2n means that each chromosome is present in two copies (i.e. diploid). The chromosome count of a triploid should be indicated as 3n=33. Saying that a triploid has a chromosome count of 2n=33 is a contradiction in terms. A haploid gamete would be n=11, indicating a single copy of each chromosome, and the problem is that triploids produce haploid gametes. They produce gametes with an unstable chromosome count, some chromosomes in a single copy, and some in more than one. Among polyploids, plants with even ploidy (2N, 4N, etc) tend to be fertile, while those with odd ploidy (3n, 5n, etc) tend to be sterile. Various websites suggest that H. petiolatum has a chromosome count of 55, making it a pentaploid, 5n = 55. If there are 77 chromosomes, it would be septaploid, 7n=77. In any event, I'm pretty sure that its chromosome count should not be presented as "2n=[some number]", because implies two copies of each chromosome, when H petiolatum will actually have 5 (or more) copies. What I find confusing about Hippeastrum breeding is the repeated claim on various websites that diploid species cannot be successfully crossed with the big commercial hybrids, because the commercial hybrids are tetraploid. I would have expected the offspring of such a cross to be viable, though sterile, triploids. If those crosses do not produced offspring, it suggests that there is something else going on. Nick On Tue, Jan 13, 2015 at 10:30 AM, James SHIELDS <jshields46074@gmail.com> wrote: > "2n" just means just the whole set of chromosomes in the plant's cells. > For a diploid of 2n=22 species, the triploids have a total of 33 > chromosomes per cell, so 2n=33 for those triploid sorts. It also suggests > why most triploids and why petiolatum with 2n=77 do not often set seeds. > > Jim S. >