Chamaesyce capitellata (Engelm.) Millsp.
Family: Euphorbiaceae Synomnys: Chamaesyce pycnanthema (Engelm.) Millsp.; Euphorbia capitellata Engelm.; Euphorbia pycnanthema Engelm.; Euphorbia rusbyi Greene; Euphorbia geminiloba Millsp. Distribution: The type is from Arizona/Sonora border at San Bernardo (by Wright). Arizona, western Texas, Chihuahua, Coahuila, Sonora, Sinaloa, Lower California (Wheeler 1941).; Brewster county (Big Bend area), Texas (Correll & Johnston 1979); northwestern Mexico from Coahuila to the Baja California penninsula and Durango, and the southwestern United States from Arizona to Texas (Steinmann & Felger 1997). Habitat: Hillsides, washes, arid plains (Shreve & Wiggins 1964); Chihuahuan Desert (as E. pycnanthema; Correll & Johnston 1979); Sonoran desert scrub, grassland, thorn scrub, and tropical deciduous forest (Steinmann & Felger 1997). Plants Seen or Cited: No records in New Mexico Natural Heritage Program Database. Two specimens at UNM.
1. E.F. Castetter. 20 August 1955. Hidalgo county, New Mexico. Winkelman's Well, Little Hatchet Mountains.
2. C.B. Carter. 30 August 1936. Pima county, Arizona. North Pima Canyon, Tucson.
Discussion: As the several synonyms indicate, this species is quite polymorphic within its broad range in the Chihuahuan and Sonoran Deserts. It was not listed in Wooton & Standley (1915). Although this plant may be rare in New Mexico, it is common and widespread outside of the state. I recommend that it should not be given special consideration in New Mexico, and that it should remain on L4. Literature cited: Correll, D.S. and M.C. Johnston. 1979. Manual of the vascular plants of Texas, second printing. The University of Texas at Dallas, Richardson, TX. (page 975-976) Shreve, F. and I.L. Wiggins. 1964. Vegetation and flora of the Sonoran Desert. Two volumes. Stanford University Press. (pg. 823-824) Steinmann, V.W. and R.S. Felger. 1997. The Euphorbiaceae of Sonora, Mexico. Aliso 16(1):1-71 (page 40) Wheeler, L.C. 1941. Euphorbia subgenus Chamaesyce in Canada and United States exclusive of southern Florida. Rhodora 43:96-286 plus many plates. Wooton, E.O. and P.S. Standley. 1915. Flora of New Mexico. Contributions from the United States National Herbarium, Smithsonian Institution, Government Printing Office, Washington, D.C. Information Compiled By: David L. Bleakly, 1998