INTRODUCTION

The study of insular floras.—Their investigation in this work from the standpoint of dispersal.—The significance of plant-distribution in the Pacific.—The problems connected with the mountain-flora of Hawaii.—The persistence of dispersing agencies at the coast, their partial suspension on the mountain-top, their more or less complete suspension in the forest, and the effect on the endemic character of plants.—The connection between the endemism of birds and plants.—The relative antiquity of plants of the coast, forest, and mountain-top.—The genetic relation between coast and inland species of the same genus.—The ethics of plant-dispersal.—Evolution takes no heed of modes of dispersal.—The seed-stage is the price of Adaptation.

The initial experiment.—The proportion of littoral plants.—The two great principles of buoyancy.—The investigations of Professor Schimper.—The investigations of the author.—The great sorting process of the ages.—Preliminary results of the inquiry into the buoyancy of seeds and fruits.

Results of observations on the buoyancy of over 300 British plants.—The small proportion of plants with buoyant seeds or seedvessels.—Their station by the water-side.—The great sifting experiment of the ages.—Summary.

The choice of station of the water-side plant possessing buoyant seeds or seedvessels.—Determined by its fitness or unfitness for living in physiologically dry stations.—In the internal organisation of a plant lies the first determining influence of station.—The grouping of the British strand-plants.—Whilst the Xerophyte with buoyant seed or fruit finds its station at the coast, the Hygrophyte similarly endowed makes its home at the river or pond side.—The grouping of the plants of the river and the pond.—Summary.

The inland extension of the beach-plants.—The grouping of the coast-plants.—Their modes of dispersal.—The zone of change.—Summary.

Lacks the mangroves and their associated plants.—Possesses mainly the plants of the coral beach.—Predominant agency of the currents.—Inland extension of shore-plants.—Summary

Its poverty.—Its negative features.—Their explanation.—The subordinate part taken by the currents.—The Oregon drift.—The inland extension of the beach-plants.—Summary

The working value of the currents as plant-dispersers.—The relation between the currents and the distribution of shore-plants.—The clue afforded by the American plants.—Two regions of tropical shore-plants, the American and the Asiatic.—America, the home of the cosmopolitan tropical shore-plants that are dispersed by the currents.—Hawaii and the currents.—Summary

Germination in the floating seed-drift of tropical estuaries.—A strain of vivipary.—Abortive germination of seeds in warm seas.—A barrier to plant dispersal.—The borderland of vivipary.—Summary

The general principles concerned.—The subject assumes a statistical character.—Seeds and seedvessels are as a rule either much heavier than sea-water or much lighter than fresh water.—The present littoral plants with buoyant seeds or seedvessels could be equally well dispersed by currents in oceans of fresh water.—Seed-buoyancy has no relation either in the present or in the past to the density of the sea.—Though an accidental attribute, the specific weight of seeds has had a profound influence on plant-distribution.—Summary

Nature has never concerned herself directly with providing means of dispersal.—Fleshy fruits not made to be eaten.—Nor “sticky” seeds to adhere to plumage.—Nor prickly fruits to entangle themselves in fur and feathers.—The dispersal of seeds a blind result of the struggle between the intruding Evolutionary power and the controlling influence of Adaptation.

The classification of buoyant seeds and fruits.—The first group, where the cavity of the seed or seedvessel is incompletely filled.—The second group, where the kernel is buoyant.—The third group, where there is air-bearing tissue in the seed-tests or fruit-coats.—The buoyant seeds and seedvessels of the littoral plants of the British flora.—Summary

The question of the operation of Natural Selection.—Are there two principles at work?—The presence of buoyant tissue in the seed-tests and fruit-coats of inland plants, both wild and cultivated.—Useless buoyancy.—The buoyancy of seeds and fruits is not concerned with Adaptation.—Summary.

Professor Schimper’s views.—Great antiquity of the mangrove-formation.—Problem mainly concerned with the derivation of inland from littoral plants.—Grouping of the genera possessing both coast and inland species.—ScÆvola.—Morinda.—Calophyllum.—Colubrina.—Tacca.—Vigna.—Premna

Inland species of a genus developed from littoral species originally brought by the currents but no longer existing in the group.—Illustrated by the Leguminous genera Erythrina, Canavalia, Mezoneuron, and Sophora, and by the Apocynaceous genus Ochrosia.—The Hawaiian difficulty.

The Fijian difficulty.—Inland species of a genus possessing fruits not known to have any means of dispersal through agencies now at work in the Pacific.—Pandanus.—Its remarkable distribution in oceanic groups.—To be attributed perhaps to extinct ColumbÆ or extinct Struthious birds.—Barringtonia.—Guettarda.—Eugenia.—Drymispermum.—Acacia laurifolia.—Conclusions to be drawn from the discussion.—Summary of Chapters XIV., XV., XVI.

Afzelia bijuga.—The African home of the genus.—The double station of Afzelia bijuga, inland and at the coast.—The nature of the buoyancy of its seeds.—Summary relating to Afzelia bijuga.—Entada scandens.—Its station and distribution.—Darwin’s opinion of the plant.—The dispersal of its seeds by the currents.—Summary relating to the plant.—CÆsalpinia bonducella and C. bonduc.—Their station and distribution.—Their characters in various Pacific groups.—The parents of inland species.—Their dispersal by the currents.—The germination of their seeds.—A dream of vivipary.—The causes of the seed-buoyancy.—Summary of results

LeguminosÆ predominate in tropical littoral floras.—The anomalies of their distribution in the Pacific islands.—They conform to no one rule of dispersal or of distribution.—Strangers to their stations.—The American home of most of the Leguminous littoral plants.—Summary

Introductory remarks.—The tranquil working of the winds and currents contrasted with the revolutionary influence of the bird.—The Hawaiian, Fijian, and Tahitian groups.—Their surface-areas and elevations.—Their climates.—The mountain climate of Hawaii.—The rainfall of the three groups.—Summary

The eras in the plant-stocking.—The age of ferns and lycopods.—The relative proportion of vascular cryptogams in Hawaii, Fiji, and Tahiti.—The large number of peculiar species in Hawaii.—The mountain ferns of Hawaii.—The origin of peculiar species.—Dr. Hillebrand’s views.—Their origin connected not with greater variety of climate in Hawaii, but with isolation.—Summary

The islands of the tropical Pacific as the homes of new genera and new species.—The significance of a large endemic element.—Synopsis of the eras.—The era of endemic genera.—The endemic genera of CompositÆ.—Their affinities and mode of dispersal.—The mystery of the suspension of the dispersing agencies.—Mr. Bentham’s views.—The remnant of an ancient Composite flora in the tropical Pacific.—The dispersion of the CompositÆ antedates the emergence of the island-groups of the Fijian region at the close of the Tertiary period.—Summary

The distribution of the arborescent LobeliaceÆ.—On the upper flanks of Ruwenzori.—The LobeliaceÆ of the Hawaiian Islands.—The LobeliaceÆ of the Tahitian or East Polynesian region.—The capacities for dispersal.—The explanation of the absence of the early LobeliaceÆ from West Polynesia.—The other Hawaiian endemic genera.—The Fijian endemic genera.—Summary

The mountain-flora of Hawaii.—A third of it derived from high southern latitudes.—An American element.—Compared with Tahiti and Fiji.—Capacities for dispersal of the genera possessing only endemic species.—AcÆna, Lagenophora, Plantago, Artemisia, Silene, Vaccinium, &c.—Capacities for dispersal of the genera possessing non-endemic species.—Cyathodes, Santalum, Carex, Rhynchospora.—Fragaria chilensis, Drosera longifolia, Nertera depressa, Luzula campestris.—Summary.

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

The Age of the Malayan Plants as represented in the Low-level Flora of Hawaii and in the Bulk of the Floras of the Fijian and Tahitian Regions

The widely dispersed genera which possess only peculiar species in Hawaii.—Pittosporum.—Reynoldsia.—Gardenia.—Psychotria.—Cyrtandra.—Freycinetia.—Sapindus.—Phyllanthus.—Pritchardia.—Summary.

The widely dispersed genera that are as a rule not entirely represented by endemic species in any archipelago.—ElÆocarpus.—DodonÆa.—Metrosideros.—Alyxia.—Alphitonia.—Pisonia.—Wikstroemia.—Peperomia.—Eugenia.—Gossypium.—The last stage in the general dispersal of plants of the Malayan era as illustrated by the widely-dispersed genera having as a rule no peculiar species.—Rhus.—Osteomeles.—Plectronia.—Boerhaavia.—Polygonum.—Pipturus.—Dianella.—Summary.

Synopsis of the Chapter given on page 359

Identity of the problems presented by the indigenous plants and the peoples of the Pacific islands.—The food-plants of the Polynesians and the pre-Polynesians.—Their weeds.—The aboriginal weeds.—The white man’s weeds.—Weeds follow the cultivator but are distributed by birds.—The general dispersion of weeds antedates the appearance of the Polynesian in the Pacific.—Weeds of little value to the ethnologist.—Aleurites moluccana.—Inocarpus edulis, Gyrocarpus Jacquini, Serianthes myriadenia, LeucÆna Forsteri, MussÆnda frondosa, Luffa insularum.—Summary

In the south of England.—On the coast of Scandinavia.—In the Mediterranean.—Southern Chile.—Very little effective dispersal by currents in temperate latitudes.—Cakile maritima.—In tropical regions.—River drift.—River and beach drift of Fiji.—Musa Ensete.—The coco-nut.—River and beach drift of Hawaii.—Comparison of the beach drift of the Old and New Worlds.—Summary

Rhizophora.—Represented by Rhizophora mucronata, Rhizophora mangle, and the Selala, a seedless intermediate form.—Their mode of association and characters.—The relation of the Selala.—Polyembryony.—The history of the plant between the fertilisation of the ovule and the detachment of the seedling.—Absence of a rest period.—Mode of detachment of the seedling.—Capacity for dispersal by the currents.—Bruguiera.—The mode of dispersal.—Peculiar method of fertilisation.—Length of period between fertilisation and the detachment of the seedling.—Mode of detachment of the seedling.—Summary

The significance of vivipary.—The scale of germinative capacity.—A lost habit with many inland plants.—The views of Goebel.–-The shrinking in the course of ages of tropical swamp areas.—The variation in the structures concerned with vivipary.—Abnormal vivipary.—Summary.

The littoral floras of the West Coast of South America.—The Convolvulus soldanella zone of Southern Chile.—The plantless or desert zone of Northern Chile.—The Sesuvium zone of Peru.—The Mangrove zone of Ecuador and Colombia.—The two varieties of Rhizophora mangle, the “mangle chico” and the “mangle grande.”—The floating vegetable drift of the Guayaquil River.—The Humboldt current and the climate of the West Coast of South America.—The advance northward of the arid climatic conditions of the Peruvian sea-border.—The retreat of the mangroves.—Evidence of ancient coral reefs on the coast of Peru.—The shore plants and stranded seed-drift of the Panama Isthmus.—Summary.

The shifting of the source of Polynesian plants from the New to the Old World.—The floral history of Polynesia stated in terms of geological time.—The suspension of the agencies of dispersal in later periods.—Parallel differentiation in the course of ages of climate, bird, and plant.—New Zealand.—Insects and bats as agents in plant-dispersal.—The effective agency of sea-birds in other regions.—The observations of Ekstam.—The Spitzbergen controversy.—The efficacy of ducks as distributors of aquatic plants.—Summary

General Argument and Conclusion	Pages 515-523
APPENDIX	Pages 525-605