MACLOSKIE : COMPOSITE. 82 1 



i. AMBROSIA SCABRA Hook. & Arn. 



Stem scabrid. Leaves pinnate, callous-scabrid on the upper surface, 

 hirsute-pubescent underneath ; segments linear-lanceolate, acute, the lower 

 incised-pinnatifid. Racemes solitary, sometimes becoming a leafy panicle. 



(Buenos Ayres, etc., in pastures) ; N. Paragon., by Rio Negro. 



2. A. TENUIFOLIA Spreng. 



Pilose ; lower leaves thrice-pinnatifid, with linear segments. Racemes 

 solitary, copiously paniculate. Male involucre with subentire orifice ; 

 female involucre hard, sparsely tubercled. 



Annual herb, 60-90 cm. high, copiously branching. (Argentina) ; N. 

 Paragon., by Rio Negro. 



35. XANTHIUM Linn. Cockle-bur. 



Rough, monoecious annuals, with small >&Aft& of greenish, discoid flowers, 

 the male-heads many-flowered, clustered at the ends of the branches, the 

 females axillary, with 2 apetalous flowers. Males involucrate by distinct 

 scales, the filaments united but anthers separate, the receptacle chaffy. 

 Female heads with closed involucre covered by hooked spines. Corolla 

 none. Pappus none. Species 5, widely distributed. (Fig. in Eng. & 

 Prantl, iv, 5, p. 223.) 



i. X. AMBROSIOIDES Hook. & Arn. 



Spinose, tomentose-hoary. Stem procumbent. Leaves bipinnatifid, 

 the segments oblong, obtuse, marginally revolute. Female head solitary, 

 its spines slender, setiform, patent, apically hooked ; the terminal spine 

 stout and straight. 



It has the foliage of Ambrosia with the fruit of Xanthium. A var. has 

 the female head with no stout spine. 



N. Patagon. in fields by Rio Negro. 



2. X. ITALICUM Moretti. (X. macrocarpum DC.) 



Leaves cordate, cuneate in the sinus, 3-lobed, toothed. Fruiting in- 

 volucre ovate-oblong, hispid between the spines and at the base of the 

 beaks, which are apically hooked. 

 N., Patagon., banks of Rio Negro. 



