108 BELL SYSTEM TECHNICAL JOURNAL 



Gulfport, from a test post in Gulfport, Mississippi, used for our assay 



work 

 The results of the assay with these strains of Coniophora cerebella and Lenli- 

 nus lepideus showed the average weight loss in percent due to decay to be 

 32.0 and 27.3 percent respectively which was as great as that in the previous 

 soil tests with the single representative of these species. A greater anwunt 

 of decay was obtained with one strain of Coniophora cerebella due to a slight 

 change in technique, i.e., the fungus was first established on small slabs of 

 southern pine sapwood, and then sterile oven-dry blocks were dropped on 

 the vigorously growing fungus. The large amount of decay (60%) which 

 resulted led to the adoption of this modification in all subsequent tests. 



The foregoing tests may be regarded as supporting the use of the criteria 

 previously employed in the selection of fungi for laboratory tests — namely, 

 their occurrence as saprophytes of wood, their isolation from service ma- 

 terials for example, pine telephone poles or tests posts, and their demon- 

 strated ability to bring about decay of wood in the laboratory. 



As a result of these preliminary experiments, the use of soil as the medium 

 in testing procedure was adopted. 



Soil Contact Technique 



On the basis of the foregoing experiments and in view of the rapidity of 

 the decay occurring on test blocks in the soil-contact test, the following 

 method is described as a means of evaluating the effectiveness of preserva- 

 tives or toxic materials which are recommended for the protection of wood 

 or other cellulosic materials. The method may also be used to study en- 

 vironmental factors which affect decay or it may be adapted to the study of 

 fungi other than the wood-destroying fungi of the Basidiomycetes. 



Ordinary top soil, such 'as a florist would use for potted plants, is satis- 

 factory for the test. While experience has shown that top soil from a 

 number of different sources may be used without materially affecting the 

 results, standardization would be desirable. Therefore the term "soil" 

 will be defined as a sandy loam type which contains 4-6 percent of organic 

 matter and a pH originally between 5-7. The soil is passed through a 

 coarse-mesh screen to remove rubble, stones and other debris; this is most 

 easily accomplished when the soil is dry. The screened soil is moistened 

 with just enough water to effect cohesion into a soft ball when squeezed in the 

 hand, and a check may then be made by determining the moisture content 

 of the soil. When prepared in this manner the moisture content of the soil 

 should be 20-25% on an oven-dry weight basis. In an alternative procedure, 

 the moisture content of the dry soil is ascertained and then sufficient water is 

 added to give a moisture content of 20-25%. 



Bottles, 12 cm. high and 6 cm. in diameter, are half filled (60-100 grams) 



