Presented below is a photomicrograph of the leaf of Elodea canadensis, more commonly known as the North American elodea. Elodea is an underwater plant, with species native to both North and South America.

Elodea was once commonly used in aquariums. Unfortunately, some of these plants have been dumped into lakes and ponds in non-native regions around the world and have become nuisance species because their virtually uncontrollable growth. The plants form dense mats that choke out native aquatic plants, provide poor habitat for fish, and interfere with aquatic sports.