OF ARTS AND SCIENCES. 397 



Dr. Nylander has founded his distinct genus Dactylina, stands in obvi- 

 ous affinity ; and the equally obvious differences of the two plants seem 

 to be fully mediated by our second species, fertile specimens of which 

 were first detected on islands of Behring's Straits, by the careful eye 

 of Mr. Wright. 



Dacttlina arctic a (Hook.) , Nyl. 1. c. Dufourea, Hook, in Richards. 

 Append, to Frankl. Narr. p. 762, t. 31. Evernia, Tuckerm. Syn. p. 11. 

 Bear Lake and elsewhere in Arctic America, Richardson. Rocky 

 hill-sides, Behring's Straits, 3Ir. Wright. Thallus becoming erect, sim- 

 ple, or very sparingly divided, ventricose, smooth and shining, rather 

 attenuated above towards the obtuse apices, pale yellow, becoming 

 brownish at the base, within hollow, the medullary filaments only thinly 

 or even obscurely clothing the walls. The taller of these specimens 

 rather exceed two inches in height, by two to three, or at the base four 

 lines in width ; but they reach nearly twice these dimensions (Hook., 

 Nyl.). Rarely, specimens are more divided above, the (2 or 3) simple 

 branches showing something of the fastigiate habit of D. madreporifor- 

 mis. Apothecia largish (two lines in diameter in my fertile specimen), 

 a single one occupying the summit of a branch, or branchlet, which is 

 wrinkled below and passes above into a crenulate, at length obscure 

 margin, enclosing the flat, shining, dark chestnut-coloi'ed disk. Spores 

 in eights, in somewhat ventricose or wedge-shaped spore-sacks, small, 

 colorless, spherical, limbate ; the paraphyses being indistinct. Spermo- 

 gonia unknown. 



Dacttlina ramulosa. Dufourea ramulosa, Hook. Append, to 

 Parry's 2d Voy. p. 414. Evernia, Tuckerm. Syn. p. 11. Arctic Amer- 

 ica, Hook., 1. c. Rocky Mountains, Herb. Hook. Hill-sides (on rocks), 

 Behring's Straits, 3Ir. Wright. Thallus very much smaller than in the 

 last (the specimens scarcely exceeding half an inch in height, except in 

 the branched state, when they do not exceed an inch), but at first not 

 wholly unlike it ; the inflated and rarely somewhat finger-shaped, obtuse 

 branches becoming, however, soon nodose (it would be interesting to 

 compare here the scarcely known Dufourea nodosa, R. Br., in Ross's 

 Voyage) and lacunose-uneven, and passing into the dichotomously 

 branched state, almost muricated with short, elongated-papilliform 

 branchlets, which is, if I mistake not, (the specimen from the Hook- 

 erian Herbarium referred here being without name,) the type of the 

 species as understood by Hooker. Some of the specimens of the sim- 

 pler condition are pale straw-colored, the tips only being brownish ; but 



