a. Electron microscopic picture of a cross-section through collenchyma cells of Curcubita leaves after removal of non-cellulose parts and fixation with permanganate. This treatment dissolves the middle lamella, so that the cells splay. The single lamellas run around the cells like rings. In 'thin' parts of the wall are they closer together, while the distances between them are larger in 'thick' parts. Encrustations of other substances like hemicellulose and others cause the thickening. The number of lamellas stays constant.

b. Electron microscopic picture of a cross section through a neighbouring epidermis cell of Curcubita leaves. The lamellas consisting of cellulose change continuously to the periclinal walls. Lamellas on top of each other alternate by 90 degree. In certain areas is an orientation vertical to the plane of the image predominant (B. P. DESHPANDE, 1976).