ASTER FAMILY 249 



n. Receptacle without bristles 



(111) Leaves alternate or basal, usu- 

 ally without glands 

 r. lnvolucral scales spreading or 



reflexed; stems 2-6 ft. high Helknium 

 s. lnvolucral scales not spread- 

 ing or reflexed ; stems less 

 than 2 ft. high as a rule 

 (r) Involucre densely woolly; 

 leaves parted or divided ; 

 alpine Rydbergia 



(s) Involucre_not densely wool- 

 ly ; leaves entire or if di- 

 vided, .not alpine Actinella 

 (n) Leaves usually opposite, with 

 distinct oil-glands 

 r. Leaves entire, narrow Pectis 

 s. Leaves divided Dysodia 

 (z) Achenes flattened, roundish or 

 swollen, sometimes striate 

 m. Heads small, disk-flowers 1-12 ; 

 rays 1-10 

 (m) Rays 2-3-lobed, 4-15 mm. long Psilostrophe 

 (n) Rays not lobed, 1-2 mm. long Gutierrezia 

 n. Heads large, disk- and ray-flowers 



many; involucres gummy Grindelia 



(b) Rays white to purple 

 x. Marginal flowers not true rays, merely 



ray-like Chaenactis 



y. Marginal flowers true rays 



(x) Rays rose-purple Polypteris 



(y) Rays white Chrysanthemum 



3. Heads with all the flowers ray-like or strap- 

 shaped, the central sometimes imperfect and 

 closed; typically with milky juice 



a. Pappus of blunt scales ; flowers blue Cichorium 



b. Pappus of plumy, hair-like bristles or bristle- 



like scales 



( 1 ) Achenes with a beak, bristles interwoven Tragopogon 



(2) Achenes not beaked 



(a) Flowers pink; pappus plumy Ptiloria 



