228 



NATURE 



{Jan. 5, 1888 



well, such forms will be found on examination to have 

 numerous minute pores on the under side or on the upper 

 side of their cheese-like, corky, or woody substance, and 

 the spores which reproduce the fungus are developed on 

 the walls lining these many pores, to which these fungi 

 owe their name. Irametes radiciperda is one of those 

 forms which has its pores on the upper side of the spore- 

 bearing fructification, and presents the remarkable pecu- 

 liarity of developing the latter on the exterior of roots 

 beneath the surface of the soil (Fig. 11). 



This is not the place to discuss the characters of species 

 and genera, nor to enter at any detail into the structure 

 of fungi, but it is necessary to point out that in those 

 cases where the casual observer sees only the fructifica- 

 tion of a Polyporus, or of a toadstool, or of a mushroom 

 (projecting from a rotting stump or from the ground, for 



Fig. II — Portion of root of a spnice-fir, with fructification of Trainetcs 

 radiciperda (after Hartig). Each fructification is a yellowish-white 

 mass of felt-like substance spread over the root, and with minute pores, 

 in which the spores are produced, on its outer surface ; the mycelium 

 which has developed it is in the interior of the root. 



instance), the botanist knows that this fructification is 

 attached to, and has taken origin from, a number of fine 

 colourless filaments woven into a felt-like mass known as 

 the mycelium, and that this felt-work of mycelium is 

 spreading on and in the rotten wood, or soil, or whatever 

 else the fungus grows on, and acts as roots, &c., for the 

 benefit of the fructification. 



Now, the peculiarity of the mycelium of this Trametes 

 radiciperda is that it spreads in the wood of the roots 

 and trunks of pines and firs and other Conifers, and takes 

 its nourishment from the wood-substance, &c., and it is to 

 the researches of Hartig that we owe our knowledge of 

 how it gets there and what it does when there. He found 

 that the spores germinate easily in the moisture around 

 the roots, and put forth filaments which enter between the 

 bark-scales, and thus the mycelium estabhshes itself in 

 the living tree, between the cortex and the wood (Fig 12), 



It is curious to note that the spores may be carried from 

 place to place by mice and other burrowing animals, since 

 this Trametes is apt to develop its fructification and 

 spores in the burrows, and they are rubbed off into the 

 fur of the animals as they pass over and under the spore- 

 bearing mass. 



When the mycelium obtains a hold in the root, it soon 

 spreads between the cortex and the wood, feeding upon, 

 and of course destroying, the cambium. Here it spreads 

 in the form of thin flattened bands, with a silky lustre, 

 making its way up the root to the base of the stem, 

 whence it goes on spreading further up into the trunk 

 (Fig. 12). 



Even if the mycelium confined its ravages to the cam- 

 bial region, it is obvious, from what was described in 

 Articles I. and II., that it would be disastrous to the tree ; 

 but its destructive influence extends much further than 

 this. In the first place, it can spread lo another root 



Fig. 12. — Piece of root of spruce-fir, with the mycelium of Trametes radici- 

 perda (after Hartig) enlarged about 3 limes. The white mycelium 

 spreads in a fan-like manner over the surface beneath the cortex, as 

 seen in the figure where the latter has been lifted and removed (n). Here 

 and there the mycelium bursts through the cortex in the form of white 

 protuberances (J}), to form the fructifications. 



belonging to another tree, if the latter comes in contact 

 in the moist soil with a root already infected ; in the second 

 place, the mycelium sends fine filaments in all directions 

 into the wood itself, and the destructive action of these 

 filaments — called hyphfe — soon reduces the timber, for 

 several yards up the trunk, to a rotting, useless mass. 

 After thus destroying the roots and lower parts of the 

 tree, the mycelium may then begin to break through the 

 dead bark, and again form the fructifications referred to. 



Since, as we shall see, Trametes radiciperda is not the 

 only fungus which brings about the destruction of stand- 

 ing timber from the roots upwards, it may be well to see 

 what characters enable us to distinguish the disease thus 

 induced, in the absence of the fructification. 



The most obvious external symptoms of the disease in 

 a plantation, &c., are : the leaves turn pale, and then 

 yellow, and die off; then the lower part of the stem 

 begins to die, and rots, though the bark higher up may 

 preserve its normal appearance. If the bark is removed 



