FREE INSTITUTE OF SCIENCE 
VEGETATION OF SOUTH FLORIDA 
75 
that this chapter is written, but merely to give a detailed account of the 
general geographic distribution of the mangrove swamps, as well as a few 
points which the conditions of growth in Florida emphasize as important addi- 
tional facts. 
On the east coast of the state the northern limit of the red-mangrove, 
Rhizophora mangle L., which is the most characteristic mangrove of Florida, is 
approximately 27° 15” N. The last trees of this species growing separated by 
considerable intervals from each other were seen along both banks of the St. 
Lucie River at Stuart. On the west coast, the mangrove vegetation does not 
extend beyond Tampa Bay at latitude 28° N., so that the northern limits on 
both the east and west coasts of southern Florida approximate the boundary 
which the writer has set as that of this monograph. The mangrove vegeta- 
tion extends along the coast in the quieter water of the lagoons, the rivers, 
and the salt estuaries rarely exposed to the full force of the ocean surge.* In 
the enclosed bays, it gradually encroaches upon the shallow water until in the 
Whitewater Bay region of southwest Florida, we probably have an open shallow 
bay almost completely invaded by mangrove trees, which have formed islands 
separated by tortuous and labyrinthine channels of tidal salt water. Theaction 
of these trees in advancing the shore line has been described by a number of 
botanists. On the immediate east coast, the mangrove fringe is best seen along 
the shores of Bay Biscayne. It extends up the Miami River to where the river 
forks into a north and a south branch. (Plate I, Fig. 2.) Here observations 
made with the hydrometer indicate that fresh water prevails. Many of the 
lower flat keys, or mud banks, of the chain of islands extending to Key West are 
covered with mangrove trees, notably the red-mangrove, Rhizophora mangle 
L., with strong prop roots, and the black-mangrove, Avicennia nitida Jacq., 
with asparagus-like roots the thickness of the little finger. Such low flat trees 
with intricately crossed roots are important agents in fixing the muddy bottom, 
and it has been suggested to plant these trees along the new embankments of 
the “oversea” railroad to Key West to prevent the wash of the waves and the 
undermining of the banks. 
Mangrove vegetation was noted along the following Florida keys: 
Card Sound is mangrove fringed and so is Barnes Sound, as seen in crossing 
from the mainland to Key Largo via the drawbridge over Jewfish Creek. 
Blackwater Sound is surrounded by the mangrove formation. The northern 
* On good authority, it occurs on the ocean side of Virginia Key and Key Biscayne. 
