1. Octoploid and tetraploid plants were obtained from seeds of Gossypium hirsutum and G. herbaceum treated with colchicine. 2. The seeds of G. herbaceum were generally homozygous and reacted as a rule more uniformly to the drug than did the seeds of G. hirsutum. 3. Microsporogenesis in octoploid (2n = 104) G. hirsutum is described in some detail: a few chromosomal irregularities were observed and the pollen grains are larger than in the normal tetraploid plants. In spite of the fact that empty pollen grains were rarely found, the plants are highly sterile. The anthers are almost always indehiscent. 4. Flowers with dehiscent anthers were self-pollinated, and others were cross-pollinated with pollen from tetraploid and octoploid plants. No fruit set occurred. 5. A few fruits from open-pollinated flowers have been obtained. Their seeds were in some cases almost spherical and were larger and heavier than the normal. The seed coat was very hard and the percentage of germination low. These seeds yielded normal tetraploids (2n = 52).