186 CARNEGIE INSTITUTION OF WASHINGTON. 



The valley formations consist of shallower gullies or the deeper river 

 valleys, or, in short, of gullies and valleys. The gullies occurring at middle 

 or higher elevations often show no difference from the ridge slopes when 

 shallower and drier, but when deeper and moist are occupied by a scanty 

 or even a most abundant growth of trees, usually with the candle-nut (Aleu- 

 rites moluccana) dominant above, or with the Polynesian chestnut (Inocarpus 

 edulis) mixed with the candle-nut. 



The valley formations vary according to the slope and composition of their 

 sides. The lower valleys often show Inocarpus, Aleurites, Cerbera, etc., mixed 

 with ferns and epiphytes. Farther up may be found mara (Neonauclea forster- 

 iana), and in the upper reaches of moist cliff or talus slopes with fair quantity 

 of soil, pu'a (Fagrcea berteriana) , Homalanthus, Laportea, Nothopanax, fehi in 

 associations of its own, and special floras for each particular valley. The 

 general indicators for such an indigenous valley flora are the tree-ferns 

 (Cyathea sp. and Angiopteris evecta). These descend almost to sea-level in 

 moist valleys and wet exposures on the northeast and southeast coasts, but 

 do not descend below 1,000 to 1,500 feet on the drier coasts, e. g., in the Pare 

 and Punaauia districts. Much of the peculiar flora of Tahiti is to be found 

 on the cliffs and upper talus slopes of the valleys of this belt. 



The higher slopes and summits are also diversified, but particularly into the 

 dry exposed slopes and the drier or moister cliffs. On the exposed dry slopes 

 the fern association (Dicranopteris) gives way to low thickets of Lycopodium 

 cernuum and its associates. On the uppermost valleys and on moist cliffs 

 are found many of the most characteristic endemic species, such as arboreal 

 Compositse and Lobelioidese, although some of these descend much lower. 



In making a reconnaisance of the flora of Tahiti, one thing becomes early 

 evident, and that is the tremendous changes that have taken place since the 

 island was discovered, and particularly in recent years. A brief visit to 

 Moorea, where fewer changes have occurred, made this even more apparent. 

 These changes are most noticeable on the coastal plain, but even in the lower 

 slope belt much has been done and the work of driving out and upward the 

 indigenous species is still actively going on. The birds have suffered severely 

 also, and many or most of the original species are all but extinct. Species of 

 plants of tropical origin introduced either into cultivation or as weeds thrive 

 amazingly under Tahitian conditions and soon escape or spread and occupy 

 large areas, to the exclusion of other plants, especially of indigenous species. 



The weeds of wayside and field grow in astonishing profusion and are only 

 slightly held in check, even with great effort. The ornamentals spread far 

 beyond the places of cultivation. There are three species which have affected 

 the flora of the slopes materially, and these are the lantana, the guava, and 

 the yellow trumpet-flower (Tecoma stans). This last has, through its buoyant 

 winged seeds being carried by the upward currents of air, invaded even the 

 highest slopes. 



Another series of changes has come about through the using up of trees 

 available for purposes of fuel and construction. The tou (Cordia subcordata), 

 the tia nina (Hernandia peltata), and the atae (Erythrina indica) have all but 

 disappeared and canoe trees like the mara {Neonauclea forsteriana) are becom- 

 ing scarcer lower down. Even the fehi, once so abundant and plucked with 

 care, must be sought in more and more inaccessible places, especially since 



