DICOTYLEDONS: SYMPET^LuE 



311 



heads of composites have the general structure described 

 for Arnica; but in the dandelion and its allies the disk- 



Fio. 298. Arnica: A, plant bearing an open head, showing the conspicuous rays 

 and disk; B, ray-flower; C, disk-flower. After HOFFMAN. 



flowers are like the ray-flowers, with conspicuous strap- 

 shaped corollas (Fig. 299). 

 21 



