158 VniversiUj of California Puhlications in Botany [Vol.9 



20. POLYGON ACE AE (Buckwheat Family) 



Flowers in involucres; stipules wanting; stamens 9 1. Eriogonum 



Flowers not in involucres; stipules present, sheathing the nodes; stamens 4-8. 



The outer sepals smaller and reflexed, the inner accrescent about the fruit. 



Sepals 4; stigmas 2; achene compressed, thin, broadly 2-winged; leaves 



reniform 2. Oxyria 



Sepals 6; stigmas 3; achene triangular in cross-section, not winged; leaves 



not reniform, usually lanceolate or oblong 3. Rumex 



Sepals uniform in size and usually not changed in fruit, 5 in number (rarely 

 4 or 6) 4. Polygonum 



1. ERIOGONUM 



Involucres solitary; calyx not stipe-like at base. 



Involucres borne on the capillary branchlets of the dichotomous panicle; 

 annual with the linear vegetative leaves radical, the few cauline reduced 



to bracts 1. E. sperguUnum 



Involucres borne on the stout or wiry branches of the inflorescence; per- 

 ennials with short leafy stems. 

 Leaves oblanceolate to linear (%-1..5 inches long), never fasicled, acute, 

 more or less revolute, white tomentose beneath and glabrate above; 



involucres cymosely umbellate 2. E. microthecum 



Leaves oblanceolate, obtusish (^/4-l inch long), some of the smaller 

 fascicled in the axils of the larger, flat, white-woolly on both sides; 



involucres spicate along the erect branches of the panicle 



3. E. Wrightii 



Involucres in heads or umbels (in reduced high mountain forms sometimes 

 solitary, but the calyx then stipe-like at base). 

 Involucres 5-6 nerved, in dense capitate clusters, never umbellate; calyces 

 not stipe-like at base. 

 Leaves densely white tomentose below; glabrate above and green; in- 

 volucres glabrous or nearly so; stems taller (5 inches-1.5 feet high), 



glabrous above 4. E. nudum 



Leaves permanently white-woolly on both sides; involucres woolly; stems 

 low (4-5 inches or less) with 1 or rarely 2 heads. 

 Perianth segments dissimilar, the outer broadly oval and cordate at base, 



the inner narrow and spatulate 5. E. ovalifolium 



Perianth segments nearly alike, obovate, cuneate 6. E. Kingii 



Involucres nerveless; calyces stipe-like at base. 



Umbels conspicuously bracteate, the bracts large and foliaceous . 

 Involucres deeply lobed, the lobes becoming reflexed. 

 Umbels simple, the mys undivided. 

 Plants jjubescent (stems and leaves). 



Leaves very obtuse or roundish, densely silvery -woolly on both sides; 

 peduncles decumbent; flowers white or pinkish ....7. E. Lobbii 

 Leaves ovate, glabrate above ; peduncles erect ; flowers yellow 



8. E. umbellatum 



Plants glabrous (stems and leaves) 9. E. Torreyanum 



Umbels compound, bracteate at all the nodes 10. E. stellatum 



Involucres with short erect teeth; umbel usually compound (3-10 rays); 



leaves oval or roundish 11. E. ursinum 



Umbels with a few linear inconspicuous bracts at the base of the rays; 

 involucre with short erect teeth. 

 Eays short, slender, sometimes so reduced as to make the umbel appear 

 capitate; leaves permanently white-tomentose; plants forming thick 



dense mats 12. E. incanum 



Eays longer and more numerous; leaves often glabrate above; plants 

 looser, the branches of the caudex spreading 13. E. marifoUum 



