Key Based on Vegetative and Floral Characters (for New Mexico and 



Arizona species) 



1. Prostrate miniature shrub with stems on or just below surface of ground, 

 commonly forming mats; alpine or subalpine (2) 



1. Erect or ascending shrubs or trees with stems usually 5 dm. tall or more; at 

 lower elevations, rarely alpine (3) 



2(1). Aments serotinous, terminating the short leafy shoots of the season; scales 

 pale, inconspicuously short-hairy within, otherwise glabrous; fila- 

 ments inconspicuously short-hairy toward the base; style very short, 

 it and the stigmas together less than 1 mm. long 13. S. nivalis. 



2. Aments coetaneous, terminating short leafy lateral branches, the principal 



vegetative shoots of the season not ending in aments; scale dark, 

 ordinarily conspicuously long-hairy (at least on the margins), the 

 hairs much surpassing the body of the scale; filaments glabrous; 

 style often longer, it and the stigmas together well over 1 mm. 

 long 14. S. arctica. 



3(1). Petioles very short (not more than 3 mm. long) or none; leaves linear- 

 lanceolate to narrowly oblanceolate, sericeous (at least beneath); 

 seldom more and usually much less than 7 mm. wide or rarely to 

 12 mm. in S. exigia, the margins entire or remotely denticulate; 

 stamens 2 (4) 



3. Petioles more than 3 mm. long or (if shorter) then the larger leaves more than 



7 mm. wide or closely serrate or serrulate (5) 



4(3). Leaves oblanceolate, sessile or very nearly so, at maturity not more than 

 3 cm. long; capsules silky-villous, then glabrate 10. S. taxi folia. 



4. Leaves linear-lanceolate, short-petioled, at maturity 5 cm. long or more; 



capsules glabrous 11. S. exigua. 



5(3). All leaves with entire margins (6) 



5. At least some or all of leaves with serrulate to serrate or crenulate-dentate 



magins (7) 



6(5). Leaves 2-4 cm. long, subglaucous beneath; staminate aments 7-15 mm. 

 long; pistillate aments 1-2.5 cm. long at maturity; style to about 

 0.4 mm. long 22. S. Geyeriana. 



6. Leaves 4-6 (-8) cm. long, the margins often revolute, silvery appressed- 



pubescent beneath; staminate aments 20-30 mm. long; pistillate 

 aments 2-6 cm. long at maturity; style mostly 0.6-1.3 mm. long 

 26. S. Drummondiana. 



7(5). Margins of the leaves entire or with some obscurely serrulate (8) 



7. Margins of all the leaves noticeably serrate to serrulate or dentate to crenulate 



(16) 



8(7). Leaves rounded to subcordate at base, green but paler beneath 



19. 5. myrtillifolia. 



8. Leaves acutish to somewhat cuneate or attenuate at base, typically white or 



whitish beneath (9) 



9(8). Capsules thin-hairy or silky-pubescent (10) 



9. Capsules glabrous; leaves lanceolate to oblanceolate, acute to acuminate at 



apex, glabrous and often shiny above (14) 



10(9). Stigmas elongate, mostly 0.5-1 mm. long; twigs not glaucous, usually 

 glabrous; leaves broadly to narrowly obovate or elliptic-obovate, 

 glabrous above at maturity, widest above the middle (11) 



10. Stigmas shorter than above, 0.2-0.5 mm. long; twigs glaucous or more or less 



pubescent; leaves not broadly obovate, more or less pubescent above 

 (especially on main veins), mostly (but not always) widest at or 

 below the middle (12) 



755 



