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, rosin weed (compass plant), rag- 



A D 



FIG. 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, 

 and 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 



