LICHENS I IX 



the following addition: Z. occulata gonatodes Ach., on rock on St. 

 Paul Island. Of another plant he notes : "Lecanora saxicola Schaer. 

 Specimens which may prove to represent a new species have been 

 provisionally referred here by Mr. Branth." 



PLACODIUM. 



KEY TO THE SPECIES. 



Thallus well developed, typically lobed at the circumference. 



Thallus orange-colored elegans. 



Thallus bright yellow murorum. 



Thallus poorly, or not at all, developed, not lobed at the circumference. 

 Spores simply bilocular. 



Thallus orbicular, crenate-granulose crenulatum. 



Thallus effuse, granules usually crowded into heaps, sometimes 



scattered vitellinum. 



Spores polar-bilocular. 



Growing over mosses jungermannice. 



Growing on wood or stone. 



Thallus very uneven, warted aurantiacum. 



Thallus comparatively smooth. 



Hypothallus bluish-black cerinum. 



Hypothallus obsolete. 



Apothecia orange-colored beneath and on the margin. 



cerinum. 

 Apothecia greenish beneath and on the margin. 



fuscoatra. 



120. Placodium vitellinum (Ehrh.) Naeg. & Hepp. 



Lichen vitellinus EHRHART, Crypt, n. 155. 1785. 



Placodium mtellinum NAEGELI & HEPP, Sporen der Flecht. Eur. n. 70. 1853. 

 SOWERBY, Eng. Bot. /. 1792. 



Hot Springs, Baranof Island (Trelease, 963 in part). On rocks 

 with Lecidea enteroleuca and Parmelia saxatilis. Wright collected 

 this species at Bering Strait, while Rothrock reports it from Port 

 Clarence. Under the synonym Lecanora mtellina Ach., Ny lander 

 reports its occurrence on St. Lawrence Island. 



It is a widely distributed species and closely related to the following, 

 which may, perhaps, be considered as developed from it. 



121. Placodium crenulatum (Wahl.) Tuck. 



Lichen murorum y crenulatus WAHLENBERG, Lapp. 416. 1812. 

 Placodium crenulatum TUCKERMAN, Syn. N. A. L. i : 180. 1882. 



Hot Springs, Baranof Island (Trelease, 984) ; Plover Bay, Siberia 

 (Trelease, 995, 996). On stones. In Rothrock's list this is reported 



