634 CONTRIBUTIONS FEOM THE NATIONAL HERBARIUM. 



5. Iva dealbata A. Gray, PI. Wright. 1: 104. 1852. 



Type locality: "In a mountain valley, between the Limpia and the Rio Grande," 

 western Texas. 



Range: Western Texas and southern New Mexico. 



New Mexico: Kingston; Lake Valley; near White Water; north of Parkers Well; 

 White Mountains; Lakewood; Carlsbad; Artesia; Carrizozo. Lower and Upper Sono- 

 ran zones. 



3. HYMENOCLEA Torr. & Gray. 



Much branched slender shrub, 1 to 2 meters high, with alternate lineai'-filiform 

 leaves, the lower irregularly pinnately parted; heads small, unisexual, very numer- 

 ous; involucre of staminate flowers saucer-shaped, 4 to 6-lobed; bracts of the recep- 

 tacle subtending the outer flowers obovate or spatulate; involucre of the solitary 

 fertile flower ovoid or fusiform, beaked at the apex, furnished below with 9 to 12 

 dilated scarious transverse wings. 



1. Hymenoclea monogyra Torr. & Gray, Mem. Amer. Acad. n. ser. 4: 79. 1849. 



Type locality: Valley of the Gila, New Mexico. 



Range: Western Texas to southern California and adjacent Mexico. 



New Mexico: Burro Mountains; Socorro; Deming; Rincon; Rio Alamosa; Dona 

 Ana Mountains; mesa west of Organ Mountains; Van Pattens. Along arroyos, in the 

 Lower Sonoran Zone. 



4. XANTHIUM L. Cocklebur. 



Coarse annuals with branched stems and alternate toothed or lobed leaves; sterile 

 and fertile flowers in different heads, the latter clustered below the short spikes or 

 racemes of the staminate ones; fertile involucre coriaceous, ellipsoid or ovoid, cov- 

 ered with hooked prickles so as to form a bur, 2-celled; achenes oblong, flat. 



KEY TO THE SPECIES. 



Leaves attenuate to both ends, short-petiolate, armed with triple 



spines in the axils 1 . X. spinosum. 



Leaves cordate-ovate, long-petiolate, unarmed. 



Fruit densely covered with spines, the body 5 to 10 mm. in 



diameter 2. X. commune. 



Fruit with few spines, the body 5 mm. in diameter or less 2a. X. commune 



vooton i. 



1. Xanthium spinosum L. Sp. PI. 987. 1753. 

 Type locality: "Habitat in Lusitania." 



Range: Waste ground in many parts of the United States; native of tropical 

 America. 



New Mexico: Pecos; Silver City; Santa Rita; Las Vegas. 



A noxious weed, in appearance very unlike the common cocklebur. 



2. Xanthium. commune Britton, Man. 912. 1901. 

 Type locality: Westport, New York. 



Range: New York and Quebec to Utah and Arizona. 



New Mexico: Shiprock; Carrizo Mountains; Tunitcha Mountains; Nara Visa; 

 Zuni; Pecos; Las Vegas; Dog Spring; Mesilla Valley. Waste ground and cultivated 

 fields. 



A very common and troublesome weed in cultivated fields in many parts of the 

 State. Probably it has been introduced into New Mexico, but in some localities it 

 seems to be at home. 



