x INTRODUCTION 
in the publication of Chapman’s Flora of the Southern United States, in 
1860. Then, botanical activity waned in the South. Toward the end of 
the last century, however, a revival took place in the southeastern states, 
mainly through the activities of permanent and transient residents, of 
plant collectors, and of botanists and naturalists who moved into the region 
to fill professional positions. 
In pioneer days with the horse and few trails, the sail-boat and un- 
developed water-ways, botanical exploration was restricted to limited areas 
and progressed slowly, consequently the botanical harvests were often scant. 
Since the advent of the automobile, the motor-boat, and the construction 
of a vast network of highways, canals, and improved waterways, largely 
through virgin country, a vast territory, until recently inaccessible, has been 
made to yield numerous botanical and horticultural treasures. As a con- 
sequence, many additional species and not a few genera of all groups of 
plants have been recorded for the area under consideration only since the 
end of the last century. 
The area extends over about twelve degrees of latitude. The southern 
limit lies within less than a hundred miles of the Tropic of Cancer. The 
northern limit is not very far north, but two mountain ranges, with a mul- 
titude of peaks rising to between five and six thousand feet and several 
to more than six thousand, furnish a cool climate representing a high lati- 
tude through altitude. Intermediate altitudes (Piedmont and Appalachian 
Plateau) supply still other elements for greater variety in the vegetation. 
s compared with northeastern America there are one-third more species 
in about one-fifth the area. Three main factors contribute to this con- 
dition—latitude, geology, physiography. 
The ancestors of our present plant-covering were subjected to both 
and minor earth disturbances, elevations and depressions and re- 
semen of the land-mass. Submergences also destroyed vast areas 
coastwise vegetation several times. When the areas emerged from the 
sea for the last time and the higher lands became more stable, the coastwise 
areas were populated from both the plant refuges in the highlands and 
those of continental and insular regions lying to the south. Whether these 
early floras were more extensive in kinds and density of population than 
those of today we shall never know. The records of several different 
floras are preserved in the sedimentary rocks, but they are naturally very 
incomplete. Large areas of eroded materials of the very old geological 
formations, often segregated into areas of different kinds of soil, such as 
sand, clay, marl, loam, in the Coastal Plain and the Piedmont, very defi- 
nitely contribute to the complexity of the flora. Then, in relatively recent 
geologic time, came the advance of successive great ice-sheets from the 
north as far south as New Jersey and Pennsylvania, with accompanying 
eold, which killed the vegetation before their immediate front, while they 
