POLYPORUS. 447 



in greater detail the destruction brought about by its mycelium. 

 He found that it penetrates lignified cell-walls, entering the living 

 elements and causing their death; it spreads most rapidly in the 

 vertical direction through wood, bast, and rind, growing through 

 parenchyma and sieve-tubes, and even boring its way into the 

 sclerenchymatous stone-cells; it absorbs the secondary tliickening 

 by dissolving out first the ligneous inerusbation, next the cellulose, 

 while the middle primary lamella remains behind untouched. 



Polyporus (Fomes) fiilvus (Scop.) (Britain). Sporophores 

 woody and very hard, at first hairy but later smooth, dark, 

 and cracked ; in form they are tuberous or triangular. In- 

 ternally they show no stratification. The fungus is very common 

 on living plum where it causes undoubted injury ; it also occurs 

 on hornbean and aspen. 



Polyporus fulvus var. Oleae Scop. In northern Italy 

 may be frequently observed a peculiar splitting of the stems 

 of olive trees into two or more portions ; the fissures occur 

 generally on the lower parts of the tree, and may extend so 

 deeply that the stem appears to stand on stilts or props. 

 Hartig ^ ascribes this phenomenon to the presence in the olive 

 stems of the mycelium of Polyporus fulvus causing rotten places 

 which are cut out by the Italian cultivators ; the disease, how- 

 ever, continuing to make progress, it may be necessary in course 

 of time to cut so deeply into the stem, that tracts extending 

 right through may be removed ; this takes place all the more 

 rapidly if several diseased spots are being simultaneously 

 operated on. The destruction of the olive-wood by this parasite 

 is similar to that produced by P. igniarius on oak and other 

 trees. The sporophores appear on rotten spots, but are gener- 

 ally quickly removed by the cultivator. Infection takes place on 

 wounds, hence it is advisable at once to apply tar after cutting 

 out any decayed wood, and also to paint pruning-cuts or other 

 exposed surfaces with tar. Neighbouring fruit-trees, liable to 

 suffer from this same fungus, should be similarly treated, both 

 for their own safety and that of the olive trees. 



Polyporus (Fomes) Hartigii Allescher"'^ (P. igniarius var. 



^R. Hartig, " Die Spaltung der Oelbaume. " Forstlich-naturwiss. Zeitschri/t, 

 1893. 



' R. Hartig, Zersetzunc/serscheinunrjen, PI. YII. Forstlich-naturwiss. Zeit- 

 schri/t, 1893, p. 61. 



