CARDUACEAE 1251 



peduncled. Involucres hemispheric, several-flowered : bracts imbricated in 2-3 series, 

 ovate to lanceolate, nearly equal in length. Receptacle hemispheric. Ray-flowers want- 

 ing. Disk-flowers perfect, fruit-producing : corollas with wide throats. Anthers not 

 caudate. Stigmas with pubescent subulate appendages. Achenes 4-angled, broadened 

 upward, truncate. Pappus of 2 or several caducous awns. 



Leaf-blades manifestly hastately lobed. 



Bracts of the involucres scale-like, shorter than the disk. 



Mature leaf-blades less than 5 cm. long ; middle lobe broadened upward. 1. Jtf. parvifolia. 



Mature leaf-blades much over 5 cm. long; middle lobe narrowed upward. 2. M. nivea. 



Bracts of the involucres foliaceous, surpassing the disk. 3. M. lobaia. 



Leaf-blades triangular, ovate, rhombic or broadened upward, without hastate lobes. 



Leaf-blades linear or broadest above the middle, several times longer than broad. 4. JI/. lanceolata. 

 Leaf-blades broadest below the middle, rarely twice as long as broad. 



Bracts of the involucres rhombic to ovate, shorter than the disk. 5. M. deltaidea. 



Bracts of the involucres lanceolate, fully as long as the disk. 6. M. Carpenteri. 



1. Melanthera parvifolia Small. Foliage hispidulous. Stems 3-8 dm. tall, simple 

 or branching : leaves opposite ; blades 2-5 cm. long, ovate-lanceolate in outline, 3-lobed, 

 sessile or short-petioled, the middle lobe elongated, more or less broadened above the 

 middle, sparingly serrate, the lateral lobes short, often tooth-like, entire or toothed : pe- 

 duncles densely hispidulous: heads not showy : involucral bracts not foliaceous, oblong to 

 ovate-lanceolate, scabrous-hispidulous, acute, ciliate : disks about 1 cm. broad ; achenes 2 

 mm. long, nearly smooth. 



In sand, peninsular Florida and the Keys. 



2. Melanthera nivea (L. ) Small. Foliage scabrous. Stems 8-24 dm. tall, 

 blotched with purple, branched : leaves opposite ; blades ovate to lanceolate in outline, 

 hastate or hastately 3-lobed, with the middle lobe narrowed upward, 8-15 cm. long, irregu- 

 larly serrate, finely pubescent beneath : pedimcles scabrous : heads not showy : involucral 

 bracts not foliaceous, ovate to ovate-lanceolate, surpassed by the disk, scabrous : disks 

 1.5 cm. broad : achenes nearly 3 mm. long, tuberculate. [Bidens nivea L. M. hastata 

 Michx. J 



In wet soil, South Carolina to Florida and Louisiana. Also in tropical America. Spring to fall. 



3. Melanthera lob^ta Small. Foliage scabrous and hispidulous. Stems 8-18 dm. 

 tall, branching, blotched with purple : leaves opposite ; blades ovate in outline, 8-15 cm. 

 long, scabrous on both sides, finely pubescent beneath, 3-lobed, the lateral lobes basal, 

 spreading, each with an erect lobe, margins of all the lobes crenate, the teeth sometimes 

 apiculate : peduncles densely hispidulous : heads not showy : involucral bracts foliaceous, 

 lanceolate or linear-lanceolate, 9-10 mm. long, surpassing the disk, hispidulous : disks 

 flat, about 1.5 cm. broad. 



About lakes and ponds, peninsular Florida. Summer. 



4. Melanthera lanceolata Benth. Foliage strigillose. Stems 2-8 dm. tall, more or 

 less branched : leaves opposite, sometimes clustered ; blades linear or linear-oblanceolate, 

 4-8 cm. long, acute or somewhat acuminate, rather coarsely serrate, or sometimes repand, 

 attenuate into slender petioles : heads not showy : peduncles densely strigillose : involucral 

 bracts not foliaceous, broadly linear to oblong-lanceolate, surpassed by the disk, acute, 

 minutely ciliolate. 



In sand, peninsular Florida. Spring to fall. 



5. Melanthera deltoidea Michx. Foliage more or less scabrous or strigillose. Stems 

 3-10 dm. tall, branched : leaves opposite ; blades firm, deltoid, ovate, or lanceolate above, 

 acute or somewhat acuminate, serrate-dentate or crenate, cuneate to truncate at the base : 

 peduncles slender, strigillose : heads not showy : involucral bracts ovate to rhombic, acute 

 or rather obtuse, strigillose and ciliate : disk surpassing the involucral bracts : achenes 

 broadly cuneate, 2 mm. long, tuberculate-roughened. 



In sandy soil, peninsular Florida and the Keys. 



6. Melanthera Carp§nteri Small. Foliage strigillose and scabrous. Stems 3-11 dm. 

 tall : leaves opposite ; blades membranous, ovate to ovate-lanceolate, 8-15 cm. long, acu- 

 minate, dentate or crenate-dentate, broadly cuneate at the base : peduncles slender, densely 

 strigillose : heads not showy : involucral bracts not foliaceous, lanceolate, acuminate, 

 ciliate : disks about 1 cm. broad, equalled by the involucral bracts or surpassed by them. 



In pine thickets, Louisiana. Summer. 



84. ISOCARPHA R. Br. 



Annual or perennial caulescent herbs. Leaves opposite or alternate : blades flat, 

 sometimes 3-nerved. Heads discoid, solitary or clustered. Involucres low, several-flow- 



