Cytological Observations in the Genus Phaseolus L.

Three species of the genus Phaseolus L. are reported upon. 1) Phaseolus lathyroides L. the name of which seems to be synonymous with Ph. semi-erectus L., has 2n = 22. This is in accordance with previous counts. 2) Phaseolus hysterinus Dur. has 2n = 22, but many cells in the inner cortical layer of the root are polysomatic. 3) Material of Phaseolus sublobatus Roxb., a species recently studied by Datta & Sen, has been studied again: 2n = 22 and in a small number of seeds 2n = 44 could be reported, hence a case of spontaneous tetraploidy in Phaseolus. Owing to the smallness of the chromosomes a complete analysis of the karyotype is nowhere attempted at and seems of dubious value for breeding work. At most can be stated that all three species in diploid condition show one large pair and one satellited pair of somewhat smaller chromosomes. These are present twice in the tetraploid.