Bio 430

Contemporary Circumscription Compared with A Utah Flora 4th ed.

Bio430

Euphorbiaceae

No differences at the family level, but considerable rearrangement of species among genera has occurred. The genus Euphorbia is very large; A Utah Flora segregates spreading plants with C4 photosynthesis into the genus Chamaesyce, but these plants belong monophyletically within Euphorbia.

Key Features

Monoecious or dioecious plants. Latex bearing species with pseudanthia (called cyathia) composed of a single female flower surrounded by few to many male flowers of one stamen each; glands surrounding these clusters may have petaloid appendages. Non-latex bearing species have ‘normal’ imperfect flowers with a calyx, but petals may or may not be present. The three stigmatic lobes are often further divided toward their tips.

Castor Bean leaves

Stillingia paucidentata, photographed off Hwy 395 in southern California "pretty much in the middle of nowhere"

Stillingia paucidentata; this species in monoecious with a few female flowers at base of inflorescence near leaves, and many male flowers above

Stillingia paucidentata; glands similar to those observed on Euphorbia cyathia appear on the side of male flowers

Croton - a desert shrub from near St. George Ut; this species is dioecious, with this photo from a plant bearing male flowers. The plant is densely covered in stellate hairs

Croton - young female flower

Croton - maturing ovary

croton seeds; the inner pericarp is elastic and when it dries, it will twist rapidly causing the seeds to be flung far from the parent plant. The carnuncle is visible on the upper tip of seed on right.

Euphorbia albomarginata, near St. George, UT

Euphorbia albomarginata

Euphorbia maculata, yard weed, Salem UT

Euphorbia maculata with latex at damaged points on plant

Euphorbia maculata, yard weed, Salem UT

Euphorbia maculata; ovaries (female flowers) become erect as they fully mature prior to dehiscence

Euphorbia maculata seeds

Euphorbia serpyllifolia, yard weed in Salem, UT

Euphorbia serpyllifolia; cyathia glands have white, petaloid appendages, many keys say appendages are narrower than the gland they are attached to, but that isn't my experience.