1918] MACCAUGHEY—HAWAIIAN ALGAE 53 
which often has sufficient leakage to stimulate extensive algal 
growths, either pendent from the under side of the flume or in the 
drip zone beneath it. Genera that are of frequent occurrence in 
the ditches and flumes are Gloeocapsa, A phanothece, Oscillatoria, 
Spirulina, Phormidium, Lyngbya, Nostoc, Anabaena, Cylindro- 
Spermum, Scytonema, Tolypothrix, Ulothrix, Stigeoclonium, Nitella; 
Chara, Zygnema, Spirogyra, etc. 
Caves 
There are many caves in the Hawaiian mountains. Some are of 
vast size, but the majority are relatively small. They occur at 
all elevations, from sea level to the highest summits, and are 
invariably due to volcanic activity in former times. Many con- 
tain pools of water; those at sea level frequently have salt or 
brackish water. The walls of the cave are usually moist, especially 
around the mouth, due to seepage from above. The conditions 
of continuous moisture and sufficient light, which prevail near 
the mouth of the cave, are favorable for the development of algae. 
Luxuriant growths, particularly of the Cyanophyceae, occur in 
these places. Representative species which inhabit these localities 
are Gloeocapsa quaternata, A phanothece Naegeli, Oscillatoria sancta, 
O. formosa, Spirulina major, Phormidium papyraceum, Nostoc spp., 
Anabaena variabilis, Scytonema varium, S. ocellatum, Fischerella 
ambigua, Characium minutum, Ulothrix minutula. 
Some typical Hawaiian caverns which support an abundant 
algal flora are those of Ha-ena, Kauai; Nu’u-anu, Manoa, and 
Maka-pu’u, Oahu; Kau-po region of Hale-a-ka-la, and Hana 
region, Maui; Hilo and Ka-u regions of Hawaii. Innumerable 
smaller caverns are scattered throughout the mountainous regions 
of all the islands. : 
Mountain streams 
The rainfall on the upper slopes (2500-6000 ft.) of the Hawaiian 
mountains is torrential. This has carved deep valleys, penetrating 
into the heart of the mountains, These valleys vary in length from 
a mile to 10-12 miles. In width they range from narrow, rock- 
walled, sunless gorges to great amphitheaters, several miles in 
diameter, and rimmed by tremendous precipices. In the floor of 
each valley is a narrow stream, rarely more than 12 ft. in width. 
