18 THE ‘‘BLUING’’ AND THE ‘‘RED ROT” OF THE PINE. 
The growth and development of the fungus may be briefly noted as 
follows:“ The spores of the ‘* blue” fungus (Pl. VII, 8) are probably 
blown about by the wind in countless thousands, and at the time of the 
beetle attack in July and August some of these spores lodge in the 
holes made in the bark of the living pine tree by the bark and wood- 
boring beetles. The atmosphere of these holes is constantly kept 
moist by the water evaporating from the trunk. In these holes the 
spores can germinate within a day after falling there. 
In drop cultures of pure water the spores germinate readily over- 
night. The hyphe grow into the bark tissues and into the cambium, 
and from there they enter the cells of the medullary rays. The readi- 
ness and rapidity with which the hyphe grow into the medullary rays 
lead one to suspect that the food substances, stored in the medullary 
rays at this period of the year in considerable quantities, exert a 
chemotropic stimulus. In the early stages of development one finds 
the hyphe of the ‘* blue” fungus only in the medullary ray cells. After 
a hypha has entered one medullary ray cell it branches and spreads to 
the neighboring cells (Pl. VII, 1 and 2; Pl. VIII, figs. 1 and 2), so 
that in a very short time the entire ray is filled with the hyphe, most 
of which grow in the ray toward the center of the trunk. Numerous 
starch grains are usually found in the ray cells during the early part 
of August; these are rapidly dissolved by the fungus and serve as a 
source of food supply for a considerable period of time. The hyphe 
are at first colorless, very thin-walled, and full of vacuoles and oil 
globules. They branch rapidly, forming numerous septa. If the 
starch supply is abundant, hyphee several microns in diameter may be 
formed (Pl. VII,2). These are constricted at the septa and show signs 
of rapid development. The older hyphe turn brown, and with the 
first signs of the brown color in the hyphe the bluish coloration of 
the wood begins. One of the first effects seen after the hyphe have 
entered the medullary ray cells is the gradual solution of the walls 
separating the medullary ray cells from one another (PI. VII, 1, 2, 
and 3). The walls which separate the ray cells from the neighbor- 
ing wood cells may become very thin, as shown in the middie ray 
(Pl. VII, 1), but they are rarely dissolved entirely. The intermediate 
walls, on the other hand, entirely disappear. This leaves a tube with 
across section having the shape of the cross section of the ray, extend- 
ing into the trunk from the bark. This tube is sometimes filled 
entirely with a mass of brown hyphe, the larger number of which 
extend in the direction of the ray (Pl. VIII, figs. 1 and 2). From the 
ray cells some hyphe make their way into adjacent wood cells (PI. VII, 
2; Pl. VIII, figs. 1 and 2). They grow along these, both up and down 
«A fuller discussion of its cultural characteristics, spore germination, and the blue 
color will be printed at a later date. 
