264 PLANT LIFE OF ALABAMA. 
the vicinity of Auburn, which were kindly placed at the service of the 
writer by the collectors, Profs. F, S. Earle and Carl Baker. 
GENERAL DISTRIBUTION. 
Of the 49 genera known at present to be represented in Alabama, the 
following are of an exclusively southern range: 
Strigula. ' Glyphis. Gyrostomum. 
Pyrenastrum. Chiodecton. Thelotrema. 
Lecanactis. Heterothecium. 
Trypethelium. Coenogonium. 
These are most numerously represented by species inhabiting the 
Louisianian life area, which frequently extend to the neighboring trop- 
ics and are rarely found north of the Carolinian life area. Represented 
by a number of species in the southern part of Eastern North America 
and also in the tropics are: 
Graphis. Leptogium. Pyxine. 
Pyrenopsis. Collema. 
Omphalaria. Sticta. 
These are also frequently met with in the Alleghenian area. 
Of decidedly northern distribution are such as— 
Verrucaria. Rhizocarpon. Placodium. 
The representatives of these genera in the Southern States are mostly 
confined to the mountain region. Elsewhere they are widely scattered 
from the cooler temperate to the frigid zones and the cooler regions of 
the Old World. 
The following are more or less equally distributed throughout the 
cooler and warmer zones, and many of them have numerous represent- 
atives in corresponding regions of the Old World: 
Pyrenula. Rinodina. Cetraria. 
Arthonia. Leptogium. Physma. 
Opegrapha. Collema. Physcia. 
Buellia. Lecanora. Parmelia. 
Biatora. Placodium. Evernia, 
Baeomyces. Heppia. Ramalina. 
Gyalecta. Pannaria. Usnea. 
Pertusaria. Peltigera. 
Up to the present 198 species and 26 varieties of lichens have been 
recognized in Alabama. 
REGIONAL DISTRIBUTION, 
Although generally of a wide distribution, the greater number of 
species and varietal forms of these lowly plants are more or less strictly 
confined to the several life areas with their floral regions, which share 
the State. Nearly one-half (48.6 per cent) are confined within the limit 
'Strigula occurs in Polynesia. 
