1240 CAKDUACEAE 



1. Melampodium cinereum DC. Stems tufted, 1-3 dm. tall, closely gray-pubes- 

 cent or strigose, simple or sparingly branched. Leaf-blades linear-spatulate to linear, 2- 

 10 cm. long, entire, sessile : peduncles slender, 2-12 cm. long : heads rather showy : invo- 

 lucres campanulate or saucer-shaped, pubescent : outer bracts ovate, 5-6 mm. long, acute, 

 united to the middle : ray-flowers 7-9 ; ligules oval to cuneate-oblong, 8-10 mm. long : 

 disk-corollas 4-5 mm. long, their bractlets fringed at the apex : mature bracts of the inner 

 series of the involucre 2 mm. long, tuberculate-wrinkled, each surmounted by a cup-like 

 hood. 



In dry soil, Kansas to Arkansas, Texas and Arizona. 



2. Melampodium ramosissimum DC. Stems 1-3 dm. tall, tufted, loosely pubes- 

 cent or somewhat hirsute, diffusely branched : leaf -blades oblong to linear, 2-7 cm. long, 

 pinnatifid : outer bracts of the involucre ovate, 4-4.5 mm. long, acutish, united to below 

 the middle : ray-flowers 8-11 ; ligules white, oblong to cuneate-oblong, about 5 mm. long : 

 disk-corollas about 2 mm. long, their spatulate bracts erose at the apex : mature bracts of 

 the inner series of the involucre cornucopia-like, 2 mm. long, tuberculate, each sur- 

 mounted by a fringed hood. 



In dry soil, southern Texas. 



70. ACANTHOSPERMUM Schrank. 



Annual rather coarse herbs, with pubescent foliage and erect or creeping stems. 

 Leaves opposite : blades broad, often leathery, toothed. Heads radiate but inconspicuous, 

 axillary to leaf -like bracts. Involucre double, an outer one of five flat herbaceous bracts, 

 and an inner one of several smaller bracts which become bur-like and fall away enclosing 

 an achene at maturity. Receptacle concave or convex. Ray -flowers few, in one series : 

 ligules very small, yellowish, concave or hooded. Disk-flowers perfect but not producing 

 fruit. Anthers entire at the base. Achenes broadest above the middle, slightly curved. 

 Pappus wanting. The plants flower from spring to fall or throughout the year in the 

 extreme South. 



Petioles broadly winged or leaf -blades sessile by cuneate bases : involucral bracts with 2 large spines in 



addition to the prickles. 1. A. humile. 



Petioles not broadly winged : involucral bracts uniformly prickly. 2. A. australe. 



1. Acanthospermum humile (Sw.) DC. Stems erect or ascending, several dm. 

 tall. Leaf-blades deltoid-ovate to fiddle-shaped, 1-3 cm. long, obtuse, crenate-dentate : 

 heads short-ped uncled or nearly sessile : involucres campanulate ; bracts oblong to oblong- 

 spatulate, obtuse, ciliate, with 2 large spines above, in addition to the prickles : disk-flow- 

 ers with corollas about 1 mm. long, glabrous : mature inner bracts of the involucre hard, 

 cuneate, truncate, with hooked prickles and 1-2 stout spines at the top. 



In sand, Florida and about sea-port towns further north. 



2. Acanthospermum australe (L.) Kuntze. Stems branching at the base ; branches 

 prostrate or creeping, 1-6 dm. long: leaf -blades ovate, oval or rhombic, 1-2.5 cm. long, 

 acute, serrate-dentate above the middle, cuneate at the base : peduncles shorter than the 

 subtending bracts : involucres campanulate : bracts broadly ovate, obtuse, 2-3 mm. long, 

 uniformly prickly : disk -flowers with corollas 2 mm. long, puberulent : mature inner bracts 

 of the involucre forming a starfish-like fruit, each lobe 8-10 mm. long, densely beset with 

 uniform blunt weak prickles. [A. xanthioides DC.] 



In waste places and dry soil, North Carolina to Florida and Louisiana. 



71. SILFHIUM L. 



Perennial usually large caulescent herbs, the sap often resinous. Leaves alternate : 

 blades entire, toothed or 1-2-pinnately parted, sometimes connate-perfoliate. Heads 

 radiate, showy. Involucres campanulate or hemispheric, many-flowered : bracts broad, in 

 few series. Receptacle flat or nearly so, with numerous bractlets subtending the disk- 

 flowers. Ray-flowers pistillate, in 2-3 series, fruit-producing : ligules yellow or rarely 

 white. Anthers usually 2-toothed or entire at the base. Achenes flat and broad, 2-winged, 

 often notched at the apex. Pappus wanting, or of 2 small awns confluent with the wings 

 of the achene. ROSIN-WEED. 



Leaf-blades or their petiole-like bases connate-perfoliate. 1. S. perfoliatum. 



Leaf-blades not connate-perfoliate. 



A. Leaf-blades 1-2-pinnately parted : stems rough-pubescent. 



a. Ray-flowers with white ligules : stems less than 1 m. tall. 2. S. albiflorum. 



