WOOD SOIL CONTACT CULTURE TECDNIQUE 



109 



with the moistened soil. Two pieces of southern pine sapwood "feeder 

 strips" (3.5 X 2.0 x 0.3 cm.) arc placed on the soil in each bottle, Fig. 3. 

 The bottles are closed tightly with screw caps and then autoclaved for 30 

 minutes at 15 pounds' pressure. When the bottles have cooled, a small 

 inoculum (a few millimeters square) cut from a pure culture of a suitable 

 wood-destroying fungus is placed on the sapwood substrate. Each bottle 

 contains a single dominant fungus culture. It is best to use at least four to 

 eight selected species of fungi for an assay. The bottles are again capped 

 and placed in an incubator, or a controlled temperature room, held at 26°- 

 28°C., for at least one month. Any contaminated or weak cultures are 



UNTRtATEO WOOD 



FEEDER STRIPS'* 'f^^ 



Fig. 3 — Schematic diagram of wood soil contact method 



discarded. This completes the preparation of the pure fungus cultures, 

 Fig. 4, and they are n6w ready to receive the test blocks. 



To each bottle containing a culture established on sapwood substrate 

 are added an untreated control block and a block treated with a preserva- 

 tive according to the following method: 



The required number of f " cubes of sapwood blocks are placed in a humid- 

 ity chamber at 30°C. and 76% relative humidity until the blocks have 

 reached a constant weight. Then the necessary number of weighed blocks, 

 weighted to ensure immersion, are placed in a container of convenient size 

 under a bell jar fitted with a separatory funnel. After evacuation of the 

 bell jar to a pressure not greater than 2 cm. as measured by a mercury man- 

 ometer, the vacuum is held for 5 minutes. The stopcock in the pump line 

 is then closed, and sufl&cient solution is admitted from the separatory funnel 



