312 A TEXT-BOOK OF BOTANY 
Some of the well-known forms, either wild or in culti- 
vation, are ironweed, -ageratum, blazing star, goldenrod, 
daisy, aster, everlasting, rosinweed (compass plant), rag- 
, 
" 
Fic. 299.—Dandelion: A, two flower-stalks, one head being closed and showing 
the double involucre, the other open and showing all the corollas strap-shaped; 
B, single flower; C, akene; D, receptacle, with single pappus-bearing akene.— 
After STRASBURGER. 
weed, cockle-bur, zinnia, sunflower, dahlia, cosmos, mari- 
gold, chrysanthemum, tansy, sage-brush, burdock, thistle, 
end dandelion. The only plant extensively used for food 
is lettuce. 
175. Other useful Sympetalae.—Some well-known plants 
that are not included in the families given above, but that 
