262 COMPOSITE. Ptkrocaulon. 



59. PTEROCAULON. Ell. sk. 2. p. 333 (1824); DC. prodr. b.p. 453. 



Heads many-flowered ; the fertile flowers filiform, pistillate, in several 

 series; the perfect flowers in the centre (or intermixed with the others, Ell.), 

 mostly sterile. Scales of the oblong involucre imbricated in several series, 

 appressed or with slightly squarrose points, caducous. Receptacle mi- 

 nutely fimbrillate or hirsute. Corolla of the fertile flowers 3-toothed ; the 

 sterile 5-cleft at the summit. Anthers bicaudate, somewhat exserted. Ache- 

 nia angled, pubescent with appressed hairs. Pappus of numerous capillary 

 scabrous equal bristles, longer than the involucre. — Perennial herbs, or 

 sliglitly shrubby jilants (chiefly natives of tropical America), with a some- 

 what tuberous rhizoma. Leaves alternate, lanceolate, entire or denticulate, 

 very densely toraentose beneath, the margins decurrent along the stem into 

 continuous foliaceous wings. Heads sessile, densely crowded in simple or 

 compound spikes. Flowers usually white. 



1. P. jjycnostachyum (E\\.): stem herbaceous, simple; leaves lanceolate, 

 undulate-denticulate, glabrous above ; heads in a dense continuous spike ; 

 scales of the involucre silUy-tomeniose, squarrose at the apex. — Ell. I. c. ; 

 DC! I. c. Conyza pycnostachya, Michx.! fl. 2. p. 126 ; Pursh ! fl. 2. p. 

 524. Chlsenolobus pycnostachyos, Cass, in diet. sci. 7iat. 49. p. 348 (1827). 

 Pluchea pycnostachya, Z,ess. Gnaphalium undulatum, Walt.! Car. p. 202. 



Dry sandy soil, S. Carolina! to Florida! May-Aug. — Black Root. (The 

 root is mucli used in some parts of the country as an alterative, and as a 

 cleanser of old ulcers. Elliott.) 



60. CALYMMANDRA. 



Heads subglobose, subsessile, collected in small axillary clusters, many- 

 flowered, heterogamous; the flowers all fertile; the pistillate in many series, 

 in the axils of narrow and plane linear or somewhat spatulate scarious (vil- 

 lous-lanate) chafl'of the receptacle, with a filiform truncate corolla; the per- 

 fect 5 in a single central series, each enclosed in an oval convolute woolly 

 chaff"; the short and somewhat inflated minutely 4-toothed corolla more or 

 less exserted. Scales of the involucre few, similar to and passing into the 

 chaff. Receptacle conical, punctate. Anthers with very short tails. Branch- 

 es of the style short ; in the perfect flowers oblong, flat ; in the pistillate fili- 

 form. Achenia oval-oblong, nearly terete, very smooth, destitute of pappus, 

 those of the perfect flowers similar, but enclosed by the subtending chaff. — 

 A small annual herb, branched from the base, clothed with a very white and 

 silvery appressed wool ; the branches slender, somewhat simple, erect, bear- 

 ing small bracteate or irregularly involucrate clusters of few heads, closely ses- 

 sile in the axils of linear-oblanceolate or narrowly spatulate entire leaves; the 

 heads themselves (about a line long) on short pedicels concealed by the wool. 



C. Candida. 



Texas, Druminond ! — Plant 5-10 inches high. Leaves alternate, approxi- 

 mate, half an inch or more in length, very much longer than the clusters in 



