SAP-STAIN, MOLD, AND DECAY IN GREEN WOOD. 11 
exist in such woods it is difficult to state whether they are due to 
dissimilarities in mechanical structure^ to the relative proportions of 
contained air and water, or to the variety and amounts of stored food 
present in the wood parenchyma and medullary rays. It is probable 
that differences in environmental conditions, i. e., temperature and hu- 
midity as affecting the growth of the fungi, are important factors 
directly responsible (Roth, 35, p. 55-56). 
STRENGTH OF " BLUED " WOOD. 
Since the wood fibers are not appreciably impaired by the growth 
of the blue-stain fungus, there should be no apparent loss in the 
strength of the invaded wood. Rudeloff (36) found that the compres- 
sion strength of pine is not affected by the presence of bluing fungi. 
Tests on the stained wood of western yellow pine conducted at Wash- 
ington University, St. Louis, Mo. (Von 'Schrenk. J^.1) and later at 
the Forest Products Laboratory, Madison, Wis. (Weiss, 56; Weiss 
and Barnum, 57) proved that there is practically no diminution in 
the end compression or cross-breaking strength and hardness of the 
stained as compared with the unstained wood. In the case of heavily 
stained shortleaf pine, however, tested at the latter institution, there 
was found to be a slight decrease in the strength, toughness, and 
hardness as compared with unstained wood having the same moisture 
content. It may be safely stated that blued wood is practically as 
strong as unstained wood. 
CAUSE OF THE COLOR IN "BLUED" WOOD. 
The cause of the blue color in the wood has never been • satisfac- 
torily explained. R. Hartig (17, p. 66) ascertained that it arises 
from the presence of the brown fungous hypha? in the intercellular 
spaces. According to Von Schrenk (1^1, p. 18, 25-26), it appears in 
the wood when the colorless mycelium begins to take on the brown 
hue characteristic of the mature fungus. Microscopic examination 
of the wood fibers taken from the blued wood reveals no indication 
of a blue color. While extracts of the blue wood with alcohol, ether, 
benzol, chloroform, alkalis, and acids differ in appearance from 
those obtained from clear wood, yet no blue tinge is apparent. Von 
Schrenk (Jfl, p. 26) suggests that possibly " there is some pigment 
with a blue element in the 'blue ' wood which is so faint that its de- 
tection in thin microscopic sections becomes almost impossible." 
Hedgcock (19, p. 110-111) states that " the brown color of the fungus 
apparently contains traces of a blue pigment whose color is trans- 
mitted by the wood cells of the pine more readily than the brown 
color." Munch (31, p. 3) concludes that the color is due to the ar- 
rangement of the mycelial threads in the wood. He cites, as some- 
