The chief obstacles to travel and development in the valley are the broken or flooded nature of the country, the impenetrable forests, through which, except off the few trails, the traveller has to hack his way by means of the _machete_, wielded by his Indians. The heavy rains, the mosquitoes and the malaria, the unreliability of the natives. Dangers from wild beasts have been exaggerated. The worst of these is the mosquito! The forests are not teeming with beasts of prey, although they are to be met with. Often the traveller may pursue his way for vast distances without seeing any living creature, and he must not depend upon game for any particular addition to his larder, for there is little, in many regions. Food must be carried, and the matter of transport is one of the most serious obstacles. Without adequate supplies the traveller will starve, and leave his bones in the dismal forest, as has befallen many an adventurer here. Except by actual travel no adequate idea of the Amazon forests can be obtained: of their alternating gloom and splendour, of their superabundant vegetation, of the impenetrable ramparts of their dense foliage and matted trunks. The forest is the largest area of virgin woodlands on the face of the globe, extending back from the Atlantic seaboard to the slopes of the Andes for more than 2,500 miles, and ranging in breadth from 200 miles on the coast, at the mouth of the river or in Brazil to 900 miles between Venezuela and Bolivia. The marvellously rich flora is among the wonders of the world. The principal characteristic is in the variety of genera and species. A single acre of ground may contain hundreds of different species of tree and shrub, including palms, acacias, myrtles, mimosas and others. The forest is in this unlike the great coniferous or other forests, and the condition is not favourable in a commercial sense as regards the industry of timber-cutting, although industrial kinds of its trees afford the basis of profit. The trees are not always of great height here, the average being perhaps a hundred feet, with many kinds reaching two hundred feet, the shorter varieties being upon the flood-plains.