-88- 



DiAGNOSis: Thallus caespitose, compressed, flaccid, apices bursting with 

 powdery-soredia, apothecia subterminal; spores straight. 



Description: Thallus caespitose (max. alt. 1.5 cm.), flaccid or sub- 

 flaccid, stramineus to virescent; cortex rarely rugose below, powdery-sorediate; 

 laciniae compressed, lacerate (max. width 4 mm.), apices vaulted or bursting, 

 with white farinose soredia. Apothecia rare, subterminal, concave, marginate 

 (max. diam. 3 mm.), disk buff. Spores ellipsoid, straight or substraight, • 



Contingent phases: (a) Laciniae short subpulvinate (max. alt. 16 mm.) 

 lacunose, scattered with soredia ( = R. pollinaria ^. humilis Ach. Lich. 

 Univ. 609. 1810. Type at Helsingfors. Orig. descript. : "laciniis aggregato- 

 complicatis brevibus lacero-laciniatis, furfum passim latioribus glauco cineras- 

 centibus pulverulentis, maculis lateralibus soredi formibus latissimis confluentibus 

 pulveraceis. " I. c.) 



Substrata: On trees, rarely on rocks = humilis. 



Distribution: Very rare in the Upper Transition to Boreal Zone from 

 California and New Mexico to the Yukon. ^ 



Stations: Yukon, Dawson. New Mexico. Minnesota, Palisades. Cali- 

 fornia, Pasadena; San Jose. Rhode Island. Massachusetts, Beverley, Salem. 

 Vermont, Mt. Mansfield. 



Observations: This generally corticolous species was evidently confused 

 by Tuckerman with forms of farinacea (intermedia = New England records). 

 I have little typical material from our area.^ This species may be distinguished 

 by its subflaccid laciniae which never show throughout longitudinal parallel 

 rugae as in the more rigid maritime polymorpha. The inflated tips with generally 

 white powdery non-granulate soredia offer another good character for determina- 

 tion. The phase or variety humilis is the plant found in our area and is more 

 difficult to distinguish from polymorpha, yet it differs in several points. Though 

 its laciniae are lacunose, they are never parallel-rugose throughout, never rigid,, 

 and always with bursting sorediate apices. R. humilis is subpulvinate, and 

 scattered with granulate and confluent soredia, and thus approaches polymorpha. 

 This latter character, as I have already said, caused me to mis-determine the plants 

 collected in the Yukon. Mr. Merrill has reported this phase from San Juan 

 Islands, Washington (Bryologist 11: 51. 1908). Other authors have recorded 

 it as follows: Ohio, Fink and Bogue; Maine, Eckfeldt and Harvey; South Dakota,, 

 Fink; Newfoundland and Labrador, Eckfeldt; New Mexico, Tuckerman; Cali- 

 fornia, Hasse; New Hampshire, Howe fide Wheelock; Massachusetts, Sprague; 

 and Cummings; New York, Harris; North Carolina, Merrill; Newfoundland, 

 Arnold; and Alaska, Macoun. This species is still hardly more than a hypotheti- 

 cal member of our flora; it having never occurred in a fertile or absolutely typ- 

 ical state. Its exact range is uncertain. 



[To be continued.] 



1 No distributional maps are given for species whose range cannot be definitely defined. 

 ^ See Merrill, Bryologist 14: 36. 1911. 



