The Vessel
The vessel: the key transport corridor for sap through
most woody angiosperms. Seen in 2D, it often just
looks like a bigger ellipse than the surrounding ellipses
of other cells on a cross-sectional slide made from a
woody stem. View a vessel under an electron micro-
scope, though, and you can see each vessel element
that makes up the vessel's length, which is similar
to small sections of perforated pipe, cut on a slant,
aligned to each other to provide a conduit for sap.
From looking at images of vessels like this, first you learn
just how perforated a vessel element is—leaking sap into
all adjacent areas is a key role of these perforations—
then you realize the need for the mechanical support of
the adjacent wood fibers, as a cell wall so full of holes is
not going to be self-supporting. This and the next image
are from the wood of common hazel (Corylus avellana).
urban-forestry.com 23
Wood Microscopy,
Senior Lecturer in Arboriculture at
Myerscough College in Lancashire, England
