264 



but more or less rounded. The spots are irregularly scattered over the 

 leaf, but usually more near the edge than elsewhere and they frequently 

 run into each other. 



The leaf is often attacked when just opened and before it has 

 attained its full green colouring. Indeed I am inclined to think that 

 the attack commonly commences in the bud. After a time the centre 

 of the spot becomes hard and black and the oil glands swollen and 

 protuberant. At length on the under, more rarely the upper, surface of 

 the leaf from the blackened spot can be seen with a lens fine white 

 hairs like a mildew. 



On examination with the microscope these are seen to be fine fila- 

 ments (Sporophores) bearing at the apex a number 3 to 9 short arms 

 all nearly equal. At the apex of each, at first abruptly decurved then 

 spreading, is a yellow sporangirum which doubtless produces one or more 

 spores which drifted about by the wind attack other parts of the plant. 



The life history of this plant has not yet been worked out but it 

 appears to be one of the Peronosporeae. In any case it is a most injuri- 

 ous pest, destroying the leaves as soon or before they emerge from the 

 bud stage. 



Indeed I have seen a tree of about 12 or 14 feet tall quite killed 

 by the attacks of this fungus. Every bud as it appeared was destroy- 

 ed, and when the terminal bud of a branch was gone and the lateral 

 buds extruded they were killed in like manner. 



It is I believe also this fungus which kills the seedlings in great 

 quantities by destroying the bud. 



Some trees in the Botanic Gardens were badly affected by this 

 fungus and the treatment of washing them with Bordeaux mixture was 

 tried with marked success. The mixture was syringed on to the trees 

 with a bamboo squirt till the foliage was very conspicuously blue. At 

 the next putting forth of leaves it was noticed that the young leaves 

 which came out were not attacked by the fungus while the trees that 

 were not syringed were as bad as before, the leaves being all spotted 

 with the fungus and many buds blackened and dead. 



The worst attacked trees are those on bad stiff yellow clay soil 

 exposed to full sun. 



A tree growing close under a large para rubber tree was but little 

 damaged though the fungus was present. This tree however appears 

 to be overshaded as though quite an old tree, it has as far as I have 

 known never flowered. The soil it grows in is better and richer than 

 that in which a tree about 50 yards away is growing and which is in a 

 bad state from the attacks of this fungus. There can be no doubt that 

 the best treatment for this pest is the destruction of its spores by the 

 aid of the Bordeaux mixture of copper sulphate and lime with which 

 the trees should be well sprayed. As the spores of the fungus are 

 chiefly produced on the lower side of the leaf, the tree should be spray- 

 ed from below upwards. Infected leaves on the ground should be 

 sprayed and swept away and burnt and the trees well manured. 



Seedlings which are often killed apparently by this fungus should 

 be carefully sprayed with a weak solution of the Bordeaux mixture and 

 should be grown at a distance from the infected trees. 



H. N. KlDLEY. 



