COMPOSITAE (COMPOSITE FAMILY) 479 
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. 
Fic. 332.— Western Tickseed 
TARWEED Sunflower (Bidens  aristosa). 
X 4. 
Média sativa, Molina 
Introduced. Annual. Propagates by seeds. 
Time of bloom: May to October. 
Seed-time: June to November. 
Range: Pacifie 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 Europé. 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. 
