jon). = 
American lichen with Pyrenula leucoplaca) a decolorate exhibition of the 
spore-type of the last-named group. Blastodesmia is a modification of 
the Pyrenula-spore, looking, as Massalongo saw, towards his Polyblastie 
corticole, and in fact merging in the latter. As seen indeed in the tropical 
species, the passage from Pyrenula, Koerb., to the bark-Polyblastie 
(Sporodictyon, Stizenb., prop.) is so nearly imperceptible, that we carry 
art beyond its province, to disjoin these clusters. There is at least no 
room for doubt that, excluding species of Sagedia, Koerb. (on the ground 
assumed in this treatise that the acicular or colourless spore-type is of a 
distinct and higher series than the muriform or coloured) we have in the 
corticoline section of Verrucaria, Fr., into however many subordinate 
clusters we divide it, a natural group, distinguished from the saxicoline as 
well generally by a significant deterioration of lichenose character, as 
specially by the obsolescence of the thallus, and the marked coloration 
(in the principal and central types) of the spores. 
Like Thelotrema, with which genus it agrees, as elsewhere already 
suggested, in some important structural features, as especially in the rich- 
ness and not unfrequent irregularity in details of its spore-history, 
Pyrenula has its centre and a wide extension in the intertropical regions; 
the number of northern and austral species recognized by Nylander not 
much varying perhaps from one-third only of the whole. Several inter- 
esting European Pyrenule are still unknown as North American; but 
our southern limits include already—and the number will doubtless be 
extended —some important tropical ones. 
North American species with (excepting 1, 2) decolorate spores. 
Pyrenula pygmea (Koerb.) (Microthelia, dein Tichothecium, Koerb. 
Findococcus erraticus, Nyl. Pyr., e Lich. Nov. Gran.). On the thallus of 
a Lecidea, Greenland, J. Vahl, e Th. Fr. Lich. Arct. p. 275. The only 
instance in Pyrenula of polysporous thekes; and so close is the relation 
of the above-reckoned form to another in which the spores are commonly 
in eights, that authors who have generally accorded systematic weight to 
the polysporous anomaly, have not attempted it here.——P. thelena 
(Ach.) (Verrucaria, Ach., Nyl.). Trunks, North Carolina (Rev. Dr. Cur- 
tis). South Carolina (Mr. Ravenel). Alabama (Mr. Peters). Also (scarcely 
differing) on White Birch, Massachusetts. Spores bilocular, smaller than 
in the next species, and always brown. Paraphyses, in our plants, rarely 
and only imperfectly distinguishable. The European Verr. cinerella, 
Flot., Nyl. 1853 (Microthelia micula (Flot.) Koerb.) varies similarly (Nyl.) 
in this last respect, but is scarcely to be kept apart (Nyl. Scand. p. 282). 
—— P. punctiformis (Ach.) Naeg. in Hepp Flecht. Eur. 1853 (Verr. 
epidermidis, Nyl. Arthopyr. analepta, Koerb.). On various barks, com- 
monin New England; and occurring westward to Ohio (Lea) and through- 
out the southern States (Ravenel, Hale, &c.). The bi-quadrilocular spores 
larger than in the last, and without colour; but similar lichens occur with 
