182 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



KEY TO THE GENERA. 



Flowers subtended by an involucre; stamens 9; sheaths 



wanting 1. Eriogonum (p. 182). 



Flowers not involucrate; stamens 4 to 8; sheaths present. 

 Stigmas tufted. 



Sepals 4; stigmas 2; achenes lenticular, winged; 



leaves orbicular-reniform 2. Oxyria (p. 190). 



Sepals 6; stigmas 3; achenes 3-angled, not winged; 

 leaves not orbicular-reniform, elongated or 



hastate 3. Rumex (p. 191). 



Stigmas capitate. 



Leaf blades jointed at the base; filaments, at least 

 the inner, dilated. 

 Herbs; flowers fascicled; sepals not winged... 5. Polygonum (p. 193). 

 Shrub; flowers solitary; inner sepals winged.. 4. Gonopyrum (p. 193). 

 Leaf blades not jointed at the base; sheaths not 

 2-lobed; filaments slender. 



Sheaths cylindric, truncate 6. Persicaria (p. 195). 



Sheaths oblique, more or less open on the side 

 facing the leaf. 

 Sepals, at least the outer ones, keeled or 



winged ; stems twining 8. Bilderdykia (p. 197) . 



Sepals neither keeled nor winged ; stems 

 erect. 

 Perennials with fleshy rootstocks, 

 mostly basal leaves, and 



simple stems 7. Bistorta (p. 197). 



Annual with fibrous roots, cauline 



leaves, and branched stems.. 9. Fagopyrum (p. 197). 



1. ERIOGONUM Michx. 



Low annuals or perennials, herbaceous, or somewhat woody at the base; leaves 

 entire, basal or scattered along the stem; inflorescence various; flowers involucrate; 

 involucre 4 to 8-toothed or lobed, mostly many-flowered; calyx with 6 divisions 

 (valves), colored, corolla-like; stamens 9; achenes triangular, sometimes winged. 



The genus is one of the largest in our State. Representatives are found almost 

 everywhere, especially at lower elevations. Strangely enough, although among our 

 commonest plants, no common name seems to have been given them, probably because 

 the plants are usually small and inconspicuous. Some species, however, are rather 

 handsome. 



KEY TO THE SPECIES. 



Fruit winged, at least above; large coarse perennials. 



Wings extending the entire length of the fruit; perianth 

 glabrous. 



Involucres strigose 1. E. alatum. 



Involucres glabrous 2. E. triste. 



Fruit winged only above the middle; perianth pubescent. 

 Leaves loosely and coarsely tomentose beneath, com- 

 monly acutish; involucres 3 to 5 mm. long 3. E. hieracifolium. 



Leaves very densely and finely tomentose beneath, 



rounded -obtuse; involucres 2 to 3 mm. long 4. E. pannosum. 



