Remarks: Analysis of the cell size of Netrium digitus (see plot) reveals that Dutch material fall into three groups: a group with breadths of approx. 30 μm, a group with breadths of 40-50 μm, and a group with breadths of >60 μm. The length of the cell increases somewhat proportionally with the breadth. Besides this difference in size there appears also a variation in cell outline and a difference in the amount of ridges of the chloroplast, which can vary between 4 and 8. This is subject to further examination.