The present investigation has included the study of the morphological and cytological details of seventeen populations of three aquatic submerged taxa viz. Hydrilla verticilla Presl., Ottelia alismoides Pers. and Vallisneria spiralis L. belonging to the family Hydrocharitaceae. The species examined were collected from various localities in the plains of West Bengal.
The chief objective was to analyse the nature of association among different environmental factors, morphological variations and chromosomal peculiarities.
Morphological details, giving average leaf length and breadth and length of internodes, were observed in members of each population and the average calculated. Karyotype analysis was carried out on each population following pretreatmentorcein squash technique modified for the purpose. The pH and proportions of Ca, Mg, K and Na were calculated of the aquatic medium surrounding each population.
Eight populations of H. verticillata were studied. Seven show 2n=24 chromosomes while only one population has 2n=16 chromosomes. The karyotype formulae were observed to differ significantly.
The water analysis data indicated a wide range of variation in the proportions of minerals and of pH. No direct association among the morphology, water analysis data and the chromosome numbers was noted.
Four populations of Ottelia alismoides studied showed chromosome numbers 2n=44, 66 and 68. The populations with same chromosone numbers differ from each other in the structural composition of chromosomes. Population III (2n=68) is an aneuploid one which may have arisen through duplication of two chromosomes from a 2n=66 type or from 2n=33 type following duplication of the entire genome. The tetraploid populations I and II have a total chromatin length less than double those of III and IV indicating a diminution in chromosome size with polyploidy.
The water analysis data indicates that the species can tolerate wide chemical variations in their aquatic environment.
In the five populations of Vallisneria spiralis the chromosome number is 2n=30 for populations I and III, 2n=40 for II and V and 2n=24 chromosomes for IV. Karyotypes differ even among the populations with same number. Total chromatin length shows a proportionate increase during polyploidy.
Populations II and V with 2n=40 chromosomes have apparently evolved through polyploidy followed by structural changes in the chromosomes. Population IV represents a completely different picture. Its chromosome number may have been derived from 2n=40 or 2n=30 forms through non-disjunction and maintained through vegetative propagation.
There is no apparent association between the minerals present in the aquatic media and the chromosomal composition of the populations. The only exception is population IV.
The observations show that cytological races cannot be correlated with morphological characteristics. The water analysis data can suggest no specific association between the morphological and cytological characteristics, except that an alkaline medium of range of 6.8 to 8.55 is necessary.
In all the taxa studied vegetative mode of reproduction is an important factor of propagation. The occurrence of variant nuclei in the somatic cells indicates the way through which a new form could have arisen in nature. Such a variant nucleus, on entering a growing shoot, may give rise to a cytologically different form which may later form a colony under environmental conditions best suited for its survival. The excess of nutrients present in the surrounding media may permit all these forms to survive.
As far as the present study shows the alkalinity and mineral content do not have any definite effect on the evolution of cytological races. A possible role of the supply of nutrients through soil and of light intensity can be suggested.

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Effects of temperature and nitrogen on meiotic chromosome pairing in clones of autotetraploid rye were studied separately. Both experiments revealed that quadrivalents are highly sensitive to changes in environmental conditions. On the other hand, bivalent frequency in the PMC remained stable with temperature changes in spite of a significant decrease in chiasma frequency. With nitrogen stress, however, bivalent frequency in the PMC increased significantly. These results led to the conclusion that a bivalent formation is much more easily and efficiently accomplished than the formation of a multivalent. The underlying reasons for the greater stability of bivalents compared to multivalent configurations are discussed. The limitations of the improvement of meiotic behaviour of autotetraploids by increasing the quadrivalent frequency are also discussed.

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6 species of the genus Alysicarpus are investigated. The detailed karyotypic analysis revealed the presence of 1 pair of secondarily constricted chromosomes (D type) in all the species justifying their inclusion in one genus. Though karyotypes exhibit gross similarity, they differ from each other in minor details. The regularity of meiotic behaviour is noticed, in all the taxa. However, some abnormalities are also recorded. The basic number x=8 for the genus is supported by this work.

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Results obtained by staining plasmalemmata and mucilage with phosphotungstic acid (PTA) are described. Plasmalemmata are strongly contrasted by staining with PTA and it is possible to study the way in which the membranes of the secretory vesicles are restructured. Contrary to what has already been reported for Drosera capensis, structural alteration of the membranes only starts at the moment when the vesicles open in the periplasm.
In addition, the author confirms the very great affinity of PTA for mucilage and compares the images obtained with this stain with those observed subsequent to Thiery's reaction.

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Karyotypes are described in Hemiechinus auritus and Paraechinus aethiopicus which have 48 chromosomes in 2n. The male complement of H. auritus consists of 43 macro- and 5 micro-chromosomes while that of the female comprises 44 macro- and 4-micro-chromosomes. The X chromosome is the smallest metacentric macro-chromosome, while the Y is a small subtelocentric micro-chromosome. These associate end-to-end at meiosis I.
The male karyotype of P. aethiopicus consists of 44 macro- and 4 micro-chromosomes. The autosomes are metacentrics or submetacentrics in morphology. The sex-complex is characterized by the medium-sized X chromosome and the mediumsized submetacentric Y.

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The structure of chromatin during spermiogenesis of a lizard was examined. The fibrillar nature of chromatin is maintained during all time even in the mature sperm, but the fibers pass through a process of thickening and reorganization which begins with a homogeneous and diffuse aspect, going through an organization of chromatin fibers parallel to the long axis of the nucleus, disposed concentrically but not evenly displaced. In a final stage the fibers are thicker and closely packed showing almost no nucleoplasm among them.

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The diploid number, karyomorphology and morphometrical analysis of metaphase chromosomes in three teleostean fishes have been studied from the kidney cells of the female after colchicine-citrate-flame drying-Giemsa technique. Mystus gulio (Fam: Bagridae) possesses 2n=58 with chromosome formula as n=15 m+6sm+1st+7 T (NF 102) and the mean length values ranging between 1.90 and 0.77 micron from the longest to the shortest chromosome. Eutropiichthys vacha (Fam: Schilbeidae) have also 2n=58 chromosomes, but with the formula of n=5 m+10sm+6st+2t+6 T (NF 100) and the mean length values of chromosomes from 1.73 to 0.67 micron. Mastacembelus armatus (Fam: Mastacembelidae) have 2n=48 chromosomes with the formula as n=5 m+2sm+1st+16 T (NF 64) and the mean length values ranged between 1.81 and 0.89 micron. The karyotypes of these species have been compared with the related ones and it has been suggested that pericentric inversion played the significant role in the evolution of their karyotypes.

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Cytogenetical studies in garden cultivars of Amaryllis vittata, Narcissus tazetta, Hemerocallis aurantiaca and H. fulva revealed their existance as different cytotypes. The karyotype was symmetrical in all these excepting N. tazetta which showed an asymmetrical karyotype. The role of chromosomal repatternings and hybridization is evident in the evolution of these taxa. Irregular segregation of small chromosomes probably accounts for the aneusomatic cells in Hemerocallis aurantiaca and Amaryllis vittata (cultivar ‘b’). The following karyotypes were established:
Amaryllis vittata L.:
cultivar ‘a’-K(2n)=22=B^st₄+B^sm₂+C^sm₂+C^st₄+D^st₂+E^m₄+E^sm₂+E^st₂
cultivar ‘b’-K(2n)=44=B^sm₂+C^sm₂+C^st₁₄+D^st₉+E^m₇+E^st₁+F^st₂
Narcissus tazetta L.:
pale-yelow cultivar-K(2n)=32=C^st₅+D^m₁+D^st₄+D^t₄+E^st₃+F^m₁+F^sm₁+F^st₁₃
dark-yillow cultivar-K(2n)=30=C^st₂+D^sm₂+D^st₁₀+E^sm₂+E^st₃+F^sm₂+F^st₉
Hamerocalis aurantiaca Bak.:
K(2n)=33=E^m₃+E^t₁+F^m₃+F^sm₁₇+F^st₃+G^m₂+G^sm₄
H. fulva L.:
K(2n)=22=E^m₂+E^sm₂+F^m₃+F^sm₄+F^st₈+F^t₂+G^m₁

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The hybrid, known as V.×teasii is intermediate between the parents (V. tenuisecta and V. hybrida) in morphology and shows complete male sterility but reasonable amount of female fertility, despite normal pairing at metaphase I. This sterility could not be altered by colchiploidy indicating a genic nature of male sterility. The amphidiploid has predominant bivalent pairing which indicate that the genomes of the parent species are structurally differentiated.

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The structural variation in the chromosome complement of Allium sativum has been noted by previous workers. However, no attempt has been made to study the heterozygosity with the help of banding technique after Giemsa staining. On the basis of the banding pattern found in the present material, three groups could be detected. In this material, out of 16, only 4 chromosomes showed bands in general. The three groups based on the banding patterns are as follows:- a) Bulbs with chromosomes showing bands only on one pair having secondary constrictions, b) Bulbs with chromosomes showing bands on two pairs with secondary constrictions, but heteromorphicity in banding pattern was noted in one pair, c) Bulbs with chromosomes showing bands on one pair with secondary constrictions and on two other chromosomes, whose homologues, however, did not reveal bands.

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Two African perennial hexaploids (n=27) of Echinochloa were collected. One from Gao, Mali was stoloniferous. Another one from Banket District of Rhodesia was a cormous perennial.
These two hexaploids have been treated as E. stagnina by taxonomists, but cytological evidence of their F₁ hybrid indicated that they have diverged to such an extent that meiosis conjugation is considerably impaired in the hybrid between them.
E. stagnina should be considered as a complex of several species because some Echinochloa specimens which are different from each other in morphological characteristics, chromosome number and genome constitution have been classified as this taxon.

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Karyotype analysis, meiosis, pollen grain morphology, thin layer chromatographic analysis of phenolic compounds in leaves, external morphology and flowering behaviour were studied in Trichosanthes cucumarina and two fruit colour varieties of T. anguina.
The two species differed not only in their karyotypes but remarkably in total chromatin length, pollen grain morphology and in leaf, fruit and seed sizes, and in flowering behaviour. The total chromatin length of T. cucumarina was more than T. anguina. The leaves, fruits and seeds of T. anguina were larger than T. cucumarina. Compared to T. anguina, T. cucumarina was a late flowering type. Meiosis was normal in all the materials. The number of spots for phenolic compounds in T. cucumarina was more than the two varieties of T. anguina. Only three spots were in common between the two species. The two species differed in at least seven reliable constituents.

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The mitochondrial division cycle and morphological changes of the mitochondria in the plasmodium after fusion of microplasmodia of P. polycephalum have been studied with acid fuchsin staining and light microscopic autoradiography.
The number of mitochondria in the plasmodium increases during late S and early G₂ and doubles at intervals of approx. 14h. The mitochondria are classified into 3 types, small spherical, oval, and dumbbell-shaped mitochondria. The frequencies of each type of mitochondria were examined at various times after fusion of microplasmodia. The results indicate that the decrease in the number of dumbbell-shaped mitochondria parallels the increase in the number of small spherical mitochondria and the relative number of mitochondria. It is also apparent that there is a sequential appearance of the dumbbell-shaped, the small spherical and the oval mitochondria. This suggests that the mitochondria multiply by division of dumbbell-shaped mitochondria. Furthermore, it is suggested from light and electron microscopic observations and light microscopic autoradiography that in fused plasmodia, a majority of the mitochondria synthesize DNA and divide during specific periods of the nuclear mitotic cycle. Therefore, we propose the existence of a mitochondrial mitotic cycle with periods, mitochondrial M (mM), mitochondrial G₁ (mG₁), mitochondrial S (mS), and mitochondrial G₂ (mG₂). The duration (in hours) of the 4 phases are mM=1.5, mG₁=3.0, mS=7.5, and mG₂=2.0 and the generation time of mitochondria is 14h.

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Root-tips of garlic (Allium sativum) were used to study the cytological effects of 1-naphthonitrile and 2-naphthonitrile in isolation and in combination. The treated interphase cells showed pycnotic and elongated nuclei. The mitotic abnormalities observed in treated root-tip cells included scattering of chromosomes, nonsynchronization in the movements of chromosomes, stickiness, chromosome breakage, bridges during anaphase, lagging of whole chromosomes, and the formation of micronuclei. Low concentrations of one compound appear capable of enhancing the overall effects of the other with respect to inducing mitotic abnormalities. The mitotic index was observed to decrease with increasing concentrations of either or both of these two constituents. It is suggested that this bioassay technique might be more economically feasible for preliminary rapid screening of the biological effects of tobacco smoke constituents from various cigarettes.

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Effect of gamma-rays on 1) dry seeds 2) seeds presoaked for 3 hours in distilled water and 3) seeds pretreated with 0.2%colchicine for 1 hour were studied. Germination was adversely affected in presoaked seeds. Almost all the germinated seedling survived. In M₂ fringed leaf mutant, strap leaf mutant, advanced stigma mutant, trisomic and male steriles were isolated. Results of genetical analysis revealed monogenic recessive nature of first two mutants. Possible pleiotropic or close likage nature of mutants has been discussed. The trisomic displayed reduced vigour and high pollen sterility, which is influenced by environmental factors. Temperature sensitivity of male steriles has also been discussed. The advanced stigma mutant changes the breeding system from inbreeder to outbreeder. Its utility in hybridization programme is obvious. As all these mutations were isolated in precolchicinized irradiated seeds the importance of colchicine treatment in combination with gammarays resulting in increased spectrum of mutations has been discussed.

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In asexual cultures, a colony of Pleodorina usually consists of 32, 64, or 128 cells. It is not a mere mass of the same kind of cells but is an organized structure composed of two types of differentiated cells, i.e. reproducing cells and somatic cells. When isolated from mother colony, reproducing cells ceased to grow and began to divide to make up small colonies consisting of 2, 4 or 8 cells size of the colonies varying according to the initial state of the reproducing cells. In these small colonies, reproducing and somatic cells were clearly distinguishable.

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Effects of X-irradiation on pairing of chromosomes in R₁ Pteris longifolia is reported. Selfed one leaf sporophytes have been irradiated to a dose ranging from 2 Kr to 10 Kr. Irregularities in pairing behaviour of chromosomes during meiosis associated with fragments have been observed in the irradiated plants. The observations have been discussed in the light of informations available from higher plants. The cause for such abnormalities are attributed more to the physiological disturbances in the cell than to the fragment of the chromosomes. Translocations have not been observed. This information has been obtained from irradiated sporophytes of selfed Pteris longifolia, the tetraploid sexual species of ferns for the first time.

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The polytene chromosomes of Cr. algarum from the Black Sea coast of Bulgaria were analysed. Salivary-chromosome map of the species was made. The diploid set of chromosomes is 2n=6. The first couple is submetacentric, the second-metacentric and the third-acrocentric. The three couples have significant differences in length. The chromosomes are concentrated in chromocentre. A comparatively high degree of chromosomal polymorphism was estimated and it was probably in relation with the distribution of the species. Aberrations, specific for every year and repeatedly occurring aberrations, determining the presence of “stable” polymorphism were found. Differences in the numbers of chromosomes in the somatic and in the sexual cells were reported.

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Lagenisma coscinodisci, an endobiotic parasite of the centric diatom Coscinodiscus granii produces typical biflagellate zoospores. The special feature of the surface structures of these zoospores is that the lateral hairs on the tinsel flagellum narrows abruptly to form very fine tips. There are a number of interesting structures, described as X-bodies present near the periphery of the zoospore body. These bodies consist of distinct outer and inner parts and have structural similarities with ‘Rohr’ and ‘Stachel’ demonstrated by Keskin and Fuchs (1969) associated with the infection of Polymyxa betae.

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This paper presents results of investigations on cellular changes produced by extracts of betel leaves (Piper betle Linn.) on root tip cells of onion. Betel leaves together with lime, a few pieces of arecanut and dried tobacco leaves are chewed as ‘paan’ by many people in countries like India and Ceylon.
The specific effect of the extract on mitoses was the production of agglomeration of chromosomes and bridged metaphases. Chromosome fragments were rarely observed. Differences in condensation of the chromosomes, bizarre forms of nuclei, cells with large nuclei with no corresponding increase in cytoplasm etc. were also observed in the treated cells. The present study has provided for the first time informations regarding cellular damage produced by extracts of betel leaves.

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