Myriophyllum (water milfoil) is a genus of about 69 species of freshwater aquatic plants, with a cosmopolitan distribution. The center of diversity for Myriophyllum is Australia with 43 recognized species (37 endemic).These submersed aquatic plants are perhaps most commonly recognized for having elongate stems with air canals and whorled leaves that are finely, pinnately divided, but there are many exceptions. For example, the North American species M. tenellum has alternately arranged scale like ...