So uniform is the foliage that the untrained observer might easily be excused for supposing that the forest was mostly composed of species of laurel. The similarity and sombre colouring of the majority of the leaves are mainly responsible for the monotonous appearance of the forest. While most of the woody species appear similar, there are a few members of the rainforest flora which are very different from the normal type in appearance, notably the palms and the species of Dracaena and Pandanus. However, such bizarre and unfamiliar- looking plants are far less conspicuous in typical rainforest than many descriptions would suggest. There is great variation in the height of the trees, and rainforest is commonly several-layered in structure.
Some scientists divide the forest into many more layers.
There is thus, in Humboldt' s often- quoted phrase, ' a forest above a forest '. The undergrowth of the rainforest consists of shrubs, herbaceous plants and vast numbers of sapling and seedling trees. Travel books often give a misleading impression of the density of tropical forests. On river banks, or in clearings, where much light reaches the ground, there is a dense growth which is indeed often quite impenetrable, but in the interior of old undisturbed forest, if one's hands are free to bend back a twig here and there, it is not difficult to walk in any direction, though sometimes a detour has to be made to avoid a fallen log or a mass of lianes which have slithered down from above. When in the forest it is usual to carry a cutlass or parang, but more in order to mark a path to return by if necessary than to hack one's way.