758 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



Key to the species 



1. Nutlets tessellate with broad flattened contiguous pavementlike tuberculations; 

 plant erect, hispid, with terminal bractless scorpioid cymes__ 1. P. jonesii. 

 1. Nutlets not tessellate, the back wrinkled or with ridges, the tuberculations 

 scattered, or none (2) . 

 2. Leaves charged with a purple dye, particularly about the midrib and mar- 

 gins; calyx circumscissile, the lobes short and strongly connivent at 



maturity ; nutlets incurved 2. P. arizonictts. 



2. Leaves green, lacking a conspicuous purple dye; calyx not circumscissile (3). 



3. Basal leaves crowded into a distinct rosette, none opposite; plant slender, 



erect, loosely branched, not producing flowers near the base; nutlets 



contracted at both ends, somewhat cruciform, incurved, the transverse 



ridges very broad and separated by grooves 3. P. tenellus. 



3. Basal leaves distinct or at least not in a well-developed rosette, the lower 



leaves opposite; plant decumbent or prostrate, frequently floriferous 



throughout, even in the axils of the lowermost leaves; nutlets not 



incurved, rounded at base, the ridges well spaced (4). 



4. Plant sparsely strigose, very slender; nutlets flattened, lanceolate, 



attached by a broadly affixed sessile ovate scar borne below the 



level of the ventral keel, the back with low rounded irregular 



ridges 4. P. cognatus. 



4. Plant distinctly hispid, rather coarse; nutlets ovoid, not compressed, 



usually with sharp narrow ridges, attached by a scar elevated to the 



level of the ventral keel and more or less stiped (5) . 



5. Stipe of the nutlet elongate, about equaling the body of the nutlet 



in length; nutlets commonly united in pairs. _5. P. pringlei. 



5. Stipe of the nutlet very short; nutlets separate. 



6. P. CALIFORNICTJS. 



1. Plagiobothrys jonesii A. Gray, Syn. Fl. ed. 2, 2 1 : 430. 1886. 



Sonnea jonesii Greene, Pittonia 1: 23. 1887. 



Mohave, Maricopa, Pinal, and Yuma Counties, eastward in and 

 near the valley of the Gila River to eastern Pinal County, mostly 

 below 2,000 feet, dry sandy and gravelly soils on slopes and in valleys of 

 the creosotebush belt. Southwestern Utah to south-central and west- 

 ern Arizona, and adjacent California. 



2. Plagiobothrys arizonicus (A. Gray) Greene in A. Gray, Amer. 



Acad. Arts and Sci. Proc. 20: 284. 1885. 



Eritrichium canescens (Benth.) A. Gray var. arizonicus A. 

 Gray, ibid. 17: 227. 1882. 



Mohave and Yavapai Counties south to Cochise and Pima Counties, 

 3,600 feet or lower, frequently among bushes or rocks, creosotebush 

 and oak belts, types from Tucson (Greene, Pringle). 



Western New Mexico to southern Nevada, California, and northern 

 Sonora. 



3. Plagiobothrys tenellus (Nutt.) A. Gray, Amer. Acad. Arts and Sci. 



Proc. 20: 283. 1885. 



Myosotis tenella Nutt., Jour. Bot. and Kew Gard. Misc. 3: 295. 

 1851. 



Known in Arizona from only a few scattered stations, near Superior 

 (Pinal County), Pinaleno Mountains (Graham County), Santa Cata- 

 hna Mountains (Pima County), probably in the oak belt. Idaho and 

 Washington to southern Arizona and southern California. 



