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.

It is evident that in one or two cases the connection between the representatives of the “Antarctic” genera on the Hawaiian uplands and those of high southern latitudes has only been recently broken off. Thus with reference to the Hawaiian species of the Cyperaceous genus, Uncinia, it may be observed that although Hillebrand regards it as a distinct species, Hemsley (Intr. Bot. Chall. Exped., p. 31) remarks that it is very near if not the same as a New Zealand species, an affinity very significant of the source of the mountain plants of this group that are derived from these southern latitudes.

The next component to be recognised in these Hawaiian mountain genera with peculiar species is a small special American element; and in this connection Sanicula and Sisyrinchium may be especially mentioned. The first is mainly North American, and particularly Californian; but there are two solitary species found on the continents and in oceanic islands such as the Azores. The continental species, Sanicula europæa, occurs not only in Europe and Central Asia, but in South Africa, and at high elevations on the mountains of Equatorial Africa and of Madagascar. It is not, however, with this widely ranging species that Sanicula sandwicensis is related, but with S. menziesii, a species from California and Oregon (Hillebrand). Sisyrinchium is confined to temperate and tropical America; but a singular and suggestive outlier of the genus (S. bermudiana) is found in Bermuda.

The mountain genera that are distributed on both sides of the Pacific constitute about three-fifths of the total. So far as my scanty data show, they seem to have reached Hawaii from the four quarters of the compass. The probable southerly origin of Plantago has been already indicated. Hillebrand notes the great resemblance between Lobelia gaudichaudii and an undescribed species from the Liukiu Islands, lying on the west side of the Pacific. It is likely, also, that the genus Ranunculus reached Hawaii from the west, since one of the species, R. mauiensis, resembles R. repens of the Old World (Hillebrand); whilst the other, R. hawaiiensis, comes near R. sericeus of Mauritius (Drake del Castillo). On the other hand, the genus Rubus may hail from an American source, since, in the opinion of Gray, Rubus hawaiiensis, one of the mountain raspberries, finds its nearest relative in R. spectabilis from the north-west coast of America; and there are reasons for believing, as will subsequently be shown, that the genus Artemisia has an American source. It is also probable that some of these genera have reached Hawaii from the north, since it is likely, as pointed out in a later page, that the Carices of the Hawaiian uplands came originally from north-eastern Asia.

In the previous paragraphs the mountain genera have been considered with especial reference to their distribution and source beyond the confines of the Pacific. If we now briefly discuss them from the standpoint of their distribution within the Pacific, or rather as concerning their presence or absence in the Fijian and Tahitian groups, we shall see that to a large extent Hawaii has received its mountain genera of this era independently of the other Pacific groups.

Mountain genera possessing only peculiar species, in Hawaii only20
Mountain genera possessing only peculiar species, in Hawaii and Fiji2
Mountain genera possessing only peculiar species, in Hawaii and Tahiti0
Mountain genera possessing only peculiar species, in all three groups4
—
26

It is here shown that three-fourths of the genera of the Hawaiian mountains in this era are not found either in Fiji or Tahiti. This, as before pointed out, is mainly to be attributed to the greater elevation of the Hawaiian Islands. Had there been an island 13,000 to 14,000 feet in height in Fiji, we cannot think that any such contrast in the floras would have existed. The temperate genera of the Hawaiian uplands would have been largely represented in the Fijian flora. Yet although we do not find such genera as Ranunculus, Geranium, Sanicula, Uncinia, &c., in Fiji and Tahiti, a small number of the Hawaiian mountain genera have obtained a scanty footing. This is what we might have expected. Thus, Lagenophora has been found on the mountains of Vanua Levu, and Vaccinium in Tahiti and Rarotonga; whilst Coprosma and Astelia occur on the tops of some of the mountains in both regions. In Fiji their distribution seems sporadic, as shown not in Lagenophora alone, but also by Astelia, which has been found only on the summit of Kandavu.

The Capacities for Dispersal of the Hawaiian Non-endemic Mountain Genera possessing only Peculiar Species.—As shown in the Table, seven, or 27 per cent., of these genera have fleshy fruits that would attract frugivorous birds. In three cases (Gunnera, Coprosma, Myoporum) they are drupes, in three others (Rubus, Vaccinium, Astelia) they are berries, and in one (Exocarpus) there is a nut with a fleshy perigone. It is particularly interesting to notice that frugivorous birds, and I include here granivorous birds that are known to be frugivorous at times, could have transported seeds of the “Antarctic” flora to this group. We can observe the process in operation in our own time within the limits of the group. It has been long known, and we find it referred to in the pages of Hillebrand’s work, that the wild mountain-goose (Bernicla sandwicensis) feeds upon the fruits of Coprosma ernodeoides, and of Vaccinium reticulatum, the famous “ohelo.” The fruits of the first are known to the natives as “kukai neenee” (droppings of geese), and the hard stones or pyrenes are very well suited for withstanding the risks of the digestive process. I found a number of these pyrenes in the stomach of a mountain-goose shot by my companion, Dr. Krämer, high up the slopes of Mauna Loa.

According to Mr. Perkins, Chloridops kona, a big Hawaiian finch, feeds on the fruits of the bastard sandal-tree (Myoporum sandwicense). There are no “impossible fruits” among the mountain genera of Hawaii, that is to say, fruits so large that bird agency must be excluded. All of them are practicable in point of size. Thus amongst the largest, the “stones” of Gunnera would not exceed 1⁄5 of an inch (5 mm.), and those of Myoporum scarcely 1⁄4 of an inch (6 mm.); whilst the nuts of Exocarpus range in the Hawaiian species from 3⁄10 to 6⁄10 of an inch (7-15 mm.), and the beans of Sophora chrysophylla do not at the most exceed 1⁄4 of an inch (6 mm.).

The principal feature, however, which these mountain genera exhibit from the point of view of their dispersal is the number of plants possessing seeds or fruits capable of adhering to plumage. Half of these genera are thus characterised. Of these Sanicula and Acæna represent the ordinary hooked fruits; whilst the fruits of the Grasses and Sedges, Agrostis, Deschampsia, Trisetum, Poa, Oreobolus, and Uncinia, are enabled by means of their awns or of their serrated beaks to attach themselves to plumage, and the same may be said of the carpels of Geranium. The fruits of Lagenophora and the seeds of Plantago display the capacity of adhesiveness by means of a gummy secretion.

One or two of these genera need further mention. I will first take Acæna, which is spread all over the south temperate zone both on the continents and on the islands. The Hawaiian species (A. exigua) forms tussocky growths on the swampy summits of Mount Eeka in Maui, and in Kauai, at an elevation of 6,000 feet above the sea. Numerous observers refer to the probable mode of dispersal of the genus in the “Antarctic” and neighbouring islands. Captain Carmichael, in the instance of Acæna sanguisorbæ on Tristan da Cunha, observes that it overruns the low ground. Its burr-like fruit, as he describes, “fixes itself on the slightest touch into one’s clothes, and falling into a hundred pieces covers one all over with an unseemly crust of prickly seeds not to be got rid of without infinite labour” (Trans. Linn. Soc., xii. 483, 1818). Both Mr. Moseley (Wallace’s Island Life, p. 250) and Dr. Kidder (Bull. U.S. Nat. Mus., 2) refer to the burrowing habits of the Petrels, Puffins, and other sea-birds amongst the vegetation covering the ground in Tristan da Cunha, Marion Island, Kerguelen, &c., in places where Acæna, amongst other plants, thrives. Mr. Moseley remarks that the fruits of this genus stick like burrs to feathers, and he looks to sea-birds for the dispersal of this and similar plants over the ocean. He especially notes that the Petrels and other seafowl burrow and breed high up the mountain-slopes of tropical islands as in Tahiti, Viti Levu, Hawaii, and Jamaica.... It should be noted in the case of the Hawaiian endemic species that it has been found only on two mountain tops; and that however active may be the dispersal of the genus in south temperate latitudes now, the Hawaiian Islands lie outside the present area of dispersal.

The next mountain genus I will specially refer to is Lagenophora, one of the Compositæ. The solitary Hawaiian endemic species, L. mauiensis, is restricted to the summit of Mount Eeka, in Maui. In the mountains of Vanua Levu, Fiji, another peculiar species, L. pickeringii, has been found; and there is a species, L. petiolata, in the Kermadec Islands (Hooker, in Journ. Linn. Soc., i. 127); but the genus is chiefly characteristic of Australia, New Zealand, and temperate South America, one species occurring both in Fuegia and Tristan da Cunha. The genus has no pappus; but Hooker in the case of the Kermadec species considered that the “viscid fruit” favoured its dispersal; and this may probably be true of the genus.

With regard to the capacity for dispersal of the seeds of Plantago, it may be pointed out that the seeds of Plantago major, P. lanceolata, &c., become coated with a mucilaginous material when wetted. In 1892, when experimenting on these plants, I found that the wetted seeds adhered firmly to a feather, so that it could be blown about without their becoming detached. Species of Plantago are so characteristic of the “alpine” floras of the summits of lofty mountains in the tropics, as in Java and many other regions, that the mode of dispersal has always been a subject of curiosity. I cannot myself doubt that this is the explanation of the occurrence of the representatives of the genus that now thrive as endemic species on the higher slopes of the Hawaiian mountains. This method of dispersal for Plantago is recognised by recent writers on the subject of seed-dispersal. (In a paper in Science Gossip for September, 1894, I dealt with the “mucous adhesiveness” of such seeds as a factor in dispersal. The subject had previously been discussed by Kerner in one of the earlier volumes of his Pflanzenleben; and I have summed up some of the results in [Note 43] of the present volume.) My readers can readily ascertain by a simple experiment that a bird pecking the fruit-spikes in wet weather would often carry away some of the sticky seeds in its plumage. Several years ago, when I was endeavouring to examine the condition of these seeds in the droppings of a canary, my efforts were defeated by the bird itself, since, in spite of all my care, some seeds and capsules were always carried by the bird on its feathers into the clean cage reserved for the experiment.

The plants of these mountain genera possessing dry seeds or fruits neither very large nor very minute and suitable for bird-food are Ranunculus, Viola, Vicia, Sophora, Artemisia, Sisyrinchium, six in all, or 24 per cent. of the total. On the probable method of transport of the ancestors of these endemic species the following remarks may be made. With regard to Ranunculus, some authors like C. M. Weed (Seed-Travellers, p. 48, Boston, 1899) perceive in the curved or hooked beaks of the achenes a means of attaching the fruit to plumage. This no doubt applies to some species, and it is advocated by Ekstam for some of the plants of the Nova Zembla flora. There are others to which this explanation would not be applicable, and the achenes of the Hawaiian species do not appear to be specially fitted for this mode of transport. I have found the achenes of Ranunculus frequently in the stomachs of birds in England, in partridges frequently, and in wild ducks at times. Those of certain species that possess buoyancy are common in the floating seed-drift of rivers, as of the Thames (Journ. Linn. Soc. Bot., xxix. 333), and they would probably in this way be often swallowed by waterfowl.

I have but few data directly relating to the dispersal of seeds of Viola by birds. From the frequent occurrence of species in alpine floras, as in the Caucasus, the Great Atlas, in the mountains of Equatorial Africa, in Madagascar, &c., it may be inferred that birds transport the seeds between the higher levels of many continental ranges in tropical regions and to the mountain-slopes of neighbouring large islands. Viola abyssinica, for instance, which occurs in Madagascar, is spread over the elevated mountain ranges of tropical Africa. With regard to the five Hawaiian species, it may be remarked that three of them are bog species and two occur in dry situations. The first are most characteristic of the mountains, one species occurring on the summit of Mount Eeka, 6,000 feet above the sea. Judging from the stations alone, at least two species were originally introduced into the Hawaiian Group.

Viola seeds, as indicated by my experiments on the different British species, including Viola palustris, are not buoyant, and there is no possibility of the seeds being picked up by birds in floating drift. There is, however, a possible means of dispersal in birds’ plumage by means of the mucosity of the seeds of some species. Thus, although this is not exhibited, as shown by my experiments, by Viola canina and V. palustris, it is well displayed by the Field-Pansy (V. tricolor). I found that the seeds of this species, after lying a little time in water, were thickly covered with mucus, and that they adhered to a feather, on drying, as firmly as if gummed. This did not, however, come under my notice in the case of the seeds of one of the Hawaiian species, V. chamissoniana, examined by me. One sometimes observes Viola canina in England growing in places, as in the crevices and on the tops of old walls, where its seeds could have only been carried by birds. In some cases the propellent force of the seed ejected by the contracting valves of the capsule would explain queer stations. In its power of seed-expulsion, Viola chamissoniana, the common Hawaiian species, is just as active as our British species.

With regard to the Leguminous genus Vicia we have the observation of Focke on the dispersal of its seeds by pigeons, as described before on page [150].

Sophora chrysophylla, the “Mamani” of the natives and one of the most familiar of the trees of the Hawaiian mountains, is discussed at length in [Chapter XV.], where the difficulty of supposing that its seeds could be transported unharmed in a bird’s stomach half-way across the Pacific is pointed out; and it is suggested that it was more probably derived from a littoral species brought by the currents. However, the point is a debatable one, and the seeds of the “Mamani” can scarcely be regarded as “impossible” from the standpoint of dispersal.

With reference to the possibilities of dispersal of the achenes of Artemisia, some very suggestive indications are to be obtained from a paper by Mr. D. Douglas on the North American Tetraonidæ published in the Transactions of the Linnæan Society for 1833. The “Cock of the Plains” (Tetrao urophasianus), as we here learn, makes its nest on the ground under the shade of Artemisia bushes, and lives on the foliage and fruits of these and other plants. This bird is plentiful in Columbia and North California, and another allied species is mentioned which lives on the same sort of food. Later authors refer to these and other birds of the same family as living chiefly on the Sage-brush (Artemisia tridentata), a plant prevailing over great regions of the plains as well as on the slopes of the Sierra Nevada and of the Rocky Mountains. According to Dr. Sernander (page [228]), birds when feeding on the fruits of Artemisia vulgaris in the district of Upsala scatter them about and thus aid in its dispersal. Artemisia achenes, since they have neither pappus nor other appendages, nor any special adhesiveness when wetted, depend largely on their small size and light weight to aid them in dispersal. (Those of A. absinthium measure a millimetre in length, or 1⁄25 of an inch, whilst those of A. vulgaris measure 1·8 mm., or 1⁄14 of an inch.) Driven as we are to look to bird-dispersal for the means of transport of Artemisia achenes, it is interesting to find a possible source of the Hawaiian endemic species on the nearest American mainland, even though it is some 2,000 miles away. It is assumed that they would be ordinarily carried in adherent soil or entangled in the feathers, and on rare occasions in the bird’s stomach.

The small seeds of Sisyrinchium possess no means of adherence to plumage. They are crustaceous, and in cases where the stomach and intestines of a bird are well filled with other food they are quite capable of resisting injury. The solitary Hawaiian species has, according to Hillebrand, a range in altitude from 3,500 to 7,000 feet. I found this pretty herb most abundant on the “cattle-plains” of Hawaii between 5,000 and 6,000 feet, where it is evidently in part dispersed by the cattle and other animals. The seeds are very small, being about a millimetre in size, and when dried nearly 100 go to a grain (0·65 decigramme). They might thus also be transported in mud on birds’ feet.

For the mode of dispersal of the minute seeds of Lobelia, the last of the mountain genera to be specially noticed, I must refer the reader to the remarks on this subject in [Chapter XXII.] They would probably be carried in soil adhering to the legs or feet of a bird.

There are one or two interesting points relating to the temperate genus Silene, which is represented on these mountains. The four Hawaiian species show a great range in altitude. Thus, whilst S. struthioloides finds its home in Hawaii and Maui at elevations of 5,000 to 9,000 feet, another species (S. lanceolata) thrives equally at elevations of 5,000 or 6,000 feet on the central plateau of Hawaii and at heights only of 300 to 500 feet above the sea. Although I have not yet come upon any direct reference to the mode of dispersal of the small seeds of this genus, there is little doubt that their rough tuberculated surfaces would favour their attachment to plumage. A very significant observation, however, is made by Jens Holmboe in a paper on littoral plants in the interior of Norway. He refers to the occurrence in no small quantity of Silene maritima on the top of “Linnekleppen,” 331 metres high, one of the highest peaks of Smaalenene, and distant about 29 kilometres from the nearest coast (Strandplanter i det indre af Norge, “Naturen,” Bergen, 1899). Sernander (p. 405), commenting on this observation, remarks that since bare hill-tops are frequented by birds, such an agency in this instance is not impossible.

I will conclude these remarks on the non-endemic Hawaiian mountain genera possessing only peculiar species, with a few observations on the genus Vaccinium in the Pacific. This genus is known to be distributed over the northern hemisphere and to occur on the uplands of tropical mountains, as, for instance, on the summits of the Java mountains and on the high levels of the Equatorial Andes at altitudes even of 15,000 to 16,000 feet. There are apparently only some four or five species known from the Pacific islands, from Hawaii, the Marquesas, Tahiti, Rarotonga, Samoa, and the New Hebrides, and it would almost seem that these can be reduced to one or two species. Although not yet recorded from Fiji, the probability of the genus being represented on some of the mountains is pointed out by Seemann. Of these Pacific forms a single species, V. cereum, is spread over the East Polynesian region including the Marquesas, Tahiti, and Rarotonga; and, according to Hillebrand, V. reticulatum, one of the two endemic Hawaiian species, is nearly related to it. Even the New Hebrides species (V. macgillivrayi) resembles it, according to Seemann, in general appearance. That there has been a single Pacific polymorphous species is, as shown below, not impossible; but Reinecke, in describing in 1898 the Samoan species, V. antipodum, was under the impression that it was the only species known from the southern hemisphere, and says nothing of its affinity to other Pacific plants.

A few words on the station and habit of Vaccinium in the Pacific islands may be here of interest. In Hawaii there are, according to Hillebrand, two species, a high-level form, V. reticulatum, occurring at elevations of 4,000 to 8,000 feet, and a low-level form, V. penduliflorum, ranging between 1,000 and 4,000 feet. I may, however, remark that the last species occasionally came under my notice at elevations of 6,000 to 7,000 feet. This species exhibits much variation, and Gray, Wawra, and other botanists have evidently not been always able to distinguish between the two species in their varying forms. It is not only distinguished from the high-level species by its lower station, but also by its epiphytic habit, a circumstance that, as pointed out below, may explain some of the differences, since such a habit is bound up with the difference in station. It seems, therefore, safer to regard them as station forms of one species which is closely allied to V. cereum, the species of the South Pacific, an inference which, if well founded, would make highly probable the view that there has been a single polymorphous Pacific species.... In Tahiti, as we learn from Nadeaud, V. cereum occurs on the mountain-tops at altitudes exceeding 800 metres (2,600 feet). In Rarotonga, according to Cheeseman, it is found on the summits of most of the higher hills extending almost to the summit of the island, 2,250 feet above the sea. The Samoan species, V. antipodum of Reinecke, which that botanist considers as probably one with V. whitmei, a Polynesian (Samoa?) species originally described by Baron F. von Müller, grows in the central mountains of Savaii at an elevation of 1,500 metres (4,920 feet).

These Pacific species of Vaccinium, as on tropical mountains of the continents, occasionally assume an epiphytic habit, and it is here, as above observed, that lies one of the distinctions between the Hawaiian species. V. penduliflorum, the low-level form, occurs typically in the forests, where, according to Hillebrand, it grows on the trunks of old trees. The trees, however, may be quite in their prime, and I have observed it growing in the fork of the trunk of an Olapa tree (Cheirodendron gaudichaudii). It is in this connection of significance to notice that a variety found in open glades and on grassy slopes is described by Hillebrand as terrestrial in habit. The other high-level form, V. reticulatum, grows gregariously on open ground, and is typically terrestrial in its habit. The Samoan species, as we learn from Reinecke, grows on trees, as on the branches of Gardenia. The epiphytic habit of species of Vaccinium is especially discussed by Schimper in the case of plants growing on the Java mountains. He there shows (Plant-Geography, i. 14) that species which are epiphytes in the virgin forest become terrestrial plants in the treeless alpine region. This interchange of station, which is exhibited by several other plants, including orchids and ferns, is connected with their xerophilous characteristics, and is given by Schimper as an example of the interchange of physiologically dry habitats.

Of the mode of dispersal of Vaccinium by frugivorous birds, much has been written and much will be familiar to my readers. The berries of V. reticulatum are known to be the principal food of the Hawaiian mountain-goose. But probably birds of the grouse family have been the chief agents in distributing the genus over the continents. I have frequently found the fruits in the stomachs of the Black Cock (Tetrao tetrix), the Scotch Grouse (Lagopus scoticus), and the Capercailzie (Tetrao urogallus); but the same story comes from all over the northern hemisphere. The Willow Grouse (Lagopus albus), which travels round the globe, is known to feed on them. Hesselman in Sweden and Ekstam in Nova Zembla have especially investigated the dispersal of Vaccinium by Tetrao tetrix and Lagopus (see Sernander, pp. 6, 226); and according to Mr. Douglas and others the different species of Tetrao that frequent the subalpine regions of the Rocky Mountains and the uplands of Columbia and North California subsist on Vaccinium fruits. This family is not now represented in the Hawaiian avifauna; but it is noteworthy, as indicated by the differentiation of the Pacific species of Vaccinium, that dispersal of the genus is there almost suspended except within the region of Eastern Polynesia. It is probable that numerous other birds, except the Hawaiian goose, aided the original dispersal.

The Mountain Genera with both Endemic and Non-endemic Species.—I pass on now to consider those Hawaiian mountain genera that possess species some of which are confined to the group, whilst others occur in regions outside the islands. They are not many, as may be seen from the table before given, and but few of them are entirely restricted to the high levels, a range in altitude that may be frequently associated with great lateral extension of the genus over different latitudes. Here the agents of dispersal have through some species in each genus preserved a connection with the outer world, though it may be restricted to the limits of the Pacific islands.

Cyathodes tameiameiæ, an Epacridaceous species found also in the uplands of Tahiti, occurs, according to Hillebrand, on all the Hawaiian Islands, from 1,800 feet up to the limit of vegetation 10,000 feet and over above the sea. I found it, however, at even lower levels. On the Puna coast of Hawaii, associated with Metrosideros polymorpha, Osteomeles anthyllidifolia, and other inland plants, it descends on the surface of ancient lava-flows to the coast wherever the bolder spurs reach the sea-border. The other species, C. imbricata, is more exclusively confined to the greater altitudes. It is endemic, and may possibly be a station form of the other species.

The six species of Lysimachia are found at different elevations, one near the sea-shore, others at altitudes of 2,000 to 3,000 feet, and others again at elevations of 6,000 feet. Chenopodium sandwicheum occurs at all elevations from near the coast to the high inland plains of Hawaii and to the upper slopes of Mauna Kea, that is to say, up to altitudes of 6,000 or 7,000 feet. Hillebrand observes that it is a low decumbent plant at the coast, and may become arborescent with a height of 12 to 15 feet in the upper forests of Mauna Kea.

The species of Santalum (sandal-wood trees) also display great vertical range in these islands. Though S. freycinetianum, which is also a Tahitian species, is most at home in the forests 2,000 to 4,000 feet above the sea, it has, as Hillebrand informs us, a dwarfed form that extends far up the mountain slopes of Mauna Loa and Hualalai to elevations of 7,000 or 8,000 feet, and another dwarfed shrubby variety that grows only near the sea-shore. Another species, S. haleakalæ, occurs as a tall shrub on Haleakala at elevations of 8,000 to 10,000 feet. Among the sedges, most of those of the genera Carex and Rhynchospora are found at altitudes of between 3,000 and 7,000 feet, and two grasses of the genus Deyeuxia occur at elevations of 6,000 to 8,000 feet.

Amongst these Hawaiian mountain genera with both endemic and non-endemic species there are no plants possessing fruits which from their size could be with difficulty regarded as dispersed by birds. The mode of dispersal of these plants is in some cases indeed not far to seek. Thus in the stomach of an Hawaiian goose (Bernicla sandwicensis), shot by my companion Dr. Krämer on the slopes of Mauna Loa, I found a number of the “stones” of Cyathodes tameiameiæ, the plant being abundant in fruit in the immediate vicinity. It is highly probable that the seeds of Santalum have been carried over the Pacific by frugivorous birds. We learn from Dr. Brandis that Santalum album in India is mainly spread through the agency of birds (Bot. Chall. Exped., iii. 13). The drupes of the Pacific species, S. freycinetianum, that occurs alike in Hawaii, the Marquesas, and Tahiti (Drake del Castillo), measure about half an inch. There can be little doubt that with this tree, as with the species of Cyathodes above mentioned, which also links together Tahiti and Hawaii, there has been up to recent times an interchange by means of frugivorous birds between these two regions, some 2,000 miles apart.

The small seeds of the capsular fruits of Lysimachia could be transported in birds’ plumage or in dried soil attached to their feet or feathers. The seed-like fruits of Chenopodium were probably dispersed by some granivorous bird, much as nowadays our partridges carry about in their stomachs the similar fruits of Atriplex. The long-awned fruits of Deyeuxia were, it is likely, transported in birds’ plumage, and doubtless also those of Panicum; whilst the nutlets of Carex and Rhynchospora might have been carried about in a similar fashion.

The distribution of the non-endemic species of these Hawaiian mountain genera may perhaps aid us in determining the original source of the genus as well as in confirming the conclusions formed concerning the other mountain genera that only possess species restricted to the group. Lysimachia, Chenopodium, Carex, Rhynchospora, Deyeuxia, and Panicum are found in both the Old and New Worlds. Since Hillebrand remarks that one of the six species of Lysimachia (L. spathulata) occurs in Japan and in the Liukiu, Bonin, and Marianne groups, we have here a valuable indication of the route followed by a genus that has not been recorded from the oceanic groups of the South Pacific.

The capricious distribution of the genus Carex in the Pacific is remarkable, and it is noticed by Hemsley in the Introduction to the Botany of the “Challenger” Expedition. No species have been recorded from Tahiti, the Marquesas, and Rarotonga, but three Fijian species are mentioned by Hemsley, and there is another in Samoa. Of the five Hawaiian species given by Hillebrand, two are endemic. Of the rest, C. wahuensis (oahuensis), Meyer, occurs also in Korea and Japan, whilst C. brunnea, Thunb., is found in Japan and Australia, and the third, C. propinqua, Nees., occurs all round the border of the Pacific Ocean, from Kamschatka through Alaska south to the Straits of Magellan. These three species all possess a home in common in north-east Asia, and probably there lies the source of the Hawaiian species of Carex—a conclusion which would help to explain the irregular distribution of the genus amongst the South Pacific groups.

The genus Rhynchospora occurs alike in the Hawaiian, Tahitian, and Fijian islands; but the groups in the North and South Pacific seem to have been independently supplied with the original species, since R. aurea, a widely spread tropical species, ranging the South Pacific from New Caledonia to Tahiti, has not been recorded from Hawaii. A connection between Hawaii and the Australian region seems to be indicated by a species of Deyeuxia (D. forsteri) that is found also in Easter Island, Australia, and New Zealand, and by the presence of the Australian and New Zealand genus Cyathodes in Hawaii, though the existence of a species common to both Tahiti and Hawaii goes to show that the route followed by the genus lay through Eastern Polynesia. It is also not unlikely that the genus Santalum reached Hawaii through Eastern Polynesia, since two forms found in Hawaii and Tahiti are closely allied, and are, in fact, regarded by Drake del Castillo as the same species. The genus occurs in tropical Asia, Australia, and New Zealand.

Looking at the indications above given, I should be inclined to think that the genera Lysimachia and Carex reached the Hawaiian mountains from temperate Asia or the islands off its Pacific coast, and that Cyathodes, Santalum, and Deyeuxia hail from the Australian or New Zealand region by way of Eastern Polynesia.

The Mountain Genera possessing no Endemic Species.—The few remaining mountain plants of Hawaii to be considered are solitary, widely ranging species of genera that here possess no peculiar species. Such may be regarded as belonging to the latest age of the indigenous plants. They still keep up, or kept up until recently, the connection with the world outside Hawaii, and among them one may name here Fragaria chilensis, Drosera longifolia, Nertera depressa, and Luzula campestris.

Fragaria chilensis, the Chilian strawberry, flourishes at elevations of between 4,000 and 6,000 feet on the Hawaiian mountains. Its fruits, according to Hillebrand and other authors, are much appreciated by the wild goose of the islands. This plant ranges in America from Chile north to Alaska; and Drake del Castillo is doubtless on safe ground when he assumes that a congener of this bird originally brought the species from the nearest part of the American continent, namely from California (Remarques, &c., p. 8). In this connection it should be remembered that one of the endemic mountain-raspberries of Hawaii (Rubus hawaiiensis) finds its nearest relative, according to Gray, in Rubus spectabilis, a species from the north-west coast of America.

The species of Sun-dew, Drosera longifolia, hitherto found only on the marshy tableland of Kauai at an elevation of 4,000 feet above the sea, occurs both in Asia and North America. Its minute fusiform seeds are very light in weight, and might readily become entangled in a bird’s plumage, or they could be carried in adherent dried mud.

Luzula campestris, which grows on the high mountains of the Hawaiian group from 3,000 feet upward, is also found in Tahiti. It is widely distributed in cool latitudes, and there is no special indication of its source. Its seeds are especially well suited for adhering to birds’ feathers. When experimenting on these seeds in 1893 I ascertained that whether freshly gathered or kept for more than a year they became on wetting coated with mucus, and adhered firmly to a feather on drying. There are many ways in which the “sticky” seeds in wet weather might fasten themselves to a bird’s plumage. The plant-materials might be used, for instance, for making nests. The Sea Eagle (Aquila albicilla), as we learn from Mr. Napier (Lakes and Rivers), uses materials derived from Luzula sylvatica in the construction of its nest.

Nertera depressa, a creeping Rubiaceous plant, with red, fleshy drupes containing two coriaceous pyrenes, is found in all the Hawaiian Islands at elevations of 2,500 to 5,000 feet, and it grows on the mountains of Tahiti at altitudes over 3,000 feet. The genus is widely diffused over the southern hemisphere. This particular species is characteristic of the Antarctic flora, being found all round the south temperate zone (excepting South Africa) in New Zealand, Fuegia, the Falkland Islands, and Tristan da Cunha, and extending up the Andes to Mexico, occurring also on the summits of Malayan mountains at elevations of 9,000 to 10,500 feet above the sea, as on Pangerango in West Java (Schimper), and on Kinabalu in North Borneo (Stapf). Captain Carmichael, who resided on Tristan da Cunha in the early part of last century, states (Trans. Linn. Soc., xii. 483) that its drupes are eaten by a species of thrush and by a bunting. Professor Moseley, who visited the island in the Challenger many years after, remarks that its fruits are “the favourite food of the remarkable endemic thrush, Nesocichla eremita,” the bunting being Emberiza brasiliensis (Bot. Chall. Exped., ii. 141). It would seem most likely that the Hawaiian Islands received this representative of the Antarctic flora through the Tahitian Islands, as in the case of the species of Cyathodes common to both these groups.

Looking at the indications of these four widely ranging plants, the Chilian strawberry (Fragaria chilensis), the Sun-dew (Drosera longifolia), Nertera depressa, and Luzula campestris, it may be inferred that with the exception of Nertera they all reached Hawaii from either the Asiatic or American sides of the North Pacific, the last route being evident in the case of the strawberry. Nertera depressa was probably derived from southern latitudes.

Summary.

(1) The second era of the flowering plants of the Pacific islands is indicated by the non-endemic genera. Here also the isolating influences have been generally active, and the work of dispersal is in some regions largely suspended. Thus in Hawaii nearly half the non-endemic genera possess only species that are restricted to the group, whilst in Fiji and Tahiti about a fourth are thus isolated.

(2) The contrast in the elevations of the islands of the Hawaiian, Tahitian, and Fijian regions is reflected in the development of an extensive mountain-flora in Hawaii, in its scanty development in Tahiti, and, excluding the Fijian conifers, in a mere remnant in Fiji and Samoa.

(3) The influence of isolation has been very active in the Hawaiian mountains, since about two-thirds of the genera contain only species confined to the group, and are thus disconnected from the world outside.

(4) Amongst these disconnected Hawaiian mountain genera, Antarctic or New Zealand genera, like Acæna, Gunnera, Coprosma, and Lagenophora, constitute nearly a third. The American element, represented, for instance, by Sanicula and Sisyrinchium, is small; whilst the genera found on both sides of the Pacific form more than one-half of the total, and include genera like Ranunculus, Viola, Rubus, Artemisia, Vaccinium, and Plantago, that often represent the flora of the temperate zone on the summits of tropical mountains. Three-fourths of these genera are not found either in Fiji or in Tahiti.

(5) The proportion of the disconnected Hawaiian mountain genera possessing seeds or seedvessels suited for dispersal in a bird’s plumage is very large, quite half belonging to this category; whilst only about a fourth have fruits that would be dispersed by frugivorous birds.

(6) The Hawaiian mountain genera that still remain in touch with the external world through species found outside the islands whilst other species are confined to the group, present a later stage in the plant-stocking. Their widely ranging species, which would be dispersed either by frugivorous birds, as with Santalum and Cyathodes, or in birds’ plumage, as with Lysimachia, Carex, and Deyeuxia, seem to indicate that the main lines of migration for these genera have been from temperate Asia and from the Australian and New Zealand region, the last by way of Eastern Polynesia.

(7) The latest stage of the Hawaiian mountain-flora is exemplified by those genera that are only represented in the group by a solitary widely-ranging species, such as Fragaria chilensis, Nertera depressa, Drosera longifolia, and Luzula campestris. It is our own age; and birds are shown to be actual agents in the dispersal of the two first-named species and to be probable agents with the two other species. The two last-named species probably reached Hawaii from one or other side of the North Pacific; whilst Fragaria chilensis doubtless hails from the adjacent part of the American continent, and Nertera depressa from high southern latitudes by way of Tahiti.

CHAPTER XXIV
THE MOUNTAIN-FLORAS OF THE TAHITIAN AND FIJIAN REGIONS

The mountain-flora of the Tahitian region, as illustrated by the non-endemic genera.—Derived chiefly from high southern latitudes.—Weinmannia, Coprosma, Vaccinium, Astelia, Coriaria, Cyathodes, Nertera depressa, Luzula campestris.—The mountain flora of Rarotonga.—The mountain-flora of the Fijian region, as illustrated by the non-endemic genera.—Weinmannia, Lagenophora, Coprosma, Astelia, Vaccinium, Nertera depressa.—The Fijian Coniferæ.—Dammara, Podocarpus, Dacrydium.—Not belonging to the present era of dispersal.—The age of dispersal of the Coniferæ in the Pacific.—Earlier than the age of Compositæ and Lobeliaceæ.—The first in the Mesozoic period.—The last in the Tertiary period.—Summary.