CAROLINIAN AREA IN ALABAMA. 57 



advanced to furnish the data required for this purpose. The frequent 

 yet only indistinctly perceived overlapping of these zones adds to the 

 difficulty of placing satisfactorily the lines by which they are separated. 

 The efforts here made to lay down the lines of life zones and their 

 subdivisions can only be regarded as tentative. 



The following subdivisions of the life zones of Alabama have been 

 recognized as floral regions; that is, as endowed with a flora of 

 characteristic and distinct features, due to the presence of types 

 which, if not confined exclusively to their limits, predominate within 

 them and impart a peculiar character to their several associations. 

 The prevalence of one or another of these associations or plant forma- 

 tions in the different sections of the same region determines the 

 character of its subordinate floral divisions. 



CAROLINIAN AREA OR FLORA. 



A line drawn from the northwestern corner of the State to the lower 

 part of Lee County, crossing the Coosa Valley near Childersburg, makes 

 the limit of the highlands having an average elevation of 800 feet above 

 sea level (E. A. Smith). This line coincides approximately with the 

 isothermal line of 60 F. , and may be regarded as the boundary in Ala- 

 bama of the Upper and Lower Austral zones, therefore of the Carolin- 

 ian and Austroriparian or Louisianian areas. It winds its way from 

 northwest to southeast and southward to the u fall line." Accepting 

 this zonal line, a botanical limit is gained, northward of which is found 

 a flora different in character from that to the southward, generally 

 described as the flora of the great Central Mississippi Valley, and dis- 

 tinguished by the feeble representation, if not total absence, of the 

 subtropical element and the exclusive prevalence of deciduous forests. 

 Various shrubs and trees coincide in their limits of northern and south- 

 ern distribution closely with this boundary line, and serve as unerring 

 guides in pointing out its course. Such truly zonal plants are: 



Pinus lirginiana (scrub pine) . Prunus americana (American plum) . 



Quercus acuminata (yellow-bark chest- Azalea arborescens (sweet-scented azalea) . 



nut oak) . Stuarlia pentagyna. (fringed stuartia) . 



Quercus prinus (mountain oak) . Butneria fertilis (mountain spicewood or 



Quercus coccinea (scarlet oak) . smooth calycanthus) . 



Quercus rubra (red oak) . Rhus aromatica (aromatic; sumac) . 

 Acer leucoderme (white-bark sugar maple) . Adelia ligustrina (southern privet) . 



These all find in Alabama their southern limit on this line. Although 

 the vegetation of the Carolinian area presents in its broad features great 

 uniformity, particularly in its tree growth, there exist in its range of 

 nine degrees of latitude differences in the latitudinal distribution of 

 heat, which necessarily affect the distribution of plants within its lim- 

 its and present insurmountable obstacles to the extension of a number of 

 species northward. Due to this temperature element, there is a most 

 pronounced limit beyond which the successful cultivation of the cotton 



