CH. XIII] 



THE DICOTYLEDONS 



557 



paratus to the dissemination of a single seed. It is cer- 

 tainly a curious fact that this highest of the plant groups 

 has returned to the arrangement in which the individual 

 flower is subordinate to the cluster, and has returned also 

 f,nwj p d Hi aspm i n flti nn 



FIG. 400. Section through a flower head of Coreopsis, exhibiting the 

 showy marginal flowers, which are sterile, and one of the inconspicuous disc 

 flowers which is fully fertile. Next the latter is its subtending bract, and 

 other bracts appear below. (From Bailey.) 



very widely distributed. They include a great many 

 economically important forms, Lettuce, Jerusalem Arti- 

 choke,, and many plants cultivated for ornament ; Chrysan- 

 themum, Aster, Marigold, Daisy^ Cineraria, Cosmos, 

 Dahlia, Sunflower, Golden Glow, Goldenrod, with Dande- 

 lion, Marguerite, and many of our weeds. This family 

 represents clearly the present acme of plant evolution. 



