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.

The Mountain-Flora of Hawaii as illustrated by the Non-endemic Genera.

Let us look in the first place at Hawaii, where the breaking off of communication with the outside world is especially pronounced. Here, all the species of two-thirds or more of the mountain-genera are confined to that group. Only in a relatively small number of cases are the species in touch with the regions outside. The mystery of disconnection that is so evident in the instance of the peculiar or endemic mountain-genera of the Compositæ and Lobeliaceæ and other orders is here again presented to us, and once more in the upland regions 4,000 to 10,000 feet above the sea. We will now endeavour to discover from an examination of the present distribution of the isolated mountain-genera (those non-endemic genera possessing only peculiar species) along what tracks they arrived at the Hawaiian uplands, tracks, as indicated by the local distribution of the species, that have been more or less abandoned since.

The Mountain Genera with only Endemic Species.—By referring to the Table on the following page it will be observed that nearly a third of these mountain genera have now their principal homes in the high latitudes of the southern hemisphere. They are components of what Forster and Hooker have termed the “Antarctic” flora, a collection of plants that range round the globe in high southern latitudes, namely, over Fuegia, New Zealand, southern Australia, South Africa, and the islands of the Southern Ocean, the “Antarctic” islands, as they have been termed. These genera are Acæna, Gunnera, Coprosma, Lagenophora, Astelia, Oreobolus, and Uncinia. (It is necessary to observe that I am entirely indebted to the Introduction to the Botany of the “Challenger” Expedition for my information on the “Antarctic” flora.)

We are thus led to expect that some of the other mountain genera may have been similarly derived from cool southern latitudes, even though they may be scarcely included in the “Antarctic” flora. This is very probably true of Myoporum and Exocarpus, two genera that are chiefly centred in Australia. A species of Sophora (S. tetraptera) is now one of the most widely dispersed of the plants of high southern latitudes, a circumstance which at all events explains the capacity for transport that the ancestor of the Hawaiian “Mamani” (S. chrysophylla) must have originally possessed (see [Chapter XV.]). Kinship between the Hawaiian species and southern forms has been found in the case of a few of the widely ranging genera here represented. Thus Decaisne placed Plantago princeps next to P. fernandeziana of Juan Fernandez; whilst according to Hillebrand, Plantago pachyphylla resembles P. aucklandica from the Auckland Islands. These resemblances are consistently associated with the respective range in altitude of the Hawaiian plants, since Plantago princeps occurs usually between 2,000 and 4,000 feet, and P. pachyphylla between 6,000 and 8,000 feet, the species of greatest elevation being related with the species of highest latitude. It is thus seen that these endemic mountain genera with peculiar species have very evident affinities with the plants of extra-tropical southern latitudes, and especially with the “Antarctic” flora. This affinity will also be found, as will subsequently be noticed, in the case of genera like Cyathodes and Nertera, where there is still a specific connection with the outside world.

THE MOUNTAIN-FLORA OF HAWAII, AS REPRESENTED BY THE NON-ENDEMIC

GENERA (Compiled from Hillebrand’s Flora).

GenusUsual altitude of station in feet.Distribution outside Polynesia.Distribution in Hawaii, Fiji, and Tahiti.Fruit.
Both Worlds.Old World.New World.Antarctic flora.Australia and New ZealandHawaii only.Hawaii, Fiji.Hawaii, Tahiti.All three groups.
With all Species Endemic.
Ranunculus (2)6,000- 7,000+............+.........Achene.
Viola (5)2,000- 6,000+............+.........Capsule.
Silene (4)2,000- 9,000+............+.........Capsule.
Geranium (6)5,000-10,000+............+.........Carpels.
Vicia (1)7,000- 8,000+............+.........Pod.
Sophora (1)5,000-10,000+.....................+Pod.
Rubus (3)4,000- 7,000+...............+......Berry.
Acæna (1)5,000- 6,000.........+...+.........Spinose achene.
Gunnera (1)3,000- 6,000.........+...+.........Drupe.
Sanicula (1)6,000- 8,000......+......+.........Prickly carpel.
Coprosma (9)3,000- 9,000............+.........+Drupe.
Lagenophora (1)6,000-.........+......+......Viscid achene.
Artemisia (2)4,000- 8,000+............+.........Achene.
Lobelia (5)2,000- 6,000+............+.........Capsule.
Vaccinium (2)3,000- 8,000+.....................+
Samoa		Berry.
Myoporum (1)Coast to 10,000............++.........Drupe.
Plantago (2)2,000- 8,000+............+.........Capsule.
Exocarpus (2)3,000- 6,000............++.........Fleshy nut.
Sisyrinchium (1)4,000- 7,000......+......+.........Capsule.
Astelia (2)2,000- 6,000.........+............+Berry.
Oreobolus (1)6,000.........+...+.........Toothed nutlet.
Uncinia (1)3,000- 5,000.........+...+.........Awned nutlet.
Agrostis (3)4,000- 6,000+............+.........Awned grain.
Deschampsia (3)3,000- 6,000+............+.........Awned grain.
Trisetum (1)3,000- 5,000+............+.........Awned grain.
Poa (2) +............+.........Grain.
With Endemic and Non-endemic Species.
Cyathodes (2)2,000-10,000............+......+...Drupe.
Lysimachia (6)Coast to 6,000+............+.........Capsule.
Chenopodium (2)Up to 7,000+............+.........Seed-like.
Santalum (3)Coast to 10,000...+..................+Drupe.
Carex (5)2,000- 7,000+...............+......Nutlet.
Rhynchospora (4)Up to 10,000+.....................+Nutlet.
Panicum (14)Coast to 6,000+.....................+Grain.
Deyeuxia (3)Up to 10,000+............+.........Awned grain.
With no Endemic Species.
Fragaria chilensis4,000- 6,000......+......+.........Fleshy.
Drosera longifolia4,000+............+.........Capsule.
Nertera depressa2,500- 5,000.........+............+Drupe.
Luzula campestris3,000-10,000+..................+...Capsule.
GenusUsual altitude of station in feet.Distribution outside Polynesia.
Both Worlds.Old World.New World.Antarctic flora.Australia and New Zealand
With all Species Endemic.
Ranunculus (2)6,000- 7,000+............
Viola (5)2,000- 6,000+............
Silene (4)2,000- 9,000+............
Geranium (6)5,000-10,000+............
Vicia (1)7,000- 8,000+............
Sophora (1)5,000-10,000+............
Rubus (3)4,000- 7,000+............
Acæna (1)5,000- 6,000.........+...
Gunnera (1)3,000- 6,000.........+...
Sanicula (1)6,000- 8,000......+......
Coprosma (9)3,000- 9,000............+
Lagenophora (1)6,000-.........+...
Artemisia (2)4,000- 8,000+............
Lobelia (5)2,000- 6,000+............
Vaccinium (2)3,000- 8,000+............
Myoporum (1)Coast to 10,000............+
Plantago (2)2,000- 8,000+............
Exocarpus (2)3,000- 6,000............+
Sisyrinchium (1)4,000- 7,000......+......
Astelia (2)2,000- 6,000.........+...
Oreobolus (1)6,000.........+...
Uncinia (1)3,000- 5,000.........+...
Agrostis (3)4,000- 6,000+............
Deschampsia (3)3,000- 6,000+............
Trisetum (1)3,000- 5,000+............
Poa (2) +............
With Endemic and Non-endemic Species.
Cyathodes (2)2,000-10,000............+
Lysimachia (6)Coast to 6,000+............
Chenopodium (2)Up to 7,000+............
Santalum (3)Coast to 10,000...+.........
Carex (5)2,000- 7,000+............
Rhynchospora (4)Up to 10,000+............
Panicum (14)Coast to 6,000+............
Deyeuxia (3)Up to 10,000+............
With no Endemic Species.
Fragaria chilensis4,000- 6,000......+......
Drosera longifolia4,000+............
Nertera depressa2,500- 5,000.........+...
Luzula campestris3,000-10,000+............
GenusDistribution in Hawaii, Fiji, and Tahiti.Fruit.
Hawaii only.Hawaii, Fiji.Hawaii, Tahiti.All three groups.
With all Species Endemic.
Ranunculus (2)+.........Achene.
Viola (5)+.........Capsule.
Silene (4)+.........Capsule.
Geranium (6)+.........Carpels.
Vicia (1)+.........Pod.
Sophora (1).........+Pod.
Rubus (3)...+......Berry.
Acæna (1)+.........Spinose achene.
Gunnera (1)+.........Drupe.
Sanicula (1)+.........Prickly carpel.
Coprosma (9).........+Drupe.
Lagenophora (1)...+......Viscid achene.
Artemisia (2)+.........Achene.
Lobelia (5)+.........Capsule.
Vaccinium (2).........+
Samoa		Berry.
Myoporum (1)+.........Drupe.
Plantago (2)+.........Capsule.
Exocarpus (2)+.........Fleshy nut.
Sisyrinchium (1)+.........Capsule.
Astelia (2).........+Berry.
Oreobolus (1)+.........Toothed nutlet.
Uncinia (1)+.........Awned nutlet.
Agrostis (3)+.........Awned grain.
Deschampsia (3)+.........Awned grain.
Trisetum (1)+.........Awned grain.
Poa (2)+.........Grain.
With Endemic and Non-endemic Species.
Cyathodes (2)......+...Drupe.
Lysimachia (6)+.........Capsule.
Chenopodium (2)+.........Seed-like.
Santalum (3).........+Drupe.
Carex (5)...+......Nutlet.
Rhynchospora (4).........+Nutlet.
Panicum (14).........+Grain.
Deyeuxia (3)+.........Awned grain.
With no Endemic Species.
Fragaria chilensis+.........Fleshy.
Drosera longifolia+.........Capsule.
Nertera depressa.........+Drupe.
Luzula campestris......+...Capsule.