Echinacea blossoms such as the one at the left are typical members of the Composite Family, as described on our Composite Flower Page. However, certain features do distinguish them from all other Composites.
For example, at the right you can see that Echinacea's central ray flowers are distributed over a hill-like receptacle, making the cluster of ray flowers look a little like a porcupine. Most composite blossoms have flat or only slightly elevated receptacles. Also in that picture notice that the involucral bracts are long and slender, green, stiff, and pointed downward. A botanist would refer to them as reflexed involucral bracts. The involucral bracts of most composite blossoms are more triangular, closer packed with one another, and pointed upward, not downward.
At the left you see more special features that make an Echinacea flower an Echinacea flower. First, notice that the ray flower bears no stigma. That's because in Echinacea the ray flowers are sterile. They don't have functional female parts and therefore the item at the base of the flower does not develop into a seed-like achene. In Echinacea the ray flower is strictly for drawing attention to the flower by pollinators. Ray flowers of many composite blossoms do produce viable achenes, and thus do have conspicuous stigmas.
Echinacea disk flowers have two unusual features. First, notice the large, stiff, orange-tipped, scoop-shaped receptacle bract partially folding around the flower. Many composite blossoms have no receptacle bract at all, and the vast majority of those who do have bracts that are much smaller, softer, and pale to transparent. In fact, when you look at an Echinacea blossom's center, the pointed things you think must be the disk flowers are actually bracts. Remember that in flowers a bract is a modified leaf.
On our Composite Flower Page we mention that many kinds of pappus exist, maybe the most common type being very small, slender, white hairs that, once the achene is mature, reside atop the achene and serve as a parachute for wind dispersal. Echinacea's pappus consists of a thick crown, toothed at the angles. In the above picture an arrow points to a large pappus tooth.