HiSteve,
I don't know much about "A. x amazonica" though it appears notto be a validly published botanical name. I am not aware of the namegoing back before the 1950's, though the hybrid plant mightwell go back to the 19th century (and been re-made later), as therewere many hybrids made then. Plants have sometimes been givencompletely erroneous geographic epithets, like the Asian Lycorisafricana, and the African Nerine sarniensis, to take two examples fromAmaryllidaceae, but I think the origin being the name of the nurserymay be correct in this case. IMO the IAS as ICRA for aroids shouldpublish a determination that "Alocasia x amazonica" is the correctlycultivar Alocasia 'Amazonica'.
By the way, the Alocasia nobilis your ?Belgian correspondentrefers to is an illegitimate name because of the prior A. nobilisHallier f. (an unrelated Sumatran species). 'Nobilis' cannot be usedas a cultivar epithet in Alocasia (for a form of A. sanderiana) becauseof the existence of Alocasia nobilis Hallier f., if my interpretationof the ICNCP is correct.
I remember agonizing over whether to include A. watsoniana inthe A. longiloba complex. He hasn't grown enough of the variable plantsin the complex, I suspect. What look like different species incultivation become much more blurred if one looks (at more variability)in the wild. I suspect the cultivated big watsoniana should also begiven the status of cultivar, Alocasia 'Watsoniana'. Many of theseproblems with and unending arguments/discussions about"horticultural-botanical" hybrids and species can be simplycircumvented by making them cultivars.
Alistair