Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Euphorbiaceae, Spurge or Euphorbias Family

The Euphorbiaceae or Spurge and sometimes Euphorbias Family consist of forbs/herbs although tropical species may be shrubs or trees. Some tropical species resemble certain members of the Cactaceae Family and are often confused with them. Most of the Euphorbs are native to the tropics however many are non-tropical species such as those found in Arizona and the United States. Once again showing Arizona's varied habitats that includes the northern most distribution of several tropical species.

Leaves are mostly alternate although many in Arizona are opposite and have stipules subtending the leaves. An interesting characteristic is that most of the leaves are simple, but compound leaves are always palmate and never pinnate.

Plants are monecious or dioecious and flower configuration is extremely variable. The arrangements and shape of the stipules may be a key characteristic especially in Chamaesyce. Also in the genus Chamaesyce, and other Euphorbs, is a cyathium which is a specialized pseudanthia ("false flower").

The Euphorbiaceae Family has 229 genera with over 6,511 accepted species named. The Plant List includes all but 1 species of the genus Chamaesyce within the genus Euphorbia which now includes 2,031 accepted species

There are several hundred species of Euphorbiaceae in Arizona, the largest genera includes Chamaesyce and Euphorbia.

References:
The Plant List. a working list of all plant species. [accessed May 23, 2015]
http://www.theplantlist.org/browse/A/Euphorbiaceae/
The Plant List. a working list of all plant species. [accessed May 23, 2015]
http://www.theplantlist.org/browse/A/Euphorbiaceae/Euphorbia/
Wikipedia contributors, 'Euphorbiaceae', Wikipedia, The Free Encyclopedia, 9 February 2015, 20:41 UTC,
[accessed 23 May 2015]
Wikipedia contributors, 'Cyathium', Wikipedia, The Free Encyclopedia, 30 September 2013, 02:37 UTC,
[accessed 23 May 2015]
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database – ITIS search