A comparison of methods for the isolation of fungi from rhizospheres

A comparison was made between the fungi isolated from non-rhizosphere soil and from rhizosphere soil of mature dwarf bean plants by three methods of isolation: soil dilution plating, soil plating, and soil washing followed by the plating of washed soil particles. The data obtained with rhizosphere soil demonstrated that the use of the soil-washing technique allowed an increased frequency of isolation of sterile forms, Fusarium spp., and members of the Mucorales, whereas heavily sporing forms were isolated with decreased frequency. It is concluded that, compared with other isolation methods, the soil-washing technique allows a more accurate assessment of fungi active in the rhizosphere.

ETHYLENE DIAMINE TETRAACETIC ACID AND CITRIC ACID AS ELUANTS IN ION EXCHANGE SEPARATION OF RARE EARTHS

Studies of the distribution of rare earths between the cation exchange resin Zeokarb 225 and solutions of ethylene diamine tetraacetic acid (EDTA) show the existence of large separation factors between members of this series. However, column experiments show that the separation is poorer than with citric acid, probably because of a slow process occurring in the solution. The variation of column efficiency with distribution coefficient has been examined. Elution of europium with citric acid appears to be diffusion controlled, while that with EDTA is not. Further experiments with strontium indicate that its elution with both EDTA and citric acid is diffusion controlled. The results are in general agreement with Glueckauf's equation relating column variables with the height equivalent to a theoretical plate. Column irregularities appear to account for the very low diffusion constants calculated from this relation.

The Problem of Crude Rubber

In recent years, rubber manufacturers have made tremendous progress in compounding and in methods of manufacture, yet they continue, as they always have done, to regard smoked sheet and crepe from the plantations as the essential raw material of their industry. As a matter of fact, however, latex is the essential raw material, and the changes which it undergoes on the plantations are among the factors which influence the quality of the final rubber and therefore play a part in its possible uses. In the face of this, it seems like a paradox to say that the processing of latex on the plantations is based on arbitrary methods, without any consideration taken of their effects on the properties of the finished rubber, whereas mixing and vulcanizing operations are scrupulously controlled by manufacturers. For what reason does this paradoxical situation continue to prevail? Only because of the way by which the broker still evaluates rubber. The plantations are obliged to classify their commercial product into different types, according to color, superficial appearance, cleanness and the presence or absence of bubbles in sheet rubber, with complete disregard to its intrinsic properties, the latter not even being measured. To be regarded as the best quality, commercial rubber must be of a uniform color, must have a regular surface and must contain neither impurities nor bubbles.