The Biology of Polyporus Pargamenus Fries 107 
few adjoining cells may be the only elements left of the 
a tissue of the erowth ring lving between the pith-rays. 
(Plate XXIII, Fig. 2.) 
Longitudinal sections of decayed wood showed a great 
abundance of matted growths of fungal hyphe which, in 
addition to occluding the vessels, often extended across a 
great number of elements, sometimes forming veritable zones 
through the wood. As in the decaying yellow birch wood, 
these mats of hyphze appear to be encrusted with brown 
decomposition products. 
The fungal hyph apparently did not exert any solvent 
action on the crystals of calcium oxalate which were of occa- 
sional occurrence in the chambered wood parenchyma cells, 
since they remained intact despite the complete decay of the 
cells containing them. 
Sections (taken near the black zones) of wood in the early 
stages of decay, exhibited considerable quantities of decom- 
position products infiltrating various portions of the wood. 
These decomposition products were most abundant in the 
vessels where they appeared as individual brown globules 
or more often a number of globules had coalesced into a 
brown, gummy mass completely occluding the vessels in a 
number of places. 
These brown, gum-like masses dissolve slowly and without 
heating when allowed. to stand in a 5 per cent solution of 
potassium hydroxide for a few hours. 
Tue Decay or Birrernut Hickory Woop. 
Structure of Normal Wood.— The wood of the bittermut 
hickory | Hicorta minima (Marsh.) Britton], is heavy, hard, 
moderately strong, and tough, but is not durable in the 
‘ground or if exposed; the sapwood especially is always sub- 
ject to the inroads of boring insects and fungi. The sapwood 
is white and character stically narrow; the heartwood is of a 
reddish nut-brown color. The pith-rays are abundant but 
not conspicuous. The wood parenchyma is arranged in fine 
tangential lines which do not appear as distinct as the rays. 
