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BELL SYSTEM TECHNICAL JOURNAL 



organisms in duplicate are used in each test (Fig. 10). Lentinus 

 lepideus, cited by Buller,^ Snell ^ and Humphrey ^ and isolated several 

 times from posts in the Gulf port, Mississippi, test plot,^ as well as 

 from poles in service, is used in all cases of organic preservatives, but 

 is seldom used against metallic salts, to which it is extremely sensitive. 

 Lenzites trabea, another species of great economic importance, Hubert,* 

 and also isolated several times from rotted southern pine poles, is 

 somewhat parallel in resistance to Lentinus lepideus, but produces a 

 markedly different type of decay. Polyporus vaporarius, Porta in- 

 crassata, and Coniophora cerebella, the common "dry rots," although 

 easily killed by many hydrocarbons, are resistant to most inorganic 

 compounds, and at least one of these organisms is included in each 

 test on such materials. Fomes roseus, another fungus of wide dis- 

 tribution, reacts in a most inconsistent manner, but its occasional 

 specific virulence is sufficient to warrant its inclusion in all assays of 



Fig. 10.^ — Assay of worthless preservative at maximum concentration. The 

 fungi in dupUcate from left to right are Lenzites trabea, U-10, Fomes roseus aiul 

 Leniinns lepideus. 



new and unusual preservatives. Unfortunately the fastest and most 

 versatile decay organism used has no name and masquerades under 

 the designation U (unknown)-lO. Isolated several years ago from a 

 decayed pine pole, the identity of U-10 is still a mystery, despite the 

 efforts of many mycological authorities. U-10 is included in every 

 test and is especially valuable when a quick indication of the value of 

 a new preservative is needed, as it is capable of producing an appreci- 

 able weight loss in about three months. In addition to the above 

 fungi occasional use is made of such common wood-destroyers as 

 Trametes serialis, Lenzites sepiaria, Polystictus versicolor, Polyporus 

 sulphureus, and Fomes pinicola. 



At the present stage of development this wood block method tells 

 nothing directly about the ability of a wood preservative to resist the 

 action of termites. Most materials which inhibit decay also prevent 



