Two new types of double flowers (D3d and Dd3) were secured in 4n Portulaca. After 14 generations of selfing, pollen of 4n Datura stramonium retains large size characteristic of newly induced tetraploids. Effect of doubling chromosome number upon shape of fruits depends upon genic constitution but generally growth in width is favored. Doubling chromosomes may render sterile hybrids fertile to form double diploids when sterility is due to chromosome incompatibility but fertility may be increased by chromosome doubling in a hybrid (D. metel X D. meteloides) which shows chromosome circles involving interchanged chromosomes. Colchicine and other polyploidizing agents usually fail to produce balanced polyploid condition. Chromosome deficiencies as well as sectorial, mixo- and periclinal chimeras are frequent. The latter prove the existence of 3 germ layers in Datura. Polyploidy in each layer (especially the innermost) affects capsule shape. Since first layer forms central tissue of style through which pollen tubes grow and pollen tubes of a 4n flower burst in a 2n style, a 2n, 4n, 2n periclinal chimera fails to form capsules when selfed. Doubling chromosome number tends to decrease crossability among 10 spp. of Datura. A 4n dioecious race of Melandrium has been established as also a 2n type with XXY chromosomes which is hermaphroditic and self-able. By injns. of auxins into ovary, pseudoembryos are induced to develop from maternal tissues outside the embryo sac.