Resumo em Inglês:

Forty-five plants including an hybrid of N. tabacum L. x N. glutinosa L., were tested as to the susceptibility to "vira-cabeça". Of all the plants tested Nicotiana paniculata L. proved to be the best for the study of local lesions, these being very clear-cut 4 days post-inoculation. Petunia sp., Nicandra physaloides Gaertn., Nicotiana glutinosa L., come next as good indicator plants also.

Resumo em Português:

1. Plantas tetraplóides e octoplóides foram obtidas de sementes de Gosjypium herbaceum e G. hirsutum, tratadas com colchicina. 2. As sementes de G. herbaceum eram bastante homozigotas e reagiram em regra mais uniformemente para o alcalóide do que as de G. hirsutum. 3. A microsporogênese em G. hirsutum octoplóide (2n = 104) é descrita com algum detalhe; algumas irregularidades cromosômicas foram observadas; os grãos de polen são maiores que os das plantas tetraplóides normais. A despeito de se encontrarem raros grãos de polen "vazios", as plantas são altamente estereis. As anteras são quase sempre indeiscentes. 4. Não se conseguiu frutificação quando as flores com anteras deiscentes foram autopolinizadas e quando outras flores foram polinizadas com polen de plantas tetraplóides e octoplóides. 5. Alguns frutos foram obtidos de flores não manipuladas, e, portanto, de polinização não controlada. Em alguns deles as sementes eram quase redondas, maiores e mais pesadas que as normais; a testa da semente era dura e a percentagem de germinação baixa. Plantas normais tetraplóides foram obtidas das que germinaram.

Resumo em Inglês:

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).