284 COMPOSITE. Partheniom. 



76. PARTHENIUM. Linn.; Gcertn. fr. t. 168 ; DC. prodr.b. i). bZ\. 



Heatls many-flowered ; the ray-flowers 5, pistillate, fertile, somewhat ob- 

 scurely ligulate, one in the axil of each inner scale of the involucre ; those of 

 the disk tubular, sterile by the abortion of the style. Involucre hemispherical, 

 in a double series ; the exterior ovate ; the interior nearly orbicular. Recep- 

 tacle conical or somewhat cylindrical, covered with membranaceous chaffy 

 scales, which are dilated above and somewliat cucuUate, partly sheathing 

 the flowers of the disk, tomentose at the summit. Corolla of the ray very 

 short, obcordate, persistent or marcescent ; of the disk tubular, somewhat 

 dilated above. Staniens inserted towards the base of the corolla : anthers 

 slightly united. Style of the sterile flowers undivided : the branches of the 

 fertile style semiterete, obtuse. Achenia (of the ray) compressed, oval or 

 obovate, smooth, surrounded by a filiform callous margin, which is firmly* 

 coherent at the base with the involucral scale and with a contiguous chaffy 

 scale of the receptacle on each side, at length tearing away from the ache- 

 nium. Pappus 2-squamellate, or somewhat aristate, sometimes nearly ob- 

 solete. — Herbs or suffrutescent (American) plants, somewhat various in 

 habit, canescent or hirsute-scabrous, with alternate undivided or 1-2-pin nately 

 cleft leaves. Heads corymbose-cymose or panicled, rarely solitary. Flow- 

 ers whitish. 



§ 1. Pappus of 2 very small and slender or aivn-like squamellce, sometimes 

 obsolete : j)erennial or suffrutescent : leaves toothed or someioliat incised, un- 

 divided. — Partheniastrum, Dill., DC. 



1. P. integrifolium (Linn.) : stem herbaceous, hirsute-pubescent ; leaves 

 hispid-scabrous, ovate-oblong or lanceolate-oblong, doubly crenate orcrenale- 

 toothed, or sometimes incised ; the upper ones sessile or partly clasping; the 

 lower petioled, often deeply incised at the base ; heads numerous, tomentose, 

 corvmbed ; exterior scales of the involucre somewhat acute. — Linn. ! spec. 

 2. p. 988; Lam. ill. t. 766 ; Michx. ! fl. 2. p. 147 ; Willd. hort. Berol. t. 

 4 ,• Schkuhr, handb. t. 293 ; Null. gen. 2. p. 183 ; Ell. ! sk. 2. p. 474 ; 

 DC. I. c. Partheniastrum Helenii folio, DHL Elth. 1. 225, /. 292. Ptar- 

 mica Virginiana &c., Pluk. aim. t. 53, /. 5, 4" 219, /. 1. 



Dry soil, Maryland ! Virginia ! to Alabama ! and west to Missouri ! 

 Louisiana! and Texas! July-Sept. — Stem 1-2 feet high. Lower leaves 

 3-5 inches long. Heads crowded, about 4 lines in diameter; the scales 

 closely appressed. Ray inconspicuous. 



§ 2. Pappus of 2 oblong obtuse membranaceous squainellee : root annual : 

 leaves hipinnatfid. — Argtroch^ta, Cav., DC. 



2. P. Hysterophorus (Linn.) : hirsute-puberulent and somewhat canescent, 

 diftiisely branched or decumbent ; leaves variously bipinnatifid ; the upper- 

 most linear and undivided ; heads (very small) paniculate; exterior scales of 

 the involucre somewhat acute. — Linn. I. c. ; bot. mag. t. 2275 ; Hook, in 

 cotnpan. to bot. mag. 1. p- 99; DC! I. c. Argyrochajta bipinnatifida, Cav. 

 ic. i. J). 54, t. 378. Villanova bipinnatifida, Ort. dec. p. 48, t. 6. 



Banks of streams. New Orleans, Drummond, Dr. Ingalls ! Texas, Ber- 

 landier! St. Augustine, Florida, Baldicin ! Key West, Mr. Blodgett! 



