1. In the present report, a result of cytogenetical research on a hpyo-autotriploid plant having 2n=19 chromosomes was descr, bed. A single plant was raised from the hybridization between 2n and 4n rye in 1952. 2. The lengths of stems, spikes and awns of the plant were found to be shorter than those of both parents, while in the density of spikelets the hybrid was somewhat superior to the parents(Table 1 and Photo 1) 3. The percentage of seed fertility is 0. 79% and the value is much lower than that of the parents. 4. 20 kernels obtained from the hypo-autotriploid plant by selfpollination was sown on Octover 1953, but no germinated plant was obtained. 5. Two members of 19 chromosomes of the hypo-autotriploid plant have each a satellite at one end, while in eu-autotriploid each of 3 members of 21 chromosomes ought to have a satellite. 6. At the heterotyplc metaphase m merosls of DMC's 0-5 univalents and 7-9 bivalents (including trivalehts) were observed. The frequency of uni-and bivalents in PMC's was shown in Table 2. 7. Trivalents were observed, though rare, in addition to bivalents at the heterotypic metaphase, but no tetravalent was found. 8. The chrom:osome constitution of genomes in the plant may be considered as RRR - 2 from the result of the present research. 9, One or two of the bivalerits other than the 7 which resulted from conjugation between chromosomes of RR genomes may have been produced by autosyndesis between chrornosomes of R-2 genome as obseved by LEVAN (1942) in the case of haploid rye.
