This lifeform is found in the SW USA (Texas, New Mexico, and Arizona).

Tall mercury (Ditaxis aphoroides to Argythamnia aphoroides) is endemic to Texas. The densely villous nature of this species aids in its identification. Ditaxis mercurialina, sometimes also called tall mercury, is considered a different species.

Ditaxis genus (changed to Argythamnia) is native to the warm and tropical regions of the world.  These are herbs or shrubs.  The leaves are usually alternate and entire (rarely toothed.) There are 17 species and seven subspecies of the genus Argythamnia living in greater North America.

Spurge Family (Euphorbiceae) is a family of approximately 7,000 to 8,000 species of shrubs, herbs, and trees. There are maybe 2,000 different species in the Euphorbia genus. A common characteristic of most members of this family is a white sticky sap (latex) that will appear whenever a cut is made. Included in this family is the Hevea genus which is the source for natural rubber. Many of the species in this family are stem succulents that can withstand considerable periods of low moisture. For a more detailed analysis of this family refer to the Encyclopedia of Succulents by Rowley. There are 372 species arranged in 46 genera growing in greater North America.

Geranium Order (Geraniales) is a large order composed of many  different families. Included here are the Geranium, Oxalis, and Citrus groups.

Dicots (Dicotyledoneae Class) are the predominant group of vascular plants on earth. With the exception of the grasses (Monocots) and the Conifers (Gymnosperms), most of the larger plants that one encounters are  Dicots. Dicots are characterized by having a seed with two outer shell coverings. Some of the more primitive Dicots are the typical hardwood trees (oaks, birches, hickories, etc). The more advanced Dicots include many of the Composite Family flowers like the  Dandelion, Aster, Thistles, and Sunflowers. Although many Monocots reach a very high degree of specialization, most botanists feel that the Dicots represent the most advanced group of plants.

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.