(127 ) 
(L. HE. p. 420.) But interesting as is the group, in several respects, the 
species are ill-defined; and their limits more than commonly uncertain. 
No clear difference has been indicated for Varicellaria, Nyl., beyond 
the subordinate one of bilocular spores. 
Pertusaria is generally diffused; the fifty described species being 
divided pretty equally between northern, and southern (tropical and 
austral) regions, and the type (P. pertusa) together with P. leioplaca, 
reckoned cosmopolitan by Nylander (Enum. Gén.). Almost the whole of 
the northern forms are European; but only half of them are known as 
yet as North American. Accessions to this number may however be 
expected; though a satisfactory estimate of the variableness of known 
conditions has perhaps yet to be made. 
P. bryontha (Ach.) Nyl., interesting as almost equally referable to 
Lecanora (in which the older writers placed it) and the present genus, is 
an alpine and arctic lichen, and has occurred here, in Greenland (J. Vahl, 
in Th. Fr. Lich. Arct. p. 117, where it is made a section of Lecanora) 
and in islands of Behring’s Straits (Mr. Wright).——P. dactylina (Ach.) 
Nyl. in Prodr. Fl. N. Gran. p. 36, note (Isidiwm, Ach.) was also found by 
Mr. Wright in islands of Behring’s Straits, and illustrates the fruticulose 
overgrowth of the Pertusariine thallus..——P. velata (Turn.) Nyl. Scand. 
p. 179 (Parmelia, Turn. in Linn. Trans. 9, p. 143, t. 12, f. 1) with lecano- 
roid apothecia, has long been known to me, and is common throughout 
the United States; but has in great measure escaped the attention of 
authors. It is near to P. multipwncta (Sm.) Nyl. in Prodr. N. Gran. 
p. 35 (P. faginea, Tuck. Synops. N. E. p. 85) which is found everywhere. 
——P. lecanina, described below,? is another lecanoroid species, peculiar 
to California.——P. pustulata (Ach.) Ny]. in Prodr. N. Gran. p. 35, and 
in Herb. Lindig n. 2877, is everywhere a common lichen here, and distin- 
guishable by its bi-sporous thekes.——P. glomerata (Ach.) Scheer. (Parm. 
verrucosa, b, Fr. Tuck. Syn. N. Eng. p. 42) occurs frequently in the alpine 
1 A similar Pertusaria, growing over mosses, in the alpine district of the Great 
Haystack, New Hampshire, differs (in my specimens) in having a less evidently, 
or not at all isidioid-elongated thallus; and I have found no spores.——Isidium 
UL ee DC. (I. stalactiticwm, Clement., Ach.) appears, as Acharius called 
‘ distinct from I. dactylinum, and to possess the aspect of Pertusaria ; but the 
eee in my possession (Welwitsch Cr, Lusit. n. 22. Delise in herb. Duby.) 
have not afforded me hymenia. 
2 Pertusaria lecanina (sp. nova) thallo tenut equabdili pallide lutescente ; apo- 
theciis lecanoroideis (0™™-, 6-1™™- lat.) sessilibus monothalamis primitus albo-pul- 
verulentis, margine thallino integro, disco carneo-pallescente submarginate. Spore 
bine in thecis, ellipsoidec, longit. 0,092-142™™., crassit. 0,0830-50™™-——On bark of 
Aisculus Californica (growing in company with Pertusaria leioplaca and P. pustu- 
lata) and also on bark of Pinus insignis, in California (Mr. Bolander). Except in 
being larger, and in their pale-yellowish colour, the apothecia are not very dissim- 
ilar to those of a minute, finally often zeorine, southern and tropical variety of 
Lecanora subfusca (v. duplicata, of the present writer) given in Wright Lich. Cub. 
n. 119. 
