Hmm...maybe a white form of Hydrophyllum virginianum?

I think he's nailed it.

Virginia waterleaf or eastern waterleaf.
Hydrophyllum virginianum.

thanks, Tugbrethil and Buddlejagar, i bought this last year, but forgot what it was..in this neck of the woods, in most of the nurseries, the plant is identified by a common name, and even most of the staff in the nurseries only know it by such, especially those temps for the summer..i remember Virginia waterleaf (now!)...am i correct in assuming it needs plenty of water in the shade? it's a lovely little plant..thanks again for your help,i would like to start cataloging my plants with both names..