The first point to know is that the egg-size item at the right is not a teasel flower, but rather many teasel flowers clustered together. Each of those little, pale, bluish things is a corolla.
On our Composite Flowers page we see that having flowers arranged like that is a feature of composite flowers, so what's going on? In fact, it's true that teasel flowers are fairly similar to composite flowers, but they're not. Teasels have their own family, the Teasel Family, the Dipsacaceae. Teasel flowers are separated from composite flowers for technical reasons. Specifically, in the Composite Family, stamen edges are grown together forming a cylinder around the style, but teasel stamens are separate. Also, Composite Family seeds contain albumen while those in the Teasel Family don't. Well, for us it's easier just to remember that teasels have their own family.
Despite these inconspicuous but important technical differences, similarities between the two families are striking. At the left you see a cross section of the above head. Notice how the individual flowers are packed side by side, arising from a fingerlike receptacle, just as with many composites. Also, notice the long, slender, upward-arching involucral bracts arising beneath the flower head, again as in many composites.
When you look at the individual flowers, shown at the right, the similarities are even more striking. The three blue things in the center are unopened corollas. Below the corollas are rectangular achenes, which are specialized dry fruits, exactly as among composites. Moreover, notice how each flower is nestled inside a scooplike scale topped with a long, sharp spike. This scoop is a chaffy scale, or bract, just as in many composite flowers -- for example, as is shown at the bottom of our Zinnia Page. Well, it's true that the Teasel Family is closely related to the Composite Family, so such similarities shouldn't surprise us.
At the left you see two teasel corollas fallen from the flower head. Of course the four items atop each corolla are the stamens, whose filaments arise from about midway up the inside of the corolla tube. The flowers are only about half an inch long (12 mm), so they are much magnified here.