DICOTYLEDONS: SYMPETALA 311 
heads of composites have the general structure described 
for Arnica; but in the dandelion and its allies the disk- 
Fie. 298.—Arnica: A, plant bearing an open head, showing the conspicuous rays 
and disk; B, ray-flower; C, disk-flower.—After Horrman. 
flowers are like the ray-flowers, with conspicuous strap- 
shaped corollas (Fig. 299). 
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