BUCiaVHEAT FAMILY . 67 



stigmas not tufted. 



Leaf-blades jointed at the base; ocreae 2-lobed, becoming lacerate; filaments, 



at least the inner, dilated. 9. Polygonum. 



Leaf-blades not jointed at the base; ocreae not 2-lobed; filaments slender. 

 Ocreae cylindric, truncate. 10. Persicahl\. 



Ocreae oblique, more or less open on the side facing the leaf. 



Herbs, not climbing or twining; sepals neither winged nor keeled. 



Flowers in simple spike-like racemes; plants with thickened tuberous 



rootstocks. 11. BiSTORTA. 



Flowers in several racemes or panicles; rootstocks not tuberous-thick- 

 ened. 

 Racemes in terminal corymbs; plants smooth. 



Embryo in the center of the endosperm; leaves sagittate or 



cordate. 12. Fagopyrum. 



Embryo at one side of the endosperm; leaves neither sagittate 

 nor cordate. 13. Aconogonum. 



Racemes not in terminal corymbs; plant prickly; embryo at one 

 side of the endosperm. 14. Tracaulon. 



Herbaceous vines, with twining stems; sepals winged or keeled. 



15. Bilderdykia. 



1. ERIOGONUM Michx. Umbrella Plant. 



Aclienes 3- winged; perianth not accrescent; perennials with a thick taproot and short 



crown. I. Alata. 



Achenes merely 3-angled; perianth accrescent in fruit. 



Perianth with a stipe-like base; bracts verticillate, leaf-like. 



Involucres in branching cymes; perennials with a branched woody caudex; flower- 

 ing bra nches scapiform. II. Eriantha. 

 Involucres in simple or compoiuid umbel-like or head-Uke clusters. 

 Perianth ijubescent. 



Perianth yellow; leaf-blades spatulate or oblanceolate. 



Involucres undulate-dentate, tomentose, many, umbellate; embryo 



straight; perennials with a cespitose caude.x. III. Flava. 

 Involucres deeply lobed, solitary, or 2 or 3 together; embryo curved; 

 perennials, subacaulescent or suffruticose. IV. Caespitcsa. 



Perianth wliite; leaf-blades ovate or eUiptic; cespitose subacaulescent 

 perennials. V. PyroLl.\efolia. 



Perianth glabrous; perennials with a cespitose caudex, with the leaves clustered 

 at the ends of the branches. VI. Umbellata. 



Perianth without stipe-Uke base. 



Ovaries and fruit pubescent; involucres few, capitate or subcymose; perennials 



with scapiform stems. VII. Lachnogyna. 



Ovaries and fruit glabrous or nearly so. 



Involucres in head-like or umbellate clusters. 



Perianth-lobes very unequal; perennials with a pulvinate-cespitose woody 

 caudex. VIII. Heterosepala. 



Perianth-lobes equal or nearly so. 



Heads solitary or, if more than one, proliferous-umbellate, with the 



central head sessile; cespitose perennials. IX. C.\pitata. 



Heads several, paniculate, corymbose or cymose-umbellate. 



Herbs with perennial caudices; heads paniculate, almost ebracteate; 



perennials with a stout rootstock. X. Elata. 



Leafy undershrubs, with fascicled leaves; heads cymose-umbeUate ; 

 suffruticose perennials. XI. Fascicul.\ta. 



Involucres in open cymes. 

 Bracts scale-Uke. 



Involucres, except those of the forks of the inflorescence, sessile, the 

 uppermost conglomerate. 

 Cymes repeatedly dichotomoiis or trichotomous. 

 Perianth-lobes very dissimilar; perennials. 



XII. DiCHOTOMA. 



Perianth-.segments not very dissimilar. 



Perennials, shrubby at least at the base. 



XIII. CORYMBOSA. 



Annuals, with a strict herbaceous stem. 



XIV. Annua. 

 Cymes with more or less raceme-Uke branches. 



Perennials. XV. Racemosa. 



Annuals. XVI. Virgata. 



Involucres all peduncled, never conglomerate; scapose annuals (except 

 E. tenellum): leaves basal, petioled. XVII. Pedunculata. 



Bracts leaf-like. 



Primary stem-leaves scale-Uke, with a pair or a fascicle of secondary 

 well-developed leaves in their axils; caulescent annuals. 



XVIII. DIVARICATA. 



Primary stem-leaves well-developed, also often with secondary leaves 

 in their axils. 

 Perianth petaloid, not closely investing the achenes; involucres 

 toothed or lobed. 



Involucres sessile; leaves basal, petioled; bracts sessile, elliptic; 

 scapose annuals. XIX. Puberula. 



