1. Work relating to the nuclear cytology of Rhinanthus is reviewed. 2. Illustrated chromosome counts of R. minor from a number of British localities indicate a bimodal diploid complement of 14 larger plus 8 smaller chromosomes: i.e. 2n=22. 3. A similar bimodal complement from R. serotinus is also illustrated, whilst investigations of R. hirsutus and R. sp. cf. R. angustifolius showed the 14 larger chromosomes and an intermediate number of smaller ones. 4. It is concluded from the results presented on R. minor and from earlier work of Fagerlind and Wulff on the genus that the basic number (x) for Rhinanthus is 11 and not 7 as has been suggested in much of the literature. 5. The prochromosomal resting nucleus of Rhinanthus and the mitotic cycle are illustrated and discussed. 6. The possible future application of studies on the resting nucleus of the Scrophulariaceae to the elucidation of the phylogeny of the semi-parasitic group is mentioned.
1. The various Golgi techniques have been applied on the ageing spinal neurones of birds (Gallus gallus domesticus, Columba livia intermedia) and mammals (Rattus norvegicus, Oryctolagus cuniculus). 2. The so-called Golgi apparatus in the adult neurones which appears as a network of convoluted argentophil and osmiophil strands and irregular masses after the application of the Golgi techniques, comes into existence by the deposition of reduced silver or osmium on the basiphil masses of Nissl substance and closely associated canalicular spaces which can be observed in living cells under the phase contrast microscope. 3. The absence of the reticular Golgi apparatus in the neurones of the young animals has been explained to be due to the absence of elongate canalicular spaces and patchy Nissl substance. 4. The lipid bodies or the mitochondria are not concerned in any way with the formation of these networks, except that a few of them lying in close vicinity of the basiphil masses may be accidently associated with them during the impregnation process.
1. The ‘Golgi apparatus’ in the invertebrate neurones is formed by a deposition of reduced osmium or silver on the various types of lipid spheroids which are in the form of granules, crescents and binary spheroids. 2. The ‘crescents’ or ‘dictyosomes’ are formed as a result of contraction caused by drastic fixation of the homogeneous bodies and there is no dictyosomal Golgi apparatus separate from and independent of the lipid spheroids. 3. An over impregnation of the material leads to blackening of the basiphil granular Nissl substance in the cytoplasm, which gives the appearance of a cloud.
The paper describes the cytological behavior of F1 cross (Phaseolus lunatus L. var. Fordhook×Phaseolus polystachyus L.) under Utah environmental conditions. The germination behavior of parental and hybrid plants was studied. The flower buds were fixed in propiono-alcohol and were smeared in propiono-carmine. The meiotic behavior of chromosomes, as seen from the dividing pollen mother cells, was normal in parent species. A number of meiotic irregularities such as non-pairing of chromosomes, early disjunction, the presence of bridges and laggards with unequal distribution of chromosomes at anaphase, and polyspory were recorded from hybrid plants. The meiotic irregularities in general seem to be responsible for high pollen sterility in F1 hybrid plants.
1. Division synchronization being taken as criterion, different cases of tapetum are classified into three types: 1) synchronized type, 2) asynchronized type and 3) intermediate type. 3). In the synchronized type second division takes place and further divisions may also occur. The final form is mostly of the periplasmodium type, with some few exceptions. 3. In the asynchronized type, the first division takes place, but no further divisions. The final form is exclusively of the secretion type. 4. In the intermediate type, two subtypes are distinguishable. In subtype 1, second division takes place as in the synchronized type, and in subtype 2, it does not as in the asynchronized type. In the intermediate type, both periplasmodium and secretion types are observed, and in subtype 1, the periplasmodium type case is found in a greater frequency than the secretion type case, and in subtype 2 the two cases are found in the reversed ratio. 5. It is concluded that the tapetum which is of sporogenous cell complex origin would be the product of counteractions between the original character retaining tendencies and the tendencies converting toward somatic nature. The apparent two types are connected by intermediate cases to form a whole, so as to indicate that any classification should be artificial.
Like ‘Chinese Spring’, ‘Holdfast’ is a hexaploid wheat (2n=42), and can be used in building a set of monosomic lines just as conveniently, for meiosis in it is not as stable as is to be expected in a stable commercial variety. Monosomics are regularly thrown out as a result of meiotic instability and as such several lines can be built up within comparatively a short time. In this paper eleven apparently different monosomic lines have been studied cytologically. The morphological features of the individual monosomes have been described and an attempt has been made to compare and identify these with the chromosomes in ‘Chinese Spring’. Meiotic irregularities have been described in these monosomic lines and at first appear substantial and significant but when they are assessed against the background of ‘Holdfast’ these irregularities no longer seem to be of much significance. However, it may be said that all these monosomic lines are not similar in the type and to the extent to which they exhibit aberrant features in meiosis. Some lines produce appreciably more aberrant features than others whereas some seem to be even more regular than the parent variety itself.
In der Mitose bei Vicia Pannònica konnte bereits in einem charakteristischen Teilungsabschnitt der Metaphase morphologisch eine Teilung der Spalthälften nachgewiesen werden, die in den folgenden Teilungsstadien noch deutlicher hervortritt.
Meiotic chromosome behavior in four intergeneric hybrids of Neofinetia falcata Hu was investigated. N. falcata×Vanda lamellata Ldl., N. falcata×Ascocentrum miniatum Schltr., and N. falcata×Ascocentrum ampullaceum Schltr. showed 19-17 bivalent chromosomes with means of about 18.6 at metaphase I, indicating a strong homology of the parental genomes, whereas N. falcata×Aerides jarckianum Schltr. exhibited 10-2 bivalents with a mean of 6.1, indicating a relatively poor homology of the parental genomes. On the basis of chromosomal affinity, Neofinetia is very closely related to Ascocentrum and strap-leaved Vanda and more distantly related to Aerides.
Cytological observations were made in maize on diakinesis configurations from crosses between interchanges in which the same two chromosomes were involved but their break positions differed. Seventeen combinations produced by intercrossing seven different interchanges between chromosomes 2 and 6, two between 3 and 6, and two between 6 and 9 were used. Diakinesis configurations of the four interchanged chromosomes in the intercrosses of different types were as follows: In type 1a in which both breaks were in opposite arms in the two chromosomes and the interchanged segments were long enough, there was a high frequency of two ‘pairs’ (56, 70 and 76% for the three studied). In type 1a, when an interchanged end segment was a satellite, only associations of four were formed. In type 1b with both breaks in opposite arms in one chromosome and in the same arm in the other chromosome, all or nearly all were associations of four. In group 2 with breaks in both chromosomes in the same arm, a high frequency or all were two ‘pairs’. The type 1b intercrosses can be distinguished from the other two intercross types based on examination at diakinesis alone, provided no interchange segment is extremely short. Decreased sterility will distinguish certain of those in group 2 from those in type 1a. The high frequency of ‘pairs’ in type 1a and group 2 as well as the high frequency of associations of four in type 1b can be ascribed to the preferential initiation of pairing in the homologous ends of chromosomes rather than in the intercalary segments. In these same intercross combinations, pairing may occur simultaneously in intercalary as well as in end segments resulting in an association of the four chromosomes. ‘Pairs’ were never observed in which only the intercalary segments were paired.
DNA amount and concentration per nucleus of root tip nuclei of Vicia faba were measured by cytophotometry. DNA amount and concentration per nucleus differed with the distance from apex and it was seen that there existed three classes in DNA amount per nucleus. Rate of DNA synthesis was discussed related to DNA concentration. Low DNA amount per nucleus seen in apical initials required further study. The author wishes to express his sincere thanks to Prof. N. Sinke of Kyoto University for valuable suggestion and criticism throughout this study.
By the Macallum's modified method and Mallory's staining, the migration of potassium in the Mimosa petiole is observable. Before receiving the stimulus the potassium salts appeared in lacunal parenchyma, phloem parenchyma, xylem parenchyma and protoxylem respectively. On the contrary, after receiving the stimulus the potassium salts appeared in the intercellular spaces and/or sieve tubes. Fig. 1 is the schema which is summarized from the data of the cytochemical experiment concerning potassium migration. In the fixed material, there are still notable differences between the two. In the tissue-cells of xylem parenchyma and protoxylem parenchyma before stimulus is given, the protoplast is observed to be in colloidal mass. After receiving the stimulus the contents of the tissue-cells have disappeared.
The chromosome number of Hemianax ephippiger (Burmeister) has been recorded for the first time. The diploid chromosome number in both males and females is 14. The sex-determing mechanism is of XX:XY type. The X-chromosome is the largest of all and in the spermatogonial metaphase plate, it is markedly bent. The Y-chromosome is medium sized and rodshaped. Metrical study of fifteen metaphase I plates reveals two very long, ten medium and two very short chromosomes. The m-chromosomes are the smallest of all. The X- and Y-chromosomes both possess euchromatic regions which form pairing segments at meiosis. Anaphase I results in two types of daughter nuclei, one with X- and the other with Y-chromosome. Anaphase II is equational for the sex and all other chromosomes.