454 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



rather flat cones, the precipitous cliffs and valleys being due to ero- 

 sion, though there are high cliffs (palis) on the north and east sides 

 of some of the mountains, as the Kohalas and the mountains of Molo- 

 kai, and the walls of the groat craters. As one looks from the sea 

 on the northeast coast of Hawaii to the summit of Mauna Kea, a dis- 

 tance of perhaps 20 miles, the slope is so even that it is difficult to 

 convince one's self that he is looking up to a peak nearly 14,000 feet 

 above him. The famous volcano Kilauea lies on the southeast slope 

 of Mauna Loa at an altitude of about 4,000 feet. In one part of the 

 large crater, about 3 miles across and 500 feet deep, is the lava pit 

 called Halemaumau, a circular depression about 1,500 feet wide at 

 the top and several hundred feet deep. The view from the rim of 

 this pit is extremely fascinating, especially at night. The liquid 

 lava seems to boil from the force of the escaping gases and the waves 

 produce a loud roar as they splash against the margins. 



The distribution of the flora upon the islands depends upon rain- 

 fall, altitude, and soil. The rainfall is highest in the mountains and 

 decreases toward the leeward side of the islands. The annual precipi- 

 tation in the rain belt is usually from 100 to 300 inches, but in some 

 localities exceeds this large amount. On the southwestern sides of 

 the islands the rainfall becomes so slight that the climate is arid. 

 The rain zone extends up on the mountains to only 5,000 to 6,000 

 feet. Consequently, on the high peaks of Hawaii and East Maui the 

 rainfall decreases toward the summits. The character of the flora 

 changes with the rainfall. Hence, rain forests occupy the regions of 

 high rainfall, while the slopes of western Molokai, East Maui, and 

 Lanai and the plains of central Oahu and Hawaii are covered with 

 grasses and other herbaceous vegetation, with sometimes intermingled 

 areas of open, scrubby forest. The peaks of Mauna Kea and Mauna 

 Loa are nearly devoid of vegetation above 10,000 feet. 



The grasses of the Hawaiian Islands number about 100 species, 

 including the large number of introduced weeds. The native species 

 are less than half the total. As grasses are inliabitants of open 

 ground they are rare in the rain forests. A well-lmown, useful native 

 grass is the pili {Hetero'pogon contortiis) which is a valuable range 

 grass. This species was used by the early Hawaiian inhabitants to 

 thatch their cabins, the grasses being fastened to a light frame work 

 to form the walls and roof. An introduced species, Hilo grass {Pas- 

 -palum, conjugaturn) ^ has become a pest, having become established 

 almost to the exclusion of other plants over wide areas on the wet 

 slopes below the rain forest. It is said to have been introduced at 

 Hilo from tropical America about 1840. It is of little value for 

 pasture as stock will not eat it except when forced to from hunger. 

 Another common and equally useless species, Paspalnm, orhirulare^ 

 which seems to have received no common name, occurs widely dis- 



