Cytology; aceto-orcein-stained squashes examined with a Zeiss x 63 n.a.1.4 objective and transmitted light, apart from (5), which is a composite fluorescent image made with blue and green excitation. Mitotic preparations were made from root tip cells and meiotic squashes from pollen mother cells. Scale bar=5 μm. (1) Meiosis in F. x conollyana (2n=54) showing 22 bivalents (the F. japonica complement), the 10 larger F. baldschuanica chromosomes remain unpaired. (2) Meiosis in triploid F. x conollyana (F. japonica var. compacta x F. baldschuanica 2n=32) is much more irregular than in the 2n=54 plants; the 22 F. japonica chromosomes are unable to pair regularly and there is a mixture of multivalents, bivalents and univalents. (3) Mitosis in a putative F. japonica x M. australis hybrid (2n=54), all chromosomes are more or less the same size c.f. F. x conollyana (4). (4) F. conollyana (2n=54) mitosis showing the 10 conspicuously larger chromosomes from F. baldschuanica. (5) GISH image of a putative F. japonica x M. australis hybrid (2n=54), the 10 green chromosomes (arrowed) have labelled M. australis DNA hybridised to them. (6) Mitosis in a F. sachalinensis x F. baldschuanica hybrid (2n=32), the 10 F. baldschuanica chromosomes are conspicuously larger.