Young leaves have abundant trichomes that become confined to the petiole
base as the leaf ages. While the leaves have no midrib, dichotomous venation
with regular, numerous branching parallel veins arises from two vascular
strands within the petiole. Stomata occur almost exclusively on the lower
surface of the leaf. The epidermis of the upper and underside of the leaf consists
of undulated, irregular, mostly long extended cells. In the cross-section, the
epidermal cells appear nearly isodiametric and from above appear to be slightly
undulated, with the upper cells appearing larger. The outer walls of the epidermal
cells are covered with a more or less thin layer of cuticle. In the area of
vascular bundles there are remarkable long extended narrow cells with slightly
undulated walls. Numerous druses of calcium oxalate occur near the vascular
bundles (