KEY TO ORDERS AND FAMILIES 



A. Thallus of more or less definite form, usually bearing fruits 



B. Spores borne in asci ASCOLICHENES 



B. Spores borne on basidia HYMENOLICHENES 



(45. Thelephoraceae) 



A. Thallus of entangled hyphae, without fruits . . LICHENES IMPERFECTI 



(46. Leprariaceae) 



ASCOLICHENES 



A. Hymenium produced in a closed structure opening 



by a minute pore, for the escape of spores PYRENULALES 



A. Hymenium produced in an open disklike structure 



B. Asci disintegrating and the spores forming a mazaedium . . . CALICIALES 

 B. Asci persistent, no mazaedium formed 



C. Thallus rudimentary to rarely well developed; 



apothecia irregular, linear, or oblong . HYSTERIALES 



C. Thallus commonly well developed; apothecia 



more or less round or cuplike LECANORALES 



PYRENULALES 



A. Perithecia opening through irregular pores, crowded 



together, divided by more or less complete walls 10. Mycoporaceae 



A. Perithecia opening through round pores, separate 



B. On leaves 7. Strigulaceae 



B. On rocks, trees, old wood, and soil 



C. With Nostoc as the algal host 8. Pyrenidiaceae 



C. With Scytonema as the algal host 9. Pyrenotrichaceae 



C. With Pleurococcus as the algal host (or Palmella) 



D. Thallus crustose 1. Verrucariaceae 



D. Thallus foliose or squamulose 2. Dermatocarpaceae 



D. Thallus shrubby or fruticose 3. Pyrenothamniaceae 



C. With Trentepohlia as the algal host 



D. Perithecia not seated in a stroma 4. Pyrenulaceae 



D. Perithecia seated in a stroma 



E. Perithecia upright, separate, each with single mouth 5. Trypetheliaceae 

 E. Perithecia crooked or bent, more or less united, 



mouths joined into a central canal 6. Astrotheliaceae 



CALICIALES 



A. Thallus crustose, without cortex 



B. Apothecia borne on stipes 11- Caliciaceae 



B. Apothecia not borne on stipes 12. Cypheliaceae 



A. Thallus foliose or bushy, with cortex 13. Sphaerophoraceae 



HYSTERIALES 



A. Apothecia without the exciple 14. Arthoniaceae 



A. Apothecia with the exciple 

 B. Thallus crustose 



C. Thallus rudimentary, often inconspicuous 



D. Apothecia not seated in a stroma IS. Graphidaceae 



D. Apothecia seated in a stroma . . .... 16. Chiodectonaceae 



C. Thallus well developed 17. Dirinaceae 



B. Thallus fruticose 18. Roccellaceae 



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