INTRODUCTION. XV 
of the Molucca Islands, it runs in a nearly straight course south 
of the Caroline and Marshall Islands toward the Bay of Panama. 
Although separated ordinarily by a narrow strip of neutral water 
from the North Equatorial Current — the continuation of the 
North Pacific Drift running in a direction opposite to it — still there 
can be no doubt that during the long continued prevalence of 
southwesterly gales, which prevail in winter, it will be pushed 
farther north, so as to intermingle to the east of our longitude 
with the North Equatorial Current and thus deposit drift on 
the shores of the Hawaiian Islands. 
s may be inferred from this isolation the flora of the 
Hawaiian Islands is very peculiar, and contains a much larger 
proportion of endemic plants than that of any other country. 
The great elevation of the mountains contributes to bring about 
this result and to increase the variety of forms. A single day's 
march will carry the traveller from the tropical heat of the coast 
to the region of perpetual snow, and in crossing the breadth 
of an island he may pass from a climate with an annual average 
of 180 inches of rainfall to one of 30 inches or less. In contrast 
to this diversity in temperature, moisture, and barometric 
pressure stands the uniformity of soil, which is derived almost 
valleys and the adjacent flat coast, and on some of the tablelands 
of the oldest formation, where denudation has long been active, 
is the water retained. In the valleys a heavy retentive clay 
forms the surface and affords a suitable bed for the cultivation 
of taro and rice. On the high tablelands of Kauai and West 
Maui, and also in one or two parts of Molokai, a thick layer of 
mosses, liverworts, and sedges covers the moderately heavy soil; 
being within the reach of perpetual clouds and continually 
dripping with moisture it has increased to beds of turf, and 
forms extensive bogs, the habitation of many of the rarest plants. 
The present work describes 844* species of phanerogamic 
The figures given on this and the following pages are mainly my own, as it was 
found by a careful enumeration that the number of species described in the Flora did 
not quite accord with the author’s total nor with allot ts to the different subdivisi 
This, with other evidence in my possession, renders it almost certain that this portion at 
least of the Introduction was written some time before the completion of the Flora, and 
that the author subsequently altered his mind as to the validity of a few species and 
as to whether a plant had been introduced since the discovery of the Islands or was 
igi W. F. iH. 
