10 BULLETIjST 1037, U, S. DEPARTMENT OF AGRICULTURE. 



leaves a tube, with a cross section having the shape of the cross sec- 

 tion of the ray, extending into the trunk from the bark. This tube 

 is sometimes filled entirely with a mass of brown hyphse, the larger 

 number of which extend in the direction of the ray (PL I, figs. 1 

 and 2). From the ray cells some hyphse make their way into adja- 

 cent wood cells (fig. 2, 2\ PL I, figs. 1 and 2).'' They grow along 

 these, both up and down (fig. 2, i) , giving off branches to other wood 

 cells. In this manner the whole wood body becomes penetrated by 

 the brown hjphas in a verj- short time after the first infection. The 

 number of hyphse in the wood cells proper, excluding the medullary 

 ray cells and the cells of the wood parenchyma, is very small indeed. 

 This is probably due to the fact that the fungus finds scant material 

 upon which to live in the wood cells. The hyph» arc apparently 

 able to puncture the unlignified walls here and there, but they stop 

 at that point. The writer was not able to demonstrate that the hyphse 

 could attack the lignified walls. In other words, the ' blue ' fungus 

 is one which confines its attack to the food sub; ttinccs contained in the 

 storing cells of the trunk and to the slightly lignified walls of these 

 storing cells." According to the same authority (4-?, p. 19), the resin 

 ducts may be attacked in like manner (fig. 2, 3\ PL I, fig. 2). 



In the case of sawed timber it is quite probable that the fungous 

 spores falling upon the surface of the sapwood find there the mois- 

 ture and food material necessary for germination. Subsequently they 

 give rise to a mass of mycelium, many of whose hyphse enter the 

 wood through the exposed medullary or pith rays and then probably 

 invade the surrounding tissue, as explained by Von Schrenk. 



SUSCEPTIBILITY OF VARIOUS WOODS TO SAP-STAIN FUNGI. 



The sap woods of many kinds of timber are susceptible ^to sap-stain, 

 though the degree of susceptibility varies considerably. Among the 

 conifers southern yellow pine, western yellow pine, sugar pine, and 

 the spruces seem to be readily stained and in the case of the broad- 

 leaved trees, red gum, red oak, white oak, and hackberry seem to be 

 particularly susceptible. 



Often there is a considerable difference between a species when 

 grown on the dry uplands and the same species when grown under 

 the moist conditions characteristic of the lowlands (Von Schrenk and 

 Spaulding, ^4)- This difference in woods of the same species may be 

 even more marked when grown in essentially different climates 

 (Spaulding, 4^) . It seems to be the opinion of many lumbermen that 

 timber grown in the South is more susceptible to fungous attacks 

 than timber grown in the North. If differences in susceptibility do 



" E. E. Hubert {21) observed in the wood of scrub pine and northern white cedar 

 hypb£B of CcratostomeUa sp., which had penetrated tracheids and wood fibers for a dis- 

 tance of several cells from the medullary rays. 



