FUNGI OF IMPORTANCE IN THE DECAY OF TIMBERS. 39 



timber, such as inferior southern pine, spruce, and hemlock, which 

 have been used in mill construction in recent years, are readily at- 

 tacked and destroyed. Hence, the losses through decay by a certain 

 group of fungi are large. Because of the practical importance under 

 mill conditions of Lenzites sepiaria, L. trabea, Trametes serialis, 

 Fomes roseus, and Lentinus lepideus, studies upon the physiological 

 relations of the basidiospores, mycelium, and secondary spores were 

 undertaken, particular attention being paid to those factors influenc- 

 ing intramural dissemination. 



All five of these fungi have been found fruiting more or less com- 

 monly upon mill roofs or in basements. Lenzites sepiaria and L. 

 trabea do more damage to coniferous roof timbers than has here- 

 tofore been reported. 



The basidiospores of the five fungi will germinate upon various 

 agars, or wood, in tap water, and irregularly in distilled water. 



At 40° C. the basidiospores of Lenzites sepiaria will germinate in 

 large percentages, while those of L. trabea and Fomes roseus give 

 small percentages. The spores of the other two fungi will not germi- 

 nate at this temperature. The optimum temperatures for rapidity 

 of germination are: Lenzites sepiaria, 32° to 35° C. (89° to 97° F.) ; 

 L. trabea, 28° to 32 ° C. (82° to 89° F.) ; Trametes serialis, 30° to 32° 

 C. (86° to 89° F.) : Fomes roseus, 28° to 32° C; Lentinus lepideus, 

 28° C. Large percentages of the spores will germinate at the lower 

 temperatures within the range of growth for each fungus if sufficient 

 time is allowed. The percentage of germination is the criterion 

 which best shows the effect of temperature upon the viability of the 

 spores. 



Diffused light did not affect the germination of the spores. The 

 basidiospores of these fungi would not germinate in direct sunlight 

 in May. and after two days of exposure few or no spores would germi- 

 nate when put in the dark. Two days of direct sunlight in May 

 acting upon dry spores usually killed all but a very small percentage, 

 if not all of them. The germ tubes showed no phototropic responses. 



In drying tests, basidiospores of Trametes serialis and T^entinus 

 hphlctiH (aged 10 days and 7 months, respectively) were killed in 

 about 10 weeks' exposure at 28° and 32° C. (82° and 89° F.) and in 

 about a month at 36° C. (97° F.). With fresh spores at 40° C. 

 (104° F.), T^enzites sepiaria survived two months and Trametes 

 serial In six weeks in an unfinished test. Spores of Fomes roseus five 

 months old were killed in one week at the same temperature. 



Alternate wetting and drying is destructive to the spores of these 

 fungi. This applies either to the wetting with free water Or exposure 

 to atmospheric moisture and subsequent drying. 



Basidiospores of Lmzites sefdaria gave a germination «>f 25 per 

 cent after 2 years and 10 months of storage in an ice box; (hose of 



