564 



POLYGONACE^. 



generally on one side (fig. 800), sometimes in the axis of the albumen ; 

 radicle superior (fig. 800). — Herbaceous, rarely shrubby plants, with 

 alternate, stipulate, or exstipulate leaves, and often unisexual fiowers. 

 They are found in almost all parts of the world, more especially in the 

 temperate regions of the northern hemisphere. They grow in fields, 

 waste-grounds, ditches, mountains, etc. The order has been divided 



Kg. r98. 



Fig. 799. 



Fig. 800. 



into two tribes : — 1. Polygonese, with loose flowers, embryo usually 

 abaxial (fig. 617, p. 341), ochreate stipules (fig. 147, p. 82). 2. 

 Eriogonese, with involucrate flowers, embryo axial, leaves generally 

 exstipulate. Authors enumerate 33 genera, including 500 species. 

 Examples — Polygonum, Rumex, Eheum, Eriogonum. 



The plants of this order have astringent and acid properties ; some 

 of them are purgative, and a few are acrid. Their astringency depends 

 on the presence of tannin, and their acidity chiefly on oxalic acid. 

 The root (or rhizome) of Polygonum Bistorta, Bistort, so called on 

 account of its double twist, contains much tannin, some gallic acid, 

 and starch, and is a powerful astringent. The leaves of P. Hydropiper, 

 Water-pepper, are acrid and vesicant. P. tinctorium yields a blue dye. 

 The fruit of P. aviculare is emetic and purgative. P. cymosmn, on the 

 Himalaya, is used as spinach, under the name of PuUop-bi. P. 

 Sieboldi, in Japan, supplies a green crop for cattle. The fruit of Fago- 

 pyrum esculentum, F. tataricum, and other species of Buckwheat, are 

 used as food. The plants are cultivated in some northern countries. 

 The leaves of Rumex acetosa, Common Sorrel, and of R. Acetosella, 

 Sheep's Sorrel, are acid and astringent. The roots of Rumex aquations, 

 Water Dock, R. Hyirolapathum, Great Water Dock, and of other 

 species, are used as astringents and alteratives, while those of R. 



Figs. 798-800. Organs of ftuctifi cation of Fagopyrum esculentum (Polygonum Fagopy- 

 nim), to illustrate tlie natural order PolygonaceEE.^ Fig. 798. Vertical section of the 

 flower, cc, Perianth, ee, Outer stamens, which are introrse. ,ei, Inner stamens, which 

 are extrorse. ■ a, Glandular appendages, o, Ovary with its erect ovule, g, s, Styles and 

 stigmas. Fig. 799. Diagram of the flower, showing five divisions of the imbricate 



perianth, stamens opposite the divisions, with glands and triangular unilocular ovary. 

 Fig. 800. Seed cut vertically, showing the embryo with Its superior radicle curved at one 

 side of mealy albumen. 



