52 Tin; WIIITK PINK. 



recently attacked, consist in a cliaii^o' ol' llie leaves to a i)ale sickly color and often I lie prod net ion 

 of short stunted shoots. A still more marked synijjtom is the formation of }in!at <|iiantitii's of 

 resin, whiidi liow (hiwnward throuKh the injured parts and out into tiie grouiul, resullin;^ in the 

 stickin<; togt^ther of the njots and masses of dirt that have bt^en i)enetrated by theresiu. Passinj; 

 u]i a little way into the trunk, the cause of this is seen in the active worl^in},' of the fungus iu 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, ])roducing great blisters in flu! youiigt^r parts where 

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



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

 soon induces marked changes. Under its inllnence the walls lose their lignilied chara(;ter, become, 

 softer, and give the cellulose reaction, while the luycelium of the fungus penetrates and tills the 

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



The whole inside of the trunk may tinally become hollow for sonu; distance above the stump, 

 its interior being tilled with a loose rotting mass, jienetrated by rhi/,om()ii)h strings, and only 

 becoming worse the longer it stands. The disease having once leached t his 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 

 unalfected. 



(li) I'oh/itonis (oi lilts IIS Fries ( Tramefcs radiciperfla It. llartig). — This is one of the most dangei'ous 

 parasites of conifi^-ous trees, causing "red rot" and the <lying out of jdantations both of young 

 aiul old piiM's. In (iermany it infests various species of piin^s, including I'iniis slnihiis and I'iniis 

 si/Iresiris; also I'icea cxvclsa, Jnniperus communis, and others. It is more destructive to tln^ White 

 Pine than to the Scotch Pine. 



The disease apjiears in ]ilantations of various ages, fr tive t(j one hundred years old, show 



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

 external symi)toms are altogether similar to those observed in trees infected by Ai/arivus milieus. 

 Other trees are attacked in the neighborhood of the infected ones, and so the disease spreads 

 centrifugally. 



The fruiting portion of the fungus (PI. Xlll, 7 to 6) grows on the roots near the surface 

 of the grouinl, forming yellowish-white cushions (white on the spore-bearing surface) that may 

 linaily, though rarely, become! a foot or more in diameter. Iletween the wood and bark of the 

 atfected tree are extremely thin layers of mycelium, distinguisbc'd from those of Aiiaricits milieus 

 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 sjiores, wiiich 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 I'oots of infected trees crossing tliose of sound ones in the 

 ground (PI. X 1 1 1. ; ), the fungus growing directly from one to the other. 



A violet discoloration of the wood is the; external symj)tom of beginning decom])osition, in 

 which the contents of the i)arein'hyma cells dU' and turn brown through the action of the mycelium. 

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

 with scattering black si)ots here and there. These are surrounded at a lat(!r jieriod with a white 

 zone (PI. XII, ^), and at the same time the wood becomes continually lighti-r and more si)()ngy. 

 At last numerous oi)enings ari.se, the wood is separated into its constituent fibers, and becomes 

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

 cellulose reaction instead of renntining lignilied, and iinally even the entire middle lamella disaj)- 

 pears. The process may go on until the wood elements are isolated, so that tliey are easily ])icketl 

 apart like threads of asbestos. 



The parasite advances rai)i(lly in the wood elements, decomposition sometimes going on in this 

 way to the height of 2.") feet. In tlie bark it jiroceeds more slowly, but is linaily none the less 

 dangerous, since it causes the death of the corti(!al ])ait of the root in wliicli 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. 



