fungi of timber trees in the valley is Forties fastuosus. It was never 
found on any host except those belonging to the Lauracese and 
Rubiacea?. Polystictus iodinus, causing a serious disease of steins, 
was found only on species of Rubiacese. Serious leaf blights were 
confined to Moracere and Urticaceae. Examples could be multiplied. 
It is not believed that these diseases and several others found on 
forest trees will attack Hevea. This condition should be of signifi- 
cance in establishing plantations in the jungle. 
REGIONAL PECULIARITIES 
Different forest and soil formations bring about reactions of 
various kinds in the general habitat, so that regional peculiarities as 
regards the presence of disease are often apparent. This was ob- 
served in the case of Hevea. On the flood lands of the lower Amazon 
the trees in some localities showed a high percentage of infection 
both in the forest and in small plantations, but in a region at another 
altitude, having different forest and soil conditions, they were en- 
tirely free from their principal fungous enemies. Why the species 
may be fairly free from fungous attack in one region and show 
severe infection in another is difficult to explain. Its possible adapta- 
tion to particular soil conditions or climatic influences may furnish a 
profitable basis for future experimental work. The health of forests 
is usually very intimately correlated with the topography of the 
region. The formation of a forest and the successive stages of its 
development are found to be wry definitely influenced by the physio- 
graphic evolution of the region. With the advance of Hevea from 
the highlands to the recently formed lowlands, it is by no means 
impossible of conception that the species has reacted in a way to 
make it more susceptible to disease, entirely apart from any imme- 
diate influence of the soil and water relation. 
Aside from this broader conception, it is by no means fanciful 
to consider the possibility of bringing about a certain degree of 
natural immunity in planted Hevea. This would be done by a care- 
ful manipulation of nursery sites and of seedlings, by the selection 
of seeds or cuttings from trees showing a high state of health and 
vigor and growing in localities free from disease, and by a careful 
selection of planting areas. It would be the function of the planta- 
tion manager, aided by the plant pathologist and soil expert, to 
seek out these areas. 
INTERCROPS 
It is safe to assume that forest trees of the same species, having 
the same physiological and morphological organization and grow- 
ing on the same site, require to a very large extent the same kind 
of food from the soil. The significance of this in relation to disease 
in plantations must be recognized by the planter. Uniform crowns, 
similar branching and natural pruning which cause wounds at the 
same level, equal depth and extent of root systems, equal annual 
increment, constant temperature, and uniform moisture and light 
relations, with few unfavorable influences, produce conditions that 
tend to increase or maintain fungous activity unequaled in planta- 
tions of mixed species. The truth of the proposition that fungous 
diseases spread more rapidly and cause greater damage in stands 
