330 SYSTEMATIC BOTANY. 



weed, is very acrid, even vesicant when fresh. P. Bistorta was formerly 

 in use as an astringent ; and Coccoloba uvifera, the sea-side Grape of the 

 West Indies, furnishes a very astringent extract. The Rhubarb of medi- 

 cine consists of the roots of Rheum officinale, and perhaps also of palma- 

 tum, undulatum, rhaponticum, Einodi^ Webbianum, and other species ; the 

 roots of Rumex alpinus were formerly used as a purgative under the name 

 of Monk's Rhubarb. Fagopyrum escukntum, common Buck-wheat, F. 

 tataricum, and other species are largely cultivated for food in the northern 

 parts of Asia and of Eastern Europe. The common Docks are species of 

 Rumex. 



NYCTAGINACE^E (THE MARVEL-OF-PERU ORDER) consists of 

 herbs, shrubs, or trees, mostly with opposite and entire leaves ; stems 

 tumid at the joints ; flowers surrounded by an involucre, with a delicate, 

 tubular or funnel-shaped petaloid perianth ; upper part deciduous, lower 

 part persistent, constricted above the 1-celled, 1-seeded ovary, and indu- 

 rated to form the pericarp (diclesium) ; stamens 1 or several, slender, 

 hypogynous ; the embryo coiled round the outside of the mealy perisperm, 

 with broad foliaceous cotyledons and an inferior radicle. Illustrative 

 Genera : Boerhaavia, L. j Mirabilis, L. ; Pisonia, Plum. 



Affinities, &c. The nearest relatives of these plants are probably the 

 Polygonaceae, especially the tribe of Eriogone-ce ; but the inferior radicle 

 and the peculiar fruit enclosed in the indurated base of the perianth are 

 evident distinctions. The stems of these plants, especially of the Pisonice, 

 have a curious arrangement of their fibro-vascular bundles. The nature 

 of the involucre serves to divide the Order into tribes. 



Distribution. Natives of warm climates, chiefly in the S. hemisphere. 



Qualities and Uses. The roots of the Nyctaginaceae are generally pur- 

 gative ; and Mirabilis Jalapa was formerly supposed to be the source of 

 medicinal Jalap. Mirabilis dichotoma, the Marvel of Peru of our gardens, 

 is remarkable for opening its flowers in the afternoon, whence it is termed 

 the Four-o'clock Plant ; both this and M. lonyiflora, another cultivated 

 species, are violent purgatives. Bougainvillea is remarkable for its brightly- 

 coloured bracts. 



AMARANTACEJE (AMARANTHS) are weedy herbs, with opposite or 

 alternate exstipulate leaves, and spiked or capitate, bracteated inflores- 

 cence ; the flowers mostly with an imbricated perianth of dry and scarious 

 persistent bracts, often coloured, 3-5 in number ; occasionally unisexual ; 

 stamens 5-merous, hypogynous ; anthers sometimes 1-celled ; the one- 

 celled ovary usually 1-ovuled, in one tribe (Celosiese) many-ovuled ; style 

 1 or ; stigma simple or compound ; fruit a utricle, a caryopsis, or a 

 berry ; seed pendulous, with the embryo curved round the circumference 

 of farinaceous perisperm ; the radicle near the hilum. Illustrative Genera : 

 Celosia, L. ; Amarantus, L. ; Achyranthes, L. ; Gomphrena, L. 



Affinities, &c. No absolute character can be given to separate this Order 

 from the Chenopodiaceae ; but the habit, especially the crowded bracteated 

 inflorescence and the membranous perianth, renders them very different 

 in appearance. Their more distant relations are the same as those of that 

 Order. The division into tribes depends upon the 1- or 2-celled anthers 

 and the number of ovules in the ovary. 



