothecia small, disk nigro-fus- 

 cous, margin entire. On hickory. Deer Park. 



