This lifeform is found widely in Africa. This lifeform is found widely in Eurasia. This lifeform is found widely in the Indo-Australian region. This lifeform is widespread in North America. This lifeform is found widely in the New World tropics. This lifeform is found in freshwater such as lakes or rivers. This lifeform is widespread, but not common.

Horned pondweed (Zanichellia palustris) is found widely in both the Old and New World. This is a freshwater species that can survive in somewhat brackish water.

Zannichellia genus (horned pondweed) contains a single species.  This species is found almost worldwide.

Pond Weed Family (Potamogetonaceae) is a small family of marine and freshwater plants. Older works show this family with less than ten genera and about 125 species.

In older works, this family was called either Potamogetonaceae or Zannichelliaceae. Griffiths now shows only two genera and 90 species in the Potamogetonaceae family. Part of the reason for this difference is that some modern works separate the Zanichella genus into its own family, Zannichelliaceae, which now contains four genera and seen species.

Another confusing issue is that some modern works separate the Ruppia genus into its own family, Ruppiaceae.

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.