104 College of Forestry 
layers of the wood prosenchyma elements are colored much 
less strongly than their middle lamelle and appear to be 
almost violaceous or violaceous tinged with red, especially in 
the terminal cells of the growth ring. When sections are 
treated with aniline sulphate-H.SO,, the vessel walls and the 
middle lamelle of all the cells stain golden yellow. The 
remaining layers of the medullary ray cells appear brownish- 
yellow. The secondary and tertiary ‘layers of the wood pro- 
senchyma elements stain much lighter than their middle 
lamellze, becoming a pale lemon color. 
From the tests described above in full detail, and from still 
other tests emploved for the differentiation of both cellulose 
and lignin, it is evident that the vessel walls are lignified 
to a much greater extent than any other one element except- 
ing the multiseriate pith-rays. Of the individual cells, the 
middle lamellee are lignified far more strongly than the sec- 
ondary layers. The ‘secondary layers of the wood prosen- 
chyma elements, therefore, are the least strongly lignified 
tissues of the wood. The lignification of these elements, how-— 
ever, increases markedly on the outer face of the growth ring. 
As a result of the dissimilar structure and the microchemical 
reactions of the various elements, we naturally would expect 
to find that the vessel walls and the broad medullary rays 
would resist decay longer than any other element. Of the 
other elements the middle lamelle would be more resistant 
to the solvent action of the fungus than the secondary layers 
of thickening possessed by these respective elements. We 
also would expect to find that the terminal margin of the 
growth ring would resist decay longer than the remainder 
of the growth ring. When it is understood that the first 
result of the decay caused by this fungus is the delignifica- 
tion of the woody substance, it would be expected that those 
elements which are strongly lignified (the vessels, medullary 
rays, and the terminal cells of the growth ring) will resist 
destruction far longer than the less lignified elements (the 
wood prosenchyma). 
Macroscopic Appearance of Decayed Wood.— The decay 
of sugar maple wood is very similar to that of yellow birch, 
