NYEric ,a semi-alba is enough?
http://www.flickr.com/photos/35673552@N06/3512600542/in/photostream
I still dont agree compleately about platiphyllum been a species,in my opinion can be a natural line breed kolopakingii(topperii type carrying alba genes) x stoneii...
Absolulety not semi-alba... there will be no albino with the plant shown in the link. that's a perfectly normal platyphyllum. All the blooms I have seen are very similar. This could have been a natural hybrid far in the past, but definitely a separate species now (or subspecies) or there would be significant variations.