488 MacCauGHEY: THE STRAND FLORA 
cated by these figures is thus about 13,500, that is, the beach 
illumination is approximately 13,500 times as great as that of the 
cloudy rain-forest. Of course, these figures do not include all of 
the light-factors involved, but they are sufficient to indicate the 
great differences in the illumination of regions not far removed 
from one another. 
PRECIPITATION 
All precipitation on the Hawaiian littoral occurs in the form of 
rain, dew, and rarely hail; snow is unknown. The strand is char- 
acteristically xerophytic or semi-xerophytic, as contrasted with 
the mesophytic lowland areas, and the montane rain-forests. 
The following data from representative stations of the U. S. 
Weather Bureau, 1915, will show these differences, the amount of 
rainfall being given in inches: 
Island Littoral station gsr a pag A Be 6 
MRR See oN 16.98 38.02 75-52 
Oahu Bim Sieh aly Vee cers Oe eae 18.99 42.29 II4.22 
Maui (914) ee wh bie owes 4 20.91 42.70 397.26 
MAMAN slates ebay we ae a 8.41 39.10 159-60 
A few littoral stations are mesophytic or hygrophytic, but this is a 
relatively unusual condition—e. g., Na Pali coast of Kauai, north 
coast of East Molokai, and Hamakua coast of Hawaii. 
The relationship between the annual precipitation on the strand 
and the character of the vegetation is very close. The paucity of 
the Hawaiian arborescent strand flora is undoubtedly due in part 
to the xerophytic character of the littoral. In those few strand 
regions which do possess sufficient rainfall, the forest extends down 
to the beachline. The Puna, Hilo, and Hamakua regions, illus- 
trate this condition. Schimper (’03, p. 407) makes the generali- 
zation: 
On Hee £. 
ann te Aiat eine 
rainfall they are almost the only ones. The close wood! 
all? 
AUR ad Siidis 
In the case of the Hawaiian littoral vegetation, much emphasis 
must be laid upon the exterminating and limiting agencies which 
