18 



HARDWOOD RECORD 



March 25. 1922 



appear as serious defects and may cause him to reject such stock. 

 A "yellow streak" in everyday language is usually interpreted as 

 u sign of weakness, and the discovery of a "yellow streak" in oak 

 wood should be seriously investigated. Yellow stained oak should 

 not be used in the construction of airplane propeller blades, although 

 there seems to be no reason why it should not be used for purposes 

 requiring wood of less exacting strength projicrties. 

 The Bed Stain in Boxelder 



As far back as 1880 there is a record in German literature of a 

 "blood red" to "carmine red" stain observed in the heartwood of 

 the trunk, roots and branches of boxelder (Acer negundo). At 

 that time a statement was made that some fungus might be respon- 

 sible for this stain. Recently many samples of red stained boxelder 

 have been referred to this laboratory for examination to determine 

 the cause of the discoloration. Sections of the stained wood exam- 

 ined under the microscope disclosed numerous hyphae of some fungus 

 developing in the wood cells. This red stain has been observed to 

 extend from the roots through the trunk and into the larger branches 

 of several freshly cut boxelders. Information from other parts of 

 the United States where boxelder is cut in considerable quantity 

 indicates that this stain is very common and that it is a peculiar 

 characteristic of the wood of this tree. In fact, it may be used 

 with some degree of accuracy as one of the characters in the iden- 

 tification of this wood. 



The color of the stain usually varies from a light jasper red to 

 a light coral red or coral pink. In the heartwood of the branches the 

 color is often very pronounced. In the heartwood of the main trunk 

 of the tree there often 

 develops a true heart- 

 rot of a dull yellowish 

 brown color and on 



the outer edge of this j^ yr,g 



rotted area is found a jS' I"" 



zone of bright red, 

 usually extending to 

 the inner edge of the 

 sapwood. Cultures 

 made from these two 

 areas indicate there 

 are apparently in this 

 case two distinct and 

 separate fungi devel- 

 oping in the heart- 

 wood. 



The "Scorch" of 



White Pine and 



Yellow Pine 







B 



I 1 



Fig. 2. Showing the flask-shaped fruiting body 

 of a blue-stain fungus at A. Enlarged about 

 100 times. The actual length is about 5 100 of 

 an inch. At B are shown the minute spores 

 produced from this fruiting body, and capable 

 of germinating and starting new infections. 

 Enlarged about 800 times. 



A new and very 

 striking stain has 

 been observed recent- 

 ly developing on air- 

 seasoned white pine (P. strobus) while stacked in the mill yards. 

 It has also been collected on western yellow pine. It is aptly 

 termed a "scorch" stain, for the discoloration resembles very 

 closely a scorching by fire. Attention to this stain was first directed 

 by samples of "scorched" white pine sent in for determination 

 of the cause of the discoloration. It has been found to discolor the 

 best grades of white pine and yellow pine lumber and considerable 

 loss in degrade has resulted. This discoloration should not be con- 

 fused with the chemically produced brown stain of sugar pine, which 

 it closely resembles. 



The scorched areas are somewhat irregularly distributed through- 

 out the wood, both heartwood and sapwood being subject to attack. 

 The colors of the patches and streaks range from a light yellowish 

 brown to a rich dark brown, sometimes approaching black. The 

 streaks are sometimes narrow, extending some distance along the 

 grain of the wood. In western yellow pine the "scorch" develops 

 in the sapwood adjacent to blue stain and apparently the two do 

 not mingle. 



Cultures made by using fragments of the stained wood invariably 

 produce a fungus, the mycelium of which becomes dark brown with 

 age. The fungus isolated is apparently the direct cause of this dis- 

 coloration, and is one of the numerous fungi belonging to the large 

 group, the molds. It is ijrobably a species of AUcrnaria, and micro- 

 scopical examination of the stained wood shows hyphae resembling 

 this fungus developing within the wood cells and occasionally pene- 

 trating the cell walls. 



Blue Stain of Hardwoods and Softwoods 

 The common defect produced in "sap" lumber and other wood 

 products by the species of Ceratostomella is called "blue stain." 

 Boards so stained are graded lower than unstained boards, and since 

 much of this staining develops in storage or during air seasoning 

 considerable loss is experienced when infected piles are opened up 

 and it is found that much of the stock has to be regraded before 

 it can be sold. 



Blue stain is com- 

 mon in the sapwood of 

 a large number of 

 woods, both of the 

 hardwood and the soft- 

 wood species. The fun- 

 gus causing the stain 

 grows rapidly and sap 

 stain may appear in a 

 log 48 hours after it 

 is cut. The minute 

 threads or hyphae of 

 the fungus are of a 

 colorless to brown 

 color, and their pres- 

 ence in the wood tis- 

 sues is responsible for 

 the blue-gray discoloration. When these threads, feeding on the 

 contents of the wood cells and to some extent on the cell walls, 

 reach a certain stage in their development, fruiting bodies are 

 produced upon the surface of the wood. These fruiting bodies 

 appear as minute black specks upon the blued wood, and under 

 a magnifying glass are seen to resemble small black hairs or 

 bristles swollen at the base (Fig. 2A). These black, flask-like 

 bodies contain the spores (Fig. 2B) which when ejected are carried 

 about by the wind and other agencies and are capable of germinat- 

 ing and causing a new blue-stain infection. 



In a study of several species of both broadleaf and coniferous 

 woods it was observed that quite frequently the fungous threads 

 penetrated the wood cells (Figs. 3c and 4). In one case in which 

 the sap wood of scrub pine was found heavily blued, the examina- 

 tion of radial sections showed a single young hypha or thread pene- 

 trating three cell walls (Fig. 4). The fungous threads are con- 

 siderably constricted where they pass through the bore holes in the 

 cell walls, and swellings occur in the threads at the points where 

 they enter and emerge (Figs. 3 and 4). 



More often the hyphae in spreading throughout the wood tissue 

 search out the natural openings in the wood cells and pass through 

 these, the shape of the fungous thread conforming to the shape of 

 the opening (Pig. 3C). In the case of simple pits, the hyphae must 

 dissolve the middle membrane in order to pass through. 



In the less resistant wood ray cells the effect of the fungous attack 

 is very pronounced. The cell walls between the ray cells are com- 

 pletely dissolved, so that there is less than a shell or framework of 

 the ray left (Fig. 3A). These wood ray cells are particularly 

 affected by the fungous attack and appear to be weakened, and 

 this no doubt affects the strength of the wood to some extent. For 

 ordinary uses blued wood is apparently as strong as unstained wood. 

 Little work has been done to prove that the stained wood is below 

 normal in strength. 



Such reliable strength tests as have been made indicate a slight 

 weakening effect, due to the blue-stain. Since decay-producing 

 fungi may develop simultaneously with blue-stain in the same tim- 

 ber, this furnishes a basis for discriminating against the use of blued 



i 



