This is a type of montage - two images overlaid - that I post regularly in my PADs. The specific technique used here is the Orton technique - named for a Canadian photographer (is there something in the water north of the border? you have so many great photographers.) Read more about the Orton technique at - http://www.naturephotographers.net/articles0106/dw0106-1.html
Some attribute the technique to Andre Gallant (yet another Canadian) and others to Tony Sweet, but my (limited) research gives the nod for the earliest use to Orton.
I posted 15 other tulip images to my PAD rejects gallery - http://www.pbase.com/ed_k/pad_2nds_year_3