THE GENUS EVERNIA AS REPRESENTED IN NORTH 
AND MIDDLE AMERICA ~ 
R. HEBER Howe, Jr. 
(WITH PLATES XXIV AND XXV) 
Genus: Evernta Ach. Lich. Univ. 84 et 441. 1810 
The species of the genus, since 1753, have appeared under the 
following: Lichen L. (1793), Lichenoides Hoffm. (1790), Lobaria 
Hoffm. (1795), Usnea Hofim. (1795), Parmelia Ach. (1810), Bor- 
rera Ach. (1810), Physcia DC. (1815), Cornicularia DC. (1815), 
Ramalina Chev. (1826), Archevernia Th. Fr. (1831), Letharia Th. 
Fr. (1831), Phacopsis Tul. (1852), Chlorea Nyl. (1859), Rhytido- 
caulon Nyl. (1859), Alectoria Mudd (1861), Nylanderaria Kuntze 
(1891); comparatively few of these, however, are generic synonyms. 
Description: A pothecia subterminal, marginal or lateral; 
scutelliform, applanate or concave, sometimes convex and lacerate; 
Marginate (thalloid dilations=vulpina); thalline exciple rugose; 
disk chestnut. Asci clavate, containing eight spores; paraphyses 
gelatino-filamentous. Spores monoblast, hyaline, ellipsoid. Sper- 
mogones immersed, black. Sterigmata branched, articulate. Sper- 
matia acicular, incrassate near apices. 
Thallus caespitose, subpendulous or pendulous, branched; cor- 
tex rugose, sometimes perforate, smooth, furfuraceous or isidioid, 
Subterete (subradial), compressed (bifacial) or angulate; rhizinae 
rarely present; sulphur yellow, stramineous, virescent-stramineous, 
orcinereous; medulla cottonous, arachnoid, or somewhat coalescent. 
Gonidia, Protococcus (Cystococcus humicola Naeg.). Soredia normal. 
Cephalodia small, often warty, concolorous, sea-green or black, often 
gelatinous. 
OBsERvations: After all has been said, I can see no sufficient reason for 
Separating the genus as given by TUCKERMAN. That the species here con- 
Sidered all have cottonous arachnoid medullas, whether more or less coalescent, 
‘annot be questioned, and in none of the species does a true chondroid, axial 
Cord exist. This slight variation in the condition of the medulla (one more or 
less of growth) does not in the least justify generic separation. It is true, as 
VCKERMAN pointed out, that thalline differences must always constitute our 
“titeria for generic distinction in this most difficult group of plants; yet if 
431] (Botanical Gazette, vol. 51 
