Compared to animal cells, plant cells are typically non-spherical, which may bias morphometric and fluorimetric analyses, including flow cytometry and other approaches used in the study of cellular biodiversity. The morphometric study of cotyledonary cells may serve to distinguish between genotypes, as cell shape is clearly an important issue when assessing flour quality and seed digestibility by animals, being affected by the surface and volume of particles. We devised a shape coefficient that resolves these difficulties with pea (Pisum sativum L.), and may find general applicability in cytological studies and for the characterization of biodiversity patterns.