Page:The Oak.djvu/177

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cases: some of the fungi destroy the vessels, fibers, etc., by dissolving their walls from inside, while others destroy the part common to contiguous cells, etc., and thus first isolate the elements and then complete the destruction. A series of very interesting researches by

Fig. 43.—Oak timber destroyed by the fungus Hydnum diversidens: a shows the medullary rays on the tangential section; b, a mass of felted mycelium. (R. Hartig.)

Hartig has demonstrated that the presence of these timber-destroying fungi can be detected from the markings and discolorations they produce in the wood; those due to Hydnum diversidens, Thelephora Perdix, Polyporus sulphureus, P. igniarius, P. dryadeus, and Stereum