52 Tin: whi'j'k pine. 



recently attacked, consist in a change of tlie leaves to a i)ale sicUy color and often tlie ]irodiictioii 

 of short stunted shoots. A still more marked .symptom is tlie formation of urcat <|nantitics of 

 resin, which flow downward through the injured part.s and oat into the ground, resulting in the 

 sticking together of the root.s and masses of dirt that have been ])enetrated by the resin. Passing 

 up a little way into the trunk, the cau.se of this is seen in the active working of tlie fungus in the 

 medullary rays and around the resin canals, where apparently both cell walls and cell contents 

 undergo degeneration and partial conversion into resin. Tliis flows downward, as already stated, 

 and also works laterally into the cambium, producing great blisters in the younger jiart.s wliere 

 growth is going on. and also resulting in the formation of abnormally large resin canals. 



As the di.sease advances the fungus continues to attack the tracheids of the sound wood and 

 .soon induces marked (dianges. Under its influence the walls lose their lignitied character, become 

 softer, and give the cellulose reaction, while the mycelium (jf the fungu.s penetrates and fills the 

 enlarged cavities of the tracheids. (IM. XII, J, 5, (J.) 



The whole inside of the trunk may finally become hollow for .some distance above the stump, 

 its interior being filled with a loose rotting mass, i)enetrated by rhi/.omorpli strings, and only 

 becoming woi'se the longer it stands. Tlie disease having once reached this stage, there is of course 

 nothing to be done for the tree but to fell it as soon as possible and save whatever wood remains 

 unaffected. 



{'2) PnJyiwruH (t)nwsi(.t Fries ( Trnmetes fatliciperda R. Hartig). — This is one of the most dangerous 

 parasites of coniferous trees, causing "red rot" and the dying out of plantations both of young 

 and old pines. In (iermauy it infests various species of pines, including I'inioi strol/un and I'iitii.s 

 sylrestris; also I'icca cxcelsa, Jiiniperus commuuis, ami others. It is more destructive to the White 

 Pine than to the Scotch Pine. 



The disease apjiears in plantations of various ages, from five to one hundred years old, show- 

 ing it.self by single plants here and there becoming pale, tlieu yellow, and suddenly dying. These 

 external symptoms are altogether similar to those observed in trees infected by Agaricus inelleus. 

 Other trees are attacketl in the neighborhood of the infected ones, ami so the disease spreads 

 centrifugally. 



The fruiting portion of the fungus (PI. XIII, 1 to 6) grows on the roots near the surface 

 of the grounil, forming yellowi.sh-white cushions (white on the spore-bearing surface) tlnit may 

 finally, though rarely, become a foot or more in diameter. lietween the wood and bark of the 

 affected tree are extremely thin layers of mycelium, distinguished from those of Ayaricns mcUcKS 

 by their softness and delicacy. The tissue of the roots and the inside of the stem is decayed to a 

 considerable height. 



The disease is .spread by the spores, which are carried away by mice and other burrowing 

 animals and deposited on the roots of adjacent trees, where they germinate and penetrate the 

 living tissues of the bark, i)assing thence into the wood elements and growing in them toward the 

 stem. It is also communicated by the I'oots of infected trees crossing those of sound ones in the 

 ground (PI. XIII, ;), the fungus growing directly from one to the other. 



A violet discoloration of the wood is the external symptom of beginning decomposition, in 

 wliich the contents of the i)arenchyma cells die and turn brown through the action of the mycelium. 

 This color disappears with the loss of the cell contents, and a dear brownish-yellow takes its jilace, 

 with scattering black spots here and tliere. These are surrounded at a later period with a white 

 zone (PI. XFI, S), and at the same time the wood becomes continually lighter and more spongy. 

 At last numerous openings ari.se, the wood is separated into its constituent libers, and becomes 

 watery and of a clear brownish-yellow color. The cell wall undergoes decomi)osition, giving the 

 cellulose reaction instead of remaining lignitieil, and finally even the entire middle lamella disap- 

 pears. Th(! jirocess may go on until the wood elements are isolated, so that they are easily jiicked 

 apart like threads of asbestos. 



The parasite advances rapidly in the wood elements, de<omposition .soinetinies going on in this 

 way to the height of 2.> feet. In the bark it ]iroceeds more slowly, but is finally none the less 

 dangerous, since it causes the death of the corti(!al ])art of the root in wiiich it originates, and 

 when after reaching the trunk it passes into the other roots, their death finally resulting in the 

 death of the whole tree. 



