292 COMPOSITE. 



31. Stylocline. Fertile flowers 5 to 10 or numerous, in two or more series on a cylindrical or 



columnar receptacle ; their chati' thin, saccate or boat-shaped. Pappus of a few cadu- 

 cous bristles to the sterile flowers, or none. 



-i- -}- Chaff more open, subtending or hardly enclosing the fertile flowers or their akenes, these in 

 more than one series : central flowers sometimes fertile. 



32. Evax HESPEREVAX. Receptacle villous, its centre elongated into a narrow column. 



Akenes pear-shaped, flattish parallel to the subtending scale : pappus none. 



33. Filago. Receptacle obconical or cylindraceous with a flat summit. Akenes oblong, nearly 



terete : pappus of numerous bristles to the perfect or sterile flowers, fewer or none to the 

 outer fertile flowers. 



Subtribe III. GNAPHALIE^E. Scales of the involucre all thin and scarious, often pearly, 

 persistent. Receptacle naked. Floccose-woolly herbs. Flowers in all the American gen- 

 era with capillary pappus, nearly in a single series ; the pistillate ones with filiform or 

 very slender corollas. 



34. Antennaria. Heads completely dioecious ; the staminate with undivided style and bristles 



of the pappus thickened or barbellate at the apex ; pistillate with slender bristles of the 

 pappus united at base into a ring. Low caispitose herbs. 



35. Anaphalis. Heads incompletely dioecious ; i. e. the staminate ones with a few hermaphro- 



dite but sterile flowers in the centre. Style commonly 2-cleft at the apex. Bristles of 

 the pappus all separate, those of the sterile flowers little thickened upward. Taller 

 herbs. 



36. Gnaphalium. Heads all heterogamous, with pistillate flowers very numerous in more than 



one series, and hermaphrodite fertile ones fewer in the centre. Bristles of pappus slen- 

 der, not thickened upward. 



TRIBE V. HELIANTHOIDE M. Heads heterogamous with ligulate ray-corollas, or discoid 

 and homogamous (or rarely heterogamous) ; the perfect or staminate flowers with tubular 

 regularly 4 - 5-lobed corollas. Receptacle chaffy (except sometimes among the disk-flow- 

 ers especially when sterile). Anthers often sagittate at base, but without tails. Branches 

 of the style in perfect flowers either truncate or tipped with an appendage. Pappus of 

 2 to 4 chaffy scales, awns, teeth, &c. , or a cup or crown, never of capillary bristles. Leaves 

 mostly opposite, at least the lower ones. Corollas most commonly yellow. 



Subtribe I. AMBROSIE^E. Heads small and discoid : only the pistillate flowers fertile ; these 

 few and with no corolla, or a rudimentary one in the form of a short tube surrounding the 

 base of the style. Hermaphrodite-sterile or staminate flowers with campanulate limb to 

 the corolla ; anthers slightly cohering or nearly distinct, their inflexed tips often mucro- 

 nate or cuspidate ; the abortive style entire, with truncate apex tipped with a minute radi- 

 ate tuft or brush. Pappus none. Akenes in our genera obovate and thick. 



* Heads heterogamous, a few fertile flowers at the margin. 



37. Oxytenia. Fertile flowers apetalous : akenes long-villous, crowned with a protuberant 



epigynous disk. Leaves pinnately divided, or the upper entire. 



38. Iva. Fertile flowers with short tubular corolla : akenes naked. Leaves simple. 



* * Heads homogamous, unisexual, monoecious ; the fertile with 1 to 4 pistillate apetalous flowers 

 in a closed and bur-like or akene-like pointed involucre ; sterile with rather numerous 

 flowers in an open 



+- 5-12-lobed or almost truncate invohicre. 



39. Hymenoclea. Fertile involucre one-flowered, appendaged with 9 to 12 scarious spreading 



scales. Stem shrubby. 



40. Ambrosia. Fertile involucre one-flowered, akene-like, bearing no more than a single row 



of tubercles or short spines. Herbs. 



41. Franseria. Fertile involucre 1 - 4-flowered, 1 - 4-celled, armed with more than one row of 



tubercles or prickles. 



+- +- Involucre to sterile heads of a few distinct scales. 



42. Xanthium. Fertile involucre oblong, bur-like, 2-flowered, 2-celled, beset with numerous 



hooked prickles. 



Subtribe II. VERBESINE^E. Heads radiate, the rays either neutral or pistillate, or else ray- 

 less ; the disk-flowers perfect and fertile, each subtended by a chaff of the receptacle. 

 Akenes thick and 3 - 4-angular ; or those of the disk laterally compressed (i. e. contrary 

 to the subtending chaff), never obcompressed (i. e. flattened parallel with the chaff). 

 Pappus none, or a cup or crown, or of 2 to 4 rigid awns or chaffy scales from the angles, 

 with or without some intermediate small scales. 



