26 TIMBEE EOT CAUSED BY LENZITES SEPIAEIA. 



althouo;h it is likely that the food substances in the cell cavities are 

 dissolved and ])artly removed by the solvent action of the water. 

 Undoubtedly the air supply has much to do with the rotting of posts 

 and similar timbers at or near the surface of the soil, wliile both 

 above and below the surface decay is not so complete (fig. 3). 



Water swpplij. — That a certain degree of moisture is essential for the 

 growth of the wood-rotting fungi is as true of the so-called dry rot 

 fungi as of any other. As soon as a certain piece of timber becomes 

 well seasoned it loses much of its susceptibility to attack by fungi, 

 and as long as it remains relatively free of water it will not rot. 

 Instances are plentiful in Europe where timbers which are now sound 

 have been in place in buildings for hundreds of years. Wood from 

 the royal tombs of Egypt is perfectly sound after a period of over 

 5,000 years. This fact can be explained in no other way than that it 

 w^as well seasoned when put in place and has been protected from 

 moisture ever since. 



Temperature. — A fourth condition is requisite for the growth of wood- 

 rotting fungi, namely, a favorable temperature. These fungi can grow 

 at ordinary temperatures in most countries, but they make little or no 

 growth at freezing point and below. Many of them appear to have an 

 upper limit even in outdoor temperatures at wliich they do not thrive. 

 In the usual spring, summer, and autumn weather of this country the 

 wood-rotting fungi thrive, but in winter growth ceases except in the 

 tvvarmer sections, wdiere it probably continues all the time.'' 



METHODS OF PREVENTING THE DECAY CAUSED BY LENZITES 



SEPIARIA. 



fX The decay of timber caused by Lenzites sejnaria is brought about 

 %■ the action of the vigorously gromng mycelium in breaking down 

 the w^ood tissues and utilizing certain of their constituents in its 

 own life processes. Consequently, anything wdiich influences the 

 growth and vigor of the fungus has a direct mfluence on the rate 

 and extent of decay which the fungus can cause. It has been already 

 stated that four essential factors govern the growth of Lenzites 

 sepiaria, and therefore control the decay caused by it. Of these 

 four factors only temperature may not be more or less regulated 

 in timber which is in service, or while such timber is being prepared 

 for service. 



oFalck (Die Lenzitesfaule des Conifereiiholzos) gives some specific data on the 

 maximum temperature for Lenzites sepiciria. He found that the mycelium in (hy 

 wood resisted an exposure of two hours to a heat of 97° C, nearly the boiling point of 

 water; but mycelium in agar cultures was killed by 10 hours' exposure to 63°, and by 

 2 hours at 75°. The optimum temperature for germination of the spores is between 

 30° and 34° C, while the optimum for the mycelium in cultures is 35° C, and the 

 growth minimum and maximum are 6° and 44° C, respectively. 

 214 



