Bul. 1262, U. S. Dept. of Agriculture. PLATE V. 
CULTURE TUBES SHOWING NEGATIVE AND POSITIVE RESULTS. 
A, Culture tube showing a negative result; no fungous growth has developed from the fragment 
of wood. The white area on the surface of the agar is due to reflections of light. B, Culture 
tube showing a positive result: the fungus has grown from the fragment of infected wood, and 
a small sporophore ( Pholiota adiposa) has developed. 
