128 College of Forestry 
wood after treatment with various microchemical reagents 
reveals the action of the fungus. 
In sections of decayed wood narrow, irregular zones of 
wood, in which the cell-walls respond to lignin tests as 
strongly as they do in normal wood, separate the pockets or 
decayed areas. Bordering on these cell-walls, which react 
the same as those of sound wood, are other cells in all stages 
of decomposition. The cell-walls of the decayed wood become 
colored variously, the coloration assumed corresponding with 
the degree of decay exhibited by the cell-walls. Those walls 
remaining but little or not at all decayed color the same as 
those in the sound wood. In other parts of the sections the 
tertiary layer —that portion of the cell-wall which borders 
upon the lumina of the cells — fails to take on the charac- 
teristic coloration or at least becomes stained only shghtly, 
thus indicating the beginning of delignification. In _ other 
groups of cells both the tertiary and secondary layers of the 
cell-wall fail to take on the characteristic coloration to any 
appreciable extent. This indicates a more advanced stage of 
the decay and consequently the delignification. 
The lay ers of the cell-walls that remained colorless after 
treatment with lignin reagents become colored violet when 
treated with cellulose reagents such as chlorzinc-iodine. In 
some cells only the tertiary lamella colors violet, the second- 
ary and primary lamellze becoming brown. In other cells 
only the middle lamella colors brown, both the secondary 
and tertiary layers becoming violet. Sections from a number 
of blocks of decayed wood were examined to see if any swell- 
ing of the cellulose layers occurred after treatment with 
chlorzinc-iodine. In the material ex xamined, however, but 
little or no swelling of the delignified layers of the cell-wall 
could be detected after treatment with this reagent. The 
middle lamelle retain their lignified nature long after the 
complete dissolution of the secondary and tertiary lamellee 
of the respective cells. After the dissolution of the other 
layers of the cell-wall the middle lamellze do not remain intact 
as long as those of yellow birch. Soon after the destruction 
of the tertiary and secondary layers the middle lamellee 
