1. A brief review of the taxonomic history of the genus Sorghum is presented, as well as a key to the five subgenera; Para-sorghum, Stiposorghum Eu-sorghum, Chaetosorghum and Heterosorghum. 2. The cytology of the genus is reviewed. Forty-three species, including all five subgenera, are now known. 3. Four species, S. conspicuurn, S. aethiopicum, S. niloticum, and S. timorense, are reported for the first time. All were 2n=20. 4. Both auto- and allopolyploidy is found commonly in the genus but the autopolyploids are apparently restricted to the Para and Stiposorghums. Intraspecific polyploidy is found to occur in two species, S. nitidum and S. plumosum. 5. A brief review of the geographical distribution of each subgenus and the individual species studied is given. 6. A review of the interspecific hybridization work is also given, and the need for a more systematic approach to this problem is suggested. 7. A brief discussion of the phylogenetic relationship of the five subgenera is presented, which included a survey of both the morphological and cytological information.
Chromosomes of Rattus norvegicus in spermatogonial mitosis and 1st and 2nd meiosis are illustrated by a series of photomicrographs. The following observations highlight this demonstration: 1. The Y chromosome remains positively heteropycnotic throughout the three division cycles while the X becomes positively heteropycnotic at the onset of the 1st meiosis and remains heteropycnotic until the end of the 2nd meiosis. 2. In the mitotic and the two meiotic prophases, regions of the autosomes adjacent to the kinetochore are marked by heterochromatin. At diplotene, one chiasma, as a rule, is seen to lie near the heterochromatin. 3. The X and the Y during 1st meiotic prophase are embedded in the sex vesicle. The arrangement of the X and the Y at diplotene suggests the partially homologous nature of the X and the Y. The chiasma formation between the X and the Y, however, appears to be limited to the extremely short second arms which may be euchromatic. The 1st meiotic division is reductional to the X and the Y.
A member of the Orthezia praelonga species group has 16 chromosomes in the germ line of both the male and female, and shows no apparent differential behavior between the two haploid complements in the male. In not showing a chromosomal difference between the sexes, it is unlike any other bisexual species of coccid yet studied cytologically. In most respects, spermatogenesis appears to conform to the primitive coccid pattern. Various possible modes of sex determination, derivable from the basic coccid XO system, are considered in the discussion.
Somatic chromosomes of Lepturus repens R. Br. and L. radicans A. Camus have been observed in root tip cells. The former has 2n=54 and the latter has 2n=18. The basic chromosome number of Lepturus may be 9, and all chromosomes are small (Fig. 1.). It is pointed out that Lepturus and Monerma are karyomorphologically very widely different and that l lonerzna may be a member of Pooideae, while Lepturus can be ascribed to Eragrostoideae, although the two genera are so closely related in external morphology that for a long time they were believed to be congeneric. I wish to express my cordial thanks to Dr. H. Kihara, Dr. Y. Takenaka, Dr. E. Potztal and Dr. F. A. Lilienfeld for their kindness throughout the present study. Thanks are also due to The Rockefeller Foundation who financially helped me in the trip to Ceylon and India.
Photometric determinations of DNA have been made of Feulgen-stained nuclei of kidney cells, both in culture and from sections, of three species of Old World monkeys in the family Cercopithecidae having different diploid chromosome numbers, viz: Macaca mulatta (2n=42), Erythrocebus patas (2n=54) and Cercopithecus aethiops sabaeus (2n=60). The mean diploid DNA values were found to be essentially the same for the three species. This result suggests that rearrangements in a basic chromosome set to produce chromosome number changes, rather than mechanisms such as aneuploidy or polyploidy, were involved in the evolutionary divergence of these Primate species. A certain proportion of the cells, especially in culture, do not contain normal diploid amounts of DNA. Such nuclei are interpreted as being aneuploid or polyploid. The origin and significance of such cells is discussed briefly.
Pollen tube growth in vivo of both selfings (controls) and crosses between six species of Hibiscus namely, cannabinus, sabdariffa, radiatus, lunariifolius, panduraeformis and vitifolius are reported here. From the behaviour of pollen tube study it is observed that the three species, viz., cannabinus, sabdariffa and radiatus show reciprocal receptivity of pollen germination and growth in the style indicating thereby that no stylar incompatibility is involved in these crosses. In the crosses of other three species, viz., lunariifolius, panduraeformis and vitifolius there is a definite stylar incompatibility between the species themselves as well as their crosses with other three species namely, cannabinus, sabdariffa and radiatus. In the selfed styles no germination of pollen occurs after five minutes of pollination excepting in H. radiatus where germination takes place after 10 minutes of pollination. All the pollen tubes, however, reach the base of the style within 30 to 45 minutes after pollination. In the crosses also the germination of pollen starts after five minutes excepting in the cross cannabinus×radiatus where it starts after 10 minutes of pollination. The rate of growth of pollen tubes in the self and crossmatings with different species of Hibiscus is also found to be slightly different.
1. Eye-antennal discs and cephalic complexes obtained from mature third-instar larvae (96 hours old after hatching at 25°C) of D. melanogaster were cultured in vitro in synthetic media, in order to investigate the tryptophan metabolism in the eye discs. 2. Eye-antennal discs cultured together with cephalic complexes showed in comparison with culturing the former alone more pronounced growth, differentiation and pigmentation of the eye discs. This indicates that the metamorphic hormone seems to be the most essential substance for growth, differentiation and pigmentation in the tissue culture of eye discs. 3. In a synthetic medium containing 5mg/ml L-tryptophan, the brown pigment was deposited in the eye discs of Oregon and bw after culturing for about 72 hours. In the medium containing 4mg/ml DL-kynurenine, the pigment was deposited in the eye discs of Oregon, v and bw after culturingfor about 30 hours, and in the eye discs of v bw after culturing for about 55 hours. In a medium containing 2mg/ml DL-3-hydroxykynurenine, the eye discs of Oregon, v, cn and bw deposited pigment after culturing for 5 hours, whereas the eye discs of v bw and cn bw deposited pigment after about 15 hours. 4. The amounts of pigment deposited in the eye discs of v bw and cn bw were less than those of Oregon, v, cn and bw. 5. The fact that the eye discs of Oregon deposited the brown pigment in media containing various tryptophan metabolites indicates that all enzymes related to tryptophan metabolism were present in the eye discs of the mature third-instar larvae of Oregon. 6. Smaller amounts of pigment in the eye discs of double recessive mutants, v bw and cn bw, seem to indicate that there may be either some interaction between tryptophan- and pteridine metabolism, or there may be some quantitative and qualitative difference among metamorphic hormones secreted from the brains of several strains. I wish to express my hearty thanks to Prof. H. Kikkawa for his advice and encouragement, and to Dr. Y. Kuroda for his kind guidance and criticism of this work.
In the salivary gland nucleus of Chironomus dorsalis it was found that the salivary gland chromosome was attached to the nuclear membrane. This phenomenon was seen in the nucleus of the salivary gland from the larvae in various stages of development. Chromosomes sometimes penetrated into the nuclear membrane, and spherical bodies, which looked brilliant under the phase negative contrast, were found in the vicinity of the attachment of the chromosomes. It may be supposed from these observations that this phenomenon has relation to a mechanism for transfering materials from the nucleus to the cytoplasm. I wish to express my sincere gratitude to Professor Sukeichi Fujii of Kobe University for his kind criticisms. I am also deeply indebted to Professor Kenji Nakamura of Kyoto University for his valuable suggestions.
1) The first meiotic divisions from prophase to metaphase in various species of orthopteran spermatocytes were studied by means of phase-contrast cinematography using an oil immersion lens. 2) The development of the chromosomal spindle fibers revealed by the observation on the first spermatocytes of Gastrimargus transversus as well as Patanga japonica is as follows. At the late diakinesis of these cells, near the nuclear membrane, two centrioles become visible from which both the astral rays and the presumptive chromosomal spindle fibrils radiate. The latter fibrils, not different in structure from the astral rays and radiating only towards the nucleus, are brought into contact with the nuclear membrane. The disappearance of the membrane initiates at the portions with which these fibrils are in contact. The fibrils grow into the nucleus through thus disrupted portions of the nuclear membrane and become attached to the kinetochores of the chromosomes. And it could be observed that each of the chromosomal spindle fibers was composed of a number of fibrils which were formed in above-mentioned way between the centers and the kinetochores. 3) The movement of the chromosomes towards the nuclear periphery which takes place shortly before the disappearance of the nuclear membrane and the ensuing movement towards the developing spindle were found in the first meiotic division of all the orthopteran spermatocytes studied. And the movement towards the developing spindle cannot be explained by the pushing action of the spindle fibers alone which grows from the poles to the equator in the same period, besides, other factor or factors may be concerned as well. 4) Some of the kinetochores of univalent and paired chromosomes can change their orientation from one pole to the other before their co-orientation (re-orientation). In addition, even if the co-orientation of a bivalent is completely interrupted in prometaphase, the bivalent can enter a second coorientation (re-coorientation). In the process of this second co-orientation, the chromosomal fibers which have been dissoluted to some extent might be reversibly reconstructed between the poles and the kinetochores of the bivalent.
On the basis of cytological examination, the life cycle of Streptomyces griseoflavus appears to consist of the following phases: 1) a vegetative phase (a primary mycelium) which develops after conidial germination; and 2) a sporulation phase (a secondary mycelium). Frequently the sporulation phase is the consequence of direct maturation of primary mycelium. The primary mycelium may give rise to three diverse and distinctive structures; namely, “nests”, “swollen bodies” and “clubs”. These appear to correspond to “initial cells” discussed in the literature and may represent a transition period between the vegetative and sporulation phases of growth. However, the present investigation suggests that such a transition period is not obligatory in the life cycle of Streptomyces griseoflavus. The secondary mycelium gives rise to conidia which contain single diploid or bipartite nuclei by a process of fragmentation or segmentation.
1) The heat stability of the extractable proteins of bacterial cells was investigated, using cell-free extracts prepared from the lysozyme-treated celllysates as the test material. The results obtained with a thermophilic bacterium were compared with those obtained with mesophilic bacteria, including B. subtilis, B. megaterium, Sarcina lutea, and Micrococcus lysodeikticus. 2) The thermophilic bacterial protein was found to be significantly more heat stable than the proteins of mesophilic bacteria such as B. subtilis, B. megateriuin, and Sarcina lutea, especially in the range of temperatures favorable for growth of the thermophil. Exceptionally high heat-stability was discovered in the case of Micrococcus lysodeikticus, more than two third of the protein in its original extract tolerating heat-treatment of 100°C for 10 minutes. 3) The electrophoretic and ultracentrifugal patterns of the macromolecular constituents of the bacterial cells were investigated. The heatstability of each macromolecular component was investigated by detecting the corresponding changes in the electrophoretic and ultracentrifugal patterns of the bacterial extracts after heating at 65°C, 80°C and 100°C for 10 minutes. The results obtained with the thermophil were compared with those obtained with the mesophils.