216 PERTUSAKIA. 



sized, globular, sub-sessile, with mostly solitary, protuberant 

 ostioles ; but soon agglomerate and confluent into large, difform, 

 crowded, pleiothalamous clusters. Spores very commonly in 

 twos ; but occurring also in fours ; sixes ; and eights ; ^'^ mic. 



Ach. Syn. p. 111. Schcer. Spicil. p. 66. Tuck. Exs. n. 22 



(Sub. Farm. verr.}. Nyl, Scand. p. 182. Th. Fr. Scand, p. 314. 

 On the earth, running over mosses, etc., in alpine districts. 

 White Mountains, Tuckerman Syn. N. E. 1848 (spores almost 

 always in twos ; and rarely solitary). Adirondack Mountains, 

 N. Y., Macrae (spores as in the last). Islands of Behring's 

 Straits, Wright (spores in fours; and eights). The species- 

 name suits our lichen perhaps quite as well as it does the Euro- 

 pean one; and ours (Tuckerm. exs. n. 22) is certainly like the 

 other in the earlier conditions of the fruit, but passes at once 

 into a confluent, difform state with the look of largest apothe- 

 cia of P. communis, but the ostioles of the present of which 

 my few foreign specimens scarcely afford a trace. The spores 

 might appear also to suggest difference in the plant of our 

 mountains from the European, the thekes of which have always 

 been taken for 4-sporous ; but the distinction is a slight one, and 

 Dr. Th. Fries has recently shewn (I c.) that the Swedish lichen 

 varies from 3 to 8-sporous. 



14. P. globularis, Ach. ; thallus incrusting, thin, granulate; 

 whitish-ash-coloured ; granules globular, becoming finger-shaped, 

 and finally somewhat branched ; apothecia small to almost mid- 

 dling-sized, sub-sessile, depressed-globose ; the commonly few* 

 ostioles collected in the sunken centre. Spores in twos ; threes ; 



and fours ; -^^ mi c. Ach. Syn. p. 212. Tuckerm. Syn. N. 



E. p. 85. 



Rocks among mosses. Northern and middle States, Muhlen- 



berg Catal 1818. Alabama, Peters. Arkansas, The same. 



Granules varying in size ; and in some of the specimens, both 

 northern and southern, they do not become isidioid ; but I see 

 no other differences'. 



15. P. Wulfenii, DC.; thallus cartilagineous and smooth, 

 but becoming thicker and rugose-verrucose ; sulphur-coloured, 

 and pale ; apothecia small to more than middling-sized, sub- 

 sessile, depressed-hemispherical ; the numerous black ostioles 

 largely running together into a depressed, lecauoroid disk, bor- 

 dered by a tumid, somewhat gibbous-flexuous thalliue margin. 



