112 TRANSACTIONS OF THE [JAN. 4, 



place. The mycelium fruiting only under very favortible condi- 

 tions, the fruit is not easily found. A specimen is here shown. 

 I have seen many thousands of tics destroyed by it without 

 finding the fruit. Its mycelium is very abundant, and pierces 

 the coarser cells of the wood with great rai)idity, generating 

 suflScient moisture, having an acid reaction, to carry on its 

 destructive work, provided external currents of air and heat 

 are not sufficient to dry the wood. Examining numy pieces 

 of bridge timbers which were horizontal, I found where they 

 had rested on others sufficient moisture had collected to 

 germinate the spores, and the mycelia had followed the lon- 

 gitudinal cells from each way, until they had met in the centre 

 between the supports. The outer portions of the timber remain- 

 ing dry did not allow the moisture to escape, and the fungus was 

 destroying the inside, while the outside looked sound. I have 

 here a part of a bridge plank. The moisture accumulated where 

 it rested on the joists, the mycelia working each way and upwards, 

 leaving a thin portion of one-eighth to one-quarter of an inch in 

 thickness, giving the appearance that it was all sound. The 

 abundant fructification during a brief, warm rain in September, 

 1883, was the first indication of tlie destruction which had taken 

 place. In ten minutes walk from this hall, we could see many 

 thousands of feet of timber destroyed by this fungus, Avhile the 

 cause of decay is hardly suspected. 



The upright cells or tracheids composing the annual ring of 

 the Finns pain str is Mill, are of two kinds; one of thin, and the 

 other of thick walls. The former fill the inner part of the ring, 

 the latter the outer portion, giving the great strength and hard- 

 ness to the wood. Interspersed through the ring are a few 

 resin ducts. In decay induced by its special fungus, the myce- 

 lium often separates some of the annular layers, and in most cases 

 the thin-walled cells are softened first. On railroad sleepers, 

 larvjB from one-sixteenth to one-eighth of an inch in length, eat 

 and bore through the softened fibres, so that in ties of four to 

 seven years' service we often find little more than a series of 

 nearly separated shells. The mycelium of this fungus, once in 

 the road-bed, is, in summer time, ready to attack new ties of this 

 timber as soon as put in the ground. I have noticed tics, taken 

 up after a short service of six to eight months, which were cov- 

 ered on the bottom by the brandling mycelium, and after dry- 

 ing one-eighth to one-fourth of an inch in depth, would crumble 

 to dust. This is the so-called dry rot. It takes much longer 

 for the mycelium to destroy the yellow-pine sleepers from the 

 bottom and sides than when it has access to the ends. In the 

 first case, it must nearly destroy the small medullary cells to 

 reach the various rings, while from the end it has a larger area of 



