Fig. 4.1-7. Transverse section of stem of cosmos (Cosmos). This is lamellar collenchyma, a type that is not too common. The outermost two layers of collenchyma cells, along with the epidermis cells, are brick-shaped and fit together in regular layers. This regular pattern of cell shape and layering results in the thickened corners also being arranged in a regular pattern of layers – the red-stained bands that run parallel to the epidermis. The cells of the third and fourth layers of collenchyma do not have such regular sizes and shapes and thus do not fit together in smooth, uniform layers. As a consequence, their thickened corners are not aligned and do not form lamellar collenchyma.