chromosome numbers are irrelevant to get results in making crosses. Just relatedness counts. I made crosses between a sedum that is twentyploid with a graptopetalum that is twelveploid or with a sedum that is diploid. It is only the next generation where problems might arise. There is usually no problem to cross dipliods with tetraploids. Only the resulting triploid is usually largely sterile. Another example: humans and guppies ( fishes) have the same chromosome number 2n=46 I don't think they cross although seeing some people....................(Joke) Ben J.M.Zonneveld NCB Naturalis, Herbarium Section Pobox 9515, 2300 RA Leiden The Netherlands Telf: +31 71 5274738