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SUMMARYOnion root meristems are a frequently used material for the study of cell cycle and the effects of several treatments. For such works as many enviromental factors (light, temperature, aeration,…) as possible must be controlled.In this paper we studied the effect of aeration at two different temperatures, 15°C and 25°C. In the experiments carried out at each temperature and with aeration we obtained very similar mitotic indices (about 13%).In bulbs whose roots were grown into nonaerated water, but renewed every day, we obtained different results: at 15°C the mitotic index was 12.4% and at 25°C the mitotic idex was 9.7%.By using a synchronous binucleate population, induced by 1-hour treatment of caffeine, we demonstrated the necessity for aeration. In the experiments at 15°C, the B-Interphase is 10% longer in the nonaerated roots, and we also observed a desynchronization of the binucleate population. In the experiments at 25°C the effects of non-aeration on the cell cycle were still more drastic. The...

SUMMARYThe paper describes two morphologically distinct forms of Pluchea lanceolata occurring at Agra and the surrounding areas. This morphological diversity is not associated with any difference in the chromosome number and the karyotype. All plants invariably have n = 10 and 2 n = 20. This is the first report on the chromosome number of the plant. Meiosis is normal and results in the formation of viable pollen grains which are shed at the 3 celled stage.

SUMMARYFive East Himalayan varieties of Narcissus tazetta L. were investigated, namely: 1. N. tazetta var. « chastity » (2n = 30).2. N. tazetta var. « ponterius » (2n = 14).3. N. tazetta var. « paper white » (2n = 32).4. N. tazetta var. « cheerfulness » (2n = 24).5. N. tazetta var. « king daffodil » (2n = 28).A thorough karyotype analysis been performed of all these types. The importance of both structural and numerical alterations of chromosomes in the evolution of species has been pointed out.The occurrence of 2 n = 14 in variety » ponterius » of N. tazetta, so far not recorded in this species, brings it closer to the other species of Narcissus.Inconstancy in chromosome complements in the somatic tissue is present and as such, the role of somatic mutation in speciation has been emphasized.

SUMMARYIn the present paper the autor reports a chromosome number of 2 n = 48 and on the morphology of chromosomes in an allopolyploid species of Allium strictum Schrad.

SUMMARYThe paper describes the activation of the ovaries of Petunia hybrida on 3 levels: changes of the fresh and dry weight, the protein, amino acids and RNA content, the changes of the polyribosome profiles and the protein synthesis in vivo with the polysomal fraction of different developmental stages after pollination. The activation of the ovary after pollination occurs before fertilization takes place and starts with the carpels and the placenta.

SUMMARY1. Several methods for relating the volumes of individual nuclei to their relative interphase stage have been applied to rapidly proliferating cells of the cortex in root tips of broad bean (Vicia faba). The methods are based upon analysis of the frequency with which particular volume classes appear within a population of nuclei. Presuming random sampling of a particular homogeneous population, it is possible and convenient to relate the volume of an individual nucleus to its age in relative interphase time by using the geometric mean volume and standard deviation of the sampled population to locate a straight line on probability paper. This graph can then be used to estimate the relative interphase time for any given nuclear volume in the population.2. In cases of heterogeneous populations of nuclei, as found for cells of bean root meristems, synthetically active cells can be distinguished from inactive or quiescent cells by means of isotopic labeling. The individual quiescent cells which occur sp...

SUMMARYThe paper deals with the mutual relation of the nucleole in sex differentiation in various sex forms of hemp (Cannabis sativa L.). The genotype divergencies of the different sex forms are expressed in the size of the nucleoles both in pollen mother cells as also in the nucleoles of young pollen grains. Results of the measurement were statistically evaluated by means of the t- test and analysis of variation. The fact that the difference in genotype is more evident in the size of the nucleoles (the differences are statistically significant) than in the size of the cell nuclei seems to prove that the nucleole in all probablity has a certain influence on the sex differentiation.

SUMMARYIn the present paper the author reports about the new karyotype in Allium porrum L. cultivated in Czechoslovakia. Comparing this new karyotype with those ones, which were published by other authors, it appears, that the difference in karyotypes of the same species cultivated in various countries is a result of chromosome mutations.

SUMMARYThe present paper deals with the cytology including karyotype analysis of eight species and varieties of Begonia, viz. B. paupercula King, (2 n = 22); B. rex Putz., (var. I), (2 n = 22); B. rex Putz. (var. II), (2 n = 32); B. rex Putz. (var. III), (2 n = 34); B. malabarica Lam., 2 n = 28); B. laciniata Roxb. (var. I), (2 n = 20); B. laciniata Roxb. (var. II), (2 n = 22); B. sp. (unidentified), (2 n = 28). In addition to these two varieties B. gigantea Wall., and two varieties of B. semperflorens, were observed. One of the former two varieties showed 2 n = 28, 32 and 34 chromosomes and in another 2 n = 40 and 42 chromosomes were counted in the somatic tissue and the latter in meiosis showed 40 to 46 chromosomes. The implications of such aneuploid numbers have been pointed out.The chromosomes are graded and in all the different species and varieties taken together with their general morphological features can be divided into eleven distinct types.Variation in addition to normal chromosome number has ...

SUMMARYIn a research programme on the karyological aspects of evolution in Primates the author in the present paper shows the results of a morphometric comparative analysis between the chromosomes of Man and the Anthropoid Apes.The chromosome number in the three genera of Apes (Gorilla, Pan and Pongo) in the somatic mitosis is always 48.The average lengths in μ of the karyotypes analysed in detail are as follows:Homo 93,7 ±19,3Pan 94,1 ± 9,1Pongo 83,6 ±11,4The comparative study of each single chromosome showed the similarity in dimension and morphology among some chromosomes of the various species.The sex chromosomes were studied from a comparative point of view. The Y chromosome is, in every case, one of the smallest of the set. While in Man, Chimpanzee and Gorilla it appears to be eucromatic along its entire length, in Orang-utan it has a big achromatic portion in its small arm. The position of the centromere is submetacentric in Pan, Homo and Pongo.The X cromosome seems to be one of the largest of the ...

SUMMARYThis paper reports chromosomal changes induced by a gregarine in the parasitized caeca cells of Trichosia sp. The chromosomes of the host cells grow to abnormal sizes and present constrictions and breaks. The polytene chromosomes dissociate producing polyploid nuclei. There are also differential effects on the autosomes and X-chromosome. The system host cell- gregarine here reported is very favorable for studies on the regulation of chromosome metabolism as well as for the understanding of chromosomal effects of pathological agents.

SUMMARYThe paper presents the first part of the study made on taxon Sternbergia colchiciflora W.K. var. dalmatica Rchb. in Yugoslavia. The number and the morphology of chromosomes of the taxon are reported here. All the chromosomes (2n=20) were found to be submetacentric. The length of the chromosomes investigated varies from 13,67 μ to 4,76 μ. The evidence collected is given in a Table and 4 figures.

SUMMARYThe paper describes the effect 24 hours of action of laurylalcohol upon cell division in roots of Vicia faba. Simultaneously reversibility after 12 hours of action was observed. The results of cytological studies indicate that: 1. The mitotic indices are reversely proportional to the duration of the treatment with laurylalcohol.2. Laurylalcohol causes the formation of various mitotic cytomixis and chromosomal disturbances (aberrations) of which the formation of micronuclei is most characteristic.

ADDENDUMThe present paper was in proof when two other examples of diffuse centromeres or polycentric chromosomes were reported in the very recent literature, again in the class of Insecta (orders of Anoplura and Mallophaga).K. Bayreuther [1955, « Holokinetische Chromosomen bei Haematopinus suis (Anoplura, Haematopinldae »), Chromosoma 7: 260–270, 1955] observed the diffuse centromere during an investigation of the spermatogenesis of Haematopinus suis, n = 5, (class Insecta, order Anoplura). By X-rays treatment Bayreutheb obtained proof that the regular mitotic cycle takes place for chromosome fragments induced by the irradiation. Meiosis probably follows the post-reductional scheme, however the lack of any heteromorphous bivalent and the uniform tetrapartite structure of all five bivalents preclude certainty regarding the actual occurrence of post-reduction.A type of spermatogenesis very similar to that of Haematopinus has been reported by H. Scholl (1955, « Ein Beitrag zur kenntnis der Spermatogenese der...

SUMMARY1. The author who in his precedent papers has studied 72 specimens of African pigmy- mice (Mus, subgenus Leggada) gives the results of the cytogenetical analysis of 35 individuals from South-Africa, Coast of Ivory and Gaboun.2. South-Africa. — In the vicinity of Kirkwood, two subspecies of M. minutoides are living together, M. m. minutoides (2 n = 18) and M. m. indutus (2 n = 36). These both forms have been considered as species in statu nascendi resulting from the splitting of a polymorphic robertsonian system (MATTHEY 1964 a et b). By M. m. minutoides the heterozygoty of an autosomic pair, consisting in one metacentric and two acrocentrics, previously observed by a single ♀, was met again by another ♀. A pericentric inversion, detected previously by a single ♂, by which a pair was represented by a metacentric and an acrocentric, has been found again by five ♂ ♂. It is very likely that these both chromosomic mutations affect respectively the third and the sixth pair of autosomes.3. Coast of Ivory....

SUMMARYThe chromosomes in the three species of the family Membracidae, subfamily Centrotinae, have been studied in this paper. Of these, Oxyrhachis tarundus Fabr. and Otinotus lignicola Buckt. show the same diploid number of 21 chromosomes and Gargara mixta Buckt. shows 19 chromosomes in the males. The sex determining mechanism is of XO:XX type in the three species.During the earlier phases of meiosis, the X chromosome is seen as a small heteropycnotic body, occupying a more or less central position. During the first meiotic metaphase, this chromosome remains further away from the autosomal bivalents in Oxyrhachis and Otinotus only. The lagging nature of the sex chromosome is observed at anaphase I in Oxyrhachis and Otinotus.The first division is reductional and the second division is equational for the sex chromosome in all the three species.The primitive sex determining mechanism in the order has been assumed to be the XO type and the type number for the family to be 21. Metrical studies of individual c...

SUMMARYIn the present paper, the morphology of the somatic chromosomes and meiotic behaviour of Russelia equisetiformis Schlecht et Cham, and R. coccinea (Linn.) Wettst. has been described in detail and discussed.The chromosome number is 2n = 20 and n = 10 in both species. The chromosomes in R. equisetiformis are larger in size and fall under nine types out of which two pairs (type A and type C) are satellifed. The somatic complement of the other species 'R. coccinea) however, has only one pair of satellited chromosomes (type A). The chromosomes, in this species can be classified in eight types only.The meiotic division is fairly normal in both species. A high degree of secondary association of bivalents has been observed and the maximum association was found to be 2(3) + 2(2) indicating the basic number as four only.Lack of synchronisation in the meiotic division in the anthers of a flower was found to be characteristic in the two species studied. The presence of non-chromatic extranuclear bodies, specia...

SUMMARYThe chromosome number of 53 species of Angiosperms, occurring in the Valley of Aosta and in the National Park « Gran Paradiso » was determined. Some notes on the taxonomy of some species are presented in this paper.

SUMMARY (1) Although geobotany is the most valuable of the auxiliary sciences to taxonomy, the disciplines of cytology, genetics, physiology, etc. are a very good support for systematists studying critical genera. The present paper deals mainly with the taxonomical value of differences in chromosome number.(2) Only about 7 per cent.—about 17.000 out of 250.000—of the species of higher plants already described have been cytologically investigated. The highest frequency of species, or more than 90 per cent, of the floras, has ben cytologically studied in the floras of northwestern Europe, while the percentage of cytologically known species of the Tropics is very low.(3) Intraspecific polyploidy has been reported from less than 7 per cent, of the species of northern Europe, if the species concept is taken in its widest sense. More than 90 per cent, of these polyplotypes have previously been described as distinct species by classical taxonomists. Morphologically completely indistinguishable polyplotypes are u...

SUMMARYThe occurrence and meiotic behaviour of accessory chromosomes in a newly-delineated species of Panicum, viz., Panicum nehruense Jauhar et Joshi, are reported in this paper. As many as 24 accessories were observed apart from the normal complement of 2 n=54 chromosomes. Mosaicism in number of accessory chromosomes, as also of the normal ones, was encountered in the taxon. Numerical variation of the accessories was attributed to somatic elimination and/or somatic non-disjunction during the premeiotic mitotic stages. Some degree of pairing between the accessory chromosomes, upto bivalent level, was noticed. On the basis of a number of characters which the accessory chromosomes have in common with the normal chromosomes, coupled with the secondary association of the former with the latter at metaphase I, it was inferred that the accessory chromosomes may have originated from the normal chromosome complement, and presumably from different genomes, in this allohexaploid taxon.

SUMMARYProceding with the morphometric analysis of the Primate chromosomes, in this paper the chromosomes of the genera Hylobates, Presbytis and Colobus are examined. All the species studied have a diploid number of chromosomes of 2n = 44.The comparison of the total lengths of the karyotypes has not shown any significant differences among these genera. The comparative morphometric analysis of each single chromosomes has shown some similarities among the chromosomes of the different genera.

SUMMARYThe paper concerns the nuclear and the mitotic studies in the endosperm of Vicia faba.The endosperm was free nuclear throughout the course of its development. The nuclei showed remarkable variation in size and shape. The haustorial part of the endosperm showed more conspicuous variation. A study of the size of nuclei measured at different stages of endosperm development showed that the nuclear volume gradually increases with the advancement of age. The nuclei in the root tip cells were uniform.Mitotic division in the endosperm was synchronous. The normal cytological constitution of the endosperm was triploid with 3 n = 18 chromosomes. Higher polyploid and aneuploid nuclei were fairly common.Several mitotic derangements like bridges, laggards, rings of chromosomes and unequal distribution of chromosomes were characteristic of the degenerating endosperm.

SUMMARYA study of the mitotic behaviour of chromosomes of the different species and varieties of Aglaonema and Richardia has been presented in the paper. The Indian forms investigated are A. hospitum, A. costatum, A. costatum, var. ‘foxi’ and R. Elliottiana showing 38, 40, 48 and 32 respectively as the normal chromosome numbers. The high number of chromosomes of Aglaonema suggests their polyploid constitution. Numerical differences maintained both at an intra- and interspecific levels clearly indicate their distinct relationship.The chromosomes, are comparatively long and graded in size. The number of chromosomes possessing secondary constrictions varies from species to species. A maximum number of six pairs and a minimum number of two pairs of chromosomes have been noted in A. costatum, var. ‘foxi’ and A. hospitum respectively.Considerable numerical and structural variations have been encountered within the same somatic tissue. It is quite significant that a high frequency of variation has been observed ...