Yoy can propagate Fiji by leaf stem,piece of rhizome, or even by the cone method and the resulting plant will be true. However if you propagate B. 'Cathedral' (sometimes incorrectly known as B. 'Cathedral Windows') from a leaf you will get B.'Fiji Islands', but if you propagate 'Cathedral' from a piece of rhizome you get 'Cathedral'. Obviously there is some connection between 'Fiji' and 'Cathedral', but the origin of both is obscure. This information originated with thelate Elda Haring who wrote extensively about begonias.