26 BULLETIN 1128, U. S. DEPARTMENT OF AGRICULTURE. 
ingly favorable for the development of wood-staining and wood- 
destroying fungi during the spring and summer months. It is from 
this region that the three most important airplane woods—Sitka 
spruce, Douglas fir, and Port Orford cedar—are obtained. 
Wood containing very severe sap-stain therefore should be care- 
fully examined for the presence of wood-destroying fungi. If de- 
cayed, the wood will be brash and may be softer and less tough 
when the fibers are picked with a knife. If any doubt exists after 
an inspection, the decision should be based on a microscopical ex- 
amination or a mechanical test by a qualified expert. 
The most important of these stains from an economic standpoint 
is blue-stain, caused by various species of Ceratostomella, which may 
be found on almost any hardwood or softwood. Softwoods are 
more commonly affected, and certain species are particularly sus- 
ceptible. This is due both to the character of the wood and to the 
climatic conditions of the region where the species occurs. The 
discoloration may be more or less superficial, occurring as spots or 
streaks. If the staining is severe, however, the entire sapwood will 
be affected, so that it can not be surfaced off. The fungi causing 
these stains are not readily seen, but sometimes if a deeply stained, 
almost black piece is inspected with a hand magnifying glass, in- 
numerable bristles with a bulbous base will be observed. ‘These are 
the fruiting bodies, containing an enormous number of spores, which 
are exuded and are carried about by air currents. Falling on green 
sap lumber they sprout, the hyphe develop, and more blue-stain re- 
sults. Under favorable conditions blue-stain may develop with sur- 
prising rapidity, appearing on lumber within a day after sawing. 
Other colors, such as black, brown, gray, red, pink, and violet, are 
caused by species of Hormodendron, Hormiscium, Graphium, Pen- 
icilhum, and Fusarium. These discolorations are not nearly so 
common as blue-stain. 
Certain other discolorations of sapwood are produced by fungi be- 
longing to the molds, of which the green mold on fruits or in certain 
cheeses is an example. Usually such stains: are superficial and 
readily surface off. They occur on both hardwoods and softwoods. 
The bluish or blackish stains are difficult to separate by visual inspec- 
tion from the true blue-stain. 
CONTROL. 
Considerable study has been devoted to the development of methods 
of prevention and control of sap stains caused by fungi (1, 25, 72). 
Naturally most of this work has been concentrated on blue-stain, 
and the following paragraphs are most directly applicable to it, but 
will probably also apply fairly well to the others. Blue-stain may 
be checked after it has started. but the stain can not be eradicated 
unless it is so superficial that it can be planed off. Therefore, the 
keynote of all treatments must be prevention. : | 
Unfortunately, there is no one principle that can be applied to the 
prevention of this discoloration. Staining may take place at any 
time after the trees are felled or, in the case of dead timber, while 
they are still standing. Hence, in logging operations in regions 
where blue-stain is of importance, the logs should be removed from 
the woods as soon as possible after the trees are felled and bucked 
