14 FOKESTS OF THE HAWAIIAI^ ISLANDS. 



islands, and because of its character and of the fact that it covers dis- 

 tricts where the rainfall is greatest and the mountains most precipi- 

 tous, it forms the most valuable protective forest. ^' early all the dis- 

 tricts which accumulate a large supply of water available for irrig-ation 

 and liuming purposes are covered by lehua forests. 



Besides growing in mixture ^vith lehua, koa {Acacia koa) forms pure 

 stands over extensive tracts in Hawaii and Maui. Koa has a leaf 

 which is almost indistinguishable from the Australian blackwood 

 {Acacia melanoxyhw), which has been commonly planted in southern 

 California and to which it is closely related botanically. It is natu- 

 rally a spreading tree with a "short trunk, growing in somewhat scat- 

 tered stands. Occasionally under normal conditions it reaches a 

 diameter of 6 or 8 feet and a height of 75 feet. Much greater height 

 than this is reported. (See PI. Hi.) 



In crowded stands the koa is forced into a long, slender, but seldom 

 straight stem. It is intolerant of shade at all ages, and will not 

 germinate or grow without a large amount of light. Koa also has the 

 fern undergrowth which characterizes the lehua, though as it grows 

 in somewhat drier situations its undergrowth is usually not so luxuri- 

 ant. The ie-ie A'ine especially is seldom seen in a koa forest. 



Koa is the one fairly abundant tree of the Hawaiian forests which 

 is valuable because of its lumber. It is a highly prized cabinet wood, 

 which has been largely used on the islands and has also been expoiled 

 in limited quantities. Its color varies through many rich shades of 

 red and brown; its grain is line and indistinct. Curly koa is espe- 

 cially prized, but is very rare. Most of the best koa on Maui has been 

 cut, but an extensive mature forest exists in Hilo and Puna at eleva- 

 tions of from 4,r)()0 to 6,0m0 feet. This forest is but little known, but 

 seems to contain some magnificent timber and to be in a good state of 

 reproduction. Practically all of this forest is upon accessible govern- 

 ment land, and could l)e utilized to great advantage should the gov- 

 ernment build a road to it and establish a sawmill for working up the 

 matui-e trees. 



MA3IAXE. 



Mamane {Sojpliora chrysophylla) grows successfully only on the high 

 slopes of Mauna Kea and Hualalai. It originally extended down to an 

 elevation of about ^,000 feet on the north slope of Mauna Kea, but was 

 killed out at this elevation apparently by the encroachment of Bermuda 

 grass (manieie). But little of it is now found except between 6.000 and 

 8,000 feet, at which elevation it forms a belt clear around Mauna Kea. 

 In this situation it is notable for its rapid extension within the last 

 few years l)uth up and down the mountain. This extension has taken 



