Fig. 3.—Transverse section of the petiole

magnified 30 diameters.
a, the epidermis of the petiole, composed of a single layer of cells which are thickened and slightly cutinized upon their exterior surface, and presenting a fringed appearance;
b, several layers of collenchyma or thick angled cells underlying the epidermis;
c, intercellular spaces in the parenchyma;
d, parenchyma tissue surrounding the vasal bundle;
e, crystals of calcium oxalate in the parenchyma cells closely encircling the vasal bundle;
f, phloem portion of the vasal bundle facing the lower surface of the leaf;
g, xylem portion of vasal bundle showing the radial arrangements of ducts.

This image is from Eriodictyon Glutinosum in the November issue of the American Journal of Pharmacy, 1895.

Fig. 3.—Transverse section of the petiole