26 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. 



entrance into the heartwood. After infection has taken place in 

 this manner, the mycelium grows in the heartwood. Before sporo- 

 phores are formed it is often impossible to locate the presence of 

 the mycelium in the tree. This is particularly true for quite young 

 fungus plants, and the possibility that the beginnings of decay 

 may be hidden in a log, both ends of which are perfectly sound, 

 must ever be present in the mind of the operator. It is impos- 

 sible, except by mere chance, to detect the very first stages in the 

 field. As soon as the fungus plant, the mycelium, has reached a 

 certain stage of development, represented by visible alterations of 

 the wood, there is no excuse for overlooking it. As a rule, the oldest 

 part of the focus of infection shows the strongest evidence of 

 fungus growth expressed in what we call decay. Decayed stubs 

 are a valuable index as to decay in the tree, although there are cases 

 where, for unknown reasons, the infection does not, or only very 

 slowly, result in more extended decay. Duesberg 1 has advocated the 

 location of infected trees by the presence of diseased branch stubs. 

 Such decayed branch stubs may also correspond to that stage of 

 development of the mycelium just before the formation of sporo- 

 phores through the stub takes place. In this case also decayed 

 branch stubs will be most valuable in detecting heart rot in the bole. 



If decay is found, it is followed throughout its entire extent by 

 splitting the logs with wedges and with the ax. To avoid this often 

 very tedious and time-consuming work, splitting with black powder 

 has been tried, with rather unsatisfactory results. In partly decayed 

 logs the splitting is very irregular, and the wood surfaces are badly 

 stained and blackened, the stain generally interfering with the inspec- 

 tion of the wood. When the full extent of the decay is determined, 

 notes are taken on the character of the discoloration or decay and on 

 the stage of development, and the extent is carefully measured. For 

 studies of this kind it will often be sufficient to note the extent in 

 length in linear feet, under the assumption that in low-priced species 

 any lumber that might be cut from an affected part of the bole will 

 not pay for its transportation to the mill. In higher grade species 

 the lateral extent must always be considered. 



This complete and detailed dissection usually allows the tracing of 

 the decay to some point of entrance, whether fire scar, lightning 

 wounds, frost cracks, or branch stubs. The result is entered on the 

 sheet. Finally, any notes not specially foreseen on the sheet are 

 entered under "Remarks." 



As a general principle, all observations that can be expressed 

 numerically must be given in figures. It is essential that all esti- 



1 Duesberg. Das Aufsuchen von Schwammbaumen in Kiefernbestanden vor der Ausbildung von 

 Fruchttragern. In Ztschr. Forst- u. Jagdw., Jahrg. 44, Heft 1, pp. 42-43, 1912. Reviewed in Forestry 

 Quart., v. 11, p. 251, 1913. 



