The Chromosomal Constitution of Nubbin, a Compound (2n + 1) Type in Datura.

with so few individuals tested. Aside from these two mutations from this treated capsule and three or four mutations which occurred in Fl's from a haploid, we have not yet determined any gene mutations in Datura Stramonium. There were tested by selfing about 400 individual parents in the F2 or later generations from the haploid 1A without discovering a single gene mutation. Following treatment with radium emanation, we have obtained in the offspring from a single capsule-(a) 17.7 per cent chromosomal mutants (chiefly non-disjunctional forms3), a much higher percentage than ever obtained from untreated capsules, the average for over 15,000 offspring being 0.47 per cent; (b) a new compound chromosomal type, Nubbin; (c) two new gene mutants out of 18 individuals tested. It is our belief that for most, if not for all, of these three types of results, the radium treatment may be held largely responsible. * Brooklyn Botanic Garden Contributions, No. 49. 1 Gager, C. Stuart, "Effects of the Rays of Radium on Plants," Mem. New York Bot. Gard., 4, 1-278, 1908. Results also presented before Sect. G, A. A. A. S., Jan., 1907. 2 Stein, Emmy, "Ueber den Einfluss von Radiumbestrahlung auf Antirrhinum," Zeitschr. Indukt. Abstamm. Vererb., 39, 1-15, 1922. Also Ibid., 43, 1-87, 1926. 3 Cf. Mavor, James W., "The Production of Non-Disjunction by X-Rays," Science, 55, 295-297, 1922.