For example, fibriform cells are not considered to be flow cells.
Strength in mechanical cells of wood is conferred by helical cellulose microfibrils in a lignified background in secondary walls, but also, quite significantly, by cementing substances between fibriform cells.
Thus, the interruption of fibriform tissue by rays would decrease strength.
The same indefinite longevity of fibriform cells can be cited for Nerium oleander of the Apocynaceae (Fig.
The idea that ontogenetic changes in ray, axial parenchyma, and tracheary elements (fibriform cells, including tracheids; vessel elements) can be shifted toward herbaceous modes or woodier modes (Carlquist, 1962, 2009; Carlquist, 2013a, b) places us in a new perspective.
Raylessness in this case may be considered an initial emphasis on mechanical strength of fibriform cells over parenchyma cells designed for radial flow, followed by a balance between the two.