68 , POLYGOXACE.\E 



Involucres peduncled: leaves and bracts similar, verticillate, 

 linear; caulescent annuals. XX. Sperguli.\.\. 



Perianth herbaceous, closely investing the achene: involucre divided 

 to near the base; leaves spatulate; caulescent annuals. 



XXI. S.\.LSUGIXOS.\. 



I. Al.\t.4^. 

 Involucres hairy, 3-3.5 mm. long and 1.5-2 mm. wide; stem and leaves manifestly hirsute 



and tomentose. 1. E. alalum. 



Involucres glabrous, 2-2.5 mm. long and of the same width; stem and leaves nearly 



glabrous. 2. E. triste. 



II. ERI-tNTHA. 



Perianth whitish; style hairy at least to the middle. 3. E. Jamesii. 

 Perianth yellow; style hairy only at the base. 



Involucres 6-8 mm. long; leaf-blades oblong or oblanceolate. 4. E. Bakeri. 



Involucres 9-10 mm. long; leaf-blades suborbicular to oval. 5. E. arcuatum. 



III. Fl.^^va. 



Perianth (externally) pubescent tlu-oughout. 



Involucre elongated-obconic, 6-S mm. long. 6. E. Piperi. 



Involucre tiu-binate, 4-5 mm. long. 



Stipe-like base of the perianth very short; old leaf-bases permanently tomentose. 

 Leaf-bases tliickened; perianth copiously pubescent; leaf-blades silky above; 



involucres usually several. 7. E. flavum. 



Leaf-bases not thickened; leaf-blades slightly floccose above; involucres few. 

 Periantli 6-7 mm. long. 8. E. chloranthum. 



Perianth about 4 mm. long. 9. E. polyphyllum. 



Stipe-Uke base of the perianth slender; old leaf-bases glabrous. 



10. E. zanthnm. 

 Perianth pubescent at the base only. 11. E. androsaceum. 



IV. C.^ESPITOS.\. 



Involucres with comparatively short, ovate, merely spreading lobes, long-peduncled ; 



leaves linear or nearly so, revolute; stems short, leafy. 12. E. thymoides. 



Involucres with long refle.xed lobes. 



Densely cespitose, subacaulescent ; involucre solitary. 



Perianth in flowers .3-4 mm. long. 13. E. caespilosum. 



Perianth in flowers 2 mm. long. 14. E. andinum. 



Caulescent, suffruticose ; involucres 1-5. 



Perianth greenish yellow, 6-8 mm. long; leaves spatulate or oblanceolate. 



15. E. sphaerocephal'im. 

 Perianth ochroleucous, 5 mm. long; leaves Unear or linear-oblanceolate. 



16. E. fasciculifolium. 

 V. Ptrol.\efoli.\. 



One species. 17. E. pyrolaefolium. 



VI. UmbelLu\ta. 

 Leaf-blades ovate or cordate. 18. E. compositum. 



Leaf-blades from obovate or orbicular to oblanceolate. 



Involucres solitary. 19. E. Porteri. 



Involucres several, umbellate. 

 Perianth deeply yellow. 



Leavas not densely tomentose beneath. 



Umbels simple; leaves spatulate. 20. E. neglectum. 



Umbels more or less compound; leaves oblanceolate. 



21. E. biumbellatum. 

 Leaves densely tomentose beneath. 



Inflorescence more or less compound. 22. E. stellatum. 



Inflorescence simple. 



Leaf-blades obovate-spatulate or oval; perianth 6-7 mm. long. 



23. E. umbellatum. 

 Leaf-blades rhombic-ovate or rhombic-oval; perianth 7-8 mm. long. 



24. E. Rydbergii. 

 Perianth ochroleucous, in age turning purplish rose-colored. 



Scape naked up to the umbel; leaves spatulate. 



Perianth about 6 mm. long; leaf-blades spatulate-oblong or elliptic, glabrous 



above at maturity. 25. E. subalpinum. 



Perianth about 8 mm. long; leaf-blades oval or ovate, permanently tomen- 

 tose above. 26. E. ariditm. 

 Scape with at least one whorl of leaves below the umbel : leaf-blades oblanceo- 

 late. 27. E. heracleoides. 



VII. L.VCHXOGY.VA. 



Leaves and scape silky; the latter elongate, 1 dm. high or more; perennials with a taproot 

 and cespitose crovsm. 

 Inflorescence irregularly branched. 28. E. lachnogynum. 



Inflorescence subcapitate. 29. E. Tetraneuris. 



Leaves lanate, subsessile, obtuse: scape short, less than 3 cm. long, or none; pulvinate- 

 cespitose perennials; involucres capitate. 

 Leaf-blades elliptic or oval, not strongly revolute; scape 1-3 cm. long. 



Perianth yellow; lobes of the involucres lanceolate, more than twice as long as the 



tube. 30. E. longilobum. 



Perianth white or pinkish; lobes of the involucres not twice as long as the tube. 



