THE comparatively recent discovery of the ease with which the chromosome number in plants may be doubled by using colchicine appears likely to greatly stimulate interest in flower breeding. As a rule tetraploids have larger flowers and fruits than diploids, and in addition, as pointed out by Mihitzing (1936), they usually bloom later and thus may extend the flowering season in some localities. All these characteristics have important bearing on the commercial value of many ornamental plants. The work of Nebel and Ruttle (1938) in inducing tetraploidy by using colchicine in marigolds, petunias, snapdragons and pinks, indicated some of the possibilities in ornamentals. Blakeslee and Avery (1937) reported induced tetraploidy in Portulaca, and Levan (1939) both tetraploidy and octoploidy in Petunia. Later Ernsweller and Brierley (1940) secured tetraploid forms of Lilium formosannum by using colehicine, and recently Weddle (1940) reported induced polyploidy in Chrysanthemum and Calendula. In this paper consideration will be given to the more recent investigations carried on by the senior author and his colleagues at the United States Horticultural Station, Beltsville, Md., and by the junior author at the Agricultural Experiment Station, Geneva, N. Y. 1 Approved by the Bureau of Plant Industry, U. S. Department of Agriculture, and the Director of the New York State Agricultural Experiment Station, as journal paper 437, March 19, 1941.