296 
At the end of 1908 the Heveas in the nursery of the Botanic Gar- 
dens of Surinam were attacked by a leaf-disease. The leaves took spots 
which spread over them in concentric circles. The disease is caused 
by a fungus Jiving at the under side of the leaves. Only young leaves 
are attacked. Though the disease is a very infectious one, trees, in 
favourable circumstances are probably little susceptible to it. The fast 
spreading in the above mentioned case must be ascribed to various 
accidental cn-cumstances especially to too close planting.” A figure 
of infected leaves and the mycelium is given. Fruit does not seem 
to have been obtained. 
The ordinary treatment for leaf fungus, either spraying with 
weak solution of bordeaux mixture or powdering with flowers of 
sulphur, would probably check this fungus. But prevention is better 
than cure and as Mr. Van Hall remarks in the paper, too close plant- 
ing is the main cause of an outbreak of this and other leaf fungi in 
he nursery and this can and should be avoided. Make the nurseries 
big enough and do not have each block too large. Watch for fungi 
and presence of mites and destroy the fallen leaves which arc or may 
be affected and become sources of further infection. 
MITES. 
It is not uncommon to find in the nursery beds that many of the 
leaves of the seedlings are irregularly twisted, bent to one side or 
otherwise deformed; frequently one side of a leaflet is much smaller 
than the other, and the leaflet is curved to one side. On examining 
the underside of the leaf, it is noticeable that the tissue between the “ 
nerves is swollen and the finer reticulations cannot be seen, the main 
nerves standing out green on a greyish back-ground. With this ap- 
pearance is associated a number of mites (acari) which live on the 
underside of the leaves. The young ones are very minute white, and 
elliptic and very slow in motion, the adult is larger semi-transparent 
with three brownish marks in the back. They do not appear to be 
veiy abundant in a leaf, certainly in proportion to the alteration they 
cause in it. The injury caused by these mites was first pointed out 
by Mr. Arden in his report published in 1902. 
1 he damage seems to be practical Jy confined to seedlings or 
at least young plants, especially such as are weakly owing to bad soil 
or excessive wind exposure. On well grown adult trees one rarelv if 
ever sees any injury caused or sees the presence of the mite. 
Overcrowding in the nursery bed, a very common error, is responsible 
lor a good deal of injury to the seedlings from mites and also from 
leaf disease. 
Frequently one sees the lowest three or four leaves attacked, and 
spoilt, and no damage done to the next output of leaves, the mites 
apparently disappearing. The number of mites visible is never very 
large, but the irritation they cause to the leaf is considerable. The 
