332 COMPOSITE ADENOCAULON 



DIMERESIA 



glabrous, 4-sided. Roadsides and wast places : introduced from Europe. 



Subtribe iv Adenocaule Gray Syn. Fl i, pi. 2 y 59. 

 Heads he^er ogamous, discoid; both pistillate and hermaphro- 

 dite flowers with tubular more or less ampliale 4-5-toothed 

 or -lobed corolla: involucre nol scarious: receptacle naked: 

 achenes elongated, sir iale or nerved: pappus none. 



33 ADENOCAULON Hook. Bot. Mise. i, 119, t. 15. 



Perennial herbs with slender stems alternate and dilated leaves 

 on long margined petioles, and very small heads of whitish flow- 

 ers. Heads several to many-flowered ; the marginal ones pistil- 

 late only; the more numerous central ones hermaphrodite-sterile. 

 Involucre of few thin herbaceous bracts. Receptacle flat, naked. 

 Corollas all somewhat alike ; of the sterile flowers broadly fun- 

 nelform and deeply 4-5 -cleft; of the fertile ones less ampliate, 

 either regularly 4-lobed. or bilabiate with the outer lip 3-lobed. 

 Style of the sterile flowers undivided ; of the fertile ones with 

 short and broad stigmatic branches. Anthers sagittate, the au- 

 ricles minutely but evidently caudate, connate. Achenes obovate- 

 oblong or clavate, very obtuse, very much exceeding the involu- 

 cre, the upper part beset with stout stipitate glands! 



A. bicolor Hook. 1. c. Stems 1-3 feet high, leafy below: leaves dilated- 

 cordate, 1-3 inches long by nearly as broad, coarsely sinuate-dentate or 

 repand or slightly lobed, early glabrate and green above, white with thin 

 cottony wool beneath : bracts of the involucre 4-5, in a single series, ovate, 

 reflexed in fruit : fertile corollas regularly 4-lobed : achenes club-shaped, 2-3 

 lines long. Common in forests and woods, Alaska to California and east 

 to Lake Superior. 



Subtribe v. Dimeresese. Heads homogamous, flowers all herma- 

 qhrodite and fertile. Corollas tubular and regular, 5-toothed. 



34 DIMERESIA Gray Syn. Fl. i, pt. 2, Supp. 448. 



Low annuals with opposite leaves and 2-flowered heads in 

 dense terminal glomerules. Heads discoid, homogamous, the 

 flowers hermaphrodite and fertile. Involucre of 2 herbaceous 

 oblong concave bracts, a little united at base, each subtending 

 and almost enclosing a flower. Corolla tubular, regular, 5-tooth- 

 ed. Anthers sagittate at base, the narrow auricles but little ex- 

 tended. Style-branches narrowly linear, obtuse, not appendaged, 

 the bordering stigmatic lines extending to and around the naked 

 apex. Achenes clavate-pyriform, glabrous, many-striate, with 

 small epigynous areola, bearing a pappus of stout plumose bristles 

 in a single series which are united at base in a ring and early 

 deciduous together. 



^ D. Howellii Gray 1. c. 449. Stems stoutish, minutely floccose-woolly, 

 simple or branched, 6-18 lines long, from a long annual taproot : leaves ob- 

 ovate or oval, including the broad petiole 10-14 lines long, thiuly white- 

 woolly beneath, soon glabrate and green above: heads numerous, subses- 

 sile, in dense terminal glomerules : corollas purplish or flesh-color : pappus 



