COMPOSITE. (COMPOSITE FAMILY.) 199 



63. MATBICABIA,! Tourn., L. 



Herbs, with finely once or thrice dissected leaves, and pedunculate heads, 

 the rays white (or wanting) and the disk-flowers yellow. 



1. M. discoidea, DC. Annual, somewhat aromatic, glabrous, a span to 

 a foot high, very leafy : leaves 2 to 3-pinnately dissected into short and narrow 

 linear lobes : heads all short-peduncled : bracts of the involucre broadly oval, 

 white-scarious with greenish centre, hardly half the length of the well-devel- 

 oped greenish-yellow ovoid disk : akenes oblong, somewhat angled, with an 

 obscure coroniform margin at summit, this occasionally produced into one or 

 two conspicuous oblique auricles of coriaceous texture. From W. California 

 to Montana and far northward ; becoming naturalized in the Atlantic States. 



64. TANACETUM, Tourn. TANSY. 



Strong-scented, alternate-leaved, yellow-flowered perennials. Ours are low, 

 with stems rather slender and naked above, bearing rather small (2 lines 

 broad) globular heads, and leaves simply or pedately 3 to 5-cleft. 



1 . T. Nuttallii, Torr. & Gray. Silvery-canescent, loosely cespitose, a span 

 high : leaves short, mostly broad-cuneate with tapering base, obtusely 3 to 5- 

 lobed at the broad summit ; those of the flowering stems usually oblong or 

 linear and entire : heads few, somewhat paniculate or loosely clustered, some of 

 them slender-pedunculate: involucre very scarious. JT1. ii. 415. Mountains 

 of N. Wyoming. 



2. T. capitatum, Torr. & Gray. Silvery-canescent, densely cespitose, a 

 span high : leaves simply or pedately 3 to 5-parted into linear lobes, or some 

 of them only 3-cleft at summit : flowering stems scapiform or 2 to 4-leaved : 

 heads 10 or more, sessile in a globose glomerule. Loc. cit. Mountains of 

 N. Wyoming. 



65. ARTEMISIA, Tourn., L. WORMWOOD. SAGE-BRUSH. 



Herbs and low shrubs, bitter-aromatic ; with alternate leaves and small 

 paniculate heads, commonly nodding ; the flowers yellow or whitish, usually 

 sprinkled with resinous globules. 



1. Heads heterogamous ; the dislc-flowers hermaphrodite bat sterile, their ovary 



abortive, and style mostly entire : receptacle not hairy. DRACUNCULUS. 

 * AJccnes and flowers beset with long cobwebby and crisped hairs : spinescent 



undershrub. 



1. A. spinescens, Eaton. Stout and densely branched, rigid, 4 to 18 

 inches high, villous-tomentose : leaves small, pedately 5-parted and the divis- 



1 The following species of the Old- World genus Chrysanthemum has become extensively 

 naturalized, its broad heads and conspicuous white raya making it very prominent. It 

 may be characterized as follows : 



C. Leucanthemum, L. Glabrous, a foot or two high, simple or sparingly branched : cau- 

 line leaves spatulate, and the upper gradually narrower, becoming small and linear, pinnately 

 dentate or incised, partly clasping at base ; radical broader, petioled : head broad and flat : 

 rays inch long : pappus none. Known as " Ox-eye Daisy " or " Whiteweed." Leucanthe- 

 mum vulgare, Lam. 



