This biennial (rarely perennial) is perhaps the most widespread 

 and common native species of the rockcresses and has been selected to 

 illustrate the genus. It is found in the 11 far-western States, as well 

 as in many of the eastern States and in southern Canada, and grows 

 in a wide variety of soils, and in moist to wet sites. It is more com- 

 mon in open grass and weed types but occurs also in shrub, wood- 

 land, and timber types, although seldom in dense shade. Generally, 

 it occurs scatteringly but is abundant in some localities, especially on 

 areas where the perennial grasses have largely been destroyed by 

 overgrazing. Its forage value varies considerably, doubtless because 

 of different conditions of abundance, habitat, size, and presence of 

 more valuable species. In the main, where better plants are avail- 

 able, it is usually of low value but occasionally is reported as being 

 grazed rather readily by sheep and even cattle, especially on over- 

 grazed ranges. 



Mountain rockcress develops a strong taproot. One to several un- 

 branched stems, 10 to 32 inches high, grow up from a basal rosette 

 of relatively narrow leaves which are narrowed toward the base 

 rather than toward the tip. The stem leaves taper gradually to a 

 pointed tip, and are somewhat larger than the basal leaves. The 

 clusters of white or pinkish flowers are usually small and the seed 

 pods are erect in a rather compact cluster. Sometimes the plants are 

 slightly hairy toward the base, the hairs being horizontal and at- 

 tached at the middle. 



ROCKCRESSES 



(A'rabis spp.) 



Rockcresses include annual, biennial, or perenial weeds and are of 

 world-wide distribution. There are more than 80 species in the west- 

 ern United States. This genus belongs to the mustard family 

 (Brassicaceae). Many authors use Cruciferae as the name of this 

 plant family, a name derived from the Latin crux, cross, and fero, 

 bear, referring to the crosslike arrangement of the petals a very 

 marked characteristic of this family. These plants, even if not in 

 flower, can often be recognized by the pungent or acrid taste of leaf 

 or stem. 



In the rockcress genus (Arabis, from Arabia) flowers are white, 

 pink, or purple, rarely yellowish, and have the distinctive mustard- 

 family characters of four separate sepals, four separate petals, and 

 six stamens (pollen-producing organs), two of which are shorter 

 than the others. The pistils (seed-producing organs of the flowers) 

 mature into long, narrow, flattened pods, with numerous seeds 

 usually in two rows. Leaves are entire or toothed; the stem leaves 

 are alternate, almost always stalkless, and frequently with clasping 

 bases. Usually there is a fairly dense cluster (rosette) of stalked 

 leaves at the base of the stems. 



In the aggregate the rockcresses are usually considered of low 

 forage value but under some conditions, especially on overgrazed or 

 depleted ranges, may be readily taken if succulent. 



