4) *‘Heavy pollen grains. . . rarely are found in sedi- 
ments in front of the coastline in any appreciable per- 
centage. Lighter pollen grains are carried seawards more 
easily and may be sedimented at considerable distance 
from the shore. ~ 
5) ‘The Fungi spore content is in general highest in 
the swamp and forest area behind the coast-line and 
ranges between 10 and 100% of the pollen sum, although 
both higher and lower values may occur (0-500%). In 
the Mangrove belt the percentages are usually relatively 
low, ordinarily varying between 3 and 10%. Ina zone in 
front of the coast percentages are generally low (1-38 ), 
and spores of this type are not found farther offshore.” 
Although Muller's and van der Hammen’s conclusions 
‘annot necessarily be assumed to represent conditions 
along the Central American coasts, they provide a ten- 
tative framework for interpretation of the Chiapas sedi- 
ments. Pertinent palynological data from these sediments 
are summarized in Table I. The relationship of Rhizo- 
phora pollen to total pollen content of the sediments is 
represented by “‘percent Rhizophora pollen.” *‘*'Total 
Rhizophora’ constitutes the sum of all Rhizophora types 
as well as those with uncertain affinities. In an attempt 
to gain more detailed ecological information from the 
total Rhizophora category, it was divided into three 
groups. The R. Mangle-type which, as established by 
ecological studies of modern mangroves, represents pol- 
len of the species occupying a more saline habitat ; R/izo- 
phora spp. (R. racemosa-type and R. Harrisoni-ty pe) 
which represents pollen of the species living in less saline 
(brackish and fresh) habitats; and RAtzophora with un- 
certain affinities. The percentage relationship of each 
of the first two groups to the total Rhizophora pollen, 
therefore, gives a possible indication of a more saline or 
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