188 COMPOSITE. 



nately parted into oblong-linear divisions and small oblong lobes, canescent 

 with a silky pubescence: sterile raceme dense, the heads large: fruit 

 ovate-fusiform, armed with short thick flattish spines, their tips often 

 incurving. — Sandy beaches; very common. June — Dec. 



3. A. Chamissonis (Less.). Size, habit etc., of the last, but leaves 

 cuneate-obovate, or oblong-ovate with cuneate base, obtusely serrate, only 

 some of the lower laciniate -incised: fruiting involucre ovate, the spines 

 broad and channeled. Habitat of the preceding, but less common. 



30. XANTHIUM, Tourn. (Cookxe-buk). Coarse annuals, with branch- 

 ing stems, alternate lobed or toothed leaves, and clustered heads of 

 greenish flowers; the staminate cjusters uppermost, the pistillate in the 

 leaf-axils. Involucre of staminate heads 1 or 2 series of narrow bracts. 

 Stamens monadelphous but anthers merely connivent. Fertile head a 

 closed ovoid bur-like 2-celled and 2-nowered involucre, 1 — 2-beaked at 

 apex: each flower a single pistil, becoming a thick ovoid achene, the two 

 enclosed in the hardened prickly involucre. 



1. X. spinosum, L. Widely branching from the base, 2 ft. high: 

 leaves ovate-lanceolate, more or less lobed or pinnatifid, glabrate and green 

 above, white-tomenlose beneath: burs % in. long, armed with short weak 

 prickles. — By waysides, common; native of tropical America. 



2. X. Canadense, Mill. Stout, branching above only : leaves broad- 

 oruid, slightly lobed, scabrous: bur an inch long, densely beset with 

 stoutish prickles, and at apex strongly 2-horned. — In low fields, where 

 it may have been introduced. Aug. — Oct. 



Suborder 5. Hblianthace^:. 



Plants commonly with balsamic-resinous juice, and coarse roughish or 

 woolly foliage. Rays conspicuous; receptacle strongly chaffy; anthers 

 not caudate; involucre not scarious; pappus never of capillary bristles. 



Involucre of 1 or 2 series of similar bracts; rays small, 



white Eoliptioa 31 



Involucral bractB imbricated in several series; 



Pappus none; achenes oblong Balsamorrhiza 32 



" of more or less united awns or palese Wyethia 33 



'' of two or more thin caducous palese Helianthus 34 



" none; achenes obovoid, compressed Heliantheixa 35 



Involucre double; outer series of bracts spreading, inner erect; 



Pappus not retrorsely barbed '. Leptostne 36 



" retrorsely barbed or aculeolate Bidens 37 



31. ECLIPTICA, Rumphius. Flaccid low riparian herbs with oppo- 

 site leaves, and scattered small heads of whitish flowers. Involucre 

 broad, of 1 or 2 series of herbaceous bracts. Bracts of flattish receptacle 

 reduced to awn-shaped chaff or bristles. Bays short, fertile. Achenes 

 thick, those of the ray triquetrous, of the disk compressed, margined. 

 Pappus of 2 — 4 short teeth or awns or none. 



