﻿24 BULLETIN 1128, TJ. S. DEPARTMENT OF AGRICULTURE. 



logs sometimes have a decided brownish red stain on the sapwood. 

 This is of no importance, because it does not occur on sawed lumber 

 except so faintly as to be almost invisible. 



A very unsightly discoloration known as brown-stain (43, p. 

 305-307), which, however, does not weaken the wood, often occurs 

 on sugar pine, but is frequently not noticeable until the lumber has 

 been finished. This appears in the sapwood as a streaky, dirty, light 

 to dark brown or brownish black discoloration, and may be super- 

 ficial or very deep. It is quite striking against the faint yellowish 

 white sapwood in finished lumber. The discoloration occurs on 

 green sap lumber upon exposure to the air and may appear during 

 air drying or kiln drying. In the last instance it is known as kiln 

 burn, but it does not differ from the brown-stain and is probably 

 sometimes due to defective circulation in the kiln. Brown-stain is 

 particularly bad in lumber cut in early spring. Hot, humid weather 

 and poor circulation of air in the lumber piles favor the staining, 

 while cool, dry weather and proper piling tend to prevent it. This 

 brown stain is an oxidation process similar to the others, but whether 

 it can be prevented by the hot- water treatment is doubtful, since the 

 discoloration often extends deeply into the lumber. 



The wood of sugar pine in dead trees, standing or down, may be 

 affected by a very brilliant orange stain which occurs in spots or as 

 a solid color, but more often is seen as narrow to broad streaks 

 parallel to the grain of the wood. It is found in both heartwood 

 and sapwood. The exact cause of this discoloration is unknown, but 

 it is probably the result of chemical reaction, since no fungous 

 mycelium has been found associated with it. While the wood is 

 apparently not weakened, the presence of this stain indicates that 

 the lumber came from dead trees, and it should be closely watched 

 for signs of decay and insect borings. 



DISCOLORATIONS CAUSED BY FUNGI. 



From an economic standpoint by far the most important discolora- 

 tions in wood are caused by fungi. Fungi are very simple plants 

 which can not live on the simple food elements of the soil and air 

 and build up complex organic matter, as is done by the green plants 

 with which we are familiar, but must have organic matter already 

 prepared in order to sustain life. This they find in the material 

 built up by green plants; hence they may attack living plants, or 

 dead portions of such plants, or any dead vegetable matter. Some 

 live on animal matter, but these do not concern us. The develop- 

 ment of fungi is dependent upon a supply of oxygen, of which there 

 is always sufficient in the air, a certain degree of moisture, a suit- 

 able range of temperature, and the necessary food substances. The 

 maximum and minimum of these requirements vary widely with 

 different fungi. 



The fungous plant consists of very fine threads (hyphse), which 

 are invisible to the naked eye unless they occur in mass. Individual 

 hyphse require magnification by a compound microscope. Collec- 

 tively, the hyphse are termed mycelium. The hyphse usually live in 

 the tissues of the substance on which the fungus is growing. The 

 fruiting bodies or sporophores, which vary in size from those so small 

 as to be invisible to the naked eye except in a mass to others quite 



