Let's split

 

Splitting seed pod of Willow Herb

Willow herb (Epilobium ciliatum) has loculicidal fruit.  The fruit is a long, slender pod that contains the seeds.  Loculicidal means that the pod splits longitudinally (lengthwise), sort of like peeling a banana (according to Michelle).

["Locule" means "little place" in Latin.  In plants, it's a small compartment (a chamber within the ovary) that contains the seeds.]

Here are a few more views of this graceful arching seed pod and its symmetrical arrangement of seeds.

 

Note that each seed has a white hair-tuft to aid in dispersal by wind.

 

Here's the flower itself. On Bodega Head it's found in freshwater marshes and wet roadside ditches.

 

P.S.  Happy Solstice!