(199 ) 
and in this case it may be difficult to keep Lithographa, Nyl., separate 
from it. 
There is no instance as yet of an Opegrapha, exhibiting the final, 
mural-multilocular stage of differentiation of the coloured spore. O. Rui- 
ziana, Fée, offers indeed decolorate spores of this structure, and looks 
generally, as presented in Lindig’s collection,— and the same remark 
may be made of the externally not dissimilar O. ovata, Fée (Herb. Meissn.) 
—almost as much like Opegrapha as Graphis ; but both these lichens 
belong really, as indicated by Nylander, to the latter genus. 
Of the thirty species, more or less, now known, (Nyl. ll. cc.) the larger 
part isextra-tropical. Some northern species extend into tropical regions, 
and tend thus to equalize the proportional distribution; but the genus 
contrasts evidently, in this respect, with Graphis. Seven or eight are 
known to me as North American; but the number is doubtless to be 
increased, both at the north, and, especially, at the south. Not oneof the 
Opegraphe of calcareous rocks in Europe has yet been observed here. 
The stock of O. lentiginosa, Lyell (Nyl. in Prodr. N. Gran. p. 92, obs.) 
-is represented here by two lichens. One of these—O. tribulodes!— 
described below, is scarcely perhaps to be distinguished from the European 
species but by the colourless hypothecium, and rather larger spores. It 
has occurred, only parasitical on Trypethelium cruentwm, in Texas (Mr. 
Ravenel) and Alabama (Dr. Curtis). The other— O. demissa—a descrip- 
tion of which is for the present reserved, is marked by larger, rather 
sunken fruit, scattered over an indistinct pale spot on the bark of Holly, 
Witch Hazel, and Poison Dogwood in southern Massachusetts (Mr. Willey) 
and yet larger spores. —— O. owlocheila, Tuckerm. (Lich. Calif. p. 32) 
was found by Schweinitz, on granitic rocks at Salem, North Carolina ; 
and is best comparable, asrespects both habit, and spores, with 0. cerebrina 
of European lime-rocks. —— 0. microcyclia, Tuck. Obs. Lich. 1. ¢.6, p. 285 
(0. myriocarpa, Suppl. 1, 1. c. p. 429 non Mont.) inhabits Yellow Birch 
and other trees in New Hampshire, and Massachusetts, and is readily 
distinguished by its granulose thallus, and very minute, roundish apothecia. 
Spores in eights, in short, ellipsoid thekes; dactyloid or sub-dacryoid ; 
1 Opegrapha tribulodes, thallo nullo ; apotheciis in Trypethelio cruento para- 
siticis, minutis ellipticis oblongisve simplicibus 1. dein 3-4-cuspidatis nigris, disco 
rimeformi dein sub-dilatato. Hypothecium incolor. Spore in thecis abbreviatis 
(ovalibus 1. saccato-clavatis) octona, ellipsoidece, biloculares medioque seepe con- 
stricte, nigro-fusce, longit. 0,016-21™™., crassit. 0,006-9™™., paraphysibus subdis- 
tinctis. ——Southern parts of Texas (Mr. Ravenel). Alabama (Dr. Curtis), — 
Thalline features of O. demissa as yet very obscure ; but the plant is not parasiti- 
cal. Apothecia commonly 1™™- in length, scattered and simple, white within. 
Spores in eights (in clavate thekes) bilocular, and constricted at the middle, brown, 
0,016-23™™: Jong, 0,006-9™™. wide. Paraphyses not always indistinct. With 
jodine, in some specimens, only the tips of gravid thekes shew a slight bluish 
tinge ; but in others, the blue reaction is more marked. 
