20 



Wherever a hypha has passed through a wall is to be found the peculiar 

 double spiral crack. (PL IX, fig. 1.) 



The diseased wood of the Balsam Fir differs little from similarly 

 affected Spruce wood. The summer tracheids as a rule are not so wide 

 as those of the Spruce, hence the spiral cracks are not as evident as in 

 that tree. The}^ appear to extend more or less parallel with the walls. 

 The}^ are likewise present in greater numbers, so that there is very 

 little left of the wall. 



Wood which is in the last stages of deca}^ is exceedingh^ brittle. It 

 does not partake of the character of brown charcoal as much as does 

 Pine wood similarly diseased, but is much firmer. It absorbs water 

 very rapidly, and when boiled in water for a few minutes becomes soft 

 and putty like and can be kneaded like bread dough. When dry it 

 can not be cut with a knife without crumbling, but when soaked in 

 water it can be readily cut into the thinnest sections. These have no 

 elasticit}^, however. The walls of the wood cells are very thin and 

 swell to several times their size on addition of dilute potash. Here 

 and there are found masses of resin, more frequently in the Balsam 

 Fir than in the Spruce. As the wood grows older the action of the 

 mycelium seems to stop. The wood changes no further except that it 

 cracks more or less. It appears to be very resistant to change brought 

 about by weathering. 



FRUITING ORGAN. 



The first fruiting bodies observed began to appear toward the begin- 

 ning of July. Small rounded masses grew out from the bark and very 

 soon became flattened horizontally. The specimen shown in the photo- 

 graph (fig. 1) was watched closely and measured daih^ from the time 

 of its first appearance until it had reached its full size. By means of 

 wires stuck at the edge of the growing shelves, it was easy to measure 

 accurately the daily increase in diameter. The hyphee rapidly grew 

 around the wire so that it became embedded in the mass of the sporo- 

 phore. One of the wires is visible at the right side of the middle shelf 

 of fig. 1. The measurements show that for the first two weeks the 

 larger shelves grew about one-fifth of an inch (one-half centimeter) a 

 day in all directions; on warm days, however, the increase was more 

 than that and on other days not so much. The 3^oungest portion of the 

 sporophore was yellow-brown, which in three or four days deepened 

 to a red brown. The unequal dcA^elopment of the mass caused concen- 

 tric rings to appear on the top of the pile us, showing b}^ the low ridges 

 and shallow furrows, respectively, where any particularly rapid growth 

 had set in and where it had stopped. On August 15 the growth in 

 width suddenl}^ stopped. When full grown, the largest of the three 

 shelves was 10 inches (40""") across at the widest point and 8 to 14 

 inches (20 to 35"™) from front to back. 



