Bignonia TS Stem

The cross section illustrated here, shows part of a Bignonia stem, which is undergoing secondary growth.

The stem is markedly angular, and mechanical support tissues are found, particularly collenchyma, beneath these angles. The outer cortex is photosynthetic, with two to three layers of  chlorenchymatous cells visible. The external phloem (EP) is capped by sclerenchymatous fibres (S).

The secondary xylem has formed a continuous ring, and this contains some conspicuous large-diameter vessels (2X). The primary xylem (PX) contains some parenchymatic elements and internal phloem (IP) which forms part of inverted medullary vascular bundles in this species. The pith is parenchymatous.

This stem is classified as being anomalous