INTRODUCTION xxvii 



been very different from the present condition. Thus at the base of the cone of 

 Diamond Head on the coast a few miles S.E. of Honolulu are found extensive deposits 

 of many species of land Mollusca {Amastra, Leptacliatina, Endodonta, Succinea etc.), 

 the species differing little, if at all, from those now living in the forest-clad parts of 

 the Oahuan mountains. Similar deposits are found on the leeward side of the Waianae 

 range at no great elevation above the sea and in various other localities. Such places 

 are amongst the most arid to be found on the island at the present time. While 

 Succinea can be found living near the coast in the driest localities, most of the other 

 genera can thrive only where there is a liberal supply of dampness, and where the 

 vegetation is dense enough to retain this. It is very important to remember that such 

 different conditions have existed in past time, when one considers the possibility of the 

 survival and establishment of any chance immigrants that may have reached the shores. 

 Where the immigrant would now find a barren and arid region on its arrival, very 

 different conditions may have existed in other times. 



Above the lower dry mountain slopes, at elevations varying usually from 1200 — 

 3000 ft., one reaches the belt of continuous forest. Where undisturbed by man or 

 beast, this is often so dense as to be impenetrable without cutting a pathway, or at 

 least breaking through by force. Luxuriant growths of leie {Freycinetia) in many 

 localities and in others wiry-stemmed ferns [Gleichenid) make progress difficult. The 

 width of this forest-belt varies very gready according to the locality and according to 

 the destruction that has been the work of man. In some places no such forest-belt 

 exists, in others it has been reduced to an open timbered country, covered with foreign 

 grasses. This is the last stage preceding destruction, when the remaining trees produce 

 their seed in vain, for the thick growth of grass prevents any young trees springing up 

 to replace the old. We have known a forest so den.se that it could be traversed only 

 along a narrow made path, generally knee-deep in mud, to be reduced to open wood- 

 land by the ravages of cattle within a period of about fifteen years. 



On Oahu (and elsewhere) the lower part of this forest consists or in past time has 

 consisted to a large extent of the fine and valuable Acacia, A. koa, which altogether 

 fails or becomes sparing in the highest forests of this island. On some of the islands 

 (Molokai and Lanai) there is now no Acacia forest, though evidences of its former 

 existence still remain. On the lofty mountains of the other islands the Koa may 

 extend throughout the whole forest-belt, but it is wanting over extensive areas from 

 natural causes. The Ohia, Metrosiderus, is the commonest of all forest trees extending 

 both above and below the region of dense forest, and is the main constituent of the 

 forests throughout the whole group of islands. It is extraordinarily variable, and can 

 adapt itself to the most varied conditions of climate and station, to an extent indeed 

 of which the Koa seems quite incapable. From one of the largest of forest trees it 

 may become, on boggy mountain tops, a trailing shrub, or a small erect plant with 

 simple stem no thicker than a pencil and bearing a single large terminal flower. Its 



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