384 DIVISION III. — MODE OF LIFE OF THE FUNGI. 



trunks of trees, wooden conduit-pipes, &c. But the strands also make their way from 

 the soil through the uninjured living rind into the roots of healthy living trees, especially 

 our Coniferae ; there they destroy the inner rind and then grow at its expense into the 

 subcortical expansions described above, from which hyphae push on further through 

 the medullary rays into the wood. "While the mycelium is spreading at these spots 

 and mounting in the stem, it kills the living tissue and ultimately the whole tree. The 

 propagation of the Fungus from tree to tree by means of the mycelial strands 

 spreading far and wide in the soil has been already described. The symptoms of 

 disease which precede death in fir-trees are known as ' resin-flux ' 1 (' Harzsticken, 

 Harzuberfulle ') and the phenomena attending the decomposition of the wood, which 

 advances with the spread of the Fungus, should be learnt from Hartig's excellent 

 descriptions 2 . 



Trametes radiciperda of Hartig (Polyporus annosus, Fr)., which attacks the 

 wood^of fir-trees from the roots and kills it, comes nearest to Agaricus melleus in its 

 mode of life and operation, but it has not the rhizomorphous strands. The 

 filamentous mycelium penetrates from without into the uninjured rind of the roots, 

 whether it has developed directly from the spores or, as is most conducive to 

 the spreading of the Fungus, has grown out of an infected root in moist soil and 

 has encountered a sound root in contact with the first. It has been observed to put 

 out germ-tubes capable of infecting in less than twenty-four hours in a moist environ- 

 ment. Whether it can arrive at its full development when growing as a pure 

 saprophyte on dead wood is still uncertain, but according to some observations of 

 Hartig it is probable ; at any rate it would appear to be adapted rather for strict than 

 for facultative parasitism. 



R. Hartig has also made us acquainted with a number of other Hymcnomycetes 

 which produce decompositions of the wood of living trees in forms varying with each 

 species, and thus kill the plants; Trametes Pini, Polyporus fulvus, P. vaporarius. 

 P. mollis, and P. borealis in fir-trees ; Hydnum diversidens, Thelephora Perdix, Poly- 

 porus sulphureus, P. igniarius, P. dryadeus, and Stereum hirsutum in the oak. It is 

 probable that there are many other wood-destroying Fungi which approach the above 

 in the qualities just indicated. 



All these Fungi attack the wood from places exposed by wounds and do not 

 penetrate into it through the uninjured rind, with the exception of Polyporus mollis, 

 in which this point has not yet been cleared up. 



It is probable therefore that they are fed and made capable of infecting chiefly 

 by the products of the decomposition of the superficial wound-layers which have 

 been laid bare and killed, in the same way therefore as the Sclerotinieae are facultative 

 parasites; but no satisfactory experiments have been made to ascertain this point. 

 On the other hand it is tolerably certain that Stereum hirsutum often attains to its 

 perfect development as a saprophyte in dead wood. We have no certain knowledge 

 on this point in the case of the other species which have been named. 



1 [There appears to be in use no English equivalent of the expression Harzsticke and Harzuber- 

 fulle ; the word resin-flux is therefore introduced as indicating a prominent symptom of the disease, 

 although it is not an exact rendering of the German tcrms.J 



 See above, page 23. 



