Ly INTRODUCTION. 
volcanic action commenced at the northwest extremity, thirty 
degrees of longitude northwest from the island of Kauai, and 
gradually moved on to the island of Hawaii, with subsidence 
of the older formations while it progressed. But the western 
extremity of this raised sea-bottom land is separated by a great 
distance and enormous depths of sounding from the nearest high 
land, Japan, and the circumstance that the present flora of the 
Hawaiian Islands has less affinity to that of Japan than to any 
other warm or temperate country on the borders of the Pacific 
Ocean forbids altogether the assumption that this submerged 
chain of islands can at any time have formed a road for the 
migration of plants. 
The soundings hitherto made between the Hawaiian Islands 
and California have given uniform depths of 3000 fathoms, and 
only a couple of degrees to the south commences one of the 
greatest depressions in the ocean, with depths of more than 3000 
fathoms, extending nearly to the next group of low islands — 
yra, Fanning, Christmas, Jarvis, and others — which trend 
in the direction of the Society group. The supposition of a 
terrestrial immigration of plants in former times finds no support 
in our actual knowledge. 
ot much better stands the case with regard to ocea 
currents. The Hawaiian group lies entirely within the domain 
of the Northeasterly Current of the Pacific, a direct continuation 
our islands and those of the Marshall and Caroline groups much 
farther on. As a review of the Hawaiian flora shows that the 
northwest coast of America, including California, has until quite 
recent times only contributed one or two inhabitants of the 
highest mountains, and has besides few so-called representative 
species, the influence of this current in supplying the islands 
could hardly come into account if it were not for a feeder which 
it receives on its southern boundary, while deflecting westward, | 
from the coast of Mexico and Central America, and perhaps 
from still farther south. This accessory stream may or may 
not account for the important American element of the Andine 
regions which is apparent in the Hawaiian flora. 
Of greater importance must have been the Equatorial Counter- 
Current. Originating north of the equator, in the neighborhood 
