The form of the ray
cells is best represented in radial section.
r radial t tangential q transversal
h high me medium mo modest
All the ray cells are procumbent (rectangularly formed and the longest
axis radially oriented). Marginal cells may be slightly modified but
still procumbent in form.
Heterogeneous rays, type I: Procumbent cells in the interior of the rays, a one cell wide
band of more or less square cells bordering the ray. This type of
ray is frequent and represents the transition between homogeneous
rays and truly heterogeneous rays.
Heterogeneous rays, type II:
Procumbent cells in the interior of the rays, one row of upright cells.
Heterogeneous rays, type III:
Procumbent cells in the interior of the ray, several rows of upright
cells on the ray border.
Small, numerous pits in ray-vessel intersections.
Particularly large ray-vessel pits.
Ray-vessel pits average size.
Development of a secondary ray:
It is necessary to examine several rays, as in certain species the
form of secondary rays differs in the initial stage and the final
stage (in the initial stage the cells are frequently upright).