DERIVATION OF THE FLORA OF HAWAII 



The lowland zone varies much in different parts of the islands. 

 Many of the strand plants invade this zone, but many others are largely 

 confined to it. On the leeward side this is largely grass land, except 

 where it has been invaded by lava flows, but in some places it is so dry 

 that the bare lava is quite destitute of vegetation. This zone, especially 

 in Oahu, has been invaded by certain introduced plants, notably prickly 

 pear and "Algaroba" (Prosopis). The latter, a leguminous tree, forms 

 extensive groves and is of great importance both for the wood and for the 

 edible pods, which furnish valuable food for animals. 



Other introduced plants which have spread extensively .are the guava 

 and a species of Lantana (L. camara}, the latter being a very trouble- 

 some pest. On the windward side of the islands the forest may come 

 down to the sea. 



Beyond the more or less open lower zone of vegetation there is 

 found the lower forest region. On the windward side of the more lofty 

 islands, and in the moist valleys of the lower islands, this forest is very 

 dense, and composed of comparatively few trees. The predominant trees 

 are the Kukui (Aleurites), and Ohia (Eugenia), both species common 

 throughout Polynesia, and very probably introduced by the aboriginal 

 immigrants. The drier parts of this lower forest, according to Rock, are 

 very much richer in species of trees than the rain forest. 



The middle forest zone, extending from about 2,000 to 4,000 feet, 

 is extremely rich in species, and includes a great variety of interesting 

 shrubs and some herbaceous species as well. Probably the most conspic- 

 uous tree is the "Ohia lehua" (Metrosideros polymorpha), also a wide- 

 spread species of Polynesia. This mountain forest is the home of many 

 of the most peculiar of the endemic plants, such as the tree-lobelias, and 

 certain Rutaceae, e. g. Pelea. On the windward side of the islands this 

 is a typical rain forest, and there is a great development of ferns, mosses, 

 and liverworts. Here the tree ferns and the beautiful filmy ferns reach 

 their best development. 



BOGS 



On the summits of some of the older mountains there are bogs of 

 characteristic formation. These are particularly well developed on the 

 high plateau which constitutes the greater part of Kauai. Here, at an 

 elevation of 4,000 to 5,000 feet, there is a prodigious and almost incessant 

 precipitation, converting the whole region into a trackless swamp largely 

 covered with trees, but in places forming open bogs, covered with tus- 

 socks of grasses and sedges, among which grow a number of character- 

 istic species, largely of northern affinities. Among these bog plants are the 



