64 Journal of Agricultural Research voi. xii. No. a 



EXAMPLES OF IDENTIFICATION OF UNKNOWN ROTS BY CULTURAI, 



CHARACTERS 



The following examples illustrate how the cultural characters here 

 described may be used to determine the causative organism of unknown 

 rots: 



(a) There are two common heartrots found in conifers in the western 

 United States. One is the redrot caused by Trameies pint and the other 

 is what the senior author has previously called western redrot (9) . In 

 their early stages of growth these two rots resemble each other very 

 much. Pure cultures from each of them differentiate the two immedi- 

 ately, since the pure cultures of the fungus which causes western redrot, 

 called previously Polyporus ellisianus, produces entirely white cultures 

 on all of the 10 media, while the cultures of Trameies pini are varying 

 shades of brown. 



(h) On a recent field trip in eastern Texas, when the senior writer was 

 studying the rots of bridge timbers and railroad ties, he often found a 

 certain rot in driven bridge piling made of creosoted longleaf pine (Pinus 

 palustris). At that time in the year there were no fruiting bodies present 

 on the rotting piling and the question at once arose as to what fungus 

 was the cause of this serious rot. From the peculiar odor of the freshly 

 opened wood as well as the character of the rot it was believed that it 

 was caused by Leniinus lepideus, but nothing could be determined 

 definitely from an examination of the rot alone. Specimens of the 

 rotted piling were forwarded to the laboratory and cultures made from 

 them. Pure cultures were obtained showing all of the characters of 

 L. lepideus when grown on the 10 cultural media. Later many of these 

 cultures developed the typical sporophores of L. lepideus. Cultures of 

 this fungus can usually be recognized by the presence of abortive sporo- 

 phores which develop on the surface of the agar and also by the presence 

 of large, thick-walled, obovate to subglobose spores in the submerged 

 mycelium. 



(c) While studying the rots of cypress (Taxodium disiichum) ties in 

 wet locations in eastern Texas two unknov^Ti rots were found in this 

 wood. Pieces of the rotting ties were sent to the laboratory and pure 

 cultures of two different fungi were obtained. One set of these cultures 

 showed all the cultural characters of Leniinus lepideus, while the other 

 series produced a sporophore of an unknown species of Poria. 



{d) A rot in the heartwood of Quercus gamhelii, collected in New 

 Mexico, was determined in the field as caused by Polyporus dryophilus. 

 Cultures of the diseased wood gave all of the cultural characters of 

 Fames everhartii and none of those of P. dryophilus. 



(e) A specimen of rot in Pinus ponderosa, which was supposed to be 

 caused by Polyporus sulphureus, was received from Oregon. Cultures 

 from the wood showed that the rot was unquestionably caused by 



