144 CUMMINGS 



east Cape (Coville and Kearney, 2008) ; Port Clarence (Trelease, 

 1254, 1 1 12, the latter a fragment mixed with Parmelia saxatilis, 

 Parmelia physodes and Alectoria divergens) ; Cape Nome (Setch- 

 ell). All specimens sterile. Collected at Taku by Dr. Hayes, and 

 on St. Paul Island by J. M. Macoun ; Hooker and Arnott report its 

 occurrence at Kotzebue Sound, and Babington credits it to the same 

 locality. Nylander lists Platysma cucullata Hoffm. as occurring at 

 Port Clarence. 



This species is distributed from about latitude 40 N. to the Arctic 

 regions, both in the Old and New Worlds. 



211. Cetraria islandica (L.) Ach. 



Lichen islandicus LINNAEUS, Fl. Suec. 1085. 1755. 



Cetraria islandica ACHARIUS, Meth. Lich. 293. 1803. SOWERBY, Eng. Bot. 

 /. 1330. NYL. Syn. t. 8. f. 32. 



Summit of White Pass (Trelease, 1193) ; Kadiak (Trelease, 1194, 

 11940, 1194$), mixed with Alectoria and Cladonia; Unalaska (Set- 

 chell) ; Hall Island (Trelease, no number) ; St. Matthew Island (Co- 

 ville and Kearney, 2113) ; St. Lawrence Island (Trelease, 1206) ; Port 

 Clarence (Trelease, 1198, 1207); St. Michael (Setchell) ; Cape 

 Nome (Setchell) . Babington reports its occurrence at Norton Sound 

 and Kotzebue Sound ; Hooker and Arnott credit it to the latter locality. 

 J. M. Macoun collected it on St. Paul and St. George Islands, the 

 forms gracilis and robustus growing with the type. Also collected 

 on Seward Peninsula by Arthur J. Collier. 



This is a very variable species, and the transition forms between the 

 species and its varieties are very puzzling. No. 1207 may be consid- 

 ered one of the most typical forms, though these specimens are some- 

 what lighter than is normal. The thallus grows nearly upright, 

 branching freely. The fibrils on the edge of the lobes of the thallus 

 are short and unbranched. The specimen from Port Clarence (NO. 

 1198) is much abbreviated, and in the broadening of its shining lobes 

 tends toward the variety platyna. The most interesting variation, 

 however, is in the specimens from the summit of White Pass (NO. 

 1193) and from Kadiak Island (NO. 11940). In these specimens the 

 lobes are long, narrow, and flexuous, thickly beset on the edge with 

 long fibrils, which in the specimen from White Pass are variously 

 branched. Dr. Lindsay, in West Greenland Lichens, 321, suggests 

 that this state " might appropriately bear the name (if name is re- 

 quired) of form or variety leucomeloides " because of its resemblance 

 to Physcia leucomela. All these specimens are sterile. 



