• Volume 16, Issue 6

      December 1942,   pages  165-211

    • Two new species ofDidymopsora from India

      M J Thirumalachar

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      In the present paper an account of the morphology and life-history of two new species ofDidymopsora, D. Toddaliæ, andD. macrospora is presented. The rust is parasitic on the leaves ofToddalia aculeata var.gracilis andfloribunda.

      The rust onToddalia aculeata had previously been identified by Petch asAecidium Toddaliæ, and later on changed toUredo Toddaliæ. Sydow in 1920 transferred the rust to the genusCtenoderma established by him asC. Toddaliæ (Petch) Syd. He mistook the urediospore; for the teliospores. Mains who merged the genusCtenoderma withSkierka, suggested that the rust onToddalia might be a species ofSkierka. In the present investigation, the telia have been observed, and the rust has been placed in the genusDidymopsora.

      Pycnia are intraepidermal, applanate, without conspicuous ostiolar paraphyses. Uredia are subepidermal, and the urediospores are stipitate, with characteristic lateral ridges at the sides and at the apex.

      Telia are exserted out in shortCronartium- like columns, and the spores are two-celled, sessile, hyaline, with a single distinct germ pore in each cell and germinating immediately. Telia have not been observed forDidymopsora macrospora.

    • Studies in Indian hepaticæ - III. On a new species ofNowellia, N. indica Pandé et Srivastava from the Western Himalayas

      S K Pandé T N Srivastava

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    • On the multiperforate plates occurring in the xylem vessels of some monocotyledonous roots

      B C Kundu

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      The occurrence and structure of multiperforate plates in the xylem vessels of the roots of some monocotyledons are described. Such plates are present in all the vessel segments of the roots of many members of the family Araceæ and inCrinum asiaticum. In all these plants vessel segments with simple perforations have not been observed. The vessel segments as found in these roots may be of three types : (i) those having oblique end walls at both ends; (ii) those having oblique end wall at one end and transverse or slightly inclined end wall at the other; (iii) those having transverse or slightly inclined end wall at both ends. The perforation plates of these segments may be scalariform, scalariform with branched bars, or reticulate. The bars of the plates can be correlated to the scalariform-reticulate thickening of the lateral walls of the vessel segments. These types of vessel segments are regarded as forming a primitive feature. Further it is concluded that the xylem vessels of roots have developed phylogenetically from typical scalariform tracheids by the loss of pit membranes at their ends.

    • The mechanism of β-amylase inhibition by vitamin C

      P Seshagirirao K V Giri

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      A critical study of the mechanism of β-amylase inhibition by vitamin C has been made. The hydrolysis of starch by the amylase is inhibited by vitamin C alone and vitamin C-Cu complex, the latter exerting greater inhibition.

      The oxidised products of the vitamin prepared by Cu oxidation, also exert inhibition of the hydrolysis of starch by the amylase.

      In addition to the inhibition exerted on the hydrolysis, vitamin C-Cu complex and the oxidised products of the vitamin inactivate the enzyme in the absence of substrate. Vitamin C alone brings about very feeble inactivation of the enzyme.

      A variety of compounds—oxalic acid, uric acid, xanthine, guanine, theophylline, yeast nucleic acid, creatinine, cysteine, cystine, glutathione, histidine, potassium cyanide and hydrogen sulphide, which are shown to inhibit the catalytic oxidation of vitamin C by Cu++ annul the inhibition and the inactivation caused by vitamin C, vitamin C-Cu complex and the oxidation products of the vitamin.

      A suggestive correlation between the inhibition of the hydrolysis and the inactivation of the enzyme on the one hand, and the oxidation of vitamin C on the other, has been established.

      The physiological significance of these findings in their relation to the influence exerted by the purine derivatives and other stabilisers of vitamin C oxidation in regulating the activity of amylases in plant life is discussed.

    • The development of the female gametophyte and floss inBombax malabaricum D.C.

      I Banerji

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      The paper gives an account of the development of the female gameto-phyte and floss inBombax malabaricum.

      1. The ovules are anatropus and bitegmic. Both the integuments take part in the formation of the micropyle which is somewhat zig-zag.

      2. The archesporial cell is hypodermal in origin. Two megaspore mother cells have been noted in many preperations. A normal linear tetrad of megaspores is produced of which the lowermost one becomes functional and produces a seven-nucleate embryo-sac of the normal angiospermous type. The antipodals are ephemeral. The development of the embryo is very much delayed. Endosperm development is of the nuclear type.

      3. The floss develops from the cells of the epidermal layer of the inner carpellary wall of the boll. All the cells, however, do not develop. The ‘non-fibre’ cells as also some of the fibre cells divide anticlinally during the early stages of the development of the fibre. The growth of the latter seems to be arrested after division. The mature fibres are uninucleate and have an unconstricted base.

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