THE RED ROT OF CONIFERS * 13 



in the tubes showed that the susceptibility of the wood seemed to range 

 in order as follows : Tamarack, pine, hemlock, spruce, balsam. This 

 order of susceptibility is the same practically as that noted by Von 

 Schrenk (2) in New England forests. 



The inoculations made on oak and birch were successful, the fun- 

 gus growing luxuriously ; but the damage to the wood was done more 

 slowly and its extent relatively was very limited. The attack of the 

 fungus on the hard woods should be studied more thoroughly. The 

 preliminary sterilization, of course, may have rendered them soft and 

 also may have brought about chemical changes which rendered them 

 more readily open to attack than when in their natural state. 



The brown incrustation occurred fully four weeks later in the 

 case of all eight cultures of the tamarack and balsam than in the 

 cultures on pine, spruce, and hemlock inoculated at the same time. 

 Microscopical examination revealed no essential difference in the fun- 

 gus as cultivated on the different woods, except that the hyphae cells 

 possibly were a little larger in diameter on the tamarack and smaller 

 on the hard woods. 



Influence of moisture. The growth of the fungus is profoundly 

 affected by the presence or absence of water in the tubes. Without 

 exception whenever moisture was lacking to any great extent, the 

 growth of the fungus was affected directly. If water was omitted at 

 the time of inoculation, the culture failed to develop. If the fungus 

 grew luxuriantly in the presence of moisture it ceased its growth im- 

 mediately and dried up if the water supply was withdrawn. Tubes in 

 which this drying out process had taken place once, but slowly re- 

 established growth upon the addition of water. 



Spores. The cultures were examined microscopically at various 

 stages for spores. The last of these examinations was made in May, 

 1913, and, even on cultures which had been growing since September, 

 1912, no trace of such reproduction could be found. The marked uni- 

 formity of the general characters of the mycelium, noticed in all 

 the slides prepared from the different cultures, indicated that the same 

 fungus had been isolated in all cases. The growth of the fungus on 

 the sterilized wood cultures produced the same appearance as that 

 taken from a diseased tree in the forest. Blocks of wood are shown in 

 Plate IV on which the fungus had flourished for a period of six 

 months but from which the mycelium was scraped from the wood to 

 show more clearly the presence of the white-lined pockets which are 

 so characteristic of the disease. 



