The cytogenetic behavior of six of the races of Oenothera mollissima and their hybrids has been presented. Five of the races viz.-Argentina, Buenos Aires, Canelones, Montevideo and Uspallata were found to be complex-heterozygotes with _??_ 14. The sixth race viz.-Carrasco had _??_ 10, _??_ 4. In some instances there was evidence for the existence of gametic lethals, which were operative, at least, in the pollen parent. On the assumption that similarity in segmental arrangement is an indication of relationship between gene complexes, the phylogenetic relationships between races within O. mollissima have been pointed out. It has been concluded that complexes of O. mollissima. in general, are only distantly related to each other with respect to their segmental arrangements.
1) From the findings that some individuals with ovata plasm and durum genomes, having one extra chromosome of ovata as univalent in addition to the 14 durum bivalents, showed normal pollen fertility, the interrelationships between cytoplasm and fertility restoring chromosomes are discussed (diagrams). It is suggested that the fertility restoring agent does act in the somatic cells, not in the microspores. 2) Restoration of durum genomes to durum cytoplasm from ovata cytoplasm was obtained through backcrosses of partially fertile plants as pollinators to normal durum as female. The offspring having 14II at meiosis have shown normal pollen fertility. 3) When male-sterile durum were crossed with 10 Emmer wheats others than durum var. Reichenbachii, the offspring was completely male sterile, while when T. dicoccoides var. Kotschyanum was used as pollen parent all the offspring were pollen fertile showing 1IV+12II at MI.
1. The diploid number in the male species is 27 (26 autosomes plus X-chromosome). 2. The X-chromosome is always outside the group of autosomes. A distinct tendency for lagging in anaphase I is noticed in the X-chromosome. 3. The presence of large autosomes (macrochromosomes) is recorded. 4. A brief discussion on the systamatics of Pyrilla is given.
1. A three hour infra-red treatment before or (to a lesser extent) after X-raying increases the observable chromosome breaks and reunions in pollen grains of Tradescantia bracteata (Figs. 1 and 2). 2. Interpolating a heat shock between the X-rays and infra-red treat-ments does not remove, but on the contrary further enhances, the action of the infra-red rays. Thus the combined effect of heat shock and infra-red is additive. 3. The data show that one of the actions of infra-red rays and of heat shock is to favour reunion, no doubt at the expense of restitution, thus increasing apparent breakage. 4. Spectrometrically it was shown that only one per cent of the infrared rays reach the anthers through the surrounding tissues. Moreover the inside body temperature of the bud does not show any appreciable increase over its surroundings. Thus an infra-red action must be due not to a rise of temperature but to a more direct physico-chemical action.
Some attempts were made on the petiole of Mimosa pudiea to examine the microscopical structure of the epidermal system and the parenchyma of the cortex. 1) On the upper and on the side surface of the petiole, many stomatal apparatus, some glandular hairs and pointed hairs are distributed. 2) The stoma is composed of two small guard cells and the latter are again surrounded by large subsidiary cells. And just under or adjacent to the stoma, several small special cells are observed. 3) The sub-stomatal air chamber of the stomata opens the large intercellular space of the dorsal part of the cortex. This space is the schizogenous intercellular space. 4) The large spaces of the petiole open into the intercellular spaces of the primary pulvinus, but do not open into the intercellular space of the pinna-rachis. 5) In these spaces, the parenchymatous cells are arranged in longitudinal rows. These cells have chloroplasts, starch grains and small tannin vacuoles. From each tannin vacuole one or two threadlike vacuoles protrude into the large central vacuole. 6) The small tannin vacuole and the threadlike vacuole were the same characteristics. Both take chrome salts, and are stained with neutral red, chrysoidin and other basic dyes indicating that the threadlike vacuoles are mere modifications of ordinary tannin vacuoles. The threads shrink by the action of caffeine solution. 7) The threadlike vacuole of one cell has a connection with that of the neighbouring cell. These connections do not occur lengthwise, but between the cells side by side.
1. In Drosophila bifasciata, a wild species distributed widely in “transpalaearctic” regions, the correspondence between the karyotype and nine elements in the salivary gland chromosomes is discussed. 2. A composite map of the standard gene arrangement of the salivary chromosomes is drawn. 3. Descriptions of eleven different inversions detected in the salivary cells of geographic strains are given. 4. Qualitative variations of the gene arrangements from different geographical regions are preliminary investigated. We wish to express our thanks to Drs. Jean and Katsuma Dan for reading the manuscript.
1. In tetraploid hybrids between distantly related varieties of cultivated rice, such as between the Continental and Insular groups, the F1 plants generally showed relatively high fertility. However, plants with different fertilities were produced after the F2 due to segregation and the mean fertilities tended to go down with the repetition of generations. Plants showing vigorous growth tended to have high fertility. 2. In the tetraploid hybrids between distant varieties, F2 segregation ratios so far observed for several monogenic characters (phenol reaction, apiculus pigmentation, glutinous endosperm and seed coat coloration) all agreed with the autotetraploid ratios 35:1 or 20.8:1, based on the assumption of random pairing of homologous chromosomes or chromatids. 3. The F2 genotypic ratio for glutinous endosperm showed a significant deviation from the expected ratio: glutinous homozygotes and simplex heterozygotes were deficient. This deviation was found to be due, not to selective pairing of chromosomes, but to a certation in favor of non-glutinous pollen, in the same manner as in diploid hybrids. 4. It was concluded that tetraploid hybrids between distant varieties of cultivated rice have no amphidiploid-like nature, and that the variation in cultivated rice is mainly due to genic changes.
1. Inhibitory effect of low temperatures in the late autumn upon fertilization of wild insects is compensated by incubation at 25°C. 2. In the silkworm, the effect of low temperature has a definite critical point between 2.5°C and 5°C, which is related to the suppression of fertilizing capacity of the sperm remaining within the mature ovum. 3. No marked critical point is found between 2.5°C and 5°C with respect to the fertilizability of the mature ovum. In other words, the ovum can resist the inhibitory effect of low temperature fairly well, and fertilization takes place normally as long as the sperm activity is well preserved. 4. Fertilizing activity of the sperm at 2.5°C in the crosses between the same strain and those between different strains shows that the sperm activity is higher in the latter crosses than in the former crosses. 5. Fertilizing activity of the sperm held within the ooplasm of hybrids was found high too. 6. These results point out that the fertilization capacity of the sperm is dependent upon surrounding ooplasm, which is likely to substantiate the preceding observations on ovarian transplantation and favors the view that the phenomenon of heterosis is related not only to the behavior of nuclear genes but also to the ooplasm which is the field of functioning of the nuclear agencies.