• Volume 75, Issue 4

      April 1972,   pages  155-200

    • A new genus of phragmosporous phaeostilbeae from a rubber estate in Kerala

      V Agnihothrudu

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      Dendrographiella podosporioides Gen.et sp. nov. collected on dried latex of rubber,Hevea brasiliensis Muell from Kerala State is described. The fungus forms septate porospores on synnemata.

    • Studies in myrsinaceae - I. A contribution to the embryology ofMaesa dubia wall

      K Sankara Rao

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      Maesa dubia (Tribe Maesoideae) of the family Myrsinaceae shows some interesting embryological features. The floral parts arise in acropetal succession. The vascular bundle of each stamen divides in the connective. The tetrasporangiate anthers dehisce by longitudinal slits shedding the pollen at the 2-celled stage. The endothecium and the next layer develop fibrillar thickenings except at the region of dehiscence.

      The ovules are anatropous, tenuinucellar and bitegmic. The micropyle is organised by both the integuments. While there is usually a single hypodermal archesporium there is a tendency for the differentiation of multiple archesporium. Only one archesporial cell functions and develops into megaspore mother cell. The tetrad of megaspores is usually linear. Some abnormalities in the sequence of degeneration of the three micropylar megaspores are observed. The development of the female gametophyte follows the Polygonum type. A prominent endothelium is differentiated at the dyad stage in the ovule. The chalazal half of the embryo sac forms an aggressive haustorium.

    • Embryological studies in compositae - III. A contribution to the embryology ofBlainvillea rhomboidea, Cass. (B. latifolia, DC)

      S Sundara Rajan

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      InBlainvillea rhomboidea, Cass. the floral parts arise in acropetalous succession. The archesporium consists of two linear rows. of cells In the fully formed anther there is an epidermis, an endothecium, a middle layer, a tapetum and two linear rows of microspore mother cells. Tapetal cells become binucleate and are of the plasmodial type. Microspore tetrads are isobilateral, tetrahedral and decussate. Exine of the pollen grain is echinate. Shedding is at the three-celled stage as in the majority of Compositae. Endothecium shows faint fibrillar thickenings at the time of anther dehiscence.

      Ovules are anatropus, unitegmic and tenuinucellate. A hypodermal archesporial cell directly functions as the megaspore mother cell. Embryo sac development is of the Polygonum type. More than one megaspore in the tetrad show signs of development. Organised embryo sac is six-celled with only two antipodals. A secondary multiplication of nuclei in the antipodal cells results in a variable number of nuclei.

      Endosperm is of theab initio cellular type.

      Embryogeny conforms to Asterad type.

      Fruit wall has a thick layer of tannin cells in the hypodermal layers.

    • Root sclereids ofSyzygium cumini (L.) Skeels

      A R Rao C K Rao

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      Sclereids in the roots ofSyzygium cumini (L.) Skeels (Myrtaceae) are polymorphic. In addition to the brachy-, osteo- and bizarre sclereids, there occur an interesting kind of sclereids—the fibre sclereids—resembling the fibres in some respects.

      Sclereids appear only after the onset of secondary activity and fall into one of the following categories depending on their origin: (a) a continuous strand of sclereids in the secondary cortex. This develops from parenchymatous initials that are derivatives of phellogen. Fibre sclereids occur only in this region along with ordinary sclereids and a few fibres. (b) sclereids formed through secondary sclerosis of distal mature parenchyma cells of the dilating phloem rays. (c) Sclereids formed through secondary sclerosis of mature parenchyma cells in old phloem. Sclereids of categoriesb andc a but on those ofa forming a composite strand.

      All the kinds of sclereids here possess thick, highly lamellated lignified walls with simple and wide pit canals ending in round or oval apertures. The adult sclereids are devoid of nuclei, starch or crystals. Insoluble tannin is present in them except in those formed from phloem parenchyma.

      Ontogenetical stages of the various kinds of sclereids are similar except that fibre sclereids show a pronounced intrusive growth which although initially bipolar later becomes unipolar. Other kinds of sclereids show either a purely symplastic growth or a combination of various degrees of symplastic and intrusive growth which is either diffuse (some osteosclereids) or multipolar (bizarre sclereids).

      The inadequacy and unreliability of the existing classifications of and criteria for classifying different mechanical elements particularly in sclereid containing plants are discussed and suggestions made.

    • Seasonal variation and exogenous hormonal effect on the interrenal glands ofRana hexadactyla lesson

      S Kasinathan S L Basu

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      Seasonal variation of the interrenal cell-types both in male and femaleRana hexadactyla and the exogenous hormonal effects on the male interrenals have been studied quantitatively. The interrenal cell-types wax and wane throughout the year. A reciprocal relation between the clear and compact cells of the interrenal in both sexes of the frogs has been observed.

      The decrease of compact cells and regression of interrenal activity resulting from steroid administration were found to be statistically significant. Concomitant with the decrease of interrenal activity, a regression of interstitium of testis has been noticed.

      Pituitary administration stimulates interrenal activity accompanied by an increased spermatogenesis.

      A possible role of exogenous steroid and pituitary hormones on the interrenal has been discussed.


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