6 BULLETIN 1037, U. S. DEPARTMENT OF AGRICULTURE. 
He found that when 1 by 3 by 6 inch boards of alder (Alnus incana 
Moench), white or gray birch {Betula populifolia Marsh), paper 
birch (Betula papyrifera Marsh), and various trees belonging to the 
rose, family (Rosacea?) were immersed in boiling water and then 
stacked under cover they would remain unchanged in color. Those 
boards which had been immersed in the boiling water and then 
placed in the most unfavorable conditions of high humidity and 
temperature in the open and exposed to the direct rays of the sun 
scorched on the surface. With the exception of this superficial 
scorching, no discoloration of the wood took place. On the other 
hand, untreated boards that had been cut from the same portion of 
the tree and subjected to similar conditions of temperature and 
humidity stained rapidly. Bailey (5) found that the rapidity and 
the depth to which the stain penetrates the wood varies with the 
temperature and the moisture, hot and humid weather being espe- 
cially favorable for the production of stain. From a consideration 
of the results obtained, he concludes that sap-stain caused by oxidiz- 
ing enzyms can be readily prevented by dipping the timber for a few 
minutes in boiling water. 
Though chemical stains give more or less trouble in kiln-dried 
maple flooring and sugar-pine lumber, the discol orations may be 
prevented to an extent by the use of comparatively low temperatures 
(120° to 125° F.) and correspondingly low humidities (50 to 70 per 
cent: Tiemann, 57, p. 185). Because of their limited distribution 
and the fact that they do not impair the strength or durability of the 
timber, chemical stains in general can hardly be considered as having 
very great economic importance. 
FUNGOUS STAINS. 
The second class of stains is produced by fungi. These fungi are 
disseminated by means of minute bodies known as spores. The 
spores may be produced in countless numbers and are blown about 
by the wind, washed along by the rain, or carried by animals, 
particularly insects. When, under favorable humidity and tem- 
perature conditions, they happen to lodge upon a substratum, such 
as the moist green sapwood of woods that contain the requisite food 
material, the spores may germinate and give rise to a mass of fine, 
usually septate threads, sometimes colorless at first, but often becom- 
ing darkened with age. This vegetative portion of the fungus is 
known as the mycelium, and the individual threads are called hyphae. 
In some cases the hyphae probably penetrate the wood but little, 
growing for the most part over the surface; in others, they may enter 
the sapwood through the medullary or pith rays. This does not result 
in the disintegration of the walls of the wood cells to any appreciable 
