260 PHYTOPHTHORA MEADlI n. Sp. ON HEVEA BRASlLlENSIS 



in the jungle ; still, since I made the suggestion at a planters' meeting in 1916, 

 I have had no positive case reported. That rather discounts the possibility 

 of the fimgus having passed to Hevea from trees in the country. Another 

 possibility is that the disease was introduced along with plants and seed 

 (possibly fruits) that were imported in considerable numbers from Ceylon. 

 It is quite possible that P. Meadii occurs in Ceylon, for the only definite report 

 is that of Fetch in 1910 who successfully inoculated 6 Hevea stems out of 13 

 by means of spores of Phytophthora obtained froin diseased cacao fruits and 

 of pieces of diseased cacao pods, and concluded from this experiment that the 

 canker and fruit-disease of Hevea are caused by P. Faberi which is the 

 cause of canker and pod-disease of cacao. No detailed description of the 

 Phytophthora on Hevea fruits in Ceylon has been published. Seeing that both 

 P. Meadii and P. Faberi infect Hevea fruits readily, and that cacao is grown 

 as an estate crop in Ceylon, it is quite likely that it is P. Faberi that is 

 attacking Hevea there, though this does not preclude the possibihty of 

 P. Meadii being present also. 



Dissemination of the fungus. 



The fungus appears to start its activity after the dry season at compara- 

 t ively few points, but when the monsoon has once burst, it spreads rapidly on 

 fruits and then to leaves. Sporangia are produced on the surface of the fruits 

 in \ery large numbers indeed, and the zoospores in correspondingly greater 

 numbers. The rapid dissemination from the first few infected fruits can be 

 explained by rain-drops that fall on these infected fruits splashing the spores 

 considerable distances to other fruits. Faulwetter^ in an illuminating and 

 suggestive paper showed by experiment that water is splashed by a falling 

 drop only when it falls upon a film of water, and it is the water of the film 

 which composes the splash-drops. A drop '02 c.c. in volume falling 16 feet on 

 to a horizontal glass slide covered with a film of water splashed drops to 

 24 inches, on a pl;ate inclined at 45° to 28 inches and on a plate incHned at 

 30° to 46 inches. When the plate was at 7 feet above the surface of the 

 counter, the distances were in the 1st and 3rd cases 42 and 66 inches 

 respectively. He also found that in wind driven by an electric-fan and 

 travelUng at 10 miles an hour at the point of splash which was 3 feet above 

 the floor, a drop falling 16 feet splashed drops to an extreme distance of 18 feet. 

 The size of the drops is comparable to that of rain-drops, and winds of 10 miles 

 an hour and much more during the early part of the monsoon are often 



1 Faulwetter, R. C. "Wmd-blowu Rain, a factor iu Disease Dissemination." Joani. Agric. 

 Res., X, pp. 639— 64S, 1917. 



