POLYGOHUM. 203 



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

 (6 ft.) and stout, has the ochreae 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 swollen joints. 

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

 which the genus 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 Sorrel worts 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 Raponticum), 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 (Rumex), 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 Acetosella) 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. Ochreae. Raceme. Spike. 



* In their modes of fertilization there is much diversity among the plants of this 

 order. The various species of Rumex are destitute of honey, and wind-fertilized. 

 Of the Polyganums, P. aviculdre, the Bird Knotweed, is probably self-fertilized. P. 

 Persicaria is proterandrous, its stigmas ripening after their anthers have shed their 

 pollen, while the Buckwheat is dimorphous, some of it with long stamens and short 

 styles, others with long styles and short stamens. 



