JEHANGIR FARDUNJI DASTUR 225 



to an excess of moisture on the layer exposed to the rain during tapping and 

 not due to any pathogenic cause, because he failed to reproduce this decay by 

 means of organisms found in the decayed bark. He does not enumerate them 

 but presumably he did not find a PJiytophthora among them. The writer 

 found in Burma that the decaying bark was soon overrun by saprophytic fungi 

 like Fusarium, Cephalosporiwn and Sjncaria, especially the first. To see if 

 any of them was able to cause " Black Thread "tapped areas were inoculated 

 with pure cultures of these fungi but in all cases negative results were obtained. 

 The sporangia of Phytophthora are very rarely formed on the diseased stem in 

 Burma, and the writer succeeded in getting the sporangia from the incubated 

 decayed bark only in a few cases after many attempts and that, too, when a 

 thick piece from the diseased part of the stem was incubated after washing the 

 piece in corrosive sublimate. Even then a pure growth of the fungus was not 

 obtained as there was also a Fusarial growth. 



Petch'si account of Hevea pods attacked by Phytophthora in Ceylon may 

 well apply to the diseased pods in Burma, but in Ceylon the fungus from the 

 fruit may grow through the stalk into the branch and kill it for some distance, 

 while in Burma the disease from the fruit has not been found to travel on to 

 the stalk and thence to the branch, though diseased fruits have been found 

 hanging on the trees for several weeks. In the case of a fruit badly attacked 

 by Phijtophthora in Burma, the woody shell underneath the diseased soft rind 

 shows black discoloured areas. On sectioning these, Botryodiplodia hyphse 

 have been foimd in the tissues. This fungus from the woody shell has been 

 found to travel on to the thalamus ; and from there it may reach the fiuit 

 stalk and eventually kill it. Petch^ has shown that Botryodiplodia Theo- 

 bromeoi Pat. may follow an attack of Glceosporimi on Hevea branches ; similarly 

 it is possible that on the fruit in Burma Botryodiplodia follows an attack of 

 Phytophthora and then spreads to the fruit stalk. It seems probable, therefore, 

 that in Ceylon also the death of the fruit stalk may be due to Botryodiplodia 

 and not due to Phytophthora as supposed by Petch, especially since he says that 

 Phytojihthora has not been isolated from diseased fruit-bearing shoots. 



In Ceylon Ph. Faberi has been found to attack the collar and the roots 

 as well, in fact all parts of the tree, except leaves. But McRae and Sundara- 

 raman,3, who have studied in Travancore and Cochin a disease of Hevea which 

 they consider to be due to Ph. Faberi, have found the presence of this fungus 



1 Fetch, T. loc. cit. 



2 Petch, T. Physiology and Diseases of Hevea Brasiliensis, 1911, p. 220. 



8 McRae, W. and Sundararaman, S. Leaf-fall of Hevea. The Planters' Chronicle, X, 

 No. 37, 1915, p. 452. 



