To determine the toxic value of the precipitated sulfur, the follow- 

 ing series of experiments was performed. A common wood-destroying 

 fungus, Stereum hirsutum, was used to test the toxicity of the preservative. 

 This fungus is a facultative parasite, growing in either living or dead 

 wood tissue, usually the latter. It grows remarkably well on artificial 

 media as was demonstrated in the course of the experiment. The plan of 

 the experiment was to find the medium upon which the fungus would 

 grow most vigorously, then to make up a series of mixtures of this nutrient 

 material with varying percentages of precipitated sulfur. Sterile slant 

 tubes were made of these different mixtures, the fungus transferred to 

 them, and the resulting growth of the mycelium taken as an index of the 

 toxic value of the sulfur. For the purpose of comparison cultures of the 

 fungus were made on the nutrient material alone and also on a mixture 

 of this material with coal-tar creosote. These were treated in exactly 

 the same manner as were the sulfur mixtures of the media. The medium 

 upon which the Stereum grew most vigorously was determined by detailed 

 experiment to be a mixture of agar-agar with a tea made by boiling in 

 water the sapwood and cambium of Alnus and Salix. The fungus not 

 only produced a vigorous vegetative growth on this substratum, but under 

 the most favorable conditions produced sporophores, both on its surface 

 and on sticks placed in the medium. A number of mixtures of the 

 nutrient material with sulfur were made in test tubes, and in flasks of 

 one half litre, litre, and two-litre capacities. The following 



CULTURE OF STEREUM HIRSUTUM, CONTAINING HL.OCK OF WOOD 

 IMPREGNATED WITH AMMONIUM POLYSUL.FIDE 



47 



