RUBBER (HEVEA) DISEASES 77 
An especially interesting case of this kind was observed on the 
Rio Marmore. * In a low boglike area some Heveas had succeeded 
in establishing themselves in the white, soggy, poorly drained soil, 
very evidently underlain by a hard impenetrable layer. The trees 
showed a stag-headed condition. In some cases they were leaning 
or were blown over, and the taproots were found to be decayed. The 
nature of the decomposition of the taproots left little room for doubt 
that the sickly appearance and reduced vigor of the trees were di- 
rectly referable to the condition of the soil. It is not generally 
believed that an actual decomposition of wood results from a purely 
chemical action of the organic or inorganic acids of the soil, although 
this may be possible under very specific conditions of stagnation and 
insufficient aeration. The fermentative action of bacteria, together 
with the presence of higher fungi, made more active by the constant 
moisture conditions, no doubt was largely responsible for this type 
of root-rot. 
In wet soils underlain by an impervious stratum of hard clay 
Hevea may be expected to fall under the influence of wind when 
left unprotected. For this reason any scheme for thinning out the 
jungle on areas where Hevea is abundant should be based on a con- 
sideration of soil conditions. The hardpan does not admit of the 
penetration of the taproot to any depth, and it also retains the mois- 
ture comparatively near the surface. Under such conditions the 
surface roots of Hevea have been observed to spread great distances, 
scarcely buried beneath the surface soil. This may be interpreted as 
both a moisture and an oxygen relation. 
Petch has found that the roots of Hevea except in certain well- 
known cases will not live permanently under water. The early con- 
ception was that Hevea was a species of swampy soils. It is interest- 
ing to read the recommendations by Cross and others for planting the 
tree on wet soils in the East. This at first was practiced, but with 
disastrous results. Petch reports that when Hevea is grown in 
swampy soil, where the water table lies near the surface, the tap- 
root does not grow below the water level, or, if it does, it soon de- 
cays. In some cases such trees had to be propped up to keep them 
from falling over. This is exactly the condition noted in one or two 
places in the Amazon Valley. 
In a territory so vast as that of the Amazon drainage, where there 
is unlimited opportunity for selecting sites admirably suited for 
growing rubber, there should be no excuse for failure to recognize 
these facts. 
PREPARED RUBBER 
MOLDS 
The prepared rubber assembled at the stations along the rivers and 
awaiting shipment to Manaos or Para not infrequently develops 
various molds. Between the periods of collecting the latex the soft 
plastic balls of rubber that are in the making are placed in the sun 
to dry. The surface may become infected with the spores of these 
molds, which are inclosed in the ball when the next layer is applied. 
Consequently, when the balls are opened up for inspection or for 
more thorough drying in the warerooms at Manaos and Para, the 
