490 MacCAuGHEY: THE STRAND FLORA 
, 
of plant societies,’ acting in two ways—either by undermining 
plant individuals and groups, or by burying them with dune sand. 
Neither of these processes is particularly conspicuous along Ha- 
waiian coasts; the vegetation is not sufficiently luxuriant to em- 
phasize the former, nor are the dunes of sufficient size or mobility 
to give much importance to the latter. Here and there, however, 
both of these processes may be witnessed. 
On the whole, the Hawaiian beach winds are retarding rather 
than destructive agencies. The Hawaiian strands may be divided 
into the following classes, based upon the relative exposure to wind 
action: 
1. Shores exposed to prevailing winds.—The windward strands 
are much more exposed than are those along the leeward sides of 
the islands. Excellent contrasts are: the Hamakua and South 
Kona shores of Hawaii; the northeast and southwest shores of 
Haleakala; the north and south coasts of East Molokai; the Koo- 
lau and Waianae shores of Oahu; the Kilauea and Kekaha shores 
of Kauai. 
2. High or promontory-like shores.—These are more exposed 
than are low flat shores. Good examples are: Hamakua, Hawaii; 
Hana and Kaanapali, Maui; the great pali of Molokai; Makapuu 
and Kaena, Oahu; Napali, Kauai; and the cliffs of Nihoa. 
3. Shores devoid of surface irregularities or vegetation sufficient 
to break the force of the wind.—Low, flat shores, not protected by 
mountains behind them nor covered with forest, are exposed to 
the full force of the wind. In this class belong the coral atolls, 
and such shores as Kahuku and Mokapu, Oahu, the western ex- 
tremity of Molokai, the Maui isthmus, and the extreme south 
point of Hawaii. 
TRANSPIRATION 
This is unquestionably the most important single physiological 
factor in determining the character of the Hawaiian strand flora. 
Only those plants which possess comparatively low transpiratory 
rates are able to permanently establish themselves upon the strand. 
Those species which invade the strand from the interior, and are 
characteristically mesophytic, undergo marked structural changes 
when they appear as members of the strand association. 
