American groundnut is normally 2n=2x=22, diploid, but both diploid and triploid forms exist. Thus, they can have diploid or even triploid germline cells. The first is the number of chromosomes&colon; whether the plant is diploid, triploid or tetraploid. Therefore, the sperm would be diploid, which means that their offspring would be triploid. These hybridization events produced the triploid cultivars of bananas commonly grown today. Cavendish bananas are a subgroup of the triploid (AAA) group cultivars of "Musa acuminata". The commercial banana is an example of a sterile, seedless triploid hybrid. The triploid forms are sterile, and reproduce only vegetatively, via bulbs. Triploid plants are infertile and show an abortive ovary with a shrivelled appearance. In 1931, Barbara McClintock discovered a triploid maize plant. Hybrids between the two are known, but are very rare, and being triploid, are sterile. The resulting cell is triploid (3n). Oligohydramnios, low levels of amniotic fluid, is common in triploid pregnancies. Common dandelion is a triploid that produces viable seeds by apomictic seed. The second sperm cell fuses with both central cell nuclei, producing a triploid (3"n") cell.