Economic Woods of Hawaii 697 



feet), have snow and ice, which occtirs nowhere else in the archi- 

 pelago. The trade winds from the northeast blow almost con- 

 tinuously throughout the year, and create marked windward and 

 leeward regions, as the main axis of the islands lies athwart these 

 winds. The trade winds are heavily water-laden, and the pre- 

 cipitation resulting from their contact with the motmtains is 

 extremely large, in some regions amounting to 400-500 inches. 

 The native forest reaches its finest development in the rainy zone, 

 although there are some tall species that inhabit the barren lava- 

 flows and other zerophytic regions. 



The chief ecologic zones are as follows : 



1. Littoral, a. Humid Littoral; windward. 



b. Arid Littoral; leeward. 



2. Lowlands, up to 1,000-1500 feet. Htmiid and Arid Sections, 



depending upon relation of topography to trade 

 winds, and distance from interior mountains. 



3. The Forest Zone. a. The Lower Forest; 1,000-2.000 feet; 



Htmiid and Arid Sections. 



b. The Middle Forest; 1800-5,000 feet; 



variable, with Himiid and Arid Sec- 

 tions. 



c. The Upper Forest; 5,000-9,000 feet; 



restricted to the high mountains of 

 Maui and Hawaii. 



4. The Summit Regions, a. Summit Deserts; 9,000-14,000 feet; 



high moimtains of Maui and 



Hawaii. 



b. Summit Bogs ; peaks rising into the 



cloud belt ; 4,000-6,000 feet. 



The tree of first rank as a commercial asset in Hawaii is the 



ohia lehua, {Metrosideros polymorpha Gaud.). This is the most 



abundant tree in our forests , and forms the largest pure stands. It , 



and other closely related species, also occur in the island of the 



South Pacific. It grows at all elevations from sea-level up to 9,000 



feet, and in every ecologic habitat, from raw new arid lava, flows 



to the perpetually water-saturated summit bogs. The ohia 



is exceedingly variable in growth form and foliar characters, and 



the botanic status of its nimierous sub-species and varieties is still 



unsettled. Many of the South Sea forms that have been described 



as species are probably only varieties of polymorpha. This species 



