266 



Mycologia 



" stringy rot." As will be brought out later, the bands of wood 

 remaining are the areas of summer wood, which probably be- 

 cause of its compactness is not so easily destroyed. The 

 elongated cavities represent the spring wood that is destroyed 

 long before the summer wood disappears. It is evident that this 

 separation of spring and summer wood results in the formation 

 of concentric rings in the wood. These rings do not coincide 

 entirely with the annual rings but the annual rings are split into 

 their two growth areas, spring and summer wood. Consequently 

 it is often possible to separate blocks of rotted wood into con- 

 centric slabs, although the persistence of groups of vertical 

 tracheids bound together by ray tracheids aids in holding these 

 concentric rings together. 



In addition to the above characteristics, the rotted wood may 

 be described as soft and watery in texture when found in the 

 woods. It is quite flexible and readily separates into narrow 

 strings or strands when twisted, often giving a rough broom-like 

 appearance. When dry the well rotted wood is brittle and 

 snaps under slight pressure. No concentric or other cracks due 

 to shrinkage are present as are found in some rots (e. g., that 

 caused by Polyporus sulphur eus, P. borealis, etc.) Neither are 

 sheets of mycelium ever developed in the cavities that appear. In 

 rare cases small strands of mycelium may appear just under the 

 bark or in the very rotten wood. No spots or colored lines of 

 any sort are present in the decayed wood. 



Microscopic Characters of The Decayed Wood 



The wood of pitch pine is made up of two elements, i. e., 

 vertical tracheids and medullary rays. The vertical tracheids 

 have a single row of bordered pits on the radial walls. Con- 

 sequently the radial section alone will show these pits in surface 

 view. When the lignin and cellulose tests 3 are applied to the 



3 The lignin test found most serviceable was the phloroglucin test with 

 hydrochloric acid. Free hand sections of the wood were first treated with a 

 two per cent, solution of phloroglucin in 95 per cent, alcohol. This was 

 immediately drained off and a drop of rather strong HQ added. The result 

 was a beautiful red color assumed by all lignified membranes. 



The best cellulose test was found to be the reaction with chlor-iodide 

 of zinc solution made up as recommended in Steven's Plant Anatomy. If 



