2:^2 



NATURE 



[yau. 12, I 



The tree was felled by sawing close to the roots : the 

 interior was hollow for several feet up the stem, and two 

 of the main roots were hollow as far as we could poke 

 canes, and no doubt further. The dark-coloured rotting 

 mass around the hollow was wet and spongy, and consisted 

 of disintegrated wood held together by a mesh-work of 

 the rhizomorphs. Further outwards the wood was yellow, 

 with white patches scattered in the yellow matrix, and, 

 again, the rhizomorph-strands were seen running in all 

 directions through the mass. 



Not to follow this particular case further — since we are 

 concerned with the general features of the diseases of I 

 timber — I may pass to the consideration of the diagnosis [ 

 of this disease caused by Agan'cus vicllciis, as contrasted j 

 with that due to Traineies radiciperda. \ 



Of course no botanist would confound the fructification 

 of the Tramctes with that of the Agaricus ; but the fructifi- 

 cations of such fungi only appear at certain seasons, and 

 that of Tramctes radiciperda may be underground, and 

 it is important to be able to distinguish such forms in the 

 absence of the fructifications. 



The external symptoms of the disease, where young 

 trees are concerned, are similar in both cases. In a 

 plantation at Freising, in Bavaria, Prof. Hartig showed 

 me young Weymouth pines {P. Strobiis) attacked and 

 killed by Ai^aricus ntel/eus. The leaves turn pale and 

 yellow, and the lower part of the stem —the so-called 

 "collar'' — begins to die and rot, the cortex above still 

 looking healthy. So far the symptoms might be those 

 due to the destructive action of other forms of tree-killing 

 fungi. 



On uprooting a young pine, killed or badly attacked by 

 the Agaric, the roots are found to be matted together with 

 a ball of earth permeated by the resin which has flowed out : 

 this is very pronounced in the cise of some pines, less so 

 in others. On lifting up the scales of the bark, there will 

 be found, not the silky, white, delicate mycelium of the 

 Tramctes, but probably the dark cord-like rhizomorphs : 

 there may also be flat white rhizomorphs in the young 

 stages, but they are easily distinguished. These dark 

 rhizomorphs may also be found spreading around into the 

 soil from the roots, and they look so much like thin roots 

 indeed that we can at once understand their name — 

 rhizomorpb. The presence of the rhizomorphs and (in the 

 case of the resinous pines) the outflow of resin and stick- 

 ing together of soil and roots are good distinctive features. 

 No less evident are the differences to be found on 

 examining the diseased timber, as exemplified by Prof 

 Hartig's magnificent specimens. The wood attacked 

 assumes brown and bright yellow colours, and is marked 

 by sharp brown or nearly black lines, bounding areas of 

 one colour and separating them from areas of another 

 colour. In some cases the yellow colour i? quite bright — 

 canary yello-v, or nearly so. The white areas scattered 

 in this yellow matrix have no black specks in them, and 

 can thus be distinguished from those due to the Tramctes. 

 In advanced stages the purple-black rhizomorphs will be 

 found in the soft, spongy wood. 



The great danger of Agaricus melieus is its power of ex- 

 tending itself beneath the soil by means of the spreading 

 rhizomorphs : these are known to reach lengths of several 

 feet, and to pass from root to root, keeping a more or less ! 

 horizontal course at a depth of 6 or 8 inches or so in the | 

 ground. On reaching the root of another tree, the tips of j 

 the branched rhizomorph penetrate the living cortex, and [ 

 grow forward in the plane of the cambium, sending off | 

 smaller ramifications into the medullary rays and (in the \ 

 case of the pines, &c.) into the resin passages. The j 

 hyphae of the ultimate twigs enter the tracheides, vessels, i 

 &c., of the wood, and delignify them, with changes of j 

 colour and substance as described. Reference must be 

 made to Prof Hartig's publications for the details which : 

 serve to distinguish histologically between timber attacked 

 by Agaricus melieus and by Tramctes or other fungi. ■ 



Enough has been said to show that diagnosis is possible, 

 and indeed, to an expert, not difficult. 



It is at leas); clear from the above sketch that we cm ' 

 distinguish these two kinds of diseases of timber, and it 

 will be seen on re:lection that this depends on know- 

 ledge of the structure and functions of the timber and 

 cambium on the one hand, and proper acquaintance with 

 the biology of the fungi on the other. It is the victory of 

 the fungus over the timber in the struggle for existence 

 which brings about the disease ; and one who is ignorant 

 of these points will be apt to go astray in any reasonini^ 

 which concerns the whole question. Anyone knowing 

 the facts and understanding their bearings, on the 

 contrary, possesses the key to a reasonable treatment of 

 the timber ; and this is important, because the two 

 diseases referred to can be eradicated from young planta- 

 tions and the areas of their ravages limited in older 

 forests. 



Suppose, for example, a plantation presents the follow- 

 ing case. A tree is found to turn sickly and die, with 

 the symptoms described, and trees immediately surround- 

 ing it are turning yellow. The first tree is at once cut 

 down, and its roots and timber examined, and the 

 diagnosis shows the ^restncG oi Agaric i/s melieus or of 

 Tramctes radiciperda, as the case may be. Knowing this, 

 the expert also knows more. If the timber is being 

 destroyed by the Tramctes, he knows that the ravaging 

 agent can travel from tree to tree by means of roots 

 in contact, and he at once cuts a ditch around the 

 diseased area, taking care to include the recently-infected 

 and neighbouring trees. Then the diseased timber is 

 cut, because it will get worse the longer itstmds, and the 

 diseased parts burnt. \i Agaricus melieus is the destroy- 

 ing agent, a similar procedure is necessary ; but regard 

 must be had to the much more extensiv^e wanderings of 

 the rhizomorphs in the soil, and it may be imperative to 

 cut the moat round more of the neighbouring trees. 

 Nevertheless, it has also to be remembered that the 

 rhizomorphs run not far below the surface. However, 

 my purpose here is not to treat this subject in detail, 

 but to indicate the lines along which practical applica- 

 tion of the truths of botanical science may be looked 

 for. The reader who wishes to go further into the sub- 

 ject may consult special works. Of course the spores 

 are a source of danger, but need be by no means so 

 much so where knowledge is intelligently applied in 

 removing young fructifications. 



I will now pass on to a few remarks on a class of 

 disease-producing timber fungi which present certain 

 peculiarities in their biology. The two fungi which have 

 been described are true parasites, attackmg the roots 

 of living trees, and causing disease in the timber by 

 travelling up the cambium, &c., into the stem : the fungi 

 I am about to refer to are termed wound-parasites, 

 because they attack the timber of trees at the surfaces 

 of wounds, such as cut branches, torn bark, frost-cracks, 

 &c , and spread from thence into the sound timber. When 

 we are reminded how many sources of clanger are here 

 open in the shape of wounds, there is no room for wonder 

 that such fungi as these are so widely spread. Squirrels, 

 rats, cattle, &c., nibble or rub off bark ; snow and dew 

 break branches ; insects bore into stems ; wind, hail, &c., 

 injure young parts of trees ; and in fact small wounds are 

 formed in such quantities that if the fructifications of such 

 fungi as those referred to are permitted to ripen indis- 

 criminately, the wonder is not that access to the timber 

 is gained, but rather that a tree of any considerable age 

 escapes at all. 



One of the commonest of these is Polyporus sulphureus, 

 which does great injury to all kinds of standing timber, 

 especially the oak, poplar, willow, hazel, pear, larch, and 

 others. It is probably well known to all foresters, as its 

 fructification projects horizontally from the diseased 

 trunks as tiers of bracket-shaped bodies of a cheese-like 



