228 phYtophtHora sP. on hevea brasIliensIs 



as " Bark Kot," " Decay of renewing bark," and sometimes as " Dieback," 

 and this " Bark Rot," according to him, is capable of explanation on 

 purely physiological grounds.^ 



From the above account it is clear that on Hevea there are two distinct 

 forms of disease caused by PhytopJitJwra, one causes canker in Ceylon, 

 Borneo, Java and Sumatra, identical with the cacao canker ; and it is significant 

 that this Hevea canker does not cause much damage on plantations of 

 Hevea only, but is decidedly more serious on mixed Hevea and cacao plantations. 

 The other form causes black stripes on the tapping area. This is found in 

 Borneo, Java and Sumatra, along with the former disease ; and in Burma, 

 Cochin and Travancore by itself. Furthermore, the decay of renewing bark, 

 first recorded by Petch^ in Ceylon, is due to the second form and not due to 

 wet condition as supposed by him. 



It seems clear that we have on Hevea two diiTerent species of Phytoflithora 

 causing two distinct kinds of diseases instead of one fungus causing two distinct 

 symptoms of one disease. Of these two different species one is Ph. Faberi 

 which causes Hevea canker identical with that of cacao as shown by the 

 inoculation experiments of Fetch and Rutgers ; and the other species causes 

 " Streepjeskanker " or " Black Thread " disease as seen from the inoculation 

 experiments made by Rutgers in Java and by me in Burma. 



This veiw of there being two diseases of Hevea stem caused by two species 

 of PhytopJithora is strengthened by inoculation experiments and by morpholo- 

 gical study. 



Fruits and cuttings of Theohroma Cacao, kindly furnished by Mr. C. D. 

 Mahaluxmiwala, Superintendent, Municipal Gardens, Bombay, and by Mr. 

 H. E. Houghton, Superintendent, Agri-Horticultural Gardens, Madras, were 

 inoculated with pure cultures of Phytophthora taken from Hevea fruits in Burma. 

 Four cacao fruits, one about one and a half inch long and the other three about 

 four to five inches long, were inoculated either with zoospores or with 

 vigorously growing mycelium fi-om pure cultures. Two wore inoculated 

 through cuts made on the surface and the other two were inoculated on the 

 unwounded surface. Though these fruits were kept in moist chambers for over 

 a fortnight, there was absolutely no trace of the inoculation succeeding. Four 



1 Bryce, G. Eeport of the Acting Botanist and Mycologist. Trop. Agr., XLVII, No. 1, 

 1916, p. 29. 



a Fetch, T. Cacao and Hevea Canker. Circs. & Agri. Jour. Roy. Bot. Card., Ceylon, V, 

 No. 13. 1910, p. 160. 



