Front Range Seed Analysts
1991 Seed Forum Volume 5 Number 4
SEEDS OF THE FRONT RANGE: POLYGONACEAE: Part 1
Written by Jim Bruce
The Polygonaceae, known as the dock family, is common and widespread. Worldwide! this family consists of 40 genera and over 1000 species. In the United statesi the family is represented by 15 genera and approximately 165 species. This large family of mainly herbaceous plants are easily recognized by a few family traits.
The family name, Polygonaceae, means "many knees" and describes one of the basic, distinguishing characteristics: the swollen, knee like nodes.
This family includes a number of economically important crops including buckwheat and sorrel. A number of species of the genus Rheum, such as rhubarb and the sea grape (which supports a local jelly industry where it is found), have economic significance also. Polygonum tinctorium is used in the making of blue dyes. Ornamental species include Antigonon leptopus, Russian vine (also known as mountain rose vine) , Polygonum affine, and P. companulatum. The latter two are used as border flowers.
Foraging for wild edible plants in the Polygonaceae family can be rewarding as well. Leaves, roots and seeds can be eaten. The leaves of Rumex crispus, curly dock, can be used as a potherb and those of R. acetosella, sheep's sorrel, can be used in salads. Plantago viv.1ioarum and P. bistoroides have edible roots and I have f ound that the achenes of R. crispus are a wonderful replacement for buckwheat in pancakes.
Many members of this family are be used in folk medicine. The acrid juice common in the species of the Polygonaceae is a powerful astringent. This is especially true of bistort, whose root is used as a curative f or diarrhea. Lady I s thumb, P. Persicaria can be used for stomach pains and cramps, while R. crispus and R. obtusifolia may be used as a poultice for healing cuts and made into a tea for an ulcer tonic. many members of the Polygonum and Rumex genera can also serve as diuretics.
The Poligonaceae have alternate leaves which are simple and entire and have stipules which unite at the base into an ocrea (tubular sheath) . This ocrea clasps around the node, giving the "many kneed" look which is so common to the plants of this family.
The inflorescence is mainly racemose (clustered), but may be cymose (all floral axes terminate in a single flower). Two types of flowers exist. The first is cyclic, type I flowers, which consist of a calyx in two whorls of three sepals each. The second acyclic, type II flowers which contain one whorl of five sepals with the inner and outer segments fused into one large sepal. Both are bisexual and actinomorphic.
The family is divided into three subfamilies. The Rumicoideae contains members with cyclic flowers. The leaves may or may not have an ocrea and seeds have a mottled or ruminate endosperm.
The Polygonoideae subfamily has acyclic flowers, an ocrea and the endosperm is not mottled. The Coccoloboideae subfamily has acyclic flowers and ocrea and the endosperm is mottled.
Many common and noxious weeds are found within this family. The seeds of the Polygonaceae are of particular importance to seed analysts because many of the seeds are virtually identical. when examining similar seeds the analyst must contend with subtleties of shape, symmetry, and texture.
The seed unit for the dock family is the achene. The achene is lenticular
and three
sided and may or may not have a persistent calyx. Just as with the
flowers, there are two types of seed units. Cyclic flowers produce achenes
which aire triangular in cross section and generally have acute angles.
The acyclic flowers produce achenes with a lenticular to slightly trigonous
shape with rounded angles. The achene coats of both types range from smooth
and shiny to faintly pitted or roughened. Colors range from golden brown
to black. The actual testa varies from dull and papery to membranous. The
hilum. is inconspicuous, but the achene attachment scar may be prominent.
Internally, the embryo is peripheral and found either along the face of one of the sides or down one of the angles. The endosperm is abundant and mealy to fleshy, often with an oily appearance.