1959). Its luxuriant growth in such areas as southern 
Florida, however, indicates that it does not always re- 
quire this high salinity. Here, the usual species found 
in more brackish water are absent. 
Rhizophora Harrisoniu, the second most widespread 
of the species, is characteristic of brackish estuaries and 
rivers in West Africa, on both the east and west sides 
of the South American continent and on the west coast 
of lower Central America. The tree forms great expanses 
of tall forest bordering the rivers in Surinam (Jonker, 
1959). 
Rhizophora racemosa is more restricted, the species 
having never been found on the west coast of the Ameri- 
cas. &. racemosa is considered the least salt-tolerant of 
the Rhizophoras, and it is found far up tidal rivers, 
growing together with R. Harrison and beyond the 
range of that species into nearly fresh water. Both Savory 
(1953) and Jonker (1959) consider it the least salt-tolerant 
of the Rhizophora species. 
The species occurring on higher ground within or near 
the mangrove and in fresh-water swamps behind or up- 
stream from the mangroves vary from region to region. 
In the coastal regions of Surinam, Venezuela and British 
Guiana, where Avicennia is the dominant mangrove, the 
region behind the mangrove belt isa complex mosaic of 
vegetation types controlled by local soil and water con- 
ditions. Especially important is the mixed swamp forest 
(including Pachira (Bombax) aquatica and Pterocarpus 
officinalis) which may form extensive stands behind the 
mangroves. ‘There also are often palm swamps; herba- 
ceous swamps, often dominated over great expanses by 
ferns (e.g., Acrostichum aureum); as well as special vege- 
tation types on sandy beach ridges and high natural 
levees. This pattern is very different from that described 
by Cuatrecasas and others for the west coast of South 
[ 807 | 
