180 COMPOSITE FAMILY. 



* * Pappus of naked, rouoh or short-barbed bristles, or none. 

 - Filaments of the stamens united into a tube. Leaves while-variegated, 



8. 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. 



-t-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. 



6. LAITA. Scales of the globular involucre abruptly tipped with a spreading 



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

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

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



C. GARTH AM US. 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 with rigid or short spiny teeth. 



1. CNICUS and 8. CENTAUREA; see next division. 



2. Thistle-like or Scabious-like, with many-ranked imbricated fcnles to the involucre, 

 many-flowers, and the tivn branches of the stifle united info one body almost or 

 quite to the tip, as in 1 : but (he outer flowers of the head different from the 

 rest and sttrile, 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 tee'h, 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 w achenium-like in (he fruit, which is a completely closed involucre 

 containing only one or two Jlotce'rs, consist inti of a pistil only, with barely a 

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

 biit the staminate jtotoert are several and in a, flat or top-slia'pe.d involucre, 

 heads therefore monoecious, or rarely dioecious: no pappus. 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-ccllcd 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 Onstlf-like nor bur-like. 

 * Two kinds of flowers in (he tame head, (he outer ones with pistils only. 



-- Pappus none or a minute border or cup : no choff among the floirers : scales of the 

 involucre dry, often with scarious maryins, imbricated. /Utter-aromatic or 

 ratiier acrid i>l<u 



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



only and a 3-6-toothed corolla* Akenes angled or ribbed, with a Hat 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, 



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

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

 top, destitute cfjappus. Hitter-aromatic, and strong-scented plants, with 

 heads in panicles. 



