This species is remarkable for its variable merosity (number of floral parts). Almost all Heuchera species have five sepals, petals, and stamens; Heuchera eastwoodiae, discovered in the 1930s, has six of each. This one has five of each, six of each, and everything in between! It is also specific to sandstone -- apparently the only species of the western US with this habitat requirement.
Flowers:
A flower with an intermediate number of parts: