1896.] ESSAYS. Ill 



called Agarieus melleus, the honey mushroom. This is an especially 

 variable species, that is to say, while it always presents certain import- 

 ant features, as that its spores are white, its gills attached to the stem, 

 etc., yet in such respects as size and color, shape of stem and of cap, 

 scaliness of surface, etc., it varies enormously, so that two varieties 

 of this one species may be as unlike to the casual or even somewhat 

 educated glance, as if they belonged to two different genera. But in 

 all its forms it gets its living from woody tissue, and is very apt to be 

 found where there is a decaying stump ot log. For this statement 

 you- are (piite prepared, l)ut it was certainly a great surprise to me to 

 leai'u how great and general a pest this harmless looking toadstool is 

 in our forests. It makes its way into a living tree, rots the wood so 

 as to spoil the timber and finally quite kills the tree. Meanwhile there 

 is nothing to show the casual observer what is at the bottom of the 

 mischief. How does this come about? 



The mycelium or plant of the honey mushroom is like a network of 

 branching root-like fibres underground. At the apex of a mycelial 

 branch the cells possess the power of secreting a ferment, and if this 

 apex in its growth underground meets the root of a tree this ferment 

 softens the outer cells of the root so that the fungus can penetrate it. 

 Once inside it finds abundant nourishment in the sap, and it grows 

 and extends ; it finds its way into the softer and more succulent parts 

 of the tree between the bark and the hard wood, and in that region 

 extends without restraint. It absorbs to itself, not only the food 

 which the tree prepares for its own growth, but the very tissues of 

 the tree itself, which usually dies within a year from the first entrance 

 of the fungus. Meanwhile the fungus growth, however extensive, 

 shows few of the characteristics of a mushroom ; you may find 

 either l)road white ribbon-like masses under the bark, or dark brown 

 bands of mycelium about the trunk. No mushrooms are to be seen, 

 except perhaps a few at point of junction of roots and trunk. It is 

 only after long and most difficult investigation that it has been shown 

 that what had been thought to be a distinct form of vegetation is only 

 the overfed and sterile mycelium of the Armillaria mellea, and that in 

 this way the common honey mushroom is a serious enemy in the culture 

 of forest trees. 



We see then that fungi, the larger as well as the microscopic ones, 

 are seriously destructive to living vegetation, but it by no means 

 follows that therefore fungi are foes to vegetation in general. For in 

 the first place consider what becomes of the tree which the honey 

 mushroom has killed. It is at once, almost in its entirety, added to 



