1. The present report deals with the somatic study on nine different species, namely, Hymenocallis daphne, Hymenocallis harrisiana, Hymenocallis littoralis Salisb., Hymenocallis rotata Salisb., Hymenocallis concinna, Hymenocallis senegambica Kunth & Bouche, Pancratium zeylanicum Linn., Haemanthus kalbreyeri Baker, Cooperanthes percyi Lanc. 2. Refined techniques involving the use of aesculin and coumarin have been adopted for the karyotype analysis and numerical study of chromosomes of different species investigated. 3. In addition to the presence of normal number in the somatic cells, considerable variation has been observed in the same root-tip tissue, which ranges from as low as eleven to ninety-two. 4. A discussion on the systematic position of the different genera has been made and on the basis of the present cytological data, the classification of Hutchinson is being confirmed. 5. Each genus is characterized by mostly having a constant chromosome number in all its species. Evolution within the genus, in view of the karyotype differences, has been visualized to have been brought about mainly through structural changes of chromosomes and also polyploidy. 6. In view of the chromosome number as well as their general morphology, the three genera Crinum, Pancratium and Hymenocallis have been considered to be much related, their position in the evolutionary scale being assigned as Crinum-Pancratium-Hymenocallis. 7. The significance of structural and numerical alteration of chromosomes within the same somatic tissue has been discussed, and their role in speciation in vegetatively propagated plants has been pointed out. It has been further emphasized that the balances within the tissue in such cases are maintained by the constant ratio involving the absolute amount of chromatin matter and the total amount of cytoplasm present in the tissue as a whole. 8. Discrepancies in the report of the genus Haemanthus by Satô have been considered to be due to structural alteration in chromosomes, observed in the present case within the somatic tissue. 9. An investigation on the hybrid nature of Cooperanthes, claimed to be a hybrid between Cooperia and Zephyranthes, has been carried out, but it has been emphasized that far more convincing data should be forthcoming for establishing its status as a hybrid.
1. Properties of paradichlorobenzene in causing fragmentation of chromosomes have been worked out after trials in different species of Monocotyledons as well as of Dicotyledons. Six species under Dicotyledons and ten species under Monocotyledons were used for the purpose. 2. Different species require different periods of treatment in the chemical for the breakage of their chromosomes. Dicotyledons, generally, require longer periods than the Monocotyledons. 3. The results of recovery experiments have been discussed and the potentiality of the chemical for mutagenic purposes has been pointed out. 4. In fixation schedules for chromosome analysis, a cautious application of the chemical is recommended, because if the period of treatment is prolonged over the one required, fragmentation of the chromosomes may result.
1. Roots from two lots of air-dry seeds of Vicia sativa Linn., that is, i. With twenty-four hours pre-germination soaking in tap water, and ii. Without any such pre-germination soaking were tested cytologically for the study of spontaneous fragmentation in the somatic tissue. 2. Chemicals having no property of causing fragmentation (so-called mutagenic) were used in techniques applied for the detection of fragments, whereas those chemicals having the property of causing fragmentation were used in some sets to study their accelerating or retarding effects on the fragmentation process. 3. Number of fragments noted were found to be one, two, three and even four, but in no case exceeding that number. Fragments were located during all the nuclear phases of the divisional cycle, namely, prophase, metaphase, anaphase and telophase. No significant difference in this behaviour could be noted between seeds germinated after pre-soaking and without presoaking. 4. Gradual degeneration of fragments with increase in age, occurrence of micronuclei and the fate of these fragments and nuclei have been studied and their significance discussed. 5. Data have been gathered to show that possibly the secondary constriction regions are involved in breakage. The susceptibility of secondary constriction regions to breakage has also been regarded as an indication of its chemical difference from the rest of the chromosome segments.
Somatic mitosis of Spirogyra setiformis was studied with special attention to the behaviour of a “nucleolus”. In the prophase, a “nucleolus” is transformed into fine chromonemata. Both chromonemata derived from the “nucleolus” and derived from the “Außenkern” or the nuclear part outside of the nucleolus, shift together toward the nuclear plate of the spindle. In the anaphase, about ten chromosomes are pulled out from the daughter chromosome-group toward the mitotic pole. A membrane surrounding the main daughter chromosome-group and the poleward proceeded chromosome-group, develops into nuclear membrane. The main chromosome-group swells and becomes a spherical body or a “nucleolus”. Most of the poleward proceeded chromosomes, are unravelled to fine chromonemata which exist in the “Außenkern” at resting stage. Part of the chromosome which remains without unravelling throughout the resting stage, is designated as a “Nebenkörper”.
The present paper deals with the histological and cytological observations of six male tortoiseshell cats. The four of these specimens possessed apparently sterile testes consisting of sterile seminal tubules which contained a few germ cells without any spermatogenetic activity. In the testes of two males active spermatogenesis seemed to be proceeding in a regular fashion. The chromosomes of these cats showed nothing different from those in normal cats, either in their number or in their morphology or behavior. There are 38 chromosomes in a 2n complex including an X-Y pair and 19 in a n complex. The results of the present observations have failed to demonstrate cytologically the X-Y crossing-over hypothesis postulated by Komai (1952).
Cytologically Halys dentatus and Halys sp. differ in the staining reaction of the nucleolus which is, however, formed by the heteropycnotic ends of the autosomes in both the species. It appears that the staining difference between the two is of the same nature as that of the heterochromatin which shows positive or negative reaction at different stages during the life of a particular cell. The metrical analysis of the chromosomes at metaphase I reveals that the difference in the chromosome sets of the two species is of the nature of a single homozygous deletion or reduplication in the longest pair of the chromosomes. It has further been observed that there is a continuous decrease in the total length of the monoploid genome during the successive spermatogonial generations which is also accompanied by the decrease in the area of the cell. There does not, however, appear any correlation between the two.
Styles of V. rotundifolia are uniformly thick from stigma to the ovary and one and one-half times longer than that of V. vinifera. The differences in the length of styles has nothing to do in the failure of crossing rotundifolia female (2n=40) with vinifera male (2n=38), since the pollen tubes of vinifera penetrate the entire style and in some cases the ovules of rotundifolia pistils in the duration of time as control. The absence of swelling of the ovaries even four days after cross-pollination with vinifera and secondly the abscisson of pollinated as well as non-pollinated pistils at about the same time suggests that fertilization does not occur. The complete failure of crossing, therefore, must reside in the cytoplasm of either embryo-sac or/and maternal tissue surrounding the embryo-sac.
Three plant species and one animal species have been subjected to cold treatment in order to determine whether or not the DNA content of the cells shows a reduction. The following conclusions have been drawn from this study: 1. A decrease in the amount of DNA results from cold treatment in Trillium erectum and Trillium sessile which is observable both by microscopic observations and by spectrophotometric measurements. These two species show no noticeable decrease in mitotic processes when cold treated. Tradescantia edwardsiana, which has supernumerary chromosomes, shows a slight increase in DNA which is attributed to the suppression of mitotic activity. Chortophaga viridifasciata does not show any significant change in meiosis subsequent to pachytene, and there is a systematic halving of the quantity of DNA corresponding to the divisions in meiosis. 2. There are at least two types of DNA present in Trillium erectum and Trillium sessile, a stable type associated with gene-bearing regions and a more labile type found in heterochromatic regions. The decrease of DNA caused by cold treatment appears to be due to a deficiency of this labile fraction of DNA. 3. Cold treatment of chromosomes results in manifestations remarkably similar to effects from other physical and chemical agents, such as 5-aminouracil and an ultraviolet microbeam. 4. The changes in quantity of DNA due to cold treatment occur only in selected plants having large heterochromatic regions and ones which are able to continue mitotic processes despite severe alteration of the environment. For these reasons, it is believed that reduction of DNA content as shown in this study does not invalidate the usefulness of the concept of constancy of DNA as currently advocated by Swift and others.
1) Der ganze Verlauf vom Hervorkommen der ersten Archesporzelle bis zur Bildung der gereiften Pollinium bei Albizzia glabrior var. speciosa wurde an jeder Zellgeneration erforscht. 2) Eine, und nie zwei, der Periblemzellen des jungen Staubbeutels bildet sich zur ersten Archesporzelle um. 3) Direkt vor der Meiosis, findet man beständig zwei Archesporzellen in jedem Staubbeutelfach. Sie vollziehen sich die letzte premeiotische Teilung, um vier P. M. Z. hervorzubringen. 4) Die ein Pollinium bildenden 16 Pollen führen die ersten Pollenkorn-teilung nicht gleichzeitig sondern selbständig aus. 5) Ein Vorschlag in bezug auf die Einheit der Organisation der Pollen war vorgesehen. Herrn Prof. Dr. Miduno danke ich herzlich für die Überlassung des Themas und für seine Leitung am Fortgang der Arbeit. In gleicherweise danke ich Herrn Prof. J. Tanaka für die freundlichen Hilfe für das deutsche Manuskript.