1. A detailed cytological study of millets like Eleusine coracana, Setaria italica, Panicum miliaceum, Panicum cruss-galli and Pennisetum typloideum with their closely allied species was taken up for the first time. Differences in chromosome numbers already reported in some species have been found. 2. Mitosis and meiosis in all the species is described. Analysis of somatic chromosomes has been done. 3. Pairing at diakinesis was found to be by means of chiasmata. Chiasmafrequency was analysed in the pollen mother cells of E. coracana, E. indica, E. verticillata and D. aegepticum. It was found that with the advancement of meiosis the total number of chiasmata decreases but the proportion of total chiasmata that are terminal increases from diakinesis to metaphase. 4. Secondary pairing occurs amongst the bivalents at metaphase I or univalents at metaphase II. The maximum association has been studied in millets. No connections which have been reported to arise by fusion at pachytene and causing the secondary association amongst the chromosomes have ever been observed. 5. Two original basic numbers have been found out by means of secondary association studies in millets. 6. Linear micro-morphological studies in these genera have been persued and effect of polyploidy has been noticed in some respects. 7. It was obvious that alto-polyploidy and the establishment of a secondary basic number are important factors in evolution. 8. Origin of millets has been determined with details and hypothesis is advanced showing a monophyletic origin of family Gramineae. In the origin of millets and their allied species included here, polyploidy, aneuploidy and structural changes have played important role at various stages. 9. Chromosome pairing at meiosis in Panicum and Pennisetum have been discussed. These genera have autoplolyploid species. 10. Fertility of millets and their allied species has been studied and the causes of varying fertility in among the members of this group has been found out.
In this paper, sixth in the series ‘Studies on Insect Spermatogenesis’ observations on the cytoplasmic inclusions in the living male germ cells of Pyrilla sp. and Dysdercus cingulatus have been presented. The mitochondria appear as granules and delicate fibrils in the spermatogonium of Pyrilla sp. and Dysdercus cingulatus respectively. Some of the mitochondrial granules align to form filaments of low phase-change in the spermatocyte of Pyrilla sp. Some of the filamentous mitochondria bend to form ovals or rings or vesicles during meiotic stages. The mitochondrial nebenkern, to start with, is ‘vacuolar’ in Pyrilla sp. and later reveals an ‘onion like’ pattern lacking in Dysdercus cingulatus. The ‘central substance’ is conspicuous by its absence in both the species. ‘Chondriokinesis’ without fragmentation of the individual mitochondria has been recorded in Pyrilla sp., and D. cingulatus. During spermateleosis the fusion of the Golgi bodies result in the formation of the acroblast to which is later on associated the acrosomal vesicle. This vesicle condenses to form the acrosome, there being no acrosomal granule in both the species.
1) Durch Keimung von Samen tetraploider Tomaten auf Colchicin-Agar wurden 6 oktoploide Pflanzen und 2 Organismen mit Chromosomenzahlen zwischen der tetra- nnd oktoploiden Valenz erhalten und nach morphologischen und cytologischen Gesichtspunkten ausgewertet. Eine Pflanze besaβ einen 16-ploiden Hauptsproß und oktoploide Seitensprosse. 2) Für Spaltöffnungen und Stengeldrüsen wurde eine direkte Proportionalität zwischen Polyploidiegrad und Größe dieser Organe gefunden. Die Mittelwerte der Stomatalängen von 2n, 4n, 7n, 8n und>8n verhalten sich wie 1: 1, 2: 1, 6: 1, 7: 2, 0. Die entsprechenden Werte der Durchmesser der Stengeldrüsen diploider, tetra-, okto- und hyperoktoploider Tomaten liegen bei 1: 1, 2: 1, 4: 1, 5. 3) In den Blüten der bearbeiteten hochpolyploiden Tomaten traten-vornehmlich im Gynaeceum-starke Reduktionserscheinungen auf. Trotz reichlichen Blütenansatzes kam keine Fruchtbildung zustande. 4) In der meiotischen Prophase oktoploider Pflanzen konnte die Bildung von Hexa- und Oktovalenten im Pachytän unmittelbar beobachtet werden. Neben Partnerwechselfiguren trat im Pachytän zwischen den 4 homologen Bivalenten eines jeden Chromosomentypus häufig das Phänomen der Sekundärpaarung in Erscheinung. 5) In späteren meiotischen Entwicklungsstadien traten vielfältige meiotische Unregelmäßigkeiten, darunter Spindelstörungen, auf. Sie führten zur Bildung einer hohen Gonenzahl je PMZ. Die Folge davon war eine vollständige Pollensterilität der betreffenden Antheren. In einigen Antheren okto- und hypo-oktoploider Pflanzen wurde demgegenüber ein völlig störungsfreier meiotischer Stadienablauf beobachtet. Die Arbeit wurde mit Unterstützung der Deutschen Forschungsgemeinschaft durchgeführt. Meiner Mitarbeiterin, Frl. Dr. N. Peters, danke ich für ihre Mitwirkung bei der mühevollen Erzeugung der hochpolyploiden Versuchspflanzen. Auch Herrn Gartenmeister H. Kawaletz bin ich für die sorgsame Pflege und Aufzucht der Pflanzen zu Dank verpflichtet.
1. A cytological investigation of five different species and varieties of the genus Mentha have been carried out. Their chromosome numbers noted here are as follows: i) Mentha viridis Linn. var. I 2n=32 ii) Mentha viridis Linn. var. II 2n=48 iii) M. piperita Linn. var. I 2n=72 iv) M. piperita Linn. var. II n=66 v) M. arvensis Linn. 2n=90 2. Karyotype analysis in detail has been performed in four species and varieties. Meiosis has been worked out in M. viridis var. I and M. piperita var. II. 3. It has been shown that each species and variety has got a karyotype, characteristic of its own. This fact indicates that evolution has been associated with a considerable degree of structural changes of chromosomes in them. 4. Role of polyploidy in speciation in this genus has been emphasized in view of the present and the previous data available on this aspect in the different species. Six has been considered as the possible basic number of chromosomes, from which all the euploid and aneuploid series have evolved. 5. Early literature as well as the present records show that in species of this genus, a large number of chromosomal biotypes occur. The importance of analysis of these biotypes from a cyto-ecological standpoint has been emphasized. 6. Variation in chromosome number in the same somatic tissue and the ineffective method of sexual reproduction have been pointed out as responsible for the origin of chromosomal biotypes or individuals with different chromosome numbers. Their role in speciation as an additional means is obvious. In conclusion, the authors wish to express their sincere thanks to Dr. K. P. Biswas, Director in charge, Medicinal Plants Scheme, Government of West Bengal, for giving us all facilities to collect different wild and cultivated species of Mentha at Rongo, Darjeeling.
Amitosis is recorded for Euglena acus, Euglena spirogyra and Euglena viridis, occurring only in biphasic culture. The process is a nuclear fragmentation not connected with reproduction, the product being a binucleate cell. The binucleate cell is capable of subsequent mitosis in Euglena acus and Euglena spirogyra, the half-nuclei dividing simultaneously. Cell cleavage following this mitosis produces two binucleate cells. Rare miscleavage results in cells with one half-nucleus (approximately half the specific chromosome complement) and with three half-nuclei (one-and-a-half times the specific chromosome complement). These types of cells are viable and their progeny retain the cytological characteristics of the species.
The euploid number of Saccharum officinarum L. is 80. By crossing noble cane variety vellai (2n=80) to Sclerostachya fusca A. Camus (2n=30), and by repeated back-crossing to the recurrent male parent, the chromosomes of sugarcane will be halved in each successive back-cross generation. Till finally, in the third back-cross generation only 10 sugarcane chromosomes are left in the hybrid along with 30 Sclerostachya-Narenga chromosomes. The third back-crossing was done in Taiwan. Narenga Porphyrocoma (Hance) Bor (2n=30) was used instead of Sclerostachya. SG310/6 (BC1) was found to have 72 chromosomes, 42 of which belong to sugarcane, the other 30 to Sclerostachya. It was obtained by back-crossing F1 hybrid to Sclerostachya. Of PMC's examined, many had 36 bivalents showing complete autosyndesis. The larger closed-type bivalents of Sclerostachya can be easily distinguished from the smaller open-type ones of sugarcane. One or two tetravalents were formed by the sugarcane chromosomes. In the second back-cross generation, clone SG363/4 was found to have 50 chromosomes. In majority of the cases, 25 bivalents were found. Again it showed complete autosyndesis. One sugarcane tetravalent was found sometimes. In the third back-cross generation, Narenga was used. 14 out of 15 plants were found to have 40 chromosomes. The other had 63. There was almost perfect pairing between the chromosomes of Sclerostachya and Narenga forming 15 closed type bivalents. The 10 sugarcane chromosomes remained either as univalents or as 1-4 open type bivalents. As many as 4 trivalents were found. It showed that 4 sugarcane chromosomes were partially homologous with 4 Sclerostuchya-Narenga chromosomes. Sometimes, two tetravalents were found. There were found to be composed of two sugarcane and two Sclerostachya-Narenga chromosomes. From these, it is conjectured that the 10 sugarcane chromosomes are probably made up of two sets of 5. Four chromosomes of each set are partially homologous to one another. At least 4 chromosomes of one set of 5 of one species are partially homologous to 4 of those from either Sclerostachya or Narenga. Initial hybridization between two unidentified species with n=5 each leading to segmental allopolyploidy, and followed by two successive autopolyploidization, have probably resulted in the origin of S. officinarum with 80 chromosomes.
1. In the egg of oyster (Gryphaea gigas (Thunberg)), there are two axes showing metabolic gradient, e.g. KP-axis and egg-axis. The former can be easily detected in the unfertilized egg and the latter in the fertilized one. 2. Karyosome changes its position by turning itself around plasmosome and faces to animal pole without fail after the sperm enters into the egg.
Bulbs and rhizomes of Nothoscordum fragrans, Haemanthus kalbreyeri, Zephyranthes mesochloa, Colocasia antiquorum, Zingiber officinale and Curcuma amada were irradiated at dosages of 250r and 500r, and the effect of irradiation was noted. 2. After forty-eight hours following treatment, heavy fragmentation, formation of micronuclei, structural alteration of chromosomes, lagging, etc. were observed in a large number of cases. 3. Frequency of fragments were found to be higher in treatment with 500r than with 250r dosage. This shows that the cells at different phages of interkinetic condition, in these species, become differentially affected following irradiation. This is in contrast to the previous report obtained with bulbs of Allium cepa, where all the interkinetic cells were found to be homogeneous as regards their response to irradiation is concerned. 4. It has been suggested that at the time of treatment, certain resting cells were lying at the last phase of interkinetic condition, that is, in a state just prior to germination. The enzymatic activity of these cells, necessary for germination, was completed at the time of treatment and so their germination capacity was not inhibited. In other young resting cells, however, the germination capacity was checked temporarily. 5. Fragments were found to be persisting after several days following irradiation. In Nothoscordum fragrans, fragments persisted even upto 2496 hours or one hundred and four days. Instead of assuming that fragments can remain ununited for such a long period, it has been suggested that possibly these fragments have passed through several cell generations, being included at random in the daughter cells and are on their way to degeneration.
The effects of Sarkomycin and Carzinophilin were investigated in vitro on normal rat fibroblasts and on methylcholanthrene-induced spindle cell sarcoma by means of customary cytochemical and cytological staining methods. The abnormalities induced in cultures by Sarkomycin are: 1) the loss of the substance, probably RNA, from the cytoplasm, chromatin and nucleolus, and 2) stickiness and coalescence of metaphasic chromosomes and anaphasic bridges. The treatment of cultures with Carzinophilin induces: 1) elimination of chromatin from the nucleus, 2) partial agglutination of chromatin, 3) condensation of the nuclear substance into respective nucleic acid components, and 4) fragmentation, slendering and translocation of chromosomes. Considered from the cytochemical viewpoint, it is probable that these abnormalities may be caused by the dissociation of RNA-DNA complex in the nucleus induced by the agent. In general effects of the two agents applied, rat fibroblasts respond more severely at relatively high concentrations than methylcholanthrene-induced spindle cell sarcoma, while the relation is reverse at low concentrations. It was shown that small and round cells containing a tiny nucleolus have remained alive unaffected by the agent. Phase microscopy studies in vitro furnished evidence that they are capable of proliferation and seem able to originate a regrowth of tissues.
1. The chiasmata frequency and terminalisation coefficient have been studied in S. nielongena L. varieties purple long, white bunchy, white round, insanurn, green oval, purple oval, and first generation cross XA of purple long×white bunchy. The chiasmata frequency varied between 0.77 to 1.37, the terminalization coefficient between 0.63 to 0.98. The respective figures with cross XA are 1.36 and 1.16. 2. The chiasmata has been found to be located in the less stained or achromatic regions also of the bivalents. 3. Though the overall chiasmata frequency in these varieties is very low, it has been interpreted that the greater the number of medianly constricted chromosomes, the higher is the chiasmata frequency.