205 



The canker " fungus of Hevea requires further careful investiga- 

 tion ; it is desirable that a large number of inoculations be performed 

 with the fungus both on the pods and on the stem, for the purpose of 

 establishing with some certainty its effect on the plant. Much remains 

 to be done on the dispersal of the fungus and on its mode of entrance 

 into the host, its capacity for living and reproducing itself on dead 

 parts of the plant and its range of hosts in this country, in order that 

 some accurate knowledge may be obtained of such important factors 

 as the facility with which the disease may be spread by a tapping 

 knife, the capacity of the fungus for passing from the fruits into 

 the young branches with production of disease in them, — in fact, in 

 order that some accurate knowledge may be obtained of the methods 

 of treatment which are likely to prove most serviceable in combat- 

 ting the disease. 



In view of these considerations, it is proposed during the fruiting 

 season to form an estimate of the amount of the disease in this country, 

 and to carry out such inoculation experiments as will lead to some 

 knowledge of the life-history of the fungus and of the disease which 

 has been attributed to it. 



Before concluding this note on the "canker" disease of Hevea it 

 is desirable to refer somewhat briefly to two fungi which occur on 

 Hevea in this country, and which are regarded by some as being the 

 cause of a disease to which the name "canker" is given. One of these 

 fungi, Nectria diversispora, has been mentioned above ; the other is 

 Stilhelhi I^eveae. The fact that these two fungi are regarded by some 

 as parasites on Hevea, coupled with the fact that they are frequently 

 associated with effects on the tapping surface, which at first appear 

 to be pathological, has led me to make investigations on the two fung 

 in order determine whether they existed merely as saprophytes or 

 whether they were capable or causing any injury to the plant. 



Nectria diversispora was originally described by Fetch on dead 

 branches of Hevea and of Thea viridis; it was considered by him to be 

 a saprophyte. Inoculation experiments described by him in the 

 Tropical Agriculturist, Dec, 1909, served to show the harmless 

 nature of the fungus. In this country the fungus occurs freely on 

 dead twigs and branches of Hevea, on the dead parts of the trunk, and 

 on the wood exposed by the splitting or breaking of the trunks. It 

 takes the form of minute, red points which are sometimes aggregated 

 in large numbers, each individual body being just visible to the naked 

 eye. This is the mature form of the fungus, the Nectria stage. This 

 stage is usually preceded by a white mould which is composed of two 

 forms, a Spic aria-form, and a Fusarium-iorm. 



The ripe ascospores of the Nectria w^ere found to germinate in a 

 1% cane sugar solution in about 24 hours and to give rise to a mycelium 

 which produced the Spicaria-form. In plate cultures, on agar-agar 

 and a 10% extract of the juice of the sugar cane, the Spicaria-form 

 appeared in five or six days and almost simultaneously the Fusarium- 



