180 COMPOSITE FAMILY. 



* * Pappus of naked, rough or short-barhed bristles, or none. 

 ■4- Filaments of the stamens united into a tube. Leaves white-variegated. 



3. SILYBUM. Scales of the involucre with the upper part leaf-like and spread- 



ing, spiny. Receptacle beset with bristles. Akenes flattened: pappus of 

 many rather short and rigid bristles minutely bearded on their edges. 



•♦-H- Filaments separate. 



4. ONOPORDON. Heads and flowers as in true Thistles, No. 2. Receptacle naked 



and honeycombed. Akenes 4-angled, wrinkled: pappus of many slender 

 bristles united at base into a horny ring. Stems strongly leaf-winged. 



5. LAPPA. Scales of the globular involucre abruptly tipped with a spreading 



slender awl-shaped appendage, mostly hooked at its point. Receptacle bristly. 

 Akenes flattened, wrinkled: pappus of many short and rough bristles, their 

 bases not united, deciduous. Leaves and stalks not prickly. 



6. CARTHAMUS. Outer scales of the involucre leaf-like and spreading, middle 



ones with ovate appendage fringed with spiny teeth or little spines, innermost 

 entire and sharp-pointed. Receptacle beset with linear chaff. Akenes very 

 smooth, 4-ribbed: pappus none. Leaves witli rigid or short spiny teeth. 

 r. CNICUS and 8. CE^iTAUREA; see next division. 



§ 2. Thistle-like or Scabious-like, with mnny-rnnked imbricated scales to the involucre, 

 many-flowers, and the two branches of the style united into one body almost or 

 quite to the tip, as in ^ I: but the outer flowers of the head different from the 

 rest and sterile, except in a few species of Centaurea. Receptacle beset with 

 bristles. 



7. CNICUS. Outer flowers smaller than the rest, slender-tubular, sterile. Scales 



of the involucre tipped with a long spine-like appendage which is spiny-fringed 

 down the sides. Akenes short-cylindrical, many-ribbed and grooved, crowned 

 with 10 short and horny teeth, within which is a pappus of 10 long and rigid 

 and 10 short naked bristles. Leaves prickly-toothed. 



8. CENTAUREA. Outer flowers sterile and with corolla larger than the rest, 



often funnel-shaped and with long sometimes irregular lobes, forming a kind 

 of false ray; but these are wanting in a few species. Involucre various, but 

 the scales commonly with fringed, sometimes with spiny tips. Akenes flat or 

 flattish : pappus of several or many bristles or narrow scales, or none. 



§ 3. Bur-like <»• achenium-like in the fruit, which is a completely closed involucre 

 containing only one or two flowers, consisting of a pistil only, with barely a 

 rudiment of corolla, therefore very different from most plants of the family ; 

 but the staminate flowers are several and in a flat or top-shaped involucre. 

 Heads therefore moncecious, or rarely dioecious: no pajij^us. Coarse and 

 homely weeds. 



9. XANTHIUM. Heads of staminate flowers in short racemes or spikes, their 



involucre of several scales in one row: fertile flowers below them, clustered 

 in the axils, two together in a 2-celled hooked-prickly bur. 



10. AMBROSIA. Heads of staminate flowers in racemes or spikes terminating the 



stem or branches, their involucre of several scales united in flattish or top- 

 shaped cup; fertile flowers clustered below the staminate, only one enclosed 

 in each small achenium-like involucre, which is naked, or with a few tubercles 

 or strong points near the top in a single row. 



§ 4. Plants not thistle-like nor bur-like. 



* Two kinds of flowers in the same head, the outer ones with pistils only. 



■t- Pappus none or a minute border or cup : no chaff among the flowers : scales of the 

 involucre dry, often with scarious margins, imbricated. Bitter-aromatic or 

 rather acrid plants. 



11. TANACETUM. Heads of many yellow flowers ; the marginal ones with pistil 



only and a 3-5-toothed corolla. Akenes angled or ribbed, with a flat top, 

 crowned with a cup-like toothed or lobed pappus. Very strong-scented 

 herbs, with heads in a corymb. 



12. ARTEMISIA. Heads small, of few or many yellow or dull purplish flowers, 



some of the marginal ones pistillate and fertile, the others perfect, but some- 

 times not maturing the ovary. Akenes obovate or club-shaped, small at the 

 top, destitute of pappus. Bitter-aromatic, and strong-sceuted plauts, with 

 heads in panicles. 



