Ed, Wes and Paul all correctly identified Friday’s flower as a morning glory, probably an Ipomoea spp. (They also made me feel rather soiled for pedaling flower porn. Sheesh.)
What I find fascinating about these flowers is the unearthly glow at the center. They’re pollinated by bumblebees among other species, and bees see best in the blue-violet-ultraviolet range. If we were able to see this flower under UV light, you’d see those white areas become completely dark, creating a bullseye for bee approach.
Here’s why the white areas turn dark. The pigments in a white flower are flavonoids, which absorb UV radiation and reflect visible light. We don’t see into the UV range, so to us they look white (all that visible light bouncing back). But bees and some other insects do see UV light, and these flavonoid pigments create patterns to help them find nectar and pollen.