Central and northern South America. The resin is ob- 
tained either from wounds in the bark and wood, or as 
hardened masses in the soil around the base of the tree. 
Amyris and Styrax produce only moderate amounts of 
resin. Bursera simaruba and Calophyllum brasiliense are 
often associated with Hymenaea, Amyris and Styrax. 
Thus, there are five resin-producing trees that occur along 
rivers in low, hot country in habitats that could be con- 
sidered excellent sites for supplying resin capable of be- 
coming incorporated in the geologic record. 
Bursera excelsa (HBK.) Engl., B. bipinnata Engl., 
Pistacia bipinnata HBK. and Guaiacum sanctum IL. 
grow principally in the Selva Baja Caducifolia, although 
these species of Bursera do appear in the Selva Alta 
Subcaducifolia. The narrow belt of Selva Baja Caduci- 
folia, which occurs along the coast today, might well 
provide a favorable habitat for preservation of the resin. 
These species of Bursera and Pistacia produce consider- 
able quantities of resin spontaneously, but large amounts 
of resin from Guaracum are obtained primarily by artifi- 
cial treatment of the heartwood. 
The numerous species of pine have to be taken into 
account as a possible source of amber. Most of the pines 
here, however, occur at relatively high elevations, and 
hence the resin would have to be carried an appreciable 
distance to a lowland environment of sedimentation. 
Pinus oocarpa Scheide has the widest distribution, occur- 
ring from 350 to 3000 m. in somewhat dry localities. In 
more humid sites there also are P. pseudostrobus Lindl. 
and P. tenuifolia Benth., whereas at higher altitudes P. 
montezumae Lamb and P.teocote Schl. and Cham. become 
more abundant. Also at higher elevations, where pre- 
cipitation likewise is high, P. strobus var. chiapensis 
Martinez and P. ayacahuite Eht. occur. Pinus strobus 
is likewise found in association with Liquidambar styraci- 
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