PLANT ASSOCIATIONS OF ALABAMA. 37 
undershrubs (including the low perennials with a woody stem and 
branchlets partially dying at the close of the season of growth) and 
perennial, biennial, and annual herbs. 
HYDROPHYTIC PLANT ASSOCIATIONS. 
Of the associations of this group the following are recognized in 
the Alabama flora, consisting of plants: (a) Floating free in water either 
on the surface or submerged; for example, the water fern (Azolla), 
duckweeds (Lemna, Spirodela), bladderworts (Utricularia), hornweed 
(Ceratophyllum), etc.; (6) connected with the soil, rooting either on 
rocks, as Podostemon, many fresh-water algae, and some mosses (Lith- 
ophile associations), or in the loose soil, as the pondweeds (Potamo- 
geton), ditch weed (Ruppia), eelgrass (Vallisneria), and of the higher 
cryptogams Nitella. 
(c) Immersed only at their base and rooting in the slightly sub- 
merged or swampy soil, forming associations of paludial plants, as the 
vegetation of the grassy marshes and of bogs, and the shrubs and trees 
covering the alluvial swamps; for example, cypress swamps. 
XEROPHYTIC PLANT ASSOCIATIONS, 
These consist of the vegetation of the dry, exposed, drifting sands 
of the seashore and of dunes, and the woody vegetation of loose sands 
(Psammophile associations); also of the vegetation of dry prairies 
(‘‘bald prairies”), and of the forests of the dry uplands, either of 
evergreen cone-bearing trees (pine barrens) or deciduous trees. 
HALOPHYTIC PLANT ASSOCIATIONS. 
These are composed mostly of aquatic plants, inhabiting the beach 
and saline marshes of the seashore. 
MESOPHYTIC PLANT ASSOCIATIONS. 
These embrace the plant associations confined to a soil and atmos- 
phere of moderate humidity, as grassy swales, canebrakes, the arbo- 
real vegetation of the subtropical forests of broad-leaved evergreen 
trees and shrubs, and the deciduous forest of the lowland with a fresh 
soil rich in humus, never or infrequently overflowed. 
GENERAL CHARACTER OF THE ALABAMA FLORA. 
The flora of Alabama stands in the number of species and varietal 
forms, as well as in the diversity of their characteristic associations, 
unsurpassed among those of adjoining regions. This wealth and vari- 
ety of Alabama’s plant life is easily explained when, on the one hand, 
its area is considered, extending over nearly 5 degrees of latitude, andon 
the other, the diversity of its topographical features, varying from the 
