1918] MACCAUGHEY—HAWAIIAN ALGAE 51 
algae are able to live even if they receive only intermittent spray 
wash. In this coralline zone are many of the calcareous hydrozoa. 
TIDAL POOLS 
Along the rocky coasts, where there are extensive shelves or 
ledges of lava or uplifted coral limestone, tidal pools are of common 
occurrence. The pools that lie nearest the water line are filled at 
every tide; indeed, many lose their identity as pools at each tide. 
Those at higher levels, and farther from the water line, may be 
filled only at times of very heavy surf, and dry up for considerable 
intervals. These variable conditions greatly affect the alga flora. 
The pools vary in size from mere puddles to large basins 10-20 m. 
long and 3-5 m. in depth. These large perennial basins support 
an alga flora very similar to that of the shallow lagoon waters. 
Excellent examples of tidal pools occur along the southern coast 
of Kauai, the Maka-pu’u region of Oahu, the north coast of Molokai 
and Maui, and along the Kona coast of Hawaii. Some of the 
algae common in the ordinary tidal pools are species of Lim- 
nothamnion, Wrangelia, Liagora, Padina, Ectocarpus, Sphacelaria, 
Halimeda, Caulerpa, Cladaphora, Chaetomorpha, Enteromorpha, 
Monostroma, Calothrix, Scytonema, Hormothamnion, Hydrocoleus, 
Lyngbya, Phormidium, Oscillatoria, etc. 
CORAL REEFS ON OTHER ISLANDS 
Special mention has been made of the reefs of Kauai and Oahu. 
The islands of Molokai, Maui, Lanai, and Ka-hoo-lawe all possess 
Some coral reefs, but nowhere is the development of the alga flora 
as great as upon Oahu. The island of Molokai, both windward and 
leeward sides, ranks first among the 4 islands enumerated. The 
island of Hawaii, with an area larger than the combined area of 
all the other islands, is the poorest in marine algae. In fresh water 
species, however, it takes precedence over several of the smaller 
islands. The coasts of Hawaii are rugged and precipitous, and the 
deep offshore waters are not favorable for algae. 
Taro loi and rice fields 
Turning now to the habitats of the fresh water flora, we consider 
first the taro loi. The Hawaiians and Chinese raise the taro plant 
