COMPOUND FLOWERS 



165 



to be met with in gardens, and are occasionally to be found as 

 escapes. — Fl. July, August ; and, in turnip fields, again in October 

 and November. Annual or ISicnnial. 



4. C. aspera (Jersey Centaurea). — Stems much branched and 

 prostrate ; leaves narrow ; [lower-heads solitary ; the florets purple, 

 and each of the outer bracts of the involucre with 3-5 prickles. 

 Channel Islands. — Biennial. 



5. C. calcitrapa (Common Star-Thistle). — Scales of the involucre 

 ending each in a long stiff thorn. Well marked by its purplish 

 flowers, which are armed below with spreading thorns, and resemble 

 in figure the cruel iron instrument, named a caltrops, which was 

 used in war to lame horses, being thrown on the ground when it 

 was expected that cavalry would pass. The instrument is so con- 

 structed that, in whatever position it lies, one point sticks upwards. 

 Gravelly and sandy places in the south of England ; rare. — Fl. July, 

 August. Annual. 



6. C. solstitialis (Yellow Star-Thistle). — Stems 1-2 feet high, 

 winged ; leaves hoary ; flower-heads solitary, terminal, furnished 

 with spines ; florets yellow. Occasionally in cornfields, etc. — 

 Fl. July, September. Annual. 



III. TuBiFLOR^. — Tansy Group 



22. BiDENS {Bur-Marigold) 



1. B. cernua (Nodding Bur-Marigold). — Heads of flowers droop- 

 ing ; leaves serrated, undivided ; bristles of the fruit 3-4. A some- 

 what succulent jilant, 1-2 feet high, with narrow, serrated, smooth 

 leaves, and button-like, drooping heads of brownish yellow flowers, 

 at the base of which are several leafy bracts. 

 The fruit is oblong, and terminates in several 

 stiff bristles, each of which is thickly set 

 with minute points, which are turned back 

 like the barbs of an arrow, so as to take a 

 firm hold on the coat of any animal which 

 comes in contact with them. Watery places ; 

 frequent. — Fl. July to September. Annual. 



2. B. tripartita (Trifid Bur - Marigold) .— 

 Heads of flowers nearly erect ; leaves 3-parted. 

 Distinguished from the last by its somewhat 

 smaller heads of flowers, which frequently 

 have ray florets {B. cernua being usually 

 without), 3-parted leaves, and by having 3-5 

 bristles on the fruit. Watery places ; com- bidens Tripartita 

 mon. — Fl. July to September. Annual. {Trifid Bur-marigold) 



