star duckweed, Lemna trisulca

Tell me I'm wrong! Better yet, tell me what this is? I had identified it as star duckweed. These surface fronds may be the very rarely seen flowering fronds. Undoubtedly they were with the submerged sterile fronds of star duckweed. You can see some of those lurking around below the surface here. The look like they're trifoliate with pointed ends. But I no longer remember if they were actually attached. Looking for images on line has been futile. Among the thousands I found two that look like this. Two other puzzled amateurs? Assuming this is star duckweed, it grows almost everywhere in the temperate world, with us in every state and province except FL, GA, HI, LA, MS, NC, OK, SC, WV, LB, and NF. Lenawee Co MI, 6/23/15. Arum family, Araceae.