GJ5RTNRRIA COMPOSITE 337 



XANTHIUM 



Nutt. Stems 1-3 feet high, from an annual or biennial root, diffusely 

 branched from the base, hirsute-pubescent or hispid, sometimes canescent 

 with strigose-sericeous pubescence when young: leaves of ova'e or round- 

 ish outline, 1-3 inches broad bipinnatifid or the upper oblong and only 

 pinna' ifid: staminate racemes solitary or paniculate: pistillate involucres 

 armed with flat and thin lanceolate-subulate smoo h and glabrous long 

 and straight spines, 3-4 lines long, commonlv 1-flowered. On sandy plains 

 and river-banks, Brit. Columbia to California and Nevada. 



0. bipinnatifida O. Ktz. Rev. Gen. i, 339. Franseria bipinnatifida Nutt. 

 Herbaceous perennial with stout procumbent stems 2-3 feet long, some- 

 what hirsute : leaves ovate in outline, 1-2 inches long, 2-3-pinnately parted 

 into oblong-linear divisions and sma'l oblong lobes, canescent with soft 

 tomentum or fine hirsute-sericeous pubes ence : staminate heads rather 

 large, in dense spikes or ra3emes: pistillate heads ovate-fusiform, armed 

 wi'h rather short and thick but flattish tubercle-like spines, their acute 

 tips sometimes incurving. On sandy beaches along the coast, Brit. Colum- 

 bia to California. 



G. Chamissonis O. Ktz. 1. c. Franseria Chamissonis Less. Stems pro- 

 cumbent, 2-3 feet long, from a perennial root : leaves cuneate-obovate or 

 oblong-ovate with a cuneate base, 3-5-nerved at base, obtusely serrate, the 

 lower often Jaciniate-incised : staminate spikes or racemes dense, of rather 

 large heads ; pistillate heads ovate, armed with rather short and tMck but 

 flattish canalicu'ate tubercule-like spines. Sandy sea- beaches, Brit- Co- 

 lumb a to California. Not common. 



* * Involucre of the staminate heads of few distinct bracts R0- 

 ceqtacle cy'indraceous. 



XANTHIUM Tourn. L. Gen. n. 1056- (COCKLE-BUR) 



Coarse annuals with branching stems, alternate and usually 

 lobed or toothed leaves, and mostly clustered heads of greenish 

 or yellowish flowers, in terminal or larger axillary clusters of 

 both sexes, the staminate uppermost. Involucre of the globu- 

 lar sterile heads 1-2 series of small narrow bracts. Receptacle 

 distinctly paleaceous, a cuneate or linear-spatulate chaffy bract 

 partly enclosing each sterile flower. Filaments monadelphous. 

 Anthers distinct but connivent, the inflexed apical appendage 

 mucronate. Sterile style unappendaged. Fertile head a closed 

 and ovoid bur-like 2-celled and 2-flowered involucre, 1-2-beak- 

 ed at the apex, the surface clothed with uncinate-tipped prickles : 

 each flower a single pistil, maturing a thick ovoid achene, the 

 two permanently enclosed in the indurated prickly involucre. 



* Leaves cordate or ovate, 3-ribbed from the base, with dentate 

 margins, and often incised or lobed, on long petioles : axiles unarmed : 

 fruiting involucre with 2 prominent beaks. 



X. STRUMARIUM L. Sp. 987. Rough : stems 1-6 feet high : leaves slender- 

 petioled, broadly ovate to orbicular, 3-ribbed and moie or less cordate at 

 base, the lower often 10 inches broad, irregularly dentate and more or 

 less 2-5-lobed: fruitiug involucre 6-9 lines long, glabrous or pubernlent; 

 the beaks straight and rarely at all hooked at maturity. In waste places. 

 Naturalized from Europe. 



X. Canadense Mill. Diet. ed. 8, No 2. Stems stout, 1-2 feet high, often 

 punctate with bro*n spots : leaves ample, broadly ovate, coarsely and irreg- 



