278 TRAXSACTIOXS OF ROYAL SCOTTISH ARBORICULTUKAL SOCIETY. 



Agaricus melleus. 



This ruushroom or honey fungus, although a less pronounced 

 parasite, is not less destructive; the details of its action on the 

 timber, and its mode of spreading from root to root in the soil by 

 means of its long, purple-black cord-like mj'^celium strands, also 

 differ. These threads extend themselves under the surface of the 

 soil, push their way into the bark of the roots with which they 

 happen to come in contact, and develop themselves under it as 

 long, ribbon-like filaments, ultimately causing the death of both 

 young and old trees. Infected plants exhibit a sti-ong outflow of 

 resin at the base of the stem, which penetrates and cements the 

 soil round the foot of the tree. Characteristic features of its 

 occurrence are the dying off of the plants here and thei-e in patches ; 

 the rapidity with which plants in excellent growth are attacked 

 and killed off, after having, perhaps the same year, developed very 

 good growth in height; and the large numbers of tawnj"- coloured 

 mushrooms round the root of the tree. 



Periderniium jnni. 



Of all the fungous diseases which affect pines, none is more 

 interesting, and few more disastrous, than one induced by a form 

 long known as Peridermium pini. This disease makes its appear- 

 ance as bladder-like bags of spores protruding from the leaves or 

 cortex, and springing from the mycelium which desti-oys the cell- 

 tissues; in consequence of this the growth of the tree ceases at 

 these places. The damage done by the cortical form is twofold in 

 character. In the first place, the cortex and cambium are killed 

 at the spot invaded, and this injury may go so far as to ring the 

 stem or branch. Then, in the second place, an abnormal formation 

 and excretion of turpentine is incited and soaks into the wood, 

 and renders the passage of water upwards difficult or impossible 

 The natural consequence is the perishing of the whole part above 

 the infected places, and in dry summers such a result is apt to 

 follow rapidly. The dying off of the tops of old pines is very often 

 caused by this fungus. 



J^cidium ela.tinum. 



When going through silver fir woods, a very frequent sight is a 

 few of the silvers broken over, and on looking closely it is found 

 that they have broken over at a dry, bare part or cankerous 

 swelling of the stem ; this is invariably caused by the silver fir 



