Ballhead Waterleaf (Hydrophyllum capitatum)

Ballhead waterleaf; Dry Canyon Trail, 5/18/2013, David Kenison; click to enlarge

The Ballhead Waterleaf (Hydrophyllum capitatum) or "woollen breeches" is among the early bloomers in the late spring, known for its beautiful delicate bloom cluster in shades of light purple or violet, occasionally white.  The long stamen extend beyond the small blossoms.  The flower can be found throughout western North America.  It grows best in moist or shady environments.  The 1- to 2-inch flower heads are on stalks that are often 4-8 inches long.

The plant is edible.  It's said that Native Americans and pioneer settlers gathered both the tender young shoots and leaves, and the fibrous roots, as a food source.

These additional photos showing the plant and the bloom in various stages were taken on 5/10/14 in Dry Canyon by the author; click to enlarge.

Additional links:
USDA description
Wildflowers of the Southern Rockies