138 College of Forestry 
nified throughout but at the same time they are lignified to 
a much greater extent than the middle lamell of the other 
elements. In the case of hemlock, however, most of the ele- 
ments being uniform in structure, they decay at approxi- 
mately the same rate. 
The mycelium exhibited essentially the same relation to 
each of the woods studied. In the early stages of the decay 
of dicotyledonous woods the larger hyphz tend to extend 
themselves in the direction that offers the least resistance. 
As a result of this tendency they extend longitudinally, fol- 
lowing mainly the lumina of the various elements, particu- 
larly the vessels. When medullary rays are reached the 
hyphe frequently branch off and enter them. ‘The vessels 
often become filled with dense plugs or matted growths of 
fungal hyphe. These mats of hyphe are brown by reason 
of being incrusted with decomposition products. The latter 
are partially soluble in 5 per cent KOH and entirely soluble 
in warm nitric acid. In general the majority of the hyphe 
elongate horizontally in the direction of the majority of the 
elements, during the earlier stages of the decay. In the later 
stages of the decay, however, the mycelium branches pro- 
fusely and grows in all directions, perforating the walls of 
the woody elements at random. As the hyphe continue to 
branch and multiply beyond the ordinary conception they 
permeate the woody substance in all directions and are 
thereby enabled to slowly dissolve the woody substance by 
means of their enzyme excretions. The hyphz observed in 
the wood, as a general rule, are exceedingly fine and minute, 
rarely being over two microns wide and usually much less. 
Cross-walls and clamp connections are discernible occasion- 
ally in the larger hyphe. In the course of the decay the 
hyphee seem to disappear from the wood as soon as the decay 
of any one portion becomes completed. Numerous holes 
occur all through the wood indicating where the hyphe had 
passed through the cell-walls. The threads exhibit no par- 
ticular preference for the pits but penetrate the cell-walls at 
will. In those woods (sugar maple, bitternut hickory, and 
chestnut oak) which contain abundant crystals of calcium 
