The iris encyclopedia is online (
http://wiki.irises.org/bin/vie...). But, the Database here at ATP includes every variety of iris listed in the American Iris Society's registry. For what it is worth, there are around 200 irises with Mary as part of the name:
http://garden.org/plants/searc...
You can narrow that down a lot if you know other details about Mary X (or any other iris). For example, the vast majority iris entries in the ATP Database already have their parentage listed. So, if you know the parentage, or even just one of the parents, you can use the "search by characteristics" function to get a list of varieties with a given parent/parentage.
The Irises Database
http://garden.org/plants/group...
