vascular bundles (fibrovascular bundles) of palm fiber are composed of vascular tissue
reinforced by a cap of thick-walled sclerenchyma cells. The
large, water conducting xylem vessels are accompanied by
much smaller water conducting tracheids. Air spaces are sometimes
found in the vascular tissue area as well. The food conducting
phloem tissue is found between the vessels and the bundle
cap. Sieve tube members associated with companion cells make
up the phloem tissue. Sieve tube members transport the products
of photosynthesis through the plant. Companion cells are
parenchyma cells that develop from the same mother cell as
the sieve tube member. The companion cell helps transport
materials in and out of the sieve tube member. A space occupies
the area in which the phloem would have been
Phloem is only rarely preserved. Visit our Texas Gallery
in the Oligocene section of our website to see vascular bundles
with preserved phloem.
The bundles caps
in a ground mass of parenchyma cells. The vascular
bundle pictured above measures 1,400 micrometers tall and
a little under 900 micrometers at its widest point. The vessels
measure a little over 200 micrometers in diameter. Visit
the Louisiana Gallery (slide 20) in the Oligocene section
of our website to see a sequence of photos that zoom in to the
individual vascular bundles can be seen in this fossil palm
(genus Palmoxylon) specimen from Wyoming. Each vascular
bundle is surrounded by numerous fibers, which thicken into a cap
shape on one end. The fibers provide structural support. The empty
spaces represent vessels for water conduction and sometimes air
spaces. The phloem tissue would be found between the vessels and
the bundle cap. This image was taken at 40x.
fossil Palmoxylon pictured above comes from the
same location in Wyoming as the previous specimen. Note this
palm has much larger bundle caps in comparison to the vascular
vascular bundles in this trunk of fossil Palmoxylon from
Louisiana exhibit great cellular detail. In some species of palm one can observe fibrous bundles,
which are made of the same cells making up the bundle caps in the fibrovascular bundles.
Fibrous bundles are made of fibers and appear as red and
orange dots in the specimen above. Note the Wyoming specimens
above lack the fibrous bundles. The next image zooms in on a fibrovascular bundle and fibrous bundle at 150x with a Dino-Lite AD7013 MT 5.0 MP. The image was resized in Adobe Photoshop CS6.
The Palmoxylon trunk used to take the images above is pictured below.
cut Palmoxylon specimen from Louisiana
reveals the rod-like structures of the vascular bundles.
This Palmoxylon specimen
from Texas represents a transverse cut (cross-section).
When viewed in cross-section the vascular bundles give
the palm fiber a spotted appearance.
The close-up below
reveals that even the parenchyma ground tissue between
the vascular bundles is well preserved in this specimen.
The bundle caps dwarf the vascular tissue in size. Note
the many small dots, which are fibrous bundles.
The close-up below shows a vascular bundle at 150x and was taken with a Dino-Lite AD7013 MT 5.0 MP. The image was resized in Adobe Photoshop CS6.
Fayette County, TX
above and below illustrate the transition zone between Palmoxylon trunks
and their adventitious roots (Rhizopalmoxylon). In
the image above individual rootlets measure 2 to 3 mm
in diameter. The adventitious
root below measures
mm in diameter.
Palmoxylon with Rhizopalmoxylon
East of Barisan Mountain Range