356 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



8. Rorippa obtusa (Nutt.) Brit ton, Torrey Bot. Club Mem. 5:169. 

 1894. 



Nasturtium obtusum Nutt. ex Torr. and Gray, Fl. North Amer. 



1 : 74. 1838. 

 Radicula obtusa Greene, Leaflets 1: 113. 1905. 



White Mountains (Apache and Greenlee Counties) in meadows, 

 Baker Butte (Coconino County), bed of the Gila River near Sacaton 

 (Pinal County) where doubtless a stray from the mountains. Michi- 

 gan to Washington, south to Texas, Arizona, and California. 



20. CARDAMINE. Bittercress 



Plant perennial, glabrous or soft-pilose ; leaves conspicuously petio- 

 late, the blades broadly ovate or suborbicular, deeply cordate, shal- 

 lowly sinuate-dentate; petals white; pods ascending on long pedicels, 

 elongate^ rather thick; seeds in 1 row. 



1. Cardamine cordifolia A. Gray, Amer. Acad. Arts and Sci. Mem. 



ser. 2, 4: 8. 1849. 

 San Francisco Peaks (Coconino County), White Mountains (Apache 

 County), 9,000 to 11,000 feet, July and August. Wyoming and 

 Idaho, south to New Mexico and Arizona. 



21. LYROCARPA 



Plants perennial, stellate-canescent ; stems weak and straggling, 

 usually supported on shrubs; leaves lyrate-pinnatifid ; petals elongate, 

 subulate, brown-purple, 1.5 to 2 cm. long; pods indehiscent or tardily 

 dehiscent, irregularly obovoid-triangular, obcordate, often constricted 

 below the apex, flattened contrary to the partition. 



1. Lyrocarpa coulteri Hook, and Harv., London Jour. Bot. 4: 76. 

 1845. 

 Western parts of Maricopa, Pinal, and Pima Counties, southern 

 Yuma County, 2,000 feet or lower, among mesquite and other bushes 

 in partial shade, March and August. Arizona, southeastern Cali- 

 fornia, Sonora, and Baja California. 



22. DITHYREA. Spectacle-pod 



Plants annual, stellate-canescent; stems leafy, erect or decumbent; 

 leaves sinuate-dentate to nearly entire; petals white or yellowish; pods 

 indehiscent or tardily dehiscent, didymous (the 2 cells side by side), 

 strongly flattened contrary to the partition, wider than long; seed 1 in 

 each cell. 



Key to the species 



1. Stems decumbent or spreading; herbage yellowish green; blades of the stem 

 leaves ovate or oblong-ovate, shallowly sinuate-dentate; petals 8 to 12 mm. 

 long, yellowish; pedicels in fruit 2 to 3 mm. long; fruit rather deeply notched 

 both above and below, canescent 1. D. californica. 



1. Stems erect; herbage gray or whitish; blades of the stem leaves linear-lanceolate 

 to ovate-lanceolate, deeply sinuate-dentate to nearly entire; petals 5 to 8 

 mm. long, white; pedicels in fruit seldom less than 10 mm. long; fruit 

 notched below, truncate or very shallowly notched above, canescent or 

 glabrous 2. D. wislizeni. 



