The last biological frontier? Advancements in research on forest canopies

Overhead, at a height, perhaps of a hundred feet, is an almost unbroken canopy of foliage formed by the meeting together of these great trees and their interlacing branches; and this canopy is usually so dense that but an indistinct glimmer of the sky is to be seen, and even the intense tropical sunlight only penetrates to the ground subdued and broken up into scattered fragments ... it is a world in which man seems an intruder, and where he feels overwhelmed ...