REPORTS BY THE HONORARY SCIENTISTS. 153 



REPORTS BY THE HONORARY 

 SCIENTISTS. 



Report by A. W. Borthwick, B.Sc, Honorary Consulting 

 Cryptogamist. 



Among the specimens sent in during the past year, the follow- 

 ing are some of the more important : — 



Trametes radicipei-da. — This fungus is described as the most 

 dangerous parasite of our conifers. It may attack trees from five 

 to a hundred years old, and occurs on Piniis, sylvestris and Strohus, 

 Picea excelsa, Abies pectinata, and Juniperus communis. The 

 sporaphores are large white bodies which form white incrustations 

 on the roots or at the base of the stem. On careful examination 

 the surface will be seen to be perforated by numerous small holes 

 or pores. The spores are produced in large numbers in these 

 cavities, they will germinate easily in moisture, and can e£fect an 

 entrance into the living cells through unwounded bark. They 

 are carried underground from one tree to another on the fur of 

 rabbits and mice. Again, where an infected root comes in 

 contact with a healthy one, the myceliuoa may pass from the one 

 to the other. 



The disease is first indicated by an apparently vigorous tree 

 becoming pale green and ultimately dying. Others around it 

 begin to go the same way, whether the first one be cut down or 

 not. The disease thus spreads in a centrifugal direction, causing 

 gaps or blanks in the plantation. If there has been more than 

 one starting-point, then the circles in a few years become 

 confluent. 



An examination of the roots reveals the presence of a fine 

 white mycelium below the bark scales; from this mycelium the 

 sporaphores arise, first like little papillae, but rapidly becoming 

 larger, till ultimately they may measure 30-40 cm. across. The 

 mycelium spreads through the attacked root, and also up to the 

 stem base, whence it can gain access to all the other roots. When 

 this happens, the tree is rapidly killed. The mycelium also 

 spreads some distance up the wood-body of the stem (except in 

 pines). Its presence in the wood causes at first a violet dis- 

 coloration; later, numerous white spots with black centres 



