You wouldn't necessarily have to remove or add anything. I'm not an expert on ferns, but they have what...23,000 genes or something? Compare that to Arabidopsis, which has...i can't remember the exact number...but its less than 10. Usually plants will sort themselves out, i mean...look at polyploidy. Also, yes, GMOs are created by cutting a gene from DNA of an organism and inserting it to another, but this is done for disease resistance, ability to tolerate a wider temperature range, etc. If a cross doesn't work, its not going to work. Gene splicing (at least not in the near future) wouldn't allow two organisms that have divered so far in the past to be hybridized. To get that effect, you'd probably have to create a graft chimera