There is remarkably little variation among plants in this genus. That is, in regard to the flowers. The heads are two or three inches across. Put a bunch of different ones together, and you would have a tough time sorting them out. Their fascination is that the ray flowers are only pistillate. Those long pistils sticking out of the disc flowers? They don't function to produce seeds. Disc flowers are functionally staminate. The shorter dark staminate tubes do work. Variation in that regard in the aster family gives us flowers like this, or with the roles reversed, or with everything functioning, or with sexes separated onto different plants. Often they self fertilize, but the arrangement here prevents that. Endless variation. Flowers playing their own kinds of music!