COMPOSITE FAMILY. 227 



|| || Flowers whitish. 

 30. PARTHENIUM. Heads small, many-flowered ; the rays 5, usually inconspicuous, 



with very short and broad obcordate limbs not projecting beyond the woolly disk. 



Involucre hemispherical, with two rows of short or roundish scales. Akenes ob- 



com pressed, with a slender callous margin, crowned with the persisting ray corolla 



and the pappus of two small chaffy scales. 

 = = Disk flowers perfect and fertile, those of the ray pistillate and fertile, or neutral. 



(Centaurea may be sought here; see p. 222.) 

 || Akenes flattened parallel with the scales of the involucre and chaff of the receptacle, 



or in 44 sometimes very slender. Leaves generally opposite ; involucre double, 



the outer mostly leafy like, the inner of erect scales. 



42. DAHLIA. Eay in the natural flowers neutral or in the common species more or less 



pistillate, but in the gardens most or all of the flowers are changed into rays. Inner 

 involucre of numerous more or less united scales. Akenes oblong, obscurely 2- 

 horned or notched at the apex. 



43. COREOPSIS. Rays usually 8, neutral, mostly yellow, or brown-purple at base. In- 



volucre commonly of about 8 outer loose or leaf-like scales and as many erect inner 

 ones. Chaff slender, deciduous with the flat akenes, which have mostly a pappus 

 of 2 teeth or awns, the latter not barbed downwards. 



44. BIDENS. Like Coreopsis, but several without rays, and some with slender or needle- 



shaped akenes ; all bear 2 or more rigid persistent awns, which are barbed down- 

 wards. 



45. COSMOS. Differs from Bidens in having the akenes distinctly beaked, and the rays 



(in ours) purple or rose-color. 



|| || Akenes flattened laterally (if at all), i.e., contrary to the scales of the involucre and 

 the chaff of the receptacle, the latter usually embracing or folded round their 

 outer margin. 



o JRays deciduous after flowering, usually yellow ; native. 

 x Receptacle flat or convex. 



89. HELIANTIIUS. Rays several or many, neutral. Scales of the involucre imbricated. 

 Receptacle flat or convex. Akenes flattish, but more or less 4-angled or lenticular, 

 marginless ; pappus of 2 thin chaffy scales corresponding with the outer and inner 

 angle of the akene, and sometimes with minute intermediate ones, all deciduous 

 from the ripe fruit. (Lessons, Fig. 381.) Leaves simple, entire or serrate ; stems 

 not winged. 



40. VERBESINA. Rays few (in ours 1-5), pistillate. Involucre of few erect scales. Re- 

 ceptacle rather flat. Akenes flat, winged or wingless ; pappus of 2 persistent awns. 

 Leaves simple, decurrent into wings on the stem. 



.41. ACTINOMERIS. Rays neutral, few or several. Involucre of several nearly equal 

 scales. Receptacle convex or conical. Akenes flat, oval, wing-margined ; pappus 

 of 2 persistent smooth awns. Leaves simple, serrate, often decurrent into wings on 

 the stem. x x Receptacle Mgh and co i umna r. 



38. LEPACHYS. Like Rudbeckia (next page), but akenes flattened, wing-margined on the 

 inner and sometimes on the outer edge, 1-2-toothed at summit. Disk grayish. Chalf 

 short and truncate. Leaves alternate, pinnately compound. 



o o Rays persistent on the fruit, becoming dry and papery, broad, pistillate and 

 fertile, of various colors ; exotic. 



34. ZINNIA. Rays several. Receptacle conical ; the oblong chaff not longer than the 

 velvety-tipped disk corollas. Akenes oblong or linear, flattened, or those of the ray 

 3-sided ; pappus of a chaffy awn or tooth on each angle, or sometimes hardly any. 

 Leaves opposite, sessile, and entire. Heads solitary, terminating the stem or 

 branches. j j j Akenes no f flattened, but angled or cornered. 



(50, 51) ANTHEMIS and ACHILLEA, to which the receptacle is sometimes chaffy, may be 

 sought here (p. 226), 



