Simply begin typing or use the editing tools above to add to
this article. Once you are finished and click submit, your
modifications will be sent to our editors for review. vascular
system in trees ...tapering cells that give rise to all cells of
the vertical system of the secondary phloem and xylem (secondary
tracheary elements, fibres, and sieve cells and the associated
companion cells). The ray initials are isodiametric cells—about
equal in all dimensions—and they produce the vascular rays,
which constitute the horizontal system of secondary tissues;
this horizontal system... ...fusiform initials are long cells
that give rise to the axial (longitudinal) system of vascular
tissue. The cells of the axial system are arranged parallel with
the long axis of the tree trunk. The ray initials form the
radial system of the bark and wood. These initials are more
squat in shape and produce cells oriented perpendicular to the
axial cells. What made you want to look up "ray initial"? Please
share what surprised you mo