304 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
growth at the top of the forest. In general, the activity of the mass 
of vegetation is greatest at the periphery, where there is access to 
light. It is here that the flowers are produced. One can usually 
obtain flowers from the overhanging branches of trees by collecting 
from a boat in the rivers and streams. One may pass through a 
forest and find scattered on the ground the corollas of flowers borne 
far above and out of sight. The collector can obtain specimens of 
these only by felling the trees, and he often obtains a rich harvest 
by accompanying workers taking out logs of commercial timber or 
making clearings or cutting roads or trails. 
The interior of the rain forest is a solemn place. In the brightest 
day the sunlight does not penetrate and there is a subdued. diffused 
light that seems to emphasize the silence. Ordinarily one can walk 
without much difficulty in any direction. Although there are many 
large trees in the forest they are scattered and the spaces between 
are filled with trees of varying smaller sizes. Woody vines or hanas 
are abundant, leafless. and flowerless as they twine or struggle up- 
wards, finally lost in the roof of the forest. Some lianas are deeply 
cut into the bark of the trees they entwine, others dangle unsupported. 
tor long distances, the original support having been destroyed. The 
trees of the first class—the giants—trise straight and strong, the shafts 
passing upward out of sight in the mass of branches and foliage. 
As viewed from the outside one sees here and there the tops of these 
giants rising far above the general level of the forest. Trees of a 
second class pass up to form the general mass of the forest roof. Be- 
tween them there is a third class whose tops expand below the tops 
of the others and must be satisfied with a less amount of light. 
Below these are other classes successively more spindling, arrested in 
their growth by the competition of their more powerful neighbors. 
Some of these maintain a precarious existence, others give up the 
struggle and die. Dead trees, branches, and twigs soon rot away 
or are ground to powder by the wood ants. For this reason one 
never sees the accumulation of dead logs that is found in northern 
forests. The floor of the forest is comparatively clean. The sub- 
dued light permits but a small amount of low vegetation. There 
are normally a few species that have become adapted to the condi- 
tions prevailing here. Such are certain broad-leaved species of 
Ichnanthus and a few aroids and gesneraceous shrubs. There is a 
tendency for the larger trees to produce buttressed roots, that is, 
the base of the trunk expands into thin supporting slabs that radiate 
in all directions, giving greater stability to the tree. The mora 
tree (Dimorphandra mora), a common tree in the interior forests, 
has such buttresses prominently formed and often extending far up 
the trunk. 
