66 
PLANTS OF YELLOWSTONE NATIONAL PARK 
3. Leaves narrowly lanceolate or oblanceolate. Pods 
about iy 2 inches long_ Arabis lyallii. 
4. Plants more than 2 feet high.___ Arabis perelegans. 
4. Plants less than a foot high__ Arabis oxylobula. 
5. Upper leaves smooth. 6. 
5. Upper leaves hairy. 8. 
6. Stems hairy at the base_ Arabis glabra. 
6. Stems smooth at the base or nearly so. 7. 
7. Leaves entire-,----- Arabis drummandii. 
7. Leaves more or less toothed_ Arabis fruticosa. 
8. Stems not woody at the base. 9. 
8. Stems somewhat woody at the base. 12. 
9. Pods widely spreading. 10. 
9. Pods erect or nearly so. 11. 
10. Leaves all linear. Plant white-hairy_____ Arabis canescens. 
10. Lower leaves oblong to lance-shaped. Plant not 
white-hairy-__--- Arabis exilis. 
11. Pods less than an inch long_ Arabis nuttallii. 
11. Pods more than an inch long____,_ Arabis hirsuta. 
12. Stems solitary--- Arabis lignipes. 
12. Stems several___ Arabis lignifera. 
In addition to the above species Arabis coluynbiana , A. furcata , 
and A. retrofracta have been reported as occurring in the park. 
Thelypodium sagittatum is an erect but rather weak herb with 
lilac-colored flowers. The leaves are sessile and clasping with ear¬ 
like lobes at the base, the lower ones lance-shaped and the upper 
ones linear. 
Thelypodium integrifolium has pale rose-colored flowers and the 
leaves are not clasping. 
Thelypodium Ulaeinum var. subumbellatum has also been found 
in the park. 
Mountain bittercress (Cardamine cordifolia) .—The plant is smooth 
throughout, 1 to 3 feet high, and leafy to the top. The leaves are 
heart-shaped and the flowers are white. 
Cardamine uni jug a is only 4 to 8 inches high, and some of the 
leaves are somewhat pinnate with 1 or 2 pairs of oblong leaflets; 
and Brewer bittercress ( Cardamine breweri) is 8 to 16 inches high, 
and its leaves are distinctly pinnate with 5 to 7 leaflets. 
Smelowskia americana is a low, perennial, alpine herb with densely 
clustered stems, the lower parts of which are densely covered by the 
bases of the dead leaves. The leaves are 1 to 2 inches long and 
pinnately divided into linear lobes. The flowers are white or pinkish. 
Sophia incisa grows 8 to 16 inches high and is often densely 
short-hairy. The leaves are pinnately lobed or evenly dissected 
and the small yellow flowers are produced in racemes which 
become much elongated as the fruits mature. 
Sophia gracilis has also been reported in the park. 
