182 COMPOSITE. (COMPOSITE FAMILY.) 



30. XANTHIUM, Tourn. COCKLE-BUR. CLOT-BUR. 



Coarse annuals : with branching stems, alternate and usually lobed or 

 toothed leaves, and mostly clustered heads, botli sexes in terminal and larger 

 axillary clusters, the male uppermost ; the lower axillary clusters of few or 

 solitary female heads. 



1. X. Canadense, Mill. Stem often punctate with brown spots: leaves 

 cordate or ovate, 3-ribbed from the base, with dentate margins and often in- 

 cised or lobed, on long petioles : fruiting involucre about an inch long, densely 

 beset with rather long prickles, the two stout beaks at maturity usually hooked 

 or incurved, the surface and base of the prickles more or less hispid. 

 X. strumarium, var. Canadense, Torr. & Gray. From Texas to the Saskatche- 

 wan and westward. 



31. ZI1TNIA, L. 



With opposite and mostly entire sessile leaves, single heads terminating the 

 branches, and showy flowers. In ours the leaves are narrow and rigid, connate- 

 sessile and crowded, and the nkenes 2 to 4-aristate. 



1. Z. grandiflora, Nutt. Scabrous: stems or branches a span or more 

 high from a stout woody base : leaves linear, 3-nerved at base : involucre nar- 

 row, 4 lines long : ligules 4 or 5, at maturity 5 to 8 lines long, dilated-obovate 

 or roundish, light yellow or sulphur-color, becoming white. Plains and bluffs, 

 E. Colorado to Texas and Arizona. 



32. HELIOPSIS, Pers. 



With loosely branching stems, veiny and mostly serrate 3-ribbed leaves on 

 naked petioles, and pedunculate showy heads with numerous yellow rays. 



1. H. lajvis, Pers. Smooth and glabrous or nearly so throughout, 3 or 4 

 feet high : leaves bright green, thinnish, oblong-ovate or ovate-lanceolate from 

 a truncate or slightly cuneate-decurrent base, acuminate, coarsely and sharply 

 serrate with numerous teeth, 3 to 5 inches long : heads somewhat corymbose : 

 rays broadly linear, an inch long : akenes wholly glabrous and smooth. 

 Near Canon City, Colorado, Brandegee ; chiefly a form of the Atlantic States. 



33. ECHINACEA, Moanch. 



Perennial herbs, with rather stout erect stems, undivided leaves, the lower 

 long-petioled, and solitary large heads on long peduncles terminating the stem 

 and few branches. Rays from flesh-color to rose-purple, much elongating 

 with age. 



1. E. angustifolia, DC. Hispid, a foot 01 two high, mostly simple: 

 leaves from broadly lanceolate to nearly linear, entire, 3-nerved, all attenuate 

 at base, the lower into slender petioles : bracts of the involucre in only about 

 2 series. Within the eastern limit of our range and extending eastward. 



34. RUDBECKIA, L. CONEFLOWER. 



With alternate leaves, either simple or compound, and showy pedunculate 

 heads terminating stem and branches : rays yellow, even sometimes wanting, 

 the lisk from fuscous to purplish black. 



