Those are Buttonbush flowers, Buttonbush being CEPHALANTHUS OCCIDENTALIS of the Coffee Family, the Rubiaceae. In fact, Buttonbush leaves have the same shape and general appearance of Coffee bushes. If you're in North America you probably know Buttonbushes because they're common in wetlands from southeastern Canada and California south to Honduras, sometimes forming nearly impenetrable thickets.

In the picture, each spherical item is a 1.3-inch wide cluster of many flowers. If you look closely at the white cluster you can see the individual flowers, which are white and very slender. Each tiny flower bears at its top four petal-like lobes (sometimes five), and four stamens (rarely five) protruding from the corollas. In the picture, the stamens are topped with very small, oval, brownish anthers, which open to release pollen. The stiff-looking, white, sticklike things below the anthers are the stamens' filaments.

Anatomically, most flowers are "superior," meaning that their sepals or calyx lobes, petals or corolla, and stamens all arise below the ovary. Flowers in the Coffee Family are "inferior," meaning that those flower parts arise above the ovary.

Once the flowers are pollinated they fall off, leaving the many closely packed ovaries forming small, green balls considerably smaller than the white balls in the picture. Eventually the spheroid of ovaries matures into a dark-reddish-brown cluster about 3/4-inch in diameter, the individual ovaries squeezed together so tightly that the cluster looks like just one brown fruit. However, as winter comes on and the balls dry out, they crumble into individual dry fruits.

Ducks eat these achenes and deer browse on Buttonbush's twigs and foliage, but, relative to the bush's abundance, not to any great extent.