230 PHYTOPHTHORA SP. ON HEVEA BRASILIENSIS 



average of 50 measurements gives the length as 28'5/x and breadth as 20*4/* ; 

 the proportion of breadth to length being 100 : 140. Thus they are smaller 

 than those of Ph. Faberi which measure 42 — 80 x25 — 30/* according to von 

 Faber. The zoospores of the Burma species measure 7*5 — 12*5 X 5*0 — T'bfx 

 (those of Faberi are not given), and the number of zoospores emitted from a 

 single sporangium got from the fruits varies from 3 — 10 whereas von Faber 

 has observed as many as 20 zoospores arising from a single sporangium. 

 According to Rorer^ sporangia of Ph. Faberi from cacao measure 

 30— 60 X 21— 30m, usually 30— 50 X 25— 27/i and emit from 15—30 zoospores. 

 What von Faber and Coleman call oospores are really resting conidia or 

 chlamydospores similar to those found in Ph. parasitica, Ph. Colocasice, 

 and Ph. infestans. They measure 22 — 45/u according to these authors and 

 according to Rorer 30 — 50/x. Those of the Burma fungus are much smaller 

 and measure 17—34/* in diameter. 



Peters^ has described a disease of Hevea fruits in the Cameroons caused 

 by a Phytophthora but he considers its identity with Ph. Faberi to be doubtful. 

 From his scanty account of the disease it is not possible to say with certainty 

 whether it is similar to the one found on Hevea fruits in Burma. But judging 

 from the measurement given by him it seems probable that the fruit disease 

 in the Cameroons is allied to that found in Burma. The sporangia on the 

 diseased fruits in Burma are slightly smaller than those on the diseased fruits 

 in the Cameroons, where the proportion of breadth to length is 100 : 144, but 

 those produced in pure cultures are 'similar in both the cases. Similarly the 

 resting spore (called by Peters oospores) are bigger on the fruits in the 

 Cameroons than those found in Burma but those produced in pure cultures 

 are of the same size. 



Remedial Measures. 



In a previous paper^ preventive measures to check the disease have been 

 suggested, viz., thinning out thickly planted areas, systematic removal of 

 diseased fruits and stopping of tapping on trees attacked by " Black Thread." 

 In Java, Rutgers* recommends the treating 'of the affected bark with a 

 solution of 20% carbolineum plantarium every 5 days and of removing from 



' Rorer, J. B. Pod-Rot, Canker and Chupon-Wilt of Cacao caused by Pfiytophthora sp. 

 Bull, of Trinidad Dcpt. Agri., IX, No. 05, 1910. p. 91. 



2 Peters. Uber cine Fruchtfiiule von Hevea brasiliensis in Kanierun. Ber. iib. d, Tatlg- 

 keit d. Kais. Biol. Anst. im Jalire 1911. Mitt. Kais. Biol. Anst. 1912, No. 12. 



8 Dastur, J. F. loc. cit. 



* Rutgers, A. A. L. and Arens, P. loc. cit., p. 9, and 

 Rutgers, A. A, L. and Dammerman, K. W. loo. cit., p. 31. 



