KEY TO THE SPECIES 29 



1. Stanleya pinnata (Pursh) Britt. (Stanleya). Stems 5-10 dm. high ; 

 leaves from nearly entire to deeply pinnatifld ; sepals linear, the petals with a 

 long claw ; filaments exserted ; sillques ^3 times as long as the style. 



2. LEPIDIUM (Peppbr-geass) 



Herbaceous plants with entire, toothed or pinnatifld leaves and mostly small 

 white flowers. 



1. Lepidium ramosissimum Aven Nelson (Branched Fepper-orass). 

 Freely branched from the base up, 2-4 dm. high ; leaves pinnately toothed ; petals 

 small, spatulate, half as long as the sepals ; the fruiting racemes long and numer- 

 ous ; siliques ovate with a broad shallow sinus. Waste grounds and open stony 

 plains. 



2. Lepidiuxn montanum Nutt. (Large-flowered Lepidium). Stems sev- 

 eral, 1-8 dm. long, loosely spreading ; leaves pinnatifld ; flowers conspicuous, 

 white or yellowish-white ; siliques elliptical, with a shallow notch and au evident 

 style. Frequent on alkaline flats. 



3. THLASPI (Penny Cress) 



Small perennials with mostly entire leaves, conspicuous white flowers, and ob- 

 cuneate siliques. 



1. Thiaspi Coloradense Eydb. (Colorado Candytuft). The stems few to 

 many from the crown of a tap-root, 5-10 cm. long ; root-leaves rosulate, elliptic or 

 broader, petioled ; stem-leaves ovate, sessile by an auricled base ; the silique 

 about 6 mm. long, obscurely retuse. Moist draws in the foothills. 



4. SISYMBRIUM 



Slender perennial herbs, glabrous, with nearly entire linear-oblanceolate 

 leaves. 



1. Sisymbrium linifolium Nutt. (Mountain Mustard). Glabrous and 

 glaucous, 3-5 dm. high, with several slender simple stems ; leaves thick ; flowers 

 light yellow ; siliques divaricate, on short pedicels ; seeds in 1 row. Frequent on 

 sandy plains and slopes. 



5. RORIPA (Cress) 



Perennial herbs from rhizomes, with sinuate pinnatifld leaves ; flowers with 

 spreading sepals and conspicuous petals. 



1. Roripa sinuata (Nutt.) A. S. Hitch. (Spreading Cress). Stems several, 

 spreading-prostrate, 1-3 dm. long; leaves oblong-lanceolate in outline, mostly 

 deeply pinnatifld ; siliques acute at both ends, often curved, beaked by a slender 

 style. Abundant in wet, waste grounds and on saline flats. 



2. Roripa Nasturtium (L.) Rusby (True Water-Cress). Stems spreading 

 and rooting; leaves with 3-11 roundish or oblong nearly entire leaflets; petals 

 white, twice the length of the calyx ; pods linear, ascending on slender widely 

 spreading stalks. Cultivated from Europe, but escaped Into brooks and ditches, 



6. CARDAMINE (Bitter Cress) 



Erect glabrous plants, growing along streams, with rather large white flowers; 

 the leaves lobed or lyrately pinnate ; siliques flattened, mostly linear. 



