COMPOSITE. 461 



Involucral bracts linear 3. Welted T. 



Involucres ovoid or cylindrical 4. Slender T. 



Pappus consisting of feathery hairs (Plume Thistles) . 

 Leaves decurrent along the stem , forming prickly wings. 

 Flower-heads all peduncled. 



Mower-heads few, near \\ inches long. Stem winged 



and prickly. Root biennial 5. Spear T. 



Flower-heads not an inch long, in terminal corymbs. 

 Leaves but little decurrrent. Rootstalk creep- 

 ing 7. Creeping T. 



Flower-heads small, in dense clusters. Stem winged 



and prickly 6. Marsh T. 



Leaves not decurrent^ or only very shortly so. 

 Flower-heads sessile or on very short peduncles. 

 Stems stout and branched (about 2 feet). Invo- 

 lucres large and cottony 8. Woolly T. 



Stems dwarf, or scarcely any. Involucres not 



cottony 12. Dwarf T. 



Flower-heads all peduncled. Eootstock perennial, 

 often creeping. 



Flower-heads in terminal corymbs 7. Creeping T. 



Flower-heads growing singly on long peduncles. 



Leaves ciliate, not prickly, very white underneath 9. Melancholy T. 

 Leaves prickly, green, or with a -loose white cotton 

 underneath. 

 Leaves deeply pinnatifid and lobed. Flower-heads 



usually 2 to 4 .10. Tuberous T* 



Leaves toothed, sinuate, or shortly lobed. 



Flower-heads usually solitary or 2 only . .11. Meadow T. 



Very anomalous specimens occur occasionally, especially among the 

 Plume T/iistles, which are generally believed to be natural hybrids. 



1. Milk Thistle. Carduus Marianus, Linn. (Fig. 550.) 

 (Eng. Bot. t. 976. Silyhum, Bab. Man.) 



An annual or biennial, 2 to 3 feet high, not much branched, and 

 glabrous or with but very little cottony wool. Leaves smooth and 

 shining above, and variegated by white veins ; the lower ones deeply 

 pinnatifid with broad very prickly lobes ; the upper ones clasping the 

 stem by prickly auricles but scarcely decurrent. Flower-heads large, 

 drooping, solitary at the ends of the branches, with purple florets. 

 Bracts of the involucre very broad at the base, with a stiff, spreading, 



