The lower micrograph shows the same section of wood,
but a region father out, produced more recently. Two primary rays are visible
(from just this micrograph, you cannot be certain that they are primary rays –
it is necessary to follow them to the pith), and a secondary
ray is also present. The arrow indicates the point where several
fusiform initials were transformed to ray initials, thus putting an end to
several rows of axial elements and initiating the production of a new ray
instead. |