Linda Goodwin sent these pictures with an explanation:
Cleared out dead pokeweed stalks yesterday & pale gold coins fell to the ground.
Turns
out pokeweed is one of the few plants (with walnut, butternut) that
produce ‘chambered pith’ inside the stalks / twigs. Found a research
paper from 1980 & photos from the NY Botanical Garden, but there’s
almost no info about this online.
Each layer is like a skinny Cheerio covered with tissue paper. Neat little things.