Buckwheat Family 111 



pedicels. Calyx of 4-9 sepals, usually petaloid, persist- 

 ent. Stamens as many as the sepals, perigynous. Styles 

 2-4, distinct or somewhat united, opposite the angles of 

 the lenticular or triquetrous achene. Seed erect; em- 

 bryo straight within the mealy endosperm or curved 

 around it. 



Leaves without stipules. 

 Involucre bract-like. 



Flowers solitary, surrounded by a 2-lobed bract, becoming elongated 1 



in fruit. 1. PTEROSTEGIA. 



Flowers capitate, each surrounded by a bract. 2. NEMACAULIS. 

 Involucre wanting; calyx involucre-like. 3. LASTARBIAB. 



Involucre tubular with 3-6 cuspidate or awned often hooked teeth. 



4. CHORIZANTHE. 



Involucre turbinate with 18-20 acicular awns. 5. ACANTHOSCYPHUS. 

 Involucre campanulate or turbinate, deeply 3-5-cleft, the lobes ending in 



straight awns or awnless. 6. OXYTHECA. 



Involucre oblong, campanulate or turbinate, 4-8-toothed or lobed, awnless,, 



usually many-flowered. 7. ERIOGONUM. 



Leaves with sheathing stipules. 



Sepals 6, the outer 3 smaller; stigmas 3, tufted. 8. RUMEX. 

 Sepals 4-6, equal; stigmas 2-3, capitate. 9. POLYGONUM. 



1. PTEROSTEGIA F. & M. 



Very slender annuals, diffusely dichotomous from the 

 base, with opposite leaves and foliaceous 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, insert- 

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

 glabrous ; cotyledons accumbent. 



1. 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 reddis 

 when growing in exposed places. 



