lichens of the lower ozark region of missouri and arkansas

Key B: Foliose lichens (continued)
51. Thallus sorediate, the soredia sometimes arising from coarse,
isidia-like pustules ...................................55
55. Medulla yellow; lobe tips pruinose ............ Pyxine
55. Medulla white; lobes tips epruinose ................56
56. Thallus closely appressed to and appearing almost
confluent w ith sheltered siliceous rocks; rhizines lacking
............................. Dirinaria frostii
56. Thallus ± adnate on, but not tightly appressed to, various
substrates; rhizines abundant ......................57
57. Larger rhizines with frequent dichotomous branches;
thallus with coarse, inflated, hollow Hypotrachyna pustulespustulifera
57. Larger rhizines simple to sparsely furcate; thallus
without pustules .............................58
58. Soredia in diffuse laminal patches; medulla often
pale yellow, at least locally; white portions of
medulla K-, KC- ........ Myelochroa aurulenta
58. Soredia in small, laminal soralia or occurring
along thallus ridges; medulla uniformly white, K+
yellow (stictic acid) or KC+ briefly faint purple
(divaricatic acid) ............... Canoparmelia