32 



uniquely arborescent with tufts of leaves at the top of woody 

 stems several feet high. 



The islands are mostly mountainous. The mountains are 

 commonly steep and precipitous on the windward side but slope 

 more gradually to the leeward. On Kauai, Oahu and Molokai 

 they scarcely reach 6000 feet in height. The extinct crater of 

 Haleakala on the island of Maui and the peaks of Mauna Loa 

 and Mauna Kea on Hawaii, however, are more than 10,000 feet 

 high. The moisture-laden clouds are caught by peaks 4000 to 

 6000 feet high with a resulting abundant precipitation. Above 

 these levels the amount of rainfall diminishes and is compara- 

 tively small above 10,000 feet. 



The great differences in altitude and in moisture have pro- 

 duced vegetation zones that are, in the main, well marked. The 

 zones are not constant as to altitude or extent on the different 

 islands. They may also vary on the different sides of the same 

 island with the forest zones usually extending to lower levels 

 on the windward than on the leeward side. In general, however, 

 five principal zones of vegetation are to be recognized : 



1 — Littoral zone, including sand beach and swampy areas 

 along the coast. 



2 — Lowland zone, open grazing and cultivated areas mostly 

 below 1000 feet altitude. 



3 — Lower forest zone with upper limits of 2000 to 3000 feet 

 altitude. 



4 — Middle forest zone with upper limits of 5000 to 6000 feet 

 altitude. 



5 — Upper forest zone found only on the higher mountains 

 and extending to 8000 or 10,000 feet altitude. 



The coast is quite variable in character. In some places it is 

 rocky while in others it is sandy Math accompanying small sand 

 dunes or it may be a mud flat. Typical genera of this coastal 

 zone are: Pandanus, Cenchrus, Panicum, Scirpus, Cocos, Batis, 

 Sesuvium, Capparis, Prosopis, Tephrosia, Tribulus, Gossypium, 

 Hibiscus, Sida, Waltheria, Calophyllum, Rhizophora, Termi- 

 nalia, Cuscuta, Cordia, Heliotropium, Vitex, Scaevola, and 

 Pluchea. 



The lowland zone extends from the littoral zone to the lower 

 limits of the forest but generally not exceeding 1000 feet altitude 

 although the upper limits vary greatly on the different sides of 



