Euphorbia subgroups

There are six major groups in Euphorbia: sect. Anisophyllum, sect. Crepidaria, sect. Alectoroctonum, sect. Poinsettia, subg. Esula, and sect. Nummulariopsis.

Section Alectoroctonum (synonymous with the genera Agaloma and Tithymalopsis) represents a group of herbaceous and succulent plants with primarily alternate leaves that are symmetric at the base and entire. The group also has petaloid appendages. It includes plants like Candelilla (Euphorbia antisiphylitica), Snow on the Prairie (Euphorbia marginata), Flowering Spurge (Euphorbia corollata), Cliff Spurge (Euphorbia misera), and many others.

Section Anisophyllum (synonymous with genus Chamaesyce) represents the group of herbaceous plants with opposite leaves with unequal bases, dorsi-ventral stems, interpetiolar stipules, and C4 photosyntheis. The group includes the mat-forming plants like Spotted Spurge (Euphorbia maculata), Prostrate Spurge (Euphorbia prostrata), Whitemargin Sandmat (Euphorbia albomarginata), and many others. For a full list of species in the US, go here: http://www.inaturalist.org/lists/459735-Euphorbia-of-the-United-Statess-Check-List?q=&taxon=506796&observed=any&rank=species&taxonomic_status=active

Section Crepidaria (synonymous with genus Pedilanthus) represents a group of succulents (similar to Candelilla) with zygomorphic (bilaterally symmetric) cyathia. In the US, it is only known from cultivation and potentially a small population in southern Florida. This group includes Slipper Plant (Euphorbia lomelii) and Devil's Backbone (Euphorbia tithymaloides).

Subgenus Esula (synonymous with genus Tithymalus) represents a large group of mostly herbaceous plants that typically have terminal pleiochasia (inflorescences), alternate stem leaves, and opposite inflorescence leaves. Widespread and represented by many species. The group includes plants like Petty Spurge (Euphorbia peplus; not to be confused with E. peplis), Cypress Spurge (Euphorbia cyparissias), Caper Spurge (Euphorbia lathyris), and Leafy Spurge (Euphorbia esula).

Section Poinsettia (synonymous with genus, well, Poinsettia) represents a group of herbaceous plants with large bract-like leaves that are often colorful. The cyathia usually have 3 or fewer glands per cyathium but a couple species have more. The cyathia are also held in inflorescences that terminate the apices of stems. The group includes Poinsettia (Euphorbia pulcherrima), Green Poinsettia (Euphorbia dentata), Painted Leaf (Euphorbia cyathophora), and others.

Section Nummulariopsis represents a small group of erect herbaceous plants in the Southeastern US that appear superficially similar to the narrow-leafed species in sect. Alectoroctonum or like a small, linear-leafed species of subg. Esula. The group includes Euphorbia inundata, E. floridana, E. rosescens, and E. telephioides.

Posted by nathantaylor nathantaylor, January 25, 2017 21:56

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Thank you Nathan, again vey helpful!

Posted by dale_denham_logsdon over 2 years ago (Flag)

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