When I took pictures for that article I did it at 4 different points in time. Here's all the shots from those days.
http://images.aquaria.net/plants/Cry...28jan2007t.jpg
Jan suggested it might be C. cordata var. gabowski based on records. Witte disagrees and suggests it's probably cordata var. cordata.
We won't know till it flowers and this particular stand of plants hasn't flowered since - literally - 1953. So don't hold your breath!