480 



POLYGONACEJE. 



pains, and it possesses also emetic and purgative qualities. The plant 

 is said to yield much potash. Petiveria alliacea is the Guinea-hen- 

 weed, so called on account of these animals being fond of it. 



990. Order 148. Polygonacete, the Buckwheat Family. (Apet. 

 Hypog. and Perigyn.) Perianth inferior (fig. 688 c c), divided, often 

 coloured; aestivation imbricate (fig. 689). Stamens definite, inserted 

 into the bottom of the perianth (fig. 688 e e, e z); anthers with longi- 

 tudinal dehiscence. Ovary free (fig. 688 o), usually formed by 3 car- 

 pels, unilocular; ovule solitary, orthotropal (fig. 418); styles and 

 stigmas equal to the carpels in number (fig. 688 s). Fruit a nut, usually 

 triangular, naked or covered by the persistent perianth (fig. 271). 

 Seed erect; albumen farinaceous; embryo antitropal, generally on one 

 side (fig. 690) sometimes in the axis of the albumen; radicle superior 



(fig. 690). Herbaceous, rarely shrubby plants, with alternate, stipu- 

 late, or exstipulate leaves, and often unisexual flowers. They are 

 found in almost all parts of the world, more especially in the tem- 

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

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

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

 abaxial (fig. 521), ochreate stipules (fig. 132). 2. Eriogoneas, with 

 involucrate flowers, embryo axial, leaves generally exstipulate. 

 Lindley enumerates 29 genera, including 490 species. Examples 

 Polygonum, Eumex, Eheum, Eriogonum. 



991. 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 of Polygonum Bistorta, Bistort, so called on account of 



Figs. 688-690. Organs of fructification of Fagopyrnm esculentum (Polygonum Fagopyrum), 

 to illustrate the natural order Polygonaceae. 



Fig. 688. Vertical section of the flower, c c. Perianth, e e. Outer stamens, which are in- 

 trorse. e i, Inner stamens, which are extrorse. a, Glandular appendages, o, Ovary with its 

 erect ovule, g. s, Styles and stigmas. 



Fig. 689. Diagram of the flower, showing five divisions of the imbricate perianth, stamens 

 opposite the divisions, with glands and triangular unilocular ovary. 



Fig. 690. Seed cut vertically, showing the embryo with its superior radicle curved at one 

 side of mealy albumen. 



