DECAYS AND DISCOLORATIONS IN AIRPLANE WOODS. 29 
stain, and as far as is known no reduction in strength results. The 
fungus causing the discoloration is as yet unknown. 
Blue-stain is very severe on the white pines and is particularly 
noticeable because of their white wood. Plate I, left part, shows a 
section from a sugar-pine rib web in which the sapwood is stained 
to some extent. The small, darker, bluish black spots are the ends 
of the medullary rays, in which, as before stated, the fungous myce- 
lium is most abundant. The longer streaks are the resin ducts. 
Certain fungi (Penicillium spp.), stain the sapwood of the pines 
an orange-red to a crimson-red color. Another fungus (/usariwm 
vosewm Link) is responsible for a pink to lilac color in the same 
woods. The color is produced by means of a pigment secreted by 
the hyphe, which actually dyes the wood. 
A wood-staining fungus (Zythia resinae (Fr.) Karst.) has been 
reported in Europe (9) as working on finished pine lumber after 
the wood has been oiled. The discoloration was characterized by 
violet to dirty red or even dark grayish brown flecks beneath the 
oiled surface of the wood. The spots were covered with minute 
pustules varying from violet, orange, and brown to black. These 
constitute the spore-producing bodies. The discolored areas ex- 
tend within the wood as streaks closely associated with the medul- 
lary rays and resin ducts. The report does not state whether the 
discoloration was confined to sapwood. Apparently the wood was 
not reduced in strength. As far as is known, this stain has not yet 
been found in the United States. 
SAP-STAIN ON HARDWOODS. 
Hardwoods are not as subject to the stains caused by fungi as are 
softwoods. In hardwoods, when sap-stain does occur, the discolora- 
tion is most intense in the medullary rays and large pores or vessels. 
In a wood such as yellow birch, in which these vessels are not too 
closely crowded, the stain, if not too severe, appears in longitudinal 
section aS very narrow bluish black lines or streaks following the 
erain of the wood. This stain will not necessarily be confined to the 
surface layers, but may extend entirely through the sapwood. Of all 
the hardwoods, however, red gum seems to be the most susceptible 
to stains caused by fungi. 
BROWN-OAK DISCOLORATIONS. 
A somewhat different discoloration than those previously de- 
scribed, in that it is confined to heartwood only, is the “ brown oak” 
(78, 79) found in Great Britain. This is also known as “red oak” 
and “ foxiness,” but the name first given is most commonly accepted. 
Instead of the normal heartwood, certain trees of the common Euro- 
pean oak have a dull-brown to rusty brown or even rust color in the 
heartwood. In some cases the color is uniform, while again longi- 
tudinal streaks of normal-colored heartwood may alternate with 
those of the brown color. When these brown streaks contain black 
patches this type of wood is known as “tortoise-shell” oak. This 
discoloration originates in the heartwood of living trees, the normal 
heartwood changing first to a faint yellow color, which continues to 
deepen until the brown stage is attained. The color change is caused 
by a fungus, but so far as known the infected wood is not weakened. 
