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 l)ark of the living pine tree by the bark and wood- 

 boring })eetles. The atmosphere of these holes is constantly kept 

 moist l)y 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- 

 nioht. The hyphw 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 hyphfe 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 hypha? 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 (PI. VII, 1 and 2: PI. VIII, figs. 1 and 2), so 

 that in a very short time the entire ray is filled with the hypha?, 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 hyphfe 

 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, hyphsB several microns in diameter may be 

 formed (PI. VII, 2). These are constricted at the septa and show signs 

 of rapid development. The older hyphfe turn brown, and with the 

 first signs of the brown color in the hypha? the bhiish coloration of 

 the wood begins. One of the first efiects seen after the hyphae have 

 entered the medullary ray cells is the gradual solution of the walls 

 separating the medullary ray cells from one another (PL 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 middle ray 

 (PL VII, 1), but they are rarely dissolved entirely. The intermediate 

 walls, on the other hand, entirely disappear. This leaves a tube with 

 a cross 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 hypha?, the larger number of which 

 extend in the direction of the ray (PL VIII, figs. 1 and 2). From the 

 ray cells some hyphfe make their way into adjacent wood cells (PL 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. 



