COMPOSITAE (COMPOSITE FAMILY) 



479 



FIG. 332. Western Tickseed 

 Sunflower (Bidens aristosa) . 

 Xi. 



clusters ; outer bracts of the invo- 

 lucre eight to ten, linear or spatu- 

 late, not exceeding the inner row; 

 rays six to ten, broad, obtuse, bright 

 golden yellow. Achenes obovoid, flat, 

 rough-hairy, tipped with two (occa- 

 sionally four) slender, diverging awns, 

 sometimes as long as the achene itself 

 or sometimes reduced to short teeth ; 

 the barbs on the awns and on the sides 

 of the achenes are on some directed 

 downward, on others upward. (Fig. 

 332.) 



Means of suppression the same as 

 for Bidens frondosa. 



TAR WEED 



Madia sativa, Molina 



Introduced. Annual. Propagates by seeds. 



Time of bloom: May to October. 



Seed-time: June to November. 



Range : Pacific Coast from California to Washington. 



Habitat : Fields, roadsides, and waste places. 



A most unpleasant weed, covered with a viscid, ill-scented excre- 

 tion which injures everything that it touches, from the crops among 

 which it is harvested to the clothing of passers-by. None of the 

 native Tarweeds are so offensive as this, which is an immigrant from 

 Chile. A remarkably sweet and limpid oil is expressed from the 

 seeds, good for table use and particularly valuable for a lubricant, 

 as it does not readily congeal ; in order to obtain this oil the plant is 

 extensively cultivated in South America and in Europe. Stem 

 stout, one to four feet tall, finely hairy, beset with viscid, pedicel- 

 late glands. Leaves alternate, entire, varying from broad lance- 

 shape below to linear above, all sticky and strong-scented. Heads 

 numerous, sessile or on short peduncles at the ends of the short 

 branches and in the upper axils ; they are about three-fourths of an 

 inch broad, with eight to twelve pale yellow rays and darker disk. 



