POLYGONACE^ 305 



1. RHfiUM. RHUBARB. 



Very large-leaved perennials, sending up stout hollow flower-stalks in 

 early summer which bear smaller leaves with sheathing bases : sepals 6, all 

 alike, withering rather than falling, and persisting beneath the 3-winged 

 akene: stamens 9: styles 3. Old World. 



R. Rhap6nticum, Linn. Hhubarb. Pie-plant. Figs. 78, 79. Leaves 

 1 ft. or more across, the thick petioles eaten: fls. white, in elevated panicles. 



2. BtTMEX. DOCK. SORREL. 



Perennial often deep-rooted plants with herbage bitter or sour: sepals 6, 

 the 3 outer large and spreading, the 3 inner (known as "valves") enlarging 

 after flowering and one or more of them often bearing a grain-like tubercle 

 on the back: stamens 6, styles 3: flowers in pan- 

 icles or interrupted spikes. 



a. Docks: herbage bitter: valves often grain- 

 bearing : flowers mostly perfect : leaves 

 not arrow-shaped. 



R. obtusifolius, Linn. Sitter dock. Lower leaves 

 oblong-cordate and obtuse, not wavy: one valve 

 usually grain-bearing. Weed from Europe. 



R. crispus, Linn. Curly dock. Leaves lanceo- 

 late, wavy or curled : all valves usually grain-bear - 

 453. Rumex Acetosella. ing. Weed from Europe. 



aa. Sorrels: herbage sour: valves not grain-bearing: flowers dioecious: 



leaves arrow-shaped. 



R. Acetos611a, Linn. Common or sheep sorrel. Fig. 453. Low (1 ft. 

 or less) : leaves mostly arrow-shaped at base: flow- 

 ers brownish, small, in a terminal panicle. Common 

 in sterile fields. Europe. 



3. FAGOPt"RUM, BUCKWHEAT. 



Fast-growing annuals, with somewhat triangu- 

 lar leaves, and fragrant flowers in flattish, panicle- 

 like clusters: calyx of 5 parts: stamens 8: fruit a 

 triangular akene. Old World. 



F. esculentum, Moench. Common buckwheat. 

 Fig. 454. Leaves triangular-arrow-shaped, long-peti- 

 oled: flowers white, in a compound cluster: akene 

 with regular angles. Flour is made from the grain. 



F. Tataricum, Gaertn. India wheat. Slen- 454. 



derer, the leaves smaller and more arrow-shaped Fas^y* esculentum. 

 and short-petioled : flowers greenish or yellowish, in simple racemes : akene 

 notched on the angles. Somewhat cultivated. 



4. POL^GONUM. KNOTWEED. SMARTWEED. 



Low weedy plants, or some exotic ones tall and cultivated, blooming in 

 summer and fall, the small pinkish or greenish flowers mostly in racemes or 



