344 COMPOSITE COREOPSIS 



BIDENS 



leaves usually all opposite, the lower bipinnately parted or divided, with 

 linear lobes ; the upper trifoliolate, with entire linear leaflets, or the upper- 

 most linear and entire : heads numerous, in open cymes : bracts of the in- 

 volucre more or less scarious-margined, the outer lanceolate to subulate, 

 about a line long ; the inner broad-ovate and 3-4 lines long : rays 8-10 lines 

 long by half as broad, yellow with brown base, obtusely 3-lobed at tbe 

 stlmmit; disk-flowers dark purplish-brown: achenes elliptical, distinctly 

 winged, crowned with 2 short subulate often deciduous teeth. Damp 

 meadows along rivers, Oregon to Brit. Columbia. 



45 BIDENS Tourn. L. Gen. n. 932. 



Annual or perennial herbs with opposite lower leaves and mostly 

 large heads of yellow flowers, Involucre campanulate or hemi- 

 spheric, its bracts in 2 series, distinct or united at base, the outer 

 often foliaceous and much larger than the inner. Receptacle flat 

 or nearly so, chaffy, the chaff subtending the disk-flowers Rays 

 when present, neutral, mostly entire. Disk-flowers perfect, fertile, 

 with tubular 5-toothed corollas. Anthers entire or minutely 

 sagittate at base. Style-branches with short or subulate tips. 

 Achenes flat, quadrangular or nearly terete, cuneate, oblong or 

 linear. Pappus of 2-6 teeth or subulate barbed or hispid awns. 



B. frondosa L. Sp. 852. Glabrous or somewhat hairy annual : stems 

 erect, 2-8 feet high, branching: leaves pinnately 3-5-divided into lanceolate 

 orTsroader sharply serrate and pinnately veiny commonly petiolulate leaf- 

 let^, or the Uppermost undivided: heads usually numerous, ped uncled, 

 about 8 lines high : involucre campanulate becoming hemispheric, its 

 outer bracts more or less foliaceous, often much exceeding the ovate-lance- 

 olate scarious-margined inner ones : rays none, or rudimentary and incon- 

 spicuous: achenes flat, oval or obovate, ciliate, with 2 slender downwardly 

 barbed awns. Moist places mostly along streams, Qregon to Brit. Colum- 

 bia and across the Continent. 



B. cernua L. Sp. 832. Annual : stems glabrous or setulose-hispid, 1-3 

 feet high : leaves oblong-lanceolate, coarsely and irregularly sharply ser- 

 rate, 3-6 inches long, sessile and commonly somewhat conn ate -per foliate 

 at base: heads numerous, 6-8 lines broad, nodding after or during flower- 

 ing : rays 6-12, 3-8 lines long, or more : involucre depressed-hemispheric. 

 its outer bracts commonly ciliate, often large and foliaceous and ranch 

 exceeding the broad yellowish-margined membranaceous inner ones: 

 achenes flat, cuneiform, usually 4-awned the margins and awns retrorsely 

 barbed. In wet places, California to Brit. Colunbia and across the Con't. 



B. Beckii Torr. in Spreng. Neue Entdeck. ii, 135. Aquatic perennial; 

 submersed stems much elongated in deep water, simple or little branched : 

 submersed leaves sessile, 1-2 inches long, repeatedly divided into numer- 

 ous capillary segments ; emersed ones few, sessile, opposite or sometimes 

 in 3's, lanceolate or oblong, acute, serrate or laciriiate, 6-18 lines long : 

 heads solitary or few, short-peduncled : involucre hemispheric, its bracts 

 oval or oblong, obtusish, glabrous, the outer somewhat shorter than the 

 inner : rays 6-10, obovate or oblong, obtuse, golden yellow : achenes nearly 

 terete, truncate at both ends, half-inch long: pappus of 3-6 rigid persistent 

 aWns which are smooth below, the upper part downwardly barbed. In 

 p6nds and slow flowing streames, Canada to New Jersey and Missouri : re- 

 ji6rted from Green Lake King Co. Washington by Mr, C. V .Piper, perhaps 

 introduced. 



Subtribe v } Madiese PC. Bay-flowers ligulatc and fertile (rarely 



