48 
PLANTS OF YELLOWSTONE NATIONAL PARK 
ground stem. The leaves are entire and vary from oblong to nearly 
linear in shape. 
BUCKWHEAT FAMILY (POLYGONACEAE) 
This is a large family containing trees, shrubs, and herbs, but 
only herbs are represented in the park. The flowers, for the most 
part, are rather small and inconspicuous, and the family contains 
relatively few ornamental plants. It contains some pernicious weeds 
and the cultivated buckwheat is a valuable food plant. 
1. Flowers subtended by an involucre. Sheaths lacking on stem. 2. 
1. Flowers not subtended by an involucre. Sheaths present on stem. 8. 
2. Bracts several, leaflike. 3. 
2. Bracts in 3’s, not leaflike. 7. 
3. Flower stalk with a whorl of leaves near the middle. Wyeth eriogonum 
(Eriogonum heracleoides) ____(p. 49) 
3. Leaves all basal. 4. 
4. Flowers smooth. 5. 
4. Flowers hairy. 6. 
5. Flowers bright yellow. Sulphur eriogonum (Eriogonum umbellatum) _(p. 49) 
5. Flowers pale yellow. Eriogonum subalpinum ___(p. 49) 
6. Leaves thick. Eriogonum flavum _ ____(p. 50) 
6. Leaves thin. Piper eriogonum {Eriogonum piperi )___(p. 50) 
7. Flowers white. Cushion eriogonum {Eriogonum ovalifolium) __(p. 50) 
7. Flowers bright yellow. Eriogonum andinum ___(p. 50) 
7. Flowers pale yellow. Eriogonum ochroleucum ___(p. 50) 
8. Perianth parts 4. Mountain-sorrel (Oxyria digyna) _ ___ (p. 50) 
8. Perianth parts 5. 9. 
8. Perianth parts 6. Dock and Sorrel ( Rumex )____ (p. 50) 
9. Plants climbing. Cornbind (Polygonum convolvulus )__ (p. 52) 
9. Plants not climbing. 10. 
10. Plants prostrate. Knotweed (Polygonum aviculare) ___(p. 52) 
10. Plants erect. 11. 
11. Flowers axillary. 12. 
11. Flowers in spikes or spikelike clusters. 13. 
12. Stamens 5 or 6. Polygonum erectum _____(p. 52) 
12. Stamens 8. Polygonum douglasii _(p. 52) 
13. Aquatic plants. Water ladysthumb (Polygonum amphibium) _(p. 52) 
13. Not strictly aquatic though some may grow in very wet places. 14. 
14. Some of the flowers replaced by bulblets. Polygonum viviparum „_(p. 52) 
14. None of the flowers replaced by bulblets. 15. 
15. Flowers bright rose color. Polygonum hartwrightii _(p. 52) 
15. Flowers white or whitish. 16. 
16. Stamens longer than the corolla. American bistort (Polygonum bistor- 
toides )_(p. 52) 
16. Stamens shorter than the corolla. Polygonum polygaloides ___(p. 52) 
Eriogonum .—The plants all have flowers with a 6-parted perianth, 
no petals, 9 stamens, and 1 pistil with 3 styles. They are found 
mostly in dry places. 
