Cellophane Surface Research Articles

Studies on the influence of leaf washings on infection by Mycosphaerella ligulicola

SUMMARYInfection of chrysanthemum leaf discs by spores of Mycosphaerella ligulicola was increased in the presence of concentrated leaf washings obtained from five plant species tested. On separation of leaf washings by dialysis the residue stimulated infection and caused aggregation of hyphae on leaf and cellophane surfaces. In the presence of the diffusible fraction an extensive branching network of hyphae developed but there was no increase in infection except in the presence of the chrysanthemum diffusate.Infection of leaf discs of certain plants normally resistant to M. ligulicola occurred in the presence of concentrated leaf washings.Leaf washings from a resistant variety of chrysanthemum had the same effects as those from a susceptible variety. An extract of chrysanthemum leaves was less effective in stimulating infection than was a leaf washing.Defined nutrient media and potato extract stimulated infection but caused the development of different growth habits on leaf surfaces.The active components of the dialysis residue of chrysanthemum leaf washings were heat‐stable but apparently volatile. Eluates from strips of certain regions of paper chromatographs of leaf washings and potato extract caused increased infection together with development of characteristic growth habits of the fungus on the leaf.

A Rapid Method for Determining the Proportion of Viable Bacteria in a Culture

Summary: A method of making graticules on the surface of Cellophane is described. The proportion of viable bacteria in a culture can be estimated by inoculating a sample on to such a graticule, and counting the organisms before and after a short period of growth.

Some Methods Used in Tracing Radioactive Growth-Regulating Substances in Plants

1. An inexpensive applicator made to hold radioactive solutions and mixtures in a pipette at a distance from the operator is described. As little as 0.01 ml. of solution can readily be delivered and placed on a plant with this apparatus. 2. A simple method of plating samples of ground radioactive plant tissues on the tacky surface of cellophane is described. The method makes possible the measurement of radioactivity in a weighed sample of ground tissue spread in an even layer essentially one particle in thickness. 3. Evaluation of counts in terms of weight of the tagged compounds was accomplished by impregnating a plated sample of tissue with a known amount of the tagged compound.

ON THE LUSTRE OF ARTIFICIAL SILK.

Dr. A. Herzog has already described that the lustre of artificial silk is chiefly decided by the optical structure of surface, the construction and transparency of a thread and the titre of a single filament. The reflection by cellophane occures most remarkably for the normal direction, and it is therefore assertained that the surface of cellophane or artificial silk must be nearly optically uniform. The lustre of artificial silk is, of cause, considerably due to the shape of its surface. However, the author now assumed that a single filament of artificial silk is formed of circular cylinder and arranged parallel to each other, and showed on the basis of geometrical optics that the most part of incident light should be regularly reflected and in consquence the thread should have a glaring metallic lustre with the light of parallel direction to yarn, and that the most part of incident light should be irregularly reflected to every direction and in consquence the thread should have a glassy and aventurine lustre with the light of perpendicular direction to yarn. The experimental results are coincident with this theory.The twist of yarn affects also remarkably the lustre, and with an increase in the twisting dagree the metallic lustre is modified to the aventurine lustre and maximum gloss is shifted to the direction of surface twist.The multiplication of filament, the irregularity of surface, the residual sulphur of viscose silk, etc. also modify the metallic lustre of artificial silk.