226 PHYTOPHTHORA MEADII n. sp. ON HEVEA BRASILlENSlS 



monsoon were in some way related : a species of Phylojphthora was found on 

 the infected parts, and subsequently was shown to be the causative factor. 

 Tlie abnormal second leaf-fall, fruit-rot, and bark-rot were found to be general 

 in the older estates which happened to be in the southern part of the area in 

 which Hevea is grown, and they had gradually appeared in estates in the more 

 northern })art of the area as the trees began to produce their fruits. 



Field characters. 



There are five well defined symptoms caused by the presence of 

 Phi/tophtJiora in Hevea hrasiliensis : wilting of the leaves, fruit-rot, leaf-fall, 

 bark-rot, and partial die-back of the branches. From about the middle 

 to the end of June, or, in other words, about a fortnight to three weeks 

 after the monsoon bursts, the fruits on infected trees begin to show dull ashy- 

 grey portions on their surfaces. The discoloured part is sUghtly wrinkled and 

 sunk a little below the surface level of the healthy part of the fruit. It fre- 

 quently appears at the proximal or stalk-end of the fruit, and gradually extends 

 downwards and laterally till the whole fruit is covered. Sometimes, however, 

 it appears first on the side of the fruit, or at its distal end. Several discoloured 

 spots may appear and run together. Drops of latex ooze out here and there 

 on the discoloured surface and gradually turn black. The outer covering of 

 the fruit becomes dark and sodden and infected by a soft-rot. It splits along 

 the sutures, exposing the hard endocarp within and remains attached to it. 

 The endocarp most frequently does not split. The seeds often have a pale 

 dirty yellow colour, or have the brown markings only faintly developed, and 

 may not occupy the whole of the loculus, while the endosperm within is rotten 

 and contracts to a thin parchment lying along the inner wall of the testa. The 

 decayed fruit hangs on the tree for a considerable time, then falls off leaving 

 the stalk attached to the branch, but it or the stalk alone may hang on the 

 tree even till the fruiting season of the next year. A few days after the dull ashy- 

 grey colour appears, especially during a break in the monsoon when there is little 

 or no rain for a day or two, the infected surface becomes covered with a thin 

 incrustation which is white when dry. This consists of mycelium of a P%- 

 tojjhthora with a most copious formation of sporangia. The number of rotten 

 fruits on a tree or on an estate varies greatly. In badly infected areas every 

 fruit on a tree may be rotten, and over considerable areas (hundreds of 

 acres) an exceedingly small percentage of fruits comes to maturity and ripens 

 properly, the rest being all attacked by the fruit-rot. On the other hand in 

 places with a lighter rainfall the fruits have not been nearly so badly 

 attacked. 



