This lifeform is found east of the Continental Divide in North America. This lifeform is scarce.

Walnut (Genus Juglans) contains about 15-20 species of trees native to North and South America and Eurasia characterized by their compound leaves with pairs of opposite lanceolate leaflets.  Six of those species are native to the United States, and several others (including the English walnut, Juglans regia) are considered established here.  The wood of several species is considered very valuable.  The fruit is contained in a larger husk that is not easily opened.

Juglandaceae Family is the sole family in the Juglandales  Order. It contains many species of trees with very valuable  wood. The hickory and walnut genus are both in this family.

Following is a list of the thirteen hickory species found in the United States (* those 7 discussed here):

  *Carya alba (=tomentosa)        Mockernut         East USA
   Carya aquatica                 Water Hickory     South USA
   Carya carolinae-septentionalis Southern Shagbark SE USA
  *Carya cordiformis              Bitternut         East USA
   Carya floridana                Scrub Hickory     SE USA
  *Carya glabra (3 varieties)     Pignut            East USA
       var. glabra (=microcarpa)  Small Fruited     East USA    
       var. megacarpa(=austrina)
       var. hirsuta(=leiodermis)  Swamp Hickory     Louisiana
  *Carya illinoinensis            Pecan             SC USA
  *Carya lacinosa                 Shellbark         Central USA
   Carya myristiciformis          Nutmeg Hickory    Local S USA
  *Carya ovalis                   Sweet Pignut      East USA
  *Carya ovata                    Shagbark          East USA
   Carya pallida                  Sand Hickory      SE USA
   Carya texana                   Black             SC USA

Following is a list of the nine species of Walnuts found in the United States: ( * = those 5 discussed here):

  *Juglans ailanthifolia        Japan               Introduced
    Juglans californica          California          S. Calif.
  *Juglans cinerea              Butternut           North USA
    Juglans hindsii              Hinds Walnut        Local Calif.
    Juglans jamaicensis
    Juglans major                Arizona Walnut      SW US & Mex.
  *Juglans microcarpa           Little Walnut       Texas
  *Juglans nigra                Black Walnut        E. USA
  *Juglans regia                English Walnut      Introduced

Juglandales Order contains the Walnuts and the Hickories. The ovary is one-celled, and the flowers are unisexual. (The male flowers of walnuts, for example, are found in catkins, and the female flowers in terminal clusters.)

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.