The seeds of Lupinus. develop in greenisgh pods, much like garden peas. As in the image to the left, when the seeds mature, the pods turn dark and become brittle.
As the pods dries, a fiber along the bottom hinge of the pod tightens, causing the pod to twist, pop open, and discharge the seeds.
I've heard tell of strolling on the mountain while the lupine pods are popping, but have yet to catch this experience.
The image at left shows some of the seeds still in the just opening pods.