Fig. 4.2-1. Transverse section of petiole of pumpkin (Cucurbita pepo). Collenchyma is common in leaves, located along the top or bottom of the petiole as well as along the largest veins. This is a leaf midrib and there is a narrow band of collenchyma located just below the upper epidermis (it does not extend out into the two halves of the blade). There is a much larger amount of collenchyma along the bottom of the midrib, just interior to the lower epidermis. There are two vascular bundles in the midrib – it is fairly common for collenchyma to occur next to vascular bundles but none is present here.