FLORAL ASPECTS OF THE HAWAIIAN ISLANDS. 



By a. S. Hitchcock. 



[With 25 plates. J 



The flora of the Hawaiian (Sandwich) Islands is of unusual inter- 

 est because the group is the most isolated upon the globe. Disregard- 

 ing mere reefs or islets, the distances to land in the various directions 

 are: Unalaska, 2,016 miles; San Francisco, 2,100 miles; Samoa, 2,263 

 miles; Yokohama, 3,415 miles. Because of this isolation the native 

 flora is peculiar and the endemic element is proportionately large. 



During the summer of 1916 the writer visited the Hawaiian Islands 

 for the purpose of studj-ing their flora. In these investigations he 

 was assisted by his son, A. E. Hitchcock. Collections were made on 

 the six larger islands of the group ; that is, on all except Niihau and 

 Kahoolawe. Brief accounts of this trip have been given elsewhere.^ 

 In the present article an attempt will be made to give a general view 

 of the more prominent features of the flora ajid to record the impres- 

 sions that appeal to a botanical traveler. 



The climate is strictly tropical but, because of the proximity of the 

 ocean and because of the moderating influence of the trade wind, the 

 temperatures are not unpleasantly high. The summer daily maxi- 

 mum is about 85° F, at Honolulu. At higher altitudes the cli- 

 mate is cooler and on the summits of the high mountains of the 

 island of Hawaii there is much snow, some of which persists through- 

 out the year. The rainfall varies greatly in different parts of the 

 same island. All the islands are mountainous and the mountains 

 intercept the trade winds, causing a heavy rainfall upon the wind- 

 ward side of the islands. The lee side is dry or even arid in places. 

 In the vicinity of Honolulu, which lies on the westerly side of the 

 island of Oahu, the rainfall at the water front may be as low as 

 15 inches, but increases rapidly toward the mountains to the east, 

 at the crest of which, about 6 miles away, the rainfall may be as 

 high as 300 inches. In general the rainy season is from November 

 to March, but in the vicinity of the mountains the rains extend 



1 Explorations and Field-work of the Smithsonian Institution in 1916 (Smiths. Misc. 

 Coll. Vol. 66, no. 17, p. 59, 1917). A botanical trip to the Hawaiian Islands (Sci. 

 Monthly, vol. 5, p. 323, and p. 419, 1917). 



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