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lignified cell-walls, light-green (methyl green); delignified cell-walls or 
cellulose, brownish red (congo red); and middle lamella, light-red (ruthe- 
nium red). The dark color of the large vigorous hyphae when advancing 
into healthy tissue is natural. In the cross-sections, OBSERVE :— 
25. The dense growth of the large dark-colored hyphae making 
up the black line. At this point the fungus is advancing in a solid line 
toward the sap-wood. DRAw a few cells included in the black line, detail- 
ing the hyphae. 
26. The scattered areas, especially around tracheae and in the 
medullary rays, where the same dark-colored hyphae are found. How do 
these centers of decay originate ahead of the general advance? Cor- 
roborate your answer by two DRAWINGS; one diagrammatic, showing 
the relation between the black line and the advanced centers of decay; 
the other detailed, showing the actual cells. 
_ 27. The accumulation of green-staining material around the cells 
newly invaded. What does this indicate? 
28. The delignification of the cell-walls near the advanced 
centers of decay. Do the hyphae of the fungus have to be in contact 
with a cell-wall to cause its delignification? Proof? How is the delignifi- 
cation brought about? Detail answers in DRAWINGS. 
29. The character of sound maple wood; elements present and 
thickness of the walls of different elements. Make a prawinc of healthy 
maple wood showing an annual ring with all elements properly arranged 
and detailed. Label fully. 
30. The characters of the decayed wood some distance inside 
the black line, noting changes in the elements. Make a prawine of the 
decayed maple wood showing the same elements as in healthy wood. 
Label fully and bring out all changes brought about by the decay-process. 
Study the longitudinal sections and OBSERVE :— 
31. The mycelium advancing into healthy tissue. 
32. The change brought about by the decay-process inside the 
black line as compared with the healthy tissue outside. Make DRAWINGS 
of healthy and decayed maple wood, contrasting the conditions as seen in 
the longitudinal sections of each. 
REPORT 
1. Compare and contrast the decay-process caused by F. 
igniarius (L.) Fr. in maple with that caused by T. Pinz Fr. in spruce. 
