TIMBER STORAGE IN THE EASTERN AND SOUTHERN STATES. 5 



thus passed during rainy weather from the bottom upward through 

 piles 12 to 15 feet high. In lumber storage sheds or in the base 

 of close piles the mycelium of several species of fungi has frequently 

 been observed developing in great abundance, not alone on the moist 

 foundations and lower layers of lumber (PL TI, fig. 1), but also 

 spreading profusely on the soil (PL II, figs. 2 and 3). 



With some species of wood-destroying fungi the mycelium within 

 infected timber may remain alive for long periods, even under air- 

 dry conditions, a fact which makes the use of infected timber in 

 building operations a dangerous procedure. As an example, we have 

 the experimental evidence advanced by Bayliss ^ that the mycelium 

 of Polystictus versicolor in wood can survive a period of four years 

 under the dry conditions of a herbarium. 



Infections hy spores. — The chief purpose of spore formation in 

 fungi, just as in seed formation in ordinary green plants, is the 

 perpetuation of the species through reproduction. Spores serve 

 the two- fold purpose of tiding the fungus over unfavorable periods 

 and of allowing its rapid spread under favorable growth conditions. 

 Nature is lavish in her methods, and the number of spores produced 

 is often enormous. For instance, Buller^ computed from partial 

 counts that each pore on the under side of Polyporus squamosus 

 produced in the course of a few hours an average of 1,700,000 spores, 

 or a total of Over eleven billion for the entire under surface of a 

 fruit body having an area of 250 square centimeters (38.75 sq. in.). 

 When one recalls that spores are either constantly or intermittently 

 produced by a single fruit body over a long period the further state- 

 ment made by Buller that "the number of spores produced by a 

 single fungus * * * in the course of a year may, therefore, 

 be some fifty times the population of the globe " becomes intelligible. 



At least two general types of spores are recognized for most wood- 

 destroying fungi, the most easily observed being the basidiospores 

 produced by the fruit bodies. These may frequently be seen en 

 masse as a white or colored powdery deposit which has fallen from 

 the sporophores (PL II, fig. 4). These spores are produced on 

 short stalks at the ends of club-shaped cells which form a palisade 

 layer (PL II, fig. 6) covering the under surface of the fruit body, 

 or, in case the fruit body is of the incrusting type, covering its outer 

 surface. When mature, the spores are cast off the basidia into the 

 air and are blown about by the wind. When they lodge in a moist 

 place favorable for growth they readily germinate and produce a 

 new infection. 



1 Bayliss, Jessie S. The biology of Polystictus versicolor (Fries). In Jour. Econ. 

 Biol., V. 3, no. 1, p. 1-24, 2 pi. 1908. 



- Buller, A. H. R. The biology of Polyporus squamosus Huds., a timber-destroying 

 fungus. In Jour. Econ. Biol., v. 1, no. 3, p. 101-138, illus., pi. 5-19. 1906. 



