The Mountain-Floras of the Pacific Islands.
In the Hawaiian Islands there are at least 37 or 38 genera, making up about 19 or 20 per cent. of those belonging to this era, that may be designated mountain genera, nearly all of them being characterised as appertaining exclusively or in the main to temperate regions, or as frequenting mountain-tops in tropical latitudes. In Tahiti there are only 7 or 8 of such genera, about 4 per cent. of the total for the era. In Fiji, excluding the Conifers, there are only 4 or 5, or not 2 per cent. of the whole. In Samoa, which may be included in the Fijian area, there are 3, or about 2 per cent. of the total. These are results which we might have expected from the varying altitudes of these groups, as described in [Chapter XIX.]
Few things give more pleasure to the botanist than his recognition in some remote locality of plants long familiar to him in other regions. This will often be his lot on the mountain summits of Hawaii. If he has been a mountain-climber in many countries, he will there notice again the genera Artemisia, Geranium, Plantago, Ranunculus, Rubus, Sanicula, Vaccinium, and others that he has met perhaps either in the Rocky Mountains or in the Andes or in Equatorial Africa or in the Himalayas. If fresh from Chile he will find on these heights the familiar Gunnera and the Chilian Strawberry (Fragaria chilensis). If he has been in New Zealand and in the islands of the Southern Ocean he will find old friends in the genera Acæna and Coprosma. He may handle once again plants like Nertera depressa, that he gathered on Tristan da Cunha; and on the boggy summits of some of the mountains he will find the ubiquitous Sun-dew (Drosera longifolia).
Within the limited area occupied by the peaks of Tahiti he will find genera like Astelia and Coprosma that are at home in New Zealand or in Antarctic America, and may even find, as in the cases of Coriaria ruscifolia and Nertera depressa, the identical species that are at home in those distant regions. Even on the summit of Rarotonga he will gather a species of Vaccinium. In Fiji, here and there on some isolated mountain-top he may come upon a remnant of this Antarctic flora, such as a solitary species of Coprosma or Lagenophora, that will carry him back for a moment to high southern latitudes; and in the highlands of Savaii, in the neighbouring Samoan Group, he will find again Nertera depressa and a species of Vaccinium. But that which will interest him most in Fiji will be the tall conifers of the genera Dammara, Podocarpus, and Dacrydium, which will bring to him memories perhaps of New Zealand and southern Chile, of South Africa, and of the mountain-woods of Java and of Southern Japan.
Yet the influence of isolation has been at work amongst the mountain-plants of all these groups. The agencies that have dispersed over the tropical Pacific plants from the cold latitudes of the southern hemisphere, and those that have borne the seeds of Plantago, Sanicula, and Vaccinium from mountain-top to mountain-top, even though it be to a peak in mid-ocean, are to a great extent inactive now.