268 SUMMER FLOWERS. 



attenuate, appressed. Wet meadows and pastures. Fl. 

 June. This plant is sometimes regarded as a variety of C. tube- 

 rosus. Luxuriant specimens, with more divided leaves, some- 

 times slightly decurrent, have been named C. Forsteri. 



(161) Silybum. MILK THISTLE. 



S. Marianus : annual or biennial ; stems 2-3 feet high, 

 slightly branched, nearly glabrous ; leaves smooth, shining 

 above and variegated by white veins, the lower ones deeply 

 pinnatifid with broad very prickly lobes, the upper ones clasp- 

 ing the stem by prickly auricles scarcely decurrent ; flower- 

 heads large, drooping, solitary at the ends of the branches, 

 with purple florets; involucral bracts, broad at the base, with 

 a stiff, spreading, leafy appendage, ending in a long prickle; 

 hairs of the pappus simple. Waste places. Fl. June, July. 



(162) Centaurea. 



* Involucral bracts not prickly. 



C. nigra : stems erect, hard, branched, 1-2 feet high ; leaves 

 linear-lanceolate or oblong, the upper ones entire or nearly 

 so, the lower with a few coarse teeth ; involucres globular, on 

 terminal peduncles, the bracts closely imbricate, so as only to 

 show their appendages, which are brown or black, and deeply 

 fringed, except on the innermost, where they are shining 

 and jagged ; florets purple, all equal or the outer row much 

 larger and neuter ; fruits crowned by a ring of very minute, 

 scaly bristles, occasionally intermixed with a few longer, very 

 deciduous ones. Knapweed. Meadows, pastures, and way- 

 sides. Fl. June to August. 



Var. Jacea : appendages of the involucral scales much paler, 

 with a much shorter fringe, or jagged. Sussex, rare. 



