BUCKWHEAT FAMILY 211 



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

 ened. 

 Racemes in terminal corymbs; plants smooth. 



Embryo in the center of tlie endosperm; leaves sagittate or 



cordate. 12. Fagopyrltm. 



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 tlie endosperm. 14. Tracaulon. 



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



15. BILDERDTKIA. 



1. ERIOGONUM Michx. Umbrella Plant. 



Annual or perennial herbs or shrubby plants, with basal or cauline, alternate, 

 opposite, or whorled leaves and no stipules. Blades entire. Flowers perfect or 

 polygamo-monoecious, in involucrate clusters variously disposed. Involucres 

 turbinate or campanulate, rarely nearly cylindric, 4-8-lobed, Perianth more or 

 less colored, jointed to a short pedicel. Segments 6, in two series. Stamens 9; 

 filaments fiUform, often hairy at the base. Ovary 1-celled, 3-angled or 3-winged; 

 styles 3. 



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



crown. . !• Alata. 



Achenes merely 3-angled; perianth accrescent in fruit. 



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



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

 ing branches scapiform. II. Eriaxtha. 

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



Perianth pubescent. 



Perianth yellow; leaf-blades spatulate or oblanceolate. 



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



straight; perennials with a cespitose caudex. III. Flava. 

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

 perennials, subacaulescent or suflfruticose. IV. Caespitosa. 



Perianth white; leaf-blades ovate or elliptic; cespitose subacaulescent 

 perennials. V. Pyhol.\efoli a . 



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

 at the ends of the branches. VI. Um^ell.\ta. 



Perianth without stipe-like base. 



Ovaries and fruit pubescent; involucres few. capitate or subcymose; perenmals 



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. Capitata. 



Heads several, paniculate, corymbose or cyraose-umbellate. 



Herbs with perennial caudices; heads paniculate, almost ebracteate; 



perennials with a stout rootstock. X. Euata. 



Leafy undershrubs. with fascicled leaves; heads cymose-umbellate; 

 suflfruticose perennials. XI. Fascicul.\ta. 



Involucres in open cymes. 



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



uppermost conglomerate. 

 Cymes repeatedly dichotomous 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. Anxta. 



Cymes with more or less raceme-like branches. 



Perennials. XV. Racemosa. 



Annuals. XVI. ViRGATA. 



Involucres all peduncled, never conglomerate; scapose amiuals (except 

 JS. tenellum); leaves basal, petioled. XVII. PzDr^xULATA. 



Primary stem-leaves scale-like, 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; mvolucrea 



toothed or lobed. 



