STANDLEY TEEES AND SHRUBS OF MEXICO. 1257 



Calyx lobes acuminate. 

 Leaves ovate or ovate-oblong, 3 to 7 mm. long, all slender- 



petiolate 14. S. serpyllifolia. 



Leaves oblong, 10 to 25 mm. long, the uppermost subsessile. 

 Leaves finely stellate-pubescent, at least v/hen young. 



15. S. coahuilensis. 



Leaves glabrous 16. S. lycioides. 



CO. Leaves crenate or crenate-serrate. 

 Calyx lobes becoming much broadened in age, the calyx funnelform. 

 Leaves green above, usually rugose, regularly crenate. 



Calyx finely and closely tomentose 17. S. ballotaeflora. 



Calyx loosely and coarsely stellate-tomentose. 



18. S. ramosa. 

 Leaves very pale on both surfaces, irregularly crenate. 



19. S. platycheila. 

 Calyx lobes not broadened in age or scarcely so. 



Mature leaves glabrous 20. S. similis. 



Mature leaves pubescent on one or both surfaces. 

 Pubescence of the leaves of stellate hairs. 



Stems very densely and finely white-tomentulose ; verticels 



6 to 10-flowered 21. S. cedrosensis. 



Stems thinly stellate-tomentose ; verticels 2 to 6-flowered. 



22. S. chamaedryoides. 

 Pubescence of the leaves not stellate. 



Leaves obtuse, densely viscid-pubescent on tlie upper surface. 



23. S. purpusii. 

 Leaves acuminate, glabrous or nearly so on the upper 

 surface. 

 Upper leaves sessile ; flowers cymose-paniculate. 



24. S. dasycalyx. 

 Upper leaves long-petiolate ; inflorescence racemose. 



25. S. fallax, 

 BB. Leaves ovate or broadly ovate, usually cordate at base. 

 Leaves glabrous beneath or sparsely puberulent along the nerves. 



4. S. nelsonii. 

 Leaves, at least when young, densely pubescent or tomentose beneath. 

 D. Leaves stellate-pubescent beneath, at least when young. 



Calyx densely white-lanate 26. S. rubropunctata. 



Calyx stellate-tomentose, not lanate except sometimes at l)ase. 



Leaves 1 to 1.5 cm. long 27. S. fruticulosa. 



Leaves 2 to 6 cm. long. 



Branchlets and nerves of young leaves with sulphur-yellow 



tomentum 28. S. conzattii. 



Branchlets and lower surface of leaves with white tomentum. 

 Leaves broadly ovate, sharply crenate-dentate ; calyx lobes 



obtuse 29. S. pruinosa. 



Leaves oblong-ovate, obtusely crenate; calyx lobes acute. 



30. S. goldmanii. 

 DD. Leaves white-tomentose beneath with simple hairs. 



E. Leaves very rugose above, usually broadly ovate, obtuse. 

 Pedicels very short, 3 mm. long or less ; racemes rather dense ; 

 calyx in anthesis 4 to 5 mm. long. 

 Calyx glandular-villous 31. S. scordoniaefolia. 



