116 BELL SYSTEM TECHNICAL JOURNAL 



permanent. This constancy of the volume during the decay period indi- 

 cates the mechanism by which the water is held practically constant during 

 the decay period. Any loss of water would result in a shrinkage from 

 which there would be no recovery. 



Table 1 gives a list of the solutions used to moisten the artificial soil and 

 the average weight loss for 3 blocks in percentage for each variation. Several 



Table 1 



Effect on the Decay of Wood in Contact With Sand and Fuller's Earth 



Mixtures Moistened with Various Nutrients and Nutrilites 



Organism Poria Incrassata. Time 12 Weeks 



Solution Used to Moisten Artificial Soil 



Top Soil (Control) 



M.S.* + 0.2% Ammonium Nitrate + 1% Maltose + Vitamins Bi, 



Be and Biotinf •• 



2% Malt Extract 



M.S. + 2% Ammonium Nitrate + Vitamins 



M.S. + 2% Ammonium Nitrate 



M.S. -j- Various Combinations of VitaminsJ 



Distilled Water : 



M.S. + Vitamins + 1% Maltose .-,'■ 



M.S. + 1% Maltose 



Average Weight Loss in 

 Per Cent Due to Decay 



67.0 



62.7 

 59.3 

 51.3 

 47.9 

 29.1 

 28.4 

 11 6 

 12.9 



* M.S. = mineral solution containing the following minerals: 



Potassium Dihydrogen Phosphate 1.5 grams per liter 



Magnesium Sulfate 1.0 gram per liter 



Copper 0.02 parts per million 



Manganese 0.01 parts per million 



Boron 0.005 parts per million 



Iron 0.10 parts per million 



Molybdenum 0.10 parts per million 



Zinc 0.09 parts per million 



t The vitamins used and the concentrations per liter were as follows: 



B^ 0.1 milligrams per liter 



Be 0.1 milligrams per Hter 



Biotin 0.02 milligrams per liter 



X The vitamins were added singly and in the following combinations: 



Bi + B« + Biotin — Concentration of each vitamin as Hsted above. 



B, + Be 



Bi + Biotin 



Be + Biotin 



conclusions may be drawn. It is evident that the soil greatly accelerates 

 decay, and that the soil extract contains a large portion of the nutrients 

 and nutrilites which accelerate decay. Malt extract, which contains 

 proteins and sugars, and the mineral solution fortified with ammonium 

 nitrate also stimulate decay. The effect of nitrogen in increasing decay 

 confirms the experiments made by Schmitz and Kaufert,^^ 1936. When 

 nitrogen is lacking and a simple sugar is present, the fungus consumes the 

 simpler sugar instead of the more complex carbohydrate cellulose. This 

 preference is not evident if sufficient nitrogen is present since both carbohy- 



