COMPOSITAE. 913 



brous, especially above; burs commonly solitary in the axils, oblong, 1.5-2.5 cm. 

 long, half as thick, or less, the subulate-conic beaks slightly incurved, hooked at 

 the apex, about as long as the subulate uncinate prickles, which are hispid to 

 about the middle with brown hairs. Quebec to N. Y., Kans.. Mo. and Ariz. 

 Type collected by N. L. Britton at Westport, N. Y. 



7. Xanthium Macounh Britton, n. sp. MACOUN'S CLOTBUR. Stem purplish 

 or purple- blotched, about 2.5 dm. high. Leaves slender petioled, triangular- 

 ovate, acute, irregularly dentate, firm, scabrous on both surfaces; burs mostly 2 in 

 each axil, oblong, the body about 2 cm. long and 8 mm. thick, the stout prickles 

 very densely hispid, excepting their strongly incurved, glabrous lips, shorter than 

 the stouter, hispid incurved beaks, and than the diameter of the bur. Goose 

 Island, Lake Winnipeg, Manitoba, J. M. Macoun, Aug. 16, 1884. Specimen in 

 the herbarium of the Geological and Natural History Survey of Canada. 



8. Xanthium echinatum Murr. BEACH CLOTBUR. Stem rough, purplish 

 or purple-blotched, 3-6 dm. high. Leaves firm, scabrous, with scattered short 

 papillose hairs, obtusely toothed and lobed, somewhat resinous-glandular beneath; 

 burs commonly clustered in the axils, ovoid to oval, 15-20 mm. long, 8-12 mm. 

 thick, glandular; prickles very dense, densely hispid from the base to the middle or 

 beyond, subulate, hooked, the longer about 5 mm. long, and about equalling the 

 stout hispid beaks. Sea, lake and river beaches, N. C. to Mass., Que., northern 

 N. Y. and Minn. (X, maculatum Raf. ; X. oviforrne Wallr., ex descr.) 



9. Xanthium glanduliferum Greene. GLANDULAR CLOTBUR. Similar to 

 X. echinatum. Leaves very thick and scabrous with short stout papillae; burs 

 oval, 10-15 mm. long, 6-9 mm. thick, yellow, the prickles scattered, bristly-hispid 

 nearly to the hooked apex, scarcely as long as the conic-subulate short-bristly 

 beaks. Neb. to N. Dak. and Assiniboia. 



Family 5. COMPOSITAE Adans. 



Thistle Family. 



Herbs, rarely shrubs (some tropical forms trees), with watery or res- 

 inous (rarely milky) sap, and opposite alternate or basal exstipulate 

 leaves. Flowers perfect, pistillate, or neutral, or sometimes monoecious 

 or dioecious, borne on a common receptacle, forming heads, subtended 

 by an involucre of few to many bracts arranged in one or more series. 

 Receptacle naked, or with chaffy scales subtending the flowers, smooth, 

 or variously pitted or honeycombed. Calyx-tube completely adnate to 

 the ovary, the limb (pappus) of bristles, awns, teeth, scales, or crown- 

 like, or cup-like, or wanting. Coralla tubular, usually 5-lobed or 5-cleft, 

 the lobes valvate, or that of the marginal flowers of the head expanded 

 into a ligule (ray); when the ray-flowers are absent the head is said to be 

 discoid; 13 when present, radiate; the tubular flowers form the disk. 

 Stamens usually 5, borne on the corolla and alternate with its lobes, their 

 anthers united into a tube (syngenesious), often appendaged at the apex, 

 sometimes sagittate or tailed at the base; pollen-grains globose, often 

 rouirh or prickly. Ovary i-celled ; ovule i, anatropous; style of fertile 

 flowers 2-cleft ; stigmas marginal; style of sterile flowers commonly un- 

 divided. Fruit an achene. Seed erect; endosperm none; embryo 

 straight; hypocotyl inferior. About 760 genera and not less than 10,000 

 species, of wide geographic distribution. In Kuknia, the anthers are 

 distinct, or nearly so. 



* Anthers not tailed at the base ; stigmatic lines of the style-branches only at the base, 

 or not extending beyond the middle ; flowers all tubular and perfect, 



never yellow ; rays none. 

 Style-branches filiform or subulate, hispidulous ; receptacle naked. 



Tribe i. VERNONIEAE. 



Style branches thickened upward, obtuse, papillose. Tribe 2. EUPATORIEAE. 



** Anthers tailed at the base, unappendaged at the tip; heads small; rays none (ex- 

 cept in Inula, where they are large and yellow). 



Tribe 4. INVLEAE. 



