COMPOSITAE. 361 



497. XANTHIUM. COCKLEBUR. 



Annual herbs; leaves alternate, petioled; heads monoecious, 

 in axillary or terminal clusters or short interrupted spikes, the 

 pistillate heads 2-flowered and below the several-flowered stami- 

 nate ones; involucre of the staminate heads of several distinct 

 narrow tegules; involucre of the pistillate heads bur-like, ovoid or 

 oblong, closed, indurated, 2-celled, 2-flowered, armed all over 

 with strongly hook- tipped spines; pappus none; corolla none; 

 akenes obovoid thick. 



Xanthium varians Greene. Stems simple or branched, 20-40 cm. high, 

 sparsely setose; leaves mostly ovate or rhombic-ovate, coarsely and doubly 

 serrate-dentate, scabrous on both surfaces; fruiting burs ovoid, 15-20 mm. 

 long, armed with about 70 spines half as long as the diameter of the body; 

 beaks stout, incurved at tip. 



Sandy banks of the Columbia River. 



498. GAERTNERIA. 



Herbs (in ours) with mostly alternate leaves ; sterile and fertile 

 heads separate or sometimes mixed in the inflorescence; fertile 

 involucre 1-4-celled, bur-like, armed with spines in more than 

 one row; pistils solitary in each cell of the involucre. 



Ours all seashore perennials. 



Leaves 2-3 times pinnately parted. G. bipinnatifida. 



Leaves cuneate-obovate, serrate or incised. G. chamissonis. 



Gaertneria bipinnatifida (Nutt.) Kuntze. Herbage canescently hirsute; 

 stems prostrate or procumbent, branched, 30-90 cm. long; leaves ovate in 

 outline, 3-5 cm. long, once or twice pinnatifid into oblong segments; staminate 

 heads in a dense raceme; fruiting involucre ovoid-fusiform, nearly glabrous, 

 armed with short subulate flattened spines. 



Common on high sandy or gravelly sea-beaches. 



Gaertneria chamissonis (Less.) Kuntze. Stems stout, prostrate or pro- 

 cumbent, 60-90 cm. long, hirsutely pubescent; leaves oblong to oval, cuneate 

 at base, obtusely serrate or the lower ones often incised, silvery-silky, petioled; 

 fruiting involucre 2-flowered, sparsely hirsute, armed with very short flat 

 spines. 



On the ocean coast, Vancouver Island to California. 



499. EUPATORIUM. 



Mostly perennial herbs; leaves whorled (in ours) mostly 

 resiniferous-atomiferous; heads discoid, in cymes or panicles, 

 rarely solitary; tegules few to numerous, receptacle naked; pappus 

 of numerous scabrous capillary bristles, mostly in 1 row. 



Eupatorium maculatum L. Perennial, stout, erect, 1-3 m. high, simple or 

 branched near the top; herbage pubescent; leaves in whorls of 3-6, ovate to 

 oblong-ovate, incisely toothed, thickish and somewhat rugose, 10-30 cm. long; 

 heads numerous in a rather flat-topped cyme; involucre cylindric; tegules 

 oblong, purplish, imbricated in 5 or 6 series, the outer shorter; flowers purple. 



Sumas, Washington, Gorman; British Columbia eastward to Newfoundland 

 and the Atlantic states. 



