1) The distribution of frequencies of the chromosome number contained in the pollen grains of the hybrid plant (n=16) of A. Cepa×A. fistulosum was investigated. According to the writer's observations for a two year period, over 70 percents of all the pollen has the normal chromosome number (n=8) and ca. 20 percents, n=9. This ratio occurred annually. 2) In cases with chromosomes above the normal, the distribution of frequencies of chromosome number in this material coincides with Poisson distribution, regardless of the observed frequencies of pollen containing chromosomes less than one genome, which seems to perish for the mcst part prior to arriving at the first pollen mitosis. This hybrid plant multiplys mainly by bulbs, seed production being of rare occurrence. 3) The pollen with a SAT-chromosome derived from A. fistulosum and with that from A. Cepa amounted to about half and half in the normal metaphase plates of this hybrid plant.
1. In order to gain information as to how the change of characters due to the doubing of chromosomes differs in rate with the variety, tetraploid strains induced from 74 different varieties of Eastern Asia were grown in a paddy field from the 2nd to the 9th generations, and various morphological and physiological characters were measured. 2. Fertility varied from ca. 1% to 55% (in the average of 3 years) among tetraploid varieties, and varieties having high fertilities were relatively large in number in “Continental” variety group. The percentage of good pollen varied from ca. 55% to 95% among varieties. It was always higher than seed fertility, but was found to correlate with the latter. 3. The lengths of stoma cell in both diploid and tetraploid, as well as its 4x/2x ratio were recognized to be different with the variety. The 4x/2x ratio varied from 1.15 to 1.50 among varieties, and varieties having small stomata in diploid tended generally to be large in the 4x/2x ratio. A similar tendency was found also in the length of unhulled grain. 4. Generally, the height of plant, the number of grains per ear and the number or ears per plant decrease, and the lengths of ear and awn increase with the doubling of chromosomes. The 4x/2x ratios in the height of plant, the length of ear and the number of grains per ear were found to correlate with one another, but no significant correlation was found between these and the 4x/2x ratio in stoma cell length, nor between these and fertility. 5. The response to day-length seemed to remain unchanged after the doubling of chromosomes. While in tetraploid varieties the date of heading was approximately the same as the date in corresponding diploid varieties, the difference between tetraploid and diploid in heading date was a character peculiar to the variety, and varied from -4 days (4x is 4 days earlier than 2x) to 12 days. In tetraploid, further, heading was incomplete generally, and the distance between the neck of ear and the node (the joint of leafsheath and leaf blade) of the uppermost leaf was found to be different with the variety. 6. Germinating capacity and germinating speed of seed in tetraploid varieties were generally lower than those in corresponding diploid varieties. Germinating capacity varied from 45% to 95% among varieties, and the higher the germinating speed, the higher was the germinating capacity. Continental varieties were generally high in germinating speed in tetraploid, in the same manner as in diploid, and accordingly high in germinating capacity. 7. The resistance to pottasium chlorate seemed not to be modified by the doubling of chromosomes. Low temperature resistance seemed to be unchanged or to become slightly higher. Drought resistance measured by Mimosa method became lower by the doubling of chromosomes. In anyone of these, however, varietal characteristics in diploid varieties were distinctly seen in tetraploid varieties. Intervarietal variations of these characters were similar with those found in diploid.
The microstructure of the salivary gland chromosome of Diptera has been investigated by means of the electron microscope. A 45% butyric acid and a butyric acid and acetic acid mixture (equivalent volume) have been used for fixing. The chromofilaments and euchromatin bands are not so well fixed and extensible, as with acetic acid.
Nucleoli of the larval salivary gland of Drosophila melanogaster, when fixed with a 45% acetic acid, squashed, and examined in the electron microscope, showed homogeneous structure, ranging from opaque to transparent states to electron beams.
1. The present investigation is concerned with a detailed account of chromosome morphology in the Genus Gymnaster, a member of the Family Compositae. 2. The karyotype of the Section Homolepis differs sharply from that of the Section Crassifolium. 3. The close resemblance of the karyotypes of G. pygmaeus to those of G. Savatieri supports the phylogenetic relationships of the two species. 4. Two triploids and a tetraploid of Gymnaster studied are, karyotypically, all autopolyploids. 5. The chromosome numbers and the karyotype formulas are as follows; Sect. Homolepis G. Pygmaeus Kitamura 2x K(2n)=18=2csAsm+2B1sm+2B2m+2Csm+4D1sm+2D2m+4Esm G. Savatieri Kitamura 2x K(2n)=18=2csAsm+2B1sm+4B2sm+4C1sm+2C2m+2Dsm+2Esm G. Savatieri Kitamura 3x K(2n)=27=3csAsm+3B1sm+6B2sm+6C1sm+3C2m+3Dsm+3Esm G. Savatieri Kitamura 4x K(2n)=36=4csAsm+4B1sm+8B2sm+8C1sm+4G2m+4Dsm+4Esm G. Savatieri Kitamura (Aster Savatieri var. hortorum Makino) 2x K(2n)=18=2csAsm+2B1sm+4B2sm+4C1472sm+2C2m+2Dsm+2Esm G. Savatieri Kitamura (A. Savatzer var. hortorum Makino) 3x K(2n)=27=3csAsm+3B1sm+6B2sm+6C1sm+3G2m+3Dsm+3Esm Sect. Crassifolium G. koraiensis Kitamura K(2n)=144=8A1st+6A2sm+14B1sm+12B2m+6C1st+72C2sm+6D1st+14D2m+6Esm