After a brief review on the morphological and biological studies of the pondweed Potamogeton pectinatus L., the dynamic aspect of the development of this species is explained and illustrated. The description of the vegetative organization of Potamogeton pectinatus L. is emphasized, the most impressive point being the diversity in the modes of ramification. A comparison with other monocotyledonous or aquatic plants is given in order to propose an architectural model. Some peculiarities of the species are discussed, in particular the stereotyped behaviour of the organism living in still waters. But the behaviour of a form living in running water was of another kind.