258 



OUTLINE OF PLANT GEOGRAPHY 



desma (Rutaceae), Gouldia (Rubiaceae), Raillardia (Compositae), 

 Cyanea (Lobeliaceae). The latter family is especially interesting 

 from the standpoint of evolution. It is developed to a remark- 

 able degree in the Archipelago, the greatest number of species, 

 as well as the most specialized ones, occurring in Kauai, the 

 oldest island — the number of species being much less in the 

 more recently isolated islands, Maui and Hawaii, although these 

 islands are very much larger than Kauai. 







Fig. 73. — Gunnera petaloidea, characteristic of the wet mountain forests of Hawaii. 

 Note the man at right of center. Photo., Dr. J. F. Rock. 



There is but a single native genus of palms, Pritchardia, while 

 there are no gymnosperms; and some wide-spread tropical genera, 

 especially Ficus, are also entirely absent. The cosmopolitan family 

 Araceae has no certainly indigenous representatives, although 

 the staple food-plant of the natives, the "taro" (Colocasia anti- 

 quorum), is an aroid. Orchids, so abundant in most tropical 

 countries, have only three species. One of the most conspicuous 

 denizens of the upper wettest rain-forest is Gunnera petaloidea, 

 with great rhubarb-like leaves four to five feet across. This much 

 resembles the species from Chile. 



