lichens of the lower ozark region of missouri and arkansas

Key H : Crustose lichens with round apothecia (continued)
12. Apothecia superficial; paraphyses branched and anastomosing; thallus
brownish to dark gray ................................ Rhizocarpon
12. Apothecia immersed and sunken; paraphyses simple to sparsely furcate;
thal lus pale gray ....................................Diploschistes
7. Ascospores simple to transversely septate ..................................13
13. Ascospores greenish to brown ........................................14
14. Thallus placodioid, distinctly lobate at the margins, yellowish green (usnic acid);
on siliceous rocks ..................................... Dimelaena oreina
14. Thallus crustose to areolate, not marginally lobed, not yellowish green (usnic acid
absent); substr ate various ............................................15
15. Well developed thalline margin present; ascospores with thickened walls, the
lumina angular or subspherical ............................... Rinodina
15. Thalline margin inconspicuous or absent at maturity; ascospores with thin,
uniform walls, the lumina conformable to the outer cell wall ..............16
16. Photobiont Trentepohlia; ascospores pale brown; hymenium and asci IKI-
........................................Melaspilea arthonioides
16. Photobiont Trebouxia; ascospores green to dark brown; hymenium and asci
IKI+ blue ...................................................17
17. Thallus K+ yellow or red (stictic or norstictic acid) or C+ orange
(xanthones), or else thallus a well-developed, ± thick, areolate saxicolous
crust; microconidia elliptical to bacilliform .......................
.................................................Buellia
17. Thallus K-, C- (no lichen substances), thin and ± continuous to obsolete;
substrate various; microconidia acicular to filiform .................
..............................................Amandinea
13. Ascospores hyaline ................................................18
18. Asci each with more than 20 spores .................................19
19. Corticolous; apothecia superficial, with well developed thalline margin
........................................... Maronea polyphaea
19. Saxicolous; apothecia immersed, or if superficial, lacking a thalline margin20
20. Thallus areolate; apothecia immersed, variously colored .............
................................................ Acarospora
20. Thallus inconspicuous; apothecia superficial, dark ................21