I forgot one of the more known strange crosses that happens (and has been repeated) that shouldn't be possible....Paltec (and similar) between bearded (i.pallida) and crested (i.tectorum).
Having said that though, based on the seed picture I imagine most are selfs. Most reports on the wide sectional crosses tend to stress the seeds look deformed and the pods they come from usually have very few seed. But there's a lot of odd crosses that have resulted in unique irises out there which demonstrate the possibility that all the rhizome iris can interbreed...just possibly very very rarely and generally resulting in sterile offspring at the diploid level.
