496 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
3. The Last Stage of Decayed Wood. The color of the most badly 
decayed wood remains the same as that of the less decayed stuff, but there 
is a difference in its texture. Instead of the wood being soft and easily 
cut without breaking, it has now become very dry and friable and is easily 
crumbled between the fingers. It cannot be cut without breaking. In 
addition, white streaks appear at frequent intervals in the vertical sections, 
and upon examination these are found to be pure wood fibers, containing 
very little lignin. These streaks are present in only the very final decay 
of the tree. The borer channels are not visible, being choked with old masses 
of mycelium which closely resemble in color the decayed wood. The 
contents of these channels have a rubbery consistency and are in the form 
of pellets. The mass of decay holds together fairly well, but would crumble 
away in time and thus cause a hollow interior. 
The rotted portion of a section taken near the base appeared like a 
star in outline, or as if some powerful acid had been spilled over the section 
and had changed the texture of all the wood with which it had come into 
contact. The dark border ring was not very distinct in this section hori- 
zontally, but could be seen very well on the longitudinal portion. At a 
few points, the fungus became powerful enough to break through the sap- 
wood and cambium in order to form fruiting bodies, and here the decayed 
wood appears a darker brown, of soft, friable texture. 
Microscopic Characteristics of Fungus and Host Tissue 
The tree was cut up and eight sections were selected for study. These 
are shown in the diagram of the tree (fig. i). 
Before much work was done on the actual course of the fungous hyphae 
in the cells, quite a bit of time was spent in the laboratory in preparing 
free-hand sections of sound wood, partially decayed wood, and badly 
decayed wood. These sections were both radial and tangential and were 
taken from section I (see fig. i). These sections were stained with chlori- 
odide of zinc for cellulose reactions and with phloroglucin and hydrochloric 
acid for lignin reactions. These tests were later confirmed by the use of 
eosin and also of congo red, the latter as a cellulose test. The best test for 
cellulose and lignin, aside from chloriodide of zinc, and phloroglucin and 
HCl, was that of haematoxylin for cellulose and safranin for lignin. In 
the case of the haematoxylin, the Heidenhain method was the best.^ Finally, 
1 The sections were washed in distilled water and then immersed in a 2 percent solution 
of iron alum. They were left in the iron alum for about five minutes and then washed 
twice in distilled water, care being taken to get all the free alum out of the sections before 
transferring them to the haematoxylin. When this had been accomplished, the sections 
were transferred to a 1/2 percent solution of haematoxylin and allowed to remain for a 
minute or two. They were again washed and then transferred to a i percent solution of 
safranin, made up of equal parts of alcohol-soluble and water-soluble safranin. The result 
was a blue for the cellulose and a red for the lignin. The sections can be left for any length 
of time in the safranin. 
