13 



on their roots, trunks, or branches. The lumberman of the present 

 day naturally tries to avoid trees which are rotted, and his method of 

 diagnosis consists in pounding the trunk to see whether it sounds hol- 

 low. Hollowness, however, is not always a sign of disease, as many 

 trees are hollow at the base and sound above, and therefore satisfy the 

 demands of the lumberman at least in part. A test in use all over the 

 country is the presence of what are variously known as punks, conchs, 

 punk knots, resin knots, etc. A punk is usually the sporophore of 

 Trametes jnni, or some other large hoof -shaped sporophore. The other 

 terms are more often applied to swellings which occur at points where 

 a dead In-anch stub is found on the tree. In diseased trees of Pine or 

 Spruce the turpentine is driven from the wood ]>y the action of the 

 mycelium of this or that fungus, and passes on before it, up the heart- 

 wood of old branches and out through them, forming resinous lumps, 

 which harden in contact with the air. These lumps occur at all heights 

 on the trunk and increase in size from year to year. The accumulation 

 of these resinous masses prevents the normal healing of the wound or 

 healing over of the stub of the branch, and results in the formation 

 of a marked protuberance at that point, commonly called a knot, with 

 its various modifications. The turpentine often drips from such a spot 

 or runs down the bark in small streams. It may be many years before 

 the decomposition within the tree advances sufficiently to enable sporo- 

 phores to form, and a system of prophylactic treatment must take into 

 account phenomena such as these to aid in detecting diseases in their 

 early stages. What has been said with reference to these resin accu- 

 mulations applies particularly to fungi like Trametes jnni {^vot.)FY. 

 and its form ahletis Karsten, to Polyporm schweinitzU, and Pohjjyorm 

 sulfurcm^ and one or two others not yet definitely identified. 



RELATION TO INSECT ATTACKS. 



The nature of the fungus injury is often very obscure, and there are 

 so many factors which have to be considered in tracing the nature of 

 any one disease that the results of the present paper are but fragmen- 

 tary, and it is very probable that they will be modified largely by 

 future discoveries. The intimate relationship which exists between 

 the attacks of insects on the one hand and fungi on the other nuist be 

 pointed out. There are without doul)t many fungi which find their 

 way into the wood of trees through the holes which l)oring insects have 

 made in the bai-k. The injury which the insect makes may be very 

 slight, but it has opened the way for the action of the fungus, which 

 may be very destructive. An example of this kind is to be found in that 

 most curious of all the Poh/porel^ Poh/ponis volvatm Peck. This grows 

 on the trunks of spruces which have been attacked by various spe(•ie^^ of 

 boring beetles, notably species of Dcndroctonus. These be(»tles bore 

 throuirh the bark into the cambium laver. The fungus enters through 



