This lifeform is found in Europe. This lifeform is found east of the Continental Divide in North America. This lifeform is found in freshwater such as lakes or rivers. This lifeform is locally common in suitable environments.

Water-weed or American Elodea (Philotria canadensis to Elodea canadensis) is found from Quebec west to Minnesota and south to Virginia. With the large amount of boat trailing traffic in North America, this species is now found over a wider range. The verticillate (whorled) leaves are in groups of 3's or 4's, but the lower ones can be in groups of 2's.

Elodea genus was originally native to North America and subtropical South America.  However,  this genus is now found over a much wider range. There are 12 species of aquatic freshwater leafy herbs in this genus with whorled or opposite leaves..   There are four species established in greater North America.

Hydrocharitaceae family contains about 90 species distributed in 16 different genera. The Vallisneria and Elodea genera are included herein, but they have sometimes been placed in their own family. There are 19 species in 11 genera now established in greater North America.

Order Helobiae is a mixed assemblage of mostly aquatic plant families. Included here are the pondweeds, Sagittaria, eel-grass, and water plantains.

Monocots are a large group of plants usually characterized by having leaves with parallel veins and a seed with a single shell. Most flowers are created with multiples of three. In  the older botany texts, the Monocots were considered more primitive than the Dicots. However, many recent authors have placed the Monocots as an offshoot of the primitive Dicots. Here they are placed before the Dicots.

Seed plants (Phylum Embryophyta) are generally grouped into one large phylum containing three major classes: the Gymnosperms, the Monocots, and the Dicots. (Some scientists separate the Gymnosperms into a separate phylum and refer to the remaining plants as flowering plants or Angiospermae.)

For North American counts of the number of species in each genus and family, the primary reference has been John T. Kartesz, author of A Synonymized Checklist of the Vascular Flora of the United States, Canada, and Greenland (1994). The geographical scope of his lists include, as part of greater North America, Hawaii, Alaska, Greenland, Puerto Rico, and the Virgin Islands.

Kartesz lists 21,757 species of vascular plants comprising the ferns, gymnosperms and flowering plants as being found in greater North America (including Alaska, Hawaii, Greenland, Puerto Rico and the Virgin Islands).

There are estimates within the scientific world that about half of the listed North American seed plants were originally native with the balance being comprised of Eurasian and tropical plants that have become established.

Plant kingdom contains a large variety of different organisms including mosses, ferns, and seed plants. Most plants manufacture their energy from sunlight and water. Identification of many species is difficult in that most individual plants have characteristics that have variables based on soil moisture, soil chemistry, and sunlight.

Because of the difficulty in learning and identifying different plant groups, specialists have emerged that study only a limited group of plants. These specialists revise the taxonomy and give us detailed descriptions and ranges of the various species.  Their results are published in technical journals and written with highly specialized words that apply to a specific group.

On the other hand, there are the nature publishers. These people and companies undertake the challenging task of trying to provide easy to use pictures and descriptions to identify those species.