any palynological interpretation of mangrove vegetation 
rests likewise primarily upon reconstruction of conditions 
indicated by these two genera, and particularly by Rhizo- 
phora, the most abundant pollen source. More studies 
on present-day pollen sedimetation are needed before 
anything other than very general ecological conclusions 
may be reached. However, the various species of Rhizo- 
phora do provide significant, although considerably 
limited, ecological data. ‘The abundant incorporation of 
Rhizophora pollen into sediments is a result, in part, of 
the manner in which the pollen is released. Rhizophoras 
produce a large amount of small light pollen which is 
released into the bud before anthesis and much of which 
is retained by the hairy petals and is not blown away or 
carried by insects when the bud opens. Both the anthers 
and the petals fall from the trees into the water within 
two or three days after the bud opens, carrying the pol- 
len directly into the water (Guppy, 1906). 
Rhizophoras are well adapted to growth in regions of 
extreme tides, because of the ability of the viviparous 
seedlings to root rapidly and to withstand inundation. 
Under these tidal conditions, it forms broad bands along 
the western coast of South America. Where tides are of 
low amplitude, for example along the north coast of 
South America, Rhizophora may be scarce or absent 
along the coast. 
Rhizophora Mangle (red mangrove), the most wide- 
spread species, is a pioneer which establishes itself suc- 
cessfully on unconsolidated silt if its seedlings are left 
unflooded for as little as 48 hours. It appears to be the 
most salt-tolerant of the New World mangroves, occur- 
ring both on the open sea shore (if protected from ex- 
treme wave action) and in areas where salt concentrations 
in the soil are abnormally high due to periodic flooding 
and evaporation (Guppy, 1906; Savory, 1953; Jonker, 
[ 306 ] 
