Nov., 1906.] Key to the Families of Ohio Lichens. 
1 5 
10. Thallus crustaceous, ovate or lobed at the border, without cortical 
layer; pycnidia exobasidial. Buelliaceae. 
11 . Thallus-when moist, more or less gelatinous, usually unstratified, 
scaly, foliose or fruticose, seldom crustaceous; apothecia sessile; 
alga a Nostoc. Collemaceae. 
11 . Thallus when moist not gelatinous nor swollen. 12. 
12 . Thallus crustaceous, border lobed, horizontal. 13. 
12. Thallus squamulose or foliose, horizontal or with border elevated; 
fastened to the substratum with rhizoics or umbilicus; pseudo- 
parenc lymatous throughout, or with cortical layer above or on 
both sides. 19. 
12. Thallus cylindrical or fruitcose, upright or pendant; fastened to sub¬ 
stratum with an anchor disc, or ciying off from the ground grow¬ 
ing radially; entirely covered with cortical layer. Usneaceae. 
13. Thallus with algae belonging to Chroolepus or Phylactidium. 14. 
13. Thallus with algae belonging to Pleurococcus or Palmella. 15. 
14. Exciple usually without algae, rarely rudimentary or wanting. 
L.ECAN ACTIDACEAE. 
14. Exciple with algae always present; apothecia single or in groups 
sunken in thalline warts. Thelotremaceae. 
15. Ascus one to eight spored, seldom sixteen to thirty-two; apothecia 
with distinct border or margin. 16, 
15. Ascus many spored. Acarosporaceae. 
16. Exciple without algae. 17. 
16. Exciple with algae; apothecia lecanorine. 18. 
17. Apothecia sessile. Lecideaceae. 
17. Apothecia borne on a stipe. Cladoniaceae. 
18. Apothecia sessile; border distinct. Lecaxoraceae. 
18. Apothecia single or in gropus, sunken in thalline warts; border usually 
very small. Pertusariaceae. 
19. Apotnecia in young stage or always with the entire under side buried 
in the thallus; without margin, or bordered with the remains of 
t e old covering. Peltigeraceae. 
19. Apothecia on well defined stipes which are often strongly expanded 
and branched; naked or covered with thalline scales. 
Cladoniaceae. 
19. Apothecia sessile or short stalked; margin distinct. 20. 
20 . Interior hyphal layer wanting or indistinct , thallus entirely or in 
great part pseudoparenchymatous, with algae belonging Scyto- 
nema; pycnidia exobasidial. Heppiaceae. 
20 . Interior hyphal layer distinct in the well stratified thallus. 21. 
21. Spores more or less spindle form, multiseptate, colorless or brownish; 
under side of t.iallus with abundant cyphellae or pseudocyphellae. 
Stictaceae. 
21. Spores ovate ellipsoid, or long ovate, one-celled (by exception two- 
celled), or muriform, in which latter case they are dark colored; 
cyphellae never present. 22. 
22. Thallus with algae belonging to Scvtonema. Pannariaceae. 
22. Thallus always with algae belonging to Pleurococcus or Palmella 
apothecia sessile with algae in exciple. Parmeliaceae. 
23. Cavity of perichecium simple; not divided by complete or incomplete 
partitions. 24. 
23. Cavity of pertithcium divided by complete or incomplete partitions; 
algae, Palmella or Chroolepus. Mycoporaceae. 
24. Thallus foliose or scaly, with cortical layer on both sides or on upper 
side only; algae Pleurococcus of Palmella. Dermatocarpaceae. 
24. Thallus crustaceous, without cortical layer or with amorphous cortex 
made up of horizontal hyphae. 25. 
