Flora of Denver. 5 



flowers, herbage smooth and glaucous, stems hollow, seeds shin- 

 ing and black. Common along the North Denver and Val- 

 verde hillsides above the Platte, Cherry Creek. Spring, sum- 

 mer. 



CRUCIFER/E. (Mustard Family.) 



16. Arabis hirsute SCOP. (HAIRY ROCK-CRESS.) Bien- 

 nial, flowers inconspicuous, wingless seeds in one row in each 

 cell of the ascending pods. Along the Platte. Spring, summer. 



17. Arabis perfoliata LAM. Biennial,stem leaves glaucous 

 and clasping by the sagittate base, pods erect with two rows of 

 seeds in each cell. Along the Platte. Summer. 



18. Arabis Holboellii HORNEM. Perennial, flowers larger, 

 pods spreading downwards with two rows of seeds in each cell 

 Along the Platte. Spring and summer. 



19. Draba cuneifolia NUTT. (WHITLOW GRASS.) Low 

 with stellate pubescence and small white flowers in racemes. 

 Rare around Denver; on the plains in early spring. 



20. Camelina sativa CRANTZ. (FALSE FLAX.) An intro- 

 duced annual with small yellow flowers and numerous pear- 

 shaped margined pods. Rare. Valverde, University Park. 



21. Nasturtium officinale R. BR. (WATER CRESS.) The 

 common water-cress found growing in the springs near the 

 Platte and Cherry Creek. Introduced. 



22. Nasturtium palustre DC. (MARSH CRESS.) Annual, 

 erect, short pods tipped with a short style, leaves pinnately 

 cleft and divisions cut toothed. There is also a low spreading 

 form in fields. In wet places. 



23. Erysimum asperum DC. (WESTERN WALL-FLOWER.) 

 Flowers yellow in racemes, fragrant, pods long, four-sided, 

 spreading horizontally. North Denver and Valverde hills, 

 spring and summer. 



