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



summer when the grasses are at their best, accounts for this seeming 

 neglect. Several of the Arizona tickclovers are recommended for 

 erosion control. 



Key to the species 



1. Leaves all 1-foliolate; plant perennial; segments of the fruit normally not 

 contorted (2). 

 2. Flowering stems more or less woody near the base; leaflet very long and nar- 

 row, not more than 5 mm. wide; fruit sessile__ 1. D. angustifolium. 



2. Flowering stems not woody; leaflet much shorter and broader, 12 to 28 mm. 



wide ; fruit stipitate 2. D. wrightii. 



1. Leaves 3-foliolate or, if some or all of them 1-foliolate, then the plant annual 

 and the segments of the fruit normally somewhat contorted (3). 



3. Bracts very conspicuous before anthesis, densely imbricate at the ends of 



the branches, mostly ovate and 8 to 10 mm. long, attenuate-acuminate; 

 stems procumbent to nearly erect, usually densely pubescent, the hairs 

 uncinate; leaflets ovate-lanceolate to broadly rhombic-ovate; fruit usually 

 pubescent, the segments normally contorted, about 3 mm. long. 



3. D. INTORTUM. 



3. Bracts not very conspicuous or densely imbricate or, if so, then not more than 

 7 mm. long, or narrowly lanceolate or subulate (4). 

 4. Fruit nearly or quite as deeply notched above as below, hence appearing 

 moniliform (5). 

 5. Plant perennial; stems diffuse or procumbent; leaflets oblong-lanceolate 

 or ovate-lanceolate to ovate; fruit glabrous or puberulent, the 

 segments 3 mm. long or shorter, normally not contorted. 



4. D. retinens. 

 5. Plants annual (6). 



6. Segments of the fruit orbicular to elliptic, not contorted, the margins 



flat or nearly so; leaves all much alike and trifoliolate (7). 



7. Leaflets ovate, the larger ones 15 to 50 mm. wide; segments of the 



fruit at maturity 6 to 10 mm. long, sparsely pubescent, at least 



on the sutures 5. D. psilocarpum. 



7. Leaflets linear or linear-lanceolate, not more than 5 mm. wide; 



segments of the fruit at maturity less than 5 mm. long, glabrous 



or nearly so 6. D. rosei. 



6. Segments of the fruit rhombic or the terminal one triangular, pubescent 

 at least on the sutures, the terminal 1 or 2 segments sometimes 

 glabrous, all or some of them slightly to strongly contorted, the 

 margins involute or revolute (8). 



8. Terminal segment of the fruit triangular, not contorted, distinctly 



larger than the others, 7 to 8.5 mm. long; leaves all trifoliolate, 

 the leaflets of much the same shape throughout the plant and 



longer than wide 7. D. scopulorum. 



8. Terminal segment much like the others in shape and contortion, if 



larger then not triangular, none of the segments more than 4 



mm. long; leaves differentiated, the basal ones with leaflets 



mostly wider than long, often unifoliolate (9). 



9. Fruit usually sessile or nearly so, the segments 3 to 5 (rarely 



only 2), moderately contorted; leaflets of the upper leaves 



lanceolate to ovate; bracts usually persistent; some or all 



of the upper leaves rarely unifoliolate. 



8. D. NEOMEXICANUM. 



9. Fruit distinctly stipitate, the segments 2 or 3, strongly contorted 

 (the 4 sides alternately involute and revolute on the margin) ; 

 leaflets of the upper leaves linear or linear-lanceolate; 



bracts often early deciduous 9. D. procumbens. 



4. Fruit less deeply notched above than below, the segments normally not 

 contorted; plants perennial, often with a woody caudex (10). 

 10. Stems diffuse or procumbent; leaves dark green above, pale or some- 

 what glaucous beneath; bracts conspicuous before anthesis, 6 mm. 

 long or shorter, imbricate, ovate or lance-ovate, attenuate-acumi- 

 nate; pubescence uncinate (11). 

 11. Segments of the fruit 5 to 8 mm. long, very pubescent; leaflets ovate, 

 often conspicuously reticulate beneath, the terminal one less than 

 twice as long as wide; bracts ovate-lanceolate, not closely im- 

 bricate 10. D. GRAHAMI. 



