AMBROSIACEAE. 



[Vol,. III. 



2. Xanthium strumarium L,. 

 Broad Cocklebur or Bur weed. 



(Fig. 3599-) 

 Xanthium strumarium L. Sp. PI. 987. 1753. 



Rough, \-6 l /2 high. Leaves slender- 

 petioled, broadly ovate to orbicular, 3-ribbed 

 and cordate or cordate-reniform at the base, 

 the lower often io' wide, the margins den- 

 tate, or more or less 3-5-lobed, both surfaces 

 roughish and green; bur oblong, glabrous or 

 puberulent, 6 // -o/ / long, about 3" in diame- 

 ter, its 2 sharp conical-subulate 2 toothed 

 beaks straight or nearly so, equalling or 

 slightly longer than the numerous, nearly 

 glabrous or pubescent spines. 



In waste places, New England and New York 

 to Nebraska, south to Florida and Mexico. 

 Naturalized from Europe or Asia. Called also 

 Ditch-, Sheep- or Clot-bur, Button Bur, Small or 

 Lesser Burdock, Sea Burdock and Bur-thistle. 

 Aug. -Oct. 



3. Xanthium Canadense Mill. 



American Cocklebur. Sea Burdock. 



Hedgehog Burweed. (Fig. 3600.) 



X.CanadenseMill.Gaxd. Diet. Ed. 8, N0.2. 1768. 

 Xanthium echinatum Murr. Conim. Goett. 6: 



32. pi. 4. 1783. 



Similar to the preceding species, usually 

 stouter, the branches ascending or diffuse. 

 Leaves similar and roughish and commonly 

 thicker; stem often brown-spotted; bur ob- 

 long, usually densely hispid, 9 // -i2 // long, 

 4 // -6 // in diameter, the two stout beaks 

 hooked or incurved at the apex, longer than 

 or equalling the more or less hispid stout or 

 slender hooked spines. 



Along rivers and sea-beaches and in waste 

 places, Nova Scotia to North Carolina, west to 

 the Northwest Territory, Nevada, Texas and 

 Mexico. Not common in the interior region 

 east of the Mississippi. Aug.-Oct. 



Family 43. COMPOSITAE Adans. Fam. PI. 2: 103. 1763. 



Thistle Family. 

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

 (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 subtend- 

 ing the flowers, smooth, or variously pitted or honeycombed. Calyx-tube com- 

 pletely adnate to the ovary, the limb (pappus) of bristles, awns, teeth, scales, 

 or crown-like, or cup-like, or wanting. Corolla 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; 

 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 rough or prickly. Ovary i-celled; ovule 

 1, anatropous; style of fertile flowers 2-cleft, its branches variously appendaged, 

 or unappendaged ; stigmas marginal ; style of sterile flowers commonly undivided. 

 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. The family- 

 is also known as CARDUACEAE.AGGREGATAE, and by the English name of Asterworts. In Kuhnia, 

 the anthers are distinct, or nearly so. 



