Anatomy of Interfascicular Fibers in Stems of the Wild Type and the fra2 Mutant.

(A) and (B) Cross-sections of the stems of the wild type (A) and fra2 (B) showing the presence of interfascicular fibers. Insets show enlarged fiber cells. It is evident that the fiber cell wall in the wild type (A) is much thicker than that in fra2 (B).

(C) and (D) Longitudinal sections of the stems of the wild type (C) and fra2 (D). Fiber cells in fra2 (D) are much shorter and wider than those in the wild type (C). Arrows mark the ends of a fiber cell.

C, cortex; e, epidermis; if, interfascicular fiber; pi, pith; x, xylem. Bars in (A) to (D) = 55 µm; bars in insets in (A) and (B) = 28 µm.