An Arnica mollis flower shows the structure of a typical Asteraceae that has ray and disk flowers:

The ray flowers are long, yellow, and strap-like around the perimeter of the flower head. 
The disk flowers are cylindrical: long and narrow.  The closed disk flowers in the above photograph are club-shaped. 
At the top of each yellow/green seed and surrounding each flower, there are silky pappus hairs (which in Arnica mollis are brownish, not silvery as in many other Asteraceae). 
The appendages that surround the entire flower head are phyllaries (also called bracts).  These are long, hairy, and green with red pointed tips.  The shape, color, hairiness, number, arrangement, etc. of these phyllaries help identify Asteraceae species.  (I peeled back several phyllaries to expose the flower parts.) 
In the above photograph, several small flowers have fully opened, and their yellow, curled styles and stigmas project above the flower head.