IS KEY TO THE SPECIES 



XVII. POLYGONACEiE (Buckwheat Family) 



Herbs with alternate entire leaves, stipules in the form of 

 sheaths above the swollen joints of the stem or wanting, 3-6- 

 cleft calyx, no petals, 4-8 stamens, and a 1-celled ovary usually 

 becoming a 3-angled nut-like fruit (achene). 



» Ochrea none ; flowers subtended by involucres. 



1. Eriogonum. Stamens 9 ; calyx 6-cleft or parted. 



* * Ochrea present ; flowers not involucrate. 



2. Rumex. Stamens 6 ; calyx 6-partRd. 



3. Polygonum. Stamens 8 ; calyx 5-parted. 



1. ERIOGONUM 



Annual or perennial herbs or with shrubby base, with entire leaves, small 

 flowers in umbellate or capitate clusters which are subtended by a 5-8-toothed 

 or cleft involucre ; style 3-parted ; stigma capitate ; achene 3-angled. 



* Flowers yellow ; involucre turbinate. 

 -r- Achene angled (not wingedj. 



1. Eriogonum umbellatum Torr. (Sulphur Flower). Perennial, with 

 scapose stems ; leaves smooth and green above, white-tomentose below, oblanceo- 

 late or Rpatulate ; bracts large and leaf-like ; umbel of 2-10 rays; flowers glabrous, 

 sulphur yellow. Abundant on hillsides and mountain foothills. 



2. Eriogonum subalpinum Greene (Sub-alpine Eriogonum). Very simi- 

 lar to the above, but often larger, 3-5 dm. high ; the leaves more tomentuse above, 

 and the flowers a light yellow or creamy-white. In similar situations. 



3. Eriogonum flavum Nutt. (Yellow Eriogonum). Perennial, white-tomen- 

 tose ; scape naked, about 2 dm. high ; leaves oblanceolate ; bracts rather large ; 

 flowers bright yellow, very silky -pubescent ; filaments villous at base ; acheue vil- 

 lous near the top. Canons and foothills. 



-K -I- Achene winged. 



4. Eriogonum alatum Torr. (Winged Eriogonum). An erect perennial, 



5-10 dm. high, branched above, with a stiff pubescence ; leaves nearly linear, the 

 midrib conspicuous below ; inflorescence an open panicle, the' solitary involucres 

 with five erect teeth ; flowers small, yellow ; achene 3-winged. 



* * Flowers white, shading to pink or purple, 

 -f- Annual. 



5. Eriogonum annuum Nutt. (Annual Eriogonum). White-tomentose; 

 stems mostly simple, leafy below, 3-6 dm. high ; leaves oblong or oblanceolate ; 

 bracts small ; inflorescence a di- or trichotomous cyme ; calyx white, the outer 

 fiegments broader than the inner, glabrous, as is also the achene. Common on the 

 dry plains. 



6. Eriogonum cerniium Nutt. (Nodding Eriogonum). Nearly glabrous ; 

 leaves radical, oval to orbicular ; the slender naked stem branching diffusely and 

 terminating in trichotomous cymes ; flowers white or rose-colored, on deflexed 



