107 



The mycelium takes the form of light brown threads when young, 

 and becomes later expanded over the surface of the root in the form 

 of sheets, and collected here and there into nodules. The sheets of 

 mycelium are dark in colour on the surface, and white or light brown 

 beneath. 



In Ceylon the progress of the disease is said to be very slow, and 

 observations which have been made in this country up to the present 

 confirm this. In some cases where the tap root was attacked, it has 

 been found that adventitious roots have arisen, and having grown 

 vertically downwards have taken the place of the tap root, -a further 

 indication of the slow progress of the disease. At each centre of 

 infection one or two trees only have been found to be diseased, and 

 each case has been found to be the result of a separate infection. 



The mycelium appears to be incapable of spreading independently- 

 through the soil, and infection can, therefore, only occur by the con- 

 tact of a diseased with a healthy root. The growth of the mycelium 

 is, however, so slow that the attacked tree is dead some time 

 before the fungus has spread to the adjacent trees. Where two ad- 

 jacent trees are attacked simultaneously, each has become infected 

 separately from one or more jungle stumps. If the dead tree be left 

 standing for some time the disease may spread to the adjacent trees. 

 To illustrate the slow progress of the disease Mr. Fetch, •Mycologist, 

 Royal Botanic Gardens, Ceylon, cites the following instance : — '* Hevea 

 was planted, 14 feet apart, in single line round the boundary of an old- 

 established Cacao estate. When the trees were eight years old, one of 

 them died, from brown root disease as was subsequently discovered. 

 The tree was left standing and allowed to deca3\ Two years later 

 the next tr^e in the line died and was likewise left todeca}'. After a 

 further two years had elapsed, the next tree in the same direction 

 along the line failed to recover after wintering, and w^as evidently 

 dying; and an examination of this tree and the two old decaying 

 stumps proved that they had all been killed b}^ brown root disease." 



In Samoa and in West Africa, the disease appears to be more 

 ^icrious than either in Ceylon or in this countr3\ When reported at 

 Kew from West Africa the disease was said to spread somewhat 

 rapidly, and in Samoa it has been said to cause considerable injury to 

 breadfruit {Artocarpus incisa.) 



The youngest age of an attacked tree which has been recorded in 

 this country is three years. 



Sprcail. 



From what is known of the fungus it is unquestionably a jungle 

 product, and, from the long list of cultivated plants which it attacks 

 one might infer that in the jungle it does not confine itself to any 

 small number of hosts. 



