POLYGONUM. 203 



P. orientale, Lady's Thumb, a foreigner, about houses, tall 

 (G ft.) and stout, has the oclirea^ with a spreading border, the 

 flower clusters large, rose-colored, stamens 7, etc. 



Classification.— The order Polygon ace^ — the Sorrel - 

 worts — may be characterized as follows : 



Herbs with alternate leaves and swelled joints. 

 Stipules in the form of ochreae sheathing the stem (a feature by 

 which the order may be recognized at sight). 

 Flowers apetalous, with a persistent calyx. 

 Ovary 1-celled, with 2 or 3 styles or stigmas. 

 Achenium with 1 erect albuminous seed. 



The Sorrelworts number 33 genera and 690 species abounding 

 in all countries. Among these are — 



The Buckwheat Plant {Fagopyrum) indigenous in Northern Asia, 

 now extensively cultivated as an article of food in general use, and by 

 bee-keepers as a valuable honey plant. The small black kernel with 

 white albumen, whence the ' flour ' is obtained, has, as every one knows, 

 the form of a Beechnut (German, Buck). Hence its name, both English 

 and classical, is equivalent to Beech- wheat. 



Rhubarb {Rheum Rapontinim), also from Asia, is the well-known 

 Pie Plant. The pulpy tissue of the petioles is made acid by the oxa- 

 late of lime. Several species of Rheum yield the medicinal rhubarb- 

 root of the shops. 



Dock (Micme.v), both the Broad-leaved and the Narrow-leaved, 

 everywhere abounds as a " pernicious weed ; " yet the roots of some 

 species afford a valuable medicine. 



Sheep Sorrel {Rumex Acetosclld) has a pleasant acid foliage, and 

 abounds in old fields and pastures where there is a lack of alkali in 

 the soil, reddening with its minute flowers many a sterile knoll and 

 hillside.* 



Scientific Terms.— Apetalous. Ciliate. Ochrefe. Raceme. Spike. 



* In their modes of fertilization there fs much diverpitv amonj; the plants of this 

 order. The various species of Rnniex are dostitulc of honey, and wind-feirilizcd. 

 Of the Polyganums, P. ariculdre^ the Bird Knofweed, is jirohahly self-fertilized. P. 

 Persicana is proterandrons, its stigmas ripening after their anthers have shed their 

 pollen, while the Buckwheat is <Iin)orp?iom, some of it with long stamens and short 

 styles, others with long styles and short stamens. 



