The Caryophyllidae
Family Overview - The Polygonales
Polygonaceae - the Buckwheat Family
Diversity:  A family of 30 genera and about 1,000 species of herbs (mostly) and some shrubs and (rarely) trees.  The ethnoflora includes, rhubarb (Rheum rhaponicum), a plant grown for its petioles, buckwheat (Fagopyrum esculentum)

Distribution:  Mostly centered in Northern and temperate parts of the World.  The Texas flora includes 5 genera and 58 species with species of 4 genera endemic to the State.

Floral structure:


Significant features:  Most species of this family, with the exception of the large genus Eriogonum (false buckwheat) show a unique vegetative feature at the node.  A modified stipule encloses the node for form a sheathing structure known as an ocrea.  The nodes also (like the Caryophyllaceae) tend to be swollen and this feature is signaled by the Genus name Polygonum which translates to 'many kneed', a reference to the swollen nodes.  The flowers are small, perfect (usually) and either show a bi- or uniseriate calyx that often continues to develop after anthesis (accrescent) to produce a winged enclosure for the fruit, a trigonal (three-sided) or lenticular (lens shaped) achene.
 

Polygonum - nodes and ocrea
 

Node of a sea grape (Coccoloba uvifera) with ocrea
 

Eriogonum longifolium (the largest genus with 250 species) - flowers
 

kohler imageRheum officinale from Kohler's Medicinal Plants

Rumex venosus in fruit (left) and a single, accrescent, winged sepal with the trigonal achene (right)

 

More information on the Polygonaceae

Return to the Biology 301 homepage, or the Caryophyllidae page
last updated/mirrored 7-27-2007 by MDR