194 



/ 



conclude that no hard and fast line can be drawn between 

 these classes of saprophytes and parasites, and there is every 

 reason to believe that the one mode of life has led to the other. 

 At the same time it must be remembered that a hypha, which 

 is able to pierce the cell- walls of a plant's tissues, is not by 

 any means necessarily able to kill the living protoplasm in 

 the cells. 



ni 17 ' In India thiS destmctive 



Species" fungus has been found on Pinus excelsa near Simla, and 

 attacked. it is well known on various conifers in Europe. 



Signs of the The characteristic sporophores usually first indicate the 

 Disease. presence of the fungus. These appear on the stem usually near 

 the stump of a dead branch, and are hard, bracket-like, masses 

 often triangular in section. The upper surface of the sporo- 

 phore is rough, blackish-brown in colour and with concentric 

 grooves, the fawn-coloured lower surface is covered with the 

 minute pores in which the spores are developed. See Plate 

 XVIII (a). 



L '!TT i Rtory I D nianv respects the damage done by this pest resembles 



and Damage v J v 



done. that described above m the case ot tomes annosus, 



but it is important to note that, whereas the latter 

 fungus can attack sound roots, Trametes Pini can only 

 attack a tree through an existing wound, and it is consequently 

 termed a " wound parasite". The spores, alighting on a 

 wound which is not covered with resin or other protective 

 substance, on germination produce hyphse which penetrate 

 into the stem. The hyphar bore through the cell-walls and 

 extract the lignin in them so that practically pure cellulose 

 is left behind. Characteristic white spots, which eventually 

 become holes, then appear in the attacked wood, see Plate 

 XVIII (6). The growth of the mycelium may also cause cup- 

 shake, or ring-shake. The timber is thus rendered useless, and 

 if the tree attacked cannot oppose the invading mycelium by 

 a copious flow of resin the hyphse may spread to the cortex 

 and kill the tree. Wounds caused by breaking or cutting off 

 old branches which contain heart-wood are favourite points 

 of attack, for little or no turpentine exudes from the central 

 portion of such wounds, into which in consequence the hypha3 

 readily penetrate. For the same reason such wounds also 

 afford a convenient passage free of resin by means of which 

 the mycelium can pass from the interior of the stem to the 

 outside for the purpose of producing sporophores, the latter 

 frequently appearing at such places. Sporophores are not 

 as a rule produced until a luxuriant growth of mycelium has 



