include the 2. brevistyla-type, as none were recognized 
in this fossil assemblage. Pollen 12-24 mw. Grains are 
generally ill-formed, tending to crumple easily. Shape, 
size, and sculpturing very variable. 
Although pollen of all of these species of Rhizophora 
is quite similar and pollen of each species shows morpho- 
logical variation, the species can be separated to some 
extent. Pollen of R. Mangle is quite distinct from that 
of all the other species except some grains of R. samoen- 
sis. ‘Typical, well-formed pollen of &. samoensis is also 
distinct from that of the other species, with the excep- 
tion of some grains which, as stated above, may be con- 
fused with those of R. Mangle. Crumpled grains of RP. 
samoensis are similar to some grains of R. Harrisoni. 
Pollen of &. racemosa is distinctive in being oblate- 
spheroidal, and thus cannot be mistaken for pollen of any 
of the other types, except for that of some grains of 
ht. Harrisonu. Modern pollen of R. Harrison has not 
been abundantly available. In order to determine 
whether the pollen of AR. Harrisoniu is distinctive and 
clearly distinguishable from the other species, much more 
flowering material is needed. In addition, further taxo- 
nomic work is needed on the entire genus to determine 
if the presently disputed species boundaries can be more 
clearly defined. Until such work is completed, it will 
remain somewhat hazardous to make species determina- 
tions of fossil RAizophora grains on a statistical basis. 
Fossil Rhizophora Pollen 
On the basis of morphology as described above, the 
fossil Rhizophora pollen has been divided into two maior 
groups which reflect not only the pollen morphology but 
also the division of the species of Rhizophora into two 
groups occupying somewhat different habitats. The first 
is composed of typical RP. Mangle-type and P. samoensis- 
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