Abstract
1) In this paper, meiotic chromosome pairing and pollen fertility of polyhaploid plants (2n=24) of S.tuberosum (variety Deodara), under two different seasonal conditions, are described in comparison with those of tlle closely allied diploid species S. stenotomum (2n=24 ). 2) The polyhaploids were found to show a frequent occurrence of unpaired chromosomes and an occasional formation of trivalents under unfavorable conditions, in spite of the fact that S.stenotomum had regular meiotic pairing under the same conditions. The pollen fertility of the former plants was extremely low, in contrast witn that of the latter. 3) On the basis of these results, affinity between the two chromosome sets of the polyhaploids is discussed and consequently it is suggested that S. tuberosum can be considered as a segmental allotetraploid.
