108 COMPOSITE. 



Sandy fields and hills. June— Aug. Per. Stem 1 to 4 feet high, short, webby- 

 haired when young, hollow. Leaves somewhat clasping, woolly and hairy, armed 

 with stiff spines. ESmds large, axillary and terminal, with 20 to 30 narrow 

 bracts at base, tho outer of which haro 6pines somewhat in pairs. Flowers dull 

 yellow, rarely purple. 



8. C. ARVENSE, Scop. Canada Thistle. Cursed Thistle. 



Low, branched; roots extensively creeping; leaves oblong or lanceolate, smooth, 

 or slightly woolly beneath, sinuate-pinnatifid, prickly-margined; involucre round 

 or ovate, with minute spines ; scales close-pressed, ovate-lanceolate. 



Cultivated fields and pastures, naturalized. July, Aug. Per. Stem 3 feet high, 

 with a branching panicle at tbe top. Leaves alternate, thickly beset with spinet. 

 Heads small, numeroui, terminal. Flowers purple rarely whitish; the involucre 

 is nearly thornless, and is the only part that can be safely handled. A most trub- 

 lesome weed, which it is extremely difficult to eradicate. 



54. ONOPORDON, Vaill. Cotton Thistle. 



Heads discoid, homogamous. Involucre ovate-globose ; 

 scales coriaceous, tipped with a. lanceolate prickly appen- 

 dage. Receptacle deeply alveolate. Aciienia 4-augled, 

 transversely wrinkled. Pappus in several series ; bristles 

 numerous, slender not plumose, united at the base into a 

 hoary ring. — Coarse branching herbs, with decurrent leaves, 

 and large hsads of purple flowers. 



1. 0. ACANTHIUM, L, Cotton Thistle. Scotch Thistle.. 



Stem and leaves woolly ; leaves ovate-oblong, sinuate and spinous, decurrent ; 

 involucre scales linear-subulate, the outer spreading and woolly at the base. 



Waste grounds, in some places naturalized. Cultivated in Scotland as the 

 Scotch Thistle. July. Bienniel. A tall cottony plant 4 to 6 feet high, branched 

 and winged at the summit, wings very spinous. Involucre round, cottony, spinous^ 

 Flowers purple. 



55. LAPPA, Tourn, Burdock. 



Lat. lappa a burr, from Gr. labein, to lay hold of, a characteristic term. 



Heads many-flowered, the flowers all perfect and similar. 

 Involucre globose ; scales imbricated coriaceous and ap- 

 pressed at the base, with a long subulate hooked point. Re- 

 ceptacle bristly. Aciienia. oblong, flattened, wrinkled 

 transeversely. Pappus short, of numerous rough bristles, 

 not united at the base, deciduous. — Coarse biennial weeds, 

 with large alternate heart-shaped and petioled leaves,^ with wavy 

 margins, and middle-sized heads of purple (rarely whiie) flowers,, 

 solitary or in clusters. 



1. L. major, Gaert. Common Burdoclc. 



Upper \t aves ovate, lower very large, heart-shaped; involucre smooihish ; ittrfet » 

 •nbulate. 



Cultivated and waste ground!, common, introduced. July— Oct. Stem stout t ': 

 to 4 feet high. Root Itavet very large, (often 1 to 2 feet long and a foot wide) with 

 navy ©dge»v Tho scaU* of tho involucre *il terminate in a minute, firm ho**, . 



