Volume 75, Issue 5
May 1972, pages 201-256
pp 201-214 May 1972
Chromosome numbers in six species ofOphioglossum available in Poona and inHelminthostachys zeylanica L. obtained from Kerala are given.O. nudicaule L.,O. gramineum Willd.,O. pedunculosum Prantl (sensu non-Desv.) andO. fibrosum Schum. were found to haven=120 chromosomes.O. aitchisoni d’Alm. had 210–215 bivalents, andO. reticulatum L. hadn=420. Of these the chromosome number inO. peduculosum was not reported before. Meiotic cycle in this species showed some irregularities such as bridge formation in some cases at anaphase I.
The paper further discusses the significance of polyploidy observed inO. nudicaule and traces the evolutionary trends seen in the genus on the basis of the chromosome numbers. There exists some sort of correlation between the size of plants and their chromosome numbers. No variation in the number of chromosomes in different plants of the same species growing in different localities was observed.
On the basis of the chromosomal analysis, it seems thatO. nudicaule, O. gramineum group is more primitive andO. aitchisoni, O. reticulatum groups more advanced. This agrees with the conclusion drawn by one of us (Mahabalè, 1965) in this regard, on the basis of the morphology of species.
pp 215-220 May 1972
The vegetative anatomy ofStemona tuberosa (Stemonaceae) has been studied. The results of this study reveal certain number of noteworthy characters not known before for the genus. Furthermore, a considerable number of differences between this taxon and the species already studied are brought to light.
pp 221-230 May 1972
Out of 18 species ofAlangium comprising the unigeneric family Alangiaceae, 15 species belonging to four subgeneric sections were investigated. As a result of this study, it is observed that the vein endings show different types of terminal idioblasts characteristic of each section. Enlarged terminal tracheary idioblasts coupled with the occurrence of tracheoidal idioblasts in varying proportion and combination are observed to be the regular feature of the sectionAngolum while those of the sectionMarlea, excepting one species, possess enlarged terminal tracheary idioblasts but exhibiting aggregated and storied condition. In sectionRhytidandra, the same enlarged terminal tracheary idioblasts are present but showing a tendency towards the elimination of reticulate or scalariform sculpturings from their walls. The species of the sectionConostigma possess distinctly lobed enlarged terminal parenchyma exceptingA. maliliense in which a new type of special idioblast designated as vermiform parenchyma is found. A positive correlation exists between the types of idioblasts and the distributional pattern of the species.
pp 231-245 May 1972
Samples of the littoral and alluvial placer deposits of the black sand concentrates which contain radioactive resistate minerals were collected from various parts of South India and their characters with respect to colour, density and radioactivity were presented.
With the aid of a hand magnet and a sensitive Frantz Isodynamic laboratory model L1 magnetic separator, each sample was subdivided into magnetic, paramagnetic and nonmagnetic components.
The paramagnetic mineral assemblage was further subdivided into fractions of varying mass magnetic susceptibility. The amounts of these fractions constitute the frequency distribution of mass magnetic susceptibility, expressed in terms of current strength, of the sample whose character is then evaluated by means of certain standard statistical parameters.
Variation in the characters with respect to grain size was also studied. Further, it is suggested that the amount of magnetite is an “Index of Maturity” for these residual deposits.
pp 246-256 May 1972
1. The present paper deals with the gross anatomy and certain mechanical properties of the stem of sixteen lianas with anomalous secondary growth in comparison to that of an erect plant.
2. An analysis developed from mechanics considerations shows clearly that liana stems have adopted themselves to some well-known engineering principles in developing their internal structure to counteract the stresses and strains caused by the natural external forces of wind, rain, light, etc.
3. Apart from the size of the pith, the shape of the pith (circular, oval) and its eccentricity with respect to the xylem cylinder also affect the flexibility.
4. The order of increase of flexibility as predicted on theoretical considerations agrees well with the order obtained from the experimental results. Further, a close relation between flexibility and water content of these plants exists.
5. A detailed study of three varieties ofBougainvillea lends support to the viewpoint stressed recently by Esau and Cheadle (1969) that complimentary cambial strips develop just adjacent to the secondary phloem and the cambium is bi-directional in this plant.