Pipewort
A new flower to me that I found on a lake shoreline on Cape Cod:
For the identification, I have to thank Linda (shoreacres.wordpress.com). Linda recently posted another flower in this genus, Eriocaulon, and I saw the similarity. This flower is likely the common E. aquaticum or possibly the rare endemic E. parkeri. The flower is just a few millimeters across. It’s always best to bet it’s the common species – I’ll ask a botanist.
Nature Diary 
What a nice portrait of a fascinating flower. There’s no mistaking a pipewort, that’s for sure. Like you, I’d suspect this is E. aquaticum. On the other hand, E. parkeri is a Cape Cod native, despite its relative rarity. Whichever this one is, I’m glad you found it.
I wrote the botanist at Native Plant Trust, and he tells me it’s E. aquaticum. He didn’t say what feature/field mark gave it away, but I’ll take his word for it! 🙂 It was neat to find – a completely new flower to me.
This is a good picture if the subject is only a few millimeters across.
Thanks, Steve. It was tiny, taken at about 2x or 3x at f/5.6.