Genus of the Week

Week of Feb. 9-15

This page has been created for people who want to learn more about plants, especially in the context of their taxonomy (Latin names, etc.). This is by no means an exhaustive list of all available Web resources on a particular genus.

This week's genus:

Euphorbia: The Spurges

Subclass: Dicotyledoneae
Superorder: Rosidae
Order: Euphorbiales
Family: Euphorbiaceae; The Spurges
Tribe: Euphorbieae
Number of Species: more than 2000
Latin Root: "euphorbea" - named for Euphorbus, physician to King Juba of Mauretania

The most famous species of this genus is undoubtedly Euphorbia pulcherrima, the Christmas Pointsettia, a winter holiday boon for greenhouses everywhere. One species that is quite common in the United States is Euphorbia cyparissias (Cypress Spurge). The bright yellow flowers of E. cyparissias can be spotted along roadsides throughout the sping and summer. The sap of this species (introduced from Europe) as well as the sap of many other Spurges, is caustic and has been blamed for poisoning cattle (Audubon Guide, 1979). According to Heywood (1993), this genus is characterized by an inflorescence termed a "cyathium". A cyathium consists of a female flower surrounded by several male flowers, which are in turn surrounded by a cup-shaped structure and several glands. These glands produce nectar to which flies (mostly order Diptera) are attracted.

Here are a few links to images and descriptions of different Euphorbia species:

Cornell has a page with images of E. pulcherrima, E. helioscopia (Sun Spurge) and E. lactea (Candelabra Cactus)
The Plant Image Database at Texas A&M University has several images of Euphorbia species, including close-ups of cyathiums. Click here and scroll down to the "E's".
The Canadian Poisonous Plants Information System has data for several Euphorbia species. Just click here and scroll down to the "E's". (Destroy the myth that Poinsettias are deadly!)
From the "Botanik online - Themenübersicht" web site in Germany come several great images of the succulent cactus-like species of Euphorbia. And here is an image of E. longispina from The Cactus and Succulent Plant Mall, located in England.
If you are interested in Ethnobotany, you should definitely check this out. The Ethnobot at the Agricultural Information Services web site will tell you every known use for a plant species and which country it originates from. Again, scroll down until you reach the "E's".
For those of you interested in Biochemistry, here is a link to an abstract concerning Cytotoxic Diterpenes from E. poisonii

References:

Heywood, V.H., ed. Flowering Plants of the World. New York, Oxford University Press: 1993.
Neiring, William A. and Nancy C. Olmstead., eds. The Audubon Society Field Guide to North American Wildflowers, Eastern Region. Alfred A. Knopf, New York: 1979.

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