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 iSchrenk, ^1) and later at 

 the Forest Products Laboratory, Madison, Wis. (Weiss, 56 \ Weiss 

 and Barnum, 67) 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 (i7, p. 66) ascertained that it arises 

 from the presence of the brown fungous hyphse in the intercellular 

 spaces. According to Von Schrenk (4^i, 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 (4-/, 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 Avhose color is trans- 

 mitted by the wood cells of the pine more readily than the brown 

 color." Miinch {31^ P- 3) concludes that the color is due to the ar- 

 rangement of the mycelial threads in the wood. He cites, as some- 



