52 THE WHITE PINE. 



recently attacked, consist in a change of the leaves to a pale sickly color and often the production 

 of short stunted shoots. A still more marked symptom is the formation of great quantities of 

 resin, which Mow downward through the injured parts and out into the ground, resulting in the 



king together of the roots and masses of dirt that have been penetrated by the resin. Passing 

 up a little way into the trunk, the cause of this is seen in the active working of the 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. This flows downward, as already stated, 

 and also works laterally into the cambium, producing great blisters in the younger parts where 

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



As the disease advances the fungus continues to attack the tracheids of the sound wood and 

 soon induces marked changes. Under its influence the walls lose their lignifled character, become 

 softer, and give the cellulose reaction, while the mycelium of the fungus penetrates and fills the 

 enlarged cavities of the tracheids. (PI. XII, J, 5, 6.) 



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, penetrated by rhizomorph strings, and only 

 becoming worse the longer it stands. The 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) Polyporus annosus Fries ( Trametes radidperda 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 Germany it infests various species of pines, including Pinus strobus and Pinus 

 sylrestris ; also Picea excelsa, Juniperus communis, and others. It is more destructive to the White 

 Pine than to the Scotch Pine. 



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

 ing itself by single plants here and there becoming pale, then yellow, and suddenly dying. These 

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

 Other trees are attacked in the neighborhood of the infected ones, and 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 ground, forming yellowish-white cushions (white on the spore-bearing surface) that may 

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

 attected tree are extremely thin layers of mycelium, distinguished from those of Agaricus melleus 

 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 hy 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, passing thence into the wood elements and growing in them toward the 

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

 ground (PI. XIII, 7), the fungus growing directly from one to the other. 



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

 which the contents of the parenchyma cells die and turn brown through the action of the mycelium. 

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

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

 zone (PI. XII, 8), and at the same time the wood becomes continually lighter and more spongy. 

 At last numerous openings arise, the wood is separated into its constituent fibers, and becomes 

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

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

 pears. The process may go on until the wood elements are isolated, so that they are easily picked 

 apart like threads of asbestos. 



The parasite advances rapidly in the wood elements, decomposition sometimes going on in this 

 way to the height of 25 fett. In tlie bark it proceeds more slowly, but is finally none the less 

 dangerous, since it causes the death of the cortical part of the root in which 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. 



