102 



POLYGONACEAE. 



Leaves without stipules. 



Involucre of distinct bracts or wanting. 

 Bracts present. 



Flowers solitary, surrounded by a 

 2-lobed bract, becoming en- 

 larged in fruit. 

 Flowers capitate, each surrounded 

 by a bract. 

 Bracts wanting: calyx involucre-like. 

 Involucre turbinate to campanulate, 

 toothed or lobed. 

 Teeth of the involucre cuspidate or 

 awned. 

 Involucre tubular, 5-6-toothed, 

 usually with hooked awns, and 

 usually 1-flowered. 

 Involucre turbinate or campanu- 

 late, deeply lobed: awns 

 straight: flowers 2-many. 

 Involucre turbinate, with 18- 



20 acicular awns. 

 Involucre deeply 3-5 cleft, the 

 lobes ending in straight awns 

 or awnless. 

 Teeth of the involucre 3-8, not awned. 

 Leaves with sheathing stipules. 



Sepals 6, the outer 3 smaller; stigmas 



tufted. 

 Sepals 4-5, similar; stigmas capitate. 



1. Pterostegia. 



2. Nemacaulis. 



3. Lastarriaea. 



4. Chorizanthe. 



5. ACANTHOCYPHUS. 



6. Oxytheca. 



7. Eriogonum. 



8. Rumex. 



9. Polygonum. 



L PTEROSTEGIA F. & M. 



Very slender annuals, dIfTusely dichotomous from the 

 base, with opposite leaves and follaceous bracts. Invo- 

 lucres axillary, sessile, solitary, consisting of a single 

 2-lobed bract, shorter than the solitary sessile flower, 

 enlarged in fruit, scarious and reticulated, loosely en- 

 closing the achene, gibbously 2-saccate on the back. 

 Calyx 6-parted or rarely 5-parted. Stamens 3-6, in- 

 serted at the base of the calyx-lobes. Achene triangular, 

 glabrous; cotyledons accumbent. 



L P. drymarioides F. & M. Stems several from the base, 10- 

 30 cm. long or more; lower leaves petioled, 4-12 mm. long, fan- 

 shaped, 2-lobed, the lobes crenately toothed or slightly lobed; 

 upper leaves obovate-spatulate, entire or more or less toothed; 

 bracts similar, 2 mm. long; involucres 2-3 mm. long in fruit, the 

 margins of the lobes toothed or laciniate; flowers about 1.5 mm. 

 long, sessile; calyx-lobes lanceolate. 



Common and general below 4000 feet. The whole plant often 

 reddish when growing in exposed places. 



