Uerbaceous plants. 289 



Rock-Cress, Arabis olpiiia. — This is one of the prettiest 

 of all rock-plants early in spring. It forms dense, spreading 

 tufts of small lanceolate, grayish and hairy leaves. Flowers 

 white, very numerous, in short racemes. The variety albida 

 has larger flowers and less toothed leaves. Fine among 

 rocks and on bare hillsides. A. arenom is a plant of sandy 

 fields with bright rose-colored flowers. All grow best in a 

 sandy loam but will also thrive in sterile and gravelly soil. 



Purple Rock-Cress, Aubrietia. — A class of very dwarf, 

 tufted, perennial herbs, with small, grayish foliage and 

 purple flowers in spring. A. deltoidea is the typical form. 

 There are many beautiful varieties with larger, differently 

 colored flowers : A. grandiflora, violet blue, Eyrei, bright 

 puiple, Grceca, reddish-purple, and Leichtlmi, rose-carmine, 

 are common and ornamental forms. All are excellent for 

 rockeries, bare hillsides, sandy fields, and similar open posi- 

 tions. They thrive best in very light, sandy loam mixed 

 with brick-rubbish. 



Whitlow-Grass, Draba. — Beautiful dwarf plants of 

 sandy fields and sunny mountain-sides, growing only a few 

 inches high, and forming dense tufts of grayish foliage, 

 covered with white or yellow flowers in early spring. 

 Should be grown in masses only in the same manner as rock- 

 cress. Among the numerous species the following are best 

 for general use: D. Aizoon and Aizoides, two or three 

 inches high, tufted, leaves almost linear. Flowers very 

 numerous in early spring, bright yellow. D. Mawei, very 

 dwarf, tufted with linear leaves and large white flowers. 

 D. pyrenaica, flowers white, changing to purple. All may 

 be raised from seeds or by means of division. 



