POLYPTERIS— PTILOCALAIS 289 



Stems 1-3 ft. high, sticky; leaves lanceolate, 2-4 in. 



long ; rays 8-10 P. hookeridna 



Prexaxtiiella Rydberg 1906 

 (Diminutive of Prenanthes) 

 Heads with rose or pink perfect strap-flower's, achenes wedge-shaped, 

 4-5-ribbed, pappus of white, hair-like bristles ; receptacle flat, without chaff, 

 involucre oblong, with 1 row of oblong bracts and 1-2 small basal ones; 

 heads solitary at the ends of the branches ; leaves alternate, entire to pin- 

 natifid ; annual. 



Stems 4-10 in. high; leaves spatulate to oblong; in- 

 volucre 4 mm. high, 4-5-flowered P. e.vigua 



Prexaxthes Linne 1753 Rattlesnake Root 

 (Gr. prenes, drooping, anthos, flower) 

 (Nabalus Cass.) 

 Heads of white, yellowish or purplish perfect strap-flowers, achenes 

 oblong or cylindric, round or 4-5-angled, ribbed, pappus of white to red- 

 dish-brown, hair-like bristles ; receptacle flat, without chaff, involucre cy- 

 lindric, the main bracts in 1-2 rows, a few small ones at the base ; heads 

 in panicles ; leaves alternate, dentate to pinnatifid ; perennial. 



1. Basal leaves obovate ; involucre somewhat hairy P. racemosa 



2. Basal leaves arrow-shaped ; involucre smooth P. sagittdta 



Psilostrophe DeCandolle 1838 

 (Gr. p silos, naked, strophe, ridge) 

 Heads with 3-4 yellow pistillate ray-flowers, disk-flowers 5-12, 

 yellow, perfect, achenes linear, striate, pappus of 4-6 scales ; receptacle 

 small, without chaff, involucre cylindric, bracts white-woolly, 4-10 in one 

 row ; heads in corymbs ; leaves alternate, entire to pinnatifid ; annual or 

 perennial. 



Stems 4-12 in. high; leaves entire to 3-lobed or pin- 

 natifid ; rays 3-5, broad and 2-3-lobed ; pappus scales 

 acute to obtuse P. tagetimi 



Ptilocalais Greene 1886 

 (Gr. ptilon, feather; Calais) 



Heads with yellow perfect strap-flowers, achenes linear, pappus of 

 white, hair-like bristles, scale-like at base ; receptacle flat, without chaff, 

 involucre cylindric, the main bracts in 1 row with a few short basal ones ; 

 heads solitary on the ends of branches ; leaves entire to pinnately parted ; 

 perennial. 



Stems 4-12 in. high ; leaves spatulate-obovate or part- 

 ed into linear lobes; heads 8-20-flowered P. nutans 



