54 THi: WHITK PINE. 



matter, as nmcli siinlif^lit as the plants will endure witliout wiltiii;:, a fairly low teini>crature, and 

 an abnndaiit siipjdy of fresh air. Jlr. .1. Dawson, of the Ai-nokl Ari)oretuni, suggests waterinjjr 

 the youii-j jjlants from below, so as to avoid wiltinj^- the leaves, as a means of i)reventif)n. Other 

 suggestions will be found in recent literature of the snbjeet, prai;tically in the rejiorts of varions 

 agricultural experiment stations.' 



A disease whieli attacks the trunk of the tree, at various ages, is very i)revalent in i)ine 

 forests, and occasions the condition known among lumbermen as "punky pjiie." A di.seased tiee 

 can freijuently be recognized by its having one or more knots with a rough, irregular contour, at 

 a considerable height above the ground, commonly conspicuous l)y a considcriible outliow of resin. 

 These seem to result from the breaking utf of brancdies, followed by gradual decay at the place 

 where they have separated from the tree, in such a way as to admit water into tbe trunk, the 

 oi)ening being afterwards partially covered Ity subsequent growth of the tree while decay is going 

 (}n inside. 



Upon examining the wood of such a tree, it is seen to be discolored and in various stages of 

 decay, the diseased condition extending inward from the knot hole, and both uiiward and 

 downward from it in the trunk. By inspecting logs cut from such trees, it will be noticed that 

 the decayed portion may have lilled up the center, making a rotten heart; or it may follow the 

 rings of growth for some distance, midway from the center to tbe periphery; or it maybe still 

 nearer to the surface, its i)0siti()n and extent being very variable and following no recognizable 

 rule. The parts diseased are utterly worthless, though boards containing a greater or less amount 

 of wood thus affected are common in the market. Microscopic examination shows that the wood 

 is penetrated by the filaments of a fungus, and that the elements of which the wood is made up 

 have been greatly altered, and to a considerable extent deconii)oscd bj- its action. 



Continued observation in the pine woods of Michigan, iu different years, does not so far justify 

 the reference of this disease to any single si)ecies of the various fungi found growing upon the 

 truidvs and logs of decaying pine trees. Hut whatever the s))ecies, one or several, concerned in 

 producing or hastening the condition described, the general facts, as stated above, appear to be 

 that the disease finds its way where the separation and decay of a branch ])reseuts a favorable 

 idace for the entrance of water and the sjxjres of fungi, and that it spreads so extensively in the 

 trunk as to entirely ruin large and valuable trees. 



In our natural forests there is, of course, neither remedy nor ijrevention, but in artificial culti- 

 vation careful and seasonable pruning would doubtless be the moNt effectual i)reventive, since, if 

 properly performed, the wounds left by the removal of branches would soon be grown over and 

 there would be no further danger from this source. 



KXI'LAXATIo.N ol' I'l.ATl-: XII. 



/. AgaririiK milieus, cluster of young .spompliorcs. 



2. Agarii-iia mdienx, larger spoiopliore with root-like organ of attachiiieut. 



3. J{oot of spruiT tree iiivadcil by inycelium of Aijariciia melhns; rliizoiuorph of s;inio fungus on the riglit. 

 i->). Fraguients of pine wood showing the destructive aetion of .Ir/ariruH mellciin. 



7. Stuuip of White' I'ino attaeked by I'oliipi>niH aiiiioiiin ; the heart is still sound, but is siirniuniled by decayed 



wood and spots filled with masses of resin. 

 S. Wood of Norway Spruio in early stages of decay occasioned by action of I'ohiporiia annoxua: the white areas 



have become delignihcd, an<l the wood elements com)io8iug them are soft and easily sciiarable. 

 9. Wood elements of Norway .Spruce isolated and showing the mycelium of the Pohjporus aiinoaus. 

 10. Fruiting hyph.i- and spores of Poh/ponis unnosita. 



KXI'I.ANATION oI- IM.AIK XIII. 



/. .Slum]) of Norway .Spruce, with a siioroiihioc of I'oliijioriia (iinioana several ye.irs ohl; tlie inner jiortions of the 



stump whcdiy decayed. 

 ,.'. Roots of a diseased spruce tree, with iiiimrrous small sporophores of I'lilijiionia uiinoitiia .ittached. 

 J. Stuuip and jiait of root system of a young )iiui- tree killed by the action of I'olijporiia annoxua, the sporophor.-s of 



whioh have grown entirely around the base of the trunk. 

 ■I. Mature sporophore of I'lili/ponix annoxua seen from below, showing the porous Sjioie-bearing surface. 

 .5. Mature sporophore of I'olijpnnix annoaua from above, showiu',;- the velvety upper surface and concentric^ bands. 



6. Mature sporophore (){ J'olifpurnx annoana in secticm. 



7. Mode of infection; where the smaller diseased root crosses the larger one, the mycelium of the I'ult/jiorua annoaua 



has penetrated the latter and spread in both directions for some distance. 



'Cf. Atkinson, Cornell Univ., Agr. Exp. .Sta. Bull. lU, 189.">, 



