(237) 
appears much in excess; and the same is true of C. triste, Koerb. (Hamp. 
in herb. Th. Fr.) and C. Ravenelii ; and possibly also in other species, 
especially of an inferior lichenose grade. 
In the spores, Acoliwm exhibits the whole differentiation of the brown 
type. Dr. Th. Fries, in his observations on the insufficient distinction of 
Rhizocarpon, Massal., from Buellia (Lich. Arct. p. 226) has well drawn 
attention to the significant fact that the spore-forms of both these groups 
occur in Acolium ; and indeed in otherwise most closely related species. 
A. Bolanderi has first added simple and spherical spores to the history of 
the genus. But this species belongs none the less to the same section, or 
natural cluster, which shall include A. Californicum. The remarkable 
modification of the coloured type exhibited in A. leucampyx has been 
considered in the description of that lichen (Obs. Lich. 1. c. 5, p. 390). 
Twenty species, or marked forms of Acoliwm, as above taken, are 
reckoned by authors; of which fourteen are northern, and the rest 
tropical. Only three of the ten European forms have as yet occurred 
here; but we possess four peculiar to the country, and one tropical 
species. The important group represented by A. tympanellum, and in- 
cluding as well the related saxicoline forms described by Nylander, as the 
parasitical A. stigonellum, is, quite remarkably, deficient east of the 
Rocky Mountains ; although the species first named is said to agree gen- 
erally, in its geographical distribution, with .A. tigiliare, and to be found, 
in the mountainous regions of Europe, in the same places (Nyl. Syn.). 
Muhlenberg reckons indeed (Catal. pl. Amer. Sept.) A. stigonellum, but I 
have seen nothing nearer to this species than an externally not dissimilar, 
parasitical Buellia (B. inquilina, Lich. Calif., append.) inhabiting Pertu- 
sarie, in the southern states. 
A. Bolanderi, Tuckerm. (Lich. Calif. p. 27) from sandstone rocks 
exposed to the sea-fog, Oakland hills, California (Mr. Bolander) is remark- 
able as well for its spherical, simple spores (0,008-16™- diam.) as for its 
conspicuous, accessory thalline exciple (measuring, in the best condi- 
tions, 1™™. -2™™. 5, in width, but also occurring, in reduced states of the 
lichen, considerably smaller) in which last feature it agrees with the next 
two following species. ——A. Californicum, Tuckerm. (Trachylia, Obs. 
Lich. 1. c. 6, p. 263) from the same rocks with the last (Mr. Bolander) is 
distinguished by its lobulate thallus. Apothecia 2-3™™ wide. Spores 
bilocular, 0,018-25™: long, and 0,010-18™"- wide. The general agree- 
ment, in all the most important structural details, of these two lichens, 
taken in connection with the difference in their spores, furnishes evidently 
a new argument against the generical separation of the round-spored 
Calicia (Cyphelium, Koerb. Anzi. Chenotheca, Th. Fr.).—A. Caro- 
linianum, Tuckerm.,! a recent discovery in the low country of South 
1 Acolium Carolinianum (sp. nova) thallo tartareo wquabili 1. dein ruguloso 
rimoso e glaucescente pallide lutescente ; apotheciis in verrucis thallinis mastoideis 
(1-2™™. lat.) innatis, disco plano-convexo nigro, margine nullo. Spore octone, 
