340 FLORA OF TEXAS. 



PLUCHEA, Cass. 



Heads many-flowered ; the ccwivsiX floiuers mostly perfect, 

 but sterile, with the corolla dilated and 5-cleft, the others 

 pistillate, slender, slightly toothed; antJiers bicaudate; 

 scales of the involucre imbricated ; receptacle flat, mostly 

 naked ; achenia grooved or angled ; pappus a single row 

 of capillary slightly scabrous bristles. — Odorous mostly 

 pubescent and glandular herbs, with alternate ovate or 

 oblong serrate leaves; heads of purplish flowers corymbose. 



P. BiFRONS, DC. Stem simple, or sparingly branched; 

 leaves oblong, acute, denticulate, strongly reticulated and 

 rugose, cordate and clasping; heads clustered; involucre 

 pubescent and viscid. Stem l°-2° high; jioiuers pale pur- 

 ple or white. 



P. FCETiDA, DC. Minutely pubescent and glandular; 

 leaves large, membranaceous, ovate-lanceolate, acuminate, 

 serrate, tapering into a petiole ; corymbs axillary and ter- 

 minal; heads rather small, numerous, on slender pedicels; 

 involucre smoothish, often purplish. Stem 2°-5° high; 

 leaves 5-8' long, resinous-dotted; flowers purple. 



pterocaulo:n', eii. 



Heads spiked; scales of the involucre lanceolate, imbri- 

 cated in several rows, caducous ; leaves lanceolate, tomen- 

 tose and hoary beneath, the margins decurrent on the stem ; 

 receptacle hairy; achenia angled, pubescent; pap r us of 

 numerous capillary bristles, longer than the invducre. 

 Heads many-flowered, central flowers mostly perfect, but 

 sterile, with the corolla dilated and 5-cleft, the others pis- 

 tillate. 



P. pyc:n'ostachyum. Ell. Leaves wavy, smooth; stem 

 l°-2° high ; spiJcG thick, woolly; floivers white. 



