336 



THE KINDS OF PLANTS 



496. Xanthium Canadense. 



1. TARAXACUM. Dandelion. 



Stemless herbs, the 1-headed scape short, leafless and hollow: florets all 

 perfect and strap-shaped: fruit ribbed, the pappus raised on a long beak. 



T. officinale, Weber (T. Dens-leonis, Desf.). Common dandelion. Figs. 

 8, 275. Perennial, introduced from the Old World : leaves long, pinnate or 

 lyrate: heads yellow, opening in sun. 



2. CICHORIUM. Chicory. 



Tall, branching perennials, with deep, hard roots: florets perfect and 

 strap-shaped : fruit lightly grooved, with sessile pappus of many small, 

 chaffy scales. 



C. Intybus, Linn. Common chicory, run wild 

 along "roadsides (from Europe): 2-3 ft. : leaves ob- 

 long or lanceolate, the lowest pinnatifid : flowers 

 bright blue or pink, 2-3 together in the axils on long 

 nearly naked branches. 



3. XANTHIUM. Clotbub. 



Coarse homely annual weeds with large alter- 

 nate leaves, flowers monoecious : in small involucres : 

 sterile involucres composed of separate scales, in 

 short "racemes : fertile involucres of united scales 

 forming a closed body, clustered in the leaf axils, becoming spiny burs. 



X. Canadense, Mill. Common clotbur. Fig. 496. One to 2 ft., branch- 

 ing: leaves broad-ovate, petioled, lobed and toothed: burs oblong-conical, 

 1 in. long, with 2 beaks. Waste places. 



X. spinosum, Linn. Spiny clotbur. Pubescent, with 

 three spines at the base of each leaf: bur Y z in. long, 

 with 1 beak. Tropical America. 



4. AMBROSIA. Ragweed. 



Homely strong-smelling weeds, monoecious: sterile 

 involucres in racemes on the ends of the branches, the 

 scales united into a cup: fertile involucres clustered in 

 the axils of leaves or bracts, containing 1 pistil, with 

 4-8 horns or projections near the top. Following are 

 annuals : 



A. artemisiaefdlia, Linn. Common ragweed. Fig. 

 497. One to 3 ft., very branchy: leaves opposite or al- 

 ternate, thin, once- or twice-pinnatifld : fruit or bur 

 globular, with 6 spines. Roadsides and waste places. 



A. trifida, Linn. Great ragweed. Three to 12 ft., 

 with opposite 3-lobed serrate leaves: fruit or bur ob- 

 ovate, with 5 or C tubercles. Swales. 

 5. AGERATUM. Ageeatum. 



Small diffuse mostly hairy herbs, with opposite simple leaves: heads 

 small, blue, white or rose, rayless, the involucre cup-shaped and composed 

 of narrow bracts: torus flatfish: pappus of a few rough bristles. 



Ambrosia artem- 

 isiasfolia. 



