"The other parent looks like a Cereus "
To my knowledge, at least 10genera possess plants that look like cereus..
To list:
Neoraimondia
Stenocereus
Pachycereus
Polaskia
Trichocereus(now echinopsis)
Pilosocereus
Dendrocereus
Armatocereus
Myrtillocactus
Neobuxbaumia
Rauhocereus
Stetsonia
Corryocactus
...
So, thats a lot of plants that look like the original cereus to some degree...
Intergenic pollination has not been achieved, nor it is plausible....
Its likely somehow self pollinated in the process....
