62 ELEMENTS OP BOTANY. 



I. RUMEX. 



Annual or perennial herbs, stems grooved, usually branch- 

 ing above ; leaves alternate, hastate-lobed or entire ; flowers 

 perfect or polygamo-dioecious, in whorls on jointed pedicels ; 

 calyx of 6 sepals, the outer 3 being usually colored and petal- 

 like, while the inner 3 form a persistent, winged, 3-valved 

 covering for the fruit ; stamens 6 ; styles 3, stigmas many 

 cleft. 



1. R. AcETOSELLA L. Sheep Sorrel. Erect, annual or 

 perennial herbs with creeping rootstocks ; stem simple or branched, 

 glabrous ; leaves petioled, narrowly hastate, usually widest above 

 the middle, the apex acute or obtuse, upper stem leaves often nearly 

 linear, and not lobed ; flowers dioecious, small, in terminal, naked, 

 panicled, interrupted racemes ; calyx greeidsh ; the pistillate panicles 

 becoming reddish ; fruit less than ^L i"- long, granular, longer than 

 the calyx. April-August. A common introduced weed, in dry fields 

 and on sour soils. Foliage very acid. 



2. R. VERTiciLLATUs L. SwAMP DocK. Perennial; stem 

 stout, smooth, erect or ascending, 3-5 ft. tall ; lower leaves oblong, 

 obtuse at the apex and usually cordate at the base, long-petioled, 

 often 12-18 in. long, upper leaves narrower and often acute at both 

 ends ; flowers perfect or polygamous, in dense whorls, pedicels slen- 

 der, ^-f in. long, tapering downward, reflexed at maturity ; calyx 

 green, the valves broadly deltoid, abruptly pointed, reticulated, a 

 distinct, long and narrow tubercle on the back of each. May-June. 

 Swamps and wet ground. 



3. R. OBTusiFOLius L. BiTTER DocK. Perennial; stem erect, 

 stout, branched and somewhat roughened above, 2-4 ft. tall ; low-er 

 leaves ovate-oblong, obtuse at the apex, cordate at the base, long- 

 petioled ; the upper leaves lanceolate or lanceolate-oblong, acute at 

 each end, short-petioled, often wavy on the margin ; flowers perfect 

 or polygamous, in open, panicled racemes, the lower whorls scattered, 

 the upper more crow^ded ; pedicels slender, a little longer than the 

 fruit ; wings hastate, ^ in. long, with a few spiny teeth on the mar- 

 gins, and at least one of them prominently tubercled on the back. 

 May-August. A common naturalized weed on rich soil. 



II. POLYGONUM. 



Annual or perennial, terrestrial or aquatic herbs, with tumid 

 joints and simple, alternate, entire leaves ; the sheathing stip- 



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