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Full text of "Observations of a naturalist in the Pacific between 1896 and 1899"

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OBSERVATIONS OF A NATURALIST IN THE 
PACIFIC BETWEEN 1896 AND 1899 




[Frontispiece- 



Fruits with seedlings nearly ready to fall from the tree o 

Rhizophora mangle (shortest) and Rhizophora mucronat: 

(longest). From Vanua Levu, Fiji. ({ of the tru 

length.) 



Rhizophora mangle (Vanua Levu. Fiji) (!). 



Rhizophora mucronata (Vanua Levu, Fiji) (]). 



OBSERVATIONS OF 
A NATURALIST IN 
THE PACIFIC BETWEEN 

1896 AND 1899 



BY 

H. B. GUPPY, M.B., F.R.S.E. 



VOLUME II 

PLANT-DISPERSAL 



ILonfcon 
MACMILLAN AND CO., LIMITED 

NEW YORK : THE MACMILLAN COMPANY 
1906 

All rights retervtd 



Q 



EARTH 
SCIENCES 



RICHARD CLAY AND SONS, LIMITED, 

BREAD STREET HILL, E.G., AND 

BUNGAY, SUFFOLK. 



JDeMcatton 

TO THOSE NUMEROUS PERSONS TO WHOM I WAS INDEBTED FOR 

GREAT KINDNESS AND ASSISTANCE DURING MY 

SOJOURN IN HAWAII AND FIJI 



PREFACE 

ALTHOUGH this volume contains a great amount of original 
material, I am largely indebted to the labours of my predecessors 
for its present form ; and a scheme that at first was limited 
only to my own observations in the Pacific has gradually ex- 
tended itself to the general subject of plant-dispersal. The 
farther I proceeded in my work the more I realised that the 
floras of the Pacific islands are of most interest in their con- 
nections, and that the problems affecting them are problems 
concerning the whole plant-world. Deprived of the writings 
of Seemann, Hillebrand, Drake del Castillo, and other botanists, 
several of whom have lived and died in the midst of their 
studies of these floras, and without the aid of the works of 
Hemsley and Schimper, generalisers who have mainly cleared 
the way for the systematic study of plant-distribution and 
plant-dispersal, it would not have been possible for me to ac- 
complish such an undertaking. 

My interest in plant-dispersal dates back to 1884, when, 
whilst surgeon of H.M.S. Lark, in the Solomon Islands, I made 
some observations on the stocking of a coral island with its 
plants, which were published in the Report on the Botany of 
the "Challenger" Expedition. In 1888 I followed up the same 
line of investigation during a sojourn of three months on 
Keeling Atoll, and during a journey along the coasts of West 
Java. But realising that as yet I had barely touched the 
fringe of a great subject, and that several years of study would 
be required before one could venture even to appreciate the 
nature of the problems involved and much less to weigh results, 



viii PREFACE 

I took advantage of the circumstances of my life to make, 
between the years 1890 and 1896, a prolonged investigation of 
the plants of the British flora, mainly from the standpoint of 
dispersal by water. This involved the study of the seed-drift 
of ponds and rivers and of the plants supplying it, a study 
which brought me into close relation with aquatic and sub- 
aquatic plants. This line of investigation led me into contact 
with many other aspects of plant-life ; and as time went on 
my field of interest extended to the plants of dry stations and 
to the bird as an agent in plant-dispersal. Only a few of these 
results have been published, as in the journals of the Linnean 
Society and of the Royal Physical Society of Edinburgh as well as 
in the pages of Science Gossip. They lie for the most part still 
within my note-books, and fitly so, since I regarded such studies 
chiefly as a preparation for the investigation of the general 
question of plant-dispersal. 

When again, in October, 1896, I found myself once more in 
the Pacific, the subject was taken up again with zeal ; but my 
larger experience had only increased my diffidence, and the 
unknown looked so overwhelming that I settled down for the 
next three years content with merely making experiments and 
recording observations. Here again the main problem was 
attacked through the study of seed-buoyancy, and gradually 
it led me to the systematic study of the mangroves and of the 
beach-plants, whilst my inland excursions brought me into 
familiarity with the plants of the interior. My geological 
exploration of the island of Vanua Levu, in Fiji, greatly 
assisted me by giving a method to my botanical examination 
of the island. 

Whilst working out my geological collections in England, in 
the years 1900-1902, I devoted an hour or two daily to the 
elaboration of my botanical notes and to a consideration of 
the problems concerned. During a winter in Sicily I took up 
again the subject of the beach-plants ; and after the publica- 
tion of the volume on the geology of Vanua Levu I was able 
to accomplish a plan, for years in my dreams, of visiting the 
eastern shores of the Pacific. During a period of three months 



PREFACE ix 

from December, 1903, to March, 1904, I examined the littoral 
flora of the west side of South America at various localities 
between Southern Chile and Ecuador ; and finally completed 
this investigation by comparing the shore-plants on the Pacific 
and Atlantic coasts of the isthmus of Panama. Returning to 
England with a fresh collection of data, I passed many months 
in elaborating and arranging all my notes, waiting vainly for a 
clue to guide me in framing a scheme by which I could bring 
the results of many years of work into some connected form. 
At last I decided once again to take the floating seed as my 
clue, and without any prearranged plan I allowed the work to 
evolve itself. Now that it is finished, I can see some obvious 
defects ; but if any other plan had been adopted I scarcely 
think that I should have been more successful in piecing 
together in a single argument materials resulting from so 
many years of research and relating to so many aspects of 
plant-life. 

Yet the final object of a naturalist would be but a sorry one, 
if his aim were only to write a treatise and append his name to it. 
His personal faith lies behind all his work ; and no one can pursue 
a long line of study of the world around him without rising from 
his task with some convictions gained and some convictions lost. 

As far as the observation of Nature's processes at present in 
operation can guide us, the world presents itself to us only as a 
differentiating world. We can perceive, it is true, a progressive 
arrangement of types of organisms from the lowest to the highest, 
and we can perceive a development of varieties of the several 
types ; but the only process evident to our observation is that 
concerned with the production of varieties of the type. Nature 
does not enlighten us as to the mode of development of the type 
itself. We can, for instance, detect in actual operation the process 
by which the different kinds of bats or the different kinds of men 
have been developed ; but there is no principle in Nature evident 
to our senses that is concerned with type-creation. Though we 
can supply it by hypothesis, we cannot discover it in fact. On the 
other hand, the evidence of differentiation is abundant on all sides 
of us, both in the organic and in the inorganic worlds. The history 



x PREFACE 

of the globe has ever proceeded from the uniform to the complex ; 
and in the closing chapter of this book an endeavour is made to 
connect the differentiation of plant and bird with the differentiation 
of the conditions of existence on the earth. But this leaves no 
room for the development of new types of organisms ; and so far 
as observation of the processes of Nature at present working around 
us can guide us, each type might well be regarded as eternal. We 
can never hope to arrive at an explanation of the progressive 
development of types by studying the differentiating process ; 
and since the last is alone cognisable for us, evolution, as it is 
usually termed, becomes an article of our faith, and of faith only. 

In illustration of this argument, let me take the case of the 
races of men. We see mankind in our own day illustrating the 
law of differentiation all over the globe, as far as physical charac- 
ters are concerned. Just as the ornithologist would postulate a 
generalised type in tracing the origin of various allied groups of 
birds, so the anthropologist, guided by his observation of the 
changes now offered by man in different regions, would postulate 
a generalised original type as the parent-stock of mankind. 
Observation of the processes of change now in operation by no 
means leads us to infer that such a generalised type was an 
anthropoid ape, or even simian in character. In so doing we 
should be forming a conclusion not warranted by the observation 
of existing agencies of change, and we should be confusing the 
two distinct processes of evolution and differentiation, or rather 
of progressive and divergent evolution, of which the last alone 
comes within our field of cognition. The study of variation can 
do no more than enable us to ascertain the mode of development 
of different kinds, we will say, of birds or of men. The origin of 
the type lies outside our observation. " Given the type, to explain 
its origin " : this is the problem we can never solve, and Nature 
aids us nothing by the study of her ways. On the other hand, 
there is the subsidiary problem ..." Given a type, to explain its 
varieties " . . . ; and here Nature's processes are apparent to us in 
a thousand different shapes. 

It might seem that the presumptive evidence connecting man 
in his origin with the monkeys is so strong that, supposing his 



PREFACE xi 

simian descent were regarded as a crime, a jury would without 
hesitation pronounce his guilt ; but until some observer of the 
processes followed by Nature can bridge over the gap that divides 
man from the ape, until indeed he can offer a legitimate illustration 
of how it is accomplished in similar cases in our own day, the gap 
remains. Those who have read the recent work of Prof. Metchni- 
koff on the Nature of Man will properly regard his chapter on the ' 
simian origin of man as a brilliant argument advanced by a most 
competent authority. Yet he fails to complete his case by bridging 
over this gap, and can only appeal to the results of the now 
famous researches of De Vries concerning the mutations of the 
evening primrose (CEnothera). It is probable, he says, that man 
owes his origin to a similar phenomenon (English edition, p. 57). 
Several objections could be raised against this illustration from 
the plant-world, the most important of them lying in the circum- 
stance that these mutations could only be urged as instances of 
the sudden development of new species of the evening primrose 
type. They merely illustrate the process of differentiation from 
a given type, and by no means represent the process of progressive 
evolution from a simian to a man. 

However, look where we may and this is the great lesson I 
have learned from my researches in the Pacific islands Nature 
does not present to our observation any process in operation by 
which a new type of organism is produced. The processes involved 
lie hidden from our view. The channels by which impressions 
from the outside world reach us are comparatively few ; and 
although it seems likely that the future development of man will 
be mainly concerned with the acquirement of additional sense- 
channels, no newly acquired sense will enable him to be at once 
an actor in and a spectator of the great drama presented in the 
organic world. That a creature should be able to get at the back 
of its own existence, or, in other words, to penetrate the secret of 
its own creation, is unthinkable. Outside the limited field of 
observation that immediately surrounds us extends the region 
where reason alone can guide us, and beyond lies the realm where 
reason fails and faith begins. 

H. B. GUPPY. 

November 8tA, 1905. 



LIST OF SOME OF THE PRINCIPAL AUTHORITIES 
QUOTED IN THIS VOLUME, WITH AN ENU- 
MERATION OF THE AUTHOR'S BOTANICAL 
PAPERS 



BURKILL, I. H., "The Flora of Vavau, one of the Tonga Islands," Journal of 
the Linnean Society, vol. xxxv., Botany, 1901. 

CHEESEMAN, T. F., "The Flora of Rarotonga," Transactions of the Linnean 
Society, 2nd Ser., Botany, vol. vi., part 6, 1903. 

DRAKE DEL CASTILLO, E., "Flore de la Polynesie Franchise," Paris, 1893. 

" Remarques sur la Flore de la Polynesie " (Memoire couronne par 
PAcademie des Sciences), Paris, 1890. 

EGGERS, BARON H. VON, " Die Manglares in Ecuador," Botanisches Central- 
blatt, No. 41, 1892. 

"Das Kustengebiet von Ecuador," Deutsche Geographische Blatter, 
heft 4, band 17, Bremen, 1894. 

EKSTAM, O., "Einige bliitenbiologische Beobachtungen auf Novaja Semlja," 
Tromso Museums Aarshefter, 18, 1895. 

" Einige bliitenbiologische Beobachtungen auf Spitzbergen," Tromso 
Museums Aarshefter, 20, 1897. 

GUPPY, H. B., " The Dispersal of Plants as illustrated by the Flora of Keeling 
Atoll," Journal of the Victoria Institute, London, 1889. 

"The Polynesians and their Plant-Names," Journal of the Victoria 
Institute, London, 1896. 

" The River Thames as an Agent in Plant-Dispersal," Journal of the 
Linnean Society, Botany, vol. xxix., 1891-93. 



xiv LIST OF PRINCIPAL AUTHORITIES QUOTED 

GUPPY, H. B. (continued}. 

" River-Temperature," part iii., Proceedings of the Royal Physical 
Society of Edinburgh, 1896. (The first two parts deal principally with the 
temperature of ponds and rivers, whilst in the last part the thermal 
conditions are discussed especially in connection with the life of aquatic 
plants.) 

" On the Postponement of the Germination of the Seeds of Aquatic 
Plants," Proceedings of the Royal Physical Society of Edinburgh, 1897. 

".On the Temperature of Springs as especially illustrated by the Wandle 
and other Tributaries of the Thames." (This paper, of which I have no copy, 
was published in the Journal of the Royal Meteorological Society, about 
1895. It throws light on the thermal conditions of plants in springs.) 

" Water- Plants and their Ways," Science Gossip, Sept., Oct., Nov., 1894. 
(The various modes of dispersal of land as well as water plants are here 
dealt with, their thermal conditions are discussed, and in the November 
number are given the results of four years' observations on the life-history 
and life-conditions of Ceratophyllum demersum.) 

" Caddis- Worms and Duckweed," Science Gossip, March, 1895. (A short 
note.) 

" Stations of Plants and Buoyancy of Seeds," Science Gossip, April and 
May, 1895. 

"Irregularity of some Cotyledons," Science Gossip, September, 1895. 
" Plants of the Black Pond, Oxshott," Science Gossip, October, 1895. 

" On the Habits of Lemna minor, L. gibba, and L. polyrrhiza," Journal of 
the Linnean Society, Botany, vol. xxx. (This paper contains the results of 
three years' systematic observations of these plants.) 

"The Distribution of Aquatic Plants and Animals," The Scottish 
Geographical Magazine, January, 1893. 

HEMSLEY, W. B., "Report on the Botany of the Challenger Expedition," 1885. 

"The Flora of the Tonga Islands," Journal of the Linnean Society,, 
Botany, vol. xxx. 

HILLEBRAND, W., "Flora of the Hawaiian Islands," Heidelberg, 1888. 
HORNE, J., "A Year in Fiji," London, 1881. 

KOLPIN RAVN, F., " Om Flydeevnen hos Froene af vore Vand-og Sump- 
planter," Botanisk Tidsskrift, 19 bind., 2 hefte, Kjobenhavn, 1894 (" On the* 
Floating Capacity of the Seeds of Aquatic and Marsh Plants "). (A resume" 
in French is appended to the paper.) 

MARTINS, CH., "Experiences sur la Persistance de la Vitalite des Graines 
flottant a la Surface de la Mer," Bull. Soc. Botanique de France tome iv., . 
1857. 



LIST OF PRINCIPAL AUTHORITIES QUOTED xv 

NADEAUD, J., " Enumeration des Plantes indigenes de 1'Ile de Tahiti," Paris, 
1873. 

PENZIG, O., " Die Fortschritte der Flora des Krakatau," Annales du Jardin 
Botanique de Buitenzorg, 2 ser., tome 3, Leide, 1902. 

PERKINS, R. C. L., "Fauna Hawaiiensis," vol. i., part iv. (Vertebrata) 
Cambridge University Press, 1903. 

REINECKE, F., "Die Flora der Samoa- Inseln," Engler's " Botanische 
Jahrbiicher," band xxv., heft v., Leipzig, 1898. 

SCHIMPER, A. F. W., " Die indo-malayische Strandflora," Jena, 1891. 
SEEM ANN, B., " Flora Vitiensis," London, 1865-73. 

SERNANDER, R., " Den Scandinaviska Vegetationens Spridnings-biologi," 
Upsala, 1901. 

THURET, G., " Experiences sur des Graines de diverses Especes plongees dans 
de 1'eau de Mer," Archives des Sciences (Phys. et Nat.) de la Bibliotheque 
Universelle, tome 47, Geneva, 1873. 

TREUB, M., " Notice sur la nouvelle Flore de Krakatau," Annales du Jardin 
Botanique de Buitenzorg, 1888. 



Note. Amongst the works quoted which are not specially particularised in the 
text are Scott Elliot's "Nature Studies," 1902, and Seal's "Seed 
Dispersal," Boston, 1900. 



CONTENTS 



PREFACE Pages vii x 

LIST OF SOME OF THE PRINCIPAL AUTHORITIES QUOTED, WITH AN ENU- 
MERATION OF THE AUTHOR'S BOTANICAL PAPERS . . . Pages xiii xv 

LIST OF ILLUSTRATIONS Page xxvii 

ADDITIONS AND CORRECTIONS Page xxviii 



CHAPTER I 

INTRODUCTION 

The study of insular floras. Their investigation in this work from the stand- 
point of dispersal. The significance of plant-distribution in the Pacific. 
The problems connected with the mountain-flora of Hawaii. The per- 
sistence 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. 

Pages i ii 

CHAPTER II 

THE FLORAS OF THE PACIFIC ISLANDS FROM THE STANDPOINT OF DISPERSAL 

BY CURRENTS 

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. 

Pages 12 22 
b 



xviii CONTENTS 

CHAPTER III 

THE LESSON OF THE BRITISH FLORA 

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. 

Pages 23 30 

CHAPTER IV 

THE LESSON OF THE BRITISH FLORA (continued} 

The choice of station of the water-side plant possessing buoyant seeds or seed- 
vessels. Determined by its fitness or unfitness for living in physiologically 
dry stations. In the internal organisation of a plant lies the first de- 
termining 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 Pages 31 39 

CHAPTER V 

THE FIJIAN STRAND-FLORA 

The inland extension of the beach-plants. The grouping of the coast-plants. 
Their modes of dispersal. The zone of change. Summary. Pages 40 46 

CHAPTER VI 

THE TAHITIAN STRAND-FLORA 

(From materials supplied mainly by the work of Drake del Castillo] 

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 Pages 47 50 

CHAPTER VII 

THE HAWAIIAN STRAND-FLORA 

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 Pages 51 60 



CONTENTS xix 

CHAPTER VIII 

THE LITTORAL PLANTS AND THE CURRENTS OF THE PACIFIC 

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 Pages 61 75 

CHAPTER IX 
THE GERMINATION OF FLOATING SEEDS 

Germination in the floating seed-drift of tropical estuaries. A strain of vivipary. 
Abortive germination of seeds in warm seas. A barrier to plant dis- 
persal. The borderland of vivipary. Summary Pages 7687 

CHAPTER X 

THE RELATION OF THE BUOYANCY OF SEEDS AND SEEDVESSELS TO THE 
DENSITY OF SEA-WATER 

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 Pages 8898 

CHAPTER XI 

ADAPTATION AND MEANS OF DISPERSAL 

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. 

Pages 99 103 
b 2 



xx CONTENTS 



CHAPTER XII 

THE CAUSES OF THE BUOYANCY OF SEEDS AND FRUITS OF LITTORAL PLANTS, 
WITH ESPECIAL REFERENCE TO THOSE OF THE PACIFIC ISLANDS 

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 Pages 104 118 



CHAPTER XIII 

ADAPTATION AND SEED-BUOYANCY 

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. 

Pages 119 129 



CHAPTER XIV 

THE RELATION BETWEEN LITTORAL AND INLAND PLANTS 

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. 
Scaevola. Morinda. Calophyllum. Colubrina. Tacca. Vigna. 
Premna Pages 130139 



CHAPTER XV 

THE RELATION BETWEEN LITTORAL AND INLAND PLANTS (continued] 

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. 

Pages 140 154 



CONTENTS xxi 

CHAPTER XVI 

THE RELATION BETWEEN LITTORAL AND INLAND PLANTS (continued} 

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 Columba2 or extinct Struthious birds. 
Barringtonia. Guettarda. Eugenia. Drymispermum. Acacia laurifolia. 
Conclusions to be drawn from the discussion. Summary of Chapters 
XIV., XV., XVI Pages 155 169 

CHAPTER XVII 

THE STORIES OF AFZELIA BIJUGA, ENTADA SCANDENS, AND C^ESALPINIA 

BONDUCELLA 

i 

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. Caesalpinia 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 . . . Pages 170 197 

CHAPTER XVIII 

THE ENIGMAS OF THE LEGUMINOS^E OF THE PACIFIC ISLANDS 

Leguminosae predominate in tropical littoral floras. The anomalies of their 
distribution in the Pacific islands. They conform to no one rule of dis- 
persal or of distribution. Strangers to their stations. The American home 
of most of the Leguminous littoral plants. Summary . . Pages 198 203 

CHAPTER XIX 
THE INLAND PLANTS OF THE PACIFIC ISLANDS 

PRELIMINARY COMPARISON OF THE PHYSICAL CONDITIONS OF HAWAII, 

FIJI, AND TAHITI 

Introductory remarks. The tranquil working of the winds and currents con- 
trasted 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 Pages 204 219 



xxii CONTENTS 

CHAPTER XX 
THE ERAS IN THE FLORAL HISTORY OF THE PACIFIC ISLANDS 

THE AGE OF FERNS 

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 Pages 220 230 

CHAPTER XXI 

THE ERAS OF THE FLOWERING PLANTS 
THE ERA OF THE ENDEMIC GENERA 

THE AGE OF COMPOSITE 

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 Compositns. 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 Compositae 
antedates the emergence of the island-groups of the Fijian region at the 
close of the Tertiary period. Summary Pages 231 249 



CHAPTER XXII 
THE ERA OF THE ENDEMIC GENERA (continued] 

THE AGE OF THE TREE-LOBELIAS 

The distribution of the arborescent Lobeliaceae. On the upper flanks of Ruwen- 
zori. The Lobeliaceae of the Hawaiian Islands. The Lobeliaceas of the 
Tahitian or East Polynesian region. The capacities for dispersal. The 
explanation of the absence of the early Lobeliaceae from West Polynesia. 
The other Hawaiian endemic genera. The Fijian endemic genera. 
Summary Pages 250267 



CONTENTS xxiii 

CHAPTER XXIII 
THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS 

THE MOUNTAIN FLORAS OF THE PACIFIC ISLANDS AS ILLUSTRATED BY 
THE NON-ENDEMIC GENERA 

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. 
Acaena, 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. 

Pages 268288 

CHAPTER XXIV 

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS 

(continued} 
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 Coniferae. Dammara, Podocarpus, Dacrydium. 
Not belonging to the present era of dispersal. The age of dispersal of the 
Coniferae in the Pacific. Earlier than the age of Compositae and Lobeliaceae. 
The first in the Mesozoic period. The last in the Tertiary period. 
Summary Pages 289 306 



CHAPTER XXV 

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS 

(continued) 

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 AGE OF WIDE DISPERSAL OVER THE TROPICAL PACIFIC 

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

Pages 307332 



xxiv CONTENTS 



CHAPTER XXVI 

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS 

(continued} 

THE AGE OF MALAYAN PLANTS (continued} 
THE AGE OF WIDE DISPERSAL OVER THE TROPICAL PACIFIC (continued} 

The widely dispersed genera that are as a rule not entirely represented by 
endemic species in any archipelago. Elaeocarpus. Dodonsea. Metro- 
sideros. 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. Boer- 
haavia. Polygonum. Pipturus. Dianella. Summary . Pages 333 358 



CHAPTER XXVII 

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS 

(continued} 
THE AGE OF MALAYAN PLANTS (continued} 

THE AGE OF LOCAL DISPERSAL 
Synopsis of the Chapter given on page 359 Pages 359410 

CHAPTER XXVIII 

THE POLYNESIAN AND HIS PLANTS 

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, Leucaena 
Forsteri. Mussasnda frondosa, Luffa insularum. Summary . Pages 411 428 



CHAPTER XXIX 

BEACH AND RIVER DRIFT 

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. Rutl- 
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 Pages 429439 



CONTENTS xxv 

CHAPTER XXX 

THE VIVIPAROUS MANGROVES OF FIJI 

RHIZOPHORA AND BRUGUIERA 

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 dis- 
persal. Peculiar method of fertilisation. Length of period between 
fertilisation and the detachment of the seedling. Mode of detachment of 
the seedling. Summary Pages 440467 



CHAPTER XXXI 



A CHAPTER ON VIVIPARY 

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. 

Pages 468473 



CHAPTER XXXII 

THE WEST COAST OF SOUTH AMERICA 

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 man- 
groves. Evidence of ancient coral reefs on the coast of Peru. The shore 
plants and stranded seed-drift of the Panama Isthmus. Summary. 

Pages 474 501 



xxvi CONTENTS 

CHAPTER XXXIII 
SEED-DISPERSAL AND GEOLOGICAL TIME 

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 Pages 502 514 

CHAPTER XXXIV 
r GENERAL ARGUMENT AND CONCLUSION Pages 515523 

APPENDIX Pages 525605 



LIST OF ILLUSTRATIONS 

PLATE. 
The Fijian species of Rhizophora Frontispiece. 



FIGURES. 

TO FACE PAGE 

Diagrams illustrating some of the causes of seed-buoyancy .... in 

Figures illustrating the development of the seed and the germinating 

process of Rhizophora and Bruguiera 452 453 

Diagrams illustrating the structure of the growing seeds of 

Barringtonia 574 

Diagram illustrating the prevailing cloud-formations of Mauna Loa 585 



MAPS. 

Oceania 12 

The Ocean Currents 61 

Trade routes of the Pacific Ocean (intended to illustrate the 

distances traversed by floating seeds in that ocean) 66 

The West Coast of South America 474 

Rough plan of the Gulf of Guayaquil 484 



ADDITIONS AND CORRECTIONS 



Page 5 and subsequent pages. For Ipomea read Ipomoea. 

,, 68. For Hippomanes read Hippomane. 

,, 68. For Conocarpus erecta read Conocarpus erectus. 

,, 122. Sir W. Buller includes the fruits of the Puriri tree (Vitex littoralis, according 
to Kirk) amongst the food of the New Zealand fruit-pigeons. 

,, 177. For Entata, in the head-line, read Entada. 

,, 266. The fruits of Oncocarpus vitiensis have been found in the crop of a Fijian 
fruit-pigeon (Carpophaga latrans). See Hemsley's Bot. Chall. Exped., Introd., 
46, and iv. 308 ; also Newton's Dictionary of Birds, p. 724. 

,, 368. Sernander (p. 185) observes that the fruits of Naias marina have little or 
no floating power. 

,, 416. For the first eight lines read as follows : " Of these, 22 occur in Continental 
regions on both sides of the Pacific ; 12 are found in the Old World alone ; one 
is peculiarly American, and two are confined to the Australian and Polynesian 
regions. A few of these can be regarded as exclusively American in their 
origin, though the bulk of them hail evidently in the first place from the Old 
World. But from the circumstance that all or most of the other species of the 
genus concerned are confined to America, it may legitimately be inferred that 
Waltheria americana, Ageratum conyzoides, and Physalis angulata are American- 
born species. Teucrium inflatum is a peculiar instance of an American weed 
collected in Polynesia before apparently it had been recorded from the Old 
World." 

,, 417. Add after Cardiospermum halicacabum "Its seeds, as my experi- 
ments show, possess little or no capacity for dispersal by currents, since they 
sink at once or within a few days, even after drying for months." 

,, 455. Omit the reference to figure 6 in the centre of the page. 

,, 498. For Conocarpus erecta read Conocarpus erectus. 

,, 498. For Hippomanes read Hippomane. 

,, 508. Amongst my Solomon Island collections identified at Kew were the fruits of 
a species of Litsea from the crop of a fruit-pigeon (Hemsley's Bot. Chall. 
Exped., IV. 295. 

j 533- For Commelyne read Commelina. 

,, 539. At foot of page, for Thames sea-drift, read Thames seed-drift. 

,, 581. For Crambe maritimum raz^Crambe maritima. 

,, 618. Under Mascarene Islands add Myoporum to the plants linking them to the 
Pacific Islands. 



OBSERVATIONS OF A NATURALIST 
IN THE PACIFIC 



CHAPTER I 

INTRODUCTION 

The study of insular floras. Their investigation in this work from the stand- 
point of dispersal. The significance of plant-distribution in the Pacific. 
The problems connected with the mountain-flora of Hawaii. The per- 
sistence 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. 

To proceed from the general to the special is the only method 
of dealing with insular floras. A broad and comprehensive grasp 
of plant-distribution, such as is only acquired by a life-time of 
research aided by travel and the handling of large collections, is a 
necessary foundation for the study ; yet in the nature of things 
such qualifications can be possessed by but a few. To direct an 
inquiry in the opposite direction, and endeavour to attack the 
problem of continental floras through the insular floras would 
result merely in the investigation of a few of the many questions 
connected with plant-distribution. 

The panoramic sketch of the surveyor on the mountain-top 
aids him in a thousand ways when after months of tedious labour 
he plots the details in his chart. Without such a panoramic view 
of the plant-world in his mind's eye, an observer like myself can 
only look for guidance to the writings of those who have 
VOL. II B 



2 A NATURALIST IN THE PACIFIC CHAR 

generalised on the foundations of a far broader experience, such as 
those of Bentham, De Candolle, Gray, Hooker, Schimper, and 
others. 

It would be quite possible for a botanist possessing a profound 
general acquaintance with the plant-world to dispense altogether 
with actual observation arid experiment on modes of dispersal. It 
would be quite possible for him to arrive at conclusions, which, 
even if they did not always come into line with results of obser- 
vation and experiment, we should be compelled to prefer. It is 
only from his more elevated position that a general can follow the 
course of a battle ; whilst the private with his experience confined 
to a limited area of the field of conflict may form the most 
erroneous ideas of the progress of the fight. So it is with 
observers whose employment it is to struggle with the details and 
secondary principles of plant-distribution, and so it is with the 
generaliser who has already roughly mapped out the principal 
features of the main problem. 

When Mr. Bentham in 1869, remarking on the paucity of 
species common to tropical Asia and America, characterised them 
either as plants wholly or partially maritime and spread by the 
currents, or as weeds dispersed by cultivation over the warm 
regions of the globe, he mentioned amongst the plants in the 
former category, Gyrocarpus jacquini. This tree presents one of 
the mysteries connected with the Pacific islands ; and I don't 
imagine that this eminent botanist could have known anything 
except inferentially as regards the mode of dispersal of its fruits. 
Yet experiment shows how well founded the inference was, whilst 
behind it lay a life-time of botanical research. 

The author thus approaches the subject of the floras of the' 
Pacific islands rather as a plotter of detail than as a delineator of 
great designs. However much we may study the means of 
dispersal, we have behind them the great facts of distribution, 
serving like the main stations of a trigonometrical survey, and with 
these we have to make our lesser facts and observations square. 
One is conscious all the time that much of what seems new in 
one's researches has already been foreseen by the generaliser, and 
that one can do little else than assist in confirming some of his 
results. This is all that I can lay claim to in this work. 

The floras of the islands and coasts of the tropical Pacific are 
here regarded entirely from the standpoint of plant-dispersal. The 
fruits and seeds rather than the flowers have been the subject of 
my investigations ; and although there is much to please the eye 



i INTRODUCTION 3 

in the flora of a Pacific island, it was always with a sense of 
disappointment that I turned away from some pretty flowering 
plant that failed to present me with its seed. Amongst the 
wonders of the plant-world rank the Tree Lobelias of the 
Hawaiian Islands ; yet their greatest charm to me lay not so much 
in their giant-flowers and their arborescent habit as in the mystery 
surrounding" the home of their birth and their mode of arrival in 

o 

these islands. When I first stood under the shade of the lofty 
Dammara vitiensis, the Kauri Pine of Fiji, all my interest lay in 
its cones lying on the ground ; and I remember how eagerly I 
handled my first specimen, and how anxiously I watched its 
behaviour when experimenting on its capacity for different modes 
of transport. When a strange plant presented itself on a beach, 
my first care was to ascertain the fitness of its fruits or seeds for 
transport by the currents ; and all inland plants with fruits likely 
to attract frugivorous birds were at once invested with a special 
interest for me. 

The mangrove swamps were always great places of interest, and 
months of my sojourn in the Pacific must have been passed in 
exploring their creeks and in examining their vegetation. Botanists 
usually avoid these regions ; but the observation of the germination 
of the Rhizophora fruits on the trees and the inquiries connected 
with their methods of distribution over the oceans were pursuits so 
engrossing that I ignored the numerous discomforts connected with 
the exploration of these gloomy regions. The magnificent man- 
grove forests of the Ecuador coast of the Pacific will live longest 
in my memory, though the risks were considerably greater and the 
discomfort of existence extreme. But the mangrove swamps 
present us with glimpses into the conditions of plant life during 
the warmer epochs of the earth's history, when perhaps the seed- 
stage was largely dispensed with, whilst an atmosphere, laden 
with moisture and screening off much of the sun's light, enveloped 
most of the circumference of the globe. 

The plant world viewed only from the standpoint of dispersal 
may lack much that is pleasing to the eye, though it abounds with 
small and great problems fascinating to the reason. Matters of 
great moment are here involved, and in the case of the Pacific 
islands they concern not only the source of the oceanic floras, 
but the story of the islands themselves ; whilst behind these there 
rise up questions of yet deeper import, questions that are bound up 
with the beginnings of genera and species, and with other mysteries 
of life on the earth. The distribution of plants presents something 

B 2 



4 A NATURALIST IN THE PACIFIC CHAP. 

more than a problem of means of dispersal, or a problem ofu- 
station, or a problem of plant migration connected with climatic 
changes. It is something a great deal more than all three, 
since it is indissolubly connected with a past, of which unfortun- 
ately we know very little. Let us take it to be a question of 
means of dispersal, and then in imagination transporting ourselves 
to the Scandinavian coast, let us gather up the stranded West 
Indian beans of Csesalpinia, Mucuna, and Entada, that have been 
drifted there for ages by the Gulf Stream, and lie in some cases 
semifossilised in the adjacent peat-bog. Was ever dispersal so 
utterly purposeless as this ? Yet here lies a principle of plant- 
dispersal that is fundamental. We see it in the thistle-seed floating 
seaward in the wind. Nature never intended its pappus for such 
an end. It was formed for quite another purpose, yet it aids 
largely the dispersion of the plant. What can be more significant 
than that ? 

Or let us take it to be a matter of station. Given time and the 
recurrence of the same conditions, with others I once imagined that 
we could explain most things in plant-distribution, whether of 
plants at the coast or of plants inland, whether of plants of the 
alpine peaks or of plants of the plains, or of plants of the river or 
of the pond. Time, it was held, had long since discounted the 
means of dispersal, and distribution became merely an affair of 
station. But the supplanting of many indigenous species of a flora 
by introduced species is a common story in the plant-world ; and 
such a view needs no further discussion here. Nor is distribution 
only concerned with plant-migration. Any theory of the origin of 
alpine floras on tropical mountains will have to explain the pre- 
sence of the temperate genera, Geranium and Sanicula, not alone on 
the summits of the mountains of Equatorial Africa and Madagascar, 
but on the uplands of Hawaii in mid-Pacific, where also are found 
Ranunculus, Vaccinium, Fragaria chilensis (the Chilian strawberry), 
and Drosera longifolia. 

Taking genera of different stations each in their turn, and fol- 
lowing up the clues thus afforded, it would be possible to find 
support for all the reputable views relating to plant-distribution. 
The wide range of aquatic plants under conditions that completely 
change the character of the terrestrial vegetation, such, for in- 
stance, as Myriophyllum and Ceratophyllum, might be plausibly 
attributed to the relative uniformity of the conditions of aquatic 
life both in time as well as space. The occurrence of Vaccinium 
on mountain-tops over most of the world, even on the highlands 



i INTRODUCTION 5 

of Samoa, Tahiti, and Hawaii in the Pacific Ocean, would be rightly 
regarded as evidence of active dispersal of the seeds through the 
agency of birds from one mountain-summit to another, whether in 
mid-ocean or in the centre of a continent. The prevalence of the 
same beach-plants over most of the globe in the same climatic 
zones would point unmistakably to the predominant agency of 
currents. But with many plant-genera, some of which range the 
world, whilst others again may be restricted to a single group 
of islands in the Pacific, there is often no question either of 
means of dispersal, or of station, or of plant-migration, and 
problems of a very different nature are opened up. 

When we leave the beach and the mountain-top, the river and 
the pond, all the troubles of distribution begin ; and since but a 
smairproportion of plants in a typical flora belong to these stations, 
it follows that difficulties will dog our steps with the large majority 
of the plants. The agencies of dispersal now working around us, 
the current, the wind, the insect, the bird, and the bat, will explain 
many of the features of littoral and alpine floras and of the vegeta- 
tion of ponds and rivers. Here we have in so many cases wide- 
ranging genera with the means of dispersal ready to hand. We 
can connect the wide range of Vaccinium with the wide range of 
birds of the grouse and other families that feed on the berries. 
We can associate the great areas of aquatic or sub-aquatic genera, 
like Potamogeton and Sparganium, with the migratory habits of 
the ducks in the stomachs of which we find their seeds. We can 
connect the great ranges of beach plants like Ipomea pes caprae 
in the tropics, and Convolvulus soldanella in the temperate regions 
with the currents, and the almost cosmopolitan range of many 
ferns and lycopods with the winds and other agencies. 

When, however, we enter the forests we find genera that are 
often much more restricted in their areas, and species that are yet 
more limited in their range. There is very little dispersal going 
on here. The birds are strange. Their distribution is usually 
very local. They look lazily down at us from the branches, as 
they disgorge the seeds and stones of the fruits they have eaten, 
which cover the ground around. We can almost fancy that they 
say : " Our work is done. We rest from the toil of our ancestors. 
They carried seeds to far-distant Hawaii, Tahiti, and Savaii. Our 
work is done." And as we walk through those noiseless forests, 
where the machinery of species-making is ever in silent motion, 
we become aware that we are treading one of Nature's great work- 
shops for the manufacture of species and genera. Outside the 



6 A NATURALIST IN THE PACIFIC CHAP. 

forest all is bustle and hurry. We are in the streets, or rather in 
the distributing areas of the plant-world. We hear the noise of 
the breaker, the roar of the gale, the cry of the sea-gull, the 
flapping of a myriad pairs of wings of some migrating host over- 
head, and we know that the current, the wind, and the bird are 
actively at work ; but their operations are confined mainly to the 
beach, the mountain-top, the river, and the pond. ' 

Let us take a well-wooded Pacific island several thousand feet 
in height. We find on its beaches the same littoral plants that 
we have seen before on the tropical shores of Malaya, of Asia, 
of Africa, and of America. We find in its ponds and rivers the 
same species of water-plants, such as Ceratophyllum demersum, 
Ruppia maritima, and Naias marina, that are familiar to us in the 
cool and tepid waters of much of the globe. On its level summit, 
if it remains within the clouds we find in the boggy ground, where 
Sphagnum thrives, genera that are represented in Fuegia, New 
Zealand, and the Antarctic islands, such as Acaena, Lagenophora, 
and Astelia, and the world-ranging Drosera longifolia. In other 
elevated localities we find Ranunculus, Geranium, Sanicula, Arte- 
misia, Vaccinium, and Plantago, chiefly genera of the temperate 
regions of the northern hemisphere ; whilst there are also found 
Gunnera, Nertera, and Uncinia, all hailing from the south and 
belonging to the Antarctic flora characterising all the land-area 
around the globe in the latitude of New Zealand and Fuegia. 
The Hawaiian species of Nertera and of Uncinia occur also in 
New Zealand, and the first-named is found also in Tristan da 
Cunha and in South America. In the Hawaiian uplands there 
is also to be seen Deyeuxia, a genus of grasses found in the 
Tibetan highlands and in the Bolivian Andes at elevations of 
16,000 to 19,000 feet; and the same species that exists in 
Australia may be found in the mountains of Hawaii. Here^ 
also, both in Hawaii and Tahiti, occurs Luzula campestris. 

In making the foregoing remarks on the alpine plants of a 
Pacific island, I have had Hawaii in my mind, but we find the 
elements of a similar widely-distributed mountain-flora in the less 
lofty peaks of Tahiti and Samoa, and traces even in Fiji, where 
the mountains, however, have only a moderate elevation. But the 
point I wish to lay stress on is the cosmopolitan yet temperate 
character of the mountain-flora of an island lying in the midst of 
the tropical Pacific. As he shifts his station on this mountain- 
summit, the observer might at different times imagine himself in 
the Sierra Nevada of California, on a Mexican tableland, on a peak 



i INTRODUCTION 7 

of the Andes, or in the lowlands of Fuegia. Other plants that I 
have not mentioned, such as Coprosma, would bring back to him 
New Zealand. He might even be on a mountain-top in Central 
Africa, or on a Madagascar plateau ; whilst in the boggy region of 
an elevated Hawaiian tableland he would meet with not only the 
physical conditions, but also several of the plants found on the 
higher levels of Tristan da Cunha. 

It is, however, to be noted that although these mountain-tops 
in the mid-Pacific have been stocked with genera from the four 
quarters of the compass, the species as a rule are restricted to that 
particular archipelago. Whilst the beach and the river in most 
cases possess plants that have very wide ranges over the earth, a 
good proportion of the species on the mountain-summit are not 
found elsewhere. This implies a partial suspension of the meansU 
of dispersal on the mountain-top, whilst the currents and waterfowl ' 
are still actively distributing the seeds of the littoral tree and of 
the aquatic plant. We here get a foreshadowing of another great 
principle, or of another line along which Nature has worked in 
stocking these islands of the Pacific with their plants, a subject 
concerning which much will be said in later pages. 

Hitherto, we have dealt only with a small proportion of the 
flora, and with but a small portion of the area of the island. We 
have yet to deal with the intermediate region between the sea- 
border and the summit of the island, or, in other words, with 
the forested mountain slopes. This is the home of many of the 
peculiar species and peculiar genera, both of plants and birds ; and 
it is with this zone that we shall be mainly concerned when 
we come to contrast the floras of the several archipelagoes of the 
tropical Pacific. Here the agencies of dispersal have, to a large 
extent, ceased to act ; and the question will arise as to the connec- 
tion between the endemic character of the plants and the endemic *" 
character of the birds. We shall have to ask why this island, after 
receiving so many plants, ceased to be centres of dispersal to other 
regions. It is possible that these seeds or fruits have lost their 
capacity for dispersal ; but only a few instances of this change 
present themselves. Rather it may be supposed that the birds 
that originally brought the seeds to the island came to stay ; and 
this at once suggests another query as to the cause of the change 
of habit. I am alluding here not to the plants with minute seeds, 
such as Sagina and Orchis, which Mr. Wallace, in his Darwinism, 
regards as capable of being transported by strong winds over 
a thousand miles of sea ; but to those numerous plants found in 



8 A NATURALIST IN THE PACIFIC CHAP. 

the Fijian, Tahitian, and Hawaiian forests, where the seeds and 
" stones " are large and heavy, measuring often as much as a 
quarter of an inch (6 mm.), and sometimes nearly an inch (25 mm.) 
in size. The reader will be surprised to learn how little " size " has 
determined the distribution of seeds and fruits in the Pacific. He 
will have to appeal to the habits of pebble-swallowing of the Dodo, 
the Solitaire, the Goura pigeon, the Nicobar pigeon, &c,, if he 
desires to find a parallel in the habits of birds. 

It is here assumed that the reader is already acquainted with 
the principles involved in a discussion of island-floras, principles 
clearly laid down in the writings of Hooker, Wallace, Hemsley> 
and others. As a general rule in an island or in a group of islands 
where there are a large number of plants not found elsewhere, 
there is also a large endemic element in the avifauna, and where 
none of the plants are peculiar, endemic birds are either few 
or wanting. As an example of the first we may mention Hawaii, 
and Iceland affords an instance of the second. But there is no 
hard and fast rule connecting the endemic character of the plants w 
and birds of an island with its distance from other regions. Even 
the small group of Fernando Noronha, lying only some 200 miles 
off the coast of Brazil, possesses its peculiar birds and its peculiar 
plants ; and we can there witness the singular spectacle, as 
described by Mr. Ridley, of an endemic bird, a frugivorous dove, 
engaged in scattering the seeds of endemic plants over the little 
group. This is the only fruit-eating bird in the islands, remarks 
the same botanist in the Journal of the Linnean Society (vol. 27, 
1891); and "when one sees the number of endemic species with 
edible fruits, one is tempted to wonder if it were possible that they 
were all introduced by this single species of dove, or whether other 
frugivorous birds may not at times have wandered to these shores." 
This inter-island dispersal in a particular group of peculiar plants 
by peculiar birds is a common spectacle in the Pacific. The con- 
trast between the large number of plant-genera possessing fruits 
that would be dispersed by frugivorous birds and the poverty of 
fruit-eating birds in the avifauna is well displayed in Hawaii. 

The island of St. Helena would seem to offer an exception 
to the rule that endemic birds and endemic plants go together, 
since, though its flora possesses a very large endemic element, 
there are scarcely any endemic or even indigenous birds recorded 
from the island. We can never know, however, how much of the 
original fauna disappeared with the destruction of the forests. It 
would nevertheless appear that but few of the genera possessing 



i INTRODUCTION 9 

peculiar species of plants were adapted for dispersal by frugivorous 
birds. The lesson to be learned from this island concerns the 
Compositae, often arboreous, that constitute the principal feature of 
its flora. St. Helena retains almost more than any other island 
evidence of the age of Compositae which has left its impress on 
many insular floras ; and when we discuss the original modes 
of dispersal of the endemic Hawaiian genera of the same order we 
shall look to the flora of this Atlantic island for assistance in the 
matter. To the age of Compositae belong the beginnings of 
several insular floras. 

To return to the main line of our argument, it would seem 
that in a Pacific island there is a constant relation between free 
means of dispersal and the preservation of specific characters. The 
ocean-current and the aquatic bird are in our own time actively 
engaged in dispersing the seeds of shore-plants and water-plants, 
and we see the same species ranging over the world. On the 
other hand on the mountain-top the agencies of dispersal are 
beginning to fail, and as a result many a mountain has some of its 
species restricted to its higher regions. In the forest zone there 
has been a more or less complete suspension of the activity of the 
dispersing agencies, and new genera are formed whilst peculiar 
species abound. Free means of communication with other regions 
restrains but does not arrest the differentiating process that is ever 
in progress throughout the organic world. Isolation within certain 
limits gives it play. 

It is in this connection interesting to reflect that during the 
differentiation of the inland flora the littoral plants have lagged 
behind or have remained relatively unchanged. The currents have 
been working without a break throughout the ages ; and the 
cosmopolitan Ipomea, that now creeps over the sand of the beach, 
or the wide-ranging Rhizophora, that forms the mangroves of the 
coast-swamp, must have witnessed the arrival of the ancestors of 
several of the endemic inland genera. The swamp-plants of the 
littoral flora are probably older, however, than the beach-plants 
which have been recruited from time to time in one region or 
another of the tropics from the inland flora. Yet as a body the 
littoral plants have lagged far behind the inland flora. We might 
thus expect that in a Pacific island, excluding the wind-distributed 
plants, such as the ferns and the lycopods, the most ancient typesv 
of the plants would be found at the coast, the most modern in the 
forests, whilst the plants of the mountain-summit would represent 
an intermediate age. 



io A NATURALIST IN THE PACIFIC CHAP. 

But true as this may be, the composition of a strand-flora is a 
very complex one. Although, as Prof. Schimper remarks, the 
mangrove formation is more isolated than the beach formation, and 
affords evidence of a much earlier separation, the beach-plants as a l> 
body are anything but homogeneous in their character. Their 
physiognomy varies to some extent with the alteration in the 
characters of the inland flora, changes to which the mangrove 
formation makes a very slow response. Yet amongst the plants of 
the beach we find strangely assorted forms that are as ancient 
denizens of the coast as the mangroves themselves. Take, for 
instance, Salsola Kali, that thrives alike on a beach in Chile, on the 
sea-shore in Devonshire, and in the salt-marshes of the interior of 
Tibet. Then, again, there is a type of littoral plant, of which 
Armeria vulgaris and Plantago maritima may be taken as examples, 
which is equally at home on the beach and on the tops of inland 
mountains. We might in a sense apply the wrecker's motto, 

" What the sea sends and the land lends," 

to the history of a littoral flora. Yet on the other hand the inland 
flora in its turn receives a few recruits from the littoral flora ; and 
it is the relation between the inland and coast species of the same 
genus that offers one of the most fascinating studies in the botany 
of the Pacific Islands. 

This introductory chapter may be concluded with a few 
remarks on what may be termed " the ethics of plant-dispersal." 
Not that this is in any way a suitable phrase, but it best expresses 
my sense of the lack of propriety in some things connected with 
this subject. It is odd, for instance, that we speak of the dispersal 
of plants and animals in the same breath, as if the process was in 
both cases identical. Seeing that from this point of view we judge 
a plant only by its seeds and fruits, it is apparent that we are 
following quite a different method than that which we employ in 
the study of the dispersal of animals. Whilst the zoologist 
classifies the units of dispersal, the botanist does nothing of the 
kind ; and the two systems of classification are at the outset 
fundamentally distinct. The student of plant-dispersal thus often 
finds himself placed in an awkward dilemma. For him a family is 
-a collection of allied genera having similar seeds or fruits and 
fitted often for the same mode of dispersal. A family like 
Sterculiaceae, possessing such a variety of seeds and fruits suitable 
for very different modes of dispersal, is from his standpoint a 
collection of dissimilar units. Genera like Commersonia, 



INTRODUCTION n 

Waltheria, Kleinhovia, Sterculia, and Heritiera, that he so often 
meets with in the Pacific Islands, have in these respects frequently 
very little in common ; and yet one of the earliest determining 
influences in plant-life must have lain in the capacity for dispersal. 

Yet chance seems to reign in the processes of plant-dispersal - 
ever going on around us. In the floating seed, in the achene with 
its light pappus blown before the gale, in the prickly mericarp 
entangled in the plumage of a bird, in the " stone " of the drupe 
disgorged or ejected by the pigeon, in the small grain that becomes 
adhesive in the rain, in the tiny rush-seed enclosed in the dried 
pond-mud on the legs of some migratory bird, in all these we see 
the agencies of dispersal making use of qualities and of structures 
that were developed in quite another connection and for quite 
another purpose. That such characters have been so to speak 
appropriated by these agencies is a pure accident in a plant's life- 
history. If the evolutionary force had been in operation here, it 
would have selected some common ground to work on. There 
would have been some uniformity in its methods, whereas the 
modes of dispersal are infinite. The qualities and characters that 
happen to be connected with dispersal belong to a plant's develop- 
ment in a particular environment. They can never have been 
adapted to another set of conditions that lie quite outside that 
environment. There is a relation of a kind between the specific 
weight of wood and the density of water, and this, in a sense, sums 
up the connection between a seed and its distributing agencies. 

Evolution has never concerned itself directly with means of 
dispersal. Evolution and Adaptation represent the dual forces 
that rule the organic world, the first an intruding force, the last a 
passive power representing the laws governing the inorganic world. 
To these laws the intruding power has often been compelled to 
bend, and it has had to pay its price, and sometimes it has 
succumbed, and sometimes it has turned its defeat into a victory. 
Nature, so watchful over the young plant, as represented by the 
seed, is finally compelled to let it go, and dispersal begins where 
evolution ends, or rather when the evolutionary power fails. The 
seed-stage itself is the price of adaptation. The death of the 
individual may also be regarded from the same standpoint. It 
represents a defeat of the evolutionary force, which, however, has 
been retrieved by the gift of reproductive power. 



CHAPTER II 

THE FLORAS OF THE PACIFIC ISLANDS FROM THE STANDPOINT 
OF DISPERSAL BY CURRENTS 

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. 

IN the previous introductory chapter some of the numerous 
questions affecting insular floras were briefly referred to. I will 
now ask my reader, if he has had the patience to read it, to con- 
sign that chapter for the time at least into oblivion, and to proceed 
with me to our Pacific island with the intention of investigating 
its flora from the standpoint of dispersal. We will together take 
up the subject de novo, after banishing from our minds all 
preconceptions that we may have possessed. 

After having been over the island gathering specimens of all 
the seeds and fruits, we return to our abode on the beach. But we 
are puzzled where to begin. The problem presents itself as a 
tangled skein, and our difficulty is to find an " end " that we can 
follow along with some chances of success. In our trouble we 
look around us ; and at that moment we see a number of floating 
seeds and fruits carried by the current past the beach. This 
presents us with a clue and our investigation begins. 

We place all our seeds and fruits in a bucket of sea-water and 
notice that many of them sink at once. In a few days we look 
again and observe that many more are at the bottom of the bucket, 
only a small percentage remaining afloat. We then remark to our 
surprise that nearly all of the floating seeds and fruits belong to 
coast plants, those of the inland plants, which indeed make up the 
great bulk of the flora, having, as a rule, little or no buoyancy. 
After a lapse of weeks and months the seeds and fruits of the 






1 - :.:_ I. >^g <* 

fi :>] ! ; 

r o x - -T ^ 

'' /f W| s 

</ *l^'-~->. -s- | 




CH. ii THE FLORAS OF THE PACIFIC ISLANDS 13 

coast plants are found to be still afloat. In the results of this 
experiment we see the work of the ages. There has been, in fact, 
-a great sorting process, during which Nature has " located " the 
plants with buoyant seeds or seed-vessels at the sea-coast, placing 
the others inland. This is the clue that we shall follow up during 
many chapters of this book ; and having in this manner introduced 
the reader to the subject, I will now refer to the general results of 
my investigations in this direction in the Pacific Islands. 

In Fiji there are about eighty littoral plants out of a total of at 
least 900 species of indigenous flowering plants, that is to say 
about nine or ten per cent. (Note i), the littoral grasses and the 
sedges being with one or two exceptions excluded. These shore 
plants belong to the sandy beach and to the coast swamp, and 
most of them are distributed over the tropical shores of the Indian 
and Pacific Oceans, whilst not a few occur on the coasts of tropical 
America. They form the characteristic plants of the coral atoll, 
and many of them have long been known to be dispersed by the 
currents. From the list given in Note 2 it will be seen that these 
eighty species belong to about seventy genera. Nearly all of them 
(95 P er cent.) possess seeds or seed-vessels that float at first in 
sea-water ; whilst three-fourths of them (75 per cent.) will float 
unharmed for two months and usually much more, and several of 
them will be found afloat after a year or more, being still capable 
of reproducing the plant (Note 3). 

The prevalence in the Fijian strand-flora of Leguminosae, 
which are included in my list under the divisions Papilionaceae, 
Caesalpinieae, and Mimoseae, is very significant. They make up 
about 29 per cent, of the total. Excluding weeds and a few other 
introduced plants, there are some fifty species known from the 
Fijian Islands, and of these almost half belong to the littoral flora, 
which as we have seen constitutes only a fraction (one-tenth) of the 
whole flora. If we regard the genera, we find that out of some 
thirtyKLeguminous genera twenty are littoral and in most cases 
exclusively so. This conspicuous feature in the constitution of the 
strand-flora is of prime importance as concerns the question of 
adaptation to dispersal by currents, since nearly all the Leguminosae 
with buoyant seeds offer themselves as defiant exceptions to any 
such law. 

I will now contrast the Fijian inland flora with that of the 
coast from the point of view of the buoyancy of the seed or fruit, 
according as it presented itself for possible dispersal by currents. 
Rather over a hundred plants were experimented upon (Note 4). 



14 A NATURALIST IN THE PACIFIC CHAR 

After excluding some introduced plants there remain some ninety 
species belonging to about sixty genera, and of these quite 75 per 
cent, sank at once or in a few days. I may add that all kinds of 
fruits are here represented, the capsule, the achene, the coccus, the 
berry, the drupe, &c. Of the buoyant residue few possess seeds or 
fruits that will float uninjured for any length of time. Not many 
gave indications directly in opposition to the principle that whilst 
the seeds or fruits of shore-plants generally float, those of inland 
plants usually sink, since as pointed out in Note 5 most of the 
difficulties are removed during the subsequent developments of the 
principle discussed in the later pages of this work or are to be 
explained on other grounds stated in the note. 

We pass now from Fiji as typical in its flora of the Western 
Pacific to Tahiti as representing in its flora the more strictly 
oceanic groups of Eastern Polynesia. In the Tahitian region, 
which is taken as including in a general sense the Society Islands, 
the Marquesas, and the Paumotus, there are only between 50 and 
60 littoral plants, excluding the occasional additions from the 
inland flora. As indicated by the letter T preceding the species 
in the list of Fijian shore plants, nearly all are to be found in Fiji, 
and the few not yet recorded from that group, which I have 
referred to in the remarks following the list, will probably be found 
there by some subsequent investigator. In Tahiti also between 
75 and 80 per cent, of the strand plants have seeds or seed- 
vessels that float for months ; and here also Leguminosae 
predominate, forming about 30 per cent, of the total. A con- 
spicuous negative feature in the Tahitian strand-flora is concerned 
with the absence of the mangroves and their numerous associated 
plants, which together form the mangrove formation in Fiji. This 
remarkable character in the distribution of shore plants in the 
Pacific is discussed in Chapter VI. 

Not having visited Tahiti, I can only deal inferentially with the 
inland plants, as in the case of the strand-flora. Here also the 
plants are in the mass Fijian in a generic and often in a specific 
sense, and there is no reason to believe that the principle involving 
the non-buoyancy of the seeds or fruits of inland plants does not 
as a rule apply to Tahiti as well as to Fiji. 

The Hawaiian Islands, standing alone in the North Pacific, 
form a floral region in themselves, a region that is the equivalent 
not of one group in the South Pacific, such as that of Fiji or of 
Tahiti, but of the whole area comprising all the groups extending 
from Fiji to the Paumotu Archipelago. Lying as it does mainly 



ii THE FLORAS OF THE PACIFIC ISLANDS 15 

outside the zone of influence of the regular currents that would 
bring the seeds of tropical plants to its shores, Hawaii possesses a 
strand-flora that is meagre in the extreme. Not only does it lack 
the mangrove formation so characteristic of Fiji, but it lacks also 
many of the plants of the beach formation that are found both in 
Fiji and in Tahiti, plants that give a peculiar beauty to the reef- 
girt beaches all over the South Pacific. Its poverty is sufficiently 
indicated in the number of its species, thirty in all, barely more 
than half of the number found in Tahiti, and not much over a 
third of those occurring in Fiji. Though coral reefs with their 
accompanying beaches of calcareous sand are relatively scanty, the 
characteristic littoral plants have not been numerous enough to 
hold their own against intruders from the inland flora, and endemic 
species have taken a permanent place amongst the strand plants. 
The Hawaiian strand-flora has thus quite a facies of its own, and 
it will be found discussed in Chapter VII., whilst a list of the 
plants is given in Note 28. It will thus not be a matter for surprise 
that the littoral flora of Hawaii follows the principle of buoyancy 
only in a modified degree. It is true that about two-thirds of the 
species of the present beach flora possess seeds or seed-vessels that 
float for months ; but since there are reasons for believing that 
several of them are of aboriginal introduction, this proportion is 
reduced to a third. In the list of the Fijian shore plants given in 
Note 2, those occurring also in Hawaii are preceded by H. 

When we look to the Hawaiian inland flora for indications 
respecting the principle of the non-buoyancy of the seeds or seed- 
vessels of inland plants, we find that so far as it has been there 
tested this principle receives fresh support from the plants growing 
on the slopes of the Hawaiian mountains. Although the author 
was only able to sample the inland flora, we have in the list given 
in Note 6 all kinds of plants, from the forest-tree to the herb, and 
most varieties of fruits. Excluding a few introduced plants, there 
are in this list about fifty species of indigenous plants belonging to 
about forty genera. Of these plants quite 80 per cent, possess 
seeds or fruits that sink either at once or in a week or two. Of 
the " buoyant " residue very few have seeds or fruits that will float 
for months. These apparent exceptions to the principle are in 
great part capable of being explained on the grounds referred to 
in Note 5 in connection with the Fijian inland plants ; and I have 
alluded to them in Note 7. 

The littoral flora of Fiji is essentially Malayan and Asiatic, and 
for our purpose is eminently typical. Its plants are found far and 



16 A NATURALIST IN THE PACIFIC CHAP. 

wide on the tropical coasts of the Old World, and sometimes also 
in the New World. In more than half the species we are con- 
cerned with the dispersal by currents of more or less dry inde- 
hiscent fruits that range usually in size from a marble to a 
cricket-ball, as illustrated by those of Hernandia peltata and 
Barringtonia speciosa, whilst with most of the rest the currents 
distribute large seeds, several of which are Leguminous, as in the 
case of Mucuna, Caesalpinia, and Entada, with others of the Con- 
volvulus type, as in the instance of Ipomea pes caprae. It is 
remarkable that in selecting plants with buoyant seeds or seed- 
vessels for a station at the coast Nature has generally ignored 
those with very small seeds. When such small seeded plants, as 
Sesuvium portulacastrum, occur on the beach, the seeds have as a 
rule no buoyancy. Pemphis acidula is, however, an exception ; 
but its case is a very rare one. It will be established in the next 
chapter that the non-buoyancy of small seeds is generally true also 
of plants growing by the river or by the pond. 

The point at which we have arrived in our inquiry concerning the 
general collection of seeds and seed-vessels that we placed in sea- 1 
water is that the plants with buoyant seeds or seed-vessels have been for 
the most part "located" at the coast. But if we look a little more 
closely at the sunken and floating seeds, we find that in the same 
genus there are species with seeds or seed-vessels that sink and 
species with those that float. We look again and then perceive that 
the same general principle is true of different species of the same 
genus growing inland and at the coast. We learn now that as a rule 
when a genus possesses both littoral and inland species, the seeds or 
fruits of the former float in sea-water for a long time, whilst those 
of the latter have little or no floating power. But we have yet to 
examine the structure of the coverings of the buoyant seed or 
fruit ; and we shall then discover that the different behaviour in 
water is often associated with corresponding structural differences 
of a striking character. The structural causes of buoyancy are 
dealt with in Chapter XII.; and we will now content ourselves 
with enunciating the second principle that in a genus comprising 
both coast and inland species, only the coast species possess buoyant 
seeds or seed-vessels. 

The important principle above indicated was not altogether new 
to me, as is shown in the next chapter. But it was new in the case 
of the floras of the Pacific Islands. When it first presented itself in 
Hawaii I was engaged in trying to find a connection between the 
inland and littoral species of Scaevola ; and its discovery led me 



ii THE FLORAS OF THE PACIFIC ISLANDS 17 

to form a plan worthy almost of Don Quixote, namely, to cultivate 
the beach species of Ipomea, Scaevola, and Vitex in the interior 
with the hope of finding them converted into inland species 
when I returned to Hawaii after a lapse of years. Little matters 
often determine a career, and for a while my future movements and 
probably the remainder of my life were largely centred around my 
interests in the well-being of Scaevola Kcenigii. The scheme was 
actually undertaken, and I had fixed on a little plot of land at the 
foot of the mountains rising behind Punaluu in Kau. The trans- 
action was on the point of completion when the owner changed his 
mind and the plan fell through. Subsequent observation and 
reflection have led me to believe that in most cases no connection 
exists between the littoral and inland species of a genus ; and I 
have dwelt on this incident merely to show the importance that I 
rightly attached to this distinction, whilst misinterpreting its 
meaning. 

But to return to my own investigations. Had I indeed read 
more carefully Professor Schimper's work on the Malayan 
strand-flora, this subject would have been found discussed by 
an observer far abler than myself, though from a very different 
standpoint, that of Adaptation and Natural Selection. He points 
out (pp. 179 182) that with a number of these tropical genera 
possessing both littoral and inland species, such as Barringtonia, 
Calophyllum, Clerodendron, Cordia, Guettarda, and Terminalia, 
greater buoyancy of the fruits of the shore species is associated 
with certain structural characters in the fruit-coverings, whilst with 
the inland species, where the floating power of the fruits is either 
much diminished or entirely absent, these structural characters are 
either less developed or lacking altogether. 

The question of structure and the debateable matters con- 
cerned with it are treated at some length in Chapters XII. and 
XIII., and Professor Schimper's views are there given. I will 
content myself with remarking that the genus Terminalia was 
especially studied by him in this respect. He tested the buoyancy 
of the fruits of ten species, and found that the flotation period 
varied from nothing to 126 days and more. By far the best 
" floaters " were the fruits of Terminalia Katappa, the only littoral 
species tested, all the others being inland species with less buoyant 
fruits, and diminished ranges, some of the fruits sinking at once, 
whilst the others sank usually in a few days or in a few weeks. 
It was also ascertained that, although the buoyant tissue in the 
fruit-coats varied in amount generally with the floating-powers, 
VOL. II C 



1 8 A NATURALIST IN THE PACIFIC CHAP. 

it was rarely absent altogether in the inland species, a very 
significant conclusion, as will subsequently be pointed out. 

Several other striking examples of this principle came under 
my notice in the Pacific, and perhaps the most significant is that 
of Scaevola, a genus of the Goodeniaceae, confined mainly to 
Australia and the Pacific islands, but possessing also a littoral 
species, S. Kcenigii, that is found on tropical beaches all round 
the globe. It is associated in both Hawaii and Fiji with inland 
species, none of which are common to the two archipelagoes, and 
in the case of the Hawaiian species not found outside the group. 
All the species have fleshy drupes, both coast and inland plants, 
the " stone " in the littoral species possessing a thick covering of 
buoyant tissue, which is absent or but slightly developed in the 
inland species. The fruits of the shore species float for many 
months ; whilst those of the inland species experimented on by 
me (S. Chamissoniana and S. Gaudichaudii in Hawaii, and S. 
floribunda in Fiji) sank at once or within a few hours. Here we 
are only concerned with the difference of buoyancy between inland 
and littoral species. The several other questions involved con- 
cerning this genus will be dealt with later on in this work. 

The genus Morinda offers another good example of this 
principle. It includes one widely-spread littoral species (M. citri- 
folia), found not only in all the Pacific archipelagoes, but also over 
much of the tropics. It is associated in all the large groups with 
one or more inland species, some of which are endemic and others 
more generally distributed. The littoral species displays in its 
pyrenes a singular air-cavity, the nature of which is discussed in 
Chapter XII., which endows them with great floating powers. 
This cavity is not found in inland species, and the pyrenes have 
in consequence no floating power (see Note 8). 

Calophyllum Inophyllum, an Old- World littoral tree, spread far 
and wide over the Pacific islands, has very buoyant fruits. In the 
groups of the South Pacific it is associated with inland species that 
are commonly found in the forests, namely, C. spectabile and C 
Burmanni, the fruits of both of which, according to my observa- 
tions in Fiji, have limited floating powers, sinking after periods 
varying from a few days to four weeks, and lacking in great part 
the buoyant coverings of the littoral species. Professor Schimper 
obtained similar results with inland species from other regions 
(Note 9). 

The fruits of the two Fijian coast trees, Barringtonia speciosa 
and B. racemosa, possess great floating powers ; whilst those of an 



ii THE FLORAS OF THE PACIFIC ISLANDS 19 

undescribed species that I found in the mountains of Vanua Levu 
sink at once. Another Fijian inland species (B. edulis, Seem.) that 
is often planted, has fruits that float heavily for about a month. 
This difference in buoyant powers is also associated with character- 
istic differences in the structure of the fruits. It would be interest- 
ing to learn what floating capacity belongs to those of the Samoan 
endemic species (B. samoensis, Gray). Professor Schimper's obser- 
vations on the genus in the Malayan region point in the same 
direction, but more than one difficulty awaits its solution in the 
re-examination of the genus. He says, however, that B. excelsa, 
Bl., a Malayan species, sometimes cultivated and growing both 
inland and at the coast, has fruits that floated for one hundred 
days after drying (p. 173). 

A striking instance of this principle is afforded in the case of 
the two Fijian species of Tacca, the wide-ranging littoral species, 
T. pinnatifida, where the seeds float for several months, and the 
inland species, T. maculata, Seem., found also in Australia and 
Samoa, where the seeds sink at once or in a few days. The seeds 
of the shore plant owe their buoyancy to the spongy tissue in 
their coverings, which is either absent or much less developed 
in those of the inland species. This point might also be deter- 
mined for the new Samoan inland species described by Reinecke, 
the German botanist, as T. samoensis. 

Another good illustration is afforded by the two species of 
Premna of the South Pacific, though here the buoyancy of the 
" stone " of a drupe is concerned. With P. taitensis or P. integri- 
folia, a small littoral tree or shrub, these stones possess great float- 
ing-power, and are often found in the floating seed-drift of the 
Fijian estuaries and in the stranded drift of the beaches. In the 
case of Premna serratifolia, an inland tree of moderate size, the 
stones have as a rule little or no buoyancy. As shown in Note 32, 
where this genus is discussed in detail, the buoyancy is mainly due 
to empty seed-cavities. 

Other instances might be given in illustration of this principle ; 
but it will have been noticed that already many of the familiar 
trees and shrubs of a tropical beach have been mentioned in 
this connection either by Professor Schimper or by myself. There 
are other genera that afford similar indications but in a less direct 
fashion. 

For instance, there are three widely spread Leguminous beach 
plants of the Pacific, Erythrina indica, Canavalia obtusifolia, and 
Sophora tomentosa, none of which are found in Hawaii ; but 

C 2 



20 A NATURALIST IN THE PACIFIC CHAP. 

in that group the genus is represented in each case by an inland 
species, Erythrina monosperma, Canavalia galeata, and Sophora 
chrysophylla, the last two species being peculiar to those islands. 
The seeds of the three littoral species will float for a long time in 
sea-water, whilst those of the three Hawaiian inland species have 
no buoyancy. I may say that some very interesting questions 
relating to the origin of these inland species are here raised. They 
will be discussed in a later chapter (Chap. XV.). 

There are a number of plants belonging to the Convolvulaceae in 
these islands that behave in an irregular way in flotation experi- 
ments ; but their inconstant behaviour can in most cases be 
explained in accordance with the principle that in the same genus 
the shore species have buoyant seeds and the inland species non- 
buoyant seeds. Thus, whilst the seeds of the littoral species, 
Ipomea pes caprae, I. grandiflora (Lam.), and I. glaberrima (Boj.), 
can float for long periods, and those of the inland species, I. penta- 
phylla, I. tuberculata, and I. Batatas (Sweet Potato), have no 
buoyancy, the seeds of other inland species, I. insularis (Steud.), 
I. bona nox (L.), and 1. turpethum (R. Br.), are inconstant in their 
behaviour. The three last-named species are, however, to be found 
also flourishing at times at and near the coast, and the varying 
floating powers of their seeds may probably be connected with 
their varying stations. This is indeed suggested by the case 
of Argyreia tiliaefolia in Hawaii, in which in my experiments 
the seeds of plants growing at the coast floated, sometimes for 
months, whilst those from inland plants sank. 

This behaviour of the Convolvulaceae becomes yet more intelli- 
gible, and more in accordance with the principle, when we reflect 
that the cause of buoyancy is not concerned with the seed-coats or 
with the nucleus, neither of which are able to float, but with 
the air-spaces left by the incomplete filling-up of the seed-cavity 
by the crumpled embryo. The extent to which the seed-cavity is 
filled up varies not only between different genera and between 
different species of the same genus, but also amongst individuals of 
the same species. Even the seeds of Ipomea pes caprae, amongst 
the most typical of floating seeds, display this variation, and they 
show it also in their floating power, since about a third of the seeds 
usually sink during the first month or two of the flotation experi- 
ments. We can thus explain also why in the case of Ipomea 
insularis seeds from Fiji floated for months, whilst those from 
Hawaii had no floating power. 

The seeds of the different species of Hibiscus also appear to 



ii THE FLORAS OF THE PACIFIC ISLANDS 21 

behave very irregularly ; but even here most of the difficulties can 
be removed, when we come to consider a further extension of the 
principle. Thus, whilst the seeds of Hibiscus tiliaceus, a wide- 
ranging littoral tree known to be dispersed by the currents, float for 
a long time, those of H. Youngianus (Gaud.), an endemic Hawaiian 
species, and of two wide-ranging species, H. diversifolius (Jacq.) 
and H. Abelmoschus (L.), also float for some time. The Hawaiian 
plant, however, grows in wet places ; and this applies also to 
H. diversifolius which grows in swamps at and near the coast. 
The extension of the principle to water-side plants generally, 
which is discussed in the next chapter, will explain the difficulties 
connected with these two species. But we have in H. Abelmoschus 
a remarkable exception to any rule of buoyancy, since it grows in 
dry situations, is often cultivated, and yet possesses a special layer 
of buoyant tissue in the seed-coats to which the floating power is 
due. The seeds of Hibiscus esculentus (L.), the widely spread 
cultivated plant of the tropics, have no buoyancy. 

Some curious indications are supplied by Caesalpinia, a 
Leguminous genus, containing two wide-ranging shore species. 
Speaking generally the rule applies ; and I found in Fiji that 
whilst the seeds of the two littoral plants (C. Bonducella and 
C. Bonduc) were as a rule buoyant, those of an inland mountain 
species sank. But it is very remarkable that although the seeds of 
C. Bonducella have long been known to be transported by the 
currents, and are often stranded by the Gulf Stream on the coast 
of Scandinavia, when it grows in Hawaii, where it is as a rule an 
inland plant, the seeds lose their buoyancy. This is quite in 
accordance with the general principle ; but I must refer the reader 
for a general treatment of this genus to Chapter XVII. There 
also will be found the instance of another Fijian littoral plant, 
Afzelia bijuga, a common littoral tree with buoyant seeds which 
also lose their buoyancy when the tree grows inland. A similar 
instance is afforded by Kleinhovia Hospita, the seeds of which 
seem to lose their buoyancy in inland stations. Not all littoral 
plants, however, lose the floating power of the seeds when grown 
away from the coast. The seeds of Ipomea pes caprse retain it in 
spite of the change of station. This point is dealt with in 
Chapter XIII and in Note 44. 

In concluding this general sketch of the first results obtained 
by testing the buoyancy in sea-water of a collection of seeds and 
fruits from a mountainous Pacific island, such as we find in Fiji, I 
must remind the reader that the subject has only been lightly 



22 A NATURALIST IN THE PACIFIC CH. n 

treated. Enough, however, has been said to illustrate the character 
of the sorting-process by which in the course of ages the plants 
with buoyant seeds or seedvessels have been gathered at the coast. 
This is indicated : 

(1) By the far greater proportion of species with buoyant seeds 
and seedvessels amongst the shore plants than among the inland 
plants. 

(2) By the circumstance that almost all the seeds or fruits that 
float unharmed for long periods belong to shore plants. 

(3) By the fact that when a genus has both inland and littoral 
species, the seeds or fruits of the coast species as a rule float for a 
long time, whilst those of the inland species either sink at once or 
float only for a short period. 

These results, therefore, justify our dividing the flora of our 
island into two groups, the one including the plants with buoyant 
seeds or fruits and comprising most of the littoral plants, the 
other including the plants with non-buoyant seeds or fruits, a 
group which contains almost all the inland plants and indeed 
nine-tenths of the flora. This classification is a very crude one ; 
but it enables us at once to assign a value to the agency of 
currents in stocking a Pacific island with its plants. Yet this is 
but the initial step in an inquiry that branches off in a thousand 
different ways, even if restricted to the littoral plants. There are 
a host of difficulties connected with the history of the strand-flora 
of such an island which can only be properly gauged when viewed 
from various standpoints. 



CHAPTER III 

THE LESSON OF THE BRITISH FLORA 

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 singular relation between station and seed-buoyancy that 
exists in an island of the tropical Pacific, such for instance 
as Vanua Levu, Tahiti, or Hawaii, would lose much of its 
significance if it stood alone in the economy of plant-life. It 
must be true not only of tropical floras generally, but of those 
of the temperate regions ; and there can be little doubt that it 
prevails all over the world. Displayed to us at first in a Pacific 
island, it acquires a new significance when we study it in the light 
of numerous observations made in Europe. It exhibits itself then 
as part of a far wider method pursued by Nature in determining 
the stations of plants. It is not only at the coast, but also at the 
river-bank and at the lake-side that Nature "locates" the plant 
with the buoyant seed or seedvessel. This relation is indeed 
as well exhibited in inland districts as it is at the coast. 

In this connection I have the results of my own investigations 
on the buoyancy of the seeds and fruits of British plants and on 
the composition of the seed-drift of ponds and rivers, which were 
carried on in the years 1890 96. Some of them were published 
in a short paper on the seed-drift of the Thames, read before the 
Linnean Society of London in June, 1892, and in the columns of 
Science Gossip for April, May, and October, 1895 ; but the mass of 
the observations remain in my notebooks. Nor do my observa- 
tions of the period since elapsed lead me to alter the position then 
adopted. I have since pursued the same line of inquiry in Hawaii, 



24 A NATURALIST IN THE PACIFIC CHAP. 

Fiji, on the Pacific coast of South America, and in Sicily, and with 
the same results. 

Since the elaboration of my notes was begun in 1900, Dr. 
Sernander, the Swedish botanist, has published (1901) his work in 
Swedish on the Dispersal-biology of the Scandinavian plant-world, 
in which the seed-drift of river, pond, and sea is exhaustively 
treated. Although this author has dealt with plant-dispersal from 
a somewhat different standpoint, I have perused his pages with the 
keenest interest and with great profit, having gone over much of 
the same ground with respect to the seed-drift of ponds and rivers. 
Yet the introductory remarks to my paper in Science Gossip in 1895 
are as apposite now as they were then, and the reader will, I trust, 
pardon my reproducing them. 

" By following up the path of inquiry that is concerned with the 
flotation of seeds and seedvessels, we are guided into other fields of 
research that give promise of interesting discoveries in connection 
with plant-life. We are led in the first place to consider the ques- 
tion of utility, and to ask whether the buoyancy of the seed or 
fruit has been a matter of moment in the history of the species. 
Nature is ever engaged in telling off the plants to their various 
stations. She places the yellow iris at the river's side and assigns 
to the blue iris its home in a shady wood. Under her direction 
the common alder thrives at the water's edge, whilst its fellow 
species live on the mountain slope. These and similar operations 
are carried on daily around us, and we know but little of the where- 
fore and the how. We are induced, therefore, to inquire whether 
by pursuing the line of investigation above indicated we may be 
able to get a glimpse at the methods adopted by Nature in select- 
ing stations for plants." 

I possess the results, which are given in Note 10, of buoyancy 
experiments and observations on the seeds and seedvessels of 
about 320 British flowering plants belonging to about 65 families. 
Of these about 260 are included in my own results, the data for the 
rest being obtained from the writings of Darwin, Martins, Thuret, 
Kolpin Ravn, and Sernander. In the great proportion of cases, 
240, or 75 per cent, sinking took place at once or within a week ; 
whilst 80, or 25 per cent., floated for a longer period, usually a month 
or more ; and about 60, or nearly 20 per cent., floated for several 
months. It is to this last small group that belong the seeds or 
seedvessels that float through the winter in our ponds and rivers. 

If the grasses had been properly represented, the grains of which 
possess as a rule but little buoyancy, except through air-bubbles 



in THE LESSON OF THE BRITISH FLORA 25 

temporarily entangled in the glumes, the proportion of seeds and 
fruits that sink at once or in a few days would probably have been 
about 80 per cent. Then again, since the plants from stations 
where buoyant seeds and seedvessels are most frequently found 
that is at the river-side, the pond-margin, and the sea-coast are 
much more completely represented in these experiments than those 
from other stations, it would seem that even 80 per cent, is too low 
a figure. Even if the 80 plants with the buoyant seeds or seed- 
vessels included all the species thus characterised, which they 
certainly do not, we should obtain an estimate for the British 
flora (rather over 1,200 species of flowering plants) of about 93 per 
cent, with non-buoyant seeds or fruits. This is, of course, too high. 
It is, however, very probable that the proportion of plants with 
non-buoyant seeds or seedvessels for the whole British flora is 
about 90 per cent. 

This proportion of plants with non-buoyant seeds or seed- 
vessels, that is to say, of those that sink at once or within a week, 
is also approximately correct for the flora of one of the larger 
islands of the tropical Pacific. The data at my disposal only 
enable me in the cases of Fiji and Hawaii to fix it at between 
95 and 85 per cent., or on an average 90 per cent. With the floras 
of continental regions the proportion would doubtless be markedly 
higher. That seeds and seedvessels as a rule possess but little 
buoyancy was a sound conclusion of Darwin, and one, as he 
remarked, that is in accordance with the common experience 
of gardeners. Thuret, after experimenting on the buoyancy in 
sea-water of the seed or seedvessels of 251 species of plants, 
belonging to 77 families and to various regions, found that 
scarcely two per cent, had any powers of flotation, all the 
rest sinking at once or in a few days, a result that led De 
Candolle in a note to this memoir to reiterate his opinion 
regarding the inefficacy of currents as plant distributors. Thuret, 
however, did not select many of his plants from stations where 
buoyancy is most frequently exhibited, and his estimate errs, 
therefore, in imputing too little buoyancy to seeds in general. The 
power of seeds and fruits to germinate after prolonged flotation in 
sea-water has long been well established, and it is often illustrated 
in this work, so that there is no need to dwell upon it here. (See 
Note 11.) 

Of the 240 species of British plants where sinking took place 
at once or within a week, in about 50 per cent, the plants had dry 
indehiscent fruits, such as we find in the genus Ranunculus and in 



26 A NATURALIST IN THE PACIFIC CHAP. 

the Umbelliferae, the Compositae, and the Labiatae ; whilst in about 
a third the plants had dehiscent fruits with small seeds, such as 
are characteristic of the Cruciferae, the Caryophyllaceae, and the 
Juncaceae. Plants with large seeds, such as those of Nuphar 
luteum and Convolvulus arvensis, make up only six per cent, of 
those of the non-buoyant group, the remainder comprising plants 
with berries, such as Solanum, and others with miscellaneous fruits. 

Of the 80 plants where the seeds or fruits floated more than a 
week, usually for several weeks, and often for months, 70 per cent, 
possessed dry, indehiscent fruits, such as those of Hydrocotyle 
vulgaris, Bidens cernua, Lycopus europaeus, Carex, &c., whilst only 
6 or 7 per cent, had dehiscent fruits with small seeds, such as we 
find in Lysimachia and Menyanthes, the remainder being generally 
characterised by large seeds, such as those of Convolvulus sepium, 
C. soldanella, Iris pseudacorus, Calla palustris, &c. It would thus 
appear that, in so far as buoyancy is concerned, Nature has for the 
most part ignored the small seed and has confined herself mainly 
to the dry indehiscent fruit. We have already seen that this 
is also true of the same great sorting-process in the tropical islands 
of the Pacific, and it doubtless applies all over the world. 

We have now to learn the significance of this distinction 
amongst British plants between those with and those without 
buoyant seeds or seedvessels. When we regard the stations of 
these 80 plants of the buoyant group we find that about 70 per cent, 
of them are placed by the river, or the pond, or the sea, the fresh- 
water stations much predominating. But if we include the plants 
of the moist meadows adjoining the rivers, such as Ranunculus 
repens, Rhinanthus crista galli, some Cyperaceae, &c., the buoyant 
fruits or seeds of which are regularly swept into the stream in the 
time of flood, we shall raise the proportion possessing a water-side 
station to 80 per cent. On the other hand, about two-thirds of the 
240 plants of the non-buoyant group, which are enumerated in 
Note 10, live away from the water-side ; but the proportion of 
plants with a relatively dry station would be considerably higher 
than this figure for the whole flora, since my investigations 
were especially directed towards plants frequenting wet stations, 
and the number of them is excessive in the list. 

Supposing, however, that our materials were restricted to the 
260 plants tested by myself, we should obtain highly instructive 
results, since in a general sense the floating powers of their seeds 
or fruits were tested to the finish. We place them, let us say, in a 
bucket of water, and after six months we find that in not more 



in THE LESSON OF THE BRITISH FLORA 27 

than forty plants are the seeds or seedvessels still afloat. These 
forty plants, excluding two or three littoral plants, are nearly all 
plants of the borders and vicinity of rivers and ponds. (They are 
indicated in the list given in Note 10 by the numbers vi. and xii., 
the last being those where the flotation experiment was prolonged 
to a year and over.) 

It would thus seem I am now quoting mainly from my paper 
in Science Gossip for May, 1895 that there are gathered at the 
margins of rivers and ponds, as well as at the sea-border, most of 
the British plants that could be assisted in the distribution of their 
seeds by the agency of water. This great sifting experiment has 
been the work of the ages, and we here get a glimpse at Nature in 
the act of selecting a station. But the curious character of the 
sorting process becomes yet more apparent when we discover that 
the buoyancy of the seeds or fruits of species of the same genus 
may become a matter of station. 

We will first take the four British species of Stachys (arvensis, 
betonica, sylvatica, and palustris). Of these the fruits of S. palus- 
tris alone possess any buoyancy, being able to float for weeks. It 
is the only species that finds its characteristic home at the water- 
side ; and as observed by Sernander its reproductive shoots occur 
in the Scandinavian fresh-water drift. 

Galium illustrates the same principle. Whilst in my experi- 
ments the fruits of G. aparine and of another species growing in a 
dry station displayed little or no floating power, those of G. palustre, 
which alone grows at the water-side and in wet situations, have 
great buoyancy. As my observations show, they float unharmed 
through the winter in our ponds and rivers, and, according to 
Sernander, are often found in the Baltic sea-drift. (See Note 12.) 

The achenes of Potentilla afford another example. Those of 
P. tormentilla and of another species from dry situations have but 
little floating power. On the other hand, those of P. comarum 
float indefinitely. The last also came under my notice in the 
floating drift of ponds in February ; and we learn from 
Sernander that they occur in the fresh-water and salt-water drift 
of Scandinavia. 

As a further instance, I will take the two British species of 
Iris. The familiar river-side Iris pseudacorus has seeds that float 
unharmed in our ponds and rivers from the autumn to the spring, 
and often for a year or more. On the other hand, the seeds of 
Iris fcetidissima, which has its home in the shady wood, sink at 
once even after drying for months. 



28 A NATURALIST IN THE PACIFIC CHAP. 

The nature of the sorting-process is especially well shown in 
some of the families, as for instance with the Labiatse. Let the 
reader put on one side the four species with buoyant fruits, namely,. 
Lycopus europaeus, Mentha aquatica, Scutellaria galericulata, and 
Stachys palustris, and on the other side all the species with non- 
buoyant fruits, such as Salvia verbenaca, Thymus sp., Calamintha 
officinalis, Nepeta glechoma, N. cataria, Prunella vulgaris, Stachys 
arvensis, S. betonica, S. sylvatica, Galeopsis tetrahit, Ballota nigra, 
Lamium purpureum, L. album, Teucrium scorodonia, and Ajuga 
reptans, and he will at once perceive that he has separated the 
regular water-side plants from those growing in drier stations. 

If he does the same with the Umbelliferae he will find that 
when he is separating Hydrocotyle vulgaris, Cicuta virosa, 
CEnanthe crocata, and Angelica sylvestris from ^Ethusa cynapium, 
Pastinaca sativa, and Chaerophyllum sylvestre, on account of their 
buoyant fruits, he is also distinguishing them on account of their 
stations. On the other hand, there are apparently weighty excep- 
tions to this rule in the non-buoyancy of the fruits of the three 
British species of Apium (graveolens, nodiflorum, inundatum), 
which grow in streams and marshes. Or, again, if we look at the 
sea-coast representatives of the family, we find that whilst the 
fruits of the Samphire (Crithmum maritimum) float buoyantly for 
months, those of Eryngium maritimum seemingly set the law at 
defiance, and all sink in less than a week or ten days, even after 
months of drying. To regard these as exceptions, however, is to 
miss the essential point of the principle concerned. It is not 
thereby implied that all water-side plants, whether by the sea or 
by the river or by the pond, have buoyant fruits or seeds, but that 
nearly all plants with such fruits or seeds have been gathered at 
the water-side. It will be shown in the next chapter that several 
other influences go to determine the station of a plant on a beach 
or by a river. This is true of the Compositae, which, if we except 
our two species of Bidens (cernua and tripartita), come under the 
play of other determining causes, as indicated by the little or no 
buoyancy displayed by the fruits of Aster tripolium, Senecio 
aquaticus, and Carduus palustris. 

Within the limits of a genus we can, however, point to other 
examples of this principle. Take, for instance, Convolvulus arvensis, 
the common weed of our fields. Its seeds, whether fresh or dried 
for months, have no buoyancy. On the other hand, those of 
Convolvulus soldanella float unharmed in sea-water for half a year 
and more. Its seeds have come frequently under my notice among 



in THE LESSON OF THE BRITISH FLORA 29 

the stranded drift of the Devonshire beaches, and also on the 
coasts of Chile ; whilst Sernander includes them amongst the drift 
of the beaches on the Norwegian coasts. It is remarkable that 
Convolvulus sepium, which accompanies C. soldanella over much 
of its great range, has seeds that are sometimes able to float 
unharmed for long periods, even for years (Notes 13, 41, 49). 
Though not strictly a water-side plant, it grows commonly over 
other plants on the banks of the Thames ; and when it fruits its 
seeds occur typically in the floating drift of that river. According 
to Gray, it is almost a river-side plant in the United States, where 
it is found " especially on the moist banks of streams." Not all 
the seeds of C. sepium, however, are buoyant ; and in its varying 
behaviour in this respect it resembles the inland species of Ipomea, 
which are referred to in the previous chapter. 

The British species of Euphorbia also seem to behave in 
accordance with the principle that when a genus has littoral and 
inland species, the first-named alone possesses buoyant fruits or 
seeds. Thus, whilst the sound fruits of E. helioscopia and of 
another species found commonly as a garden weed are non- 
buoyant, those of E. paralias, the familiar beach-plant, float for 
several weeks, and are to be noticed among the stranded drift of 
the coasts frequented by this plant. (See Note 90 for later results.) 

The structural characters connected with the buoyancy of the 
seeds or seedvessels of some of the British plants are dealt with in 
Chapter XII. Here it may be remarked that this capacity is often 
associated, as with the Pacific island plants, with a "buoyant" 
tissue, that is either absent or less developed in the case of the 
non-buoyant group. 

Enough has now been said to show in a general fashion how 
Nature through the agency of buoyant seeds and fruits has affected 
the stations of plants of the British flora. Allowing this line of 
inquiry to develop itself as the work proceeds, we will here pause 
and close the chapter with a reference to some of the principal 
points that have been brought into prominence. 

(a) The proportion of flowering plants of the British flora that 
possess buoyant seeds or seedvessels is very small, probably not 
more than 10 per cent. 

() In so far as buoyancy is concerned, Nature has for the most 
part ignored the dehiscent fruit with small seeds, such as we see in 
the Cruciferae and the Caryophyllaceae, and has chiefly endowed 
with floating power the dry indehiscent fruit, such as we see in the 
Umbelliferae and in the Labiatae. 



30 A NATURALIST IN THE PACIFIC CH. in 

(c) In the great sorting-process that has been in operation 
through the ages, nearly all the plants with buoyant seeds or seed- 
vessels have been located at the water-side, principally by ponds 
and rivers, but also on the sea-beach. On the other hand, the 
great majority of the plants with seeds or seedvessels that sink 
have found a home in drier stations. 

(d} The character of the operation is well displayed in certain 
genera possessing species of the water-side and species of drier 
situations, and in the case of genera having both coast and inland 
species. In both instances the species by the water-side possesses 
buoyant seeds or fruits, whilst that of the station in a drier locality 
or removed from the coast has seeds or fruits that sink. 

(e) Yet it is necessary to remember that the principle involved 
is not that all water-side plants have buoyant seeds or fruits, but 
merely that plants thus endowed gather at the water-side. There 
are many plants with non-buoyant seeds or fruits on our beaches 
and beside our ponds and rivers. 

(/) We have now learned from the British flora that the 
" locating " of plants with buoyant fruits or seeds on the beaches 
of the tropical islands of the Pacific, and indeed of tropical regions 
generally, is but a part of a much wider principle by which plants 
thus endowed are placed at the water-side, whether by a river or a 
pond or by the sea. 

(g) It is with this distinction between a fresh-water and a salt- 
water station that we shall be occupied in the next chapter ; and 
it is of great interest, since it leads us to discover that the wider 
principle is in its turn part of a far larger scheme. 



Note. It must be clearly understood that by water-side plants 
the true aquatic plants, such as the Water-lilies, the Myriophylls, 
the Potamogetons, &c., are not implied. It will be seen from the 
list in Note 10 that in most cases the seeds or fruits of aquatic 
plants have little or no floating power. This is true, for instance, 
of Ranunculus aquatilis, Nymphaea, Nuphar, Myriophyllum, Cerato- 
phyllum, Callitriche, Naias, Zannichellia, Ruppia, and half the 
Potamogetons. 



CHAPTER IV 

THE LESSON OF THE BRITISH FLORA (continued) 

The choice of station of the water-side plant possessing buoyant seeds or seed- 
vessels. Determined by its fitness or unfitness for living in physiologically 
dry stations. In the internal organisation of a plant lies the first de- 
termining 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. 

BY following up the clue supplied by the floating seed, we have 
arrived at the conclusion with respect to the British flora that 
plants with buoyant seeds or fruits gather at the water-side. But 
we have yet to inquire why some of these plants are " located " at 
the sea-coast and others on the borders of ponds and rivers. Mere 
buoyancy aided by chance has not determined the choice. There 
are definite principles at work in the economy of plant-life that 
make the selection for each plant. 

Rivers in all parts of the world carry to the sea in great 
abundance the seeds and fruits of the plants that are stationed 
at their borders ; and such seed-drift is found in quantity washed 
up on the beaches in the vicinity of the estuary. One finds, for 
instance, on such beaches in the South of England the stranded 
fruits and seeds of Bidens cernua, Alnus glutinosa, Sparganium 
ramosum, Iris pseudacorus, &c., mingled with those of true beach 
plants like Cakile maritima, Convolvulus soldanella, Euphorbia 
paralias, &c. Yet we would be much surprised if either the Bidens 
or the Alder or the Sparganium were to establish itself on the 
sandy beach, even though they have had through the ages in- 
numerable opportunities of doing so. We thus see that mere 



32 A NATURALIST IN THE PACIFIC CHAP. 

buoyancy of fruit or seed cannot determine a station on a sea- 
beach, and that some other factor makes the choice. The nature 
of this factor I will now endeavour to explain ; but in so doing 
it will be necessary to employ a few technical terms, which it is 
not easy to dispense with altogether. 

It may be doubted whether Professor Schimper could have 
conferred a greater benefit on the student of plant-distribution 
than in his clear delineation of the connection between the habit 
or organisation of a plant and its station. Nature has imposed an 
important structural distinction between plants that have been 
endowed with the means of checking excessive transpiration or 
water-loss in stations where there is risk of drought, as in deserts 
and in similar arid localities, and those that live in stations where 
such safeguards are not needed. Hence arises the distinction 
between Xerophytes on the one hand, and Hygrophytes on the 
other. This contrast is shown not only in minute structural 
features, but also, as my readers are aware, in the external 
characters, as in hairiness, succulency, a leathery cuticle, the 
occurrence of thorns, and in several other characters of the 
plants of the steppe and the desert. This important subject is 
dealt with by Professor Schimper in his recent work on Plant- 
Geography ; but it was from his earlier work on the Indo- 
Malayan strand-flora that I learned this valuable lesson in 
plant-distribution. 

It has been ascertained, however, that a safeguard against 
excessive water-loss by transpiration is not only needed by plants 
living in arid localities, but also by those placed at the coast. Both 
the shore plant and the plant of the steppe and the desert present the 
.same xerophilous organisation, provision against excessive transpira- 
tion being also required by the beach plant to prevent the injury of 
the green cells from the accumulation of salt in the tissues. It would 
thus appear that plants of the Hygrophytes that possess buoyant 
seeds or fruits are gathered at the borders of ponds and rivers, whilst 
those of the Xerophytes that are similarly endowed find their 
station on the sea-shore. This important distinction penetrates 
very deeply into the conditions defining the stations of plants. 
The connection between the plant of the coast and the plant of the 
steppe or the desert is strikingly shown on those occasions when 
the beach plants extend inland over parched and arid plains, such 
as occurs for instance in North Africa, and in the larger islands of 
Fiji, as described in Chapter V. 

The causes of the buoyancy of fruits and seeds, as pointed out 



iv THE LESSON OF THE BRITISH FLORA 33 

in Chapter XII, are so various, that it appears at first sight im- 
possible to connect them with the xerophilous or hygrophilous 
organisation of a plant, or, in other words, with any structural 
characters associated with particular stations ; yet behind all lies 
the general principle that, given a plant of the buoyant group, 
if it is a Xerophyte it finds its way to the coast, and if a Hygrophyte 
it makes its home by ponds and rivers. In the case of a tropical 
littoral flora, such as we find in a Pacific island, the large proportion 
of plants with buoyant fruits or seeds gives so much prominence to 
the subject of their distribution by currents that the question of 
" station " is often masked. On the other hand, in the shore-flora 
of a temperate region like that of Great Britain, the plants with 
buoyant seeds or fruits are in the minority, and the question of 
" station " is the first to obtrude itself. 

In establishing the principle that most of the plants with 
buoyant seeds or fruits have been gathered at the water-side, it 
was never implied that all the plants by the river or by the pond 
or at the coast are thus characterised. There is much to learn 
from the circumstance that whilst nearly all plants with buoyant 
seeds or fruits are placed at the water-side, not all water-side plants 
have buoyant seeds or fruits. In the first place, it is to be inferred 
in the light of what has been said above that the first determining 
principle in the selection of a station is concerned not with the 
buoyancy of the seeds or fruits, but with the xerophytic or hygro- 
phytic organisation of a plant. In other words, it is the fitness or the 
unfitness of a plant for living in situations where the loss of water 
by transpiration requires to be checked that primarily determines 
the station at the coast. We thus see in the internal organisation 
of the plant the primary determining influence on station. Buoyancy 
of seed or fruit comes subsequently into play, the Xerophyte and 
the Hygrophyte, thus endowed, ultimately finding their way, the 
first to the beach, the second to the bank of the river or to the 
margin of the lake or pond. 

In the next place, when we regard the composition of the 
British coast-flora, and examine the distribution of the plants 
in other situations than on the beach, we obtain some interesting 
results. There is first a group of plants, including such as Armeria 
vulgaris, Artemisia maritima, Cochlearia officinalis, Erodium mari- 
timum, Matricaria inodora, Plantago coronopus, Polycarpon tetra- 
phyllum, Raphanus maritimus, Spergularia rubra, Silene maritima 
(see Note 15), and others, all of which occur not only at the coast 
and on the adjacent hill-slopes, but also often far inland, and 
VOL. II D 



34 A NATURALIST IN THE PACIFIC CHAP. 

sometimes at considerable elevations in mountainous districts, as in 
Central Europe. It is on this occurrence of certain shore-plants in 
alpine regions that Prof. Schimper lays much stress in his 
memoir on the Indo-Malayan strand-flora (p. 28), and in his later 
work on Plant Geography (Engl. edit., p. 716), when pointing out 
that here temperature does not play a determining part, and that 
in both stations, whether on the sandy beach or on the mountain- 
top, the same xerophilous organisation is needed to obviate the 
risk of impeded water-supply. He quotes in this connection 
the observation of Battandier that many alpine species from 
the Atlas Mountains occur on the Algerian beaches, but not in 
intervening regions. Mr. Druce, in his discussion of the British 
species of Sea-Thrifts and Sea-Lavenders (Armeria,Statice), brought 
the subject of the occurrence of maritime plants on mountain sum- 
mits again to the front ; but he did not advance any general 
explanation, and seems to regard it as the result, as it doubtless 
is, of the recurrence of suitable stations (Jour. Linn. Soc. Bot., 
Dec. 1900). 

Very few of these plants have any capacity for dispersal by 
currents, a subject dealt with in Note 16. Several of them have 
dehiscent, small-seeded fruits which, as pointed out in the previous 
chapter, hardly ever come into the buoyant category. I have 
experimented on the greater number of them, and in only one 
species, Matricaria inodora (var. maritima), do the results indicate 
a capacity for dispersal over wide tracts of sea. 

If we look again at a list of British shore-plants, we find 
another group of plants frequenting salt marshes and muddy 
shores, and found also often far inland, as in the saline plains 
of Central Asia. Here we have such plants as Aster tripolium, 
Glaux maritima, Plantago maritima, Salicornia herbacea, Salsola 
kali, Samolus valerandi, Scirpus maritimus, Suaeda fruticosa, 
S. maritima, Triglochin maritimum, T. palustre, &c. It becomes in 
this connection a subject of peculiar interest to the student of plant- 
distribution when he reads in Mr. Hemsley's paper on the flora of 
Tibet (Jour. Linn. Soc. Bot., vol. 35) that amongst the British shore- 
plants above-named the two species of Triglochin and the same 
species of Glaux and Salsola occur in the salt marshes of the Tibetan 
uplands at elevations of 15,000 to 16,000 feet, Scirpus maritimus 
also being found in the swamps of the lower levels. We have the 
same thing, affecting much the same plants, illustrated in America. 
Thus we learn from Asa Gray that Salicornia herbacea, Scirpus 
maritimus, Triglochin maritimum, &c., which are common in salt 



iv THE LESSON OF THE BRITISH FLORA 35 

marshes on the coast of the United States, occur also in the 
interior of the continent in the vicinity of salt-springs. 

Facts of this sort are well known, and I merely refer to them 
here in order to emphasise the importance of this little group 
of British littoral plants, those of the salt marsh. Their very wide 
distribution is connected with the frequent recurrence of suitable 
conditions, not only in space, but what seems of greater import, 
also in time. One can scarcely doubt when the Saltwort (Salsola 
kali) is seen on the Devonshire coast, on a beach in Chile, and in 
the elevated regions of Central Asia that here a very ancient type 
of plant finds its still more ancient conditions of existence. In the 
capacity which most of the plants of the salt marsh possess of 
germinating in sea-water, this group of littoral plants is sharply 
distinguished, as far as my observations show, from the other 
groups of British shore-plants. For instance, in my experiments 
the seeds of Aster tripolium, Salicornia herbacea, and Triglochin 
maritimum germinated freely in sea-water, whilst those of Sper- 
gularia rubra, Cakile maritima, Convolvulus soldanella and others 
failed to do so^(see Note 19). It will also be noticed with 
respect to this group of littoral plants that, except in the case of 
Scirpus maritimus, the seeds or fruits have little or no floating 
power, the exception offered by Salsola kali being not very striking. 
This feature is brought out in the Table given in Note 10 ; but 
some of the details of my observations are given in Note 17. 

There yet remains a third group of the British shore-plants, 
namely, that comprising the plants that rarely stray far from the 
beach and often possess seeds or seedvessels that will float for 
months. Here we have such species as Arenaria (Honckeneya) 
peploides, Beta maritima, Cakile maritima, Crambe maritima, Crith- 
mum maritimum, Convolvulus soldanella, Eryngium maritimum, 
Euphorbia paralias, Glaucium luteum, Lathyrus maritimus, Poly- 
gonum maritimum, &c. The seeds or seedvessels of quite half 
of these species will float for months unharmed in sea-water, but 
in a few, as with Cakile maritima and Eryngium maritimum, they 
float for only a week or two, whilst in others again like Glaucium 
luteum they have no buoyancy. (Some details of the buoyancy 
experiments on these plants are given in Note 18 ; and the long 
list in Note 10 may be first consulted.) 

It is not necessary to enter here into more detail with respect to 
British shore-plants. Enough has been said to disclose cleavage- 
lines in what might have appeared as a homogeneous plant-forma- 
tion. We can thus discern the elements of at least three groups 

D 2 



36 A NATURALIST IN THE PACIFIC CHAP. 

amongst the plants of our beaches, each group bearing the impress 
of an independent history : 

(a) The plants of the beach and of the inland plain or of the 
distant mountain peak, excluding those of the salt marshes. 
Armeria vulgaris, Silene maritima, and Spergularia rubra may be 
taken as examples. The currents here as a rule take little or no 
part in their dispersal. 

(b) The " saline " group, including the plants of the saline plains 
and the salt marshes of the interior of continents. Of these Glaux 
maritima, Salsola kali, and Triglochin maritimum are examples. 
The capacity of germinating in sea-water is a distinguishing 
character of most of the plants ; and but few of them possess seeds 
or seedvessels that are markedly buoyant. 

(c) The true beach plants that rarely stray far from the beach, 
of which Arenaria peploides, Cakile maritima, and Convolvulus 
soldanella are examples. Many of them have buoyant seeds or 
fruits capable of dispersion over wide areas through the agency 
of the currents. 

The reader will be able to extend this subject for himself if he 
is so inclined, but we have gone far enough together to learn that 
the plants with buoyant seeds or fruits are in the minority on our 
beaches, scarcely a third of the total being fitted for dispersal by 
the currents over broad tracts of sea. The British strand-flora thus 
differs strikingly from the littoral flora of a Pacific island, or indeed 
of any ordinary tropical coast, and in this respect it is to be 
regarded as typical of the temperate regions. It has been re- 
marked before that on a beach in the tropics we would expect 
to find that quite three-fourths of the plants are provided with 
buoyant fruits or seeds distributed far and wide over the tropical 
seas by the currents. 

We pass on now to briefly discuss from the same standpoint 
the British plants that find their homes on the borders of rivers 
and ponds. It is here that the hygrophytes with buoyant seeds or 
fruits gather together, just as the xerophytes with similar seeds or 
fruits collect on the beaches. We have seen before that only a 
portion of the beach plants belong to the buoyant group, and the 
same applies to the plants at the edges of rivers and ponds. The 
plant-formation is no more homogeneous there than it is in the 
case of the strand-flora. Let us see if we can discern some lines of 
division there also, or in other words let us endeavour to connect 
the absence or presence of floating power in the fruits and seeds 
with some variations in the placing of the plants. We still pursue 



iv THE LESSON OF THE BRITISH FLORA 37 

the clue to the study of the complicated problems connected with 
plant-stations by taking the floating seed as our guide. 

We will carry ourselves in thought to the Thames-side between 
Teddington and Twickenham at the end of August, 1892. The 
river is at the high-water level, and we see flourishing at the 
margins, sometimes a little above the water and sometimes a little 
within its reach, Ranunculus repens, R. sceleratus, Spiraea ulmaria, 
Lycopus europaeus, Scutellaria galericulata, different species of 
Rumex, Alnus glutinosa, Iris pseudacorus, Sparganium ramosum, 
and different species of Carex, with several other plants, all con- 
tributing their seeds or fruits to the drift that floats in the river 
from the autumn to the spring. 

But besides these plants there are a number more or less 
submerged in the stream, including Nasturtium amphibium, N. 
sylvestre, Stellaria aquatica, Myosotis palustris, and Veronica 
beccabunga ; and as the water falls other plants still more sub- 
merged come into view on the exposed flats, such as Nasturtium 
officinale, Apium nodiflorum, and Polygonum hydropiper. None 
of these plants are represented by their seeds or fruits in the float- 
ing river-drift. Several of them possess dry dehiscent fruits with 
small seeds, such as Nature ignores in the matter of buoyancy, and 
the small fruits of Myosotis, Apium, and Polygonum have little or 
no floating power. 

We have thus here a clear dividing line between the plants with 
buoyant seeds or fruits that were more or less exposed above the 
high-water level, and those that were more or less submerged at 
that state of the tide. That which occurs in the Lower Thames 
twice in the day within the reach of the tide represents what 
happens in the higher part of the river during the seasonal floods, 
but in the last case the effects cannot be so readily distinguished. 
We thus perceive that the buoyant seed or fruit is as a rule only 
characteristic of the plants of the river-side that grow more or less 
exposed above the water, whilst those plants liable to periodic 
submergence have seeds or fruits that sink. 

In this connection it is of especial interest to observe that as a 
general rule the truly aquatic plants of English rivers contribute 
little or nothing to the floating seed-drift. I pointed this out 
several years ago, in my paper on the Thames, as an agent in plant- 
dispersal, and it has been already noticed in this work (page 30). 
We look in vain amongst the floating winter drift of our rivers 
for the seeds or fruits of Ranunculus aquatilis, Nuphar luteum, 
Nymphaea alba, and of the species of Myriophyllum, Limnan- 



38 A NATURALIST IN THE PACIFIC CHAP. 

themum, Callitriche, Ceratophyllum, Zannichellia, and of several 
of the Potamogetons, all of which give character in summer to the 
aquatic vegetation of the river. In their place we find only the 
seeds and fruits of the plants growing on the banks. 

There is, however, another small group of river plants, which 
in their structure and habits and in the behaviour of their floating 
fruits come between the true aquatics and the plants of the river- 
banks. They belong mostly to the Alisma family, and Alisma 
plantago and Sagittaria sagittifolia may here be specially 
mentioned. Their fruits display great variation in their floating 
power ; and on this point M. Kolpin-Ravn, writing to me in 1895, 
made the following interesting suggestion, that since these plants 
approach true aquatics in structure they may be also regarded as 
approaching them in the inconstancy of the buoyant capacity of 
their fruits, those of aquatics having typically little or no floating 
power. 

Seed-buoyancy, however, does not play quite such an important 
part in the plant-economy of a river as the examination of the 
floating drift would lead one to expect. Only a portion of the 
bank-plants have buoyant seeds or fruits, whilst amongst the true 
aquatics, the semi-aquatics, and the plants periodically submerged, 
the rule of non-buoyancy prevails. And, indeed, when we look at 
all the possible stations for the plants of the British flora, we 
discover that seed-buoyancy can rarely be connected with station. 
It is, however, in those few stations that plants with buoyant seeds 
have mainly gathered. There it is, probably, that the remnants of 
a past floral age find a refuge, since it would seem likely that the 
tendency has been in the course of geological time for the develop- 
ment of dry stations for plants at the expense of the wet stations. 

The following is a summary of some of the points discussed in 
this chapter : 

(1) In the case of the strand-flora of a Pacific island, and 
indeed in that of an ordinary tropical region, the large proportion 
of plants with buoyant seeds or fruits tends to mask all other 
issues, and we are seemingly only concerned with dispersal by 
currents. 

(2) But in the British strand-flora where plants with buoyant 
seeds and fruits are in a minority, constituting less than a third of 
the total, it is seen that the issue is primarily an affair of station, 
an inference that may be applied generally to temperate regions. 

(3) All British shore-plants may be regarded as owning certain 
characters in common which may be collectively designated the 



iv THE LESSON OF THE BRITISH FLORA 39 

xerophilous habit, and we may extend this view to other temperate 
strand-floras. 

(4) But this xerophilous habit is also characteristic of inland 
plants in certain localities, as of those of the steppe, the desert, the 
rocky mountain- top, and of other exposed situations, in all of 
which checks to the loss of water by transpiration are required. 
Whilst the risks of drought are thus guarded against in the case of 
plants stationed in arid localities, the risk of injury to the plant 
from the accumulation of salt in the tissues is obviated in the 
instance of the plants of the coast. 

(5) On the other side we have the hygrophilous habit 
characteristic of plants living under conditions where checks to 
transpiration are relatively little needed. All the plants of the 
margins of rivers and ponds belong here, and indeed all plants 
living under moist conditions. 

(6) This distinction between the xerophilous and hygrophilous 
habits penetrates deeply into all questions connected with stations, 
and lies behind all matters relating to the buoyancy of seeds or 
fruits. It is the fitness or unfitness of a plant for living in dry 
situations that primarily determines the station. If a xerophilous 
plant has a buoyant seed or seedvessel it finds its way ultimately 
to the coast ; if it is hygrophilous and its seeds or fruits can float, 
then it is finally established on the side of a pond or river. 

(7) The composite character of the British strand-flora is to be 
explained on the above principles. We have in the first place the 
plants confined to the sandy beach, many of which possessing 
buoyant seeds or fruits are dispersed by the currents. Next come 
the plants of the sandy beach which are found also far inland in 
open plains and on mountain-tops ; and afterwards come the plants 
of the salt-marsh and mud-flats of the coast, which appear again 
in the saline plains and swamps in the interior of the continents. 

(8) The plant-formation of the river's border displays also 
lines of division, and is by no means homogeneous ; and indeed 
other factors besides those connected with seed-buoyancy have 
here been in operation. 

(9) In only a few of the possible stations of British plants can 
a direct connection be traced with seed-buoyancy. Yet it is at 
these few stations, such as at the coast and by the pond or river, 
that the plants with buoyant seeds and fruits have mainly gathered. 

(10) The plants now frequenting wet stations may often be 
regarded as the remains of an age when moist conditions for 
plant-life prevailed. 



CHAPTER V 
THE FIJIAN STRAND-FLORA 

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

HAVING learned from the British flora the real significance of the 
buoyant seed or fruit in a littoral flora, we will now return to the 
Pacific and proceed to deal with the composition and general 
character of the strand-plants. 

Speaking of the Malayan strand-plants, Professor Schimper 
remarks (pp. n, 12) that both in outward appearance and in 
anatomical structure they are xerophilous in character, whether in 
the case of those of the mangrove-swamp or in those of the beach. 
Since the tropical shore-flora of the Pacific islands is essentially 
Malayan, the identity usually extending to the species, the same 
conclusion may be applied to its character. The xerophilous habit 
may show itself externally in a variety of ways, as in hairiness, 
leaf-structure, a leathery cuticle, succulency, &c. 

From this xerophilous habit of the Pacific strand-flora we 
should expect to find that many of the plants stray far from the 
coast, wherever the suitable conditions for their type of organisa- 
tion occur, whether in the inland plain or on the mountain-top. 
This is indeed the case ; but in dealing with this subject it will be 
necessary to discuss in some general detail the littoral floras of the 
Fijian, Hawaiian, and Tahitian groups in succession. 

THE FIJIAN STRAND-FLORA 
THE INLAND EXTENSION OF THE BEACH PLANTS 

Viewed from the old standpoint of " station," where one would 
distinguish sharply between the coast and the inland plants, the 
Fijian strand-flora exhibits a number of inconsistencies, all at first 



CH. v THE FIJIAN STRAND-FLORA 41 

sight extremely puzzling. When, however, we regard their xero- 
philous character and reflect that this habit, and not mere fitness 
for growing at the coast, is the primary determining factor of their 
station, much that is strange appears normal and plain. 

Let me refer in this connection to the impression that the 
distribution of the Fijian shore-plants made on Mr. Home, the 
director of the Botanic Gardens of Mauritius, who spent a year 
in the botanical investigation of the group about a quarter of a 
century ago. In his account of the group (pp. 59, 60) he says that 
several of " what are known as sea-shore plants " are found far in 
the interior of the larger islands ; and amongst others he names 
such characteristic beach plants as Cerbera Odollam, Hibiscus 
tiliaceus, Ipomea pes caprse, and Pandanus odoratissimus. On the 
other hand, he remarks that several species of inland plants occur 
at the coast, and that several plants growing on the mountain-tops 
are found near the sea. This apparent confusion of station he 
seems to attribute to the circumstance that the mountains of Fiji 
are not high enough for the development of an alpine flora. But 
such a view could not be held now, since the effect of an alpine 
flora would be the introduction of further elements of confusion in 
the occasional occurrence of some of the alpine plants on the sea- 
coast, as we find in Hawaii. 

Yet this apparent mingling of the littoral and inland floras in 
Fiji becomes intelligible when we perceive that the seeming con- 
fusion of station is mainly restricted to the xerophilous plants of 
the arid inland plains and of the bare mountain-tops. The rank 
humid forests that cover so much of the interior of the islands, and 
the luxuriant vegetation of the mountain-gorges, are not here con- 
cerned. Such a mingling occurs it is true under certain conditions ; 
but in the general physiognomy of the flora the distinction between 
the shore and inland plants holds good. The same shore plants 
that are distributed far and wide over the Pacific here present 
themselves ; and although some of them extend far inland, where 
the scantily-vegetated plains descend to the coast, this does not 
deprive them of the right of being still regarded as littoral 
plants. 

Still, when we look at a fairly complete list of the shore-plants 
of Fiji, numbering in all about eighty, we perceive that about two- 
thirds of them also occur inland, either in Fiji or in some other 
tropical region ; and if we reflect that many of the residue are 
plants of the mangroves that would not be found inland except 
under estuarine conditions, it becomes evident that with this 



42 A NATURALIST IN THE PACIFIC CHAP. 

reservation there are very few littoral plants in Fiji that do not at 
times leave the coast. 

Caesalpinia Bonducella may be taken as a type of those shore- 
plants that stray far away from the coast, even into the interior of 
continents, since in India it reaches the Himalayas. Although 
Terminalia Katappa and Calophyllum Inophyllum often owe 
their existence inland in different parts of the tropics to man's 
agency, this cannot be said of most others, as Cassytha filiformis, 
Casuarina equisetifolia,Cycas circinalis, Ipomea pes caprae,Pandanus 
odoratissimus, Premna tahitensis, Tacca pinnatifida, Tephrosia 
piscatoria, Vitex trifolia, &c., when they occupy the extensive 
inland plains that slope to the coasts on the lee sides of the large 
islands of Fiji. Plants, like Hibiscus tiliaceus, are found in a 
Pacific island almost as frequently away from the beach as on the 
beach itself; and this is true of most other regions of the tropics 
where it occurs. 

Other plants that appear to be altogether confined to the 
sandy beach in Fiji, break away on rare occasions from their 
usual station and appear on the bare rocky summits of hills near 
the coast, even though the hill-slopes are densely wooded. On 
such bare hilltops in Vanua Levu, varying from 500 to 1,100 feet 
in elevation, one is surprised at times to find shore creepers and 
climbers like Canavalia obtusifolia and Derris uliginosa associated 
with other beach-plants more frequently found inland, such as 
Tephrosia piscatoria and Vitex trifolia, and in the company of 
climbing species of Morinda and of small trees of Fagraea 
Berteriana. When the "talasinga" (sun-burnt) districts, as the 
Fijians term the plains on the north sides of the islands, extend a 
long distance from the coast into the heart of the island, they carry 
with them their peculiar vegetation and the intruding beach-plants 
up to considerable elevations above the sea. We then find 
familiar beach-plants like Cerbera Odollam and Ipomea pes caprse 
growing far inland at heights of 1,000 feet and over above the sea. 
(See Notes 20 and 21.) 

One is never quite sure of the behaviour of shore-plants in Fiji 
when the " talasinga " plains lie behind the beach, since even 
Scaevola Kcenigii, usually a steadfast beach-plant, occurs at times 
some miles inland. (See Notes 20 and 55.) There are, however, 
a few that never came under my notice inland, such as Pemphis 
acidula, Triumfetta procumbens, and-Tournefortia argentea. The 
extension of sea-coast plants for any distance inland depends 
a good deal on the occurrence of scantily-vegetated plains, or of 



v THE FIJIAN STRAND-FLORA 43 

scrub-covered, rolling country at the back of the beaches ; and 
doubtless that which I have described in the case of Fiji is to 
be found in other tropical coast-regions. Professor Schimper 
informed me by letter that he had noticed a similar inland exten- 
sion of the shore-plants in the Seychelles I have only here 

touched on this subject. In Notes 20 and 21 the reader will find 
further details of the inland extension of the beach-plants, and in 
Note 22 is given a general account of the " talasinga " plains, 
in which the wandering beach-plants mingle with the peculiar 
vegetation of the plains themselves. Covered with reeds and 
bracken, and dotted over with clumps of Casuarinas and Acacias, 
with the Cycad and Pandanus distributed irregularly over their 
surfaces, such level districts possess, as remarked by Seemann, 
a South Australian look. 



THE GROUPING OF THE FIJIAN LITTORAL PLANTS. 

The littoral plants readily divide themselves into three princi- 
pal groups as concerning their station, namely : 

(a) The " beach-formation," typically exhibited on the whitish 
calcareous beaches of reef-bound coasts. 

() The " mangrove-formation," found at intervals all along the 
coasts, but most fully developed at the estuaries, and for the most 
part occupying flats regularly overflown by the tide. 

(c) The " intermediate formation," comprising the plants of the 
tracts between the beach and the mangrove-swamp and at the 
borders of the swamps. 

This grouping does not differ materially from that adopted by 
Professor Schimper in the instance of the Indo-Malayan strand- 
flora. (See Note 23.) 

To the beach-formation belong, amongst the trees and shrubs, 
Barringtonia speciosa, Calophyllum Inophyllum, Guettarda 
speciosa, Pemphis acidula, Scaevola Kcenigii, Tournefortia 
argentea, &c., and amongst the creepers and procumbent plants, 
Canavalia obtusifolia, Ipomea pes caprse, Triumfetta procumbens, 
&c. To the mangrove-formation belong the Asiatic and the 
American species of Rhizophora, and species of Bruguiera, Carapa, 
Lumnitzera, &c. Amongst the trees that gather around the 
borders of the mangrove-swamp, constituting the intermediate 
formation, occur Barringtonia racemosa, Excaecaria Agallocha, 
Heritiera littoralis, Hibiscus tiliaceus, and several other species, all 
of them being equally at home on the sandy beach, at the border 



44 A NATURALIST IN THE PACIFIC CHAP. 

of a mangrove-swamp, and on the banks of an estuary. The 
climbers, such as Entada scandens, Mucuna gigantea, Derris 
uliginosa, &c., belong more to the mangrove and to the inter- 
mediate formations than they do to that of the beach. Referring 
the reader to the more complete lists given in Note 24, I may 
remark that it is not always possible to distinguish sharply between 
the three formations, since some of the plants belong to two, and a 
tree like Cerbera Odollam may, in different localities, be referred to 
all three formations. The general distinction, however, prevails in 
the physiognomy of the coast-flora. 

The mangrove-formation comprises, it may be pointed out, 
many plants other than mangroves, plants that find a home in the 
mangrove-swamps of Fiji, either within their limits or at their 
borders. It presents, indeed, a world in itself. When the man- 
groves establish themselves in a new locality they carry along 
with them a host of hangers-on, both plants and animals, that only 
find a home under the favourable conditions of a mangrove- 
swamp. Thus, the absence of the mangrove-formation from a 
Pacific island deprives its littoral flora of many very striking 
features. For this reason the Tahitian shore-flora must seem to a 
botanist coming from Fiji comparatively tame and monotonous ; 
whilst that of Hawaii, for this and for other reasons to be subse- 
quently mentioned, is still less interesting, and scarcely even gives 
a character to the coasts. 

We are now, therefore, prepared to learn that a large number 
of the plants other than true mangroves, that thrive in or around 
the Fijian mangrove-swamp, are not to be found in those Poly- 
nesian islands where true mangroves do not exist ; and that a law 
of association here exists. Many of the plants of the intermediate 
formation are so closely bound up with the mangroves in their life- 
conditions that they are not to be found where the mangroves are 
absent, even though their seeds or fruits are pre-eminently fitted 
for dispersal by the currents. The influence of " station " here 
rules supreme. This matter will be treated more in detail when 
discussing the Tahitian and Hawaiian strand-floras in Chapters 
VI. and VII. 



THE MODES OF DISPERSAL OF THE FIJIAN STRAND-PLANTS. 

The predominant influence of the currents having been already 
established, there remains for consideration the distribution of the 
floating capacity of the seeds or fruits among the different forma- 



THE FIJIAN STRAND-FLORA 45 

tions. One can say that almost without exception the seeds or 
fruits or seedlings of the mangrove and intermediate formations 
float for long periods. In the case of some of the true mangroves, 
as in Rhizophora and in Bruguiera, where germination takes place 
on the tree, it is the seedling that floats, whilst in others, as in 
Carapa and Lumnitzera, it is the seedvessel that floats. The 
plants with non-buoyant seeds or fruits that belong to the littoral 
flora are all confined to the beach formation, but they do not form 
more than a sixth of the total. Almost all the " good floaters " of 
the beach-plants are widely spread over the shores of the Pacific 
and of much of the tropics, and include such familiar species 
as Barringtonia speciosa, Caesalpinia Bonducella, Terminalia 
Katappa, and many others mentioned in the lists of Notes 2 
and 24. 

When, however, we come to the dozen or so of beach-plants 
that possess seeds or fruits with little or no floating power, we find 
that several of them have a limited distribution in the Pacific, such 
as Acacia laurifolia, Drymispermum Burnettianum, Eugenia Richii, 
&c., whilst others, such as Casuarina equisetifolia, Tephrosia pisca- 
toria, Triumfetta procumbens, and Wikstrcemia foetida, are widely 
spread. This small non-buoyant group of the beach-plants has a 
nondescript appearance, and it is here that the inland flora is most 
likely to make its influence felt by additions to the number. It is 
here indeed that the littoral floras of the tropics mostly differ, the 
accessions from the inland flora varying in each region. It is in 
fact the zone of change. 

A number of these plants, such as the species of Drymispermum, 
Eugenia, and Wikstrcemia, have probably been dispersed by frugi- 
vorous birds ; whilst others, like Triumfetta procumbens, possess 
fruits that might have been transported in birds' plumage. From 
the frequency with which Tephrosia piscatoria is associated on 
hilltops in Fiji with Fagraea Berteriana and climbing species 
of Morinda that are well suited for dispersal by frugivorous birds, 
it seems likely that it is also distributed by birds fond of a drier 
diet. It is possible that the Polynesians, who much value the wood 
of Casuarina equisetifolia, have often assisted in dispersing the tree. 

The following is a summary of the contents of the chapter. 

(i) The extension inland of the Fijian strand-flora is to be 
attributed to the xerophilous organisation of the plants, and to the 
exceptionally favourable conditions that are offered to such plants 
on the plains, and in other scantily vegetated localities, lying 
usually on the drier sides of the larger islands. 



46 A NATURALIST IN THE PACIFIC CH. v 

(2) Excluding the mangroves and the plants associated with 
them in the coast-swamps, there are few littoral plants of the 
islands of the tropical Pacific that do not extend inland in one 
region or another. 

(3) The Fijian shore-plants can be rudely arranged in three 
groups, those of the mangrove-swamp, those of the sandy beach, 
and those of the intermediate districts, the last including those 
plants that occur typically at the borders of a mangrove-swamp, 
though some of them can thrive equally well on a beach. 

^ (4) There is a law of association connecting many plants with 
a mangrove-swamp in such a manner that when the true man- 
groves are not represented in a Polynesian group, as in Tahiti or 
in Hawaii, the plants in question are also absent, notwithstanding 
that in many cases, such as those of Clerodendron inerme and 
Heritiera littoralis, they possess seeds or seedvessels of great 
floating power. 

(5) The fruits or seeds or seedlings, as the case may be, of the 
plants of the mangrove-swamp and of the bordering districts float 
almost without exception for long periods. This is true also of 
five-sixths of the beach-plants, whilst the remainder owe their 
dispersal chiefly to birds. 

(6) The small non-buoyant group of the beach-plants repre- 
sents that portion of the strand-flora that is most likely to be 
recruited from the inland flora. It is here that exists the zone of 
change ; and it is in this respect that the littoral floras of the 
tropics differ principally amongst each other, the recruits from 
inland varying naturally with the floras of different regions. 



Though it does not come within my plan to discuss the littoral 
floras of the adjacent smaller groups of Tonga and Samoa, it may 
be remarked that they reflect most of the principal features of the 
strand-flora of Fiji. In particular it may be observed that they 
possess the mangrove-formation, but to a more limited extent. 
Both own the mangrove genera Rhizophora and Bruguiera, whilst 
Carapa is also found in Tonga. The intermediate formation is 
represented in Tonga by Clerodendron inerme, Excsecaria Agal- 
locha, and Heritiera littoralis ; whilst in Samoa we find, besides 
the first-named species, Barringtonia racemosa and Scirpodendron 
costatum. In both the beach-formation is well represented. 



CHAPTER VI 

THE TAHITIAN STRAND-FLORA 
{From materials siipplied mainly by the work of Drake del Castillo) 

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. 

JUST as the littoral plants of Fiji may be regarded as typical of 
Western Polynesia, so the strand-flora of Tahiti, or, rather, of the 
Tahitian Islands, may be considered as representing Eastern Poly- 
nesia. We have thus the Tahitian area, comprising generally the 
Cook and Austral Groups, the Society Islands, the Paumotus, and 
also the Marquesas, as contrasted with the Fijian area, including the 
neighbouring Samoan and Tongan groups. For the sake of brevity 
the terms Fiji and Tahiti are often used as equivalents of the entire 
areas (see Note 25). 

The littoral flora of this part of the Pacific lacks the mangroves 
and most of the plants that are associated in the Fijian region 
with a mangrcve-swamp, either at its borders or within its interior. 
Thus we miss here the true mangroves of the genera Rhizophora, 
Bruguiera, Carapa, and Lumnitzera, as well as the accompanying 
trees and shrubs, such as Barringtonia racemosa, Excaecaria Agal- 
locha, and Heritiera littoralis. The climbers and straggling plants 
that are so characteristic of the borders of the mangrove-creeks in 
Fiji proper are also wanting, such as Clerodendron inerme, Derris 
uliginosa, and Smythea pacifica ; and we do not find in the Tahi- 
tian region the Giant-Sedge (Scirpodendron costatum) that is so 
common in the mangrove-swamps of Fiji, and occurs also in 
Samoa. 

It is not at first sight easy to account for the absence from 
Tahiti of the mangrove-formation and of so many of the plants 



48 A NATURALIST IN THE PACIFIC CHAP. 

that grow at the borders of a mangrove-swamp in Fiji. Their 
absence can scarcely be due to the want of suitable stations, as is 
indicated by the common occurrence in the Tahitian coast-marshes 
of Chrysodium aureum, the Great Swamp-fern, that not only 
abounds in the mangrove belts of Fiji, Tonga, and Samoa, but is 
associated with mangrove-swamps over much of the tropical zone. 
Nor can it be said that the currents are ineffective, or that the 
seeds or fruits of the missing plants possess, as a rule, insufficient 
floating powers. Most of the plants of the Tahitian beaches hail, 
like those of Fiji, from Malaya, and have been brought through the 
agency of the currents ; and many of the absent littoral plants that 
have the same home, such as Heritiera littoralis and Clerodendron 
inerme, have fruits or seeds just as capable of floating unharmed 
over the same extent of ocean. It is not any defect in floating- 
power that has prevented the establishment of two such plants in 
the Tahitian area. Entada scandens, which in some parts of the 
world is a typical climber of the mangrove-formation, and in other 
places thrives well in the absence of mangrove-swamps, has only 
been recorded from Rarotonga in this region by botanists, but I 
believe Wyatt Gill refers to its occurrence in Mangaia in one of 
his books. 

On the other hand, it is likely that the floating seedlings of 
Rhizophora and Bruguiera, which represent the only means of dis- 
persal by the currents at the service of these mangroves, would not 
arrive at Tahiti in a condition favourable for the establishment of 
the plants. My observations, which are described in Chapter XXX., 
go to show that, though the seseedlings will float uninjured in still 
sea-water for months, they will not withstand prolonged sea-buffet- 
ing. These two genera of mangroves, it is most important to 
remember, supply the pioneers and the principal components of a 
mangrove-swamp in the Western Pacific. Where they fail to 
establish themselves, the requisite conditions for the large number 
of plants and animals that find their home in and around a man- 
grove-swamp would not be provided. We thus perceive that the 
absence from the Tahitian coast flora of several plants that are 
associated in Fiji with the mangrove-swamps depends on a law of 
association, which has already been referred to in the preceding 
chapter, and is not concerned with incapacity for dispersal by 
currents (see Note 26). 

Whilst the Tahitian coast flora does not, therefore, possess the 
plants of the mangrove-swamp and its vicinity, it includes most of 
the typical beach-trees of the coral islands and reef-fronted coasts of 



vi THE TAHITIAN STRAND-FLORA 49 

other parts of the South Pacific. Thus we find here on the sandy 
beaches Barringtonia speciosa, Calophyllum Inophyllum, Cerbera 
Odollam, Hernandia peltata, Guettarda speciosa, and numerous other 
plants that are indicated by the letter T in the list of Fijian littoral 
plants given in Note 2. The total number of Tahitian shore-plants 
is thus considerably less than that of Fiji (there are about 55 m 
Tahiti and about 80 in Fiji) ; but in its turn, as will subsequently 
be shown, it is much larger than that of Hawaii, where the number 
is about 30. 

Quite three-fourths of the strand-flora of this region have 
buoyant seeds or seedvessels capable of floating for long periods ; 
and there is no difficulty in assigning by far the greater share in 
the stocking of the beaches with their plants to the agency of the 
currents. The currents in their operations have indeed carried the 
fruits or seeds of many of these plants across the South Pacific as 
far as the islands extend, namely, to Ducie Island and to Easter 
Island. There are few more significant proofs of the efficacy of the 
currents in distributing plants over the Pacific than the discovery, 
by Mr. Arundel, of Barringtonia speciosa in Ducie Island in 
association with Tournefortia argentea (Challenger, Botany, 
III. 116). 

The residue of the Tahitian coast flora possessing fruits or seeds 
that are unsuited for dispersal by currents includes such plants as 
Heliotropium anomalum, Triumfetta procumbens, Tephrosia pisca-t 
toria, Wikstrcemia fcetida, &c. The small nucules of the first-named 
are perhaps dispersed by granivorous birds ; the fruits of Triumfetta 
are probably transported in birds' plumage ; those of Wikstrcemia 
are distributed by frugivorous birds ; and the seeds of Tephrosia 
may be dispersed like those of Heliotropium. 

The recruits or intruders from the inland flora do not appear to 
be numerous or to give any special character to the shore flora. 
(See Note 27.) 

From not having a personal acquaintance with this region it is 
not possible for me to discuss the extension of the shore-plants 
inland except in a general way. From the pages of the work of 
Drake del Castillo we can, however, infer that several plants such as 
Cassytha filiformis, Cerbera Odollam, Colubrina asiatica, Hernandia 
peltata, Morinda citrifolia, and Pandanus odoratissimus have 
-extended inland to the mouths of the Tahitian valleys, and have 
ascended the lower slopes of the hills that lie near the coast. 
Others, like Caesalpinia Bonduc, Gyrocarpus Jacquini, and Ochrosia 
parviflora, have climbed far up the mountain-sides to elevations of 

VOL. Ii E 



50 A NATURALIST IN THE PACIFIC CH. vi 

from 2,000 to 2,400 feet above the sea. It is also evident from 
Mr. Cheeseman's memoir on the Rarotongan flora that coast plants 
also stray inland in that island. In an island like Raro tonga, where 
a sorry substitute for a mangrove-swamp exists in the form of a few 
coastal muddy places occupied by Vitex trifolia and Sesuvium 
Portulacastrum, Entada scandens takes to the hills ; and thus it is 
that in this island it is most abundant in the interior, climbing to 
the tops of the highest trees and " covering acres of the forest with 
a dense canopy of green." 



Summary of the Chapter. 

(1) The Tahitian region possesses most of the plants that 
frequent the sandy beaches of the Pacific islands. 

(2) But it lacks the mangroves and the associated plants of the 
mangrove-swamp. 

(3) It also wants many of the plants that grow in the vicinity of 
such swamps. 

(4) But since the plants last-mentioned often possess 
fruits or seeds capable of being carried great distances by the 
currents, their absence is to be attributed to the necessary 
conditions being lacking on account of the failure of the 
mangroves. 

(5) Most of the beach plants, however, owe their existence in 
this region to the transport of their buoyant fruits or seeds by 
the currents. 

(6) The negative features of the Tahitian strand-flora are 
mostly to be connected with the absence of Rhizophora and 
Bruguiera, the pioneers of the mangrove-swamp ; and their absence 
is, in turn, to be attributed to the inability of their floating 
seedlings to reach this region in a fit condition for establishing 
themselves. 



CHAPTER VII 

THE HAWAIIAN STRAND-FLORA 

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. 

COMPARED with the rich strand-flora of Fiji, that of Hawaii 
presents but a sorry aspect In the number of species (30) it does 
not amount to half; whilst it lacks the great mangrove-formation 
arid the luxuriant vegetation accompanying it that gives so much 
character to the shores and estuaries of Fiji, Strangely enough, it 
is also deprived of most of the familiar trees that, whether in 
foliage, in flower, or in fruit, form the chief attraction of the sandy 
beaches of the Pacific islands. 

Neither the mangroves, therefore, nor the plants of the inter- 
mediate formation, are to be found in Hawaii ; and when we 
reflect that the absentees from the beach formation include most of 
the trees, under the shade of which the visitor to the Pacific islands 
can nearly always find protection from the fierce rays of a tropical 
sun, it cannot be a matter of surprise that this littoral flora has 
such a poverty-stricken appearance. We look in vain for such 
shady beach trees as Barringtonia speciosa, Terminalia Katappa, 
and Hernandia peltata ; and we are lucky if we find some small 
trees under which we can obtain a scanty shade. 

I have been speaking, of course, of the indigenous shore-plants, 
those that have arrived at these islands without the assistance of 
man. Yet it must be added that the existing littoral flora does 
include some of the missing indigenous trees, though rarely in any 
number. There is, however, scarcely one of them that is regarded 
by Dr. Hillebrand as having formed part of the original flora. 
That botanist would indeed rob the present beach flora, scanty as 
it is, of most of its conspicuous plants, as far as their claims to be 

E 2 



52 A NATURALIST IN THE PACIFIC CHAP. 

considered indigenous are concerned. Dr. Hillebrand indeed 
includes Calophyllum Inophyllum, Hibiscus tiliaceus, Thespesia 
populnea, Morinda citrifolia, Cordia subcordata, and Pandanus 
odoratissimus in the present Hawaiian flora, and nearly all of them 
are to be found at times at the coast as well as inland ; but he 
regards all, excepting the last-named, as having been introduced 
by the aborigines. I was not inclined at first to go quite so far as 
Dr. Hillebrand in this direction ; but he carefully considered the 
case of each individual plant, and, remembering his sojourn of 
twenty years in the islands, his authority cannot be lightly put 
aside. In the list of Hawaiian strand-plants given in Note 28 
there are several species not always littoral in the group, but 
typically littoral in other tropical regions. One species, Ipomea 
glaberrima, Boj., has not been recorded before from these islands. 
A strong reason in favour of the contention of this botanist is 

,/ that all the trees above-named are useful in some way to the 
natives ; and, indeed, when we look at the works dealing with the 
floras of the islands of the South Pacific, we observe that in almost 
all the groups one or other of these six trees bears the reputation 
of having been introduced by the aborigines. All of them in their 
turn lose their fame as truly indigenous plants in some group or 
other. The occurrence of two or three useless South Pacific 
beach trees, that are known to be dispersed by the currents, in the 
indigenous strand-flora of Hawaii, would go far to invalidate 
Dr. Hillebrand's argument, since the six trees in dispute are also 
known to be dispersed by the currents. But such trees are not to 
be found ; and we look in vain for trees like Cerbera Odollam, 
Guettarda speciosa, Gyrocarpus Jacquini, and Hernandia peltata, 
that are spread far and wide over the beaches of the South Pacific. 
It is also of interest to notice how trees like Morinda citrifolia 

\/ and Terminalia Katappa, concerning the non-indigenous character 
of which there can be but little doubt, are in our own day acquiring 
a littoral station. The second is not even regarded by Dr. Hille- 
brand as having been introduced by the natives, but is referred by 
him to the European epoch. After having been extensively 
planted, it is now, as I found, becoming a littoral tree on the coast 
of Oahu, and supplies its buoyant fruits in a regular way to the 
beach drift. Its native name of Kamani is merely that of 
Calophyllum Inophyllum. All the six trees in dispute are known 
in Hawaii by the names by which they are distinguished far and 
wide over the South Pacific, a fact of which the reader may satisfy 
himself by referring to my paper on Polynesian plant-names. The 



vii THE HAWAIIAN STRAND-FLORA 53 

Hawaiians, when their ancestors abode in the South Pacific, must 
have been well acquainted with one or other of the prevailing 
names of Terminalia Katappa (Talie, Tara, &c.) ; but it had 
lapsed in the memory of the race when the Europeans introduced 
the tree into Hawaii. 

It may be added in this connection that Dr. Hillebrand 
weakens his argument by regarding Pandanus odoratissimus as v 
of pre-aboriginal origin or as truly indigenous. Like the other six 
trees in question, its fruits are known to be capable of dispersal 
far and wide by the currents ; and if this species of Pandanus is 
indigenous, we are obliged to assume that its fruits were first 
brought by the currents. That being so, we cannot exclude the 
probability of the currents having been also effective with several 
of the other plants regarded by Hillebrand as of aboriginal 
introduction, more especially those with large fruits like 
Calophyllum Inophyllum, and Cordia subcordata, where the 
alternative agency of frugivorous birds would be impracticable, at 
least over a wide extent of ocean. Pandanus odoratissimus is, 
as I venture to think, a tree that was introduced ages since by 
the aborigines. Next to the Coco palm, few trees have been 
more utilised by island-peoples, more particularly perhaps in the 
ruder stages of their history. 

This point has been discussed at some length, because on the 
correctness of Dr. Hillebrand's view depends the explanation to 
be subsequently given of the origin of the shore-flora of Hawaii. 
Though differing in some details, my observations on the 
Hawaiian coast plants, which are given in Note 29, tend to 
strengthen his contention. 

I now return to the consideration of some of the negative 
features of the Hawaiian strand-flora, and will allude first to the 
absence of the mangroves and of the numerous other plants that 
live in and around a mangrove-swamp. This cannot be connected 
with a total absence of suitable stations. Although it is true that 
there are but few large rivers and but few suitable localities, yet 
such localities exist. The shores of Hilo Bay might readily have 
been the home of a mangrove-swamp ; and one can point to 
different places on the coast of Oahu, such, for instance, as Pearl 
Harbour, which in Fiji would have been occupied by a luxuriant 
growth of mangroves. The same argument applies to the 
missing beach trees, such as Barringtonia speciosa, Hernandia 
peltata, Guettarda speciosa, &c., that adorn the beaches of many a 
coral island or of many a coral-bound coast in the South Pacific. 



54 A NATURALIST IN THE PACIFIC CHAP. 

Although in a large island like Hawaii with its lava-bound coasts 
but few white calcareous beaches exist where we might expect to 
find such a flora, yet such beaches occur wherever the scanty coral 
reefs are found off the coast ; and it is just in those localities, as is 
pointed out in the account of my observations in Note 29, that the 
" plantes madreporiques " of the French botanists, the plants of 
the coral atoll and of the reef-girt coast, make their best 
endeavours to establish themselves. In other islands like Oahu, 
where coral reefs are more developed, calcareous beaches are more 
frequent, and there the few " madreporic " plants of Hawaii make 
a home. 

Nor can the deficiencies in the Hawaiian strand-flora be 
connected with climatic conditions. That its meagre character 
cannot be so explained is indicated by the manner in which the 
Indo-Malayan shore-plants have pushed their way northward on 
the western side of the Pacific to the Liukiu and Bonin Islands. 
Here in latitude 26-27 N. we find several Fijian littoral trees and 
shrubs, such as Hernandia peltata, Pemphis acidula, Pongamia 
glabra, Sophora tomentosa, Terminalia Katappa, Tournefortia 
argentea, &c., that do not occur in Hawaii, although this group is 
some degrees nearer the equator, namely, in latitude 19-22 N. 
They are accompanied by the mangroves (Rhizophora, Bruguiera, 
&c.) in strength as far as South Liukiu in latitude 25 N. ; but we 
learn from Dr. Warburg that the mangroves thin off further 
north, though they reach to South Japan, where Doderlein found 
in latitude 32 N. solitary examples of Rhizophora mucronata. 
These interesting facts of distribution, which are taken from 
Schimper's work on the Indo-Malayan shore-plants (pp. 85, 90), 
show us that we can scarcely look to climatic conditions for the 
explanation of the absence of mangroves and of many other 
tropical littoral plants from Hawaii. We form the same opinion 
when we regard the extension northward of the mangrove- 
formation on the American coasts of the North Pacific Ocean. 
According to the account of Dr. Seemann given in the " Botany of 
the Voyage of H.M.S. Herald!' the mangroves with the coco-nut 
palm, and many other littoral plants common on the western 
shores of tropical America, reach their northern limit a little north 
of Mazatlan within the mouth of the Gulf of California in latitude 
24 38' N. The parallel of 25 N. latitude, as indicated in Drude's 
Atlas, probably represents the extreme northern limit, which is 
thus five or six degrees north of the latitude of the large island 
of Hawaii. 



vii THE HAWAIIAN STRAND-FLORA 55 

Neither can the explanation be found in the deficient floating 
powers of the seeds or seedvessels of many of the "absentees." 
Those of Barringtonia speciosa, Guettarda speciosa, Heritiera 
littoralis, the two species of Terminalia, &c., possess great buoyant 
powers equal to, and probably often exceeding, those of the plants 
that, like Ipomea pes caprae, have succeeded in establishing them- 
selves in Hawaii. One has only to look at the lists giving the 
results of flotation experiments in Notes 2 and 3, in order to 
realise that there are very few of the " absentee " littoral plants, 
the non-existence of which in Hawaii could be attributed to 
deficient floating powers of the fruit or seed. Being able to float 
unharmed for months, and in several cases even for years, the 
seeds or fruits of the shore-plants unrepresented on the Hawaiian 
beaches have been carried far and wide by the currents over the 
tropical Pacific even to Ducie and Easter Islands, that is, as far as 
the islands extend. 

The only plants about which one could express a doubt 
concerning their ability to reach Hawaii through the agency of 
the currents, and to establish themselves there, are the true 
mangroves of the genera Rhizophora and Bruguiera. Since 
germination takes place on the tree, it is only through the 
floating seedlings that they could reach these islands ; but, as 
shown in Chapter XXX., it is doubtful whether the seedlings would 
be in a fit condition for reproducing the plant after such a long 
oceanic voyage. If they had been as successful in establishing 
themselves in Hawaii as they have been in the Liukiu Islands, 
which lie in latitude a few degrees farther north, these two species 
through their reclaiming agency would alone have prepared the 
way for the whole mangrove formation. We have seen in the 
preceding chapter that the absence of the mangrove formation 
from Tahiti appears to be mainly due to the failure of the 
pioneer species of Rhizophora and Bruguiera to establish them- 
selves there. This evidently also applies to Hawaii, the cause of 
their exclusion being connected neither with climate nor with 
station, but as in Tahiti with the general unfitness of the floating 
mangrove seedlings for crossing broad tracts of ocean without 
injury to the growing plantlet. 

With regard, however, to the bulk of the " absentee " littoral 
plants, those of the beach-formation, no such incapacity on the 
part of the buoyant seed or fruit can be accepted. These plants, 
which have reached Tahiti in numbers, have in the mass failed to 
reach Hawaii. It will, therefore, be of interest to glance at the 



56 A NATURALIST IN THE PACIFIC CHAP. 

character of the fruits of the " absentee " trees, which a traveller 
fresh from a visit to the coral islands and reef-girt coasts of the 
South Pacific sadly misses on the Hawaiian beaches. We notice 
in the first place that the absent trees, such as Barringtonia 
speciosa, Cerbera Odollam, Guettarda speciosa, Heritiera littoralis, 
Terminalia Katappa, &c., have large fruits which could only have 
been carried to Hawaii by the currents, the agency of birds being 
quite out of the question. On the other hand, almost all the 
littoral plants of Hawaii, whether trees, shrubs, or herbs, which 
are regarded as truly indigenous by Mann, Hillebrand, and other 
Hawaiian botanists, have only small fruits or seeds available for 
dispersal, from which the agency of birds cannot, on the point or 
size, be excluded. Amongst these shore plants possessing buoyant 
seeds or fruits are Cassytha filiformis, Colubrina asiatica, Ipomea 
pes caprae, Scaevola Kcenigii, Vigna lutea, and Vitex trifolia; whilst 
amongst the plants with non-buoyant fruits or seeds are to be 
reckoned Heliotropium anomalum, H. curassavicum, Tephrosia 
piscatoria, Tribulus cistoides, &c. The seeds or seedvessels of the 
plants of the buoyant group possess great floating powers ; and it 
seems at first sight scarcely credible that the currents which have 
failed to establish Barringtonia speciosa, Guettarda speciosa, and 
the other trees that through this agency have often found a home 
on the remotest islands of the Pacific, should have succeeded in 
the instances of plants like Scaevola Kcenigii and Vitex trifolia. 

It would indeed almost seem that in nearly all cases where it 
would be impossible in point of size for a bird to transport the 
fruit or seed of a shore-plant to Hawaii, such a plant is not to be 
found in the strand-flora of that group, even though it is well 
adapted for dispersal by the currents. Many of the littoral trees 
missing from the Hawaiian coast-flora, having large buoyant 
fruits, come into this category ; and grave suspicion is thus 
apparently cast on the agency of the currents in the case of the 
plants with small fruits and seeds that really compose the strand- 
flora, even when their capacity for sea- transport has been well 
established by observation and experiment. The efficacy of the 
currents would thus seem to be called into question for the whole 
littoral flora of Hawaii. 

If, however, we were to adopt such a sweeping conclusion we 
should be led into an error. It is pointed out in the following 
chapter that nearly all these large-fruited beach trees that are 
found far and wide over the South Pacific, but are absent from 
Hawaii, do not occur as indigenous plants in America. If, there- 



vii THE HAWAIIAN STRAND-FLORA 57 

fore, the fruits of such Old World littoral trees as Barringtonia 
speciosa, Cerbera Odollam, Guettarda speciosa, Ochrosia parviflora, 
Terminalia Katappa, &c., that could be dispersed only by the 
currents, have failed to reach Hawaii, it is essential to remember 
that they have also failed to reach America. This suggests that 
Hawaii may have received some of its littoral plants from America 
through the agency of the currents ; and it is shown in the 
following chapter that, as a rule, when a South Pacific plant 
with buoyant fruits or seeds is not found in America, it is equally 
absent from Hawaii. The question thus acquires quite a different 
aspect, and we shall accordingly have to regard tropical America 
in the next chapter as a possible centre of diffusion of littoral 
plants over the globe, a centre possibly as important as that 
connected with the tropics of the Old World. 

Although, however, the currents have played a part in stocking 
the Hawaiian beaches with their plants, their share in the work has 
been unimportant, and the number of plants concerned is limited. 
If we take away the seven or eight littoral plants introduced by the 
aborigines, as well as the three endemic species as indicated in the 
list in Note 28, and then remove from the residue the plants with 
small fruits or seeds possessing little or no buoyancy, there remain 
only the following eight species, the presence of which in Hawaii 
might be attributed to the currents, namely, Caesalpinia Bonducella, 
Cassytha filiformis, Colubrina asiatica, Ipomea glaberrima, Ipomea 
pes caprae, Scaevola Kcenigii, Vigna lutea, and Vitex trifolia. Of 
these plants, three species, those of Cassytha, Scaevola, and Vitex, 
possess fruits that would be likely to attract frugivorous birds, and 
are in some cases known to be dispersed by them (see Chapter 
XI II.); so that we are not in these instances restricted to the agency 
of the currents. With the other five the currents offer the readiest 
explanation, but, as is indicated in the cases of Caesalpinia Bondu- 
cella and Ipomea glaberrima (Chapter XVII.), it is quite possible 
that birds have occasionally intervened. Altogether we may infer 
that in stocking the Hawaiian beaches with their littoral plants the 
currents have taken a subordinate part. 

Coming to the Hawaiian littoral plants having seeds or fruits 
that have no floating power, we find that they present a motley 
group. It has been already remarked that this is the group of 
shore plants that derives most recruits from the inland flora, and 
that it is in this group that the differences between the shore-floras 
of tropical regions find their expression. Yet a very odd collection 
of plants is here exhibited. Sometimes the beach-flora is composed 



S 8 A NATURALIST IN THE PACIFIC CHAP. 

in great part of these plants ; and a sorry spectacle is presented by 
a beach possessing such plants as Gossypium tomentosum, Helio- 
tropium anomalum and H. curassavicum, Lipochaeta integrifolia, 
Tephrosia piscatoria, Tribulus cistoides, &c. Yet to the student of 
plant-distribution such a motley collection would be full of 
suggestiveness. From the circumstance that species of Cuscuta, 
Jacquemontia, and Lipochaeta, that are peculiar to the Hawaiian 
Islands, have made their homes on the beach, he would infer that 
since Nature has been compelled to borrow from the endemic 
inland flora, there has been some difficulty in stocking the beaches 
with their plants. The occurrence of endemic species amongst the 
strand-plants would be viewed by him as especially indicating 
incapacity on the part of the ocean currents. 

Yet in the quantities of drift timber, showing evidence of many 
months and probably even of years of ocean-transport, to be seen 
stranded on the weather coasts of these islands, the observer discerns 
undoubted evidence of the efficacy of the ocean currents. But 
what he finds are huge stranded pine logs of "red- cedar" and 
" white-cedar " from the north-west coasts of America. He may 
search the drift for days together, as I have done, and discover no 
tropical fruits or seeds except such as could be supplied by the 
present Hawaiian flora. The subject of this drift is especially 
discussed in Note 30 ; and it need only be mentioned here that it 
is not improbable that, as shown in the next chapter, some drift may 
reach Hawaii from tropical America under exceptional conditions, 
and that its presence is masked by the Oregon drift. 

The agency of the drifting log in carrying small seeds in its 
crevices would be effectual in the instance of plants from the 
temperate coasts of North America. For example, the nutlets of 
Heliotropium curassavicum, which have no buoyancy, might easily 
be washed, together with sand, into the cracks of a pine log stranded 
temporarily on the Oregon coast where this plant occurs. The 
modus operandi was brought home to me when examining the 
drift brought down by the Chancay River on the coast of Peru. 
Here I found this species of Heliotropium growing on the margin 
of a swamp near some stranded logs, that would probably be 
carried out to sea when the river was next in flood. 

It is probable, I may add, that the seeds or fruits of some of 
the plants of the non-buoyant group of the Hawaiian littoral flora 
may be dispersed in birds' plumage. For instance, the spiny 
fruits of Tribulus cistoides sink in sea-water ; but they are well 
suited for entangling themselves in birds' feathers. 



vii THE HAWAIIAN STRAND-FLORA 59 

It is possible that the hairy seeds of Gossypium tomentosum 
may have been thus distributed ; but there is much that is 
enigmatical about this plant (see Chapter XXVI). 

THE INLAND EXTENSION OF THE BEACH PLANTS OF 
HAWAII. When we regard the inland extension of littoral plants 
in Hawaii, we get fresh indications of the meagreness of the strand- 
flora. Several of the species, as Csesalpinia Bonducella, Cassytha 
filiformis, Tephrosia piscatoria, &c., show themselves only occasion- 
ally on the sandy beaches, though they are common enough on the 
old scantily vegetated lava-flows near the coast and are often found 
miles inland. Indeed, Dr. Hillebrand not infrequently in describing 
the station only gives prominence to the situation of the plants 
away from the beaches, and places most of them on the old lava 
plains that extend inland from the coast. It is only by a detailed 
examination of extensive coast lines in these islands that I have 
succeeded in preserving to a small degree their reputation as 
beach plants. A few of them behave somewhat strangely in their 
inland station. Thus, the seeds of Caesalpinia Bonducella obtained 
from various localities showed no buoyancy in my experiments ; 
and had I not found a solitary buoyant seed in the stranded drift 
I should have inferred that this was a rule without exception. 

It is to be remarked that whilst some plants like Scaevola 
Koenigii occasionally stray a few hundred yards inland on the 
surface of the old lava-flows, others like Ipomea pes caprae and 
Vitex trifolia, that are spread far and wide over the inland plains 
of Fiji, are confined in Hawaii to the beaches and their immediate 
vicinity. Some of the plants like Hibiscus tiliaceus, Morinda 
citrifolia, and Pandanus odoratissimus, that are regarded as having 
been introduced by the aborigines, behave exactly like indigenous 
plants in the inland plains ; but this is not necessarily an indication 
of an indigenous plant in this group, since the Cactus (Opuntia* Tuna) 
and the Castor-Oil Plant (Ricinus communis) have spread all over 
the drier lower regions of the islands, whilst Aleurites moluccana, 
the Candle-Nut Tree, which has no means of reaching these islands 
without man's agency, now forms entire woods on the mountain 
slopes, usurping the place often of the original forests. . . . Further 
details relating to this subject are given in Note 31. 

The principal points in the foregoing discussion of the strand- 
flora of Hawaii may be thus summed up : 

(i) The indigenous, that is, the pre-aboriginal, strand-flora of 
this group lacks not only the mangroves and their associated 
plants, but also most of the characteristic beach-trees of the South 



60 A NATURALIST IN THE PACIFIC CH. vn 

Pacific, which [are known to owe their wide distribution in 
tropical regions to the currents. 

(2) The meagreness of the littoral flora is intensified by the 
tendency of some of the plants to extend inland and to desert the 
coasts, and by the occurrence on the beaches of peculiar species 
not found outside the Hawaiian Islands. 

(3) The absence of the mangrove formation and of so many of 
the typical beach trees of the Pacific cannot be attributed either to 
the lack of suitable stations, or to climatic conditions, or to deficient 
floating power of the seed or fruit. 

(4) As in the case of Tahiti, the mangroves and their associated 
plants are lacking because the floating seedlings of Rhizophora 
and Bruguiera, the pioneer plants of a mangrove-swamp, have 
failed to reach Hawaii in a fit condition for establishing themselves. 
The numerous plants that accompany a mangrove-swamp have 
thus been unable to find a home, though the buoyant powers of 
their fruits or seeds are often great. 

(5 ) With the missing beach-trees, however, which possess fruits 
that can float for years unharmed in sea-water, no such incapacity 
is suggested. Most of them have large fruits, which could only 
reach Hawaii through the currents. This absence from the Hawaiian 
indigenous strand-plants of most, if not all, of the large-fruited 
species, where on account of size the agency of birds is absolutely 
excluded, is very remarkable ; and it at first seems to throw grave 
suspicion on the efficacy of the currents for the whole strand-flora. 

(6) It is, however, to be noticed that these large-fruited beach 
trees have not only failed to reach Hawaii but have also failed to 
reach America. The question thus acquires quite a different aspect, 
and America becomes the possible source of most of the Hawaiian 
plants with buoyant seeds or fruits. 

(7) This subject is discussed in the next chapter ; but it is here 
shown that at their best the currents have taken but a secondary 
part in stocking the Hawaiian beaches with their plants, since 
many of the plants have non-buoyant seeds or fruits. 

(8) The drift stranded on the shores of the Hawaiian Islands is 
composed of logs from the north-west coast of North America. No 
drift from the south has been discovered ; but it is not unlikely 
that future investigators will find some seed-drift from tropical 
America. 



CHAPTER VIII 

THE LITTORAL PLANTS AND THE CURRENTS OF THE PACIFIC 

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. 

ACTIVE as the currents are in dispersing seeds and fruits over the 
Pacific, it should be remembered that those plants that owe their 
distribution to this agency are only shore-plants, and not, indeed, 
all the shore-plants, but only those with buoyant seeds or fruits. 
Even the coral atoll owes a great deal to the agency of the fruit- 
pigeon and of other birds ; for instance, their species of Ficus, 
Eugenia, and Pisonia. In order, therefore, not to form an ex- 
aggerated notion of the efficacy of the currents, it will be necessary 
to obtain some numerical idea of what they have really accom- 
plished in transporting seeds and seedvessels over the oceans in a 
state fit for successful germination on the shores upon which they 
are stranded. It is requisite to make this proviso, because in some 
cases the currents work to no purpose. Thus, the empty nuts of 
Aleurites moluccana are carried far and wide over the Indian and 
Pacific Oceans, and are stranded on the beaches of the various 
islands, as I have found myself in the cases of Keeling Atoll, Java, 
and Fiji. The Coco-de-Mer, or the Double Coco-nut Palm, is 
another apt instance. Though its fruits have been carried far and 
wide over the Indian Ocean, the species is restricted to the Sey- 
chelles. So also the acorns of various species of Quercus are 
widely but ineffectually distributed by the currents both in tem- 
perate and tropical regions. (This subject ol useless dispersal is 
dealt with in Chapter XIII.) 



62 A NATURALIST IN THE PACIFIC CHAP, 

It is essential to bear in mind at the outset that for their inland 
plants the Pacific islands can draw on the floras of a relatively 
large portion of the globe. Such plants, having as a rule fruits or 
seeds that sink in sea-water, or are incapable of floating for long 
periods, could only have arrived at these islands, where man's 
interference is excluded, through the agencies of winds and birds,, 
assisted by other lesser agencies, as those of bats, insects, &c. On 
the other hand, for their littoral plants, which are for the most part 
dispersed by the currents, the source of supply is very restricted. 
The shore-plants with buoyant seeds or fruits of the islands of the 
tropical Pacific, that are here dealt with, number only about seventy, 
and it is not likely that this number will be greatly increased, since, 
whatever may be the deficiencies in our acquaintance with the inland 
floras of these islands, we have a fairly complete knowledge of the 
strictly littoral plants. 

I do not suppose, indeed, that the number of such plants with 
seeds or fruits capable of being transported unharmed over wide 
tracts of sea would much exceed 100 for the whole Indo-Pacific 
region from India to Tahiti. Professor Schimper gives a list con- 
taining 117 tropical plants distributed far and wide over the shores 
of this region, and made up of species dispersed by currents, birds, 
and man. Taking a liberal estimate, not over two-thirds of the 
plants mentioned in this list are dispersed by currents. Then, 
again, if the flora of a coral atoll, like that of Diego Garcia or of 
the Keeling Islands, is taken as affording an index of the work 
of the currents, the number of plants dispersed by the currents 
would appear to be indeed restricted, since in either case their in- 
digenous flowering plants, including those of both the buoyant and 
non-buoyant groups, do not exceed fifty. 

About twenty years ago, Mr. Hemsley, who, in his work on 
the botany of the Challenger Expedition, prepared the way for the 
investigation of this subject, made a list of not less than 1 20 plants, 
almost all tropical, that are " certainly or probably dispersed " by 
the currents (Introd. Chall. Bot, p. 42). This is admittedly only 
a preliminary list, and as the result of recent investigations some 
plants have to be omitted and others to be added ; but I doubt 
whether, numerically, it is far below the mark. The relative 
efficacy of the currents seems to have been first systematically 
discussed by De Candolle in his Geographic Botanique, which 
was published in 1855. Data were then very scanty, and out of a 
list of nearly 100 inter-tropical species (Old World plants found in 
the New World and New World plants found in the Old World) 



vni LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 63 

he designates nine only as exclusively dispersed by the currents. 
Even this list, in one respect, needs correction (see Note 33) ; but 
it is of interest to note that this eminent botanist from the first 
never looked upon the agency of the currents as a very important 
factor in plant-dispersal ; and, finding in the specially directed and 
carefully performed experiments of Thuret confirmation of his 
views, he reiterated his opinion in a note to that author's paper in 
1873 (cited in Chapter III.). 

However, De Candolle was quite right in minimising the effect 
of currents on the distribution of plants. His extensive survey of 
the plant-world from the standpoint of dispersal gave him that 
sense of proportion in assigning values to dispersing agents which 
enabled him to feel his way almost intuitively, even where exact 
data were often lacking. It is, however, a little disappointing to 
find such a slight treatment of the subject in Kerner's great work 
on the Natural History of Plants, though one can scarcely con- 
trovert his opinion that the dispersion of plants, as a whole, is not 
appreciably affected by this process. Numerically speaking, this 
is in the main correct ; yet it is here that the genius of Schimper 
led him to recognise and to mark out a line of investigation, fruit- 
ful in important results, in connection with the weighty question 
of " Adaptation." If the author of this work has been able to add 
a little to our acquaintance with this subject, he owes much to the 
inspiration he received from Schimper's memoir on the Indo- 
Malayan Strand- Flora. 

Still, it must be admitted that the effectual operations of the 
currents as plant-dispersers are limited to the shore-plants with 
buoyant seeds or fruits. If we were to include in our list the 
shore-plants of temperate regions that possess seeds or fruits 
capable of floating in sea-water for long periods, and of afterwards 
germinating, the total for the whole world would not, I imagine,, 
reach 200. We cannot here concern ourselves with those purely 
river-side plants that contribute their buoyant seeds and seed- 
vessels to river-drift, since there is no evidence indicating that river- 
side plants are effectively dispersed by the currents unless they 
also frequent the estuary and the coast-swamp ; and in that case 
they come under the head of littoral plants. The total for the 
whole British flora would probably not far exceed a dozen, and 
nearly all of them are very widely dispersed. 

The working value of the currents as plant-dispersers in the 
Pacific can be rudely estimated by the number of littoral plants 
with buoyant seeds or fruits that occur in the various groups. 



64 A NATURALIST IN THE PACIFIC CHAP. 

Most of these plants hail from the Indo-Malayan region. 
Speaking generally of the extension eastward of the Indo- 
Malayan strand-plants over the Pacific, Prof. Schimper (page 195) 
remarks that they become fewer and fewer in number as they 
extend farther from their original home, their number shrinking to 
a very few in the most remote groups of the Marquesas and the 
Hawaiian Islands. This is well illustrated in the following 
numerical results that I have prepared. Of the whole number, 
some seventy in all, of the littoral plants of the tropical Pacific 
with buoyant seeds or fruits, Fiji possesses about sixty-five, Tahiti 
about forty, and Hawaii only about sixteen. As shown, however, in 
Chapter VII., some of the Hawaiian littoral trees that are useful 
to the aborigines were probably introduced by them. The number 
actually introduced through the currents into Hawaii in all 
likelihood therefore does not exceed ten. There is a method in 
this diminution in numbers, as the plants migrate eastward and 
northward over the Pacific, which has been described in detail in 
the preceding chapter. The efficacy of the currents as plant- 
dispersers in the tropical Pacific therefore diminishes as we proceed 
eastward. 

In the South Pacific the littoral plants preserve their Old 
World origin as far as the Polynesian archipelagoes extend east- 
ward across to Pitcairn, Elizabeth, and Ducie Islands, where we 
find in one or other of them such characteristic Indo-Malayan 
beach trees as Barringtonia speciosa, Cerbera Odollam, Guettarda 
speciosa, Hernandia peltata, and Tournefortia argentea (see Note 34). 
In the more distant Easter Island there is a suspicion, for the first 
time, of immigration from South America in the presence of 
Sophora tetraptera. In the islands relatively close to the 
American continent, as in Juan Fernandez and in the Galapagos 
group, the Indo-Malayan strand-plants are no longer represented. 

We come now to consider the relation between the distribution 
of the shore-plants and the currents. It is quite legitimate to 
discuss the currents of the Pacific from the botanist's point of view, 
.that is to say, from the standpoint of the distribution of littoral 
plants with buoyant seeds or fruits. For ages the buoyant seeds 
.and fruits of the strand-plants of the tropical Pacific have been 
drifting over that ocean, and we have the results now before us in 
the dispersal of the species to which they belong. There is no 
necessity to endeavour to make the distribution of such littoral 
plants square with the arrangement of the currents as shown in a 
chart. The usual result of such a comparison has been to lead the 



viii LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 65 

investigator, whether an anthropologist, a zoologist, or a botanist, 
to find his facts at variance with the course of the prevailing 
currents. Man, animals, and plants have entered the Pacific from 
the west, whilst the most available currents are from the east ; and 
one may be perhaps permitted the solecism that the Pacific islands 
have apparently been stocked with their shore-plants, with their 
aborigines, and with much of their fauna by currents running in the 
wrong direction. These Pacific islands could only have had a direct 
communication with the Old World, from which they have mainly 
derived their shore-plants, by the currents ; but since both the 
aborigines and the plants have forced their way across the ocean 
to the Tahitian region in the teeth of the regular currents, 
indicated as such in the chart, we are compelled to assume that 
they have availed themselves either of the Equatorial Counter- 
Current or of the occasional easterly drift currents that mark the 
prevalence of westerly winds during the short season of the year 
when the easterly trade-winds do not prevail. 

The Equatorial Counter-Current hypothesis would involve a 
preliminary crossing of the whole breadth of the Pacific Ocean, 
that is to say, a voyage of some 8,000 miles, before the drifting 
seed doubled back to the Polynesian Islands. The other view is a 
much more probable one, as is sufficiently indicated by the follow- 
ing extract from the " Admiralty Sailing Directions for the Pacific 
Islands" (II., p. 25, 1900) . . . " In the western part of the Pacific 
these trades . . . are frequently interrupted by winds which blow 
from west or north-west, especially during the months of January, 
February, and March, when the north-west monsoon of the Indian 
Ocean extends out in the Pacific as far as the Samoa Islands." In 
various works on this region one may find reference to canoes 
blown off the shore during this season and carried some hundreds of 
miles to the eastward. A ship can then sometimes sail with a fair 
wind from the southern end of the Solomon Group to the Fijis ; 
and as we learn from Mariner, the crocodile may be at such times 
carried away from the Solomon Islands and stranded in Fiji. 
Mr. Hedley, in his exceedingly interesting paper on a zoo- 
geographic scheme for the mid-Pacific (Proc. Linn. Soc. N.S.W., 
1899), gives many details of this nature; but there is no space to 
deal further with the matter here. 

After all, the botanist must take his cue from the drifting seed 
and the distribution of the plant He finds the seed floating in 
the open sea as well as stranded on the beach. He then discovers 
the plant growing on the beaches, and by experiment he tests the 

VOL. II F 



66 A NATURALIST IN THE PACIFIC CHAP. 

floating capacity of the fruit or seed. Finally he ascertains the 
home of the plant. He does this for all the littoral plants with 
buoyant seeds or fruits, and he forms his own conclusions of the 
efficacy of the currents independently of the current-chart, 
remembering that he has in Time an important factor that the 
geographer does not possess in dealing with the currents. The 
effect of time has often been to obscure the differential results of 
the operations of the currents in the case of those species that, like 
Barringtonia speciosa, are almost universally distributed in the 
islands of the Pacific. It is obvious that such plants cannot aid 
us much in the matter of ascertaining the track followed by the 
drifting seed in entering this ocean. But if we find a littoral 
plant with buoyant seed or fruit that has only partially performed 
the traverse we shall possess in the interrupted operation an 
important piece of evidence. 

Several years ago, in my paper on Polynesian plant-names, read 
before the Victoria Institute, I developed this argument when 
endeavouring to find in the floating seed a clue to the route 
pursued by the Polynesians in entering the Pacific. Since that 
time my acquaintance with these islands and their plants has been 
considerably extended ; but no important modification of the 
principal argument is now needed. It was then pointed out that 
in Nipa fruticans, the swamp-palm of the Malayan Islands and of 
tropical south-eastern Asia, we have a plant well fitted for the 
purpose and one well known to be dispersed by the currents over 
small tracts of ocean. The Nipa Palm has attempted to enter 
Polynesia from the Malayan region by two routes, namely, by 
Melanesia and by Micronesia. Along the first route it has in the 
course of ages reached the Solomon Islands, where I found it in 
1884. Along the second route it has extended its range to Ualan 
at the eastern end of the Caroline Group, where it was observed 
by Kittlitz many years ago, as indicated in the narrative of his 
voyage (Reise nach russische America, nach Mikronesien, etc., 1858, 
ii. 35), and in Dr. Seemann's English edition of the same author's 
Vierundzwanzig Vegetationsansichten .... des stillen Oceans. 

The question now arises as to which of these two routes was 
taken by the drifting seed. In my paper I adopted the view that 
the shore plants reached Fiji and Samoa by Micronesia, that is to 
say, by the Caroline, Marshall, and Gilbert Groups. This is the 
route which, as mentioned by Mr. Hedley in the paper above 
quoted, Mr. Wood ford prefers for some of the Lepidoptera ; and it 
is the one that is favoured by Mr. Wiglesworth for the birds, since 



viii LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 67 

in his memoir entitled Aves Polynesia he remarks that certain 
indications tend to show that the Pelew Islands have served as a 
sort of bridge for the spread of species from Indo-Austro- Malaya 
right across the Pacific. Though I still think that the beach trees, 
most of which would find a home on the numerous coral atolls of 
the Marshall, Gilbert, and Ellice Groups, often followed that 
track, yet I am now inclined to consider that the mangroves and 
their associates, plants which find their most suitable home in the 
estuaries of large elevated islands, like those of the Solomon 
Group, in all probability reached Fiji in the mass by the 
Melanesian route. 

Although the Old World has supplied to the Pacific islands 
most of their littoral plants that are dispersed by the currents, 
that is to say," the plants with buoyant seeds or seed vessels, yet 
there is an appreciable American element, and it is with the plants 
occurring in the New World that we are now concerned. The 
total number of the littoral plants of these islands that possess 
buoyant seeds or fruits is, according to the lists given under 
Note 35, about seventy. Of these about forty-five are exclusively 
Old World species, sixteen occur in both the Old and New 
Worlds, three are exclusively American, and six are Polynesian. 

The question we have now to ask ourselves is whether the 
shore plants common to both the Old World and America have 
their homes in America, or whether they have been derived from 
the other hemisphere. With one or two exceptions, as in the cases 
of the Australian genera Dodonaea, Scaevola, and Cassytha, which, 
as shown in a later page in this chapter, present no great difficulty, 
there does not seem to be any serious objection, as far as the 
numerical distribution of the species is concerned, in regarding 
America as a possible home of the genus. It is not often we shall 
come upon such a striking instance of the principle that where 
the species are most numerous there is the home of the genus, as 
in the instance of Cocos. The Coco-nut palm has been carried 
around the world through the agencies of man and the currents, 
whilst the home of the genus is in America. 

Now assuming that in having to choose between the Old World 
and the New World as the home of most of the genera in the list 
we selected the latter, we have to ask ourselves in what degree this 
would be consistent with the place America holds with regard to 
the distribution of tropical shore-plants dispersed by the currents 
and with reference to the arrangement of the currents. If we 
except the African continent, there is no part of the world that 

F 2 



68 A NATURALIST IN THE PACIFIC CHAP. 

bears such a definite relation to the currents as America, and with 
an ordinary chart of these regions their arrangement is to be 
understood at a glance. Yet strange to say, as far as the distribu- 
tion of tropical littoral plants is concerned, America holds a position 
that the present system of the currents on its coasts will not 
altogether explain. Within the lifetime of the species of mangroves 
and other plants of the coast swamps that are found on both 
the Pacific and Atlantic coasts of tropical America the two 
continents of this name have been united by the emergence of the 
Isthmus of Panama. 

Few things are more significant in plant-distribution than the 
arrangement of the tropical littoral plants with buoyant seeds or 
fruits, a subject that is discussed with some detail by Professor 
Schimper in his work on the Indo-Malayan strand-flora (page 190). 
These plants group themselves into four sections : 

(a) Those of the Pacific and Atlantic coasts of tropical America 
(including the West Indies) and of the West Coast of Africa. 
They include mostly plants of the mangrove-swamps and their 
vicinity, such as Anona paludosa, Avicennia tomentosa, A. nitida, 
Conocarpus erecta, Laguncularia racemosa, Rhizophora mangle, 
etc. 

(b) Those of the Old World excluding the African West Coast 
and extending from the East Coast of Africa eastward to the 
Pacific islands. This is much the largest group and comprises 
many of the plants named in the list given in Note 35 under Old 
World species. One may cite as examples of plants ranging 
almost all over this area, Barringtonia speciosa, B. racemosa, 
Bruguiera gymnorhiza (in its most comprehensive sense), Carapa 
moluccensis, Derris uliginosa, Guettarda speciosa, Hernandia 
peltata, Heritiera littoralis, Pemphis acidula, Rhizophora mucronata, 
etc. Plants of the mangrove-swamp and of the beach are, therefore, 
here included. 

(c) Those occurring all around the tropics and including many 
of the plants mentioned under Note 35 as Pacific island shore- 
plants found also in America. Most of them belong to the Legu- 
minosae, and there may here be mentioned Canavalia obtusifolia, 
Caesalpinia Bonducella, Entada scandens, Gyrocarpus jacquini, 
Ipomea pes caprae, Sophora tomentosa, and Vigna lutea, 

(a) Those confined to a portion of the two great regions, such 
as Nipa fruticans in the Old World, and the Manchineel (Hippo- 
manes mancinella) to tropical America. 

It is to be noted that the ubiquitous species do not include any 



vni LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 69 

of the mangroves. Each of the two regions has its own species, 
none being common to both the American and Asiatic regions, 
although, as is shown in Chapter XXX., the American species of 
Rhizophora is now seemingly breaking its bounds and intruding 
into the Pacific islands. On the other hand, some of the mangrove 
genera, Avicennia, Carapa, and Rhizophora, are found all round 
the globe, whilst others are restricted to one or other of the two 
regions, Bruguiera, Lumnitzera, and Sonneratia, for instance, to 
the Old World region, and Laguncularia to the American and 
West African region. 

For convenience we may designate the two great regions of 
tropical strand-plants, with buoyant seeds or fruits, the American and 
the Asiatic regions, remembering that the first includes both coasts 
of America as well as the African West Coast, whilst the second 
extends from the East Coastj of Africa to Polynesia. Excluding 
the ubiquitous species, these two regions are well distinguished from 
each other. If we look at the chart of the currents we perceive the 
reason of the American region including the West African Coast, 
and we see why none of the indigenous plants of this region occur 
on the African East Coast. So also with the Asiatic region, a 
glance at the chart will show that all the portions of its area are in 
connection with each other directly or indirectly through the 
currents, and that only time is required for the transport of buoy- 
ant seeds over most of the region. 

Hitherto I have mainly followed Professor Schimper in this 
matter ; but since my visit to Ecuador and the Panama Isthmus 
some further considerations have presented themselves to me. If 
the reader will look again at the map of the currents, he will 
observe that there is little reason for supposing that the Asiatic 
region can lend its littoral plants to the American region. On the 
other hand there are greater facilities, as far as currents are con- 
cerned, for America supplying the Asiatic region, namely by 
means of the great equatorial currents that course westward across 
the Pacific to the tropics of the Old World. 

It would therefore seem that the American region can receive 
nothing by the currents from the Asiatic region. If accordingly it 
gives but gets nothing back, we are compelled to assign an origin 
in the American region to all littoral plants dispersed by the 
currents that are found in the tropics around the globe. This is 
what we have already regarded on other grounds as possible for 
nearly all the littoral plants of the tropical Pacific with buoyant 
seeds or seedvessels that are found in America. These plants are 



70 A NATURALIST IN THE PACIFIC CHAP. 

practically the same as those distributed around the tropical zone 
which are enumerated in the list given under Note 35, b. With 
their home in America, by crossing the Pacific they would ulti- 
mately arrive at the East African coast, where their course 
westward would terminate ; whilst commencing their journey from 
the east side of the American continent they would reach the West 
African coast ; and their distribution around the tropics of the 
world would be explained. There follow from these considerations 
the corollaries that a tropicaFstrand-plant dispersed by the currents 
which has its birthplace in Asia could never reach the American 
region, and that American strand-plants are for the most part 
native-born, excepting those, if there are any, that hail originally 
from the African West Coast. 

It is necessary in passing to explain the similarity of shore 
plants on the Pacific and Atlantic coasts of Tropical America. 
For the mangroves and their accompanying plants inter-com- 
munication between the two coasts is now impossible ; and a 
communication between the two oceans must be postulated 
within the lives of the existing species. For the plants like 
Entada scandens and Ipomea pes caprae, which occur inland as 
well as at the coast, it is easy to show that in the case of the 
Panama Isthmus, their seeds could be readily carried into the 
Atlantic and Pacific Oceans by rivers draining the opposite slopes 
of the same " divide," so that the dispersal of the same species from 
a common centre into two oceans may be seen in operation in our 
own day. My observations on this subject are given -in Chapter 
XXXII., to which the reader is referred. 

I have now gone far enough to indicate the place that America 
holds with regard to the distribution of tropical shore-plants dis- 
persed by the currents and with regard to the currents. There is 
every probability, as I venture to think I have shown, that the 
Pacific islands have derived most of their ubiquitous shore-plants 
with buoyant seeds or fruits from America. But one of the results 
of our discussion of America in this double aspect was that 
excepting in the case of the African West Coast it gives but does 
not receive plants from the Old World. We apply this test, with 
perhaps a little hesitation, to the shore-plants of the Pacific islands 
that are dispersed by the currents ; and we find, as will be seen 
below, that it is responded to in a remarkable manner. 

It has been observed in the previous chapter that scarcely any 
of the large-fruited beach-plants of the South Pacific islands, that 
could only have been dispersed by the currents, have reached 



vin LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 71 

Hawaii. We do not find amongst the truly indigenous coast flora 
of this group any of the following trees : Barringtonia speciosa, 
Calophyllum Inophyllum, Cerbera Odollam, Guettarda speciosa, 
Hernandia peltata, Ochrosia parviflora, Pongamia glabra, Termi- 
nalia Katappa, Terminalia littoralis, &c. It was also noted that 
the currents had not only failed to establish these plants in Hawaii, 
but that they had also failed to establish them in America, the 
suggestion being that the Hawaiian Islands had been, in part at 
least, stocked by the currents from America. That the Indo-Malayan 
strand-plants in their extension eastward over the Pacific should 
have failed to reach America, is a result we might have expected 
from the arrangement of the currents. Yet mingled with them 
we have plants like Ipomea pes caprae, Canavalia obtusifolia, and 
Sophora tomentosa, that also occur in America. Since, however, 
their seeds are not better adapted for accomplishing the passage 
across the Pacific from the Old World to America than the equally 
buoyant fruits of the above-named littoral trees that have failed, 
the presumption arises that their home is in America, and that they 
have performed the easier passage across the Pacific westward from 
America to the Old World. 

The exclusion of so many characteristic shore-trees from America 
that range often over the whole tropical region from the African 
East Coast to the islands of the Central Pacific, is not a matter of 
seed or fruit-buoyancy, but a matter concerned with the home of the 
species, and with the arrangement of the currents. Those shore- 
plants of this region that occur also in America have their home 
in that continent, and have subsequently been carried across the 
Pacific by the currents westward to the Asiatic shores. 

The only exceptions, that I can recall, to the rule that America 
does not receive shore-plants dispersed by the currents from the 
Old World, are presented by the three Australian genera, 
Dodonsea, Scaevola, and Cassytha, of which widely spread littoral 
species occur in America, namely, Scaevola Lobelia, Dodonaea 
viscosa, and Cassytha filiformis. They offer, however, but little 
difficulty, since, as pointed out in other parts of this work, 
Dodonaea viscosa has probably been in part dispersed by man, 
whilst the other two species are as well fitted for dispersal by birds 
as by currents. The occurrence therefore of these species in 
America does not necessarily raise the question of the currents. 

The same exclusive principle is illustrated in the scanty littoral 
flora of Hawaii. Deprived, like America, of the characteristic 
large-fruited beach-trees of the South Pacific, species that could 



72 A NATURALIST IN THE PACIFIC CHAP. 

only have reached it through the agency of the currents, it is 
scarcely to be expected that it would have received its few littoral 
plants with buoyant seeds from the source which has failed it in 
the cases of the numerous absentees. It is to America therefore 
that we look for the source of its littoral plants as far as the 
agency of the currents is concerned. 

The Hawaiian Islands contain about twelve plants, named in 
the list given in Note 36, that possess seeds or fruits known to be 
dispersed by the currents, and capable, as experiments indicate, of 
floating in sea-water for prolonged periods. Not all of them are 
at present littoral in their station in this group ; but their claim to 
be considered such in other regions is established in the Note 
above mentioned. Of these plants, seven at least are found in 
America, five in the Old World also, and two exclusively in 
America. This proportion of American plants is far greater than 
that characterising the whole littoral flora of the Pacific islands 
dispersed by currents, where out of some seventy species only 
nineteen are found in America (see Note 35). As far as the 
distribution of the plants is concerned, it is therefore quite possible 
that Hawaii has received most of its plants that are dispersed by 
the currents from tropical America. 

We will now consider how such a possibility is in accordance 
with the arrangement of the currents in the North Pacific. If we 
look at the Quarterly Current Charts for this ocean published by 
the British Admiralty we notice that all through the year the 
Hawaiian Group lies more or less within the area of currents 
flowing from the West Coast of America, the Northern Equatorial 
Currents as they are collectively named. Except in the winter 
months these currents come from the N.E. and E.N.E., and bring 
drift from the coasts of British Columbia, Oregon, and Northern 
California. It is then that they pile up huge pine logs on the 
shores of the Hawaiian Islands, as I have described in Chapter VII. 
and in Note 30 ; and, according to Dr. Hillebrand, they transport 
this drift timber much farther south to the shores of the Marshall 
and Caroline Groups. One might cite other facts illustrative of 
the working of these currents, such as one finds in the pages of 
Fornander and other authors ; but this would scarcely come 
within the province of this work. I may here remark that when 
in Honolulu I was informed that a bell-buoy which had got adrift 
on the Californian coast was subsequently washed up on the coasts 
of Kauai. It is stated in Findlay's " North Pacific Directory " 
(1886, p. 1068), that a junk carrying nine hands that had been 



vin LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 73 

blown off the south coast of Japan in a typhoon, anchored, after 
ten or eleven months at sea, in December, 1832, near Waialea in 
Oahu, the view taken of its course being that after drifting along 
in the Japan Current it came within the range of the south-west 
current that carries pine timber to Hawaii from the West Coast of 
America. 

The portion of the Northern Equatorial Current that strikes 
the Hawaiian Group during the greater part of the year is no 
doubt a south-westerly deflection of the Japan Current from the 
American West Coast ; and it would be impossible to find any 
tropical drift mingled with the pine logs stranded on the islands 
during that period. However, in the winter months, centering in 
January, the Japan Current flows down the West Coast of America 
to about the latitude of Cape Corrientes on the coast of Mexico, 
before being deflected westward. Here it meets with a portion of 
the Peruvian Current, and both flow westward, the united stream 
striking probably only the southernmost islands of the Hawaiian 
Group. It is at this season alone that there would be any 
likelihood of drift from tropical America being stranded on the 
Hawaiian beaches, and it is quite possible that at such a time the 
Northern Equatorial Current may carry intermingled in its stream 
pine logs from Oregon and seed-drift from Panama. 

I am not inclined to attach any value except in the Western 
Pacific to the agency of the Equatorial Counter-Current in trans- 
porting seeds and fruits over the Pacific. It presents seemingly 
the only opportunity of the transportal of the seeds and fruits of 
Asiatic littoral plants to America ; but if at all effective in this 
way, it would have endowed the littoral flora of the western shores 
of tropical America with many of the trees so characteristic of the 
coral islands of the Pacific. In this sense, it has failed completely 
as an effective agency in plant-dispersal ; and judging by results 
we may, I think, dismiss it from our consideration. However, 
Dr. Hillebrand (p. xv.) assumes that during the prevalence of 
south-westerly gales in winter in the Hawaiian Islands, the 
Equatorial Counter-Currrent would be pushed northward so as 
to mingle to the east of the group with the North Equatorial 
Current. In this manner it is supposed that seed-drift brought 
direct from the Asiatic side of the Pacific would be stranded on 
these islands. This appears to me to be most improbable, since 
some ten or twelve degrees of latitude usually intervene between 
the Hawaiian Group and the Equatorial Counter-Current (see 
Admiralty Sailing Directions, Pacific Islands, 1900, II., 31, and the 



74 A NATURALIST IN THE PACIFIC CHAP. 

Quarterly Current Charts ; also Encyclopaedia Britannica, vol. 18, 
p. 1 1 8). 

The most serious objection from the botanist's standpoint 
against such a view as that of Dr. Hillebrand is the absence from 
Hawaii of most of the shore-plants that we should expect the 
currents to have brought from the Old World. It is also evident 
that as far as the currents are concerned the Hawaiian Islands are 
far more likely to receive littoral plants from America than from 
the Old World. Though no tropical drift has yet been found 
stranded on the coasts of these islands, yet it is not unlikely that 
future investigators may find some seed-drift from Central America 
on the most southerly coasts of the group, as on the south-east 
shores of the large island of Hawaii. It would only be stranded in 
the winter months and then probably in small quantities. 

Summary of the Chapter. 

(a) Since the effective operations of the currents are limited to 
the shore-plants with buoyant seeds or fruits, such plants forming 
but a small proportion of any flora, it must be acknowledged that, 
numerically speaking, the results of the dispersing-agency of the 
currents on plant-distribution in general are but slight. 

(b} Yet the importance of the subject is by no means to be 
measured by a numerical scale of results, a line of inquiry being 
here opened up leading to fields of investigation full of promise for 
the student of plant-distribution. 

(c) Whilst dealing with the relation between the distribution 
of shore-plants and the arrangement of the currents, it is quite 
legitimate to discuss the currents of the Pacific from the point of 
view of the botanist, who, after all, must take his cue from the 
drifting seed and the resulting distribution of the plant. 

(d) The shore-plants of the Pacific islands that are dispersed by 
the currents being mainly Indo-Malayan in origin, it follows that 
they have extended eastward over the Pacific to the Tahitian 
islands against the stream of the South Equatorial Current and 
against the trade- wind. It is, however, shown that they could 
have availed themselves of the interval between January and 
March when the North-west Monsoon reaches the Pacific. 

(e) It is claimed that whilst the mangroves and their associated 
plants have for the most part entered the Pacific by the Melanesian 
route through the Solomon Islands, the beach-plants have also 
followed the route through Micronesia by the Caroline, Marshall, 
and Ellice Groups. 



vni LITTORAL PLANTS AND CURRENTS OF THE PACIFIC 75 

(/) A small number of the strand-plants of the Pacific islands 
that are dispersed by currents occur in America as well as in the 
Old World ; and questions of prime importance arise when we 
have to decide whether their home is in the Old World or in the 
New World. 

(g) Good reasons are given for regarding them as chiefly of 
American origin ; and it is shown that America with regard to 
the arrangement of the currents stands in the singular relation of 
being a disperser but not a recipient of shore-plants. 

(h) It is pointed out that the tropical shore-plants that are dis- 
tributed by currents belong to two great regions which are the 
effect of the present arrangement of the currents, viz., the American 
including the West Coast of Africa, and the Asiatic comprising the 
remainder of the tropical zone. Each region has its own plants, 
and those that occur in both, being in fact distributed all round the 
tropics, are regarded, according to the principle above stated, as 
having their home in the American region. 

(z) The occurrence of the same strand species on the Pacific and 
Atlantic coasts of tropical America is regarded as indicating that 
the arrangement of the existing species of its shore-plants, more 
particularly of the mangroves, antedates the emergence of the 
Panama Isthmus. This hypothesis is not needed for the coast 
plants like Entada scandens that occur inland, since we can now 
observe their seeds being carried down into the Atlantic and 
Pacific Oceans by rivers draining the opposite slopes of the same 
" divide " in the Panama Isthmus. 

(/) It is shown that the currents of the Pacific have failed to- 
establish the numerous beach-trees (possessing buoyant fruits) of 
the Pacific islands, not only in the Hawaiian Group, but also on 
the coast of America ; and it is therefore argued that we should 
expect the Hawaiian Group to have received through the currents 
its shore-plants with buoyant seeds or fruits from the tropical west 
coasts of America. 

(/) In support of this contention it is pointed out that most of 
the Hawaiian strand-plants that are dispersed by the currents are 
found in America, and some indeed in America to the exclusion 
of the Old World. 

(/) The arrangement of the currents in the North Pacific also 
favours the view that the Hawaiian Islands are more likely to 
receive plants by the agency of the currents from America than 
from the Asiatic side of the Pacific. 



CHAPTER IX 

THE GERMINATION OF FLOATING SEEDS 

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

THE tendency of the floating seed or fruit to germinate in the 
estuaries of tropical rivers is especially characteristic of the plants 
of the mangrove-swamps and of their borders. In the Fijian 
rivers, and particularly in the estuary of the Rewa, where the 
river-water is usually mixed with that of the sea, there are 
frequently to be found in a state of germination floating fruits of 
Barringtonia racemosa, Carapa obovata, Clerodendron inerme, 
Derris uliginosa, Smythea pacifica, &c. ; whilst the floating fruits 
of more characteristic beach-trees like Barringtonia speciosa and 
Cerbera Odollam, that grow also on the sides of the estuaries, were 
never noticed in this condition. That this tendency should be 
restricted to the plants of the mangrove-formation and is not to be 
observed in the beach-trees is a singular fact. There is, however, 
an intermediate group of littoral plants mostly belonging to 
genera of the Leguminosse and Convolvulacese, such as Mucuna 
and Ipomea, where germination of the floating seed is apt to 
begin but ends abortively, and results in the sinking and death of 
the seed. The subject of the germination of seeds in the floating 
drift of tropical estuaries presents itself, therefore, in three 
aspects : 

(1) As concerning the plants of the mangrove-formation, where, 
excluding the viviparous species (when germination takes place on 
the plant), germination is frequent in the water : 

(2) As concerning the beach-trees where it is rare or absent 
altogether : 

(3) As concerning certain Leguminous and Convolvulaceous 



CH. ix THE GERMINATION OF FLOATING SEEDS 77 

littoral plants where germination is not infrequent but always 
abortive. 

Dealing first with the plants of the mangrove-formation, it may 
be remarked that the same tendency of the floating fruits or seeds 
to germinate, which is above noticed in the case of the estuaries of 
Fiji, came under my observation in the floating drift of the estuary 
of the Guayaquil River in Ecuador, the germinating fruits and 
seeds being carried far out to sea. The seeds of Anona 
paludosa, which float in quantities in the river-drift, were often 
found germinating ; and the same may be said of the fruits of 
Laguncularia racemosa and of the " joints " of Salicornia peruviana 
which abound in the creeks of the mangrove-delta and are carried 
out to sea in the germinating condition. 

It might be expected that this readiness to germinate in the 
brackish water of estuaries would prove to be a formidable 
obstacle to the dispersal of these plants over wide tracts of ocean. 
The exposed portions of the seedling might be deemed ill-suited 
to withstand, without injury, the " wear-and-tear " of transport by 
currents over long distances, even when not affected by the sea- 
water ; and it might be thought that they would be often nibbled 
off by fish or destroyed by other aquatic animals. Only the 
specially organised seedlings produced by a viviparous process on 
the tree, such as those of Rhizophora and Bruguiera, might be 
regarded as able to survive the effects of prolonged immersion in 
the oceanic currents. 

Observation, indeed, shows that such seedlings are exposed to 
and suffer from these perils ; yet it is evident from the distribution 
of the species that, whether in the germinating condition or not, 
the seeds and fruits of Anona paludosa and Laguncularia racemosa 
have been carried by the currents from America to the West Coast 
of Africa. The seedlings of Avicennia and of Rhizophora mangle 
have also performed the same trans-Atlantic voyage. Those of 
both these mangroves are to be observed floating off the coasts 
and in the estuaries of both coasts of America. The seedlings of 
Avicennia are particularly abundant in the mangrove-creeks of the 
delta of the Guayaquil River ; and I observed them in a healthy 
condition, ten to twenty miles out at sea, floating together with 
those of the Rhizophora. Since, as in the case of Rhizophora, 
germination occurs normally on the plant, Avicennia can only be 
dispersed by its floating seedlings. Yet it is noteworthy that 
although Avicennia seedlings appear, to a marked degree, less 
fitted for ocean transport than those of Rhizophora and Bruguiera, 



78 A NATURALIST IN THE PACIFIC CHAP. 

the species have a much wider distribution. Avicennia officinalis has 
a cosmopolitan distribution in the tropics and beyond, occurring as 
it does on the Atlantic and Pacific coasts of America, on both 
coasts of Africa, over Asia and Australia, as well as in New 
Caledonia and New Zealand, but not in Polynesia (Bot. Chall, 

Exped.^ III., 178) I have now gone far enough to show that 

the tendency displayed by the seeds and fruits of several of the 
plants of the mangrove-formation to germinate either on the tree 
or in the floating drift of estuaries has not affected the general 
distribution of the species in its main outlines. Few fruits are 
found more often in a germinating condition in the floating drift 
of the Rewa River in Fiji than those of Barringtonia racemosa, 
yet the species ranges from the African East Coast eastward to 
Polynesia. Seedlings as well as seeds or fruits, whether or not in 
a germinating condition, are, therefore, able in such cases to disperse 
the species. 

This readiness of the floating fruits of plants of the mangrove 
formation (excluding the viviparous species) to germinate in the 
estuaries is, I am inclined to think, due in the main to the strain of 
vivipary that runs through nearly all the plants of the mangrove- 
swamp and of its borders. It would, indeed, appear that the 
viviparous habit (the capacity of germinating on the plant) which 
finds its extreme development in Rhizophora and Bruguiera of the 
Fijian swamps is represented in its earliest stage in the readiness 
of the floating fruits of Barringtonia racemosa, Carapa obovata, &c., 
to germinate in the Fijian estuaries, and as remarked in Note 37 
there is a suspicion of vivipary in the instances of both the species 
just named. Intermediate cases, as that of Laguncularia in the 
Ecuador swamps, occur in other regions with species where 
germination only takes place at times on the plant. This subject 
is, however, generally discussed in Chapter XXX. and need not 
be further dealt with here. 

A predisposing cause of the germination of floating seeds and 
fruits in tropical estuaries would seem to be afforded by the super- 
heating of the water of the estuary. This came under my notice 
both in the Rewa River in Fiji and in the Guayaquil River in 
Ecuador, where the water of the estuary is often noticed to be 
some degrees warmer than that of the sea outside, and of the 
water from the river above the estuary. (See Note 38.) 

We come now to the subject of the non-germination in tropical 
estuaries of the floating fruits of the beach-trees, such as Bar- 
ringtonia speciosa and Cerbera Odollam, that in the Pacific islands 



ix THE GERMINATION OF FLOATING SEEDS 79 

may contribute to river-drift. Such trees may grow on the banks 
of the estuary, and their fruits would thus readily fall into the 
water ; but in the Rewa estuary in Fiji it was evident that the 
fruits and seeds of beach-plants, such as Scaevola Koenigii, are also 
brought in by the tide. The seeds of Morinda citrifolia were 
often noticed in the Rewa drift together with the fruits of Heritiera 
littoralis, which is both a beach and a swamp plant, but never in a 
germinating condition. The same remark applies also to the 
fruits of beach trees found afloat in the sea between the islands, 
such as Cordia subcordata, Guettarda speciosa, and Terminalia. 
It is possible that a few of these plants, as in the case of Bar- 
ringtonia speciosa, display traces in the structure of their fruits of 
a lost viviparous habit. (See Note 50.) It is pointed out in 
discussing Guettarda that germination is much more easily induced 
than one would expect in the case of fruits with such a hard 
ligneous putamen. 

An interesting subject is presented in the abortive germination 
of the floating seeds of many plants of the Leguminosae and 
Convolvulacese both at sea and in a tropical estuary. My con- 
clusions on this matter are based partly on observations made in 
Fiji, but mainly on the results of numbers of experiments, this 
being unavoidable, since the abortive germination causes the 
sinking of the seed. The principal determining cause of the 
germination in water of one of these floating seeds is evidently to 
be sought in the temperature of the water, it being immaterial for 
the earliest stage of germination, as many of my experiments 
indicate, whether the seed or fruit is afloat in the sea or in the 
river. In these flotation experiments, when conducted under warm 
conditions with sea-water, the earliest signs of germination were 
frequently displayed in the softening, swelling, and sinking of the 
seed. If the swelling seed is taken out in time and planted after a 
preliminary soaking in fresh water, the germinating process is at 
once resumed and is often successfully and rapidly completed ; but 
if the seed is allowed to remain in the vessel after it has absorbed 
sea- water the vitality of the embryo is destroyed and the seed 
decays. 

That many seeds would fail from this cause to cross an ocean 
my experiments repeatedly demonstrated. Nor does the ap- 
pearance of a seed afford any indication of its probable failure to 
cross an ocean. Some seeds of Mucuna, as far as their hard 
coverings could guide one, would seem to be quite secure from 
such a risk. The stony seeds, for instance, of M. urens D.C. look 



So A NATURALIST IN Til 1C 1'ACIHC CHAf 

as if they mivhi :..ii< l\ he transported by the currents round .m<l 
round the globe; and De Candolle very ri-htlv placed tin's species 

in hi-, scanty list >! plants dispersed hy currents. Yet lew seeds 

are more treacherous when their Imovam y in sea-water is tested in 
a warm place, as in a hot-house. They may take up water, swell, 
and sink in a week, or they may float unharmed for ;i year, 

The seeds most exposed to this risk are those <>r the 

l.e : ;nminons ; ;i.ml climber,, the lianes o| th- , o.i-.i .ind inl.ind 

forests of the islands of the tropical Pacific. They belong to the 
genera Mucuna, Strongylodon, &c, ; and thus several of the plant 
that constitute for the student of plant-dispersal the enigmas of 

the Pacific are here included. The seeds of Miieiina are especially 

liable when afloat in sea-water under warm conditions to display 
the early signs of germination, swelling up and sinking to the 
bottom of the vessel, a process, however, soon arrested and 
followed by the death of the embryo unless the seed is removed in 
time. Yet the seeds of this genus are notably long "floaters," 
Those of an American species, variously designated as Mucima 
pruriens D.C. and M. urens D.C., have long been known to be 
washed ashore together with the seeds of Entada scandi n <>n tin- 
western shores of Europe, and particularly on the Scandinavian 
coast, where they form regular constituents of what the Scan- 
dinavian botanists correctly term the Gulf-stream Drift. 

Mucuna urens D.C. occurs with other American shore plan! 
that are dispersed by the currents on the African West Coast ; and 
there is no reason to doubt that its seeds perform the trans- 
Atlantic voyage. It is found in Polynesia, in Hawaii, in tin- 
Marquesas, and according to Reinecke also in Samoa; and 
probably it occurs in other groups. The specific determinations of 
the genus, however, need thorough overhauling, so that it is not 

possible to deal more than in -encral terms with the distribution 

of a species. The distribution of Mucuna urens in the Pacific i ,, 
however, irregular, and no doubt this is to be connected with tin- 
uncertain behaviour of its seeds when transported by tropical 
currents. The seeds would, I venture to think, often sink through 
abortive germination in the warm areas of equatorial seas. 

When in Hawaii I kept ten of the seeds of this spe. 
(M. urens D.C.) in sea-water for four and a half months, none of 
them sinking in that period, the temperature of the water rarely 
reaching over So K, the average daily temperature bcini; 76 -/; . 
However, when four years afterwards in England I placed five .i 

the seeds obtained at the same time in sea-water under conditions 



ix THE GERMINATION <>!< KLOATINCJ SICKI) i Hi 

where tin- water temperature ran;;ed |.,i lli,- In ,1 |,-\v u<-,-| 

between 75 and 90, three of them began to swell within ten day;, 
and 'n removal at onee : M -mi inal < -d In -a 1 1 Inly. The rrm.iiimi'.; two 
were! afloat at tin- end of twelve months, and uhen planted one "I 

them verm muted a month aftei wards, 

Having experimented on the seeds of about half a dozen 

dilfeirnt ,],< irs <!' Mm 111 i.i i iter, all with buoyant qualities, 

it is po iihli- for me to lay down the general rule for the buoyant 
seeds of the gem is that sinking is the result of an attempt at 

;;< rmination, wlii h, a . l>< lir "I, ,, -\\, d, proves abortive miles . the 

seed is removed in time, It is obvious that the gardener wishing 

to raise plants ol this venns without delay mi;.'.ht profitably adopt 

the method of keeping them afloat in water at a temperature of 
So 90 F, until they begin to swell, which may happen in some 
cases in a few days. Sea-water seems to produce the most rapid 

results. 

When on Keeling Atoll in the Indian Ocean I collected, 

amoii;;,! thr stranded seed drift bioiijdit by the currents to those 

i lands, the seeds of five or six species of Mucuna, two of which 
were identified at Kew as M. macrocarpa, Wall., and M. gigantea 
D.C. (see my paper on the dispersal of plants at Keeling Atoll). 
No plant of this genus appears up to that time to have been 
recorded from the Keeling Islands, so that at all events most if not 
all of the seeds had been brought by the currents from the Indian 
\r< hip< la ; ;o, -.nine 7oo miles away. It may be added that amongst 
tin dull gathered by me on the south coast of Java the seeds of 
three species of Mucuna were identified at Kew, including the two 

above named species from Keelin- Atoll. 

These current-borne seeds of the Keeling beaches had probably 

performed an ocean journey of a thousand miles, since the route 

could scarcely have been direct. Yet their behaviour when placed 

i h teen months after in sea-water in a hothouse in England was 

erratic. Of three seeds of Mucuna gigantea all swelled and 

sank within ei : dit days. Two .seeds of M, macrocarpa sank after 

tlo.it ing from sixty to a hundred days; whilst of two seeds of 

anolln r .]<< i-s both remained all.ul alter a \<.n In a sea water 

experiment in England on five Hawaiian seeds of M. gigantea, 

under the conditions referred to in the Mucuna urens experiment, 

one sank within ten days, whilst three of them were afloat after 

twelve months, one of them subsequently germinating. This 

!>! ,ii ;i b i i.ed, is widely distributed as a coast plant 

over tropical Asia, Australia, and in Polynesia. It seems to take 

VOL, II G 



82 A NATURALIST IN THE PACIFIC CHAP. 

the place in the Old World which Mucuna urens takes in America, 
and it is curious that they meet in Polynesia, being sometimes 
associated as in Hawaii. In the chapter on my observations in 
Ecuador and in Panama it is remarked that Mucuna seeds are 
frequent constituents of river, sea, and stranded drift. I, therefore, 
have enjoyed the opportunity of observing the behaviour of the 
seeds of this genus in a variety of localities, namely, in the Keeling 
Islands, in West Java, in Fiji, Hawaii, and tropical America ; and 
this may be pleaded as an excuse for entering into so much detail 
respecting them. 

The large seeds of Strongylodon lucidum (S. ruber), a Leguminous 
liane that ranks with the species of Mucuna amongst the huge 
climbers of the forest of the Pacific islands, behaved in a similar 
way in my flotation experiments in sea-water. Though, as shown 
in Note 3, these seeds can float for a year and retain their 
germinating power, some of them brought their buoyant capacity 
prematurely to an end by an abortive attempt at germination. 
These black rounded seeds form a common object amongst the 
river seed-drift stranded on some of the Fijian beaches in the 
vicinity of estuaries. They are so hard and durable that they are 
mounted in brooches in Honolulu. Yet these pebble-like seeds will 
sometimes begin to swell in a few days in sea-water. Out of five 
seeds placed in sea-water in England under warm conditions (the 
water temperature for the first few weeks ranging between 75 and 
90 F.), one swelled and sank within ten days, another did so after 
two months, whilst the other three were afloat after twelve months,, 
and one of them subsequently germinated. There is some 
disagreement amongst botanists as to the limits of the specific 
characters of the plants of this genus (see Note 39) ; but the 
plan seemingly most in accord with the fundamental principles 
regulating plant-distribution in this region of the Pacific is to* 
regard the forms found in Hawaii, Tahiti, and Fiji, as referable to 
one species. In addition to the Polynesian forms there are only 
two or three species, found in the Philippines, Madagascar, and 
Ceylon, and it is with the species from the last-named locality that 
the Polynesian species is by some identified. 

The seeds of several other Leguminous climbers would probably 
act in a similar way, for instance, those of Entada scandens ; but 
the seeds of this plant experimented on by me were too few to- 
enable an opinion to be formed. Of four seeds of Dioclea violacea 
from Fiji that were subjected to the same experiment as those of 
Strongylodon lucidum, all floated in sea-water after a year, with 



ix THE GERMINATION OF FLOATING SEEDS 83 

the exception of one that did not swell and sink until after ten 
months. On the other hand, in my experiment in Fiji on the fresh 
seeds of Canavalia obtusifolia, a plant found on tropical beaches all 
round the globe, seventy per cent, sank in the first six or seven 
weeks, swelling and displaying the first signs of germination, but 
quite ten per cent, were afloat after three months. 

My experiments on the foregoing and other littoral species of 
the Leguminosae merely indicate that under the ordinary tempera- 
ture of tropical currents a portion of the seeds will probably sink 
owing to abortive attempts at germination. It is likely that if in 
the experiments in England a constant temperature of 85 to 90 R 
had been sustained throughout, most if not all of the seeds would 
have swelled and sunk within a month or two. The temperature 
of the experiments in Fiji and Hawaii did not exceed that of many 
tropical currents ; but there are areas of superheating in equatorial 
seas, which I think would prove insurmountable barriers in the path 
of most drifting Leguminous seeds, a subject to which further 
reference will be made. 

Coming to the Convolvulaceae, my experiments show that the 
buoyant seeds often lose their floating powers from the same cause. 
Those of Ipomea pes caprae may be taken as an example. I was 
surprised to find when experimenting on the buoyancy in sea- 
water of these seeds in Fiji and Hawaii that a considerable pro- 
portion, about a third, sank in the first two months, swelling and 
sinking to the bottom. That this swelling represented the early 
stage of germination was well brought out in parallel experiments 
in fresh water and sea-water made in England on the buoyant 
seeds of the British littoral species, Convolvulus soldanella. A 
good proportion of the seeds in the first part of the experiment 
absorbed water, swelled, and sank, those in fresh water proceeding 
at once to germinate healthily at the bottom, whilst those that sank 
in sea- water merely decayed. Of the survivors about fifty per 
cent, in either case floated after six months. It may be added 
that the seeds of other tropical littoral species, such as those of 
Ipomea glaberrima and I. grandiflora, behaved in the same way. 

It would appear from my experiments, and it is a result that 
we should expect, that buoyant seeds of the Leguminosae and 
Convolvulaceae would often float for much longer periods under 
cool than under warm conditions. There must be areas of high 
temperature in mid-ocean that would prove much more fatal to the 
chances of a drifting tropical seed than the icy waters of a Polar 
current. In my paper on Keeling Atoll I have described how I 

G 2 



84 A NATURALIST IN THE PACIFIC CHAP. 

procured the germination of a seed of Ipomea grandiflora, Lam., 
after a year's flotation in sea-water in London, which included a 
period of three weeks when the water temperature was at or about 
32 F. These seeds from this point of view would be exposed to 
much more risk of sinking through abortive attempts at germina- 
tion when drifting across some parts of the Pacific Ocean. It 
would appear from the Admiralty Chart of Surface-Temperatures, 
published in 1884, that such an area with a surface-temperature of 
83 to 86 throughout the year extends north and east of New 
Guinea well into the Pacific, reaching in the first half of the year as 
far east as the Tahitian region. It would seem highly probable 
that the immersion of Leguminous or Convolvulaceous seeds for 
many months in these tepid waters would in most if not in all 
cases induce incipient germination which would lead to the sinking 
of the seed. There are, however, exceptional cases, as that of 
Caesalpinia bonducella, which, as my experiments recorded in 
Chapter XVII. indicate, appear to be quite proof against any 
conditions of temperature such as are likely to be found in tropical 
seas in the present day. 

There are a few general considerations arising out of the fore- 
going observations to which reference may now be made. The 
study of the behaviour of the floating seed or fruit often carries us, 
as I have before implied, to the borderland of vivipary. When 
from a canoe on a Fijian river we lift up the germinating fruit of 
Barringtonia racemosa from amongst the drift floating past in the 
stream and pull down from the branches overhead the seedling a 
foot in length of Rhizophora, we hold in our hands the two extremes 
of the series of vivipary. With many of the plants of the mangrove- 
formation there is a fine adjustment with respect to the germinat- 
ing capacity of the seed, or in other words a delicate balancing of 
organisation on one side and of physical conditions on the other. 
A slight disturbance of the equilibrium would produce great results 
in plant distribution. Thus, an elevation of the temperature of the 
J sea-water in the tropics to 90 F. would, I apprehend, produce the 
abortive germination of nearly every floating seed and fruit in 
equatorial seas, even of those of the beach-trees like Barring- 
tonia speciosa and Terminalia littoralis that are regarded as proof 
against such risks under existing conditions where the surface- 
temperatures would average 78 to 80. 

There would thus be a barrier to the dispersal of plants by 
currents as effective as that of a frozen ocean. In the warm, humid 
climates of the early geological ages, seed-transport by currents 



ix THE CiERMINATION OF FLOATING SEEDS 85 

may have been often impossible, since the seeds that did not begin 
to germinate on the plants of the swamps would probably do so 
in the tepid water of the sea. Viviparous plants would, however, 
be placed at no greater disadvantage than they are at present, since 
the genera Rhizophora, Avicennia, and others are now only 
dispersed by the floating seedlings. But such an increase of 
temperature at the present time would mean the death in the 
current of the floating seeds and fruits of nearly all non-viviparous 
shore-plants. As a rule every Leguminous and Convolvulaceous 
seed would swell up and go to the bottom ; whilst fruits like those 
of Barringtonia racemosa and Carapa obovata, that often germi- 
nate afloat in tropical estuaries, would invariably do so under the 
changed conditions, and the seedlings not being adapted for ocean 
transport would perish. 

Yet we know that with the seeds of many inland plants 
temperature has seemingly very little to do with starting the 
process of germination. We are familiar with the fact that the 
seeds of many plants that fail to germinate in the summer of their 
production habitually germinate under apparently less favourable 
conditions of temperature in the following spring. This is attributed 
by botanists to the immaturity of the seed on first falling from the 
plant, a further period of maturation being necessary before, under 
any conditions, germination is possible. 

We see this also well illustrated in the floating seeds and fruits 
of the Thames drift. Most of them fail to germinate in the drift at 
the end of the summer and the beginning of autumn, and defer the 
process until the following spring, when they germinate freely ini 
the water under much cooler conditions than those which they 
experienced in the early part of their flotation in the drift. There 
are, however, exceptions to this rule. Plants like Caltha palustris, 
for instance, are rarely represented in the spring seed-drift of ponds 
and rivers, because most of the fruits or seeds germinated soon after 
falling into the water in the previous summer. 

In most of my sea-water experiments in England the immersion 
had a very marked influence, not in causing premature germination 
and destroying the germinating capacity, as often happens with the 
floating seeds of Convolvulaceae and Leguminosae, especially in the 
tropics, but in postponing without injury to the seed the process of 
reproducing the plant. Such seeds or fruits when placed in fresh 
water after many months of flotation in sea-water germinated very 
freely in a few days, whilst those left in the sea-water under precisely 
the same conditions remained unchanged, This is true of many of 



86 A NATURALIST IN THE PACIFIC CHAP. 

the seeds and fruits found in the Thames drift, such as those of 
Ranunculus repens, Lycopus europaeus, Rumex, &c. A striking 
instance was also afforded by the seeds of Arenaria (Honckeneya) 
peploides, where seeds transferred directly to fresh water, after many 
months flotation in sea-water, germinated in a few days ; whilst 
those left in the sea-water remained unchanged. This subject is 
discussed at length in Note 19, and needs no further mention here. 
If the seeds of many plants in Great Britain postpone through 
immaturity their germination to the following or even to the second 
spring, it goes without saying that this does not exclude tempera- 
ture as the ultimate determining factor in germination. The im- 
maturity of seeds adds another link to the series of the germination- 
range in plants. This range begins with the plants where germina- 
tion takes place on the tree and the seedlings hang suspended from 
the branches, as in the typical mangroves Rhizophora and Bruguiera. 
Here, as is shown in Chapter XXX., there is evidently no period of 
repose between the completion of the maturation of the seed and 
the commencement of germination. The range ends with the 
detachment of immature seeds which ripen apart from the parent 
plant, and may postpone the germinating process for months and 
-often for years. All intermediate stages exist between these two 
^extremes. Thus the seedling may at once detach itself from the 
parent as in Avicennia, or the germinating process on the plant 
-may be limited to the protrusion of the radicle as in Laguncularia, 
or the seeds may be quite mature and ready to germinate as soon 
as they fall to the ground, as we find with many small seeded 
^plants. All the stages, of which only a few are here indicated, are 
full of suggestiveness for the student of plant-life. 

This subject is dealt with from other standpoints in Chapter 
XXX., but the reader will now see more clearly what was meant 
when I said that the study of the behaviour of the floating seed leads 
us to the borderland of vivipary. In this range of the germinating 
process we may possess an epitome of the history of the climatic 
conditions of plant-life from an early era in the world's story, 
beginning with those ages when perhaps under the uniform 
conditions that then prevailed, all plants were more or less coast- 
plants and more or less viviparous, and coming down to the present 
era when with an extensive and varied land-surface there is great 
variety both in climate and in the range of germination. The 
mangrove-swamp and its viviparous trees would thus represent 
from this point of view a condition of things once more or less 
universal on the globe. 



ix THE GERMINATION OF FLOATING SEEDS 87 

Summary of the Chapter. 

(a) The tendency of the floating seed or fruit to germinate in 
the brackish water of tropical estuaries is especially characteristic 
of the plants of the mangrove-swamp and their vicinity ; but with 
those of the beach trees that occur in the river-drift it is rarely if at 
all to be observed. 

(b) From the wide distribution of plants of the mangrove- 
formation it is evident that this readiness of the floating seed or 
fruit to germinate is not prejudicial to the dispersal of the species. 

(c) It may perhaps be in the main attributed to a strain of 
vivipary running through all the plants of the mangrove-formation, 
which finds its extreme development in the viviparous species, 
where germination takes place on the tree. But it is probably 
favoured by the superheating of the waters of tropical estuaries. 

(d) In the case of the buoyant seeds of several climbers and 
creepers of the Leguminosae and Convolvulaceae, more or less 
littoral in their station, it is shown that in warm water, whether 
fresh or salt, a good proportion are apt to sink through incipient 
germination, which results when the experiment is made in sea- 
water in the death of the embryo. 

(*) Though in tropical currents of ordinary temperature a good 
number of such floating seeds would escape this risk, it is argued 
that there are certain warm areas in the tropical seas that would 
prove much more fatal to the chances of these drifting Leguminous 
and Convolvulaceous seeds than the icy waters of a polar current. 
It is thus held that these seeds often sink in mid-ocean in tropical 
latitudes through abortive germination. 

(/) The study of the behaviour of the floating seed or fruit 
leads us to the borderland of vivipary. In the scale of the 
germinative capacity of plants it is possible to arrange a con- 
tinuous series that commencing with the mangroves, where germi- 
nation takes place on the tree, ends with those numerous inland 
plants where seeds are liberated in an immature condition. 

(g) It is suggested that the viviparous habit may have been the 
rule under the uniform climatic conditions of early geological 
periods and that with the differentiation of climates that marked 
the emergence and extension of the continental areas the viviparous 
habit has been lost, except in those regions of the mangrove- 
swamps which to some extent retain the climatic conditions once 
general over the globe. With differentiation of climate the true 
seed-stage with its varying rest-periods has been developed. 



CHAPTER X 

THE RELATION OF THE BUOYANCY OF SEEDS AND SEED- 
VESSELS TO THE DENSITY OF SEA-WATER 

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. 

To find amongst the results of my numerous experiments 
examples illustrating the influence of density on flotation has not 
been so easy as I at first imagined. Excluding all adventitious 
causes of buoyancy, a matter discussed in Note 40, it may be 
inferred that the great majority of .seeds and fruits sink both in 
fresh water and sea- water. Of those that are buoyant many float 
indefinitely in both waters, whilst in a very few cases, where the 
floating power is derived from an outer fleshy covering, as with the 
fruits of Potamogeton natans, the fruits float a much shorter time 
in sea-water than in fresh water, on account of the injurious effect 
of the salt upon their coats. 

Experiments have to be specially directed towards this subject. 
It would be useless to experiment in fresh water at one time and 
in sea-water a month later. Nor would it answer to employ seeds 
and fruits from different localities, since variations in this way 
sometimes occur. It is necessary that the experiments should 
be made on seeds or fruits collected at the same time and place, 
and that they should be simultaneous and carried on under the 
same conditions. As the discussion proceeds, the reader will 
perceive that many interesting points are opened up, and that such 



CH. x THE BUOYANCY OF SEEDS AND SEEDVESSELS 89 

an investigation, instead of being, as the title of this chapter might 
suggest, an abstruse and disconnected inquiry, is of considerable 
importance in relation to the dispersal of plants through the agency 
of currents. 

Guided by the results of my experiments in this direction I 
will proceed to lay down certain general principles : 

(A) In the first place it may be accepted as a general rule that 
seeds or seedvessels that sink in fresh water sink also in sea-water, 
the difference in density between the two being rarely a factor of 
any importance in determining buoyancy. The great majority of 
seeds and fruits come under this category, since, as is pointed out 
in Chapter VIII., only a small proportion of the whole, say a tenth, 
possess floating power. We might cite, as illustrative of this 
principle in temperate regions, almost all the 240 species included 
in the non-buoyant group of the British plants experimented on 
(see Chapter III. and Note 10). As a general rule this is true alike 
of the small seeds of the Cruciferae and Scrophulariaceae, of the 
nutlets of the Labiatae and Boragineae, of the genus Scirpus, and 
of the dust-like seeds of Juncus. The results of my experiments 
on the plants of the tropical Pacific are no doubt typical of other 
tropical regions ; and if I wished to quote instances, I should have 
to enumerate not only most of the plants without buoyant seeds 
or fruits that are mentioned in the Fijian and Hawaiian lists given 
under Notes 2, 4, and 6, but also to appeal to tropical regions 
generally. 

(B) One can carry the principle above-named yet further and 
say that not only as a rule do seeds or fruits that sink in fresh 
water sink also in sea-water, but that so far as tested many of them 
sink in water of much greater density than that of ordinary sea- 
water (1-026). Thus, for instance, the seeds of Nuphar luteum, 
Scrophularia aquatica, and Stellaria aquatica, the nutlets of Poly- 
gonum persicaria, and the achenes of Aster tripolium sank in sea- 
water the density of which had been raised to 1*050, the limit of 
the experiment. The minute seeds of Juncus communis and 
J. glaucus and the larger seeds of Luzula campestris, even after 
drying for six months, sank in salt water having a density of 
1-075. It would, however, seem probable that for most of these 
small seeds and seedvessels a density of rioo would prove to be 
the critical point. If this is so, then most of those that sink in 
sea-water would float in the dense water (ri6o) of the Dead Sea. 

However, my investigations have only gone a small way in 
this direction ; and perhaps some of my readers will pursue the 



90 A NATURALIST IN THE PACIFIC CHAP. 

inquiry. I will take the case of the nutlets of Scirpus palustris. 
They sink in fresh water and in sea-water, or may float in 
rare cases for a day or two. Out of 100 of these seed-like 
fruits, 25 floated in salt water of a density of 1*075, J 3 m 
water of 1*050, 7 in sea- water (1*025), and 3 in fresh water, 
(1*000). It would thus appear that the proportion of buoyant 
nutlets is doubled with every increase of '025 of the density 
scale. At this rate of increase they would all float in salt 
water of a density of 1*125, which may be regarded as the 
suitable medium for the flotation of the fruits of this Scirpus. 
. . . The seeds of Glaucium luteum, the Sea-Poppy, have no 
buoyancy either in fresh water or in sea-water even after pro- 
longed drying. They all sank in water of a density of 1*050, 
but 1 8 per cent, floated when the density was raised to 1*075. 
At the rate of increase noticed in the case of Scirpus palustris, 
all the seeds would float in water of a density of 1*130-1*140. . . . 
The acorns of the Common Oak (Quercus robur) have usually 
but little buoyancy unless they have been long drying. After 
soaking in fresh water for half an hour 100 mature fruits, without 
the cupule, that had been kept a fortnight, I found that only 
2 floated in fresh water, 6 in sea- water (1*025), and 18 in water 
of 1*050. At this rate of increase all would float in water having 
a density of 1*080-1*090. 

(C) There is also another general rule, and it is this : Seeds or 
fruits that float for a long time in sea-water usually float almost as 
long in fresh water. Here belong the greater number of buoyant 
seeds and fruits, those only able to float for a few weeks being 
comparatively few. Now with the long-floating seeds and fruits, 
those for instance that float in the drift of English rivers from 
the autumn to the spring, or those that are transported by 
currents over the tropical zone, there is, as a rule, but a slight 
difference between their flotation periods in fresh water and sea- 
water. If one of them sinks after floating for several months 
in fresh water, it will sink in sea-water a few days after. 
Fruits of Scaevola Kcenigii, pyrenes of Morinda citrifolia, and 
seeds of Thespesia populnea, Ipomea grandiflora, Csesalpinia 
bonducella, and of different species of Mucuna, that had been 
kept afloat for a year in sea-water, floated just as buoyantly 
in fresh water at the close ; and in those cases where any 
sank during the course of the experiment, it was ascertained 
that they were able to float in fresh water almost to the end. 

That many of the seeds and fruits of tropical littoral plants 



x THE BUOYANCY OF SEEDS AND SEEDVESSELS 91 

that are known to be dispersed by the ocean-currents will float 
well in fresh water is shown in the constant occurrence in the 
floating drift of Fijian estuaries, where the water may be quite 
fresh or brackish, of the seeds and fruits of plants like Cerbera 
odollam, Clerodendron inerme, Entada scandens, Heritiera littor- 
alis, Ipomea pes caprae, Morinda citrifolia, Mucuna, Vigna lutea, 
&c. In the same way I noticed afloat in the Guayaquil River 
in Ecuador, when the water was quite fresh, seeds and fruits 
characteristic of the sea-drift, such as those of Anona paludosa 
(seeds), Entada scandens, Ipomea, Mucuna, Vigna, &c. ; and 
when we supplement observation with experiment, as for instance 
in the case of Anona paludosa, we find that they will float 
equally long in fresh and sea-water. 

The same rule prevails with most of the buoyant seeds 
and seed vessels of plants' of the British flora seeds and fruits, 
as I may remind the reader, that are mostly to be found in 
river and pond drift. I am not able to distinguish any differ- 
ence of importance in the results of the separate fresh-water 
and sea-water experiments. Thus with the seeds or seedvessels 
of Bidens cernua, several species of Carex, Galium palustre, 
Iris pseudacorus, Lycopus europaeus, Ranunculus repens, and 
numerous others, the difference after a flotation of many months 
was but slight. If the results of the separate experiments were 
to be compared, there would be at least ninety afloat in fresh 
water for every hundred afloat in sea-water ; and if at the end 
of a sea-water experiment, whether occupying three, six, or 
twelve months, the seed or fruits were to be placed in fresh 
water, quite nine-tenths and sometimes more would remain afloat. 
A striking illustration of the principle that the excess in density 
of sea-water, as compared with fresh water, adds but little to 
the floating capacity of seeds is to be found in the results 
given in Note 41 of simultaneous experiments made some years 
since by Mr. Millett and myself at Marazion and in London 
on the seeds of Convolvulus soldanella. 

(D) In their relation, therefore, to the density of fresh water 
and sea-water, most seeds and seedvessels may be placed in two 
principal classes, the first including quite four-fifths of the total, 
where they are much heavier than sea-water, and the second com- 
prising most of the remainder, where they are much lighter than 
fresh water. 

(E) It would be surprising, however, if there were not some 
seeds or seedvessels that come between these two extreme 



92 A NATURALIST IN THE PACIFIC CHAP. 

groups ; some, indeed, that have a specific weight approximating 
to that of fresh water, or to that of sea-water, or fluctuating 
between them, and presenting such evidence of a fine adjustment 
that the observer, forgetting that they are members of a series, 
might be apt to regard them as specially adaptive in their origin. 
It will thus be seen that this subject is gradually assuming a 
statistical character ; and in truth we shall ultimately recognise 
here the play of the laws of numbers. 

As an example of the plants where the specific weight of the 
seeds or fruits is near that of fresh water, Alisma plantago may 
be taken. In the course of an experiment, by lowering the 
density of the water from 1*025 to 1*020, I sent a shower of 
floating carpels to the bottom. The results vary considerably, 
as one might expect ; but, generally, during the first few days of 
an experiment about twice as many (sometimes in all as much as 
80 per cent.) sank in fresh water as in sea-water, a few only 
floating in either water for long periods. . . . The seeds of 
Arenaria peploides present an example where the specific weight 
is between that of fresh water and of sea-water. For the purposes 
of dispersal they may be considered as heavier than fresh water 
and lighter than sea-water. The details are given in Note 18 ; 
but it may be remarked here that plants possessing seeds or fruits 
that sink in fresh water and float in sea- water are very rare. As 
indicated below, this is what we might look for on statistical 
grounds. 

Plants whose seeds or fruits are not much lighter than sea- 
water are exceptional. In such cases the effect of increased density 
of the water is to extend the period of flotation. Thus, in my 
experiments on the nutlets of Scirpus maritimus, the majority of 
the fruits floated in fresh water only eight to ten days ; whilst 
in ordinary sea-water they floated in most cases two to three 
weeks; but when the density was raised to 1*050, the greater 
number of them were afloat after two months. In a few plants, as 
with Spiraea ulmaria, the effect of the difference in density between 
fresh and sea- water was not to extend the period of flotation, but 
to increase the number that floated for a given period, the extreme 
limit of the buoyancy of the carpels in either water with this 
species being about three weeks. 

Amongst tropical plants, as illustrated by those of the Pacific 
islands, cases also came under my notice where the mean specific 
weight of the seed is somewhere between those of fresh water and 
sea-water. The seeds of Afzelia bijuga, an inland as well as a 



THE BUOYANCY OF SEEDS AND SEEDVESSELS 



93 



littoral tree in Fiji, offer an interesting example. If we place 
100 seeds of a littoral tree in sea- water, we find that on the 
average about 70 float. If then we lower the density gradually, 
some of the seeds begin to sink at once ; and on the removal of 
the survivors to fresh water, about 47 will remain afloat. The 
results may thus be stated : Out of 100 littoral seeds, 30 are 
specifically heavier than sea-water (1-025) ; 23 are between sea- 
water and fresh water in specific weight ; whilst 47 are lighter 
than fresh water (rooo). When, however, we take 100 seeds of 
inland trees, we find that on the average 87 are heavier than sea- 
water, 5 are in weight between sea-water and fresh water, and 8 
are lighter than fresh water. The significance of these figures 
becomes evident when we arrange them in curves. The combined 
result for littoral and inland seeds is given in the diagram below ; 



Combined results for 200 seeds of Afzelia bijuga (100 littoral ; 100 inland). 


Percentage. 


Heavier than sea- 
water, or + 1 "025. 


Between sea-water and 
fresh water in weight. 


Lighter than fresh 
water, or - I 'ooo. 


100 

80 
60 
40 

20 
















'.. 






" 


"-.. 

















and we see there, what is also indicated with the separate curves 
that we are dealing with a double series, one concerned with 
seeds lighter than fresh water, and the other with seeds heavier 
than sea-water. The reader can himself supply the separate 
curves for the littoral and inland seeds. The point, however, to 
notice is that if a botanist with a statistical bent were to make a 
miscellaneous collection of the seeds of the Vesi (Afzelia bijuga) in 
one of the Fijian islands, in order to test their buoyancy, he would 
obtain such a result as is given in this diagram. Two varieties of 
the tree would be at once indicated, and further research would 
indicate that these varieties were connected with littoral and inland 
stations. This subject is further dealt with in Chapter XVII. 



94 A NATURALIST IN THE PACIFIC CHAP. 

It might seem strange that the seeds of Entada scandens should 
come into the category of seeds with a specific weight near that of 
fresh water ; yet my observations in Fiji indicate that such is the 
case. In the discussion of this plant in Chapter XVII. it is pointed 
out that, as a rule, not more than a fourth will float in a river when 
they are first freed from the pod, and not more than fifty per cent, 
will float in the sea. Those that float, however, in either water will 
usually float indefinitely. The seeds also of Mucuna gigantea D.C. 
are not very much lighter than fresh water. Out of six seeds that 
floated in sea-water buoyantly, five floated in fresh water t but heavily. 

It is of interest to notice in this connection that the mangrove- 
seedlings produced by germination on the tree, as in the case of 
Rhizophora and Bruguiera, have a mean specific weight somewhere 
between fresh water and sea-water. This is often illustrated in a 
curious way, when the seedling has not been prematurely detached 
from the tree. Thus in the sea off the coast of tropical America, as 
well as amongst the Fijian Islands, the seedlings of Rhizophora 
mangle are as a rule to be observed floating horizontally ; whilst in 
the fresh or brackish water of the estuaries of these regions they 
assume a more or less vertical position, only the plumular portion 
protruding above the water. This is also true of the seedlings of 
Rhizophora mucronata, the Asiatic mangrove, and of Bruguiera 
rheedii. This subject is discussed in detail in Chapter XXX. ; but 
it may be here remarked that a good proportion of Rhizophora 
seedlings, when detached in the mature condition from the tree, 
have no buoyancy, between 20 and 50 per cent, going to the 
bottom when they fall into a river, and between 5 and 10 per cent, 
when they drop into the sea. The navigator might often obtain an 
indication of the density of the sea-surface when approaching the 
mouth of a large river by observing the floating Rhizophora 
seedlings (a foot long) which are carried out to sea in numbers. If 
he sees them from the deck of his ship floating horizontally he will 
infer that the surface-water is mainly sea-water. In ordinary fresh 
water when they float vertically he would not be able to distinguish 
them from floating seeds or fruits. 

It has only been possible to treat this subject in an illustrative 
manner. More details might have been given ; but I have gone 
far enough to bring the following points into relief and to justify 
one in drawing the conclusions to be now stated. 

Most seeds and seedvessels in respect of their floating powers tend 
to gather around two centres or means and to form two groups, the 
sinking group and the buoyant group. 



x THE BUOYANCY OF SEEDS AND SEEDVESSELS 95 

In the sinking or non-buoyant group, which includes 80 per cent, 
of tJie whole, the mean specific weight is considerably greater than that 
of sea-water (ro26), which would require its density to be raised to 
rioo in order to serve as a floating medium for many of them. 

In the buoyant group the mean specific weight is much lighter than 
that of fresh water (rooo) ; and from this it is to be inferred that in 
oceans of fresh water the same fruits and seeds in the mass would be 
distributed by the currents that are transported by them at the present 
day. Even though it arose from an ocean of fresh water, the coral 
island would receive the same littoral plants through the agency of the 
currents that it receives under its existing conditions. 

The number of plants with seeds or fruits between fresh water 
and sea-water in specific weight is very small, probably not over 2 
per cent, of the total. Most seeds or fruits that sink in fresh water 
sink also in sea-water, and most that float in sea-water float also in 
fresh water. Nature has thus created a wide gap between the sinking 
and t lie floating seed ; and nearly all of the work of the present 
currents in plant-dispersal might have been effected, so far as the 
density is concerned, in fresh water. She has not arranged seeds and 
seedvessels in what the statistician would term " a good series." As 
indicated in the diagram below, there are two series that meet in 



Relation of the specific weight of seeds and fruits to the density of 
fresh and sea-water. 


Percentage. 


Heavier than sea- 
water, or + 1 '026. 


Between fresh and sea- 
water, i -ooo 1-026. 


Lighter than fresh 
water, or - I 'ooo. 


100 

80 
60 
40 

20 















.^ 






". 

























the neutral region where the density is between fresh water and 
sea-water, but with culminating points placed on the one side far 
above the density of sea-water and on the other far below that of 
fresh water. 



96 A NATURALIST IN THE PACIFIC CHAP. 

I do not, therefore, think that the buoyancy of seeds and fruits 
has had any relation either in the present or in the past to the 
density of the sea. Nor is it to be supposed that any slight 
variations in density in the course of ages would have materially 
affected the dispersal of plants by currents. It is to be inferred 
that the physicist and the geologist would be prepared to grant 
only small variations, such as a change from 1*020 to 1*025. It 
will be gathered from what has been said before that changes of 
this nature would have a very slight influence on the buoyancy of 
seeds and fruits, since the plants they would affect would be very 
few. The change that the student of plant-dispersal would require 
to produce any marked alteration in distribution would be in 
amount alarming to the physicist. 

Whether or not the oceans have been getting fresher or salter 
in the course of ages (see Note 42), we will be moderate in our 
demands, and will listen to the physicist when he argues that a 
diminishing density, for instance, from 1*035 to 1*025, in the course of 
ages might explain some of the peculiar features in the present 
isolation of insular floras. Many seeds, he would contend, that 
could float across an ocean having a density of 1*035 would be 
unable to accomplish it when the density fell to 1*025. It has, 
however, been remarked that the critical point of density for the 
flotation of seeds or fruits that sink under present conditions is 
probably about 1*100. Cases of such a fine adjustment to the 
density of sea- water are too few to endow this argument with any 
weight. Or it might be suggested that with a gradual increase in 
density in the lapse of ages seeds might float now that sank before, 
or they might float for a longer period. Such a change, however, 
would not have much effect, since nearly all the seeds and seed- 
vessels that sink in our rivers sink also in our seas, and a much 
greater increase of density is required to make any difference. 

Yet, although we might term the sinking of a seed or fruit an 
accidental attribute of certain plants, just as we might regard the 
floating of a log as an accidental attribute of a pine, since in either 
case the specific weight might have been acquired without any 
direct relation to the density of water, still the sinking of the seed 
or fruit signifies a profound distinction not only, as is stated below, 
in plant distribution, but, as we shall see later on, in plant-develop- 
ment. Especially striking, says Prof. Schimper (p. 153), is the 
dependence between an over-sea area of distribution and a station 
at the coast in the case of species of the same genus of which some 
belong to the littoral and some to the inland flora. In the first 



x THE BUOYANCY OF SEEDS AND SEEDVESSELS 97 

place, as has been often remarked in these pages, we have a wide 
distribution generally associated with considerable buoyancy 
of the seeds or fruits. In the second case the areas are usually 
very restricted and there is little or no buoyancy. The better 
fitted a seed or fruit is for dispersal by currents the greater, there- 
fore, is the area of the plant. Whether such an important relation- 
ship depends on an accidental attribute of the seed or fruit is the 
question that immediately presents itself. But it is obvious that 
in raising such a question we touch on a very vital point in 
adaptation, since if attributes developed in one connection have a 
profound influence in another we may have to rearrange some of 
our fundamental notions of the inner workings of Nature. 

Let us, therefore, look a little closer into this matter, and turn 
again to the Pacific islands. The present state of things may be 
thus tersely described. Whilst the shore-plants dispersed by the 
currents have remained relatively the same, changes of all kinds, 
from the production of a variety and of a species to the develop- 
ment of a genus, have taken place in the inland floras. Now, let 
us imagine that all this is altered and that every seed or fruit is 
buoyant. There would then be but little distinction between the 
strand and inland floras, since they would be in a constant state of 
interchange, and most species would be widely distributed. A 
relatively monotonous aspect would belong to all insular floras, and 
indeed to much of the plant-world, since isolation, one of the 
principal conditions for the origin of new species and new genera, 
would often not exist. 

On the other hand, let us suppose that all seeds and fruits 
were non-buoyant. The agency of birds would then be alone 
available for stocking new islands with most of their plants. The 
conditions of isolation would be intensified. There would be no 
widely-ranging strand-flora, since every island and every stretch of 
continental sea-board would possess its own littoral plants that 
could only reflect the peculiarities of the inland flora. The only 
determining factor between coast and inland plants would be the 
presence or absence of the capacity or organisation for occupying 
a station on the sea-shore. 

We have now proceeded far enough to disclose the far-reaching 
influence on plant-distribution and on plant-development that the 
relation between the specific weight of seeds and fruits and the 
density of sea-water must possess. Yet it has been shown that 
when such a relation is viewed statistically it has an accidental 
aspect. We will accordingly devote the next few chapters to the 
VOL. II H 



98 A NATURALIST IN THE PACIFIC CH. x. 

discussion of the buoyancy of seeds and fruits from the structural 
standpoint. 

Summary of the Cliapter. 

(a) The great majority of seeds and seedvessels (quite 80 per 
cent.) are much heavier than sea-water, but a noticeable proportion 
are considerably lighter than fresh water, whilst those with a specific 
weight near that of fresh water or of sea- water are very few. 

(fr) The buoyancy of seed and fruit has no direct relation to 
the density of sea-water, and even if the ocean was deprived of all 
its dissolved salts, the agency of the dispersal of plants by currents 
would not be materially affected. 

(c) Small changes in sea-density, such as the physicist would 
allow, would, therefore, have no appreciable influence on the opera- 
tions of the currents as plant dispersers ; and only great changes 
in density, such as are presented by the waters of the Dead Sea, 
would add materially to the number of floating seeds and fruits. 

(d) Although the specific weight of seeds and fruits in its 
relation to sea-density may be regarded as an accidental attribute, 
their non-buoyancy in the great majority of plants has had a far- 
reaching influence not only on plant-distribution, but on plant- 
development. The plant-world would be transformed if all seeds 
and fruits floated in sea-water. 

(e) If the floating seed or fruit displays a quality that, so far as 
the density of the sea is concerned, has been developed in quite 
another connection, we have next to inquire whether the structure 
of such buoyant seeds and fruits also affords evidence of non- 
adaptation. 



CHAPTER XI 



ADAPTATION AND MEANS OF DISPERSAL 

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. 

BEFORE entering into a discussion of the causes of the floating 
powers of seeds, it is necessary that I should state my general 
position on the relation between capacities of dispersal in the 
organic world and the question of adaptation. Adaptation runs 
through all the organic and inorganic worlds, and we cannot con- 
ceive an universe without it. The naturalist who looks only for 
the end in the purpose served makes but a partially legitimate use 
of the phrase. On the other hand, it has been improperly appro- 
priated by those who hold to the theory of Natural Selection, as 
indicating the result of small fortuitous variations that have 
chanced to be of service to the species in the struggle for existence. 
There is no question here of any end in view. Nature is repre- 
sented as working blindly, and the result of such " fortuitous 
variation " is termed an adaptation. We cannot, however, pick 
and choose only adaptations that are very evident in their character. 
We must include everything in the organic world as an adaptation, 
whether apparent or not, that is in direct relation with the organism's 
conditions of existence. It is not conceivable that an organism 
can be adapted to conditions outside its environment, and yet 
many so-called adaptations are of this character. 

Nature and I here confess my belief in a determining agency 
working above and through all living and dead matter, but largely 
controlled and checked by the laws of the physical world Nature, 
as I apprehend, has never concerned herself directly with providing 

H 2 



ioo A NATURALIST IN THE PACIFIC CHAP. 

means of dispersal either for plants or animals. With regard to 
plants, she makes no direct provision for the distribution of their 
fruits or seeds. If she had done so, she would have employed 
some uniformity in her methods, as in the instance of the means 
of reproduction ; whereas the modes of dispersal are almost infinite 
in their variety. When I say that Nature makes no direct pro- 
vision for the dispersal of plants and animals, I mean not in the 
sense that a bird is adapted for an aerial life, or an aquatic plant 
for a more or less submerged existence. That a bird is often able 
to distribute its kind over a great area is the " accident " of its 
conditions of existence. In a similar way the wide distribution of 
the " ticks " that they carry round the world is due to the para- 
sitical habits of these insects, habits that have been acquired with- 
out any view to their mode of dispersal by birds. 

Similarly it cannot be said of seeds or fruits that are transported 
by birds, whether adhering to their plumage by means of hooks or 
hairs, or through some viscid excretion, or inclosed in soil adhering 
to the feet or legs, or carried in the stomach and intestines, that 
Nature has made any special provision for their dispersal. The 
dispersing agencies take advantage of certain capacities or charac- 
ters of a seed or fruit that have been developed in the plant for 
quite other reasons and in conformity with quite other principles. 
There may be mentioned as examples the mucosity of seeds, the 
fleshiness of fruits, the occurrence of hairs and prickles, &c. Yet 
as far as their connection with dispersal is concerned, such capacities 
and characters are blind results in the history of the plant's 
development, the dispersing agencies making use of what was 
not intended for them. 

"Adaptation to definite life-purposes," as Sachs terms it 
(Physiology of Plants, 1887, p. 122), is seen everywhere; but it 
is adaptation restricted to the organism's conditions of existence. 
It is not conceivable, as I have said, that an organism can be 
adapted to conditions outside its environment. If there is such 
a seeming adaptation, it is but a blind result, the accidental out- 
come of collision or contact between two sets of conditions. If 
we represent a number of these sets of conditions by several circles 
gradually increasing in size until they encroach on each other, we 
find that the circles lose their form and acquire a polygonal shape. 
All characters seemingly connected with modes of dispersal have 
only this indirect relation to such agencies ; and their utility in 
these respects is an accident in the plant's life. They have not 
been acquired in connection with the dispersing medium, but are 



xi ADAPTATION AND MEANS OF " J^SPER&AL ib* 

the products of the laws of growth and heredity, guided by a 
determining agency, and acting within the organism's conditions 
of existence. It is within these narrow limits that all evident 
adaptations lie. In matters outside the conditions of the develop- 
ment of seeds and fruits, the evolutionary or determining principle 
" lets them go." Detached from the plant, they come in contact 
with conditions for which they were never created. The predo- 
minant power in Nature, that brings to a successful issue the 
development of an organism, has its limitations, and this is one of 
them, the evolutionary or determining influence being ever checked 
and hampered by the laws of the inorganic world. 

I can only refer briefly to some of the reasons that have led me 
to apply this view of the duality of forces in Nature to the subject 
of plant-dispersal. The principles of evolution and adaptation 
rule the world except in matters of dispersal. Take, for instance, 
the fleshy fruits which the gardener often makes more attractive 
to birds than they are in the wild condition. The result is cer- 
tainly to increase their facilities for dispersal by birds ; but such 
a result was as little intended by man as it was by Nature when 
species of Cornus, Ficus, Prunus, Viburnum, and other genera 
matured their drupes, berries, and fleshy fruits in the Cretaceous 
epoch. 

Children are now taught in several excellent little books on 
" Nature-Study " that fleshy fruits are specially adapted to be eaten 
by animals to secure the distribution of the seeds. We read in one 
book that plants produce these fruits " on purpose to be eaten," in 
another that they are " intended to be eaten," and in a third that 
the seed-coverings are adaptations, all with the ulterior object of 
distribution by frugivorous animals. I must be pardoned if I 
venture to express my dissent from these statements, more espe- 
cially since they are made by authors from whom it might be 
thought almost impertinent for me to differ. Yet authority can 
be claimed for holding the opposite view. 

When the botanist speaks of " useless secretions " in a plant, he 
is alluding amongst other things to the sugar and organic acids of 
fruits. " How and why all these substances originate is," as Pro- 
fessor Sachs observed in the work before quoted, " not known." It 
is, however, suggested by Dr. Kerner, in his Natural History of 
Plants (Engl. edit, i, 460 462), that such secretions, though useless 
to plants, may exist for the purpose of alluring animals to assist in 
seed-dispersal. There are some botanists, it may be remarked, 
that would reject such a view of the nature of fruits. Dr. Stapf in 



J.C2 A NATURALIST IN THE PACIFIC CHAP. 

his memoir on the flora of Kinabalu observes in this connection 
that the fact that a fruit is fleshy and attractive to birds is " no 
proof that it is really devoured by them, and still less that it is 
dispersed by them." Neither in fleshy fruits, nor in minute seeds, 
nor in seeds capable of being transported by the wind does he 
regard the general object of the particular character as primarily 
to act as a means of dispersion. 

The same plea is made for the mucosity of seeds like those 
of Capsella and Plantago (see Note 43), or for the " stickiness " of 
other seeds and fruits like those of Pisonia, qualities that favour 
adherence to passing objects. This is the reason, we are told, why 
seeds are " sticky." Such secretions I infer are often materials lost 
to the plant ; and being in that sense excretory we are not called 
on to supply a use for them. They can, therefore, not be regarded 
as having any teleological significance, since adaptation arises only 
from the requirements of the plant's conditions of existence. If 
they are serviceable in assisting the distribution of seeds, such an 
event can only be described as an accident in the plant's life arising 
from chance contact with another environment. 

The appendages of seeds and fruits, such as hooks and hairs, 
that render them liable to adhere to fur or feathers, are also 
regarded as special adaptations to this end. Without entering into 
the physiological significance of hairs and prickles generally, con- 
cerning which, as many of my readers will know, much might be 
said not in favour of such a view, I would refer to cases like that of 
Caesalpinia Bonducella, where the large prickly pods could not 
possibly be intended to aid the plant's dispersal, whilst the leaf- 
branches are also prickly, and the seeds are well known to be dis- 
tributed by the currents. There are other cases like that of Bidens 
cernua where the achenes, by reason of their barbed bristles, and on 
account of a layer of " buoyant tissue " in the fruit-coats, are dis- 
persed both by birds and by water. We may fitly ask to which 
capacity the theory of adaptation should be applied. Spiny fruits 
may be sometimes so large, as in the instance of Trapa natans, 
that the question of adaptation to dispersal cannot be raised. 

The great variety of the modes of dispersal of seeds is in itself 
an indication that the dispersing agencies avail themselves in 
a hap-hazard fashion of characters and capacities that have been 
developed in other connections. Seeds and fruits, having developed 
certain characters under a particular set of life-conditions, on being 
detached from the parent plant are brought into contact with con- 
ditions quite outside their original environment. Qualities and 



xi ADAPTATION AND MEANS OF DISPERSAL 103 

capacities are then brought into play which have no connection 
with the life-history of the plant. The care with which the mother 
plant guards the maturing seeds, and the protection of the environ- 
ment, are at a certain period withdrawn, and the seeds are left to 
take their chance under strange conditions. It would be idle 
to see anything purposeful in the waste that results. Rather 
we would see in it the effect of one of the numerous limitations of 
the determining or evolutionary power in Nature. Such a power 
has to adapt its workings to the laws of the physical world, checked 
here, frustrated there, at times, as in this particular case, losing all 
control, but in the end prevailing. 

My general position may be thus summarised. As concerning 
the distribution of fruits and seeds, the dispersing agencies take 
advantage of characters and capacities that were never intended 
for them, characters and qualities indeed that are often only 
brought out in relation to another environment. Thus no question 
of adaptation as regards means of dispersal can arise, since such 
capacities for dispersal have no connection with the plant's life- 
history. That seeds are dispersed at all is a blind result of the 
ever-continued struggle between the opposing forces of evolution 
and adaptation ; that is to say, between the determining power 
that lies behind organic life and the physical conditions to which it 
has to adapt its ends. 



CHAPTER XII 

THE CAUSES OF THE BUOYANCY OF SEEDS AND FRUITS OF 
LITTORAL PLANTS WITH ESPECIAL REFERENCE TO THOSE 
.OF THE PACIFIC ISLANDS 

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. 

IN the following pages I have adopted in its main features the 
classification of buoyant seeds and fruits employed by Professor 
Schimper in his work on the strand-flora of the Indo-Malayan 
region. The causes of buoyancy, as he points out, are very various, 
but they can be arranged in a few categories ; each category, how- 
ever, usually admitting great variety within its limits. It is this 
want of uniformity that first attracts our attention when we 
come to study the structure of seeds and fruits from the standpoint 
of their buoyancy. Whilst in the Pacific I went over most of the 
field traversed by Professor Schimper in Malaya (the majority of 
littoral plants of these regions being common to both), and as a 
result I have added not a few plants to his original groups. 

It will be seen from the following synopsis that there are three 
principal groups. The first group includes those seeds and fruits 
where the buoyancy is derived from unfilled space in the seed or 
fruit cavity. The second group comprises those seeds or fruits 
where the floating power is due to the buoyant kernel or nucleus. 
The third group includes those where the buoyancy arises from the 
existence of air-bearing tissue in the coverings of the seed or 
fruit. 

The first two groups I will term the mechanical or non-adaptive 
groups, not only on account of the structure inducing the buoyancy, 



CH. xii CAUSES OF BUOYANCY OF SEEDS AND FRUITS 105 

but because, as Professor Schimper remarks, the same structure 
often occurs with inland fruits and seeds possessing little or no 
floating power. In many of these cases, as he points out, the 
question of adaptation to dispersal by ocean currents cannot, there- 
fore, be raised. The third group may be named the adaptation 
group, because it is on these examples of buoyant seeds and fruits 
that this investigator chiefly based his contention that in the main 
the structures concerned with buoyancy represent adaptations to 
dispersal by currents effected through the agency of Natural Selec- 
tion. It is accordingly to this group that Professor Schimper 
especially directed his attention, and the result of his observations 
made in the home of the plants and of his investigations in the 
laboratory has been the elucidation of many difficult points in the 
structure of their fruits and seeds. To the two "mechanical" 
groups he did not pay the same attention ; and as their examina- 
tion came more within the limits of my own capacity as an inquirer 
I have worked them out with some detail, the subdivisions of the 
first group being my own as well as much of the material. 

Synopsis of the buoyant fruits and seeds of littoral plants of the 
tropical Pacific classified according to the cause of buoyancy. (The 
authorities are indicated by the initial letter, S = Schimper, 
G = Guppy. Details are given under some of the species in 
latter part of volume.) 

FIRST GROUP. The floating power is derived from un- 
occupied space in the cavity of the seed or fruit, no 
part of the seed or fruit as a rule possessing independent 
floating power. 

SUB-GROUP I., where the seed is concerned. 

SECTION I. The seeds have little or no albumen, and 
neither the tests nor the seed-contents have any 
buoyancy. The cotyledons are generally large, 
foliaceous, and crumpled or folded, or otherwise 
arranged, so that the seed-cavity is incompletely 
filled. 

S. G. Hibiscus tiliaceus. 

G. Hibiscus diversifolius. 
S. G. Thespesia populnea. 
S. Suriana maritima. 
G. Kleinhovia hospita, variable. 
S. G. Colubrina asiatica. 



io6 A NATURALIST IN THE PACIFIC CHAP. 

S. Dodonaea viscosa. 

G. Argyreia tiliaefolia, variable. 

G. Ipomea bona nox, variable. 

G. Ipomea glaberrima, Boj. 
S. G. Ipomea grandiflora. 
S. G. Ipomea pes caprae. 

G. Ipomea turpethum, variable. 

G. Cassytha filiformis. 

S. Euphorbia atoto. 

Notes. The species marked " variable " have seeds that some- 
times sink and sometimes float. With the exception of Kleinhovia 
they are only at times littoral in station. 

The plants of the British flora are represented by Convolvulus 
soldanella and C. sepium, the last being "variable" and not a 
littoral species. 

SECTION II. All the seeds belong to the Leguminosse. 
Neither the tests nor the seed-contents have any 
buoyancy, the floating power arising from a large 
central cavity produced by the bending outward of 
the cotyledons during the final shrinking stage of the 
maturation of the seed. 

S. Mucuna (generically). 
G. Mucuna urens D.C. (Hawaii). 
G. Mucuna, species of. 
S. G. Vigna lutea. 
S. G. Caesalpinia bonducella. 
G. Caesalpinia bonduc. 
G. Entada scandens. 

SUB-GROUP II., where the fruit is concerned. 

SECTION III. The seed only partially fills the fruit- 
cavity, and as a rule is not buoyant. The fruit shell, 
usually woody, may be also buoyant. 
S. G. Heritiera littoralis. 
G. Smythea pacifica. 
G. Dalbergia monosperma. 
S. G. Derris uliginosa. 
S. G. Pongamia glabra. 

G. Desmodium umbellatum. 
G. Gyrocarpus jacquini. 



xii CAUSES OF BUOYANCY OF SEEDS AND FRUITS 107 

SECTION IV. The floating power is derived from empty 
seed-cavities, where owing to abortion of the ovule 
or some similar cause the seed is not developed. 
S. G. Morinda citrifolia. 
G. Premna tahitensis. 

Note. Professor Schimper, in the case of Morinda citrifolia, 
holds the view that we have here a special adaptation to dispersal 
by currents. 



SECOND GROUP. Here the floating power is due mainly or 
entirely to buoyant kernels. In the case of seeds the 
tests are non- buoyant; but with "stones" the floating 
capacity may be aided by a layer of air-bearing tissue 
inside the shell. 

SECTION I. Non-Leguminous. 

S. G. Ximenia americana (drupe). 

S. G. Calophyllum inophyllum (drupe). 

Note. Professor Schimper would place these two plants in the 
second section of the third group on account of the layer of air- 
bearing tissue inside the shell of the " stone " ; but they are 
assigned to this section, since the floating power is mainly due to 
the buoyant kernel. 

Arenaria (Honckeneya) peploides, a British beach plant, belongs 
here. 

SECTION II. Leguminous seeds. 
G. Dioclea. 

G. Strongylodon lucidum. 
S. Canavalia (generic). 
G. Canavalia sericea. 
S. G. Canavalia obtusifolia. 

S. Erythrina (generic). 
S. G. Erythrina indica. 

P. Erythrina ovalifolia (Penzigj. 
S. G. Sophora tomentosa. 
G. Afzelia bijuga. 
G. Lathyrus ? 

THIRD GROUP. The floating power is due to the presence 
of air-bearing tissue in the seed-tests or fruit-coats. 



io8 A NATURALIST IN THE PACIFIC CHAP. 

SECTION I. The buoyant tissue occurs at the outside or 
forms the periphery of the seed or fruit. Unless 
otherwise indicated the fruit is implied in the list 
below. 

S. G. Carapa moluccensis (seed). 
S. G. Carapa obovata (seed). 

G. Inocarpus edulis. 

G. Serianthes myriadenia. 

G. Parinarium laurinum. 
S. G. Barringtonia speciosa. 

G. Barringtonia racemosa. 
S. G. Pemphis acidula (seed). 

S. Terminalia (generic). 
S. G. Terminalia katappa. 

G. Terminalia litorea. 

S. Lumnitzera (generic). 
S. G. Lumnitzera coccinea. 
S. G. Guettarda speciosa. 

G. Wedelia strigulosa. 
S. G. Scaevola Kcenigii. 
S. G. Cerbera Odollam. 

G. Ochrosia parviflora. 
S. G. Cordia subcordata. 
S. G. Tournefortia argentea. 
S. G. Clerodendron inerme. 

G. Vitex trifolia. 

G. Vitex trifolia, var. unifoliolata. 

G. Tacca pinnatifida (seed). 

S. Nipa fruticans. 

S. Cocos nucifera. 

G. Scirpodendron costatum. 



Additions of shore-plants from Malaya and tropical America 
mostly given in Schimper's work on the Indo-Malayan strand- 
flora. 

S. Cynometra cauliflora. 
S. Conocarpus erectus. 
S. G. Laguncularia racemosa. 
S. Lumnitzera racemosa. 
S. Sonneratia (seed). 
S. Barringtonia excelsa. 



xii CAUSES OF BUOYANCY OF SEEDS AND FRUITS 109 

S. Scyphiphora hydrophyllacea. 
S. Wollastonia glabrata. 
G. Hippomane mancinella. 

Note. Here belong a species of Vitex, probably V. agnus castus, 
the fruits of which occur in the stranded drift of the Sicilian 
beaches, and also the British littoral shore-plants, Cakile maritima, 
Crithmum maritimum, Matricaria inodora, and Scirpus maritimus. 

SECTION II. The buoyant tissue forms a layer inside the 
hard test of a seed or inside the shell of he " stone " 
of a drupaceous fruit, and to this cause the floating 
power is mainly or entirely due. 

G. Mucuna gigantea (seed). 

S. Hernandia peltata. 

S. Excaecaria agallocha. 

S. Cycas circinalis. 

S. Pandanus odoratissimus. 

G. Anona paludosa (seed) of tropical America. 

Note. I have followed Schimper in respect to Pandanus, but 
it might be by some placed in the first section of this group. 

Here belongs Euphorbia paralias, a British littoral plant, the 
buoyant seeds of which occur in the stranded seed-drift of English 
and Mediterranean beaches. 

In the following general discussion of the groups, reference will 
be made only to the plants best illustrating the different varieties 
of structure connected with buoyancy ; whilst mention of the other 
plants will in some cases be found in other parts of this volume, as 
shown in the Index ; and the matter is discussed at some length in 
not a few of the species. 

THE FIRST GROUP. 

Of the first group, where the floating power is due to the un- 
occupied space in the cavity of the seed or fruit, the Convolvu- 
laceae offer the most typical examples. Here as a rule the 
crumpled embryo fills the seed-cavity more or less incompletely ; 
and it is on the relative size of the unoccupied space that the 
sinking or floating of the seed depends. In those plants where the 
seed sinks the seed-cavity may be almost filled, as in Ipomea 
tuberculata, or densely packed, as in Ipomea pentaphylla, and 



no A NATURALIST IN THE PACIFIC CHAP. 

in species of Cuscuta. When the seed floats, as with Ipomea 
pes caprae, I. glaberrima, &c., the unoccupied space is relatively 
large ; and when, as with I. bona nox and I. turpethum, the 
behaviour of the seeds is irregular, some floating, and others 
sinking, a corresponding variation exists in the extent to which 
the seed-cavity is filled. This applies also to the irregular 
behaviour of the seeds of Ipomea peltata and of Argyreia 
tilisefolia. A singular instance is afforded by the seeds of 
Ipomea insularis, collected by me in Fiji and Hawaii. Those 
from Fiji were incompletely filled, and consequently buoyant. 
Those from Hawaii were more densely packed and sank. 
. . . The three British species of Convolvulus illustrate the 
same principle, namely, C. arvensis, with non-buoyant seeds ; 
C. soldanella, with buoyant seeds ; and C. sepium, with seeds 
irregular in behaviour. 

In the case of plants of the Corivolvulaceae, possessing buoyant 
seeds, there is always evidence of marked shrinking of the seed- 
contents before the final setting and hardening of the seed-coats. 
The embryo often appears shrivelled and dried up, and is almost 
brittle, so that large spaces are produced in the seed-cavity. If 
we partly divide such a seed and place it in water, the embryo 
absorbs water rapidly, and within an hour is soft, healthy-looking, 
and much swollen, the interspaces being filled with a jelly-like 
mucilage. It is therefore evident that absolute impermeability 
of the seed-coats is essential for the successful transport by sea- 
currents of the floating seed ; and we can only suppose that the 
shrinking of the seed-contents takes place before the final setting 
of the tests. That with the buoyant seeds the coats are quite 
waterproof was illustrated in many of my experiments where, after 
a period of flotation covering several months, and sometimes a 
year or more, the seed-contents were still quite dry and shrunken. 
The limit of buoyancy, as I have shown in Chapter IX., depends 
on an attempt at germination on the part of the floating seed, 
which then absorbs water, softens, swells, and sinks. 

It is, therefore, not a matter of surprise that non-buoyant seeds 
of the Convolvulacese do not gain floating power after prolonged 
drying of many months. It is also to be expected that, as we find 
in Fiji, when a characteristic shore-species with buoyant seeds like 
Ipomea pes caprae extends far inland, the seeds retain their floating 
powers. Seed-buoyancy of this description is, on the face of it, 
purely mechanical. 

Another type of the buoyant seeds of the first group is 



EXPLANATION OF THE DIAGRAMS ILLUSTRATING 
THE CAUSES OF SEED-BUOYANCY 

1. Entada scandens (natural size): (a), the shell; (), the kernel; (c), the inter- 

cotyledonary cavity. The shell consists of three coats an outer and an inner 
hard chitinous coat, and an intermediate layer of brown cellular tissue contain- 
ing little or no air. The buoyancy is due entirely to the central cavity, neither 
the seed-tests nor the seed contents possessing any floating power (see page 181). 

2. .}fiiinna itrens, from Hawaii (natural size). The kernel (b) sinks, and the shell has 

no floating power except where it possesses (under the raphe) a layer of dark 
brown, air-bearing, spongy tissue (a). This, however, is not sufficiently developed 
to endow the seed with buoyancy, which is due to the intercotyledonary cavity (c). 
' (see page in). 

C Miiriuia gigaiifea, from Fiji (natural size). The kernel (b) sinks, and the seed owes 

3. | its floating power entirely to the existence in the shell (a) of a layer of brown, 

4. I spongy, air-bearing tissue which is mostly developed at the circumference and is 

almost wanting at the flat sides of the seed (see page 115). 

Dioclea (vioiacea ?), from Fiji (natural size). Here the kernel (b} is buoyant and 

5. endows the seed with floating power. Though the shell (a) possesses a thick 

6. layer of reddish-brown cellular tissue, this tissue contains but little air and aids 
the floating power but slightly (see page 113). 

7. Strongylodon hiciduin, from Fiji (natural size). The floating power is due entirely 

to the buoyant kernel (b}. There is a very scanty amount of loose brown tissue 
(a) under the raphe ; but it has no appreciable effect on the buoyancy (see 
page 113). 

Ctesalpinia bondiicella and C. bonditc, from Fiji (natural size). Neither the seed- 
tests (a) nor the kernel (b) have any floating power in themselves, the buoyancy 
being connected with a large internal cavity (c), which normally is intercotyle- 
9. donary, as in Fig. 8 (C. bonducella). With both plants, but more especially 

IO . with C. bonduc (Figs. 9 and 10), there may be a lateral cavity (d), or the kernel 

may be loose in the shell (Fig. 10), but this does not necessarily imply buoyancy 
(see page 194). 

Arenaria peploides (enlarged : seeds 4 mm. in size). Here the curved embryo (a) 
sinks, and the spongy air-bearing albumen (b) gives buoyancy to the seed (see 
page 1 1 6). 

13. Euphorbia paralias (enlarged : seeds 3 mm. in size). The kernel (b) sinks, and the 

seed owes its buoyancy to a layer of air-bearing tissue (a) in the shell (see 
page 1 1 6). 

14. Aforinda citrifolia (enlarged pyrene 7 mm. long). The floating power is due 

to the bladder-like air cavity (a). The seed (b) proper is enclosed in the 
woody tissue behind the bladder (see page 112). 

15. Cucurbita (seed enlarged), from the Valparaiso beach-drift (see page 125). The 

kernel (b) has no buoyancy. The shell (a) is formed of two layers of air-bearing 
tissue, the outer composed of prismatic cells and the inner of a spongy vacuola- 
material. 



[ To face page in. 




Diagrams illustrating some of the causes of seed-buoyancy. 



xu CAUSES OF BUOYANCY OF SEEDS AND FRUITS in 

presented by several species of Leguminosae, as with Entada 
scandens, some species of Mucuna, and Caesalpinia bonducella. 
As with the Convolvulaceous seed, the embryo sinks and the seed- 
shell has no buoyancy; but here the floating power is due to 
the existence of a more or less symmetrical long central cavity 
produced by the arching or bending outwards of the large 
cotyledons which lie usually in close contact with the seed-shell. 
This arching outward of the cotyledons depends on a shrinking 
process in the setting or final stage of the maturation of the 
seed. The stages of the process may be traced in the immature 
seeds, which are much larger and in some cases twice the size of 
the mature seed. In this immature condition the seed-coats are 
soft, and the flabby fleshy and thick cotyledons fill up the seed- 
cavity. As the hardening and setting process continues, the 
cotyledons diminish in size, become firmer, and gradually bend 
outward, leaving a central cavity. This arching outwards is no 
doubt in part the result of the contraction of the seed-tests during 
the shrinking process. Considerable variation prevails in the 
results, and where the cavity is very small the seed sinks. Further 
details relating to this subject will be given in my treatment ot 
some of the plants, and especially under Caesalpinia. But it may 
be here remarked with reference to Hawaiian seeds of Mucuna 
urens D.C., that although they are strictly referable to this group, 
they display beneath the hard test, on the side beneath the raphe, a 
scanty layer of dark spongy air-bearing tissue which is sufficiently 
buoyant to float up detached portions of the test, but does not of 
itself give buoyancy to the seed. The significance of this structure 
will be subsequently pointed out. The seed owes its floating 
power to the large central cavity, but this layer of spongy tissue 
adds to its buoyancy. 

The section where the buoyancy of the fruit is connected with 
unoccupied space in the fruit-cavity is extremely heterogeneous in 
its composition. Every fruit has a method of its own, and the 
great variety of causes of buoyancy of a mechanical character is 
here exemplified. For instance, with Gyrocarpus jacquini and 
Cassytha filiformis the cause of buoyancy is in the main the same 
as that described in the case of the Convolvulacese. The origin of 
the floating power of the pods of Derris uliginosa is two-fold. In 
the first place the seed or seeds but partly fill the pod, and in the 
second place the seed is able to float of itself by reason of its 
possessing, as in the seeds of Entada scandens, a large central 
cavity produced by the arching out of the cotyledons during the 



ii2 A NATURALIST IN THE PACIFIC CHAP. 

final stage of maturation. A double cause is also to be assigned 
to the buoyancy of the fruits of Heritiera littoralis and of Smythea 
pacifica, where, in addition to the unoccupied space produced by 
the shrinking of the seed, the fruit-case itself floats, though nothing 
but a mechanical explanation is to be given of the floating of 
empty ligneous fruits. 

One of the most suggestive types of buoyancy belonging to the 
first group is presented by those cases, which are, however, not 
very frequent, where the floating power is to be attributed to 
empty seed-cavities produced by -the abortion of the ovule or 
failure of the development of the seed. A significant instance of 
this is afforded by the fruits of Premna taitensis, a coast plant. 
The buoyant " stone " of the drupe, which is often found afloat in 
the Rewa estuary in Fiji, is 4-locular, each cell containing normally 
one seed, but as a rule only one cavity contains a mature seed, the 
three other cavities becoming more or less empty through the 
failure of their seeds. It can be proved that neither the seeds nor 
the substance of the " stone " are buoyant, and that the " stone " 
owes its capacity of floating for months to the empty cavities 
arising from the failure in development of three out of the four 
seeds. In Fiji we see the rivers distributing these small fruits, and 
we find the " stones " stranded on the beaches and floating in the 
currents amongst the islands ; and there can be no doubt that this 
is one of the effective modes of dispersal of the species ; yet, if 
there was ever a case of accidental buoyancy concerned with 
dispersal by currents, we have it here. Further details are given in 
Note 32. , 

It is probably also to the abortion of the ovule, or to the 
failure of the seed, that the remarkable air-cavity (see Note 8) to 
which the pyrenes of Morinda citrifolia owe their floating power, is 
to be attributed. To this structure Professor Schimper (pp. 165, 
183, 200) attaches considerable importance as an example of 
special adaptation to dispersal by currents through the influence of 
Natural Selection. He suggests, however, that possibly its mor- 
phological significance may be found in^ its being a peculiarly 
modified seed-chamber. The case of Premna taitensis above cited 
indicates that the latter view is the most probable. The subject 
awaits a careful microscopical study of the seed-development of 
the genus Morinda since, as elsewhere remarked, the non-buoyant 
pyrenes of inland species have not such an air-chamber. An 
outline sketch of a pyrene of Morinda citrifolia is given in the 
preceding plate. A good figure of it occurs in Schimper's Plant 



xii CAUSES OF BUOYANCY OF SEEDS AND FRUITS 113 

Geography, p. 28. A very suggestive instance of this nature is 
described under Brackenridgea in Note 46 and in Chapter XIII. 

THE SECOND GROUP. 

Here are included those seeds and stone-fruits that possess 
buoyant kernels. Professor Schimper points out that since this is 
a feature both with inland as well as coast plants such a character 
cannot be viewed as an adaptation to dispersal by currents. The 
plants concerned belong mostly to the Leguminosae, and we find 
here some of the most widely spread of strand species, such as 
Canavalia obtusifolia and Sophora tomentosa, as well as some of 
the giant climbers of the coast forests belonging to the genera 
Dioclea and Strongylodon. The kernels when divested of their 
coverings float buoyantly, but they soon absorb water and sink 
usually in a day or two, a circumstance indicating that it is to the 
impervious coverings that they indirectly owe their capacity to 
keep the seed or fruit afloat. It is noteworthy that seeds of 
Strongylodon lucidum from Fiji display beneath the raphe a trace 
of an internal layer of loose cellular tissue which, however, has no 
appreciable effect on the buoyancy ; whilst with seeds of Dioclea 
(violacea ?) from the same locality there is a thick layer of loose 
tissue which aids the floating power of the kernel but is not of 
itself sufficiently aeriferous to buoy up the seed. 

This leads one to refer to two other plants belonging to this 
group, Calophyllum inophyllum (Guttiferae) and Ximenia ameri- 
cana (Olacineae), where, though the floating power is mainly due to 
the buoyant kernel, it is also aided by a layer of air-bearing tissue 
inside the hard shell of the "stone" of the drupe. Professor 
Schimper places these fruits in the third or adaptive group on 
account of the layer of buoyant tissue, but it would be more 
correct to class them according to the predominant cause of their 
buoyancy. It can be shown that with a non-buoyant kernel the 
" stone " no longer floats. This double cause of the floating power 
renders an explanation very difficult, since it would seem inde- 
fensible to give conflicting interpretations of their nature. With 
Ximenia americana there is another great difficulty. Its drupes 
are known to be dispersed by fruit-pigeons (Introd. Chall. Bot^ 
p. 46) ; and judging from the rare occurrence of the " stones " 
in the drift there is good reason to believe that bird agency in the 
Western Pacific is predominant in the dispersal of the plant. It is 
by such test cases as this that we must put to the proof the reality 
or non-reality of the influence of adaptation on seed -buoyancy. 
VOL. II I 



ii 4 A NATURALIST IN THE PACIFIC CHAP. 

THE THIRD GROUP. 

We have here those plants where the floating-power is entirely 
or mainly due to an air-bearing tissue in the seed-tests or fruit- 
coats. Several of the fruits are figured in Schimper's Indo-malay- 
ische Strand-flora^ and one or two are figured in the English 
edition of his work on Plant- Geography, p. 29. 

In the first section, where the buoyant tissue occurs at the out- 
side or forms the periphery of the seed or fruit, are included 
several of the most familiar of the littoral trees and shrubs of the 
Pacific islands, such as Barringtonia speciosa, Cerbera Odollam, 
Guettarda speciosa, Pemphis acidula, Scaevola Kcenigii, Terminalia 
katappa, and several others named in the synopsis. I cannot enter 
into detail here, but the reader will find fuller particulars of each 
plant in most cases in Professor Schimper's work, and in some 
instances in my separate discussion of the plants concerned. In 
nearly all cases we are concerned here with the fruits, and only in 
a few cases with the seeds, as with Carapa and Pemphis acidula. 

This investigator observes that to this sub-group belong the 
fruits and seeds usually described in systematic works as provided 
with corky or suberous coverings ; but he points out (p. 167) that 
the resemblance is nearly always quite superficial, and is limited to 
colour and consistence, suberous tissue occurring in only a few 
cases, as in the fruit-coats of Clerodendron inerme. The buoyant 
tissues, he remarks, are often more or less ligneous, and in those 
cases where there is no lignin reaction they resist the action of 
sulphuric acid much more effectively than pure cellulose ; whilst 
in their physical characters, as well as in their behaviour with 
reagents, they differ just as much from ordinary cork. Thus, they 
are but little elastic and often easily crumble away ; whilst in 
large fruits, like those of Cerbera and Terminalia, they would soon 
be stripped off entirely when subjected to the " wear-and-tear " of 
transport by currents, if they were not traversed by numbers 
of stout, tough fibres which hold the materials together. Where 
the buoyant tissues are firmer, as with Clerodendron inerme and 
Cordia subcordata, the fibrous framework is scanty or absent, 
whilst very small seeds or fruits, like those of Tournefortia argentea 
and Pemphis acidula, where the " wear-and-tear " would be com- 
paratively slight, often possess no protecting fibres in the buoyant 
tissues. 

In one or two fruits, like those of Cerbera Odollam, these 
tissues display large intercellular spaces ; but in the majority of 



xii CAUSES OF BUOYANCY OF SEEDS AND FRUITS 115 

cases such spaces are insignificant in size or absent altogether. 
Speaking generally, however, there is, as Professor Schimper 
observes, great similarity in the structure of the buoyant tissue in 
the coverings of these fruits and seeds. The cell-walls are thin or 
only slightly thickened, and detached air-bearing portions of the 
tissue will float for many weeks. The great floating capacity 
of these fruits and seeds is stated by this investigator to be 
entirely due to the tenacity with which the air is retained in the 
covering tissues. It is, however, noteworthy that in the case 
of Scaevola Kcenigii the fruits are just as well suited for dispersal 
by frugivorous birds as by the currents, a significant circumstance 
discussed in the next chapter. 

The second section contains those plants where the buoyant 
tissue occurs inside the hard shell of the fruit or seed, such as 
is found, for example, in Anona paludosa, Mucuna gigantea, 
Hernandia peltata, Cycas circinalis, &c. Professor Schimper here 
includes Calophyllum inophyllum and Ximenia americana ; but I 
have before remarked that the buoyancy of their fruits is mainly 
due to their buoyant kernels. This aeriferous tissue forms a layer 
between the seed or nucleus and the hard outer shell. It is 
described by the above-named authority as soft or friable and dark 
brown. The cells contain air and may be closely arranged or 
separated by small interspaces, their walls being neither woody 
nor suberous, 



The structure of the buoyant seeds and seedvessels of the littoral 
plants of the British flora. 

The littoral plants with floating seeds or fruits form but a 
section of the strand-plants of the British flora, scarcely a third, as 
is pointed out in Chapter IV., of the total number. Though small 
in number they exhibit great variety in structure ; and notwith- 
standing that as far as they have been examined they may all be 
referred to one or other of the groups and sections of the classifica- 
tion adopted in the synopsis for the plants of the Pacific islands, 
nearly every plant presents in the structure of its seeds or seed- 
vessels a type of buoyant structure different from the others. 

The first group is represented by the seeds of Convolvulus 
soldanella, which owe their floating power to the incomplete filling 
of the seed-cavity. The second group, where the buoyancy arises 
from the buoyancy of the kernel or nucleus, is illustrated by the 

I 2 



u6 A NATURALIST IN THE PACIFIC CHAP. 

seeds of Arenaria (Honckeneya) peploides, but in a fashion quite 
unique. The test is thin but impervious, and has no buoyancy ; 
the curved embryo also sinks ; and the floating power arises 
from the air contained in the loose spongy albumen, around which 
the embryo is coiled (see figure). A more normal component 
of the second group is represented in some Leguminous seeds, 
perhaps of Lathyrus maritimus, that occur regularly amongst the 
stranded seed-drift of the north coast of Devon. Here the kernel 
of the seed is buoyant. The seeds of Euphorbia paralias are 
indebted for their floating capacity to a layer of spongy tissue con- 
taining large air-spaces placed between the kernel and the 
chitinous outer test, neither of which possess any floating power 
(see figure). They thus belong to the second section of the third 
group. 

The fruits of Cakile maritima, Crithmum maritimum, Matricaria 
inodora, and Scirpus maritimus, all belong to the first subdivision 
of the third group where the air-bearing tissue exists in the 
peripheral coverings, the seed or nucleus in all cases sinking. With 
Cakile maritima there is a light spongy outer case of aeriferous 
tissue, which, however, soon loses the epidermis, a circumstance 
that probably explains the limited period of flotation of about a 
week. The walls of the mericarp of Crithmum maritimum are 
composed of spongy cellular air-bearing tissue with a persistent 
epidermis, and the floating powers of the fruits are consequently 
great. The achenes of Matricaria inodora have beneath the 
epidermis a layer of buoyant tissue, and their structure is similar to 
that found with the buoyant achenes of littoral species of Wedelia, 
plants of the same order of Compositae that are found on the 
Pacific islands. The cause of the floating power of the fruits of 
Scirpus maritimus lies entirely, according to Kolpin Ravn, in the 
air-bearing cells of the epidermis. The reader will find the results 
of my experiments on the buoyancy of the seeds in Notes 16, 17, 
and 1 8. 

Summary of the Chapter. 

(i) Following the main lines of Schimper's classification of 
those of the Indo-Malayan region which possesses for the most 
part the same species, the buoyant seeds and fruits of the littoral 
plants of the Pacific islands are classed in three groups : the first 
where the cavity of the seed or fruit is incompletely filled, the 
floating power arising from the empty space ; the second where the 



xii CAUSES OF BUOYANCY OF SEEDS AND FRUITS 117 

buoyancy is derived from the buoyant nucleus or kernel ; and the 
third where it arises from air-bearing tissues in the coats of the seed 
or fruit. 

(2) The first and second groups, in which the question of 
adaptation to distribution by currents through the agency of 
Natural Selection is not raised, since the same structural characters 
are found in seeds and fruits of inland plants not dispersed by the 
currents, are termed the mechanical or non-adaptive groups. The 
third is distinguished as the adaptive group, because it is here that 
Schimper finds evidence in favour of the Selection Theory. 

(3) The first group is best represented by the Convolvulaceous 
and the Leguminous types. In the former, which is well illustrated 
by Ipomea pes caprae, the seed-cavity is imperfectly filled by the 
crumpled embryo, the result of the shrinking process during the 
final setting of the seed. In the latter, which is exemplified by 
Entada scandens and Caesalpinia bonducella, the seed displays a 
large central cavity produced by the arching outward of the 
cotyledons during the shrinking process accompanying the last 
stage of the maturation of the seed. As an instance of fruits 
belonging to the group, those of Heritiera littoralis'may be cited. 
An uncommon type is presented in the " stones " of the drupes of 
Premna taitensis, and in the pyrenes of Morinda citrifolia, where 
the buoyancy arises from empty seed-cavities resulting from the 
failure of some of the seeds. 

(4) The second group with buoyant kernels includes mostly 
widespread Leguminous species, such as Canavalia obtusifolia and 
Sophora tomentosa. 

(5) The third or "adaptive" group comprises many of the 
characteristic littoral trees and shrubs of the Pacific islands, such 
as Barringtonia speciosa, Guettarda speciosa, Terminalia katappa, 
Tournefortia argentea, &c., that contain in their fruit-coverings a 
buoyant cork-like material often bound together by fibres, but 
which proves on examination to resemble cork only in appearance. 
In another type, illustrated by the fruits of Cycas circinalis and the 
seeds of Anona paludosa, the buoyant tissue forms a layer inside 
the shell of the seed or "stone." 

(6) Some fruits like those of Ximenia americana and Calo- 
phyllum inophyllum illustrate both the so-called mechanical and 
adaptive principles in their structure ; whilst with the first-named 
species they are as well adapted for dispersal by frugivorous birds 
and are known to be a favourite food of fruit-pigeons. The same 
difficulty arises with the fruits of some other characteristic littoral 



n8 A NATURALIST IN THE PACIFIC CH. xn 

plants, as with Scaevola Kcenigii, the drupes of which are equally 
well fitted for dispersal by birds and currents. 

(7) The same general principles have been at work in determin- 
ing the structures concerned with the buoyancy of the fruits and 
seeds of British littoral plants. Although the species are few in 
number they exhibit in this respect great variety, eight species 
illustrating six or seven types of buoyant structure. 



CHAPTER XIII 

ADAPTATION AND SEED-BUOYANCY 

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. 

WHEN we speak of a certain structure as an adaptation to dispersal 
by currents through the agency of Natural Selection, it is necessary 
at the outset to be quite clear as to what is implied. Professor 
Schimper, who brought his great and varied knowledge of many 
other phases of plant-life to bear on this subject, is careful to clear 
the ground of preliminary erroneous conceptions in such a per- 
spicuous and impartial manner that we cannot do better than follow 
his guidance. There are, he observes (p. 178), many mechanisms 
or contrivances in plants, which, though they seem to have arisen 
with a fixed purpose, can in no wise be regarded as having been 
developed for that end, since they were produced in quite a different 
connection and have merely acquired a new or supplementary 
function, of which they are the cause and not the effect. 

This is very much the position that I have taken up for the 
whole subject of the relation between plants and their dispersing 
agencies, and it will be found discussed in Chapter XI. It involves, 
as I venture to think, a dominant principle in the organic world, 
which it is one of the objects of this work to emphasise, namely> 
that Nature in dispersing plants habitually makes use of structures 
and capacities that were originally developed in quite another 
connection. Behind this change of function, this new purpose, lies 
the secret of the organic world. There is for me no more pregnant 
fact in plant-life than the thistle-seed blown before the wind, or the 
seed of our sea-convolvulus floating in the sea. It proves to my 
mind that the evolutionary power in nature is checked and 



120 A NATURALIST IN THE PACIFIC CHAP. 

hampered by conditions not of its own creation, and that two 
opposing forces are ever at work, the one creating and the other 
limiting the creative power, the actual mode of dispersal being but 
a blind and accidental result of the struggle. 

The question of the operation of Natural Selection is not raised, 
as Professor Schimper indicates, until we consider whether the new 
function has had any bettering influence on the structure or 
mechanism with which it has come to be concerned. If such a 
modification is thus brought about it might be legitimately claimed 
as a result of this agency, and the term " adaptation " could be 
used. But if there is no evident change produced, we should be 
compelled to assign very subordinate limits to the capacity of 
Natural Selection ; and in the instance of buoyant fruits and seeds 
it would be restricted to determining a plant's station by the water- 
side and in increasing its area. It is only in the first case that we 
could speak of them as adaptations in the meaning attached to this 
term in the language of the Selection Theory. It would at first 
sight seem easy to ascertain whether the characters of fruits and 
seeds, to which the buoyancy is due, are adaptations in this sense 
of the word ; but in reality it is far from being so. We can, how- 
ever, proceed with unanimity up to a certain stage in the argument ; 
but there agreement ends. 

It has been before established that in the Pacific islands, and 
indeed in the tropics generally, the plants with buoyant seeds or 
seedvessels are mainly stationed at the coast. It has also already 
been shown that this littoral station is often associated with a 
special buoyant-tissue in the coverings of the seed or fruit ; and it 
will now be pointed out that this tissue is, as a rule, absent or but 
scantily developed in the case of inland species of the same genus. 
Of great importance, remarks Professor Schimper (p. 179), in 
relation to the Selection Theory and the development of adapta- 
tions, is the comparison of the fruits and seeds of strand-plants 
with those of allied inland species ; and he finds here evidence in 
support of the Darwinian view. He takes the cases of the genera 
Terminalia and Calophyllum, which contain both inland and littoral 
species ; and he shows that although the same buoyant-tissue occurs 
in the fruit-coats of inland species, it is there much diminished, and 
in consequence the floating powers are considerably lessened or lost 
altogether (see Chapter II.). It is not pretended that this tissue 
has had any connection in its origin with dispersal by currents, but 
merely that its greater development in the shore species is an 
adaptation to this mode of transport. 



xiii ADAPTATION AND SEED-BUOYANCY 121 

Further testimony is adduced by this investigator (p. 182) in 
supporting his view in the fruits of the genera Barringtonia, 
Clerodendron, Cordia, and Guettarda, where the buoyant tissues 
extensively developed in the coast species are either non-existent 
or only represented by a trace in the inland species of the same 
genus, a difference in structure associated with the loss or great 
diminution of the floating capacity of the fruits concerned. I have 
been able to establish other examples in the cases of the genera 
Scaevola and Tacca, which will be found referred to in Chapter II. 

Professor Schimper (p. 200) points to the circumstance that the 
" adaptations " in these fruits all belong to the diagnostic marks 
of the genera and the species, and contends that these plants 
abundantly prove the erroneous nature of the contention that 
Natural Selection could have played no part in the elimination of 
the strand-flora. My own contention is that Natural Selection has 
played such a part, but that in doing so it has merely availed itself 
of characters previously existing, without originating, modifying, or 
improving them in any way. The foregoing evidence might with 
equal fitness be employed to show, as pointed out in Chapter II., 
that in the course of ages there has been a great sorting process by 
which, excluding the mangroves, plants of the xerophilous habit 
possessing buoyant seeds and fruits have been sorted out and placed 
at the coast. Direct evidence does not lead us farther than to the 
establishment of a littoral station for plants thus endowed. The 
problem whether the characters of their fruits and seeds that are 
concerned with buoyancy may be regarded as adaptive in the 
Darwinian sense lies beyond the reach of direct testimony. We 
can, however, approach it from the outside by several directions, 
and from some of these we will now proceed to deal with it. 

There is first the singular circumstance that in Fiji, when the 
littoral plants with buoyant seeds or fruits leave the beach and 
extend far inland, they, as a rule, retain their floating powers 
and, of course, their buoyant structures. I found this to be true of 
Cassytha filiformis, Cerbera Odollam, Ipomea pes caprse, Morinda 
citrifolia, Scaevola Kcenigii, and one or two other plants mentioned 
in Note 44, where this subject is discussed. My experiments 
on these plants indicated that their fruits or seeds floated equally 
long, whether obtained from coast or from inland plants. 
This, at first sight, appears to present a serious objection to the 
adaptation theory ; but it was not so regarded by Professor 
Schimper, who in a letter to me, dated March 8th, 1900, observed 
that he did not see " why littoral plants growing inland should lose 



122 A NATURALIST IN THE PACIFIC CHAP. 

their adaptations to littoral life, especially if those adaptations are 
not conflicting with the conditions of life beyond the littoral 
zone, and if the competition does not require special adaptations." 

My view, however, is that any process of adaptation is 
unnecessary. All these plants, it is contended, were originally 
inland plants that acquired the buoyant qualities of their seeds and 
fruits in the inland stations, and ultimately found a station at the 
coast through the sorting process above referred to. In the case of 
plants like Ipomea pes caprae and Cassytha filiformis this would 
be conceded, since they belong to the acknowledged non-adaptive 
groups discussed in the preceding chapter. It is only to some of 
these plants, such as Scsevola Kcenigii and Cerbera Odollam, that 
the adaptation view of Professor Schimper is applied ; and the 
question arises whether we are justified in making such a distinction, 
or, in other words, whether it is antecedently probable that two 
independent principles have been at work in determining the 
fitness of seeds and fruits for dispersal by the currents. 

The plants for which the influence of adaptation through Natural 
Selection is claimed belong, as stated in Chapter XII., almost 
entirely to the third group. It is admitted that with the other two 
groups the utmost that any sorting or selecting process would effect 
would be to determine a station at the coast and to extend the area 
of distribution. The numerical aspect of the question therefore 
acquires some importance ; and the reader's attention is accordingly 
directed to the results tabulated in Note 45, where it is shown 
(assuming for the time that there is no difference of opinion 
about the adaptive significance of the seeds and fruits concerned) 
that the plants of the third or adaptive group make up only about 
half the total. It would therefore appear that if the agencies of 
Natural Selection have been at work here either in bettering or 
in developing buoyant structures, half of the shore-plants with 
buoyant seeds or fruits have not come within their influence. 

But the subject takes another aspect when we reflect that in 
some buoyant fruits, as with Ximenia americana and Calophyllum 
inophyllum, the two principles would seem to have been at work. 
Whilst from this standpoint Natural Selection is regarded as 
having either developed or increased in amount the layer of 
buoyant tissue in the fruit-coats, the buoyant kernels are not viewed 
as adaptive in their origin. In the case of Ximenia americana the 
dispersing agency of frugivorous birds adds another factor, since, 
as before stated, its drupes are known to be dispersed by fruit- 
pigeons. In the cases of Scsevola Kcenigii and of Vitex trifolia, 



xin ADAPTATION AND SEED-BUOYANCY 123 

two plants belonging to the adaptive group, Professor Schimper 
(pp. 156, 1 88) admits also the dispersing agency of frugivorous 
birds, and he claims it for Morinda citrifolia, in the pyrenes of 
which he also detects a special adaptation to dispersal by currents. 
It may be added that, as he also points out, fruits of the non- 
adaptive group of littoral plants, such as Premna integrifolia 
(P. taitensis) and Cassytha filiformis, would sometimes also attract 
birds. In fact, those of the last-named have been found in the 
crops of pigeons (Introd. Chall. Bot., p. 46). 

Looking at all these littoral plants with fruits that are equally 
fitted for dispersal by birds and by currents, we may now ask, 
Where does the general principle of adaptation to dispersal lie ? 
Whatever view we adopt, we must apply the same view to all, 
whether it be a question of dispersal by birds or by currents. We 
cannot choose between two sets of principles determining the 
buoyancy of seeds and fruits any more than we can regard a 
fleshy drupe and a buoyant seed as illustrating different principles 
regulating the dispersal of plants. Nature works with uniformity 
in these matters, and if the Natural Selection theory is held to 
explain one case it ought to account for all. Yet nobody would 
go so far as this ; and this view of dispersal is on many grounds 
antecedently improbable. These difficulties disappear if we assume 
that in all cases the dispersing agencies have without modification 
made use of characters and capacities that were developed, as we 
now see them, in quite other connections and under quite other 
conditions. 

It will now be necessary to look a little closer into the subject 
of the buoyant tissue, to the existence of which in their coats about 
half of the littoral plants concerned owe the floating power of 
their fruits or seeds. In the first place, it is to be remarked that in 
the case of some of the seeds of the plants of the non-adaptive 
groups it is also represented to a small degree in the seed-coats, 
although, as with Strongylodon lucidum and Mucuna urens, it is 
not present in sufficient amount to float the seed. In the next 
place, it should be noted that with some genera possessing, like 
Terminalia, both inland and coast species it is to be found alike in 
the fruit-coverings of inland and of littoral plants, though in a less 
degree in the case of the fruits of inland species, the floating power 
of which is proportionately diminished. There are, however, a 
few cases where this buoyant tissue is developed in inland species 
which belong to genera or subgenera that have no littoral species. 
This is what we would expect, if Natural Selection has merely 



i2 4 A NATURALIST IN THE PACIFIC CHAP. 

concerned itself with placing plants of xerophilous habit possess- 
ing buoyant seeds or fruits at the coast. Under such conditions we 
would now and then expect to find an inland plant possessing 
buoyant fruits or seeds of this description that has never been able 
to establish itself at the coast. 

A good instance is afforded by Pritchardia Gaudichaudii, a fan 
palm peculiar to Hawaii, the drupes of which float for several 
weeks and have a covering of spongy buoyant tissue (see Chapter 
XXV.). The seeds of Hibiscus Abelmoschus, a species dis- 
tinguished subgenerically from the littoral Hibiscus tiliaceus, 
offer another example. They float for months, and owe their 
buoyancy to a layer of air-bearing tissue between the kernel and 
the test, in this respect differing from the seeds of the littoral 
species, where the floating power is due to unoccupied space in the 
seed-cavity. The buoyancy of the seeds of Hibiscus Abelmoschus 
thus offers another example of ineffectual floating power, since it 
is not a littoral plant, is often cultivated, and has accompanied 
aboriginal man over much of the tropical zone. 

A singular instance of the dispersal by currents of an inland 
plant that occurs both wild and cultivated in tropical America, the 
West Indies, and on the West Coast of Africa, is afforded by 
Spondias lutea, Linn., which is referred to at the end of Chapter 
XXXII. Its "stones," which are provided with a cork-like cover- 
ing much as we find with those of Cordia subcordata and Guettarda 
speciosa, possess great buoyancy, and are found in the river and 
beach drift of those regions with the seeds in a sound condition. 

A very remarkable case of ineffectual buoyancy is presented 
by the seedvessels of Brackenridgea, which have been found 
floating in the drift off the coast of New Guinea. They owe their 
floating power to closed cavities which would seem to arise from 
the failure of one of the seeds or from the abortion of an ovule. 
But, according to Beccari, their fleshy coverings would aid their 
dispersal by frugivorous birds ; and since the species are all much 
localised and are rarely littoral in their habit, it is very probable 
that birds have mainly effected the dispersal of the genus (see 
Note 46). It has, however, been shown in the previous chapter 
that Premna taitensis and Morinda citrifolia owe their dispersal by 
currents to similar cavities in the seeds or " stones." 

Amongst the inland plants possessing seeds or fruits that are 
dispersed by the currents without aiding the distribution of the 
species may be recognised types of both the adaptive and non- 
adaptive groups. A singular instance is afforded by the large 



xin ADAPTATION AND SEED-BUOYANCY 125 

seeds almost an inch long of a huge pumpkin (Cucurbita) which, in 
sound condition, form one of the commonest constituents of the 
beach drift on the coast of Chile from Valparaiso northward to 
Iquique. The fruit is commonly eaten by the lower classes. The 
seeds, which are very buoyant, contain a kernel that does not 
float, the buoyancy being due to the water-tight coats which, as 
shown in the plate in Chapter XII., possess well developed air- 
bearing tissues. It may here be observed that Martins refers to 
the germination of seeds of Cucurbita pepo after 45 and 93 days' 
flotation in sea-water. 

One sometimes finds buoyant tissue developed in the seeds of 
bottle-gourds, where it can serve no useful purpose of dispersal. 
Thus small bottle-gourds, seemingly of the genus Cucurbita rather 
than of Lagenaria, are to be commonly found afloat in the Guay- 
aquil River and stranded on the Ecuador beaches. They will float 
for many months, and contain the seeds dried up into a small loose 
compacted mass in their interior. These seeds, which contain a 
layer of spongy air-bearing tissue in their coverings, will in several 
cases float for months. Some that I had been keeping two months 
afloat in sea-water germinated freely. It is shown in Note 47 that 
bottle-gourds containing sound seeds are dispersed far and wide by 
the currents. In some species the seeds are buoyant, and in others 
they sink in sea-water ; but the gourds themselves will float for 
probably a year or more, and the floating capacity of the seeds 
when it exists is too insignificant to affect the fruit's buoyancy. 

Other instances of the useless buoyancy of fruits of inland 
plants are afforded by different species of Citrus. In the floating 
drift of the Fijian rivers the fruits of the wild and indigenous 
Shaddock (C. decumana) and of an inedible Orange, also wild and 
indigenous (C. vulgaris?), are at certain times to be found, the 
latter often in numbers. The first-named floats four to five weeks 
in sea-water, and the last-named nearly two months, and both are 
to be observed floating out at sea between the islands. The fruits 
of the Tahitian Orange, a variety of C. aurantium, floated in sea- 
water between three and four weeks. The seeds of these and 
other species of Citrus sank in from a few hours to a day or two. 
The buoyancy of the fruit depends on the rind the thicker the 
rind the greater the floating power. This was not only shown in 
the length of the period of flotation, but also in the buoyant 
behaviour of the fruit. With the Tahitian Orange, where the rind 
is relatively thin, the fruits floated heavily in sea-water and only 
protruded slightly above the surface. With the Shaddock and 



126 A NATURALIST IN THE PACIFIC CHAP. 

with the other indigenous species of Citrus, the fruits floated lightly 
and protruded half-way out of the water. 

There is nothing trivial in these examples of buoyant fruits. 
That they have at times aided in the dispersal of the genus, with 
man's assistance in planting the seeds of the stranded fruits, I 
cannot doubt ; but unaided by man such buoyant capacities would 
be useless for purposes of effective dispersal by currents. Between 
the two genera Terminalia and Citrus there is this great distinction, 
that the former is more or less halophilous, some of its species 
being at home on the sea-beaches, whilst the latter, as Schimper 
would term it, is salt-shy, and includes no halophytes or plants of 
the sea-shore amongst its species. The only effect of buoyancy of 
the fruits on the distribution of the species of Citrus would be to 
place them by the side of the river and the pond. This has 
evidently been its result in the case of the Shaddock in Fiji, where, 
as Seemann remarks, it often thickly lines the banks of the rivers. 

As also indicating that the buoyancy of the seed or fruit would 
never, apart from the halophilous habit, endow an inland plant 
with a littoral station, the examples of the Oak (Quercus robur) 
and of the Hazel (Corylus avellana) may be taken. As shown in 
Note 48, these fruits acquire floating power by drying, on account 
of the space formed by the shrinking of the kernel. They occur 
commonly in beach drift, but rarely in a sound condition ; yet 
experiment has proved that they will sometimes germinate after 
prolonged sea-water flotation. The fruits of other species of 
Quercus are also transported in tropical regions by the currents, 
but never, as far as I could learn, effectively. The Amentaceae as 
an order are " salt-shy," and with only a few exceptions shun the 
sea-beach. 

In the great sorting-process, by which xerophytic plants with 
buoyant seeds or fruits have been placed at the coast, and hygro- 
phytic plants with similar fruits or seeds have been stationed at 
the riverside or by ponds and lakes, one might expect to find 
that other influences may have at times been in conflict with the 
selecting operation here indicated. To this cause may probably 
be attributed the cases of " useless buoyancy " above referred to. 
Here we find in some inland plants fruits and seeds with buoyant 
tissues in their coverings that in the case of littoral plants would 
have been regarded as the result of adaptation to dispersal by 
currents. Such cases go to emphasize the conclusion already 
indicated that these tissues could not have been developed through 
the agency of Natural Selection. But the great objection against 



xin ADAPTATION AND SEED-BUOYANCY 127 

the application of the Darwinian view to the general subject of the 
buoyancy of the seeds and fruits of littoral plants lies in the cir- 
cumstance that quite half of the plants concerned are admitted to 
be outside the scope of the theory, and that for these another 
explanation has to be found. I think we may fairly claim that in 
a matter which finally resolves itself into a question of buoyancy 
one explanation should cover all. We have thus to decide whether 
to regard as adaptations to dispersal by currents the structures of 
the buoyant seeds and fruits of littoral plants ; or whether to hold 
the view that as far as dispersal by currents is concerned such 
structures are purely accidental, and that Nature has never directly 
concerned herself in the matter at all. The first explanation lies 
under the disadvantage above alluded to, and it remains to be 
learned whether the second view could be made to cover all cases 
of dispersal by currents. Further investigation on many points 
is yet required ; but, apart from the evidence against Natural 
Selection as the principal agency that has been produced in this 
chapter, a powerful argument in favour of the view that the 
buoyancy of seeds and fruits is not concerned with adaptation 
is, that as a rule the floating capacity of the seed or fruit has 
no direct relation with the density of sea-water. Generally 
speaking, as shown in Chapter X., these seeds and fruits are 
much more buoyant than they need to be, that is to say, if 
they owe their floating power to adaptation to dispersal by 
currents. This is quite in accordance with the argument deve- 
loped in Chapter XL with regard to the general question of 
plant-distribution, that dispersing agencies make use of characters 
and capacities of seeds and fruits that were never intended for 
them. 



Summary of the Chapter. 

(1) There are many mechanisms or contrivances in plants 
that now serve a purpose for which they were not originally 
developed. 

(2) Of this nature, it is contended, is the relation between fruits 
and seeds and the agencies of dispersal. 

(3) If, however, the structure or mechanism is made more 
effective by the new function, such a modification may be regarded 
as an " adaptation " in the language of the theory of Natural 
Selection. 



128 A NATURALIST IN THE PACIFIC CHAP. 

(4) It is held by Professor Schimper that the structures con- 
nected with the buoyancy of the fruits or seeds of several tropical 
littoral plants are, in the above sense, adaptations ; and he points 
to several genera where the buoyant tissues in the coverings of the 
fruits or seeds of the coast species are scantily represented or 
absent in the inland species of the same genus, a difference 
corresponding with the loss or diminution of the floating powers. 

(5) This contrast in structure and in floating capacity between 
the fruits or seeds of inland and coast species of the same genus is 
beyond dispute, and the author adduces fresh data in support 
of it. 

(6) But he contends that it is not proved that the relatively 
great development of buoyant tissues in the case of littoral plants is 
the effect of adaptation ; and that if the selecting process had been 
confined to sorting out the xerophilous plants with buoyant seeds 
or fruits and to placing them at the coast, the same contrast 
would have been produced. 

(7) In support of this contention he points out that when such 
littoral plants extend inland the floating capacity and the buoyant 
tissues are as a rule retained ; and that in those exceptional cases 
where inland plants possess buoyant fruits or seeds these tissues 
are sometimes well developed under conditions in which they could 
never aid the plant's dispersal. 

(8) But the most serious objection against the adaptation 
view is that admittedly only about half of the shore-plants with 
buoyant fruits or seeds come within its scope. Therefore a 
second explanation has to be framed for the other plants 
concerned. 

(9) As showing the difficulties raised by regarding some of the 
structures connected with buoyancy as " adaptive " and others as 
"accidental," it is pointed out that some fruits possess the two 
kinds of structure. It is also shown that in several cases fruits 
endowed with buoyant tissues are just as well adapted for 
dispersal by frugivorous birds ; and the instance of Ximenia 
americana is cited where a drupaceous fruit, known to be dispersed 
by fruit-pigeons, possesses also in its " stone " both the " adaptive " 
and " non-adaptive " types of " buoyant structures." 

(10) It is urged that whatever is the relation between the 
buoyancy of the seeds and fruits of shore-plants and dispersal by 
currents, there has been a uniform principle affecting all. 

(11) The weight of evidence is regarded as adverse to the 
Natural Selection theory, an inference which is consistent with the 



xin ADAPTATION AND SEED-BUOYANCY 129 

conclusion arrived at in Chapter X. that there is no direct relation 
between the density of sea-water and the buoyancy of seeds and 
fruits, the floating capacities being as a rule far greater than the 
adaptation view would explain. Nature, it is held, has never 
made any provision for dispersal by currents, the buoyancy of 
seeds and fruits being, as concerns the currents, a purely accidental 
quality. 



VOL. II K 



CHAPTER XIV 

THE RELATION BETWEEN LITTORAL AND INLAND PLANTS 

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. 
Scaevola. Morinda. Calophyllum. Colubrina. Tacca. Vigna. 
Premna. 

IN discussing the relation between the littoral and inland floras in 
the Pacific it will be at first necessary to pick up some of the 
threads of the various lines of investigation dealt with in the 
previous portion of this work. Apart from considerations con- 
nected with the genetic history of the plants concerned, when 
we come to inquire into the sources of any individual strand-flora, 
whether in the temperate or in the tropical regions, we arrive 
at the rough and ready inference that it is composed of " what the 
sea sends and the land lends." But it has been already shown 
that the relative proportion of the current-borne and in con- 
sequence widely dispersed plants in a strand-flora varies greatly 
in different regions. Thus in the Pacific islands, as typified by 
those of Fiji, about 90 per cent, have buoyant seeds or seed- 
vessels originally brought from distant localities ; and in the 
tropics, as a rule, the average would probably be never under 
75 per cent. On the other hand, in a temperate region the plants 
derived from inland would be most predominant, making up 
probably some three-fourths of the whole, whilst the proportion of 
current-dispersed plants hailing from distant places would be 
relatively few. 

It is on this account that there is such uniformity in the 
general composition of the strand-flora over a large part of the 
tropics, since current-dispersed plants are widely spread. But in 
the temperate regions we find a great contrast in this respect. 



CH.XIV LITTORAL AND INLAND PLANTS' RELATIONSHIP 131 

There are, it is true, a few current-borne plants that one meets 
everywhere. For instance, Convolvulus soldanella is to be 
gathered on English beaches and on those of New Zealand and 
of the coast of Chile. But these littoral plants with buoyant 
fruits hardly give a feature to the strand-flora. A multitude 
of intruders, either characteristic of the inland flora of the region 
or confined only to the seaboard of that part of the world, 
also make their home on the beach and frequently endow a 
beach-flora with its leading features. The possible associations of 
plants on a beach in a temperate region are thus very great ; and 
I have already discussed this in part in Chapter IV. as concerning 
the British shore-flora. One has only to look at a work like that 
of Dr. Willkomm on the vegetation of the strand and steppe- 
regions of the Iberian peninsula to realise how the few littoral 
plants familiar to the English eye cut but a sorry figure amongst 
the numbers of strange intruders from the arid regions inland. 
So again, as I found on the Chilian beaches, Convolvulus 
soldanella finds odd associates amongst the species of Nolana 
and Franseria that are peculiar to the coasts of that part of the 
globe (see Chapter XXXII.) ; and different grotesque American 
forms of the Cactaceae with a Mesembryanthemum and a host of 
strange-looking plants descend from the arid slopes of the hills 
behind to keep company with the far-travelled English beach- 
plant (see Note 49). Or again, a glance at the pages of Professor 
Schimper's great work on Plant- Geography will bring the same fact 
home in a still more varied fashion. 

Yet on tropical coasts the intruding inland element is also 
distinguishable, though it may influence only to a small degree the 
general character of the strand-flora. Dividing it, as we have 
described in Chapter V., into the plants of the sandy beach and of 
the mangrove-swamp, we find in the mangroves the most stable 
element and in the beach-plants those most liable to change. 
Professor Schimper observes that whilst the physiognomy of the 
beach-flora varies to some extent with the alterations in the inland 
flora, the mangrove-formation makes but a slow response to such 
changes. As he points out in his work on the Indo-Malayan 
Strand-Flora (p. 199), seeds and seed vessels are being continually 
brought down to the sea-coast through the agencies of rivers, 
winds, and birds ; and in this manner, in the course of ages, the 
beach-flora is recruited from the inland plants. But for the 
mangroves such additions to their numbers are rarely possible. 
Whilst the same genera are often shared by both the beach 

K 2 



1 32 A NATURALIST IN THE PACIFIC CHAP. 

and inland floras, we have in the mangrove-formation families, 
sub-families, and genera almost peculiar to itself, and including 
plants, like those of the Rhizophoreae, that in their characters 
betray but little kinship with others and give but little indication 
of their descent. The mangroves have remained through the ages 
as something apart from other coast-plants, isolated both in their 
history and in their characters, and especially distinguished by 
their " adaptations " to their surroundings. 

Such is the line of argument followed by this eminent German 
botanist in his account of the development of a tropical strand- 
flora. In various parts of this work I have ventured to suggest 
that the mangroves may be the remnant of an ancient flora widely 
distributed over the lower levels and coastal regions of the globe 
in an age when vivipary (meaning, thereby, germination on the 
plant) was the rule rather than the exception. At such a period, 
as I imagine, the climatic conditions of the earth were much more 
uniform than they are at present, at least in the lower levels ; and a 
warm atmosphere, charged with aqueous vapour and heavy with 
mist and cloud, enveloped a large portion of the globe. The 
mangroves, it may be remarked, are by no means universally 
distributed on tropical coasts in our own time. (Professor 
Schimper describes their distribution in his Indo-malayische 
Strand-Flora, pp. 85, 86, and in the English edition of his 
Plant-Geography^ p. 409.) They are not found on rainless coasts 
even when under the Line, except where there happen to be large 
estuaries ; but where a rank and luxuriant inland flora betokens a 
high degree of humidity, there they thrive. This is well illustrated 
on the rainless shores of tropical Peru, a locality described in 
Chapter XXXII. of this work. 

Yet if, as it is here contended, the mangroves form a remnant 
of a once widely spread viviparous flora, it might be expected that 
the beach-plants of that age would have been also viviparous, and 
that with their present descendants, as well as with some of the 
inland plants allied to them, we ought to find in the anomalous 
structure of the seed some indication of the lost viviparous habit. 
This appears to be the case, as described in Note 50, with the 
Barringtoniae, a tribe that has supplied some of the most 
characteristic beach-trees, and also with some genera of the 
Guttiferse. Perhaps, indeed, when the seeds of several other 
littoral beach-trees come to be examined, for instance, Guettarda, 
analogous structures may be found. 

Although the beach-flora of the tropics is less stable in its 



xiv LITTORAL AND INLAND PLANTS' RELATIONSHIP 133 

composition than the mangrove-formation, it is not to be assumed 

that in the Pacific region or in the tropics generally it is at all 

modern in its character. Though in the main, no doubt, more 

recent than the mangroves, since it is likely that in early 

geological periods the swamp rather than the sandy beach formed 

the predominant feature of the sea-border throughout the tropics, 

yet it bears in several respects the impress of a high antiquity. 

There are few beach plants in the tropical Pacific that are not 

found over the tropics of a large portion of the globe, a 

circumstance that would in itself warrant our assigning a great age 

to the beach-flora ; and it is highly probable that some at least of 

the beach plants of the Pacific that occur on the east and west 

coasts of tropical America are, for reasons given in Chapter XXXII., 

older than the barrier now interposed by Central America between the 

Atlantic and Pacific oceans. There are, it is true, a few species, 

like Acacia laurifolia and DrymispermumlBurnettianum, which, on 

account of their restriction to the beaches of the Western Pacific 

and their lack of capacity for dispersal by currents, may be 

regarded as local productions ; but for the great majority, ranging 

as they do over much of the tropics, it is not possible to determine 

when and where they assumed their littoral habits. That except 

in a few instances their home in some bygone age lay outside the 

Pacific can scarcely be doubted. 

It is therefore to be expected that in a discussion of the relation 
between the strand and inland floras in the Pacific islands the 
problem will be mainly concerned with the possible derivation of 
inland from littoral plants. In such a discussion the relation 
between the beach and inland species of the same genus becomes a 
subject of great interest. It is a subject that had a peculiar 
fascination for Professor Schimper, who refers to it more than once 
in his pages ; and though never able to take it up, he viewed it 
as a very promising field of inquiry. The question has been 
frequently alluded to in this work ; and it is especially dealt with 
in one connection in Chapter 1 1. It is there shown that whilst, as 
a general rule, the seeds or seedvessels of the coast species possess 
great floating power, those of the inland species of the same genus 
have little or none, and that both may have independent modes of 
dispersal, the first by currents, and the last through frugivorous birds. 
A close connection between the beach and inland floras is 
apparently displayed in the circumstance that quite a third of the 
genera of the Pacific insular floras containing littoral species (some 
70 in all, excluding the mangroves) possess in this region also 



i 3 4 A NATURALIST IN THE PACIFIC CHAR 

inland species. But the further examination of this interesting 
group of genera, which are enumerated in the list below, goes to 
show that the connection between the inland and coast species of a 
genus is by no means always so close, or of such a character, as 
one might have expected. It will not be possible, however, to do 
much more than indicate in this chapter the results of this 
inquiry ; but the details will usually be found either in the separate 
discussion of the genus or in other parts of this work. For 
convenience of treatment these genera may be grouped in the 
following sections. 

Grouping of the Plant-Genera of the Islands of the Tropical 
Pacific that possess both Littoral and Inland Species. 

Section I. Where the littoral and inland species are most 
probably of independent origin, both possessing their own means 
of dispersal ; Calophyllum, Hibiscus, Colubrina, Morinda, Scaevola, 
Cordia, Ipomea, Vitex, Tacca, Casuarina. 

Section II. Where the littoral species have probably given 
rise to inland species, and both still exist in the group of islands : 
Vigna, Premna. 

Section III. Where inland species have been probably 
developed from littoral species no longer existing in the group : 
Canavalia, Erythrina, Sophora, Ochrosia. 

Section IV. Where the littoral and inland species are 
evidently of independent origin, and there is no means of 
accounting for the existence of the inland species by agencies of 
dispersal at present in operation : Barringtonia, Pandanus. 

Section V. Where in the same genus some inland species are 
derivatives of the coast species and others are of independent 
origin : Guettarda. 

Section VI. Where the coast species, having little or no 
capacity for dispersal by currents, are regarded as derived from 
the inland species in one group of islands and as afterwards 
distributed to those in the vicinity : Eugenia, Drymispermum,. 
Acacia. 

SECTION I 

This group, which includes those genera where the coast and 
inland species are regarded as of independent origin, both possess- 
ing their own means of dispersal, contains about half of the total 



xiv LITTORAL AND INLAND PLANTS' RELATIONSHIP 135 

number of genera here concerned. We will first deal with the 
genera Calophyllum, Morinda, and Scaevola, where the littoral 
species have buoyant fruits or seeds that are dispersed by currents, 
whilst the inland species have more or less non-buoyant fleshy 
fruits that could only be dispersed by frugivorous birds. Here the 
inland and coast species could have arrived independently at the 
island, and we are not called upon either on this ground or by 
reason of affinity of characters to connect the one with the 
other. 

The genus Scaevola is very typical of its kind and has been 
already in part discussed in Chapter II. The wide-ranging shore- 
species, S. Kcenigii, that is distributed over the Pacific may some- 
times, as in Hawaii, be accompanied by numerous inland species, 
all endemic, seven of them being enumerated by Hillebrand ; or, 
as in Fiji and Tonga, there may be associated with it a solitary 
inland species, S. floribunda (see Note 51) ; or, as in Tahiti, it may 
exist by itself. On the other hand, as in the Kermadec Islands, 
a single inland peculiar species may alone represent the genus. 
The inland species have fleshy drupes which, as far as examined, 
have no floating power and possess no buoyant tissues in their 
coverings ; and their independent dispersal by birds cannot be 
doubted. The endemic character of most of the inland species of 
the Pacific islands is most probably due to the suspension of the 
transporting agency of frugivorous birds, just as the wide range 
of the solitary littoral species may be attributed to the uninter- 
rupted agency of the currents. There is nothing in the description 
of the endemic species given in Hillebrand's Hawaiian Flora 
to indicate any especial genetic connection between the inland 
species and the beach plant, S. Kcenigii; and the occurrence of 
a solitary inland peculiar species in the Kermadec Islands clearly 
proves an origin independent of any littoral plant. 

Morinda is another critical genus in this discussion. Besides 
the widespread littoral species (M. citrifolia) that is distributed by 
the currents and is also dispersed by man, there are in the Pacific 
islands a number of inland species, mostly climbers and denizens of 
the forests. In the Index Kewensis six are accredited to Fiji and five 
to New Caledonia. Hillebrand gives a peculiar Hawaiian species, 
and there is a widespread species (M. Forsteri) that ranges over 
the South Pacific from New Caledonia to the Marquesas and the 
Paumotu Islands. Since, as indicated in Chapter II. and in Note 8, 
the pyrenes of the fruits of the inland species are not dispersed by 
the currents and could readily be transported by frugivorous birds, 



136 A NATURALIST IN THE PACIFIC CHAP. 

we are not called upon to connect them in their origin with 
M. citrifolia, the wide-ranging species of tropical beaches. 

The fact of the dispersal of certain inland species of the genus 
over large areas of the tropics, such as in the case of Morinda 
umbellata through tropical Asia and Malaya, and M. Forsteri in 
the Pacific, is indeed sufficient proof that these inland plants are 
independent of any littoral species in the Pacific and possess their 
own means of distribution. Though the genus, comprising at least 
forty species, is mainly confined to the Old World, there are a few 
species in America ; but M. citrifolia, the familiar beach species 
of the Old World and the Pacific, is not indigenous there, and, as 
far as I can gather, all the American species belong inland. Facts 
of distribution of this nature negative the possibility that the 
Pacific islands have received their inland species of Morinda 
through the intervention of the far-ranging littoral plant. 

As respecting Calophyllum, which is represented all over the 
tropical South Pacific by the wide-ranging C. inophyllum and by 
a tree of the inland forests found also in Malaya and in Ceylon 
(C. spectabile), there are, apart from questions of affinity, grave 
objections against the derivation of the same inland species from 
the coast species all over this area. The fruits of the two inland 
species of Fiji, C. spectabile and C. burmanni, have sappy outer 
coverings and are quite suited for dispersal by fruit-pigeons. As 
observed in Chapter II. and Note 9, they have limited floating 
capacities and their dispersal by birds is necessary to explain their 
distribution. Since the timber is greatly valued by the Polynesians, 
it is not unlikely, however, that those islanders have assisted in the 
distribution of the inland species. It is not possible to do more 
than touch on this subject here ; but it may be inferred that the 
history of Calophyllum in the Pacific has not been one that would 
warrant our regarding the inland trees as derivatives of a coast 
species. 

There are other genera of this section where, for reasons of a 
different character, there is no cause for assuming that the inland 
species are derived from the coast species, or vice versa. Thus, in 
Fiji, Casuarina equisetifolia, a widely distributed species of the 
Old World, occurs at the coast and in the scantily wooded plains 
behind ; while C. nodiflora, a New Caledonian species, finds its 
home in the lower forests. There are many endemic species in 
Australia and New Caledonia ; and we are not called on to con- 
nect together these two species in Fiji. In the same way we are 
not under any obligation in the case of the numerous inland species 



xiv LITTORAL AND INLAND PLANTS' RELATIONSHIP 137 

of Ipomea of the Pacific islands to connect them with the coast 
species. They are all widely ranging species, and their seeds have 
been carried to the islands, each in its own fashion. So again with 
the inland species of Hibiscus found in the Polynesian islands and 
often cultivated, we cannot either from the point of view of 
dispersal or of affinity connect them with the far-ranging littoral 
species, H. tiliaceus, which belongs to a section of the genus 
distinct from those sections to which the inland species belong. 

In a similar way there is no ground for supposing that Cordia 
aspera, an inland species confined to Fiji, Tonga, and Samoa, is 
derived from C. subcordata, the widely distributed littoral species 
of the Pacific and of the Old World, since they belong to different 
sections of the genus. But, apart from any question of affinity, 
the drupes of inland species of Cordia are known to be well suited 
for dispersal by frugivorous birds, though, unlike the littoral species 
above named, not adapted for transportal by the currents. The 
genus Vitex, which is represented by a wide-ranging littoral species 
in the Pacific (V. trifolia), appears to be associated with inland 
species only in Fiji, where one or two, seemingly endemic, occur, 
But there is nothing in Dr. Seemann's description ofV. vitiensis, one 
of these species, that at all suggests its derivation from the strand 
species, a very variable plant that often extends far inland into the 
plains, adopting a different habit of growth in those localities. It 
is known that Vitex fruits can be dispersed both by birds and by 
currents. This genus is more fully discussed in a later chapter. 

Of the genus Colubrina there seem to be only two Pacific 
species known one the widely distributed shore-plant, C. asiatica, 
a straggling shrub with 'alternate leaves found in all the Pacific 
groups and on the beaches of much of the tropics of the Old 
World ; the other a tree, C. oppositifolia, with opposite leaves, that 
is peculiar to the Hawaiian islands, where it frequents the open- 
wooded and scrubby inland districts. The seeds of the shore- 
plant float unharmed for many months, whilst the fruits of the 
inland plant, which differ in some important respects (see Note 52), 
would float only for a week or two. The strand species is also quite 
at home inland in many parts of the world ; and there is nothing 
from the standpoint of affinity to indicate that in Hawaii it has 
given birth to an inland species so divergent in habit and in 
character. There is of course the difficulty of explaining how a 
plant like C. oppositifolia, with such a dry, unattractive fruit, could 
be indebted to birds for its original introduction into the group ; 
but the same difficulty arises with a host of Hawaiian plants. It 



138 A NATURALIST IN THE PACIFIC CHAP. 

is, however, evident from its distribution over the islands of this 
archipelago that it possesses or has possessed some means of 
inter-island dispersal, and since it is not of much service to the 
aborigines we must look therefore to the bird. 

In the instance of the genus Tacca there is in Fiji an inland 
species, T. maculata, associated with a wide-ranging beach species, 
T. pinnatifida, which also grows inland. The first-named is 
recorded from the north coast of Australia and from Samoa, and 
though, unlike the beach plant, its seeds are unfitted for dispersal by 
currents (see Chapter II.), they might be distributed by birds. Dr. 
Reinecke describes another inland species from Samoa, T. samoensis. 
The beach plant, T. pinnatifida, grows so typically (sometimes side 
by side with T. maculata) in the inland plains of Fiji that one 
would not be justified, apart from questions of affinity, in regarding 
it as the parent form of inland species in the Pacific islands. 

For food and other purposes Tacca pinnatifida is or was much 
valued by the Pacific islanders, and it grows so abundantly that 
cultivation is rarely practised. That the Polynesians have aided 
,the currents in the distribution of the plant there can be no doubt, 
and this is particularly indicated by its occurrence in Hawaii. The 
genus contains ten or a dozen species, of which at least three are 
peculiar to America ; but T. pinnatifida, the characteristic shore- 
plant of the Old World, and according to Schimper the only one 
that can be so designated, is not found in America, where, as far as 
I can gather, there is no widely-spread beach species dispersed by 
the currents from which the peculiar species could have been 
derived. In the case of the Pacific species, however, it should be 
noted that I am not endeavouring to prove the improbability of the 
inland species having been derived from the coast species in other 
regions, as in Australia, but that my point is to show there is 
no reason to suppose that this has taken place in the Pacific. 
There is no difficulty in attributing the dispersal of inland species 
to birds ; and we are therefore not called on to connect them with 
the beach plants. 

SECTION II 

This division includes those genera where the littoral species 
has apparently given rise to one or more inland species and both 
still exist in the same group of islands. Two genera alone, Vigna 
and Premna, come into this category. The first-named seems to 
present a good case for the derivation of an inland from a coast 



xiv LITTORAL AND INLAND PLANTS' RELATIONSHIP 139 

species in Hawaii. Besides Vigna lutea, the beach species, which 
is found not only all over the Pacific islands but on the tropical 
beaches of the Old World, there are in Hawaii two endemic species 
(V. sandwicensis and V. oahuensis) that occur in the mountains, 
usually at elevations of from 1,500 to 5,000 feet ; but I do not find 
any more inland species recorded from the other Polynesian 
archipelagoes. It may at first be noted that Vigna lutea, which in 
some parts of the world strays inland, displays considerable variety 
in its littoral station in the Pacific. Thus, in Hawaii, I found it 
sometimes on the sandy beach, sometimes on a rocky shore, and 
sometimes on the edge of old lava-cliffs overlooking the sea. In 
Fiji, though usually a trailer on the beach, it may become a climber 
hanging from the trees bordering the creeks in the mangrove- 
swamps. Though Hillebrand makes no mention of forms inter- 
mediate between coast and inland species in Hawaii, I found in one 
locality at the coast some specimens of Vigna lutea displaying the 
twisted pods and two callosities on the standard that are charac- 
teristic of V. sandwicensis, one of the inland species. The seeds 
of Vigna lutea float in sea-water unharmed for months, and they 
are to be found in the stranded drift of the Hawaiian and Fijian 
beaches, and floating in the drift of the Fijian rivers. I was unable 
to obtain the mature seeds of the inland species, and it has there- 
fore yet to be determined whether they follow the rule in the loss 
of buoyancy. It may be added that a plant of Vigna lutea 
raised in Hawaii from seed displayed some small tubers of the size 
of a pea on its roots. 

The case for Premna is stated in Note 32. In this genus, as 
with Vigna, the final test of experiment is needed ; but the data at 
my disposal point to the probability that an inland species has 
here been derived from a littoral plant. 

The summary of this chapter is given at the end of Chapter 
XVI. 



CHAPTER XV 

THE RELATION BETWEEN LITTORAL AND INLAND PLANTS 

(continued) 

Inland species of a genus developed trom 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. 

SECTION III 

HERE we have three genera of the Leguminosae, namely, 
Erythrina, Canavalia, and Sophora, and one Apocynaceous genus, 
Ochrosia, in which it is considered that inland species have been 
probably developed from littoral species no longer found in the 
group. In this case the shore species, possessing buoyant seeds or 
fruits that are known to be dispersed by the currents, is absent 
from the particular group in which the inland species occurs ; and 
since the last-named displays no capacity for distribution by 
currents, or seemingly by birds, we are driven to infer that it was 
originally derived from a coast species, brought by the currents, that 
has since disappeared. 

Hawaii is the only region concerned here ; and these four 
genera may be said to well illustrate the particular " Hawaiian 
difficulty." If this explanation of the origin of the inland species 
is legitimate, then it offers us a mode of explaining still more 
perplexing cases in the Hawaiian flora, such as those relating to 
the endemic species of Mezoneuron (Leguminosae) and to Hille- 
brand's Vallesia (Apocynaceae), where there is apparently no 
littoral species known from any region. 

Dealing with the three Leguminous genera, it is at first to be 
remarked that the great floating powers of the seeds of the littoral 
species are in all three cases to be attributed to the buoyant 



CH. xv LITTORAL AND INLAND PLANTS' RELATIONSHIP 141 

kernel ; whilst on account of the non-buoyancy of the kernel the 
seeds of all the inland species possess no floating power. Some 
very interesting points are raised in each of the three genera, and I 
will first deal with the genus Erythrina. 



ERYTHRINA. 

If we look over the Pacific islands in search of a critical locality 
for the investigation of the genetic relation between the littoral 
and coast species of Erythrina, we discover it, as far as I can gather, 
only in one group. In Fiji, Tonga, and Samoa we find only the 
littoral species ; in Hawaii there is only an inland species ; whilst 
in Tahiti occur both the littoral and the inland species E. indica,. 
the wide-ranging shore-tree of the South Pacific, and E. mono- 
sperma, the inland tree of Hawaii the last found nowhere else in 
Polynesia, and confined to the Pacific. In Tahiti there are no 
other species, and it is between these two species that the connec- 
tion, if it exists, is to be sought. (Further details relating to the 
genus are given in Note 53. In this place only the facts bearing 
on the argument will be discussed.) 

The buoyant seeds of Erythrina indica are well known to be 
dispersed by the currents ; whilst those of E. monosperma, as 
obtained from Hawaii, have no floating power and sink at once, or 
in a day or so, even after drying for two years. In Tahiti the first- 
named species is a characteristic plant of the beach, whilst the last 
grows there in the valleys and on the mountains up to elevations 
of 700 to 800 metres. We have now to inquire whether there is 
any decided affinity between the two species, and whether the 
divergent characters of the inland species can be connected with 
its station. With regard to the first query we may quote in reply 
the observation of Drake del Castillo, that as concerning the foliage 
and the inflorescence E. monosperma is very nearly related to- 
E. indica, differing only from it in the more hairy calyx, in the 
more permanently tomentose and much shorter pod, and in the 
paucity of seeds (one or two in number). 

We will now see whether it is possible to connect these 
differences in character with differences of station. Neither 
Nadeaud nor Drake del Castillo give precise descriptions of 
the station of Erythrina monosperma in Tahiti ; but Nadeaud and 
Lepine remark that it grows on precipices as well as in the valleys 
on the north or dry side of the island ; and we may infer that it 



i 4 2 A NATURALIST IN THE PACIFIC CHAP. 

affects exposed dry rocky stations. In Hawaii, according to 
Hillebrand, it is found on the dry rocky hills and plains of all the 
islands up to 1,000 feet. I was particularly interested in this tree 
whilst in the group, and found it in the large islands of Maui and 
Hawaii thriving in rocky arid districts of little rainfall, accom- 
panied by Cactus opuntia, Ricinus communis, and Caesalpinia 
bonducella. It is often to be observed on scantily vegetated lava- 
flows, a solitary tree growing here and there out of a crack in the 
old lava, or it may dot the rocky slopes of some barren declivity. 
I found it in the dry gulches behind Lahaina at elevations of 800 
to 1,200 feet above the sea, growing amongst huge blocks of 
stone in clumps of ten or twelve trees. When one contrasts the 
inland station of E. monosperma with that of E. indica on the beach 
where the atmosphere is more humid and the conditions more 
suited for plant-growth, it appears probable that the differences 
between these two species may be largely connected with station, 
especially as regards hairiness and the diminished size of the pods. 
Assuming, therefore, that Erythrina monosperma is but the 
inland form of E. indica and that the differences between the two 
species are mainly an affair of station, we have next to account for 
the occurrence of the inland species in Hawaii without the littoral 
species. The agency of currents in explanation of the existence of 
E. monosperma in Hawaii is at once excluded, since the pods 
dehisce on the tree, and the seeds, as already remarked, have no 
floating power. Nor does it seem likely that beans half an inch 
(13 mm.) long could be transported unharmed in a bird's stomach 
over the two thousand miles of sea that intervene between Tahiti 
and Hawaii. Yet one cannot doubt that the pyrenes and 
" stones " of genera like Coprosma, Nertera, Cyathodes, and 
Osteomeles have been carried by frugivorous birds to Hawaii. 
But a bean is somewhat different from the crustaceous pyrene of 
Coprosma or the hard " stone " of Cyathodes ; and although, as 
indicated by the occurrence of an endemic species of Erythrina in 
Fernando Noronha, birds may carry large beans unharmed over a 
couple of hundred miles of sea, one hesitates to conclude that they 
could effect this when the tract of ocean to be traversed is ten 
times as great. There are again reasons for believing that the 
seeds of Erythrina monosperma are particularly ill-suited for 
dispersal by birds, since, notwithstanding their hardness, they soon 
absorb water through the micropylar opening ; and they germi- 
nated so readily in my experiments that the digestive juices in a 
bird's stomach would probably soon find access and destroy the 



xv LITTORAL AND INLAND PLANTS' RELATIONSHIP 143 

kernel. It is, however, known from the observations of the 
Messrs. Layard in New Caledonia that a small crow and different 
species of parrots feed on the seeds of Erythrina, and they may 
aid in the local dispersal (Ibis, vol. 6, 1882). 

To admit man's agency in carrying to Hawaii the seeds of a 
tree which is only useful in supplying him with light wood for his 
outriggers and his fishing-net floats would compel us to place in 
the same category a great number of plants in some way useful 
to him which are recognised as indigenous. The Polynesian 
ransacks the vegetable world for his wants, and carries with him 
in his migrations only his food-plants and the seeds of his sacred 
trees. 

There remains then the possibility that the parent species, 
Erythrina indica, was once in Hawaii but has since disappeared. 
In order to establish this, it will be requisite to show not only 
that the extinction of a shore-plant is probable, but also to 
explain why the new species has selected such arid inland 
localities for its stations, to account for the loss of buoyancy of the 
seeds, and, if possible, to give an instance of the production of a 
new species of Erythrina in a small isolated oceanic island. 

A study of the special circumstances of Hawaii leads one to 
conclude that a shore-tree may become extinct in one of two ways. 
It may be exterminated by insect pests, or it may be forced inland 
through unsuitable coast-conditions and there be lost in the 
resulting new species. One characteristic shore-tree, Cordia 
subcordata, has indeed been almost exterminated by insects, 
and even Erythrina monosperma is now from the same cause 
on its road to extinction (see Note 53) ; but there is no 
indication of their leaving modified descendants behind that 
are pest-proof. The most probable view then is that the littoral 
tree, having been driven inland through the unsuitability of the 
coast-conditions, such as lack of beaches or want of moisture, has 
there become modified. This is what has really happened, as I 
have shown, with Caesalpinia bonducella in Hawaii. As indicated 
in Chapter XVIL, this characteristic beach-plant has here been 
driven off the beach. There would thus be no difficulty in 
assigning a reason why a littoral tree like Erythrina indica 
should select arid localities when it extends inland, since, as is 
pointed out in Chapter IV. and in other parts of this work, the 
plants of the beach and of the arid inland district possess the same 
xerophilous habit. 

With regard to the loss of buoyancy of the seeds in the case of 



144 A NATURALIST IN THE PACIFIC CHAP, 

Erythrina monosperma, it may be remarked that this is precisely 
what has happened with the seeds of Caesalpinia bonducella, its 
usual associate on the old lava-wastes in Hawaii, and with an 
inland species of Csesalpinia in Fiji. It is argued that the same 
thing has occurred with the inland Hawaiian species of Canavalia 
and Sophora, as shown in later pages of this chapter. It has. 
certainly happened with the inland form of Afzelia bijuga in Fiji, 
a tree dealt with in Chapter XVII. These are all Leguminous 
genera ; and in all of them, with the exception of Csesalpinia, 
where the floating power arises from a central cavity in the seed, 
the seeds of the littoral species possess, like Erythrina indica, 
buoyant kernels. Whilst most littoral plants with buoyant seeds 
or fruits retain the floating capacity of the seed or fruit when 
they extend inland, the Leguminosae often offer exceptions to the 
rule. 

That inland endemic species of Erythrina can be developed 
in isolated islands is illustrated by the existence in Fernando 
Noronha, some two hundred miles from the coast of Brazil, of a 
peculiar species, E. aurantiaca, described by Mr. Ridley. Here 
also is found an inland species of Guettarda peculiar to the locality ; 
but in neither genus does the littoral species occur. 

Many difficulties will yet have to be explained before it can be 
finally established that Erythrina monosperma has been derived 
from E. indica or some similar shore species that was originally 
dispersed by the currents ; but we are almost driven towards such 
a view, since it is hard to believe that the beans were carried to 
Hawaii by birds over some two thousand miles of sea. Observers 
in other regions where littoral and inland species of the genus occur 
may perhaps devote their attention to the relation between the 
two ; and if they are able to supplement observation and 
experiment by a microscopical investigation, some interesting 
results would be obtained. For instance, I would suggest that in 
Queensland a thorough examination of the littoral E. indica and 
the inland E. vespertilio might be undertaken ; or perhaps there 
may be some other littoral form. 

With the two other Leguminous genera, Canavalia and 
Sophora, to be immediately discussed, we have for the most part 
the same questions raised. Both possess wide-ranging current- 
dispersed littoral species in other parts of the Pacific, but only 
endemic inland species with non-buoyant seeds in Hawaii. The 
pivot of the discussion will be here also the impracticability of 
these inland species ever having reached the Hawaiian Islands 



xv LITTORAL AND INLAND PLANTS' RELATIONSHIP 145 

through the agency of the currents, and the great difficulty in 
believing that their beans were carried unharmed by birds over 
half the breadth of the Pacific Ocean. If we reject alike the 
current, the bird, and the parentage of a lost littoral species, we 
must fall back on the continental hypothesis, against which in the 
case of Hawaii the evidence is overwhelming. 



CANAVALIA. 

This genus is represented in the tropical islands of the South 
Pacific from Fiji to Tahiti by three littoral species, none of which 
have been found in Hawaii, where only an endemic inland species 
exists. Reference will alone be made here to such facts as bear 
on the probable history of the mysterious Hawaiian species> 
additional particulars being given in Note 54. The littoral species, 
Canavalia obtusifolia (D. C.), C. sericea (Gray), and C. ensiformis 
{D. C.), have buoyant seeds and are dispersed by the currents ; 
whilst the inland Hawaiian species, C. galeata (Gaud.), a forest 
climber peculiar to that group, has non-buoyant seeds. We thus 
have repeated the problem of Erythrina monosperma. The absence 
of the littoral species from Hawaii can scarcely be attributed to the 
failure of the currents, since Ipomea pes caprae, which accompanies 
C. obtusifolia as a beach-creeper all round the tropical globe, is 
present on the Hawaiian beaches. Nor can it arise from lack of 
floating-power on the part of the seeds, since experiment indicates 
that the seeds of C. obtusifolia will float for months unharmed in 
sea-water. Nor can it be ascribed to climatic conditions, since 
this tropical shore species extends into cooler latitudes than 
those of the Hawaiian Islands, being found in the Kermadec Group 
and in the Bermudas, which are subtropical both in position and 
as regards much of their vegetation. The reason perhaps we may 
never learn from the plants themselves, though it may be possible 
to obtain some light on the problem from outside sources. 

Canavalia galeata differs much in its habits, as well as in some 
of its characters, from the existing littoral species of regions outside 
the Hawaiian Group. It is a stout climber ascending the forest 
trees to a considerable height, though, as is indicated in Note 54, 
the shore species sometimes display a tendency in the same 
direction. It is described by Hillebrand as occurring "on all 
islands, in forests up to 2,000 feet." Like those of the inland 
species of Erythrina (E. monosperma), its seeds sink in sea-water 
even after being kept for four years, nor could the pods be utilised 
VOL. II L 



146 A NATURALIST IN THE PACIFIC CHAP. 

for dispersal by the currents, since they float, when unopened, only 
for four or five days. Here also, as with Erythrina, the seeds of the 
inland species no longer possess the buoyant kernels to which the 
floating capacity of the seeds of the coast species is due. Though 
we have to exclude the currents, we can scarcely in its case appeal 
to bird-agency when we wish to account for the transportal of the 
original seeds to Hawaii, as that would imply that birds can carry 
beans nearly an inch, or 2 to 2*5 centimetres, in length unharmed 
in their stomachs over a tract of ocean some 1,500 or 2,000 miles 
across. We should have to learn much that is unexpected of the 
modes of dispersal of the Leguminosae before we could accept such 
an hypothesis. 

Canavalia galeata indeed presents to the student of dispersal 
one of the enigmas of the Hawaiian flora ; and it should be noted 
that the mystery of its distribution is concerned not only with the 
means of transportal of the seeds of the original species to the 
group, but also with its present dispersal among the islands. It is, 
however, suggestive that Dr. Hillebrand mentions two varieties, 
one of them found on Kauai, with somewhat smaller seeds ; so that 
some inter-island differentiation is evidently in progress. No 
attempt is made here to connect this inland species directly with 
the absent beach-plants. That is a matter for the systematist ; but 
we are not tied down to existing shore-plants in finding an ancestor,, 
since the common parent of the littoral and inland species may 
have been a shore-plant dispersed by the currents. 



MEZONEURON. 

Another closely parallel instance, offering, from the standpoint 
of dispersal, the same difficulties presented by Canavalia galeata, 
is to be found in Mezoneuron kauaiensis (Hillebr.), a tall inland 
shrub also peculiar to the group and belonging alike to the 
Leguminosse. The difficulties are so nearly identical that the 
same explanation will have to cover both ; but it is significant that 
with Mezoneuron there is no littoral species to which we can 
appeal to extricate us from the difficulty. Yet the genus is related 
to CiEsalpinia, and the species was first described by Mann as 
C. kauaiensis, so that it may have once possessed a littoral species 
that has ceased to exist as such. When we come to discuss 
Caesalpinia and Afzelia (Chapter XVII.) we shall obtain from those 
genera many suggestions as to the probable past of Canavalia 



xv LITTORAL AND INLAND PLANTS' RELATIONSHIP 147 

galeata and Mezoneuron kauaiensis, two of the greatest riddles 
presented by the Leguminosae of Hawaii. 

The flat seeds of this species of Mezoneuron measure about an 
inch (2*5 cm.), and seem most unsuitable for dispersal by birds 
over a wide extent of ocean. Nor can we appeal to the currents, 
since my experiments in Hawaii show that the seeds have no 
buoyancy and that the pods only float for a week in sea-water. 
Dr. Hillebrand records this shrub from Kauai, Oahu, and Maui ; I 
found it also on the lower slopes of Hualalai in Hawaii and there- 
fore the same question of inter-island dispersal here presents itself 
that was connected with Canavalia galeata, since we have also to 
explain the transport of the seeds between islands 70 to 150 miles 
apart. The critical point in the history of these two enigmatic 
inland plants of the Hawaiian Islands was doubtless concerned 
with the loss of buoyancy of the seeds of the original littoral plant. 
It will subsequently be shown that this is what is now in actual 
operation with Caesalpinia and Afzelia in different parts of the 
Pacific. 

SOPHORA. 

In this genus, as in Erythrina and Canavalia, we have a littoral 
species, Sophora tomentosa, that ranges over the tropical beaches 
of the globe, including most of the islands of the Pacific, but does 
not occur in Hawaii, where the genus is represented by an endemic 
inland species, S. chrysophylla. Here also we find the shore- 
species with seeds capable of floating for months on account 
of their buoyant kernels, and the inland species with seeds 
that sink even after years of drying (see Note 56). Unless other 
inland species of Sophora have recently been described from the 
tropical Pacific, the Hawaiian species is the only one of its kind 
known from this region. 

But the problem wears a different aspect in the case of this 
genus, since the endemic inland species of Hawaii is a tree of the 
mountains where a temperate climate prevails, whilst Sophora 
tomentosa is a shrub of the tropical beach that only at times 
extends into subtropical latitudes. The Mamani tree, as the 
Hawaiians name S. chrysophylla, extends up to 9,000 or 10,000 
feet above the sea, forming, with Myoporum sandwicense and one 
or two other trees and shrubs, the highest belt of the forest in the 
larger islands. It is in the open woodland between 6,000 and 
7,000 feet that it is most at home, and here it attains a height of 
20 to 30 feet. It descends in places to as low as 2,000 feet above 

L 2 



148 A NATURALIST IN THE PACIFIC CHAP. 

sea-level ; but here is living under uncongenial conditions, and, like 
Myoporum sandwicense, becomes dwarfed and shrubby. The 
climatic conditions under which S. chrysophylla thrives in the 
Hawaiian mountains are therefore those of the temperate zone. 
From the data given in Chapter XIX., the mean annual tempera- 
ture at an elevation of 6,000 to 7,000 feet would probably be about 
55, the average temperature of New Zealand. 

We must therefore look to the temperate and not to the 
tropical zone for the home of the parent species of Sophora 
chrysophylla ; and if it was originally derived from a shore-plant 
dispersed by the currents, the widespread S. tomentosa could 
scarcely have been the species concerned. But this strand-plant is 
disqualified for another potent reason, since it belongs to a 
different section of the genus. Whilst S. tomentosa belongs to 
the section possessing smooth pods, S. chrysophylla is referred to 
the section Edwardsia having four-winged pods, which comprises 
about ten species found in Chile and Peru, Hawaii, New Zealand, 
Further India, and the Isle of Bourbon. What strange principle 
in distribution, we may fitly ask, has linked together in this 
odd fashion the continents of the Old and New World and the 
islands of the Indian and Pacific oceans ? 

Yet, discredited as Sophora tomentosa is as a possible parent of 
the Hawaiian mountain species, it may yet afford us a clue. It is 
significant that the distribution of this wide-ranging beach-shrub in 
the tropics of the southern hemisphere is almost coterminous with 
that of Sophora tetraptera, a species widely spread in the south 
temperate zone from Chile to New Zealand and extending towards 
the tropics as far as Juan Fernandez in lat. 33 S. and to Easter 
Island in lat. 27 S. Though not strictly a beach-plant, S. tetra- 
ptera is a plant of the sea-border ; and it is remarkable, but not 
surprising, how in New Zealand, one of its principal homes, its 
behaviour in respect of its vertical distribution presents a great 
contrast to that of S. chrysophylla in the tropical latitudes of 
Hawaii. We have seen that, in Hawaii, S. chrysophylla, which 
thrives as a tree 20 to 30 feet high in the mountains, becomes 
shrubby when it descends to the lower levels. In New Zealand, 
S. tetraptera is, as we learn from Kirk, a prostrate shrub in the 
mountains, whilst in the lower elevations towards the sea it 
becomes a tree 30 and even 50 feet in height. It can scarcely 
be doubted that, if we exchanged the habitats of these Hawaiian 
and New Zealand species, each would to a great extent take up 
the other's station and the other's habit. 



xv LITTORAL AND INLAND PLANTS' RELATIONSHIP 149 

The whole problem of the dispersal of Sophora was brought 
immediately to my notice at Corral, in latitude 40 S. on the coast 
of Chile. Here a small tree of the section Edwardsia was growing 
in fruit on the lower slopes of the hills, becoming bushy when 
descending to the beach. Specimens of its four-winged pods have 
been identified at the Kew Museum as those of Sophora tetra- 
ptera ; and, as far as the pod is concerned, I cannot distinguish 
between my specimens of the Hawaiian S. chrysophylla and the 
Chilian species. Subsequently I found the buoyant seeds of the 
same plant amongst the stranded beach-drift at Bahia San 
Vincente, nearly 200 miles further north. This led to my experi- 
menting on the capacity of the plant for dispersal by the currents, 
and as a result it was ascertained (see Note 56) that whilst, as in 
the case of S. chrysophylla, the pods floated only one or two weeks, 
the seeds on account of their buoyant kernels floated for several 
months in sea-water, retaining their power of germination. The 
Chilian plant thus differs significantly in its capacity for dispersal 
by currents from the Hawaiian species, the seeds of which sink in 
sea-water even after years of drying. 

The Mamani tree in Hawaii had always been an object of great 
interest to me. I was attracted by the mystery surrounding its 
origin and had long suspected that the clue was to be found in the 
non-buoyancy of its seeds and in the absence of a littoral species 
of the genus. When in Fiji it was to the littoral Sophora. 
tomentosa that I looked in vain for a solution of the riddle, and 
seven years afterwards on the coast of Chile a solution of this 
enigma of the Hawaiian mountains presented itself in the form of 
an argument somewhat in this shape. 

On account of the elevated station of the Mamani tree 
(S. chrysophylla) in Hawaii it is to be inferred that the original 
species was a plant of the temperate regions or of the uplands 
of some tropical mountains. If it has had its origin in some 
shore-plant dispersed by the currents, that species can only now be 
found on the coasts of extra-tropical regions. Such a maritime 
plant had buoyant seeds ; and plants of this type are presented by 
Sophora tetraptera and its allied species that are at home in the 
cool latitudes of the southern hemisphere, as in Chile and New 
Zealand. No difficulty, as I argued, could be connected with the 
loss of buoyancy of the seeds of the Hawaiian mountain species,. 
since it follows the general principle (laid down in Chapter II.) that 
in the same genus coast species have buoyant seeds or fruits, and 
inland species those that sink ; and in support of this view it was 



150 A NATURALIST IN THE PACIFIC CHAP. 

recalled that this is what happens to the seeds of Csesalpinia 
bonducella and Afzelia bijuga when the plants extend inland 
in the Pacific islands. It was held, in short, that the original 
form of Sophora chrysophylla in Hawaii was a coast plant with 
buoyant seeds, and therefore indebted for its presence to the 
currents. Hailing from an extra-tropical region, it abandoned the 
beach and found suitable conditions of existence in the moun- 
tains, where it underwent specific differentiation. Such was the 
explanation that presented itself to me on a Chilian beach. 

The first objection that offers itself against this view is that 
Sophora chrysophylla is one of several species characterising the 
antarctic element of the mountain flora of Hawaii, and that many 
of these plants, such as those of the genera Astelia, Coprosma, 
Gunnera, Myoporum, &c., could only have reached these islands 
through the agency of frugivorous birds (see Chapter XXIII.). 
There is, therefore, something to be said for this mode of dispersal ; 
but though one can understand how hard seeds and the " stones " 
and crustaceous pyrenes of fleshy fruits might be transported 
unharmed in a bird's stomach half-way across the Pacific Ocean 
to the distant group of Hawaii, it is difficult to understand how 
Leguminous seeds, except in such cases as Tephrosia piscatoria, 
could be ejected unharmed by a bird after an ocean passage of some 
1,500 or 2,000 miles. Yet evidence pointing to such a possibility 
is not lacking. It was pointed out by W. O. Focke (Nat. schaft. 
Ver. zur Bremen, Abhandl., Band 5, 1876) that for many Legu- 
minosae we are driven to the agency of birds in order to explain 
their dispersal. In this connection he mentions the case of a 
pigeon killed by some beast of prey that he found in his garden in 
the early winter. In the following spring he noticed numerous 
seedlings of Vicia faba sprouting up from amongst the feathers 
that alone remained of the bird. In this observation he detected 
the normal method of the dispersal of the Leguminosae by birds, 
the seeds not being ejected by the bird but being set free by 
its death. It is well known that Darwin had this idea in his mind 
when he conducted his experiments on the dispersal of seeds ; and 
reference may here be made to one that is recorded in More Letters 
of Charles Danvin (i., 436). Out of a number of seeds left in 
the stomach of an eagle for eighteen hours, the majority were 
killed ; but amongst the few that germinated afterwards was a seed 
of clover (Trifolium). If such a bird had carried a Sophora seed to 
Hawaii, this would have involved a continuous flight of, on the 
average, 100 miles per hour for a period of fifteen to twenty hours. 



xv LITTORAL AND INLAND PLANTS' RELATIONSHIP 151 

This would just come within the limitations laid down by Gatke 
as regards length and velocity of flight a subject discussed in 
Chapter XXXIII. 

We will now turn to the Sophora seeds themselves for evidence 
of their capacity of surviving the perils of such a journey. The 
seeds of Sophora chrysophylla, which are about a quarter of an 
inch (6 to 7 mm.) in length, possess unusually hard coverings for 
the order, and in that respect appear fitted for dispersal by animals. 
Indeed, in the large island of Hawaii wild pigs and sheep feed on 
the pods, and no doubt aid in the distribution of the plant over the 
island through the germination of ejected undigested seeds. But 
since the species is found on most of the larger islands, it is 
apparent that to birds we must look for the explanation of its 
inter-island dispersal. Mr. Wilson, in his Aves Hawaienses, 
remarks that one of the Hawaiian finches (Loxioides) feeds on the 
seeds of this tree, which probably, he adds, also serve as the food of 
Chloridops kona, another big finch ; and it is to be inferred from 
the observations of Mr. Perkins, quoted by Mr. Evans in his book 
on Birds, that the Drepanididse, a family peculiar to Hawaii, are 
in the habit of splitting the pods of trees like Acacia koa and 
Sophora chrysophylla to obtain the seeds. It would, however, 
seem that the agency of birds confined to these islands does not 
carry us very far when we wish to explain the original transport of 
the seeds over a breadth of ocean of some 1,500 miles and more. 
Yet we know that this must have happened with some of the 
Hawaiian plants, such as Osteomeles anthyllidifolia and Nertera 
depressa, that are not confined to these islands and possess fruits 
that would attract frugivorous birds. But whether it has occurred 
with the dry beans of the Hawaiian species of Sophora is another 
matter. 

On the whole I am inclined to the view, bearing in mind the 
general indications of the Leguminosae in the Pacific, that S. 
chrysophylla originally reached Hawaii as a littoral plant through 
the agency of the currents. Many points still need investigation ; 
but it may be pointed out that South America probably received 
Sophora tetraptera from New Zealand by the West Wind Drift 
Current. 

OCHROSIA (Apocyneae). 

This genus seems to offer the strongest testimony in support of 
the derivation of an inland species from a strand-plant. The 
drupes are so large, the minimum size of the "stone" being \\ or 



152 A NATURALIST IN THE PACIFIC CHAP. 

2 inches (37 to 50 mm.), and so dry and unattractive for birds, that 
any other agency but that of the currents appears to be out of the 
question. 'Indeed their dry appearance would suggest to my 
readers that only birds of the habits of the ostrich would venture 
on such a diet. It is, however, worth noting that whilst in the 
Keeling Islands I learned that a cassowary that had been kept on 
the atoll was a very efficient distributor of the seeds of Ochrosia 
parviflora, scattering the undigested stones everywhere, and causing 
the young trees to become so numerous that they had to be 
destroyed. A similar habit of the cassowary in the Aru Islands is 
recorded by Beccari, where the dry fruits of a palm, 2j inches 
across, are swallowed by these birds and the seeds dispersed. 
Cassowaries are active agents in dissemination, for they swallow 
every kind of pulpy fruit, and convey them long distances 
undigested ; they are also excellent swimmers and traverse 
considerable expanses of water (Beccari, quoted in Chall. Bot., iv., 

297, 313). 

Modern ornithologists would probably not object to our appeal- 
ing to the former volant habits of the cassowary and its allies even 
across a wide tract of sea ; but, excepting in New Zealand and its 
vicinity, such birds are not at our disposal in the island groups of 
the open Pacific. There is a possibility that the extinct Columbse 
and other exterminated birds of the Mascarene Islands might 
account for some anomalies in their floras ; and in Chapter XVI. 
reference is made to the fact that these islands possess more 
endemic species of Pandanus than any other oceanic groups, 
a genus possessing drupes that in the case of inland species seem 
unfit for any mode of dispersal with which we are familiar. In the 
islands of the tropical Pacific, however, it is not possible to find 
such a way out of the difficulty, since, as shown in Chapter XXX 1 1 1., 
the birds are lacking. 

The genus, according to the Index Kewensis, includes about 
ten species distributed over the islands of the Indian Ocean, and 
found also in Malaya, Australia, and throughout the Pacific. It is 
essentially an insular genus, and two at least of the species are 
wide-ranging littoral trees, one, Ochrosia borbonica, mainly dis- 
tributed over the islands of the Indian Ocean and of Malaya, 
and the other, O. parviflora, chiefly of the islands of the Pacific. 
It will be out of place to deal here in any detail with this 
interesting genus, and my remarks will be confined to such matters 
as concern the origin of the inland species of the Hawaiian Islands, 
species that are peculiar to that group. Some confusion has pre- 



xv LITTORAL AND INLAND PLANTS' RELATIONSHIP 153 

vailed amongst different authors in the determination of the limits 
of the various species, and to avoid this I have mainly followed 
Schumann in his monograph on the order (Engler's Naturl. Pflanz. 
Fam., Theil 4, Abth. 2, 1895), as indicated in Note 57. 

Besides the littoral species Ochrosia parviflora, Hensl., that 
ranges over most of the archipelagoes of the Pacific from the 
Solomon Islands to Tahiti, but is not found in Hawaii, we have in 
the Pacific, O. elliptica, Lab., of New Caledonia and Fiji ; another 
species of New Guinea and the Ladrones ; and one or two inland 
species of Hawaii. Ochrosia parviflora was familiar to me on 
Keeling Atoll, in the coral islets of the Solomon Group, and 
on the islets and coasts of certain parts of Fiji. Its fruits, which 
are dispersed by the currents, were found amongst the stranded 
drift of the Keeling and Fijian beaches. Although usually a coast- 
tree in Fiji, it came under my notice in one locality growing 
inland ; and it is a very suggestive circumstance in connection with 
the inland species of Hawaii, that in Tahiti this tree is only 
described by the French botanists as growing in the mountains at 
elevations of 700 to 800 metres above the sea, it having for some 
reason abandoned the beach. The process which we thus see 
in operation in Tahiti is completed in Hawaii, and we there find a 
peculiar inland species far away in the interior of the islands which 
is placed by Schumann in the same section of the genus with the 
littoral O. parviflora, that is not, however, found in the group. 
It may be remarked that Gray describes only one species from 
Hawaii, O. sandwicensis, but Schumann makes two species of it 
one, O. compta, Sch., peculiar to the group and referred to the 
same section as O. parviflora ; the other, the original species of 
Gray, which he considers as probably a variety of O. borbonica. 
These determinations of the German botanist, who had no theory 
to serve, are especially interesting. It is with the littoral trees 
now missing from the Hawaiian beaches that he compares the 
inland species of the group, trees now chiefly characteristic the 
one of the Indian Ocean and the other of the South Pacific ; and 
we can scarcely doubt that originally one littoral tree ranged over 
both oceans. 

Hillebrand describes Ochrosia sandwicensis of Gray as a shrub 
or small tree, 6 to 12 feet in height, growing in the open woods of 
the lower and middle regions on all the islands. Its dry ellipsoid 
fruit is two inches (5 cm.) long, and possesses a thin suberose covering 
on one side and a very thick woody endocarp, one-quarter to one- 
third of an inch (6 to 8 mm.) in depth. The other species which he 



154 A NATURALIST IN THE PACIFIC CH. xv 

characterises as a variety is not so generally distributed in the 
group. We have to explain not only how the original species 
reached the group, but also how they have been distributed over 
the islands. The currents could scarcely have transported the 
fruits as we now see them. Those of O. sandwicensis have only a 
trace of a buoyant covering, and, judging from some fruits that I 
examined, they could possess little or no floating power. Even the 
most enthusiastic advocate of dispersal by birds must pause here ; 
and there remains the view, supported by evidence of a striking 
character, that the inland Hawaiian species are derived from littoral 
species that, having. been originally brought by the currents, like 
O. parviflora in Fiji, abandoned the beach and took to the 
mountains, where they have become differentiated. 

It is probable that the lesson of Ochrosia in Hawaii can be 
applied to one or two of the other Hawaiian " difficulties," and 
that plants that now set at defiance all the attempts of the student 
of dispersal to explain their occurrence in this group may have 
commenced their existence in these islands as littoral species 
brought originally by the currents and afterwards driven off the 
beach. One of the greatest enigmas of the Hawaiian flora is 
connected with another small Apocynaceous tree peculiar to the 
group and described by Hillebrand as Vallesia macrocarpa and by 
other Hawaiian botanists as a species of Ochrosia. Schumann, 
however, places it in a new genus, Pteralyxia, near to Alyxia, 
a genus already in the islands. However this may be, its dry 
drupaceous fruits two inches (5 cm.) in length, and its pyrenes 
almost as long, could never have been transported as such by the 
birds of our own time ; and if they could have been carried in the 
stomach of a bird given to the dietetic humours of the cassowary, 
such birds in their trans-oceanic passages would have left some 
trace behind in the groups of the mid-Pacific. In our perplexity 
we read again the lesson of Ochrosia. 

Summary of Chapter (see end of Chapter XVI.). 



CHAPTER XVI 

THE RELATION BETWEEN LITTORAL AND INLAND PLANTS 

(continued) 

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 Columbas or extinct Struthious birds. 
Barringtonia. Guettarda. Eugenia. Drymispermum. Acacia laurifolia. 
Conclusions to be drawn from the discussion. Summary of chapters 
XIV, XV, XVI. 

SECTION IV 

HERE we deal with two genera, Pandanus and Barringtonia, 
where inland endemic species occur in the same group with the 
wide-ranging coast species, but possess fruits concerning which it 
is either difficult or almost impossible to suggest a mode of dispersal 
by existing agencies. This section is especially concerned with 
Fiji, and represents the peculiar " Fijian difficulty " that is illustrated 
by other genera as for instance, the Coniferous genus Dammara 
which are not in any sense littoral. Further investigation is, 
however, requisite in the case of Barringtonia, and to a less degree 
with Pandanus ; and I can only here point to the general indica- 
tions of the data at my disposal. We have in these genera to 
assume either that the inland species are derived from the coast 
species, or that the seeds were brought by one of the extinct 
birds of the Western Pacific, by a megapode or by one of the 
Columbae, or by some Struthious bird like the moa or the 
cassowary, or, if these two assumptions fail, that there has been a 
continental connection through the islands to the westward with 
the mainland beyond. 

PANDANUS. 

I take this genus first because the recent monograph on the 
Pandanaceae by Dr. Warburg (Engler's Das Pflanzenreich, 1900) 



156 A NATURALIST IN THE PACIFIC CHAP. 

enables me to tread on relatively safe ground in making my 
deductions. The three genera of the order, Freycinetia, Pandanus, 
and Sararanga, each tell their own story ; and in each and all of 
them I have taken an especial interest from the standpoint of 
their dispersal. Freycinetia is fully discussed in Chapter XXV., 
and presents no difficulties respecting its dispersal. In the 
discovery of Sararanga the author has had a share. It was first 
established by Mr. Hemsley from specimens sent by me to Kew in 
1885 ; and it has received from the botanist the name given to it 
by the natives of the islands of Bougainville Straits in the Solomon 
Group, where I first collected it. It contains only one species and 
was also discovered by Dr. Beccari, the celebrated Italian botanist, in 
Jobie Island, New Guinea. From the other two genera of the 
order, Pandanus and Freycinetia, it stands quite apart ; and it 
apparently presents us with a relic of some ancient flora on the 
western borders of the Pacific. Its fleshy drupes (one-half to three- 
quarters of an inch in size) inclosing several small osseous pyrenes 
seem suited for dispersal by birds ; and it is not at first sight easy 
to understand why its distribution should be so limited, unless this 
is connected with its dioecious habit (see Guppy's Solomon Islands, 
p. 302 ; Journ. Linn. Soc. Bot. vol. xxx. ; and Warburg's monograph). 
It is, however, with the genus Pandanus that we are here 
especially concerned. If the advocate of the previous continental 
connections of Fiji and the groups around were to look for 
evidence in support of his views, he apparently could not do better 
than take this genus. Whilst P. odoratissimus, the littoral species 
of tropical Asia and Malaya, is found on the coasts of almost 
all the Pacific islands from Fiji to Tahiti and northward to 
Hawaii, it is only in the archipelagoes of the Western Pacific, 
namely, in Fiji and Samoa, that inland endemic species have been 
found. (Such species occur also in the more western islands 
not dealt with here New Caledonia, Solomon Islands, &c.) Not 
even in Hawaii, with all its botanical evidence of antiquity, has an 
inland endemic species been found, although the coast species 
extends miles inland, and for nearly 2,000 feet up the mountain 
slopes. When, however, we turn to Fiji and Samoa, we find in 
each group two endemic inland species. To endeavour to connect 
the inland species of Fiji and Samoa with the widespread littoral 
Pandanus odoratissimus, that owes its dispersal largely to the 
currents, is out of the question, at least for the student of plant- 
dispersal, since they belong to different sections of the genus, and 
in their characters are often far removed (see Note 58). 



xvi LITTORAL AND INLAND PLANTS' RELATIONSHIP 157 

As regards the agency of birds, it is of course possible that 
fruit-pigeons that can disperse the " stones " of Canarium and 
Elaeocarpus could transport the smaller drupes of Pandanus to 
oceanic islands like the Fijis, Samoa, and the Mascarene Islands ; 
and in Note 58 reference is made to the size of the drupes of the 
endemic species of Pandanus in those groups. But my difficulty is 
that I have not come upon any record of birds eating these fruits ; 
and I should imagine that amongst living birds only those like the 
cassowary and its kin would prefer such a kind of diet ; whilst the 
only pigeon that could have ever attempted it must have been able 
to swallow pebbles like the dodo. It is remarkable that the 
Mascarene Islands, the home of the extinct Columbse, possess more 
endemic species of Pandanus than any other groups. 

Dr. Warburg points out that, with the exception of some three 
or four species dispersed by the currents (P. dubius, P. leram, 
P. polycephalus, P. odoratissimus), almost all the species (156 in 
number) are very restricted in their areas. When we look at his 
table of the distribution of the genus we notice that, excepting the 
islands of the Hawaiian and Tahitian regions, nearly all the 
elevated or mountainous islands of the tropical and subtropical 
latitudes of the Indian and Pacific oceans have their peculiar 
species, whether in the case of Mauritius, Rodriguez, Reunion, and 
the Seychelles in the one ocean, or of Lord Howe Island, New 
Caledonia, Fiji, and Samoa in the other. The student here hesi- 
tates even to raise the question of present plant-dispersal in the face 
of such evidence of isolation all over the area of the genus. He is 
almost inclined to evade the issue and to place the matter beside 
that of the dying or extinct Columbae that have been found in 
some of these islands, as in Mauritius, Rodriguez, Reunion, and 
Samoa. 

For reasons above given in the instance of Fiji and Samoa, 
it would seem futile to attempt to connect in their origin the inland 
with the coast species ; and it may be inferred that, excepting the 
few dispersed by the currents, the species are in the main inland in 
their stations. Those peculiar to Fiji, for instance, occur in the 
swampy forests of the lower regions of the interior, as well as high 
up towards the mountain summits. When traversing the Fijian 
forests I often used to speculate on the modes of dispersal of the 
plants familiar to me ; but the sight of a strange Pandanus usually 
brought my speculations to a close. Many of the enigmas of 
insular floras would be solved if we could interpret aright the 
156 species of Pandanus that are enumerated and described by 



158 A NATURALIST IN THE PACIFIC CHAP. 

Dr. Warburg in his monograph. Observers like myself obtain 
little peeps into the conditions of existence of these interesting 
plants ; and the travelled botanist, who becomes a systematist 
in his later years, attains to a far more extensive view, yet even 
he can only penetrate the mystery for a little way. 

It is doubtful whether Pandanus odoratissimus, the shore-tree 
of the tropical beaches of the islands of the Pacific and Indian 
oceans, of Australia, Malaya, and Southern Asia, can aid us much 
in any one locality, since its distribution has no doubt been often 
assisted by man. Yet it is probable that the currents have played 
a predominant part in its dispersal. Its fruits occur commonly 
in beach-drift, both in the Indian and Pacific oceans, and are 
often incrusted with serpulae, polyzoa, and cirripedes. At certain 
seasons the currents bring them to Keeling Atoll in abundance. 
When, however, we come to inquire why it is that this beach 
species is the only representative of the genus in Hawaii and 
Tahiti, we are met with the possibility of its having been introduced 
by the aborigines. The tree is almost as useful to a Polynesian as 
the coco-nut palm, and it has been cultivated by him in some of 
the atoll-groups, as in the Marshall and in the Radack archipela- 
goes. In Chapter VII. good reasons are advanced for regarding it 
as an aboriginal introduction into Hawaii. When, therefore, we 
learn that in the group just named it extends from the sea-coast 
to nearly 2,000 feet above the sea, that in Samoa it may at 
times be found at a similar elevation though usually restricted to 
the sea-border, and that in the same way in Tahiti and in Fiji 
it may leave the coast-region and extend into the heart of the 
islands, we are not inclined to look for any marked differentiation 
in its character. This indeed appears to be the case. Numerous 
varieties in different regions are referred to by Dr. Warburg ; but 
the only important one in the Pacific islands here mentioned is 
a cultivated form from the Marshall Group. A variety from 
Hawaii is distinguished chiefly by the smaller size of its drupes. 

Assuming, therefore, that the inland species are as a rule 
not derived from littoral species originally brought by the currents, 
and that no birds of our own time are in the habit of carrying the 
drupes of Pandanus to oceanic islands, in order to explain the 
distribution of such species we have to choose between the 
possibility of the agency of extinct Columbae and birds similar 
in their habits and the alternative of a continental connection. 
Dr. Warburg, who says but little of the mode of dispersal of 
Pandanus drupes, regards the genus as having now two centres, 



xvi LITTORAL AND INLAND PLANTS' RELATIONSHIP 159 

one in the East African islands (Madagascar, the Mascarenes, and 
the Seychelles), and the other in Papuasia (New Guinea, extending 
doubtless to New Caledonia). My readers will recall to their 
minds that zoologists have at times felt bound to postulate a 
continent in both the centres of the genus Pandanus. There is the 
well-known Lemuria of the Indian Ocean, and then we have in the 
Western Pacific Forbes' Antipodea and Hedley's Melanesian 
Plateau. 

Before, however, we accept the indications of the distribution of 
Pandanus as favouring a continental hypothesis for either area it is 
essential to exclude the agency of the extinct Aves. In this con- 
nection it is of prime importance to notice that the Mascarene 
Islands are remarkable, when contrasted with all other oceanic 
islands, not only for the predominance of peculiar species of 
Pandanus, but also as having been the home of extinct Columbae 
like the dodo and the solitaire. The dodo's habit of swallowing 
pebbles of the size of a nutmeg (Encyclop&dia Britannica, vii., 322),, 
and the solitaire's inclination for swallowing stones as large as a 
hen's egg (Birds, by A. H. Evans, p. 331), doubtless represent, as 
explained below, a capacity for the dispersal of large fruits and 
seeds that would be regarded as " impossible " for distribution by 
birds now. It is quite possible that at some time the ancestors of 
these birds possessed the powers of flight now owned by the 
Nicobar pigeon, in the gizzard of which, in the Solomon Islands, I 
found quartz pebbles half an inch across (Solomon Islands, p. 324). 
In the work just quoted I refer on page 325 to the observation of 
Messrs. Chalmers and Gill that the Goura pigeon of New Guinea 
usually carries a good-sized pebble in its gizzard. We do not>. 
however, seem to possess any record of extinct Columbae in the 
tropical islands of the Western Pacific. The nearly extinct 
Didunculus of Samoa apparently prefers berries and soft fruits. 
Dr. Reinecke says that it especially favours the berries of Cananga 
odorata, the seeds of which are not over a third of an inch (8 mm.) 
in length. 

It would appear from Mr. Hamilton's note in the Transactions 
and Proceedings of the New Zealand Institute (vol. 24) that the 
extinct Struthious birds of New Zealand, as in the case of the moa, 
carried crop-stones sometimes as large as a pigeon's egg. These 
pebbles are, of course, swallowed by birds to enable them to crush 
the hard seeds, and " stones " of fleshy fruits, on which they feed- 
In the Solomon Islands I noticed that the Nicobar pigeon was 
able in this way to crack the seeds of Adenanthera pavonina, which 



160 A NATURALIST IN THE PACIFIC CHAP. 

for their fracture require a blow with a hammer. The implication is 
that the extinct Columbae were able to transport to oceanic groups 
seeds and " stones " which no existing pigeon could now carry over 
a tract of ocean. I am inclined to extend this view also to extinct 
Struthious birds, and to suppose that they were able, like the casso- 
wary (see page 1 52), to fly across tracts of sea in ages gone by. Though 
such an agency would come under discussion in connection with 
the floras of New Zealand and Madagascar, we have no evidence 
to show that birds of this family ever reached the tropical islands 
of the open Pacific. 

The Megapodidae of the Western Pacific are a family of birds 
that suggest themselves in this connection. Their distribution 
corresponds with that of Pandanus in the Western Pacific, except- 
ing the littoral species ; and like Pandanus the Megapodes have 
41 differentiated " in every group. The limited powers of flight 
possessed by existing species would unfit them for crossing wide 
tracts of sea ; but the parent form or forms of all these species 
must have been able to traverse broad tracts of ocean. These 
birds subsist on fallen fruits, seeds, &c. ; but I have no data 
relating to them as seed-dispersers. 

It is evident from the endemic character of most of the species 
of Pandanus in oceanic islands that, except with a few widely-spread 
littoral species, the dispersal of the genus has been for ages 
suspended. Whether the explanation is to be found in the isola- 
tion and differentiation of the extinct Columbae of the Mascarene 
Islands, where the endemic species of Pandanus are most numerous, 
has yet to be established. It seems to offer the only way out of 
the difficulty, unless we accept the old view concerned with the 
continent of Lemuria. 

BARRINGTONIA. 

There are two littoral species of this genus in the Pacific, 
B. speciosa and B. racemosa, both widely spread over the Old 
World, but only the first is generally distributed over the Polynesian 
region reaching east to Ducie Island, whilst the second does not 
extend east of Fiji and Samoa. With the exception of one or two 
inland species in Fiji and Samoa no inland species have been 
recorded from the groups of the open Pacific, and the genus is not 
represented at all in Hawaii. If it were not for a suspicion that the 
aborigines may have aided in the distribution of the inland species, 
the advocate of the previous continental connections of the islands 



xvi LITTORAL AND INLAND PLANTS' RELATIONSHIP 161 

of the Western Pacific would receive from their occurrence in these 
islands considerable support for his views. The fruits of the 
inland Fijian species are large, the smallest being three inches in 
length ; and the agency of birds seems to be out of the question. 

The fruits of the littoral species possess dry buoyant husks that 
enable them to be carried by the currents over wide tracts of ocean. 
Those of the Fijian inland species display only a trace of these 
buoyant coverings and the floating power is much diminished or 
absent altogether. These inland species are two or three in 
number. One of them, described as a new species by Seemann 
under the name of B. edulis, has edible kernels and is sometimes 
cultivated. A species that I found growing in the plantations 
of the Solomon Islanders in Bougainville Straits may be near 
the Fijian tree just named {Solomon Islands, pp. 85, 297). Its 
kernels are edible ; and I may add that the Solomon Islanders 
cultivate other species with edible fruits. We cannot, therefore, 
exclude the agency of the aborigines in the distribution of the 
inland species of this genus. Home found an undescribed species 
in Fiji, which may be that which I found on the slopes of Mount 
Seatura in Vanua Levu, as described in Note 50 ; and it is quite 
possible that it was originally a cultivated tree, though not 
necessarily within the memory of the later generations of the 
aborigines. 

This retrocession to the wild state of cultivated plants and the 
resulting production of apparently new species is a point on which 
Dr. Beccari lays considerable stress in the English edition of his 
book on the Great Forests of Borneo. He takes the case of 
Nephelium and other fruit-trees and shows how in old clearings, 
long since abandoned, they have undergone singular alteration in 
characters. For these reasons, therefore, Barringtonia can scarcely 
be regarded as offering in its inland species unequivocal evidence 
of a previous continental condition of the islands of the Western 
Pacific. Nor, as shown in Note 50, should we be justified in 
establishing a genetic connection between the inland and coast 
species ; but a great deal of research is needed before we can 
handle the numerous interesting problems connected with the 
genus ; and indeed it cannot be said that the specific limits of the 
inland Polynesian trees have been definitely determined, or the 
species themselves diagnosed. 



VOL. II M 



162 A NATURALIST IN THE PACIFIC CHAP. 



SECTION V. 

In this section are included those genera where within the same 
genus some inland species have been derived from the coast species 
whilst others have been originally brought by birds. Guettarda alone 
belongs here. In this genus we find, as is so frequently the case, 
a littoral tree (G. speciosa) widely spread in the Old World and 
ranging over the whole tropical Pacific as far east as Pitcairn and 
Elizabeth islands, but absent from Hawaii. Here also as with 
Pandanus it is only in the Western Pacific that we find inland 
endemic species so distinct in character from the littoral tree that 
they may be regarded as of independent origin. 

Since, however, there is an inland form of the coast species in 
Tahiti (Guettarda speciosa, var. tahitensis) which, according to 
Drake del Castillo, is distinguished only by its more rounded 
leaves and by the more marked pubescence of the under leaf- 
surfaces, we evidently have there an inland species in process of 
development from the littoral species. This inland tree is found 
at elevations as great as 600 metres or almost 2,000 feet above the 
sea ; and indeed if we follow Nadeaud the specific differentiation 
is complete. However, there is no doubt raised as to its close 
affinity to the beach tree ; and we are almost compelled for another 
reason to regard it as a derivative of the shore species, because, as 
pointed out in Chapter XX VI I., there are very few inland plants in 
the Tahitian flora possessing fruits as large as those of Guettarda 
that owe their presence in those islands to frugivorous birds. 

Of the two inland species of the genus found in Fiji, G. 
inconspicua and G. vitiensis, it may at once be said that, as indicated 
in Dr. Seemann's work, their characters are far from suggesting any 
connection in origin with G. speciosa, the shore-species, the inland 
and littoral plants belonging to different sections of the genus. In 
their case we can only look to the frugivorous bird for the explana- 
tion of their existence in the group. The fruits would be probably 
small ; and in this connection it is to be noted that Mr. H. N. 
Ridley in his paper on the flora of Fernando Noronha evidently 
looks to birds to account for the presence of a species of Guettarda 
on the island, a species not found elsewhere. 

But another inland Fijian form of Guettarda found by me in 
Vanua Levu at elevations of 1,000 to 1,400 feet above the sea, and 
dubbed by the natives with the name of the littoral tree (Mbua- 
mbua), corresponds in its close relation to G. speciosa with the 



xvi LITTORAL AND INLAND PLANTS' RELATIONSHIP 163 

inland Tahitian form of that tree, and is to all appearance a 
derivative of it. It is chiefly distinguished by its thinner, more 
hairy leaves, which taper at each end and are not subcordate at the 
base as is often the case with the leaves of G. speciosa. The 
coverings of the fruit are less fibrous and the putamen is not 
so deeply notched or grooved. The difference also extends to 
the buoyancy of the fruits in accordance with the principle laid 
down in Chapter II. Whilst those of G. speciosa float for many 
months and are of common occurrence amongst the stranded drift 
of tropical beaches, as for instance in the Keeling Islands, in the 
Solomon Group, and in Fiji, those of the inland species float only 
for a few weeks, their softer coverings decaying more rapidly 
in sea-water. 

We seem therefore to have had two principles at work in Fiji 
in determining the origin of the inland species of Guettarda. 
Whilst in one case the inland species is so sharply distinguished 
from the coast species as to require the independent agency of 
frugivorous birds to explain its presence, in the other the inland 
form, as in the instance also of the Tahitian variety, is so much 
akin to it that the probability of derivation from it is very great. 



SECTION VI. 

In this section are contained genera possessing littoral species 
restricted to the Western Pacific islands, and dispersed by birds, 
but having little or no capacity for dispersal by the currents. 
They are regarded as derived from the inland species of the genus 
in the western part of the Pacific, and as distributed from thence 
over the islands in that part of the ocean. We are here only 
concerned with Fiji, Tonga, and Samoa and the neighbouring 
islands. The genera Eugenia, Drymispermum, and Acacia are 
here comprised. 

The genus Eugenia, though essentially inland in its station, is 
apt to lend species to the beach-flora in different parts of the 
tropics. Such species, being dispersed by frugivorous birds and 
other animals, and possessing but slight capacity for distribution 
by the currents, are usually restricted in their areas. Thus, 
Schimper (p. 118) names two or three species, including E. 
javanica, as amongst the Indo-Malayan strand-flora. Ridley 
notices that E. grandis is a common sea-shore tree in the Malay 
peninsula ; and the author observed two littoral trees of the genus 

M 2 



1 64 A NATURALIST IN THE PACIFIC CHAP. 

in the islands of Bougainville Straits in the Solomon Group, the 
fruits of one of them that flourished in the interior of the coral 
islets being found in the crops of fruit-pigeons. So also in Fiji, 
some of the inland species, as E. rariflora, appear at times amongst 
the strand vegetation and in the coral islets. There is, however, 
one Fijian species found also in Samoa and Tonga that is a 
characteristic beach tree, namely E. richii (Gray), and it is more or 
less confined to that station. The fruits will float a fortnight 
in sea-water, which is nearly twice as long as most other Eugenia 
fruits will float ; and it is quite possible that the currents may 
assist the pigeons in distributing the species. This genus is dealt 
with more in detail in Chapter XXVI. 

The genus Drymispermum (Thymeleaceae) comprises in the 
Western Pacific a number of species, of which two range over the 
groups of Fiji, Tonga, and Samoa, whilst some four or more 
are peculiar to Fiji. All are inland plants with the exception 
of D. Burnettianum, a characteristic littoral shrub of these three 
groups. Its bright red drupes float only from five to ten days, even 
after some weeks of drying ; and like those of the inland species 
they are well suited for dispersal by fruit-pigeons. This beach- 
plant may be regarded as probably an intruder in the strand-flora 
from the interior of one of the islands of the Western Pacific, 
whence birds, perhaps assisted a little by currents, have carried it 
to the neighbouring groups. 

The very remarkable coast tree, Acacia laurifolia, alone repre- 
sents its genus in the littoral flora of the Pacific islands. It is con- 
fined to the Western Pacific, having been found in New Caledonia, 
the New Hebrides, Fiji, Tonga, and Samoa ; but it is doubtful 
whether it is truly indigenous in all these localities. Thus, in 
Samoa, though restricted to the coast districts, as we learn from 
Reinecke it seldom flowers, and according to that botanist it 
was probably introduced through cultivation. It is, however, 
evidently regarded by the Samoans as a tree of their group, as 
is shown in a curious legend, given by Dr. George Turner in 
his latest book on those islands, which I have quoted in my book 
on the Solomon Islands, p. 287. Both in Fiji and Samoa it bears 
the name "tatangia" or "tatania," whilst its hard wood was 
employed for various purposes, the leaves being used as spoons. 
The tree flowers and seeds freely on the Fijian beaches. The pods 
dry up on the plant, and do not dehisce, but are apt to break 
across between the seeds into article-like portions, the seeds being 
ultimately liberated by the decay of the pod or its fragments. 



xvi LITTORAL AND INLAND PLANTS' RELATIONSHIP 165 

The seeds either sink at once or in the course of a day or two ; 
whilst the pods or their fragments float at first in sea-water, but all 
are at the bottom in a week or less. With its absence of any 
apparent means of dispersal this small tree presents quite an 
anomaly in the strand-floras of the Western Pacific, and can only 
be regarded as a loan from the inland flora, though probably of a 
very ancient date, and perhaps going back like Acacia koa, the 
forest-tree of Hawaii, to some early epoch in the history of these 
islands. 



The conclusions to be drawn from the discussion of the relations 
between the littoral and inland species of the same genus in 
the Pacific islands. (Chapters XIV., XV., XVI.) 

In ten of the twenty-two genera here dealt with (Calophyllum, 
Hibiscus, Colubrina, Morinda, Scaevola, Cordia, Ipomea, Vitex, 
Tacca, Casuarina) the shore and inland species have their own 
independent modes of dispersal, usually by currents in the case of 
coast plants, and by birds in that of inland plants ; and the 
relations between the two are not such as to suggest a derivation 
of one from the other. 

In six genera the inland species are regarded as derived from 
the littoral species. In two of them, as in Vigna and Premna, 
where the coast and inland species occur in the same group of 
islands and are connected by intermediate forms, there is direct 
evidence in favour of this conclusion ; but such a development 
of inland species need not have taken place in every group, since 
in the instance of Premna it has apparently occurred only in 
the Western Pacific, and the inland and coast species have 
extended independently to the eastern groups through the agencies 

of birds and currents In the other four genera (Canavalia, 

Erythrina, Sophora, Ochrosia) we have presented the so-called 
" Hawaiian difficulty," that group being alone concerned. Although 
these genera have no littoral species in Hawaii, they have inland 
species in those islands, which are in three genera endemic. Since 
these inland species have non-buoyant seeds or seedvessels, the 
transport of which by birds half-way across the Pacific Ocean is in 
the case of the first three genera unlikely and in the last impossible, it 
is assumed that they are all derived from original coast species with 
buoyant seeds or fruits, such as are widely distributed over the 
Pacific but are not now existing in Hawaii. This assumption, 
in the instance of the Leguminosae, to which the first three genera 



166 A NATURALIST IN THE PACIFIC CHAP. 

belong, derives support from the singular fact in the distribution of 
the order pointed out by Mr. Hemsley, that it is wanting in many 
oceanic islands where there is no littoral flora. 

In one genus, Guettarda, the inland species are regarded as 
having been sometimes developed independently of the coast 
species, and as at other times derived from it, both principles 
having been at work in Fiji and only the last in Tahiti. 

In two genera, Pandanus and Barringtonia, which represent the 
" Fijian difficulty," there is no reason on grounds of affinity to 
connect the inland with the coast species ; and since the agency of 
existing birds is improbable in the first genus and out of the 
question in the second, whilst the operation of the currents is 
excluded for the inland species of both genera, it is assumed that 
we must either appeal to the agency of extinct birds, such as those 
of the Mascarene Islands, or we must fall back on the hypothesis 
of a continental connection. In the instance of Barringtonia it is 
also possible that some of the inland species may have been derived 
from species spread through cultivation. 

Lastly, in three genera (Eugenia, Drymispermum, Acacia) the 
coast species are viewed as derivatives of the inland flora in the 
Western Pacific, not necessarily in Fiji, but it may be in New 
Caledonia or in one of the other large groups. In this case the 
coast species of all three genera are either unfitted for dispersal by 
currents, or display the capacity only in a small degree. 

We thus see that in only seven of these twenty-two genera, 
containing both littoral and inland species in the Pacific islands, 
can it be argued from the standpoint of dispersal that the inland 
species are or may have been derived from the shore species ; and in 
most instances the evidence is largely presumptive in its character. 
In three genera the reverse has been the case, and here the coast has 
borrowed from the inland flora, In twelve, or more than half of the 
genera, the shore and inland species have been evidently inde- 
pendent in their origin. It is accordingly apparent that in the 
Pacific the strand flora has lent more to the inland flora than it has 
borrowed from it ; but with a large proportion of these coast genera 
no interchange has taken place. Two-thirds of the genera of the 
beach-plants have no inland species, and in their case the question 
of such a connection cannot be raised. With the remaining genera 
such a relation can be suggested in only two-fifths of the cases, or 
in about one-seventh of the total number of beach genera. Where 
a connection can be traced, it points more frequently to the deriva- 
tion of the inland from the shore plant. Taking all the evidence 



xvi LITTORAL AND INLAND PLANTS' RELATIONSHIP 167 

together, the beach flora presents itself in the Pacific as practically 
independent of the inland flora as regards its origin. It has 
received in these regions but few recruits from inland. It has 
yielded, except in Hawaii, but few recruits to the inland flora. In 
this ocean it bears the stamp of a high antiquity, though in the 
mass no doubt of more recent origin than the mangrove flora. 

Yet, as I have remarked in different parts of this work, even 
with the beach genera possessing no inland species, considerable 
variety is displayed in the behaviour of the strand species. Thus, 
whilst some, like Pemphis acidula, Tournefortia argentea, and 
Triumfetta procumbens, rarely if ever leave the beach, others, like 
Heritiera littoralis and Excaecaria agallocha, find a home on the 
borders of the mangrove swamps, and one or two extend inland 
and take their place in the forests, either as trees (Afzelia bijuga) 
or as giant climbers (Entada scandens). Others again, like 
Cassytha filiformis, Cerbera Odollam, and Cycas circinalis, with a 
number of other beach-plants, may invade the interior of the island 
wherever arid plains or exposed scantily wooded districts offer 
conditions conformable to the xerophytic habit of the beach-plants. 
It will thus be perceived that although the inland and coast 
floras of an island are in the mass distinct, the line of separation is 
by no means always well defined. Beach-plants are something 
more than salt-lovers in their ways. They are in the first place 
xerophilous, or, in other words, they will be equally at home in 
exposed situations away from the coast where the soil is dry and 
the rainfall scanty. Whenever these conditions are presented by 
the districts backing the coast, as we find for instance in the plains 
on the lee or dry sides of many a Pacific island, the shore-plants 
will often leave the beach and travel far inland. 



Summary of Chapters XIV., X F., A' VI. 

(1) Though littoral floras are as a rule chiefly made up of 
two sets of plants, one brought through the agency of the currents 
from regions outside, and the other derived from the inland flora 
of the region concerned, the proportion of the two varies much 
amongst temperate and tropical strand-floras, the current-borne 
plants forming the majority in the tropics, and those from the 
inland flora of the region prevailing in the temperate zone. 

(2) There is, therefore, far greater uniformity as a rule amongst 
tropical strand-floras than in the temperate zone, since in temperate 
latitudes the prevailing constituents of the strand flora vary with 



1 68 A NATURALIST IN THE PACIFIC CHAP. 

the inland flora of every region, whilst in the tropics the pre- 
dominant plants are those ranging far and wide on the shores of 
the warm regions of the globe. 

(3) Regarding the tropical strand-flora as comprising two forma- 
tions, that of the beach and that of the mangrove swamp, the last, 
which is the older of the two, may, it is suggested, be viewed as the 
remnant of an ancient flora widely spread over the lower levels and 
coastal regions of the globe, during an age when, in a warm 
atmosphere charged with watery vapour and heavy with mist and 
cloud, vivipary or germination on the plant was not the exception 
but the rule. 

(4) But it is contended that even in the beach formation 
some of the plants may date back to this age of vivipary, as is 
indicated by the anomalous seed-structures of some of the genera, 
such as Barringtonia, which seem to indicate a lost viviparous 
habit. 

(5) Since the beach formation of the islands of the tropical 
Pacific is largely formed of plants ranging over great areas in the 
tropics, there is no reason to expect that it owes much to recruits 
from the inland floras of this region. The discussion, therefore, of 
the relation between the littoral and inland floras is mainly 
concerned with the possible origin of inland from coast plants 
in these islands. 

(6) Yet there are numerous cases of genera possessing both 
coast and inland species that are of peculiar interest in determining 
the true relation between the beach and inland floras. 

(7) As the result of a detailed discussion of these genera, 
the conclusion is formed that the beach and inland floras have 
been in the main developed on independent lines, the beach flora 
receiving from the inland flora but few recruits, and except in 
Hawaii yielding but few plants to the inland flora. Only a third 
of the genera of the beach flora have also inland species, and in 
only a few of these genera, or about a seventh of the whole beach 
flora, can any question of a connection between coast and inland 
species of the same genus be raised. 

(8) Two special difficulties arise in this discussion. The first is 
the " Hawaiian difficulty," which is more particularly concerned 
with genera of the orders Leguminosae and Apocynaceae. Here are 
genera which possess both inland and littoral species, but only the 
first occur in Hawaii. In the absence of any likely means of 
dispersal, whether by currents or by birds, it is assumed that 
the inland species are derived from shore plants, originally brought 



xvi LITTORAL AND INLAND PLANTS' RELATIONSHIP 169 

by the currents, that have since disappeared, a view supported 
by the fact that Leguminosae are wanting in oceanic islands where 
there is no littoral flora. The second is the " Fijian difficulty " 
which is best represented by Pandanus. From our inability to 
regard the inland species as derivatives of the coast species, or to 
supply them with a means of dispersal, we are compelled to regard 
them either as having been a part of the original continental flora 
of Fiji or as owing their existence there to the agency of extinct 
birds having the habits of the Nicobar pigeon and of the extinct 
Columbae of the Mascarene Islands. Since the Mascarene Islands 
are noted not only for their extinct Columbae but also for their 
number of peculiar species of Pandanus, the implication seems 
to lie against the continental view. The subject, however, awaits 
further investigation. In the Western Pacific the possible agency 
of the parent forms of the existing species of Megapodidae is 
worthy of attention. Like the Columbae and Pandanus in the 
Mascarene Islands, the Megapodes and Pandanus have " differenti- 
ated " together in the Western Pacific. 

(9) The general view of the independent origin of the beach 
and inland floras of the Pacific islands is supported by the large 
number of genera in the strand flora that only possess littoral 
species. 

(10) Such shore species, together with other strand plants, 
sometimes extend into the interior of an island, but only as a rule 
where the requisite conditions for a plant of xerophilous habit 
exist. 

(n) Shore plants, it is pointed out, are xerophytes first and 
halophytes afterwards ; and under certain conditions the purely 
xerophilous inclination prevails and the plants travel far inland. 



CHAPTER XVII 

THE STORIES OF AFZELIA BIJUGA, ENTADA SCANDENS, AND 
(LESALPINIA BONDUCELLA 

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. Cassalpinia 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. 

IN this chapter we have a study of Leguminous strand plants that 
are of great interest. It can be safely said that the student of 
plant-dispersal in the Pacific will be brought into contact with the 
problems here involved wherever he goes. 



AFZELIA BIJUGA (Gray). 

This Old World tree, which belongs to the sub-family Caesal- 
piniae, is of great interest to the student of plant-dispersal. It is 
one of that large group of Indo-Malayan plants that extend into 
the Western Pacific, and give the prevailing character to the 
floras of such archipelagoes as that of Fiji. It is a large tree yielding 
a valuable timber used by the Fijians and Samoans for many 
purposes, such as for canoes, house-posts, clubs, kava bowls, &c., 
but it has not been recorded from the Tahitian region, and is 
unknown from Hawaii. In the fact of its being a littoral as well 
as an inland tree, it possesses a peculiar interest from the stand- 
point of plant-dispersal, and especially since this difference in 
station is associated with a difference in buoyancy, the seeds of the 



CH. xvn AFZELIA BIJUGA 171 

inland trees usually sinking, whilst those of the coast trees usually 
float, and often for a period of months. 

A glance at the distribution of the genus will enable us to 
appreciate some of the points that will be touched upon in the 
following discussion ; and it may he here remarked that the 
explanation of the distribution of these Leguminous trees will go 
far to make clear some of the most difficult points in plant- 
geography. Of the eleven species enumerated in the Index 
Kewensis, five belong to tropical Africa, occurring on both the 
east and west coasts as well as in the interior, three are confined 
to the mainland of tropical Asia, and two are peculiar to Malaya. 
In the last place we have the wide-ranging Afzelia bijuga, which, 
if it does not actually occur on the east coast of Africa, is found at 
all events in Madagascar and in the Seychelles, and is to be 
followed by the way of the Chagos Archipelago to the Malayan 
Islands and Queensland, and eastward to Fiji and Samoa. 

The most suggestive feature in the distribution of the genus is 
to be seen in the frequent station of the species by rivers. We 
learn from Oliver's Flora of Tropical Africa that these trees find a 
home along river-courses on both sides of the continent, as on the 
banks of the Congo, the Niger, the rivers of Senegambia, and the 
Zambesi, the Zambesi species being found also on the shores of 
Lake Nyassa. Since tropical Africa possesses about half of the 
species, it would seem highly probable that it is the home of the 
genus, and that from the rain-forests in the heart of the continent 
rivers flowing east and west have borne the buoyant seeds of the 
wandering species to the coasts of the Atlantic and Pacific Oceans. 
The operation that I witnessed on a miniature scale in the case 
of a species of Entada (E. scandens) in the Isthmus of Panama, as 
described in a later page of this chapter, has been in progress 
through the ages with the genus of Afzelia in the breadth of the 
African continent. According to the principle illustrated by 
Afzelia bijuga in the forests of Fiji, the seeds of the African forest- 
trees would, as a rule, possess no floating power ; but now and 
then in the lapse of long periods of time buoyancy in some species 
would be developed, and such species would ultimately, through 
their buoyant seeds, find their station along the lower courses of 
the rivers. 

To sustain this view it is not necessary that continuous rain- 
forests should now clothe the elevated regions in the interior of 
tropical Africa ; but it is requisite that there should be sometimes a 
generic similarity between the plants of the East African and West 



172 A NATURALIST IN THE PACIFIC CHAP. 

African rain-forests ; and it is evident that this is the case. Pechuel- 
Losche, as quoted by Schimper (Plant-Geography, p. 299), describes 
the rain-forest on the Loango coast as covering the mountain ranges 
and as extending to the river-plains. In such a locality the opera- 
tion would be rapid. In advancing this hypothesis I am referring 
to the possibility, however, of such an operation having effected the 
distribution of Afzelia in tropical Africa in the past rather than in 
the present. I would suggest that botanists in other habitats of 
the genus, as for instance in Queensland, might put it to the test 
of observation and experiment. 

The interest that attaches itself to the story of the genus in its 
African home may be extended to the species that forms its out- 
post in the Pacific, and we shall see there a littoral species that 
doubtless had its home in the interior of a continent endeavouring, 
with a considerable measure of success, to become again an inland 
plant. Home (p. 112), who was familiar with Afzelia bijuga at 
the two extremes of its range, namely, in the Mascarene Islands 
and in Fiji, speaks of it as characteristic of the shores of tropical 
regions ; and Schimper, who includes it in the Indo-Malayan 
strand-flora, implies that it is more or less exclusively confined to 
the coast and its immediate vicinity (pages 121, 191-2). In the 
Seychelles, according to Mr. Button, this tree attains gigantic 
dimensions on the sandy flats. Still larger trees occur in the 
coral islands of the Chagos Archipelago ; but in the atoll of 
Diego Garcia, as we learn from Mr. Bourne, it is almost extinct 
only some four or five trees existing there about twenty years 
ago, the increase of the tree being prevented through the de- 
struction of the fallen seeds by the rats {Journ. Linn. Soc. Bot., 
vol. 22, 1887). 

Afzelia bijuga may, therefore, be safely regarded as a littoral 
tree. We shall now see the importance of this conclusion when 
we come to consider its station in the Pacific islands, where it grows 
both inland and at the coast, and we have to decide to which 
station we must assign the priority. Speaking of its occurrence 
in Fiji, Dr. Seemann says it is "common in the forests all over 
Viti," but makes no allusion to it as a littoral tree either in Fiji 
or elsewhere. On the other hand, Mr. Home (p. 112) describes it 
as " generally growing on the shore or sandy beaches, and in 
rocky clefts, and by the sides of streams in the interior of Viti 
Levu and Vanua Levu." It was on or near the coast in Fiji that 
the present writer was most familiar with this tree, sometimes 
bordering the sandy beach, at other times growing behind the 



xvn AFZELIA BIJUGA 173 

mangrove- belt, or again thriving in the half sandy and half swampy 
soil of some low islet off the mouth of the Rewa. Especially is 
it to be found on those parts of the coast where the hill-slopes 
descend rapidly to the beach, or where some lofty spur from the 
mountains of the interior reaches the shore. It is also not un- 
common on the banks of rivers both in their lower and upper 
courses. But it is as a forest-tree of the interior that it is most 
valued by both the white men and the natives on account of the 
superior quality of its timber in that station. There, far removed 
from stream or river, the Vesi, as the Fijians name Afzelia bijuga, 
takes its place amongst the lofty forest-trees, such as the Ndamanu 
(Calophyllum), the Ndakua (Dammara), and the Wathi-wathi 
(Sterculia). It is not often that one finds a tree in these islands 
that, like the Vesi, is able to make its home in almost any station, 
excepting, however, the " talasinga " or " sun-burnt " regions of 
the plains. Wherever tall trees grow gregariously in Vanua Levu, 
one will probably find Afzelia bijuga, whether beside a sandy 
beach, or bordering a swamp, or on a river's bank, or on some 
rocky declivity, or on the great forest- clad mountain-slopes and 
plateaux of the interior. No doubt the same diversity of station 
is displayed in Samoa, where, according to Dr. Reinecke, the tree 
is most frequent in the " coast-bush." 

From the variety in station it might be expected that corre- 
sponding variations in character would be found. There are differ- 
ences, such as in the quality of the timber and in the size of the 
seeds between coast and inland trees ; but the most important dis- 
tinction in connection with the study of the dispersal of the species 
is to be found in the circumstance that whilst the seeds of the 
coast trees are, as a rule, buoyant, and often float for months, those of 
the inland trees usually sink, even after being kept for three or four 
years. I made a considerable number of experiments on the 
buoyancy of the seeds of this tree in Vanua Levu, and found that 
with the coast trees, as a rule, either all the seeds or the majority 
of them floated in sea-water, whilst with the inland trees either all 
of them or the majority of them sank. The buoyant seeds are 
able in most cases to float for a long time. Thus, in one experi- 
ment half were afloat after two months, and in another half were 
afloat after five months. It is probable that several of the excep- 
tions, where inland seeds float, will prove to be connected with an 
inland station by a river. (I experimented on eight sets of seeds 
of coast trees from eight different localities, and found 70 to be the 
mean percentage of buoyant seeds. In the same way, four sets of 



174 A NATURALIST IN THE PACIFIC CHAP. 

seeds from four different inland localities gave 13 as the mean per- 
centage of buoyant seeds.) 

As in the case of Entada scandens, there is a rather fine adjust- 
ment between the mean specific weight of seeds and the density 
of water. If we place a number of the buoyant seeds in sea-water 
and begin to lower the density, some of the seeds will at once 
commence to float heavily and afterwards sink ; and when the 
density has been lowered to approximately that of fresh water, 
usually about a third will be found at the bottom of the vessel. 
Out of 100 coast seeds, 70 will, as a rule, float in the sea and about 
47 in the river ; whilst of the same number of inland seeds, 13 on 
the average will float in sea-water and 8 or 9 in fresh water. The 
bearing of facts of this kind is especially discussed in Chapter X. 

Coming to the causes of the floating-power of the seeds, we find 
that with the buoyant seeds the kernel floats, whilst with the non- 
buoyant seeds it sinks, the seed-tests in neither case possessing any 
floating-power. In this respect, therefore, the seeds of Afzelia 
bijuga belong, with the seeds of some other Leguminous littoral 
plants of the Pacific islands, such as Canavalia obtusifolia, Eryth- 
rina indica, and Sophora tomentosa, to the second section of the 
second non-adaptive group of buoyant seeds (page 107). 
But though we can in a measure explain the cause of the 
buoyancy, we are still ignorant of the manner in which the differ- 
ence in the buoyant behaviour of coast and inland seeds has been 
brought about. It is possible that this may be connected with 
another difference between the coast and inland seeds, the latter 
being markedly smaller, and it is noteworthy that in my experi- 
ments the smaller seeds were generally those that sank. (Whilst 
the inland seeds averaged between f^ and I inch, or 20 to 25 mm., 
in greatest diameter, 12 to 16 being required to make an ounce, 
the coast seeds measured I to ly 2 ^ inch, or 25 to 30 mm., and only 
10 or ii were needed to weigh an ounce.) 

There can be no question that the seeds are at times trans- 
ported by the currents over wide tracts of sea, and this no doubt 
explains the occurrence of Afzelia bijuga in oceanic islands. They 
may be usually seen lying free in numbers on the ground beneath 
the tree or else still inclosed in the fallen dehiscing and decaying 
pods ; and they might be swept sometimes into the sea or washed 
down into an adjacent stream. They thus came under my notice 
amongst the stranded beach drift at the mouths of estuaries in Fiji. 
But it is remarkable that the seeds have not apparently been 
recorded from the beach drift of other tropical regions. Penzig 



xvn AFZELIA BIJUGA 175 

does not note them amongst the seeds stranded on the shores 
of Krakatoa. They did not occur amongst my collections from 
the beaches of Keeling Atoll or of the south coast of Java ; nor 
does Schimper mention them amongst the drift of the Java Sea. In 
the Botany of the " Challenger " Expedition the species is not even 
referred to in any connection. Although, however, the capacity of 
these seeds for dispersal by currents is for the first time established 
by me, their fitness in this respect was surmised by Schimper 
(p. 191), when he placed the species in his list of tropical shore 
plants evidently distributed by the currents. 

It will thus be gathered that we have yet much to learn in this 
matter ; and I would recommend any resident in the tropics to 
take up this subject. When indeed we remember the fine adjust- 
ment existing between the specific weight of the seeds and the 
density of water, and recall the unknown factor determining the 
difference in buoyancy between the kernels of coast and inland 
seeds, we can understand how under particular conditions in certain 
portions of its range the seeds of Afzelia bijuga may perhaps never 
possess any floating power. It would seem, in fact, that the seeds 
are much more buoyant in the Western Pacific than they are in the 
Java Sea ; or it may be that the tree is much less frequent ; or that 
the stranded seeds are soon destroyed by crabs, such as is the fate 
of much seed-drift on the Keeling beaches ; or lastly that, as in 
Diego Garcia, rats in destroying the fallen seeds are bringing about 
the extermination of the species. 



Summary relating to Afzelia bijuga. 

(1) Assuming that the genus has its home in the African 
continent, and that the species have frequently a riverside station, 
it is argued that the distribution of the genus on both sides of that 
continent can only be explained by its dispersal by rivers from a 
centre in the interior. 

(2) Afzelia bijuga, a widely distributed shore tree of tropical 
Asia, occurs in Fiji both at the coast and in the inland forests. 

(3) This double station is associated inter alia with a 
different buoyant behaviour of the seeds, those of the coast trees 
usually floating for long periods, whilst those from inland generally 
sink. 

(4) There can be no doubt that this widely ranging littoral tree 
has been dispersed by the currents ; but the specific weight of the 



J y6 A NATURALIST IN THE PACIFIC CHAP. 

coast seeds is on the average but slightly less than that of sea- 
water ; and it is to this fine adjustment, always liable to be 
disturbed by variations in the environment, that the irregularities 
in the distribution of the species are to be attributed. 



ENTADA SCANDENS (Benth.). 

The story of Entada scandens, a plant familiar to many of my 
readers under the name of the Queensland Bean, is a story of three 
continents, Africa, Asia, and America. From the point of view of 
its dispersal two features at once attract attention in the case 
of this giant-climber ; in the first place its wide distribution over the 
tropics of the Old and New Worlds, and in the second place the 
great capacity of its large seeds, often two inches across, for dis- 
persal by the currents. But before discussing these matters it will 
be necessary to glance at the distribution of the genus, since much 
light will thereby be thrown on some of the numerous difficult 
points affecting this extremely interesting tropical plant. Of the 
thirteen species enumerated in the Index Kewensis^ seven are 
African, three are American, one is Burmese, one hails from 
Madagascar, and, lastly, there is the world-ranging Entada scandens, 
concerning whose home botanists are not agreed. Most of the 
species would seem to be inland plants, whilst Entada scandens 
thrives both inland and at the coast. Africa would thus appear to 
be, as with Afzelia, the principal home of the genus, but with 
America as a subsidiary centre. 

In many points Entada scandens presents a parallel to Caesal- 
pinia bonducella, another Leguminous tropical plant which occurs 
also at the coast and inland. But since they both owe their wide 
distribution to their littoral station, it will be as coast plants that 
they will be most properly considered in this and the following 
chapter. Yet if the student were to regard the distribution of 
these two plants in a continental region as in India, where they 
extend inland to the Himalayas, he might fail to discern their true 
station. To accurately gauge the matter of their station, it is 
necessary for him to look at the plants as they occur in the islands 
of the Pacific. There he will first see the stranding of the seeds on 
a shore by the currents, then their germination and their develop- 
ment into giant-climbers over the littoral trees or into straggling 
bushes on the beach ; and afterwards he will observe the plants of 
both species extending inland, and in these three stages he will 



xvn ENTATA SCANDENS 177 

learn their history in the Pacific ; but a history, it may be observed, 
that in this region represents their efforts to return to an inland 
station, such as they once possessed in their birthplace in some 
distant region of the globe. 

Dealing first with the station of Entada scandens, it may be 
remarked, as Dr. Seemann points out, that in Fiji it is most 
characteristic of the mangrove-formation. But it also occurs 
amongst the trees at the back of the mangrove swamp, on the 
beaches, on the banks of the estuaries, and at the edge of the 
inland forests where they border on the plains. Sometimes in the 
company of Derris uliginosa it grows not as a climber, but as a 
prostrate plant on the sandy beaches ; and here, not being able to 
assume its normal habit of a climber, it does not seed. It is to be 
found at times far inland in open-wooded districts. Thus in Vanua 
Levu I found it growing in the Mbua district four miles inland, and 
1,400 feet above the sea. Reinecke speaks of it in Samoa only in 
connection with the " urwald," or primeval forest. Cheeseman 
describes it as most abundant in the interior of Rarotonga, cover- 
ing the trees with a wide-spreading canopy of green. In the 
Malayan region Schirnper refers to it as a plant of the beach-tree 
formation. In Ecuador and on the Panama Isthmus it grows not 
only at the coast, but also on the hill-slopes in the rear of the 
mangrove-belt. 

With reference to the distribution of the plant, it may be 
remarked that, although it is found all round the tropics and 
possesses great capacity for dispersal by currents, there are certain 
difficulties in explaining its wide area and in accounting for its 
very peculiar distribution in the Pacific islands. It was doubtless 
in allusion to some of these difficulties that Mr. Darwin, in a letter 
to Sir Joseph Hooker, remarked : " Entada is a beast " (More 
Letters, &c., i, 93). There is at first the question of the identity 
of the species in the Old and New Worlds. It is here assumed 
that it is the same in both hemispheres ; but it must not be 
forgotten that the identity is "not beyond doubt" (Bot. Chall. 
Exped. iv, 147). 

Then there is the difficulty connected with its occurrence on 
both coasts of tropical America. In this respect it is at one 
with some other littoral plants, like Ipomea pes caprae, as well as 
with the plants of the mangrove formation, as is pointed out in 
Chapter VIII. Whilst with the mangroves it is necessary to 
assume that they antedate the land connection between North and 
South America, this is not requisite in the case of Entada scandens, 
VOL. II N 



178 A NATURALIST IN THE PACIFIC CHAP. 

since it grows in the interior of the Panama Isthmus, and rivers on 
the north and south sides now carry its seeds seaward from the 
same "divide" to the Atlantic and Pacific Oceans, as described in 
Chapter XXXII. 

But, as I have also shown in Chapter VIII, America forms with 
the West Coast of Africa a region characterised by the same 
tropical littoral flora. This region, on account of the arrangement 
of the currents, stands in a very peculiar relation with the Asiatic 
region, which comprises the rest of the tropics, and to a great extent 
possesses its own peculiar strand-flora. There are a few littoral 
plants, like Entada scandens, Canavalia obtustfolia, Sophora tomen- 
tosa, and Ipomea pes caprse that occur in both areas ; but the 
large majority are confined to one or other of them, either to 
the American region, including the African West Coast, or to the 
Old World region, which includes the African East Coast. The 
American region gives to the Old World, but it can receive nothing 
in return. For this reason, it is argued, we are compelled to regard 
most, if not all, of the cosmopolitan tropical shore plants that are 
dispersed by the currents, such as those above named, as having 
their home jn the American region. Entada scandens would, there- 
fore, from this standpoint have its home in America. 

Then, again, there is the difficulty connected with the distribu- 
tion of this plant on both sides of tropical Africa. Though Oliver 
in his Flora of Tropical Africa mentions this species only in 
connection with the West Coast, he says it is probably widely 
spread in that continent, and he refers to a pod in the Kew 
Museum indistinctly labelled "Lake Ngami." I have not come 
upon any reference to its being a littoral plant on the East Coast, 
but since numerous littoral plants of tropical Asia are found on 
that coast its occurrence there or in the East African islands would 
be expected. However, as the genus has a centre in America, and 
as this species is regarded as of American birth, we are not called 
upon to employ the argument used in assigning to a non-American, 
genus like Afzelia an African home. Since the African West 
Coast belongs to the American region of tropical shore plants 
dispersed by the currents, the presence of Entada scandens on that 
coast of Africa can be readily explained, whilst if it has reached 
the Malayan Archipelago from America by way of the Pacific, it 
would, by extending like many other Malayan coast-plants along 
the shores of the Indian Ocean, almost complete its circuit of the 
globe. It is in this fashion, I believe, that the other littoral plants,, 
like Caesalpinia bonducella, Canavalia obtusifolia, and Ipomea pes. 



xvn ENTADA SCANDENS 179 

caprae, that are found all round the tropics, have performed the 
circuit of the globe with America as their home. 

One may remark in passing that the double home of the genus 
in America and the Old World, though offering a serious difficulty 
in plant geography, has no immediate bearing on the present mode 
of distribution of Entada scandens. Questions relating to the dis- 
tribution of tropical shore-plants that are dispersed by the currents 
at first resolve themselves into considerations of the arrangement 
of the currents. Entada is not alone amongst the genera contain- 
ing littoral species in having a home both in the Old and in the 
New World. Carapa is another instance, and additional cases 
might be cited. 

The next peculiarity in the geographical range of this species is 
concerned with its irregular distribution in the archipelagoes of the 
tropical Pacific. Notwithstanding its great capacity for dispersal 
by the currents, although it occurs in all the groups of the Western 
Pacific as well as in the Cook Islands, it has not been recorded 
from the Society Islands, the Paumotus, the Marquesas, and 
Hawaii. Since, however, its seeds have been gathered by 
Mr. Arundel on the beaches of Flint Island, lying about six 
degrees north of Tahiti (Bot. ChalL iv, 302), it is not unlikely that 
it will be found growing in other parts of Eastern Polynesia south 
of the equator. One might have looked for an explanation of its 
rarity in Eastern Polynesia to the absence of mangrove swamps, in 
which, as in Fiji, it is sometimes most at home ; but this is nega- 
tived by its abundance in Rarotonga, where mangrove swamps do 
not exist. 

The dispersal of Entada scandens by the currents. This 
plant offers one of the most conspicuous examples of the transport 
of seeds across oceans through the agency of the currents. In the 
pages of many botanical works, from the close of the 1 7th century 
onward, reference is made to the transport of its beans (often in 
association with those of Mucuna urens and Caesalpinia bondu- 
cella) by the Gulf Stream or other currents across the Atlantic to 
St. Helena, the Azores, the west coast of Ireland, the Hebrides, the 
Orkney Islands, the coasts of Scandinavia, and even as far north as 
Nova Zembla (see Hemsley's Bot. Chall. Exped. ; Sernander's 
Skand. Veg. Spridningsbiologi, &c.). That the seeds of Entada 
scandens retain their germinating capacity after this ocean-trans- 
port has been demonstrated not only by the germination of 
stranded seeds on the shores of St. Helena, but also by the 
germination when sown at Kew of seeds drifted to the Azores, as 

N 2 



i8o A NATURALIST IN THE PACIFIC CHAP.' 

well as by the results obtained by Lindman, who procured the 
germination of the seeds of this plant and of Mucuna urens that 
had been washed up on the Scandinavian beaches (see Sernander, 

PP- 7, 390). 

One of the most interesting references to the conveyance by 
currents of these seeds to the coasts of Europe is to be found 
in Dr. Sernander's recent work on the modes of dispersal of 
the Scandinavian flora, where he sums up the results of Lindman's 
investigations respecting the Gulf Stream drift. The stranded 
seeds of Entada scandens, it appears, have been found all along the 
Norwegian coast, but occur most frequently north of the Sondmore 
district. They have even been found in a sub-fossil condition in 
the peat-bogs of Tjorn on the Bohuslan coast in Sweden, having 
been originally stranded on a beach in that locality at some 
distant, but post-glacial, epoch. Few phenomena in plant-distribu- 
tion are more suggestive than this ineffectual transport through the 
ages of these large tropical beans to coasts within the Arctic 
Circle. The seed, no longer under the care of the mother-plant, 
becomes a waif, exposed to the pitiless laws of the physical world 
which here prevail. It was not thus that the plant was reared, but 
it is in this haphazard fashion that its seeds are spread. The 
philosopher could unravel most of the tangled problems connected 
with present and past plant-dispersal, if he could follow the clue 
supplied by this stranded tropical seed on a Scandinavian 
beach. 

It is a far jump from the North Cape to the coral islands of the 
Pacific and Indian Oceans ; yet it is within the area covered by the 
drifting Entada bean. The stranded seeds occur commonly on the 
Fijian beaches and on other islands of the South Pacific ; but 
I never found them in Hawaii. They were gathered by me on the 
shores of Keeling Atoll in the Indian Ocean, and on the south 
coast of Java. Penzig found on the Krakatoa beaches, in 1897, 
not only the stranded seed but the established plant. They came 
under my notice in numbers on the beaches of Ecuador and on the 
Pacific and Atlantic coasts of the Panama Isthmus ; and, as I 
learned, they are equally common on the other parts of the coasts 
of Central America. Not uncommonly these stranded seeds in 
various parts of the world are to be found incrusted with 
polyzoa and tubicular annelids, which afford proof of prolonged 
flotation in the sea. These seeds are also to be frequently noticed 
floating in the drift of the tropical estuaries. Thus they came 
under my observation afloat in numbers in the Fijian estuaries, in 



xvn ENTADA SCANDENS 181 

the Guayaquil river, in the estuary of the Chagres at Colon, and in 
the mouth of a river on the Panama side of the isthmus. 

The mode of liberation of the seeds is worthy of a passing 
remark. The huge pods, often several feet in length, ultimately 
break up into separate joints bearing the seeds. The joints may 
decay on the ground, and the seeds are thus freed ; or not infre- 
quently in a mangrove-swamp they fall at once into the water, and 
there they float, as may often be observed in Fijian rivers, until 
their decay sets free the seed. 

The seeds of Entada scandens are often quoted, and justly so, 
as striking examples of the dispersal of seeds by currents. Yet in 
few plants could the nature or the structural cause of the buoyancy 
have so little claim to be considered as adaptive in its character. 
Quite half, and sometimes even the majority, of the seeds freshly 
liberated from the plant have no buoyancy at all. The mean 
specific weight of the seed is about that of sea-water, but markedly 
higher than that of fresh water ; whilst the principal determining 
cause of the buoyancy is, as shown below, purely mechanical, and 
one that, whilst favouring the wide distribution of the species, could 
not be improved by or come within the scope of Natural Selection. 

From experiments made in Fiji and Ecuador, it appears that at 
least 50 per cent., and often more than half, of the seeds when first 
liberated from the pod have no buoyancy in sea-water. Of those 
that float in sea-water, a proportion varying between one-third and 
one-half sink in fresh water, so that in the case of plants growing 
on the banks of a river only about one-fourth or one-third would 
be carried down to the sea. So fine is the adjustment of the 
specific weight of these seeds to the density of water, a subject 
discussed in its general bearings in Chapter X, that if one gathers 
a number of drift seeds on a beach, let it be in Fiji or in Ecuador, 
although, of course, all will float in the sea, only one-half or two- 
thirds will float in the neighbouring fresh-water stream. Those 
that float appear to be able to float almost indefinitely. This is 
sufficiently established by the transport of the seeds in a sound 
condition by the currents across the Atlantic, and by such evidence 
as the stranding of seeds incrusted with polyzoa and serpulae on 
the beaches of Keeling Atoll. It has been also proved by the 
following experiment. Several years since, I placed a seed in a 
vessel of sea-water, where it still floated buoyantly in a perfectly 
sound condition twelve months afterwards. 

With regard to the cause of the buoyancy, investigation shows 
that neither the seed tests nor the seed contents have any floating 



i82 A NATURALIST IN THE PACIFIC CHAP. 

power, the buoyancy arising from a large central cavity produced 
by the shrinking and bending outward of the cotyledons during the 
drying and hardening of the maturing seed (see figure in 
Chapter XII). With the seeds that sink, this cavity is, as a rule, 
reduced to small dimensions, and may be represented only by a 
narrow slit. In some cases, however, where the cotyledons are un- 
usually thick and heavy, even a large central cavity will not give 
floating power to the seed. There is an indication in my experi- 
ments that seeds from inland plants that have matured their pods 
in the forests sink in a much greater proportion than seeds of coast 
plants, or of those growing on the banks of estuaries. This we 
might expect, since in the shade of the forests the drying process 
that accompanies the setting and final maturation of the seed would 
be less complete and the intercotyledonary cavity smaller than with 
the seeds matured in more exposed situations. This is a point, 
however, that requires further investigation. 

It will thus be seen that in respect of buoyancy the seeds of 
Entada scandens are to be referred to the mechanical or non- 
adaptive group of buoyant seeds, described in Chapter XII, which 
comprises several other Leguminous strand-plants, including 
Csesalpinia bonducella. I especially studied the various stages in 
the development of the buoyancy of seeds in this mechanical group 
in the case of the species of Csesalpinia just named, and the 
description of the process as given under that plant will apply 
to all. 

Summary relating to Entada scandens 

(1) This plant, which has been distributed by the currents over 
the tropics of the globe, has its station in the mangrove swamp, on 
the beach, by the estuary, and in the inland forest. 

(2) It is regarded as an American plant that has reached the 
shores of the Indian Ocean by crossing the Pacific, and the coast 
of West Africa by crossing the Atlantic. 

(3) Its occurrence on both coasts of America is attributed to 
its having a focus of dispersal in the forests of Central America, 
from which its seeds have been transported by the rivers to the 
shores of the Atlantic and Pacific Oceans. 

(4) Its irregular distribution in the Pacific islands, to wit, its 
absence from Hawaii and its rarity in the Tahitian region, is not to 
be easily explained, but it is more than likely that it will be sub- 
sequently recorded from other localities in Eastern Polynesia. 



xvn OESALPINIA 183 

(5) Although the seeds offer a striking example of dispersal by 
currents, since they are to be found stranded on beaches over much 
of the globe, from within the Arctic Circle to the Coral Sea, in few 
plants could the character of the buoyancy and the structure 
connected with it have so little claim to be considered as adaptive 
in their nature. At least 50 per cent, of the seeds sink in sea-water, 
and the cause of the buoyancy of the other seeds is only to be 
connected with the large size of a cavity produced by the shrinking 
of the embryo within the seed tests during maturation. 



CESALPINIA 

This genus is represented in the tropics of both the Old and 
the New World by some eighty species of trees, shrubs, and 
climbers, some of which are noted for their dye-woods, and others 
for the beauty of their flowers. In the Pacific islands the botanist 
is only concerned with three widely distributed species, all more or 
less littoral in their station, and in great part dispersed by the 
currents, namely, Caesalpinia nuga (Ait), C. bonducella (Flem.), and 
C. bonduc (Roxb.). 

With Caesalpinia nuga we have little to do, since, although 
widely distributed in tropical Asia and the Malayan region, and 
reaching to both New Guinea and North Australia, it has not 
apparently penetrated into the Pacific further east than the Solomon 
and New Hebrides groups. I found it growing on the coasts of 
the larger islands of the Solomon group, but no observations were 
made on its mode of dispersal. However, as its seeds were 
identified at Kew (Bot. ChalL Exped. iv, 311) amongst my 
collections of stranded drift from those islands, it would appear to 
be to some degree dispersed by the currents, though since it does 
not extend far into the Pacific, its capacity for dispersal by this 
agency would seem to be limited. Schimper includes it among 
the strand-plants of the Indo-Malayan region. 

It is with the other two species, Caesalpinia bonducella and 
C. bonduc that we are especially interested. Their extremely hard, 
marble-like seeds at once attract attention, and when pale in colour 
they look not unlike quartz pebbles as they lie stranded on a beach. 
The prickly pods and the recurved prickles of the leaf-branches 
often make these plants provokingly evident to a stranger. 
Though usually to be characterised when growing on a beach as 
straggling shrubs, they will often climb trees when opportunities 



1 84 A NATURALIST IN THE PACIFIC CHAP. 

occur, and they then display themselves as stout-stemmed climbers. 
I have seen one or other of them in the mangrove swamps of Fiji 
ascending the Bruguiera trees to a height of 30 feet and more, the 
stem quite bare below, but leafing and flowering in the tree-branches 
above. 

From the standpoint of dispersal there are few more interesting 
plants in the Pacific islands ; but their discussion raises several 
difficult questions, and it will be, therefore, requisite to treat them 
somewhat in detail. With regard first to the diagnostic characters 
between the species, it may be observed that, as a rule, they are 
sufficiently evident, such, for instance, as the number, size, and 
form of the leaflets, the presence or absence of foliaceous stipules, 
and the colour of the seeds, though, as shown below, the seed- 
colour in the case of Fijian plants does not always present a 
constant distinction. Yet as I found in Fiji the difference between 
the two species is not in all cases well pronounced, and inter- 
mediate forms occur, about which it is sometimes difficult to 
decide to which of the two species they should be assigned. 

Mr. Hemsley remarks (Bot. ChalL Exped. iii, 114, 145, 300) that 
the two species have been often confused. I venture to think that 
this has been in some cases due to the occurrence of these 
intermediate forms. One has only to look at the different 
" distributions " given by botanists for C. bonduc, as indicated 
below, in order to suspect that the cause of confusion has been at 
times with the plants themselves. When in Fiji I paid a good 
deal of attention to this subject, and the results of the comparison 
of the foliage and seeds of the plants obtained from fourteen 
different localities in Vanua Levu are given below. 

It will be seen in this table that I distinguish in Fiji three 
littoral forms and one inland or mountain variety, which may 
perhaps be a distinct species. Those of the strand include 
Csesalpinia bonducella, C. bonduc, and an intermediate form. 
C. bonduc is typically distinguished by its large leaflets, by the 
absence of foliaceous stipules, and by its pale yellow seeds ; whilst 
C. bonducella is similarly characterised by its small leaflets, its 
foliaceous stipules, and its lead-coloured or darkish grey seeds. 
But in the first species the colour of the seeds may often be yellow 
mixed with pale-grey, or almost white ; whilst in the second 
species the seeds may be stained with brownish-yellow patches. 

It seemed to me when examining fresh specimens in Hawaii 
and Fiji that the ultimate colour of the seed is a good deal 
determined by the degree of alteration of the original olive-green 



XVII 



C^SALPINIA 



185 



colour of the immature seed. All gradations may be noticed 
from the olive-green of immaturity to the yellow, pale grey, and 
dirty white hues of the mature seeds of Caesalpinia bonduc and to 
the lead or slate-colour of those of C. bonducella. It almost 
appeared as if the changes might be compared to the bleaching 
which a dark volcanic rock undergoes in the weathering process 
through the hydration and removal of the iron oxides. 

C/ESALPINIA IN FIJI, TAHITI, AND HAWAII. 











Leaflets. 


Seeds. 


Locality. 


Species. 


Folia- 
ceous 
stipules. 


Pairs 
of 
pinnae. 


Pairs. 


Length 
in 


Form. 


Size in 
tenths 

_r 


Colour. 












inches. 




OI 

inch. 




/ 


Bonducella 


Present 


8-9 


9-1 1 


.1-.} 


Oblong, obtuse 
mucronate : base 


fltoi 


Usually lead- 
colour with at 














rounded and in- 




times brownish- 














equilateral 




yellow patches. 


Coast, < 


Bonduc 


Absent 


5-6 


4-6 


2^-5 


Oblong, acumi- 


5i-6 


Pale yellow 


Fiji 












nate, mucronate, 


















base rounded or 


6i~7i 


Pale grey, some- 














subcordate 




times mixed 


















with yellow. 


V 


Intermediate 


Present 


7-8 


7-9 


2-3 


Oblong, obtuse 


6-7 


Lead-colour or 














mucronate, round- 
ed at base ; upper 
leaflets may be 




pale grey with 
brownish-yellow 
patches 














elliptical 






Inland, 


Mountain 


Present 


5-6 


9-10 


li-2| 


Lanceolate with 


6 


Yellowish or pale 


Fiji 


species 










long tapering 




grey or mixed. 














aristate apex 


















and rounded 


















base 






Coast, 


Bonducella 


Present 






i-i| 


Oblong 






Tahiti 


















Inland, 
Tahiti 


Bonduc 


Absent 




5-6 




Oblong 






Inland, 


Bonducella 




4-6 


6-8 


lt-2 


Oblong, obtuse, 


6-7 


Lead-colour. 


Hawaii 












not cordate at 


















base 







Note. The characters of the Fijian plants are from my own observations. Drake del 
Castillo is quoted for Tahiti, and Hillebrand for Hawaii. Reinecke observes that 
the pods of C. bonducella in the inland forests have no prickles. 

In Fiji all three coast forms may be found on the same beach, 
or they may exist apart. The large-leaved species (C. bonduc) 
appears to be much the most frequent in Vanua Levu ; and the 
intermediate form is common enough to disturb the serenity 
of the observer's mind when he is anxious to diagnose 
rather than to collect cumbersome specimens. The mountain 
form, which came under my notice as a climber in the forest at an 



1 86 A NATURALIST IN THE PACIFIC CHAP. 

elevation of 1,700 feet on the slopes of Koro-mbasanga in Vanua 
Levu, acquires from the lanceolate shape of its leaflets quite a 
character of its own, though it comes nearest to Csesalpinia bondu- 
cella. Mountain forms also occur, as indicated in a later page, in the 
forests of Samoa and in Tahiti ; but in the first-named group they 
are referred by Reinecke to C. bonducella, and in Tahiti by Drake 
del Castillo to C. bonduc. In the Samoan forests the inland 
plants possess pods deprived of the prickles that are so character- 
istic of the beach plants. Before one can pronounce definitely on 
the relation between the coast and inland forms in any of the 
groups, a thorough investigation of the connections between the 
two shore-species is needed. I am inclined to think that they will 
prove to belong to a single dimorphic (or perhaps polymorphic) 
species. 

The distribution of Ccesalpinia bonducella andC. bonduc. Botanists 
agree in giving C. bonducella a distribution around the tropics of 
the globe ; but they are not at all unanimous with respect to the 
other species. According to Mr. Hemsley this species is by no 
means so universally dispersed as C. bonducella. It is unknown 
from Africa and Australia ; but it is generally characteristic of 
tropical Asia and the Malay Archipelago. The same authority 
alludes to specimens in the Kew Herbarium from Florida and the 
West Indies (Bot. Chall. iv, 300). Drake del Castillo gives both 
species a range through the tropics, whilst Schimper seems in 
doubt about the occurrence of C. bonduc in the New World, and 
Mr. Burkill makes no allusion to its American habitat in his paper 
on the Tongan flora. The cause of this confusion is doubtless to 
be mainly attributed to the variation in characters of the plants, 
and to the occurrence of intermediate forms. 

We should be scarcely consistent if we assumed that of two 
kindred shore-species dispersed by the currents one had its home 
in America and the other in the Old World. The same home 
must belong to both. According to the principle laid down in 
Chapter VIII, and referred to under Entada scandens, it is held 
that a strand-plant, with its home in Asia, on account of the arrange- 
ment of the currents could never reach the American continent, 
and that American shore-plants are for the most part native-born 
except those hailing from the African West Coast, which, however, 
lies within the American province of tropical strand-plants. From 
this standpoint Caesalpinia bonducella would be regarded as now 
having its home in the New World, and since it is found on both 
the Pacific and Atlantic coasts of that continent (as well as on 



xvii OESALPINIA 187 

both coasts of Africa), it is assumed, as with Entada scandens, that 
it has reached the African West Coast by crossing the Atlantic, 
and the African East Coast by way of the Pacific and Indian 
Oceans. The genus, I may remark, is distributed over the tropics 
of the eastern and western hemispheres. 

As regards the general distribution of the two species in the 
Pacific islands, it would appear from the writings of Seemann, 
Hillebrand, Hemsley, Drake del Castillo, Reinecke, Cheeseman, 
and Burkill that with the exception of Hawaii and Samoa, where 
Caesalpinia bonducella alone occurs, and of Rarotonga where C. 
bonduc alone is found, they are generally associated in the larger 
groups, as in Fiji, Tonga, Tahiti, and the Marquesas. 

The station of C&salpinia bonducella and C. bonduc. Both the 
species are to be regarded as littoral plants likely to stray inland. 
The first-named is described in the Botany of the " Challenger " 
Expedition as essentially a sea-side plant, though flourishing 
equally well inland, and in India extending to the Himalayas as 
far as Kumaon, and up to elevations of 2,500 feet. Schimper 
speaks of both species as characteristic of the Indo-Malayan 
strand-flora, and he quotes Kurz when referring to C. bonduc as a 
constituent of the beach-jungle of Pegu. 

In the Pacific islands they are typically littoral in their station ; 
but they may extend inland, and in one or two groups they are 
only known in their inland station. Dr. Seemann speaks of both 
species only in connection with the beaches in Fiji, and alludes to 
Caesalpinia bonducella (p. 72) as sometimes climbing over the 
mangroves. In Vanua Levu both came under my notice on the 
beaches, and in their immediate vicinity, usually as straggling bushes, 
whilst at times they were to be observed climbing the mangroves at 
the borders of the adjacent swamp. In this island of the Fijis they 
do not, as a rule, stray far from the beach, and strange to say are 
not to be ranked amongst those seashore plants that frequent the 
" talasinga " regions or inland plains. Judging from the mountain 
form found in the forests of Koro-mbasanga, if they extend inland 
in Fiji they prefer the forests and become differentiated in character. 
In Tahiti, as we learn from Nadeaud and Drake del Castillo, 
C. bonducella occurs on the beach and extends inland to the 
mouths of the valleys ; whilst C. bonduc is only recorded from the 
mountains at elevations of 600 to 700 metres (2,000 to 2,300 
feet). Jouan is quoted by Mr. Hemsley as remarking that C. 
bonduc is as common in the Marquesas as brambles are in Europe 
(Bot. Chall. Exped. iii, 145)- In Rarotonga, according to Cheeseman, 



1 88 A NATURALIST IN THE PACIFIC CHAP. 

C. bonduc is restricted to the interior. In Samoa, as we are in- 
formed by Reinecke, C. bonducella is frequent both in the coast 
districts and in the mountain-forests. In the Samoan mountains 
the pods lose their prickles, and from this circumstance, as well as 
from the extremely widespread distribution of the species over the 
islands, the German botanist concludes that the plant has been for 
ages established in the group. 

In Hawaii, Caesalpinia bonducella, which alone occurs, rarely 
figures as a beach plant ; but it is found, as Hillebrand observes, in 
the lower plains of all the islands. In the large island of Hawaii 
I found it not on the scanty beaches of the coast, but on the 
partly vegetated surface of the old lava-flows at distances varying 
usually between a hundred yards and a mile from the sea, but 
extending at times a few miles inland, and in one locality reaching 
an elevation of 2,000 feet above the sea. It was mostly observed 
by me on the dry side of the island, where, associated with Erythrina 
monosperma, the Cactus, and the Castor-Oil plant, it thrives in 
very arid localities, where the rainfall is only a few inches in the 
year. Farther inland, where the old lava-surfaces were more 
vegetated, it was associated with such shrubs as Osteomeles 
anthyllidifolia and Cyathodes tameiameiae. Dr. Hillebrand, writing 
of a generation and more ago, says that in his time the plant was 
less common than formerly. 

The Methods of Dispersal of Cczsalpinia bonducella and C. bonduc. 
We come now to the modes of dispersal of these plants ; and in 
so doing we have to choose between the agencies of birds and of 
currents. The seeds of C. bonducella are on the average T V of an 
inch (18 mm.) in diameter, whilst those of C. bonduc are rather 
smaller ($ of an inch or 15 mm.). As far as their size and 
character go, it would seem scarcely likely that birds could trans- 
port these seeds across an ocean ; but our knowledge of the 
agency of birds is of a very imperfect nature. Yet their occasional 
dispersal by birds is not improbable. When I was in the Keeling 
Islands the residents informed me that the seeds of C. bonducella 
are sometimes found in the stomachs of sea-birds, such as frigate- 
birds and boobies. (See Note 59.) 

However, it has long been known that the seeds of one or both 
of these species are carried great distances by the currents ; but it 
is to be gathered that the older botanists, in alluding to this fact, 
more usually referred under the synonym of Guilandina bonduc 
to Caesalpinia bonducella. De Candolle, loth to attach much 
importance to the effective transport of seeds by currents, was 



xvn C^ESALPINIA 189 

compelled to admit this species in his scanty list of current- 
dispersed plants (see Note 33). For more than two centuries it 
has been known that the seeds of C. bonducella are carried in the 
Gulf Stream drift to the coast of Europe from the American side 
of the Atlantic ; and ever since they were recorded by Sloane in 
1696 as stranded in a fresh condition on the beaches of the Orkney 
Islands, they have been found washed up on other localities, as on 
the coasts of Ireland and of Scandinavia and on the shores of the 
islands of the Western Atlantic. According to Robert Brown, a 
plant was raised from a seed cast up on the west coast of Ireland ; 
and with respect to Scandinavia, Dr. Sernander informs us that 
the seeds of Csesalpinia bonducella, like those of Entada scandens 
and of Mucuna urens, are of frequent occurrence amongst the " Gulf 
Stream products " stranded on the Norwegian coasts. The seeds 
of this species are commonly washed ashore at St. Helena, and 
there are specimens in the Kew Museum that were stranded on 
Tristan da Cunha. (Those interested in the subject will find it 
discussed by Mr. Hemsley in the Botany of the " Challenger" 
Expedition, and also by Dr. Sernander in his recent work on 
Scandinavia.) 

The seeds of Csesalpinia bonducella have been also found stranded 
on beaches in other parts of the world. Thus Prof. Schimper found 
them in the beach-drift of the south coast of Java. Prof. Penzig 
noticed them amongst the stranded seeds of the Krakatoa beaches ; 
but it does not appear that the plant had established itself up to 
the date of his visit in 1897, or fourteen years after the great 
eruption. They have been picked up on the other side of the 
Indian Ocean on the east shores of Africa (Bot. Chall. Exped. iv, 300). 
They came frequently under my notice stranded on the beaches of 
Keeling Atoll in the same ocean ; and seedlings sprouting from 
the seeds were sometimes to be seen growing amongst the drift 
just above the high-tide level. The seeds of both C. bonducella 
and C. bonduc have been found also on the shores of Jamaica. 
Those of both species are not uncommon amongst the stranded 
drift of the Fijian beaches ; but notwithstanding a careful search 
I found only a solitary seed of C. bonducella in the Hawaiian 
beach-drift, a circumstance explained below as arising from the 
usual non-buoyancy of Hawaiian seeds. 

That the seeds of Caesalpinia bonducella stranded on the coasts 
of an oceanic island are able to germinate and reproduce the plant 
is, of course, established by the distribution of the species ; and we 
have just observed that the process was noticed by the author on 



1 90 A NATURALIST IN THE PACIFIC CHAP. 

Keeling Atoll where the plant has found a home. It is to be 
noted that the plant collected by Darwin in this atoll was identified 
by Prof. Henslow as C. bonduc ; but the plant observed by me 
was more like C. bonducella, and the stranded seeds collected by 
me were referred at Kew to this species. Some curious considera- 
tions arise from the fact that although, just as in the Keeling 
Islands, the plants of C. bonducella have evidently established 
themselves from drift seed in one locality in the Bermudas, they 
do not seem to have done so either on the shores of Krakatoa, or 
of St. Helena, where, although they are frequently washed ashore, 
Mr. Melliss never met with an instance of germination (see Bot. 
Chall. Exped. iv, 300, and Penzig). This is doubtless in part the 
result of the destructive efforts of the crabs, which, as I have shown 
in my paper on Keeling Atoll, nibble off the shoots of many ger- 
minating seeds in beach drift. 

The readiness or non-readiness of seeds to germinate on a 
beach, and the nature of the conditions essential for the process, are 
matters that are directly concerned with their effective dispersal 
by currents. On account of the stony character of the seeds of 
these two species, it might be expected that germination would 
only take place under exceptional conditions. It should, however, 
be observed that the fine transverse striae on their outer surfa-ce 
represent original fissures or cracks in the epidermis of the soft 
immature seed ; and as such may be regarded as lines of weakness 
in the seed-tests. If a pod is opened before the seeds are mature, 
we find the seeds about twice the size of maturity, and so soft that 
they can be indented by the nail. The transverse striae that mark 
the mature seed are displayed as indistinct cracks in the epidermis ; 
and if the immature seed is exposed to the sun, in a few hours 
these cracks gape widely, and the seed has the grooved appearance 
of a top. If a pod opens prematurely on a plant, as sometimes 
happens, the immature seeds will be noticed with the epidermis 
scaling off. It is evident that the "setting" or the induration of 
the seed-coats and the final great contraction of the seed take 
place in the pod before dehiscence. From these remarks it would 
seem probable that seeds lying exposed to the fierce rays of the 
sun on a tropical beach would be liable to develop cracks along 
the old fissures, and that such cracks by permitting the entrance of 
moisture would favour germination. 

My experiments show that high temperature under moist con- 
ditions will not of itself induce germination or in any way affect 
the seed. Thus in two sets of experiments, in 1890 and 1902, I 



xvn C^ESALPINIA 191 

failed to induce the germination of seeds which, after floating a 
year in sea-water, were kept in moist soil at a high temperature. 
In one case a temperature varying from 80 to 1 10 F. was sustained 
for several weeks, and in the other experiment a temperature of 
80 to 90 was kept up for five months. When, however, an incision 
was made into the epidermis, or the seed-coats were partially 
penetrated with a file, the seeds swelled up in a day or two, and in 
a few days began to germinate. 

The rapid transformation of the stone-like seed into a softened, 
swollen, germinating mass ranks amongst the numerous little 
wonders of the plant world. The seed, in fact, assumes again the 
appearance of immaturity, and in so doing it suggests to us that 
the rest-stage exemplified in the hard, pebble-like seed is but an 
adaptation to general climatic conditions, and that in a region of 
great heat and humidity, where there are no seasons, and where the 
sun's rays are for ever screened off by mist and cloud, it could be 
dispensed with altogether. One of my Hawaiian dreams was to 
establish vivipary in Caesalpinia bonducella by subjecting the 
maturing pod on the plant to very warm and humid conditions, my 
expectation being that the soft, swollen seed would at once proceed 
to germinate in the pod, and that the final process of setting, as 
indicated by the induration and contraction of the coats, or in 
other words the rest-stage, would be done away with. The dream, 
however, bore some fruits in enlarging my standpoint in the 
matter of vivipary, and I have referred to the subject in Chapter 
XXXI. 

The seed-shell, about 1-5 mm. in thickness, consists of three 
coats : the outer skin very tough and waterproof ; the inner skin 
seemingly permeable ; and the intermediate layer of hard prismatic 
tissue, the " prismenschicht " of Schimper (p. 164). This middle 
layer absorbs water rapidly and in large quantity, so that if a 
fragment of the shell is placed in water it will be found after a 
day's soaking to be three times as thick as it was in the dry state. 
If one files a seed, or makes a small incision, so as to expose the 
middle layer without piercing the inner coat, and then places it in 
water, it will be noticed that the middle layer at once begins to 
absorb water ; and within a couple of days the whole seed will 
swell and attain the size it possessed in the so-called immature 
condition. During the process the outer skin stretches, usually 
without rupturing ; and all three coats, previously so hard that a 
heavy blow with a hammer is required to break the seed, become 
in a day or two soft enough to be easily cut with a knife. The 



i 9 2 A NATURALIST IN THE PACIFIC CHAP. 

seeds thus treated swell in two days to three times their original 
size and increase their weight fourfold. Water finds its way to 
the nucleus or embryo partly through the dilated inner opening of 
the micropylar passage and partly through the inner skin. The 
nucleus then swells up into a fleshy mass, filling the seed-cavity, 
and in two or three days more germination begins. 

I pass now to the discussion of the buoyancy of the seeds. 
Considering that both species occur in oceanic islands, and that the 
currents are active agents in transporting the seeds, their behaviour 
under experiment appears at first sight to be full of anomalies. 
Thus, it was ascertained at Kew (Bot. ChalL Exped. iv., 301), both 
with comparatively fresh and with older seeds, that those of 
Caesalpinia bonducella floated in salt water, whilst those of 
C. bonduc sank ; but in the record given of the experiment no 
mention is made of the original station of the parent plants ; and it 
will be shown later on that the station of the plant, whether at the 
coast or inland, has an important determining influence on the 
buoyancy. 

In Fiji I found that almost without exception the seeds of littoral 
plants of Caesalpinia bonducella floated both in sea-water and in fresh 
water. On the other hand, in Hawaii the seeds of this species, 
obtained from three typical localities removed inland from the 
beach, sank without exception, even after drying for several months ; 
and the only buoyant seed noted in these islands was a solitary seed 
collected from the beach drift. In Hawaii, however, as before 
remarked, the species is not strictly a littoral plant, occurring as it 
does in the lower levels, but not necessarily in the vicinity of the 
coast. In the case of seeds of littoral plants of C. bonduc in 
Fiji, I found that sometimes all floated in sea-water and some- 
times only a portion of them, whilst their specific weight was 
on the whole rather greater than that of the seeds of the other 
species. Thus, in one experiment half the seeds floated in sea- 
water and a quarter in fresh water, whilst with seeds from another 
locality 90 per cent, of the seeds floated in sea-water and 80 per 
cent, in fresh-water ; and in a third set of seeds all floated in both 
waters. 

The above experiments on Fijian seeds all relate to littoral 
plants. In the instance, however, of the inland species from the 
mountains of Vanua Levu, all the seeds sank in sea-water, even 
after being kept for five years. If we follow the indications of 
these several experiments we shall find that Caesalpinia presents 
another illustration of the general principle established in Chapter 



xvn OESALPINIA 193 

II that the seeds of inland plants sink and those of coast plants 
float. 

My data, therefore, show that with the seeds of Caesalpinia 
buoyancy goes with station and not necessarily with species. It is 
probable, therefore, that with the two widespread species, C. bondu- 
cella and C. bonduc, varying results will be obtained with seeds 
from different localities, whether insular or continental, according 
to the original station. The typically buoyant seeds of the former 
species may, as we have seen in Hawaii, lose their floating powers 
when they grow inland ; and the seeds of an inland species from 
the mountains of Fiji sink at once. It is essential in interpreting 
the results of experiments on the seeds of these plants to be 
acquainted with the stations j and in this respect those of the 
Tahitian plants may be regarded as probable test cases. We have 
seen that in Tahiti, C. bonduc is an inland plant, and C. bonducella 
usually a beach plant ; and I have no doubt that experiments in 
that island on the seeds of these two species from the particular 
stations just referred to will give results in agreement with the 
principle here laid down. 

With reference to the duration of the floating powers of these 
seeds it may be observed that a seed of Caesalpinia bonducella, 
originally found stranded on the beaches of Keeling Atoll, floated 
after a year in sea-water as buoyantly as at the commencement of 
the experiment. Seeds of Fijian littoral plants of both 
C. bonducella and C. bonduc floated in my experiments after 
two and a half years' immersion in sea-water, showing no change 
whatever. Some of the seeds removed at the end of the first year 
were filed and placed in soil, when they germinated healthily. In 
Chapter IX it is pointed out that some buoyant seeds of other 
Leguminous plants, such as Mucuna urens, would be apt to 
germinate abortively and to sink in crossing the more heated areas 
of tropical seas. The seeds of Caesalpinia, judging from my experi- 
ments and observations noted on page 84, seem to be quite proof 
against such risks. This was well brought out in an experiment 
where seeds of the two species of Caesalpinia were kept afloat for two 
and a half years in a vessel of sea-water together with seeds of 
Mucuna and Strongylodon. None of the Caesalpinia seeds at- 
tempted to germinate in the sea-water ; but with the other genera 
some of the seeds began to germinate, and sank in the course of 
the first warm season, when the water-temperature ranged from 
75 to 90 Fahr. 

The seeds develop their buoyancy during the great contraction 
VOL. II O 



i 9 4 A NATURALIST IN THE PACIFIC CHAP.. 

that, as before described, marks the final setting of the seed-coats 
and the ultimate maturation, as it is termed, of the seed. During 
this shrinking process the kernel also shrinks within the seed-tests, 
and cavities are thus produced within the seed-shell, on the 
relative size of which depends the buoyancy of the seed, neither 
the seed-shell nor the kernel possessing independent floating- 
power. These cavities, as illustrated in the figures given in 
Chapter XII, are of two kinds. That usually produced, being the 
one that mainly determines the buoyancy, is a large central hollow 
caused by the arching outwards of the cotyledons during the 
shrinking process, such as is found also in the seeds of Entada 
scandens, Mucuna urens, and some other Leguminous littoral 
plants. With such seeds the kernel never rattles when the 
seed is shaken, since the cotyledons lie in close contact with the 
seed-shell. The other kind of cavity is produced between the seed- 
shell and the kernel by the general or partial shrinking of the 
kernel away from the shell, the cotyledons remaining in apposition, 
as shown in the figures. When the shrinking away from the shell 
is general, the kernel lies loose within the shell, and the seed 
rattles when shaken. When the shrinking is partial the cavity is 
on one side of the seed and the kernel is fixed. 

Professor Schimper (p. 164) remarks that the buoyant seeds of 
Csesalpinia bonducella all rattle when shaken, and that it is to the 
incomplete filling of the seed-cavity, thus indicated by the loose 
kernels, that the buoyancy of the seed is due. The rattling of the 
kernel was, however, quite exceptional in the seeds handled by me, 
even in the case of originally buoyant seeds kept for five 
years. Seeds with loose kernels were, in fact, more frequent 
with non-buoyant seeds than with those that floated. Thus in 
Fiji I found that whilst with the buoyant seeds 17 to 20 
per cent, had loose kernels, with non-buoyant seeds the pro- 
portion was as much as 60 per cent. 

The normal cause of buoyancy is, therefore, a large inter- 
cotyledonary cavity with the cotyledons lying in close contact with 
the seed-shell ; but the two kinds of cavity may sometimes be 
combined. Out of a number of buoyant seeds of Csesalpinia 
bonducella examined by me, 80 per cent, owed their buoyancy 
solely to a large central cavity (4 to 5 mm. across). In 6 per 
cent, it was due solely to the shrinking of the kernel away from 
the seed-shell ; whilst in 14 per cent, it was to be attributed partly 
to a reduced central cavity (2 to 3 mm. wide), and partly to a space 
outside the kernel. The only difference noted in the structure of the 



XVII 



OESALPINIA 195 



buoyant seeds of C. bonduc was that the two kinds of cavities were 
more often combined. 

The reason of the absence of floating power was clearly 
indicated in the non-buoyant Hawaiian seeds, where there was no 
central cavity, or it was represented by a narrow slit. The solitary 
buoyant seed found in the beach drift had a typical large central 
cavity. With the non-buoyant seeds of the inland species of the 
mountains of Vanua Levu it was ascertained that two-thirds had 
loose kernels with the cotyledons closely appressed. In the others 
there was a lateral cavity outside the kernel, the central cavity 
being only represented by a slit, a hair's width in breadth. In 
the non-buoyant seeds of C. bonduc, the central cavity was only 
2 to 3 mm. wide, and the lateral cavities were small. 

Respecting the influence of " station " in producing the 
differences in buoyancy, it cannot be said to be connected with the 
maturation of the seeds of inland plants under more humid con- 
ditions than those which prevail at the coast. In Fiji some of the 
littoral plants with buoyant seeds grow on the mangrove-trees in 
the shade and humidity of the swamps ; whilst in Hawaii the 
inland plants of Caesalpinia bonducella with their non-buoyant 
seeds thrive in exposed arid situations in districts of little rainfall, 
such as on scantily vegetated lava-flows. With non-buoyant seeds, 
where there is little or no cavity, the cotyledons are always 
thicker and moister than in the case of the seeds that float. 
Though associated with differences in station, as implied in the 
terms " coast " and " inland," the cause of the difference in 
buoyancy is not connected with different degrees of humidity, but 
with some other cause or causes acting on the spot which, while 
they favour the drying of the kernel in coast plants before the 
seed-coats finally set, impede it in the inland plants. That the 
seed does not subsequently acquire floating power, even after 
years of drying, was shown in several of my experiments. 

The light, unopened prickly pods of both species float buoyantly, 
even when the inclosed seeds have no floating power. In an 
experiment on Caesalpinia bonduc in Fiji the pods remained afloat 
after a month in sea-water. With those of C. bonducella in Hawaii 
I found that they floated for several weeks, and in one case a pod 
was afloat after three months. The pods dehisce on the plant ; 
but they sometimes do not open sufficiently to allow the seeds to 
fall out. The pods, however, have to be torn off from the plant, 
and are not likely to occur in the drift. Indeed, they never came 
under my notice in any locality in the drift, and as an effective aid 

O 2 



196 A NATURALIST IN THE PACIFIC CHAP. 

to dispersal they must be disregarded. The buoyancy of the seeds 
and their well established distribution by currents render unneces- 
sary an appeal to the floating pod. 

The following is a summary of the foregoing remarks on 
Csesalpinia bonducella and C. bonduc. 

(1) The two species in Fiji are not always sharply distinguished, 
since intermediate forms occur, and here probably lies the explana- 
tion of the confusion that has sometimes occurred in diagnosing the 
species. 

(2) Both are typical littoral plants, distributed over most of the 
tropical zone, and occurring in company in most of the Pacific 
archipelagoes ; but they at times extend far inland. 

(3) Though it is not unlikely that sea-birds may have aided in 
their dispersal, the oceanic currents have been the great agencies in 
their dispersal, as is indicated by the frequent transport of seeds 
In the Gulf Stream drift across the Atlantic, and by their occur- 
rence in beach drift in various parts of the world. 

(4) Having regard to the present arrangement of the currents 
and the distribution of the two species, reasons are given for the 
belief that their original birthplace was in the interior of the 
American continent. 

(5) Notwithstanding the stony hardness of the seeds, when a 
notch is made in the outer skin a seed rapidly takes up water, and 
in a few days it becomes a soft and much swollen germinating 
mass. The author is inclined to think that this was the original 
condition of the seed, and that the rest-stage is an adaptation 
to secular differentiation of climate in later epochs. 

(6) Unlike the seeds of other Leguminous littoral plants, those 
of Caesalpinia are not likely to germinate abortively when floating 
in warm tropical seas, a risk that restricts the distribution of several 
littoral species. 

(7) As tested by experiment, the seeds of both species are often 
able to float unharmed for years ; but on the other hand seeds not 
infrequently have no floating power. 

(8) Observation, however, shows that buoyancy goes with 
station, and that the general rule here applies that the seeds of 
coast plants float and those of inland plants sink. 

(9) The nature of the influence of " station " on the seed- 
buoyancy is obscure ; but it is evidently not connected with the 
usual differences between coast and inland localities, such as those 
concerned with exposure or shade, dryness of soil, relative humidity, 
and similar contrasts. 



xvii C^SALPINIA 197 

(10) The buoyancy of the seed is developed during the final 
shrinking process associated with its maturation, a large cavity 
between the cotyledons being usually produced. 



Note. Since most of the principal conclusions of this work are 
involved in my especial study of the littoral species of Afzelia, 
Caesalpinia, and Entada, the reader is advised, if he wishes to form 
an opinion of the author's method of investigation, to read this 
chapter carefully through. With most other shore-plants, though 
in not a few cases studied with the same detail, the exigencies of 
space have often limited me to the employment of the general 
results in the appropriate chapters without entering into details. 
Should he desire to test any view of his own relating to plant- 
dispersal, he could not do better than begin with the materials here 
provided. 



CHAPTER XVIII 

THE ENIGMAS OF THE LEGUMINOS^ OF THE PACIFIC ISLANDS 

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

IT is my intention here to gather up some of the "ends "of 
the great tangle presented by the Leguminosae in the Pacific. 
When we look at the indigenous phanerogamic floras of Fiji, 
Samoa, Tahiti, and Hawaii we find that the Leguminosae form 
5 or 6 per cent, of the total in each of the three first-named groups, 
and only about 2*5 per cent, in Hawaii. The paucity of Legu- 
minosse in oceanic floras was long ago pointed out by Sir Joseph 
Hooker, whose work forms the foundation of much of our know- 
ledge of insular plant-life. This is emphasised by Mr. Hemsley in 
his volume on the Botany of the " Challenger" Expedition (Introd. 
p. 25), where he makes the very significant remark that the 
Leguminosae are wanting in a large number of oceanic islands 
where there is no truly littoral flora. The islands, however, here 
more especially referred to, are those of the southern Atlantic and 
Indian oceans, such as St. Helena, Tristan da Cunha, and Amster- 
dam. It is especially true of New Zealand, where the Leguminosae 
barely make 2 per cent, of the total. Of the Polynesian islands, as 
he points out, it is not so correct ; and, in fact, the proportion found 
in the Fijian, Samoan, and Tahitian floras, respectively, is much 
the same as that which characterises the British flora, namely, 
5 to 6 per cent. 

When we come to explain the paucity of the Leguminosae 
in the Hawaiian flora we bring to light the singular principle that 
Leguminosa are far more characteristic of the littoral flora than of 



CH. xvin THE LEGUMINOS^: OF THE PACIFIC ISLANDS 199 

the inland flora of a Pacific island. About half of the Leguminosae 
of Fiji and Tahiti are coast plants ; and about 30 per cent, of the 
littoral plants of the islands of the tropical Pacific belong to 
this order. Since, therefore, Hawaii possesses much fewer shore- 
plants (30) than does Tahiti (55) or Fiji (80), the paucity of its 
Leguminous plants is readily accounted for. 

We have next to notice a principle, which is, in fact, deducible 
from the first, namely, that buoyant seeds are much more charac- 
teristic of the Pacific Leguminosce than of any other order. Three- 
fourths of the species have buoyant seeds, and, in fact, about a third 
of the littoral Polynesian plants with buoyant seeds or fruits belong 
to this order. 

It may, therefore, be inferred that the Leguminoscz owe their 
presence in the islands of the tropical Pacific mainly to the currents. 

From Mr. Hemsley's conclusion that the Leguminosae are 
wanting in a large number of islands where there is no truly 
littoral flora, the presumptions arise that when inland species exist 
that possess no capacity for dispersal by currents they are to be re- 
garded as derivatives from the littoral flora, and that they owe their 
origin to a strand-plant possessing buoyant seeds originally brought 
by the currents. It has been shown in the case of Afzelia bijuga 
and of Csesalpinia that when Leguminous shore-plants extend 
inland the seeds often lose their buoyancy, and it is probable that 
divergence in other characters may occur, leading, as in the moun- 
tains of Fiji, to the development of a new species of Caesalpinia. It 
is urged that by a continuation of the same process the inland 
species, Erythrina monosperma, has been developed in Tahiti and 
Hawaii, and the inland species, Canavalia galeata and Sophora 
chrysophylla, have been produced in the last-named group. All 
these species have non-buoyant seeds, and in all three cases there 
is no littoral species in Hawaii, it being assumed that the parent 
strand-plant has been driven inland from the beach. // is not 
necessary that the littoral species should be now represented in the 
flora. 

It is remarkable that in almost all cases the cause of buoyancy is 
of the non-adaptive or mechanical kind, due either to cavities formed 
by the shrinking of the seed-nucleus during the setting of the seed 
or to the light specific weight of the kernel. There is but little 
to show that the buoyancy of the seeds of Leguminosae is anything 
but an adventitious character of the seed, as far as its relation to 
dispersal by currents is concerned. Although this capacity has 
been the great factor in the wide distribution of the species, yet it 



200 A NATURALIST IN THE PACIFIC CHAP. 

is evident that Nature here takes advantage of a quality that could 
never by its aid become a specific distinction. The upshot of the 
selecting process would be the dispersal by the currents of nearly 
empty seeds or seeds that have lost their germinating capacity. 

The distribution of the Leguminosae in the Pacific islands, and 
indeed of tropical islands generally, is often full of inconsistencies. 
This is the only order that sets at nought most of the principles 
established for the other plants of the sea-coast, and that defies the 
application of the laws of plant-dispersal now most in evidence. 
Take, for instance, the inexplicable affinity of Acacia koa, the 
well-known Koa tree of the Hawaiian forests, to Acacia hetero- 
phylla, a tree restricted to the Mascarene islands of Mauritius and 
Bourbon. Mr. Bentham, who placed them in the same group with 
three or four Australian species, even doubted whether the differ- 
ence between the Hawaiian and Mascarene species amounted to 
specific rank. These two closely related Acacia trees of far-sepa- 
rated islands of the Indian and Pacific Oceans represent outliers of 
the great formation of phyllodineous Acacias that have their home 
in Australia (Introd. ChalL Bot. p. 26). As far as I can gather 
Acacia seeds have no known means of dispersal. Not even when 
the tree has a littoral station, as in the case of Acacia laurifolia in 
Fiji, have the seeds or pods any capacity worth speaking of for 
dispersal by currents. We must appeal to the birds ; but to what 
birds we may ask, unless it be to the extinct Columbae and their 
kin, or to the Megapodes. Some of the other Hawaiian difficulties 
connected with the inland Leguminosae are repeated in the Mascarene 
Islands. Thus, Bourbon, like Hawaii, has its inland species of 
Sophora of the section Edwardsia. 

In their irregular distribution the Leguminosae of the Pacific 
islands are often a source of perplexity to the student of plant- 
dispersal. Take, for example, the inland Erythrina, E. mono- 
sperma, of Hawaii, Tahiti, and perhaps New Caledonia. Then 
look at the singular distribution of the Sophoras of the Edwardsia 
section in Chile and Peru, Hawaii, New Zealand, Further India, 
and Bourbon. The botanist, again, finds a climber like Strongy- 
lodon in the forests of Fiji, Tahiti, and Hawaii, and he picks up the 
seeds on the beaches of those islands and notices that they float 
unharmed for many months in the sea, yet when he pays heed to 
the distribution of the genus he finds that it only comprises four or 
five species, and that it occurs outside the Pacific only in the 
Philippines, Ceylon, and Madagascar. The extraordinary distri- 
bution of Entada scandens in the Pacific islands has been before 



xvni THE LEGUMINOS^E OF THE PACIFIC ISLANDS 201 

alluded to in these pages. Here we have a plant, the seeds of 
which are known to be transported unharmed by currents all round 
the tropics. Yet it is absent from Hawaii and from almost all of 
the islands of Eastern Polynesia. In many cases an endeavour has 
been made in this work to explain these difficulties. But the order 
in the Pacific teems with such difficulties. We may ask with 
astonishment why it is that the genera, and sometimes even the 
separate species, of the Leguminosse seem so often to follow in 
each case a principle of their own. 

Plants of this order in the Pacific conform to no one rule of 
dispersal or distribution, whether we regard a species, a genus, or 
the whole order. Take, for instance, the presence in Hawaii of 
Canavalia galeata, a plant that, as we know it now, could not 
possibly have reached there through the agency of the currents, 
and the absence from the same group of Entada scandens that could 
have been readily transported there by the currents from America. 
Or, if we take the whole order and look at the structures connected 
with the buoyancy of the seeds, we find two types of structure and 
the elements of a third. Then, again, whilst most littoral plants 
with buoyant seeds retain the buoyancy of their seeds when they 
extend inland, Leguminous shore-plants, like Afzelia bijuga and 
Caesalpinia bonducella, when they extend inland in Fiji and Hawaii, 
lose in great part or entirely the floating power of their seeds. 

Furthermore, most strand-plants, being typically xerophilous in 
character, when they extend inland shun the forests and prefer the 
dry soil and sparsely vegetated surface of the open plain ; but the 
Leguminous genera and species (Mucuna, Afzelia, Entada, &c.) 
when they leave the coast take to the forests, growing usually as 
stout lianes, but sometimes as tall trees. Here again the Legu- 
minosae seem to follow a principle of their own. As far as I know, 
this is the only order in the Pacific possessing forest-trees which, 
as in the case of Afzelia bijuga in Fiji, are equally at home in the 
woods of the interior and of the coast. 

Indeed, judging from Professor Schimper's observations, the 
littoral Leguminosse of the tropics often display a physiological 
constitution that seems in some respects out of touch with their 
surroundings. They may, as in Sophora tomentosa and in Cana- 
valia, present the xerophytic character of strand-plants, but fre- 
quently they are not halophilous or " salt-loving," like other plants 
associated with them on the same shore-station. They are often 
shy of salt in their tissues, though able to thrive in salt-rich locali- 
ties. That capacity which strand-plants usually possess of storing 



202 A NATURALIST IN THE PACIFIC CHAP. 

up chlorides in their tissues, and especially in their leaves, without 
injury to themselves, is but slightly possessed by such characteristic 
shore-plants as Canavalia, Pongamia glabra, and Sophora tomen- 
tosa. This capacity, which, as Professor Schimper indicates, goes 
to determine whether or not plants are capable of living in salt-rich 
localities, has often no determining influence with the Leguminosse. 
(See Note 60.) 

Though the plants of this order form such a large element in the 
strand-flora of the Pacific islands and of the tropics generally, 
they seem in other respects, besides those just referred to, to act as 
if they were strangers to the station. Look, for instance, at the 
readiness of the floating beans of Mucuna, Strongylodon, &c., to 
germinate, as shown in Chapter IX, in the tepid waters of the 
warmer areas of the tropical oceans. This is a great deal more 
than a disturbing factor of distribution. It is significant also of 
the plants being out of touch with their dispersing agencies. 

One may notice in conclusion the fact brought out in 
Chapter VIII that nearly all the littoral plants dispersed by the 
currents that are common to the Old and the New Worlds belong 
to the Leguminosae. This is held to indicate that their home is in 
America, since that continent distributes but does not receive 
tropical littoral plants dispersed by currents. 



Summary. 

The Leguminosae are far more characteristic of the littoral flora 
than of the inland flora of the Pacific islands ; and since the greater 
number of them have buoyant seeds, it follows that this order 
mainly owes its presence in this region to the currents. 

As it has been shown that in a large number of islands where 
there is no littoral flora the Leguminosae are wanting, the presumption 
arises that when, as in Hawaii, inland species occur which at present 
have no capacity for dispersal by currents, they have been derived 
from strand-plants originally brought by the currents, even though 
such shore species no longer belong to the flora. 

As far as its relation to dispersal by currents is concerned, the 
buoyancy of the seeds of Leguminosae is merely an adventitious 
character, and the structure connected with it has no specific 
value. 

Plants of this order in the Pacific are a source of much 
perplexity and conform to no one rule of dispersal, whether as 
regards their disconnected distribution, their means of dispersal, the 



xvin THE LEGUMINOS^: OF THE PACIFIC ISLANDS 203 

structural cause of buoyancy, the loss of buoyancy of inland species, 
and in other particulars. Even in their physiological constitution 
they are often at variance with the bulk of littoral plants when they 
grow on the sea-shore, since typical beach-plants of the order, 
though thriving in salt-rich localities, are shy of salt in their 
tissues. 

It is probable that whilst the Pacific islands have derived most 
of their littoral plants that are dispersed by currents from the 
tropics of the Old World, they have received most of their strand 
Leguminosae from America. 



CHAPTER XIX 
THE INLAND PLANTS OF THE PACIFIC ISLANDS 

PRELIMINARY COMPARISON OF THE PHYSICAL CONDITIONS OF 
HAWAII, FIJI, AND TAHITI 

Introductory remarks. The tranquil working of the winds and currents con- 
trasted 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. 

INTRODUCTORY REMARKS. 

I WILL carry my readers back to that moment when we began to 
investigate together the composition of the floras of the islands of 
the tropical Pacific from the standpoint of dispersal. It will be 
remembered that after collecting all the fruits and seeds of a 
particular island we placed them in sea-water, and that some nine- 
tenths of them went to the bottom at once or in a few days. We 
found, speaking generally, that the buoyant seeds and fruits 
belonged to coast plants, whilst those at the bottom of the vessel 
proved to be obtained from inland plants. Since that period we 
have been occupied in following up the clue supplied by the floating 
seeds and fruits. In their company we have travelled far beyond 
the Pacific islands. We have not only seen their fellows in other 
parts of the tropics, both on the coral atoll and on the continental 
coast, but we have met their representatives on the beaches of 
Europe and of temperate South America. We have followed them 
in their ocean traverses round most of the tropical zone, and on the 
way we have naturally interested ourselves in the question of the 
currents. We have weighed these seeds and fruits and have 
compared their specific weight with that of sea-water. We have 



CH. xix THE PHYSICAL CONDITIONS 205 

cut them up and carefully examined them, and under their 
guidance we have explored the mangrove-swamps both of Polynesia 
and of Ecuador, and have penetrated the mysterious cut de sac of 
vivipary. Having formed our opinion of them, we now bid the 
subject farewell, and stand once more on the same Pacific beach 
where, it seems so long ago, our investigations began. 

For the seed and fruits lying at the bottom of the sea-water we 
have to appeal to other agencies than to that of the currents if we 
wish to inquire into their means of arriving at this island. In 
imagination we leave the reef-lined shores for the interior, and 
exchange the exhilarating surroundings of a coral beach, where 
" the sky is always blue and the wind is always true," for the arid 
conditions of an inland plain, or for the humid conditions of the 
forest, where the rain is incessant and the cloud-cap and mist 
seemingly eternal. When we look at the motley collection of fruits 
and seeds obtained in such localities, we are at a loss to know 
where to take up the clue. After vainly endeavouring to obtain 
some inspiration as to the manner of commencing the inquiry, we 
do what all good naturalists in the Pacific islands do from force of 
habit when they meet with difficulties of any kind we sit down and 
light our pipes. Then come a flood of old memories and old trains 
of thought that came to us years before on some mountain-top or 
in a shady gorge or on some river-bank, in regions Pacific and non- 
Pacific, and by degrees our ideas shape themselves and we begin to 
think the matter over in an orderly fashion. 

When the winds first brought the spores of ferns to this Pacific 
island, the ocean currents brought the seeds and fruits of littoral 
plants, and the birds transported the seeds and " stones " of various 
inland species. All three agencies have been working side by side 
since the earliest stage in its history. Yet it is only in the work of 
the wind and the current that we find any indication of stability in 
the floral history of the island. With the work of the bird it has 
been very different. Since the first bird carried seeds to this 
locality all else has been turmoil and change. Wave after wave of 
migrant plants has overrun the interior of the island, and all have 
left their mark ; but the great distributing factor and disturbing 
agent has always been the bird. Genera have been born and have 
disappeared, and in their place new genera have arisen. Whole 
families even have participated in the revolutions of the plant-world, 
and species have grown rankly in the great confusion. Last of all 
came man with his cultivated plants and his weeds, introducing 
new elements of change and discord into the island, and often up- 



206 A NATURALIST IN THE PACIFIC CHAP. 

setting the floral economy altogether. The history of man's most 
troubled epoch would not be more full of catastrophes and great 
events than the history of the plants of this Pacific island. Yet 
through all these changes the winds and currents have been quietly 
carrying on their work, bringing the same plants to beach and hill- 
side that they did before the age of unrest began. 

The monotonous character of an island flora that has been 
supplied by the winds and currents can be readily imagined. For 
their variety the floras of the Pacific islands are mainly indebted 
to the bird, the great disturber of the peace of the plant world. 
We cannot attach too much importance to the contrast in the 
results produced by these several agencies in stocking a Pacific 
island with its plants, On the one hand we have the tranquil 
working through the ages of the winds and currents. On the other 
hand there has been the revolutionary influence of the bird. One 
cannot doubt that many of the species of flowering plants now 
growing on the beach and many of the ferns on the upper 
mountain-slopes have witnessed changes within the forest-zone of 
the island, such as an antediluvian might record if he had lived 
through the ages to the present time. 

Now, what are these changes ? How has the bird acted un- 
consciously such a determining part ? These are questions which 
I will endeavour in some way to answer as one picks one's path 
slowly through the various epochs in the plant-history of these 
islands. We already are fairly well acquainted with the beginnings 
of a flora either on a coral atoll or on an ordinary tropical beach. 
What we have yet to learn is the subsequent history of the flora. 
When Dr. Treub undertook, in 1886, his now celebrated examina- 
tion of the new flora of Krakatoa after the great eruption, he com- 
menced a series of observations which will no doubt be prolonged 
into future centuries. Botanists a hundred and two hundred years 
hence will complete a long chain of observations which will be 
unique as a record of plant-colonisation ; and science is deeply 
indebted to Prof. Penzig for making, in 1897, the second examina- 
tion of the new flora. Though deprived of the valuable record 
that future generations will possess for Krakatoa, we yet have at 
our disposal in the completed process displayed by many a Pacific 
island a means of working backward and in a sense completing 
the history. 

In order to attack this problem I have mainly confined myself 

to the Fijian, Tahitian, and Hawaiian floras, taking the three archi- 

lagoes just named as the centres of the regions in which they 



xix THE PHYSICAL CONDITIONS 207 

occur. These three groups lie near the three angles of the tri- 
angular area of the Pacific over which the various archipelagoes 
are scattered. They are thus geographically well placed for an 
inquiry into the subject of plant-dispersal over this ocean, and 
each of their floras has been investigated by botanists of various 
nationalities American, Austrian, British, French, German, and 
Italian. The Fijian area may be regarded as including the adjacent 
Samoan and Tongan groups, though the individual group or the 
whole area will always be in this work particularised. In the same 
way Tahiti will be viewed as usually representative of the larger 
islands of the surrounding groups of the Cook and Austral Islands 
and of the Marquesas ; and under the designation of the Tahitian 
area or Tahitian region there will be generally included the 
Paumotu archipelago. 

COMPARISON OF THE AREAS AND ALTITUDES OF HAWAII, 
FIJI, AND TAHITI. 

Since differences in physical conditions have played an impor- 
tant part in plant distribution in these groups such, for instance > 
as in determining the development of a mountain flora or in 
favouring the relative abundance of particular types of plants 
it is at first essential to obtain a general idea, in the case of the 
larger islands of each group, of their size and elevation, and of 
the more conspicuous differences in their climates. 

Hawaii, the largest island of the Hawaiian archipelago, has an 
area of 4,210 square miles. All the other islands of the group are 
considerably smaller Maui, the second in size, having a surface of 
760 square miles ; Oahu coming next ; and after it Kauai, with an 
area of 590 square miles. The area of Viti Levu, the largest 
island of the Fijis, is 4,112 square miles, being thus closely similar 
to that of the island of Hawaii ; Vanua Levu, the second in size, 
is 2,433 square miles in extent ; whilst the other important islands 
of the group are much smaller, Taviuni, the third in size, having 
an area of 218, and Kandavu an area of 125 square miles. Tahiti, 
the largest and loftiest island of Eastern Polynesia, has a surface 
of about 400 square miles ; whilst most of the other elevated 
islands of the groups around are considerably smaller. 

In respect of elevation above the sea, there is a great contrast 
between the islands of these three regions. Taking the Hawaiian 
Group first, we notice that the three principal mountains of the 
large island of Hawaii rise in the cases of Mauna Kea and Mauna 



2o8 A NATURALIST IN THE PACIFIC CHAP. 

Loa to between 13,000 and 14,000 feet, and in that of Hualalai to 
rather over 8,000 feet. Situated between these three mountains 
there is an extensive tableland or plateau, known as the Cattle 
Plains, which is elevated between 4,000 and 6,000 feet, and has an 
area of not less than ; 200 square miles. At least a third of the 
whole area of the island exceeds 4,000 feet in altitude. In the 
eastern portion of Maui the huge mass of Haleakala rises to rather 
over 10,000 feet ; whilst Mount Eeka, in West Maui, rises in bulk 
to some 6,000 feet. The island of Kauai, which is elevated between 
5,000 and 6,000 feet, possesses in its interior an elevated tableland 
40 square miles in extent and 4,000 feet in altitude. Oahu attains 
in Mount Kaala a maximum elevation of 4,000 feet, but 3,000 feet 
is the limit of the other peaks, and much of the island is low in 
elevation. 

On the other hand, in the two largest islands of Fiji, namely, 
Viti Levu and Vanua Levu, we find in the first-named only two or 
three of the highest mountain peaks rising to between 4,000 and 5,000 
feet ; whilst the highest peak of Vanua Levu reaches only to about 
3,500 feet. Amongst the lesser islands, Taviuni just reaches the 
level of 4,000 feet, and Kandavu, the next in height, about 2,750 
feet. The area of the land-surface in this group that is above 
a level of 4,000 feet is very scanty, and for the botanist a negli- 
gible quantity, so that for purposes of comparison the Fijian Islands, 
as far as elevation is concerned, correspond to the lower levels of 
the Hawaiian Islands, that is, to the areas below 4,000 feet. The 
same may be said of the Samoan Islands with the exception of a 
limited area in the centre of Savaii, where a peak rises to 5,400 feet 
above the sea. 

Coming to the Tahitian region, we find that Tahiti, the most 
elevated island, attains an extreme height of about 7,300 feet ; but 
from its surface-configuration it is evident that not one-tenth of the 
area exceeds 5,000 feet ; yet since its total extent is about 400 
square miles there must be an elevated region of some 30 square 
miles in amount comparable in some degree with the uplands 
of Hawaii. The Marquesas, next in order in size and height, attain 
a maximum elevation of about 4,000 feet ; whilst, amongst the Cook 
and Austral Groups, Rarotonga reaches a height, according to 
Mr. Cheeseman, of 2,250 feet. Excepting the limited elevated 
area of the uplands of Tahiti, there is nothing in Eastern Polynesia 
corresponding to the higher levels of the Hawaiian Islands over 
4,000 feet. We formed the same conclusion for Fiji, and I may 
add that it applies to the whole area of Fiji, Samoa, and Tonga, 



xix THE PHYSICAL CONDITIONS 209 

since the solitary peak of Savaii in the second-named group, which 
reaches 5,400 feet, alone represents a high-level area. The uplands 
of Hawaii that is to say, the elevated region between 4,000 or 
5,000 feet and 14,000 feet (strictly speaking 13,800 feet) are 
therefore almost unrepresented amongst the oceanic groups of the 
South Pacific ; and it is only in the peak of Savaii and in the 
limited high levels of Tahiti that we would expect to find their 
conditions reproduced. The great effect that this contrast implies 
in determining differences between the floras of the Hawaiian, 
Fijian, and Tahitian regions will become apparent as we proceed 
in this discussion. 



COMPARISON OF THE CLIMATES OF HAWAII, FIJI, AND 

TAHITI. 

Before comparing the climatic conditions in the three groups, 
it may first be remarked that since they lie, roughly speaking, at 
not very dissimilar distances north and south of the equator a great 
contrast is not to be expected in so far as they agree in elevation. 
The mean latitudes do not differ greatly, that of Hawaii being 20 
to 21 N., and those of Fiji and Tahiti both about 18 S. The 
climate of both groups is tempered by the north-east trade in the 
one region and by the south-east trade in the other. Still there is 
a difference in the temperature and dryness of the air which 
noticeably distinguishes Hawaii from Fiji, and to a less extent 
from Tahiti. The mean temperature of the Hawaiian Islands 
would be 74 or 75 ; whilst that of Tahiti is placed at 76 to 77, 
and that of Fiji at 79. But it is to be observed that to a person 
residing in Fiji after a residence in Hawaii the climate is perceptibly 
warmer, more humid, and more enervating. No doubt this is in 
part connected with the greater dryness of the air in Hawaii, where 
the average relative humidity at Honolulu is placed at 72 per cent., 
and it must be much less on the Kona coast on the dry side of 
the largest island. It is, however, probable that the Hawaiian 
climate was less dry before the destruction of the forests, and that 
the contrast with the Fijian climate was then less pronounced. 

The great distinguishing feature, however, of the Hawaiian 
Islands is to be found in their mountain climate. This is not 
represented in Fiji, but slightly in Samoa, and to a small extent in 
Tahiti ; and I will now refer more particularly to this important 
subject. 

In the uplands of the large island of Hawaii, on the tops of the 
VOL. II P 



2IO 



A NATURALIST IN THE PACIFIC 



CHAP. 



lofty mountains 10,000 to 14,000 feet above the sea, we have a mean 
temperature only found far north. Snow lies often on these barren 
summits in winter, more particularly on Mauna Kea, which thus 
derives its native name of the White Mountain. The details of 
my meteorological observations on Mauna Loa will be found in 
Note 61 ; and only some of the general results will be referred to 
here. 

The mean temperature for the period of twenty-three days 
passed by me on the summit of Mauna Loa (13,600 feet) between 
August gth and 3ist, 1897, was 3 8 '5 F. The mean temperature 
for a period of twenty days from December 24th, 1840, to January 
1 2th, 1841, during which Commodore Wilkes and his party were 
making pendulum observations on the summit of the same moun- 
tain, was approximately 33*5 (see Note 61). From these 
results, which are tabulated below, it will be seen that the mean 
annual temperature would be probably about 36, which is scarcely 
comparable with any continental climate, since only a difference of 
a few degrees is indicated between the mean temperatures of 
August and of a similar period in mid-winter. I may add that 
although it was in the summer month of August, water froze inside 
my tent during twenty out of the twenty-three nights passed on 
the top. We may, therefore, infer that the temperature falls below 
the freezing point at night practically throughout the year. It will 
be seen from the table that the mean annual temperature for the 
summit of Mauna Loa, as here computed from the observations 
of Commodore Wilkes and myself, comes very near to that which 
might be estimated by employing Hann's tables of variation in 
temperature with altitude on tropical mountains (see Schimper's 
Plant- Geography, iv. 691). 

WINTER AND SUMMER TEMPERATURES ON THE SUMMIT OF MAUNA LOA 
(13,600 FEET), IN DEGREES FAHRENHEIT. 



Observer. 


Period. 


Mean daily 
range. 


Lowest. 


Highest. 


Mean for 
period. 


Approximate 
yearly mean. 


Wilkes... 
Guppy... 


Dec. 24, 1840 Jan. 12, 1841 
Aug. 931, 1897 


17 -5o =33 
23'2-53 8=30-6 


J 3 
15 


55? 

6l'2 


33 '5 

38-5 


} * 



Estimated mean annual temperature of the summit of Mauna 
Loa, taking that of the coast at 75, would be 34 if the rate of 
increase was the same as on Mount Pangerango in Java (i per 
328 feet). 



xix THE PHYSICAL CONDITIONS 211 

The great daily range of temperature is one of the most 
striking features of the climate of the summit of Mauna Loa. The 
extreme recorded by me was 387, whilst Wilkes registered as 
much as 42. As on most lofty mountains the dryness of the air, 
as indicated by the relative humidity, was usually great. The 
average percentage during my stay between 8 and 9 A.M. was 
44, at midday 43, and between 5 and 6 P.M. 56. This may be 
contrasted with 72, the average for the year at Honolulu. In the 
tropics the mean for the year in the lower levels often rises to 80 
and over ; and it can scarcely be doubted that the Hawaiian 
climate is generally drier than it was before the destruction of the 
forests. The lowest relative humidity recorded by me on the 
summit of Mauna Loa was 20 per cent. Junghuhn on the summits 
of two mountains in Java, 10,500 and 1 1,500 feet in height, recorded 
percentages as low as 5 and 13. Further details relating to this 
subject are given in Note 61. The rainfall on the top of Mauna 
Loa is probably very slight. During my sojourn rain was noted 
on six days, but on only two could it be measured, and the total 
fall could not have amounted to over a third of an inch. 

The mean annual temperature of the great forest-zone at the 
elevations where it displays the greatest luxuriance of growth 
on the island of Hawaii, that is, between 4,000 and 6,000 feet, 
would be estimated at 63 and 57 R, if we take the rate of 
decrease before employed of about three degrees per 1,000 feet. 
But remembering the heavy rainfall in this region and the usual 
occurrence of a protecting belt of cloud during the day, this might 
seem to be too high. According, however, to a table given by Mr. 
Jared G. Smith in his annual report of the Hawaii Agricultural 
Experiment Station for 1902, the average temperature at 4,000 
feet would be 65. I cannot help thinking this is excessive as an 
average for the island. In the latter part of May, 1897, the mean 
temperature during my sojourn of twelve days at elevations between 
6,000 and 6,700 feet around the slopes of Mauna Kea was 51*2 ; 
whilst for eight days in the first part of June in the same region 
the mean temperature was 58-2 at an altitude of 4,000 to 4,300 
feet. 

It is possible, as I have pointed out on a later page, to recognise 
in the different zones of vegetation the floras of a variety of lati- 
tudes ; and these zones are to a large extent controlled by temper- 
ature as well as by other conditions. Thus the Fijian would be 
amongst familiar vegetation on the lower slopes of Mauna Kea, 
whilst the Maori would be at home halfway up the mountain- 

P 2 



212 A NATURALIST IN THE PACIFIC CHAP. 

slopes, and the African from the upper forests of Kilima Njaro 
and Ruwenzori would find in the higher levels much to remind 
him of his native land. 

The upper woods extend usually to 8,000 or 9,000 feet above 
the sea, and vegetation of a scrubby character occurs as high 
generally as 10,000 or 11,000 feet. The highest regions present 
only a barren rocky waste. 

THE RAINFALL. 

The Hawaiian Islands. Although on account of the extensive 
deforesting of the Hawaiian Islands since their discovery the con- 
trast between this group and that of Fiji is now, as regards rainfall, 
somewhat emphasised, it is almost certain that in early times the 
contrast was much less marked. In the lower levels the natives 
and sandalwood traders in the past, and the agriculturists in 
the present, have accomplished much in this direction. Between 
1,000 and 3,000 feet, whole forests were in my time disappearing 
under fire and axe for the coffee plantations. Above those levels 
up to the higher limits of the woods, cattle were destroying the 
forests in a wholesale fashion ; whilst foreign insects were proving 
themselves almost as great enemies to the vegetation. I remember 
an enterprising agriculturist explaining to me how he cleared the 
land of forest around his station. A large tract having been 
fenced in, the cattle were introduced. After destroying the under- 
growth and the young trees, the animals attacked the bark of the 
trees, and in a year or two, without fire or axe, the land was 
cleared. The consequence of this unchecked destruction of the 
forests was in my time becoming only too evident. When I passed 
through Ookala, on the Hamakua coast, at the end of May, 1897, 
there was a water famine. Water was sold at a quarter of a dollar 
a bucket, and the allowance for a family was three oil-cans a week. 
Stealing water was a crime and punished by the plantation 
authorities by dismissal or a five-dollar fine. 

If we could look back for fifty or sixty years I am now 
quoting from the reports of Prof. Koebele and Dr. Stubbs we 
should see large forests where we now see barren slopes and 
plains. Originally forests covered the upland plateaux and moun- 
tain slopes of all the islands. Now much of the original forests 
has been removed, and large areas of naked soils and bare rocks 
remain. The present forest area, writes Mr. Giffard, the editor of 
the Hawaiian Forester (August, 1904), is about 20 per cent, of 



xix THE PHYSICAL CONDITIONS 213 

the islands, a small fraction of what it was a hundred years ago. 
It is, however, very satisfactory to learn that American energy 
is now combating this evil. Already in the January number of the 
same journal is to be found a report by Mr. W. L. Hall, of the 
Bureau of Forestry, on " The Forests of Hawaii"; and now, under 
the charge of Mr. Jared G. Smith, institutions have been formed 
and experiment stations have been established for "the intelligent 
and skilful cultivation of the soil." Hawaii owes much to the 
United States Department of Agriculture. May we in England 
take the cue in the case of our own Crown colonies ! 

Under these circumstances the comparison of the present rain- 
fall of Hawaii must be carried out with discrimination. But it may 
be at once observed that to make a contrast in detail between the 
rainfalls of these three groups is quite beyond the province of this 
work ; and this remark applies also to the other observations on the 
climatic conditions. I can only treat the subject in an illustrative 
fashion in connection with the general subject of their floras. 

Thanks to Professor Lyons, the Government meteorologist, the 
rainfall has long been systematically investigated. It may be said 
to range anywhere between 10 and 300 inches. As in most groups 
within the trade-wind belts, there is a great contrast in the rainfall 
between the weather and leeward sides of the islands, which is well 
exhibited in the large island of Hawaii. Whilst in the Hilo 
district on the wet side of the island the annual rainfall near the 
coast is about 120 inches, on the Kona coast of the dry side of the 
island it may be anything between 20 and 50 inches and it may fall 
to less than 10. The effect of elevation is, however, evident on both 
the weather and lee sides of the island. Thus at a height of 1,650 
feet in the Hilo district it is as much as 180 inches, and at a greater 
elevation 210 inches. At a height of about 1,600 feet at Keala- 
kekua, on the dry side of the island the average yearly rainfall, 
according to the results kindly supplied to me by the Rev. 
S. H. Davis, was for the six years, 1891-6, 60 inches. On the 
beach, as he says, it is " very much less," probably not 30 inches. 
Dr. Maxwell, in his report on " Irrigation in Hawaii," mentions a 
locality in Maui where the rainfall at the sea-shore was 28 inches, and 
at a height of 2,800 feet up the mountain side as much as 179 inches. 
In the region of the cloud-belt, which coincides with that of the 
forest-zone on the slopes of the great mountains of Hawaii and 
extends up from about 3,000 to 7,000 or 8,000 feet above the sea, 
the average annual rainfall would probably be rarely under 200 
inches, and in some localities it might approach 300 inches. There 



214 A NATURALIST IN THE PACIFIC CHAP. 

are some particularly wet mountains, and amongst these may 
be placed the high table-land of Kauai (4,000 feet) and the 
flat summit of Mount Eeka (6,000 feet) in West Maui. Here in 
a region almost of eternal mist we have developed a special 
bog-flora. 

Hillebrand describes the flat top of Mount Eeka as " wrapt in a 
cloud of mist nearly the whole year." Whilst descending this 
mountain I was overtaken by the darkness at a little under 
5,000 feet above the sea. Through the night there was a con- 
tinuous soft rain, or rather a heavy wet mist, and I passed it under 
conditions suggestive of living in a sponge. Everything was reek- 
ing with moisture. The air was saturated with it, and water 
dripped from every leaf and branch, whilst the ground on which I 
stood was soft and yielding and soaked with water like a sponge. 
The surface was cut up by numerous narrow water-channels ten to 
twenty feet deep and only a couple of feet wide, their very exist- 
ence almost concealed by ferns, whilst torrents rushed along at 
the bottom and kept up a strange music through the night. This 
was the longest night I have ever experienced, as my standing- 
ground was very limited, and with a water-channel a foot or two 
away on either side I had to keep on my legs until the dawn. 

Above the cloud-belt, at elevations of 10,000 feet and over, the 
rainfall is evidently very small. I have before remarked that 
during my stay of twenty-three days (August 9-31) on the summit 
of Mauna Loa (13,600 feet) the rain did not exceed one-third of 
an inch in amount. I have by my side the report to the Weather 
Bureau, compiled by Prof. Lyons, on the rainfall of this large island 
of Hawaii for the entire month (August, 1897) >' an d it enables one 
to make a comparison, in some respects unique, of the distribution 
of the August rainfall on Mauna Loa, from its base to its summit, 
where it occupies the breadth of the island. Whilst on the east or 
wet side from the coast up to 1,500 feet amounts ranging from 
ii to 15 inches were measured, on the west or dry side between 
one and two inches were registered at the coast, and 10 inches 
at Kealakekua, about 1,600 feet above the sea. But the level 
of maximum precipitation would lie much further up the mountain 
slopes on either side, probably at an altitude of 4,000 or 5,000 feet, 
and here the rainfall for the month could not have been less 
in either case than 20 inches. Above this line of greatest rainfall 
the amount of atmospheric precipitation would become less and 
less until beyond the upper forest zone above 10,000 feet to 
the summit (13,600 feet) the quantity would be very small; and 



xix THE PHYSICAL CONDITIONS 215 

judging from my observations, that covered three-fourths of the 
month, the rainfall on the top of the mountain for August would 
not have far exceeded half an inch. 

The dry climate of the summits of Mauna Kea and Mauna 
Loa is reproduced on the tops of the Java mountains and on the 
summits of the Owen Stanley Range in New Guinea. Sir W, 
Macgregor found a fine and dry climate on the top of the moun- 
tains last named, beyond the limits of the forests, which extend 
to 12,000 feet above the sea. Below lay the cloud belt, a zone of 
moss and fog, where at an elevation of 7,000 to 8,000 feet every- 
thing was reeking with moisture (Journ. Roy. Geogr. Soc. 1890). 
Observers at the coast often little imagine, when looking at a cloud- 
concealed mountain peak, that although the cloud-belt from below 
looks black and lowering and rain is falling heavily in the gloomy 
forests, there is on the upper side a region of bright sunshine, and 
that the peak stands out, unseen by them, above a sea of clouds 
sparkling brilliantly in the sun and dazzling in their whiteness. 
It will be seen from the table given in Note 61, that during my 
sojourn on the summit of Mauna Loa the sky was cloudless or 
almost free from cloud during nearly half the time. The mean 
cloudiness in the forenoon for twenty-two days was 1*3 and for 
the afternoon 3-5, whilst the nights were cloudless. 

The Rainfall of Fiji. The rainfall of Fiji is known to be very 
large. In illustration I will take Vanua Levu, the second largest 
island, partly because of my familiar acquaintance with it, and 
partly because I have at my disposal measurements for both the 
lee and weather sides of the island the first dry and characterised 
by a scanty and peculiar vegetation, the second humid and densely 
forested. At Davutu, near the sea-level on the weather or wet 
side of the island, the average yearly fall for a period of sixteen 
years up to 1898 was 160 inches (these observations were made in 
the grounds of the manager's house and I am indebted to 
Mr. Barratt for allowing me to inspect them). The mountainous 
backbone of the island, which has an elevation ranging usually from 
2,000 to 3,000 feet, is generally in the rain-clouds. During the 
months I was occupied in examining the geology of these moun- 
tains, it was a common experience to be drenched to the skin all 
day long, and I cannot doubt that the annual rainfall in the higher 
levels must often reach 300 inches. Those familiar with the " sun- 
burnt " lands or " talasinga " plains that mainly form the north or 
lee side of the island, would expect a great difference in rainfall as 
compared with the south or weather side. There is a marked 



216 A NATURALIST IN THE PACIFIC CHAP. 

difference, it is true, but it is far less than we might have looked for. 
At Delanasau on the north coast, less than a hundred feet above the 
sea, the mean rainfall for seven years (1871-77), according to the 
observations of Mr Holmes, was 113 inches, and the range 80 
to 159 inches (see Home's Year in Fiji}. In discussing the 
origin of the arid-looking plains on the north or lee side of the 
island in Note 22, I have shown that the explanation is to be found 
not so much in the rainfall as in the dryness of the air as indicated 
by the relative humidity. 

The rainfall varies greatly in and around Vanua Levu, but there 
is little doubt that by far the greatest bulk of the rain is pre- 
cipitated on the upper weather slopes of the mountainous backbone 
of the island. Taviuni, which lies off its weather coast, is probably 
the wettest among the smaller islands of the group. In 1877, when 
80 inches were recorded by Mr. Holmes at Delanasau on the north 
side of Vanua Levu and 73 inches at Levuka in the island 
of Ovalau, 251 inches were measured in Taviuni at Ngara Walu 
564 feet above the sea ; and in 1875 the rainfall recorded at 
Taviuni was 212 inches, and at Delanasau 126 inches (Home). 

Fortunately, the Fijian islands have not been long enough 
occupied by the whites to produce much effect on the rainfall 
through the destruction of the forests. A significant warning, 
however, has been given in the vicinity of Levuka. The woods of 
the hills around the town, as we learn from Mr. Home, were cut 
down to prevent them from affording shelter to the unfriendly 
natives of the interior, the result being to reduce the number of 
rainy days in a few years from 256 to 149 per annum. 

The Tahitian rainfall. The annual rainfall of the coast 
districts of Tahiti is placed at about 50 inches (EncycL Brit. 
vol. 23) ; but, as is observed by Nadeaud and Drake del Castillo, the 
rain-clouds gather round the peaks, and the precipitation is much 
greater in the interior than at the " littoral," with a corresponding 
result in a striking difference between the vegetation of the two 
regions. Probably, therefore, the rainfall for the year on the wooded 
mountain slopes and at the heads of valleys where the vegetation is 
most luxuriant would be over 100, and perhaps as much as 150 
inches in places. (The annual rainfall in Rarotonga is, according 
to Cheeseman, about 90 inches.) 

It is evident that in the three groups of Hawaii, Fiji, and Tahiti, 
the rainfall varies greatly with situation and with elevation ; but 
the contrast is much greater in Hawaii than in Fiji. Thus there 
would be scarcely any place on the lee side of Vanua Levu where 



xix THE PHYSICAL CONDITIONS 217 

the average annual fall would be less than 80 or 90 inches, except 
perhaps in the Undu Promontory, whilst on the lava-bound coast 
of the west or lee side of Hawaii, it may be reduced to 20 inches 
and less. There is no doubt that this was to some extent the case 
in pre-European times, since Fiji must have possessed for ages, on 
the northern sides of the larger islands, its arid " talasinga " or 
" sun-burnt " plains ; and in the island of Hawaii there must have 
always been vast, scantily vegetated lava fields at the sea-border. 
It is probable, however, that it is in the older islands of the 
Hawaiian group, those where the volcanic forces have been long 
extinct, that the rainfall has been chiefly affected by deforestation. 
Speaking generally, in pre-European times the climatic conditions 
of the lower levels of the group, that is below 4,000 feet, which are 
alone comparable with Fiji, were less contrasted with the climatic 
conditions of the Fijian islands than they are at present. By reason 
of their great elevation, the Hawaiian islands present a mountain 
climate not found in Fiji, and scantily represented in Tahiti. It is, 
therefore, in the flora of the Hawaiian uplands that we should 
expect to find the great distinguishing feature between that group 
and Fiji. 

Summary of the Chapter. 

(1) Whilst the winds and the currents have been working 
tranquilly through the ages, bringing always the same vascular 
cryptogams and shore-plants to the Pacific islands, the bird has 
ever been a disturbing factor in the inland flora, and changes often 
of a revolutionary character have taken place from time to time 
within the forest-zone. 

(2) In the discussion of the inland plants of these islands, the 
Fijian, Tahitian and Hawaiian areas are taken as centres of develop- 
ment and dispersal, and as including the groups around. 

(3) On account of the contrast in physical conditions presented 
by these archipelagoes, differences with which some of the most 
distinctive features of the floras are to be connected, a com- 
parison of the islands from this standpoint is first necessary. 

(4) Since the largest islands of the Fijian and Hawaiian areas 
are from five to ten times the size of Tahiti, the largest island of 
the Tahitian region, we would expect to find in the two first-named 
groups a much more varied flora. 

(5) There are three huge mountain-masses in the Hawaiian 
group which rise to between 10,000 and 14,000 feet, and there is in 



218 A NATURALIST IN THE PACIFIC CHAP. 

the aggregate a large area elevated more than 4,000 feet above the 
sea. These elevated regions are almost unrepresented in the 
southern groups, the Fijian islands being only comparable with the 
lower levels of the Hawaiian islands below 4,000 feet, and the same 
is true of all the groups with the exception of a limited area in 
Tahiti, where the mountains reach a height of 7,300 feet, and of 
the solitary peak of Savaii in Samoa, which attains an altitude of 
5,400 feet. Thus the conditions for a high-level or mountain flora 
which exist in Hawaii are not to be found in Fiji, but slightly in 
Samoa, and to a limited extent in Tahiti. 

(6) From their position with regard to the equator and with 
reference to the trade-winds a great contrast between the climates 
of these three regions the Fijian, the Tahitian, and the Hawaiian 
is, as far as the islands agree in elevation, not to be expected, 
and in fact does not exist. The Fijian climate, however, is now 
warmer and more humid, and the general rainfall is greater than in 
the case of Hawaii, but it is probable that these differences were 
much less pronounced before the destruction of the Hawaiian 
forests, which has been in progress since the discovery of the 
group. 

(7) Anywhere around the coasts of the larger Fijian islands we 
might expect an annual rainfall of not less than 80 or 100 
inches. In the Hawaiian group the rainfall at the coast may be 
anything between 10 and 100 inches, but is generally less than 50 
inches. In Tahiti, at the coast, it is 50 inches. In all cases the 
rainfall increases greatly with elevation. In the Fijian mountains 
the rainfall probably varies between 200 and 300 inches. In the 
Hawaiian forest-zone it would range probably between 100 and 
200 inches, though this is probably exceeded in a few localities. 
In the Tahitian uplands it would doubtless exceed 100 inches and 
approach 150 inches. 

(8) Quite a different climate prevails on the lofty summits of 
Hawaii 13,000 to 14,000 feet above the sea. Here the snow lies in 
winter, and the mean annual temperature is only a few degrees 
above the freezing point, probably about 36 F. The difference 
between the mean summer and winter temperatures is very small,, 
and does not exceed five or six degrees. Water freezes here during 
nearly every night of the year. The daily variation of temperature 
is very large, the average being probably about thirty degrees. 
Great dryness of the air prevails, the average relative humidity in 
August, 1897, being about 43 per cent. There is but little rain. 
The sun shines fiercely, and the sky is usually clear. 



xix THE PHYSICAL CONDITIONS 219 

(9) All Pacific climates are represented in the Hawaiian moun- 
tains, that of Fiji on the lower slopes, that of New Zealand half 
way up, and that of the Antarctic islands on the summits. 

(10) When contrasting the floras of Fiji, Tahiti, and Hawaii, it 
will be necessary to restrict our comparison in the case of Hawaii 
to the lower slopes below 4,000 or 5,000 feet ; and we should expect 
the Hawaiian mountain flora to be scantily represented in Tahiti, 
and scarcely at all in Fiji and Samoa. 



CHAPTER XX 

THE EPOCHS IN THE FLORAL HISTORY OF THE PACIFIC 

ISLANDS 

THE AGE OF FERNS 

The epochs 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. 

Introductory Remarks 

IN the endeavour to follow the various stages in the floral history 
of the Pacific islands from the standpoint of plant-dispersal, a 
method is here adopted which is not often employed. The usual 
mode of making a general description of a flora is not intended to 
bring out its genesis in point of time. We describe the result of a 
long series of changes dating back to some unknown period, much 
as one might describe the present condition of a people without 
reference to their history ; and for obvious reasons rarely is an 
effort made to differentiate the epochs of the stocking of the 
region with its plants. The difficulties investing such a task in the 
case of a region situated within a continental area would be almost 
insuperable. With the oceanic groups of the Pacific such diffi- 
culties, though still very numerous, would at all events be fewer in 
number and less formidable in appearance. 

Taking my cue from the well-known instance of Krakatoa, it 
is here assumed that the earliest epoch is connected with the 
arrival of the cryptogamic flora (ferns, mosses, lichens, &c.) through 
the agency of the winds, and with the arrival of the littoral plants 



CH. xx THE AGE OF FERNS 221 

through the agency of the currents. The next era is represented 
by the genera now peculiar to each group, since it is implied that 
they have descended from the earliest phanerogams that established 
themselves in the group. The following epoch, which ends only 
with the arrival of man, is characterised by the genera found out- 
side the group ; and here different degrees of antiquity are indicated 
according as the genus is represented wholly or in part by peculiar 
species, or contains only species found in other regions. The 
following eight chapters will be devoted to the development of the 
method here briefly indicated. 

THE AGE OF FERNS. 

It was established by Dr. Treub in the case of Krakatoa that 
ferns and algae formed the earliest vegetation of this island after it 
had been completely stripped of all its plants in the great eruption 
of 1883. It is, therefore, but natural that the vascular cryptogams 
should first be dealt with in any discussion relating to the historical 
aspects of these floras. 

It has been before remarked that the epoch of ferns and lycopods, 
which began with the earliest stage in the island's floral history, 
may be regarded as extending to our own day. It is thus implied 
that the vascular cryptogams of those early times are yet brought 
there, and that, alike with the littoral plants, these ferns and lycopods 
have witnessed almost unchanged the great revolutions that have 
marked the history of the inland flowering plants, more particularly 
those of the forest flora. This, as I will show, is true in Hawaii, 
though only in a partial sense in comparison with the other island- 
groups of Fiji and Tahiti, since in Hawaii nearly half the ferns and 
lycopods are peculiar to that group, whilst in Fiji and Tahiti not 
more than 8 or 9 per cent, appear to be endemic. (Rarotonga, 
according to Cheeseman, possesses one new species amongst its 
seventy-two ferns and lycopods, and probably in this it is typical of 
the smaller elevated islands of Eastern Polynesia.) 

The large proportion of peculiar Hawaiian species is the central 
fact in the distribution of vascular cryptogams in the Hawaiian, 
Fijian, and Tahitian archipelagoes, and indeed in the Pacific islands ; 
and it is around this fact that much of the following discussion will 
lie. (For the data relating to the Tahitian region, I have almost 
exclusively followed Drake del Castillo.) 

On looking at the table given below, it will be noticed that 
whilst there are about the same number of species of ferns and 



222 



A NATURALIST IN THE PACIFIC 



CHAP. 



lycopods in the Tahitian and Hawaiian islands there are at least 
half as many again in Fiji. When we reflect that the total areas 
of the Fijian and Hawaiian groups are in each case about 7,000 
square miles and that the extent of the whole Tahitian region does 
not amount to 2,000 square miles, these facts acquire a fresh 
significance. Ferns and lycopods might, therefore, be expected to 
figure more largely in the Tahitian flora than in those of Fiji and 
Hawaii ; and this is indeed the case. When we examine the 
relative proportion of the vascular cryptogams to the indigenous 
flowering plants in each area we find that whilst in Hawaii they 
form about 18 per cent, of the total flora and in Fiji not much 
more than this (see Note 62), in Tahiti they constitute just a third. 
This excess of vascular cryptogams is reflected in the flora of the 
outlying groups, the proportion in Rarotonga being, according to 
Cheeseman, 30 per cent. It is, therefore, evident that in compari- 
son with the other groups Tahiti possesses a marked preponder- 
ance in ferns and lycopods. In this respect the Tahitian islands 
resemble those of Juan Fernandez, where judging from the data 
relating to the indigenous flora given in Hemsley's Botany of the 
Challenger Expedition, the proportion of vascular cryptogams 
amounts to between 30 and 38 per cent. 

But it has been already implied that the proportion of endemic 
species of ferns and lycopods is from four to five times as large in 
Hawaii as it is in Tahiti or Fiji. In Hawaii, therefore, there has been 
.a production of many new species, whilst in Fiji and Tahiti there 
has been a great rush of immigrants. " Formative energy " in 
Hawaii (to adopt an expression of Dr. Hillebrand) and " active 
colonisation " in Fiji and Tahiti, such would appear to be the most 
conspicuous features in the history of the vascular cryptogams of 
these three archipelagoes. 

In these floras it is, therefore, apparent that respecting the vas- 
cular cryptogams the average number of species in a genus does not 
supply a means of contrasting them. As indicated in the table, 

TABLE OF VASCULAR CRYPTOGAMS (FERNS AND LYCOPODS) IN THE GROUPS OF 
TAHITI, HAWAII, AND FIJI. (See note 63.) 



Group. 


Number of 
genera. 


Number of 
species. 


Species to 
a genus. 


Number of 
endemic 
species. 


Percentage of 
endemic 
species. 


Percentage of ferns 
and lycopods among 
the vascular plants. 


Tahiti 


38 


154 


4' 1 


13 


8 


33 


Hawaii 


29 


155 


5 '4 


70 


45 


18 


Fiji 


40 


237 


5 '9 


20 


8 


21 



xx THE AGE OF FERNS 223 

the fern and lycopod floras of Fiji and Hawaii are similar in this 
respect. Yet in each the average number of species to a genus has 
a separate significance. A genus may acquire its species through 
immigration, or they may arise from its formative energy within 
the particular area. The first principle has been largely dominant 
in Fiji, the last in Hawaii, and the resemblance between the 
average number of species in a genus in these two groups is to a 
large extent accidental. Between the vascular cryptogams of Fiji 
and Tahiti, however, such a comparison is legitimate ; and since 
the average formative energy is in these groups about the same, 
the difference is to be attributed to a lessened number of immi- 
grants into the Tahitian area. 

The results, so far mentioned, are in the main consistent with 
the geographical position and the degree of isolation of these three 
areas. From their proximity to the large continental islands of 
the Western Pacific, the Fijian islands would have readily received 
a great number of immigrants from the west, since the intervening 
sea is not over 500 miles in breadth. They lie in the track of the 
main line of migration into and across the South Pacific, a track 
which has been followed by flowering plants and animals as well as 
by aboriginal man. Assuming that the migration of the vascular 
cryptogams extended from Fiji eastward to Tahiti, fewer of the 
immigrants would reach the last-named group. Fewer still would 
reach the Hawaiian islands, which excluding the groups of low 
coral islands to the southward are cut off on all sides, whether from 
the Fiji-Samoan and Tahitian areas, from the coasts of North 
America, or from the regions north and west, by a breadth of 
ocean that is never less than 1,500 miles. 

That the main track of the ferns and lycopods across the South 
Pacific to Tahiti has been eastward there can be little doubt. This 
is indicated in the tables given by Drake del Castillo for Eastern 
Polynesia, and also by an analysis I have prepared of the distribu- 
tions that he gives for the species of the Tahitian region (see Note 
64). Out of the 154 species there are only two that belong exclu- 
sively to the American side of the Pacific ; whilst 58 are derived 
exclusively from the Asiatic side, and mainly from Indo-Malaya. 
The drift of the ferns and lycopods eastward from Fiji is also 
brought out in the number of Tahitian species common to Hawaii 
and Fiji. Of these about 76 per cent, are common to Fiji or to 
the groups around, and only 30 per cent, occur in Hawaii. The 
Tahitian species found in Hawaii occur also in Fiji with the excep- 
tion of two or three mountain species which have doubtless failed 



224 A NATURALIST IN THE PACIFIC CHAP. 

to find a suitable elevation in Fiji. These two or three mountain 
ferns and lycopods are probably the only vascular cryptogams 
possessed in common by Hawaii and Tahiti to the exclusion of 
other groups. (See Note 64.) 

The prevailing Indo-Malayan origin of the ferns and lycopods 
of the archipelagoes of the Fijian area (Fiji, Tonga, Samoa) is 
so well established in the writings of Seemann, Baker, Hemsley, 
Christ, and Burkill that there is no necessity to enter into details 
here. That the stream of vascular cryptogams to Hawaii has 
proceeded mainly from the Old World side of the Pacific is 
shown in the circumstance that of the eighty and odd species 
found outside the group nearly half are from the Asiatic side 
exclusively and only three from America alone, whilst about a 
fourth occur in both continents, and a fourth are confined to 
Polynesia. One point, says Dr. Hillebrand, comes out in strong 
relief, and that is " the great number of ferns scattered over the 
long track which leads from the Hawaiian islands through Polynesia 
and Malaysia to the east coast of tropical Africa." But he 
adds significantly that "it cannot be inferred from this fact that 
all the species in question have travelled eastward to find the 
terminus of their long migration on this group, unless the 
principle be established, that the formative energy of a species or 
genus be greatest at the circumference or farthest extremity of 
its area " (p. 542). 

Though evidently prepared to admit the general eastward 
trend of plants in the Pacific, Dr. Hillebrand (p. xxviii) puts 
forward in the case of the ferns the startling view that originally 
spores of a few simple species have been diffused over various 
countries and that they have there evolved on parallel lines 
" predetermined by the structure of the original immigrant " a series 
of higher forms, so that the same form might have been produced 
in two widely distant localities, as, for instance, in Ceylon and 
Hawaii. The editor, Mr. W. F. Hillebrand, gives good reasons for 
his belief that this does not represent the matured opinion of the 
author. It is, however, worth noting in this connection that 
Dr. Karl Mueller has advanced a similar view with respect to the 
lower orders of plants. (See a translation of his paper in Trans, 
and Proc. N. Z. Inst. Vol. 25.) Bearing in mind the known 
capacity of ferns for dispersal by the winds, an hypothesis of this 
kind, even if established, seems scarcely needed in the study of 
fern-dispersal. 

It is probable that many of the ferns and lycopods reached 



xx THE AGE OF FERNS 225 

Hawaii directly and not through South Polynesia. The mountain- 
ferns of this group could hardly have been received by that route, 
since, as is shown below, they do not as a rule occur in that 
region. 

Some other interesting relations present themselves in con- 
nection with the Hawaiian ferns and lycopods when we consider 
the distribution of its non-endemic species in the other two groups 
of Fiji and Tahiti. Out of these species, some eighty in all, not 
more than half are common to all three groups, and about two 
dozen have not been found either in Fiji or in Tahiti. Of these 
last quite half are mountain species in Hawaii, having their station 
at elevations exceeding those of the highest districts of Fiji and of 
the several islands of the Tahitian area, excepting the limited 
region comprised in the uplands of Tahiti itself. 

A glance at the list, given in Note 65 of some of the mountain 
ferns of Hawaii not recorded from Fiji and Tahiti will show that 
these species are very widely distributed. Ferns .and lycopods 
found in the Himalayas and in the Andes meet on the higher 
slopes of the lofty mountains of Hawaii and in no other of the 
less elevated island-groups of the open Pacific. This distribution 
of the vascular cryptogams thus foreshadows a principle that will 
come into prominence in the case of the flowering plants, namely, 
that difference in elevation has been an important factor in 
determining some of the contrasts between the Hawaiian, Fijian, 
and Tahitian floras. The contrasts here implied are those 
connected with the climatic conditions of station, since several 
plants of temperate - regions, such as Aspidium filix mas, 
Asplenium trichomanes, Asplenium adiantum nigrum, &c., 
that are at home in the highlands of Hawaii, do not occur in 
either Fiji or Tahiti. We can infer that widely ranging ferns 
and lycopods have been dispersed over the oceanic groups of 
the tropical Pacific with a fair degree of uniformity, and that 
any marked contrasts in their distribution may be attributed to 
considerable differences in the altitude of the islands. 

In appreciating such a conclusion, and in dealing with 
apparent exceptions to the rule, the relation between the vertical 
range of a species and its lateral distribution has to be considered. 
We find, for instance, that whilst the Common Bracken (Pteris 
aquilina) is a mountain plant in Hawaii, it occurs also in Fiji 
and Tahiti. Since, however, it is found all over the temperate 
and tropical regions, and has a vertical range in Hawaii of from 
800 to 8,000 feet, any difficulty in this respect is thus explained. 
VOL. II Q 



226 A NATURALIST IN THE PACIFIC CHAP. 

Aspidium aculeatum, a characteristic fern of temperate latitudes, 
seems at first to present a, difficulty, which, however, proves to be 
more apparent than real. Whilst it has been recorded from 
Hawaii at heightsipf 6,000 to 9,000 feet, and from Tahiti at 4,000 
feet, it has also 'been found in Fiji and Samoa ; but since it was 
not collected by Seemann in Fiji, it can scarcely be common, and 
Home seems only to have obtained it from the tops of mountains 
in Vanua Levu at an elevation of 1,800 feet. 

Up to this point the non-endemic ferns and lycopods have been 
chiefly discussed. We will now briefly deal with the probable 
cause of the relative preponderance of peculiar or endemic species 
in Hawaii as contrasted with Fiji and Tahiti. In this respect the 
Hawaiian islands, as remarked at the commencement of this 
chapter, come into sharp contrast with the other two groups ; but 
it would seem that the differentiation has rarely acquired a generic 
value (see Note 66). In this respect the age of ferns is markedly 
distinguished from the succeeding era, the age of the arborescent 
Compositae and of Tree-Lobelias, to which a large number of 
peculiar genera belong. This, according to my view, is to be 
attributed to the circumstance that whilst the dispersion of spores 
by the wind is probably as active in our own time as it was in the 
earliest stage of the floral history of Hawaii, the dispersion of 
seeds by birds, to which the flowering plants in the main originally 
owe their presence in this group, has been greatly influenced by 
the various changes that have affected the migration of birds over 
the Pacific, a subject discussed in later pages. 

Respecting the origin of the species of ferns and lycopods 
peculiar to Hawaii, it is first of importance to quote the remarks 
of Dr. Hillebrand on the subject. Speaking of the whole flora 
(p. xxv), but evidently with the ferns more especially in his mind, 
he says : " Nature here luxuriates in formative energy. Is it 
because the islands offer a great range of conditions of life ? Or is 
it because the leading genera are in their age of manhood, of 
greatest vigour ? Or is it because the number of types which here 
come into play is limited, and, therefore, the area offered to their 
development comparatively great and varied ? " It is deeply to 
be regretted that sickness and death intervened before the author 
was able to give to the world his matured views on the very 
important points here raised. Yet they are much the same 
questions that man is ever putting to the life around him. There 
is the same querulous note that we find in all, the question that 
begins, the question that ends, and the reply that never comes. 



xx THE AGE OF FERNS 227 

" The evolution theory (writes Dr. Hillebrand, p. xxix) could 
hardly find a more favourable field for observation than an isolated 
island-group in mid-ocean, large enough to have produced a number 
of original forms, and at the same time so diversified in conditions 
of temperature, humidity, and atmospheric currents as to admit an 
extraordinary development in nearly every direction of vegetable 
morphology, uninfluenced by intercrossing with foreign elements." 
Isolation thus admittedly offers the preliminary determining or 
favouring conditions. This is directly indicated by the fact that 
Hawaii possesses fewer genera of ferns and lycopods than either 
Fiji or Tahiti, notwithstanding that it has the same area as Fiji, 
and is in extent three or four times the size of the whole Tahitian 
area. One effect of isolation in Hawaii has, therefore, been greater 
room for the development of new forms. It has, however, already 
been remarked that the islands of the Fijian area are much less 
isolated than those of the Hawaiian group, and that in consequence 
the free immigration possible in the one group has been checked 
in the other. Fiji possesses in respect to vascular cryptogams at 
least half as many species again as Hawaii, but Hawaii has three 
or four times the number of peculiar species. Yet before this great 
contrast can be ascribed to different degrees of isolation, it is 
necessary to exclude another possible cause presented by the 
greater range of life-conditions in Hawaii. It is possible that all 
the Hawaiian peculiar species may belong to the higher levels, 
elevations, as before shown, not represented in the Fijian islands, 
which correspond only to the lowlands of Hawaii, that is, to levels 
below 4,000 feet. If this is the case, the contrast between Fiji and 
Hawaii would be connected mainly with a difference in life- 
conditions, and, however potent the isolating influences might have 
been in Hawaii, they could hardly have been concerned with this 
striking difference. 

In order to determine this point, I went carefully through the 
account given by Hillebrand of the Hawaiian ferns and lycopods, 
noting the altitudes there given, and making use of the maps and 
of my own local knowledge of the islands of Oahu and Hawaii, 
where the elevation is neither directly nor indirectly implied. As 
a result, I found that out of sixty-six endemic species available for 
my purpose, forty-seven had their stations at levels below 4,000 feet, 
that is in the region corresponding to Fiji, and nineteen at eleva- 
tions exceeding this height. This, however, did not finally decide 
the question, since the proportion of endemic species may be much 
smaller in the region below 4,000 feet than in that above it. I, 

Q 2 



228 A NATURALIST IN THE PACIFIC CHAP. 

therefore, went over the ground again, and found, as shown in the 
table below, that the percentages of peculiar species amongst the 
total available for my use were not very far apart, 58 per cent, for 
the upper region and 43 per cent, for the lower region. 

DISTRIBUTION OF THE HAWAIIAN FERNS AND LYCOPODS ABOVE AND BELOW 

4,000 FEET. 





Number. 


Endemic. 


Percentage of endemic species. 


Species below 4,000 feet 


110 


47 


43 


above ,, 


33 


19 


58 



From the above it would appear that although the process of 
species-production in the Hawaiian islands has seemingly been 
rather more active above than below 4,000 feet, if we were to 
compare the entire vascular cryptogamic flora of Fiji with that of 
the corresponding lower levels of the Hawaiian group we should 
obtain much the same contrast in the proportion of peculiar species 
that we obtained when comparing all the ferns and lycopods of 
both groups. In other words, if we were to restrict our com- 
parison with Fiji, and I may add Tahiti, to that lower portion of 
Hawaii that corresponds in elevation, we should not get results 
very different from those to be obtained by including the Hawaiian 
upland regions as well. 

We are, I think, on these grounds justified in assuming that the 
relatively great development of new species of ferns and lycopods 
in Hawaii as contrasted with Fiji is not to be connected with the 
greater elevation of those islands. The only thing that we have 
been able to associate with the greater altitude of the Hawaiian 
Islands, and the consequent greater range of climatic conditions, 
when contrasting the Fijian and Hawaiian vascular cryptogams, is 
the 'occurrence of a number of peculiar mountain species and of 
wide-ranging temperate species that are found in the uplands of 
Hawaii, but not in the less elevated islands of Fiji. 

On the whole, therefore, it is to be inferred that the greater 
display of formative power among the ferns and lycopods of the 
Hawaiian Islands is in great part to be associated with the isolation 
of this group as compared with those of Fiji and Tahiti. The 
indications supplied by the vascular cryptogams resemble in kind 
those we shall obtain from the study of the flowering plants, but 
there is this important distinction. In formative power, as shown 



xx THE AGE OF FERNS 229 

in the development of new specific and generic types, the Hawaiian 
vascular cryptogams are far exceeded by the flowering plants where 
the proportion of endemic species amounts to 80 per cent. We have 
no reason to believe that the winds, to which the ferns and lycopods 
chiefly owe their dispersal, are less effective now in carrying their 
spores than they were in the earliest era of the floral history of 
Hawaii or in the intervening periods. In the course of ages the 
winds have been more uniform in their action as plant-dispersers 
even than the currents, and certainly far more than birds. 

On the other hand, in the case of the Hawaiian flowering plants 
that depend on the varying influence of the migrant bird, the 
agency of dispersal has often been suspended altogether, and far 
greater differentiation or departure from the original type has 
resulted, the amount of change often reaching to the value of 
a generic distinction. It is a question, however, whether the 
isolation of the Hawaiian Islands is to be entirely connected with 
their mid-oceanic position. It will be shown in Chapter XXXIII. 
that effects almost as great have been produced in continental 
regions and in continental islands, and that the isolated situation of 
Hawaii has not induced but has intensified these results. In the 
later eras of plant-life a process of segregation has been ever active 
throughout the tropical world whether in the case of an elevated 
oceanic island or of a mid-continental mountain. 

The following are some of the principal points that have been 
emphasised in the foregoing discussion of the ferns and lycopods of 
the Hawaiian, Fijian, and Tahitian Islands : 

(a} In all three groups the vascular cryptogams (ferns and 
lycopods) have been largely supplied from the warmer regions 
of the Old World. But whilst in the South Pacific the migration 
has been mainly from Fiji eastward to Tahiti, it is probable 
that Hawaii in the North Pacific has been in part independently 
stocked. 

() Whilst in Hawaii many peculiar species of ferns and 
lycopods have been developed, in Fiji and Tahiti there have been 
comparatively few. 

(<;) Whilst there has been more or less free immigration into 
Fiji and Tahiti there has been comparative isolation in Hawaii. 
Though the areas of the Fijian and Hawaiian archipelagoes are 
about the same, Fiji possesses at least half as many species 
again as Hawaii ; but Hawaii owns three or four times the number 
of peculiar species. 

(d) Though the land-area of the Tahitian region does not 



230 A NATURALIST IN THE PACIFIC CH. xx 

exceed a fourth part of that of Hawaii, it has the same number of 
species. The Tahitian islands therefore display a predominance of 
ferns and lycopods. 

(e) The non-effective influence of the greater elevation of the 
Hawaiian Islands on its preponderance of peculiar species is shown 
by comparing all the ferns and lycopods of the Fijian and Tahitian 
Islands with those of the corresponding lower levels of the Hawaiian 
Islands, when we find much the same contrast exhibited in the 
number of peculiar species. 

00 Whilst a large proportion of the ferns and lycopods are 
common to all three groups, Hawaii possesses a number of 
mountain species, widely distributed in temperate regions and on 
the higher levels of mountainous areas in the tropics, that are not 
found either in Fiji or in Tahiti. Their absence from these two 
groups is due to the insufficient elevation of the islands and to the 
non-existence there of extensive areas of any altitude. 

(g) The agency of the winds in dispersing the spores of ferns 
and lycopods has been relatively uniform through the ages when 
compared with the varying agency of the migrant bird, to which 
the flowering plants mainly owe their distribution. Thus it is that 
in the Pacific islands the vascular cryptogams have experienced 
much less differentiation than the flowering plants, though as a rule 
far older denizens of the islands. Yet we cannot doubt that the 
same principle has been at work in both cases, the difference 
arising in the instance of the flowering plants from the interrupted 
and often suspended agency of birds in the work of dispersal. 

(h} It is a question whether there is not something more 
concerned in the isolation of the Hawaiian group than its mid- 
oceanic position, since effects almost as great have been produced 
in continental regions. 



CHAPTER XXI 
THE ERAS OF THE FLOWERING PLANTS 

THE AGE OF COMPOSITES. 

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 Composite. 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 Compositse 
antedates the emergence of the island-groups of the Fijian region at the 
close of the Tertiary period. Summary. 

The Endemism of the Pacific Island Floras. 

As far as the production of new species is concerned, the 
Hawaiian group presents the same contrast with the Fijian and 
Tahitian groups in respect of the flowering plants that it does as 
regards the ferns and lycopods. The proportion of endemic species, 
after excluding all introduced plants, is in Hawaii 80 per cent, in 
Fiji about 50 per cent., and in Tahiti 35 per cent, (see Table A). 
The same contrast is also displayed in the number of peculiar 
genera. In Hawaii there are, according to Dr. Hillebrand, 37 or 
38, and in Fiji Dr. Seemann discovered 16; whilst, as we learn 
from Drake del Castillo, there are only 3 or 4 in the Tahitian 
Islands. (As will be pointed out later on, these numbers for Fiji 
and Hawaii have to be reduced, but the general inference to be 
drawn from them is not materially affected ; see Table B.) 

But if we look at the accompanying table (Table B) we notice 
that the flora of Hawaii is sharply contrasted with those of Fiji 
and Tahiti not only in the large proportion of endemic genera, but 
also in the large number of non-endemic genera with peculiar 



232 



A NATURALIST IN THE PACIFIC 



CHAP. 



species, and in the small proportion of genera possessing no 
peculiar species. There is an endemic element of greater or less 
degree in about 70 per cent, of the Hawaiian genera, whilst in Fiji 
only about 53 per cent, and in Tahiti as few as 34 per cent, of the 
genera contain to a varying extent peculiar species. Another 
feature brought out in this table is the relative poverty of genera 
in the Hawaiian Islands. Fiji, though about the same size as 
Hawaii, contains nearly half as many genera again, whilst the 
islands of the Tahitian region, which in the aggregate amount to 
only one-third or one-fourth of the area of the islands of Hawaii, 
possess nearly as many genera. 

TABLE A (FLOWERING PLANTS). 

Proportions of Endemic Species in the Hawaiian, Fijian, and Tahitian floras, with those 
for Samoa, Tonga, and Rarotonga added. 



Groups. 


Number of species. 


Number of endemic species. 


Percentage of endemic species. 


Hawaii 


686 


546 


80 


Fiji .. 


rs. 617 


/2S8 


(47 




\ H. 1086 


\620 


1 57 


Tahiti 


315 


112 


35 


Samoa 


326 


1 10 


34 


Tonga 


285 


17 


6 


Rarotonga 
Island ... 


140 


17 


12 



Remarks. The materials for this table have been obtained 
from the works of Hillebrand for Hawaii, Seemann and Home for 
Fiji, Drake del Castillo for Tahiti, Reinecke for Samoa, Hemsley 
and Burkill for Tonga, and Cheeseman for Rarotonga. The two 
estimates for Fiji are marked S. for Seemann and H. for Home, 
the last being a rough preliminary computation made by Home 
himself. 

The results given are only to be considered as approximations 
liable to emendation, but as regards the proportion of endemic 
species in the several groups they no doubt illustrate fairly well the 
relative degree of endemism in the various archipelagoes. The 
results for Samoa, Tonga, and Rarotonga are merely added in 
order to enable a comparison to be made with sub-groups of a 



XXI 



THE AGE OF COMPOSITE 



233 



region and with solitary islands, the Hawaiian, Fijian, and Tahitian 
groups being regarded as the three principal centres of plant-life 
in the open Pacific. 

All plants introduced by the aborigines and the white man are 
excluded. In so doing, I have mainly followed Seemann, a safe 
guide in all matters relating to weeds and to cultivated plants. 
The flora of a Pacific island thus treated undergoes serious diminu- 
tion in its extent. In the case of the Rarotonga flora, for example, 
which according to Cheeseman includes about 260 flowering plants, 
the number of truly indigenous plants, in the sense here implied, is 
only 140. Though this is an extreme case, it will serve to illustrate 
the principle here followed. 

TABLE B (FLOWERING PLANTS). 

Comparison of the Hawaiian, Fijian^ aud Tahitian genera. (All genera containing 
introduced plants entirely are excluded, ) 



Group. 


Non-endemic genera. 


Endemic 
genera. 


Total. 


No endemic 
species. 


Some species 
endemic, some 
not. 


All species 
endemic. 


Hawaii 


70(31) 


30(13) 


95 (43) 


28(13) 


223 (100) 


Fiji { 


S. 150(47) 
H. 162 (47) 


s. 74(23) 

H. 80(23) 


S. 87 (27) : S. 10 (3) 
H. 94 (27) H. 10 (3) 


S. 321 (ioo) 
H. 346 (ioo) 


Tahiti 
(Eastern 
Polynesia) 


125 (66) 


21(11) 


40 (21) 


4 (2) 


190(100) 



Remarks. The figures in brackets are percentages. S. = See- 
mann, H. = Horne and Seemann. 

In the construction of this table, Hillebrand, Seemann, and 
Drake del Castillo have been mainly followed, except with regard 
to the endemic genera for Hawaii and Fiji. In this respect the 
Index Kewensis has been largely consulted as well as Engler's 
publications, as indicated in the text. Hillebrand's total of nearly 
forty Hawaiian peculiar genera and Seemann's total of sixteen for 
Fiji have thus been considerably reduced. The two results given 
for Fiji are those of Seemann alone and with Home superadded. 
Home discovered, according to Hemsley, no new genera, but several 
genera from outside regions were added to the Fijian flora. Taking 
them as twenty-five (two-thirds of his own computation), I have 



234 A NATURALIST IN THE PACIFIC CHAP. 

apportioned them as in Seemann's results. The Tahitian region 
here includes Eastern Polynesia. 

It is necessary before proceeding further to obtain a correct 
idea of the significance of a large endemic element in the phanero- 
gamic flora of a Pacific archipelago. We have therefore at the out- 
set to inquire whether it is indicative of isolation or of antiquity. 
If the number of peculiar genera is to be regarded as the test of the 
relative antiquity of different Pacific floras and, by implication, of 
the islands to which they belong, these three groups, as shown in 
Table B, would arrange themselves in the following order, namely, 
Hawaii, Fiji, Tahiti. This test might be reliable if the several 
groups were in the same condition of isolation. Since, however, 
as we have previously seen, the Fijian Islands still enjoy a fairly 
free communication with the islands westward, whilst the Hawaiian 
group is largely cut off, it is apparent that the tendency to generic 
differentiation in Fiji might have been often swamped by immigra- 
tion, and that Fiji with its much smaller number of endemic genera 
may even be older than Hawaii. This objection does not apply 
quite as forcibly to a comparison between Hawaii and Tahiti, yet 
for reasons before given it may be regarded as sufficient to negative 
any inferences concerned with relative antiquity. 

On account, therefore, of the great differences in the degree of 
isolation of these three groups, we cannot be guided in our esti- 
mation of the relative antiquity of their floras by their number 
of peculiar genera. With the evidence at our disposal we are 
compelled to accept the view, which indeed a single glance at a 
map would suggest, that the number or proportion of endemic 
genera is to be connected with the degree of isolation. Whether a 
parallelism can be traced in the original stocking of these groups 
with their earliest flowering-plants is a matter that can only be 
elucidated by a further analysis of the peculiar genera. 

SYNOPSIS OF THE ERAS OF THE FLOWERING PLANTS IN THE 
TROPICAL PACIFIC. 

A. The Era of the Endemic Genera. Mostly American in 
their affinities. Represented particularly by Compositse and 
Lobeliaceae. 

B. The Era of Non-Endemic Genera. 

(i) The mountain genera, either cosmopolitan in temperate 
latitudes or derived from the New Zealand or the 
Antarctic flora. Mostly represented in Hawaii. 



xxi THE AGE OF COMPOSITE 235 

(2) The genera forming the low-level flora of Hawaii 
below 4,000 or 5,000 feet and composing almost the 
entire floras of the Fijian and Tahitian regions. Pre- 
dominantly Indo-Malayan. 

(a) The age of general dispersal over the tropical Pacific, 
the genera with only peculiar species being first 
treated, and afterwards those possessing a non- 
endemic element. 

(b) The age of local dispersal over the tropical Pacific. 

THE FIRST ERA OF THE FLOWERING PLANTS, BEING THE 
AGE OF THE ENDEMIC GENERA. 

With the above preliminary remarks I pass on to the next 
stage in the history of the stocking of these islands with their 
plants. The age of the ferns and lycopods is left behind, and it 
is assumed that the next era is mainly indicated by those genera 
of phanerogams that are now peculiar to their respective groups. 
In this connection by far the most interesting of the three regions, 
the Hawaiian, the Tahitian or East Polynesian, and the Fijian, is 
that of Hawaii, which, as before observed, is distinguished from the 
groups of the Fijian and Tahitian regions, or, in other words, from 
all the oceanic archipelagoes of the tropical Pacific, by its large 
number of endemic genera. 

Peculiar genera of shrubby and arborescent Compositae and of 
arborescent Lobeliaceae form the most striking characteristics of the 
endemic genera, and therefore of the ancient flora of Hawaii. It is 
in this connection of singular interest to remark that of the three 
endemic genera of the Tahitian flora one is an arborescent genus of 
the Compositae, and the other two are shrubby genera of the 
Lobeliaceae. There are, therefore, indications here of an ancient 
insular flora of the Pacific, characterised mainly by the prevalence 
of Compositae and Lobeliaceae. It is, however, remarkable that 
not only are no endemic genera of these orders known from Fiji or 
from the adjacent groups of Samoa and Tonga, but that the 
Lobeliaceae are not represented at all, whilst amongst the Fijian 
Compositae, with the exception of Lagenophora, the genera display 
no endemic element as far as the data at my disposal indicate. 

The problem we are brought face to face with is clearly stated 
by Mr. Hemsley in the Introduction to the Botany of the Chal- 
lenger Expedition (p. 68). " In Polynesia as elsewhere," he re- 
marks, " the Compositae mere particularly are perplexing to the 



236 A NATURALIST IN THE PACIFIC CHAP. 

botanical geographer, for although they have their greatest affinities 
in America, as well as the sub-arboreous Lobeliaceae, so numerous 
in the Sandwich Islands, yet the bulk of the vegetation seems to 
have been derived from the Australo- Asiatic region." 

In attempting to approach this problem I do so from the stand- 
point of dispersal. There are so many intricate questions bound 
up with the systematic position of these genera that in dealing with 
them the student of plant-distribution would require the capacities 
and opportunities of the eminent botanist who dealt with the distri- 
bution of ten thousand species of Compositse. On such ground, 
therefore, and only under the guidance of others, I will lightly 
tread. 

THE ENDEMIC GENERA OF COMPOSITE. 

On account of their endemic character the peculiar genera of 
Compositae are regarded as belonging to the oldest era of the 
flowering plants of the island-groups lying in the tropical latitudes 
of the open Pacific. This is the view of Bentham, but it is, of 
course, the opinion that most botanists would arrive at with the 
facts before them. With the exception of the solitary Tahitian 
genus Fitchia, they are all restricted to the Hawaiian Islands, and 
nearly all are either shrubby or arborescent, the greatest height of 
25 to 30 feet being attained in the Tahitian genus and in Hespero- 
mannia of Hawaii. 

Nine Hawaiian genera are included in this era, though, strictly 
speaking, we ought only to concern ourselves with the six genera, 
Remya, Argyroxiphium, Wilkesia, Dubautia, Raillardia, and Hes- 
peromannia, since the other three, Tetramolopium, Lipochaeta, and 
Campylotheca, are only on the borderland of generic distinction. 
It is, however, necessary that we should include these three genera 
in our treatment of the Hawaiian endemic genera, more especially 
because they appear to have been the last arrivals of the early 
Compositae. They still display, as shown below, a very suggestive 
connection with the land of their birth, a circumstance that is of 
much importance in finally determining the source of the other 
strictly endemic genera, where the links with their original homes 
have been in most cases largely severed. 

It would, however, be quite out of place here to enter into any 
details into the affinities of these Hawaiian genera of Compositae, 
and I will limit myself here to such general conclusions as may be 
derived from the pages of Bentham, Hillebrand, Hemsley, and 



xxi THE AGE OF COMPOSITE 237 

other writers, and such as are in accordance with the facts of distri- 
bution given in the Index Kewensis. Most ancient of all are the 
genera Remya, Argyroxiphium, Wilkesia, and Hesperomannia, 
which, although belonging to tribes that only occur on the American 
continent, as in the Mexican region, stand quite isolated, and, as 
Dr. Hillebrand remarks, probably belong to the oldest denizens of 
the Hawaiian Islands. It is noteworthy that these four ancient 
genera only contain two species apiece, a circumstance that favours 
their priority in point of age. 

The American affinities, however, are not always of the charac- 
ter that we might have expected. Thus, it was remarked by Mr. 
Bentham that although the tribe Mutisiaceae attains a great de- 
velopment in South America, and especially in Chile, its only 
representative in the Pacific islands is the very rare arboreous 
Hesperomannia of Hawaii. 

Rather less isolated in character, and we would presume there- 
fore of somewhat less antiquity, are the two closely allied genera 
of Raillardia and Dubautia, which have a close relative in Raillar- 
della of the Sierra Nevada in California. Then we come to the 
three genera, Tetramolopium, Lipochaeta, and Campylotheca, that, 
being still in touch with the world outside, may be regarded as 
the latest arrivals of the early genera of the Compositae. Tetramo- 
lopium, concerning which botanists were unable to agree, would 
seem, according to the Index Kewensis, to possess Mexican and 
Ecuadorian as well as Hawaiian species. Lipochaeta, nearly re- 
lated to other American genera, contains a dozen species, of which 
eleven are found only in Hawaii, whilst the twelfth occurs, according 
to the Index Kewensis, in California, and, according to Dr. Hille- 
brand, in the Galapagos group. Of the generic value of Campylo- 
theca there seems a doubt, and its distinctness is scarcely recog- 
nised in the Index Kewensis. It is, however, closely allied to 
Coreopsis, an American genus represented, according to Drake del 
Castillo, in the Marquesas. 

In the Tahitian region, that is to say in Eastern Polynesia, the 
genus Fitchia alone belongs to the early age of the Compositae, so 
characteristic of Hawaii. Indications of the former widespread 
range of the genus over this region of the South Pacific are afforded 
by its being now represented by two species in Tahiti and by one 
species in Rarotonga, localities nearly 700 miles apart. It was 
thus regarded by Bentham, who saw in it a solitary remnant of the 
ancient South Pacific flora. Like the Hawaiian genera, as shown 
below, it is often restricted to the higher levels. Botanists differ 



238 A NATURALIST IN THE PACIFIC CHAP. 

about its affinities, and a discussion of the subject will be found 
on pages 20 and 66 of the Introduction to the Botany of the 
Challenger Expedition. 

The restriction of these ancient genera of the Polynesian 
Compositae to the upland regions is of some interest. " The pre- 
ponderance of Compositae among the high-level plants obtains 
almost throughout the world." This observation was made by 
Mr. Hemsley in connection with the flora of the highlands of Tibet 
{Journ. Linn. Soc. Bot. vol. 35, 1902), where the Compositae 
constitute about 19 per cent, of the flowering plants ; and I may 
remark in passing that, according to Mr. Ball, one of the most con- 
spicuous elements in point of frequency in the higher flora of the 
Great Atlas is presented by the Compositse which make up between 
12 and 13 per cent, of the whole flora (Hooker and Ball's Marocco 
aud the Great Atlas]. This feature of alpine floras is brought into 
great prominence in Schimper's recent book on Plant Geography. 

Some of the most lasting reminiscences that the naturalist will 
bear away with him from the highlands of Hawaii are connected 
with the Compositae. Those who have ascended the mountains of 
Mauna Kea and Mauna Loa, will remember that amongst the last 
plants occurring above the forest zone, and scattered about on the 
ancient lava fields at elevations exceeding 10,000 feet above the 
sea, are species of Raillardia and the beautiful "Ahinahina" 
(Argyroxiphium). It is, however, in the open, scantily wooded 
region, elevated 6,000 to 9,000 feet, and lying between the true 
forest zone below and the bare lava slopes above, that the shrubby 
and arborescent Compositae of the large island of Hawaii are most 
at home. Such regions, as Hillebrand well describes (p. xxiv), are 
characterised by stunted trees, chiefly Sophora, Cyathodes, 
Myoporum, and others, associated with arborescent Raillardiae of 
the order of Compositae. Between them luxuriate other shrubby 
Compositae of the genera Raillardia, Dubautia, Campylotheca, and 
Artemisia, together with Strawberries, Raspberries, and species of 
Vaccinium. 

Botanists have not given us much account of the associates of 
the interesting genus Fitchia on the uplands of Tahiti. We learn, 
however, from Nadeaud that in his time these Composite trees and 
shrubs were spread over the higher region of the island of Tahiti 
above 800 and 1,000 metres. Cheeseman, to whom we are indebted 
for the discovery and the description of the Rarotongan species, 
tells us that this tree, which attains a height of 25 feet in the 
sheltered valleys, and is much dwarfed on the exposed ridges and 



XXI 



THE AGE OF COMPOSITE 239 



hill-tops, often forms the greater part of the forest above 500 feet, 
and reaches the highest peaks of the island (2,250 feet). 

In discussing the probable mode of dispersal of these early 
Composite plants of the Pacific we shall be treading on somewhat 
debatable ground. We will, however, point out that the mere 
possession of structures that could be utilised for dispersal of the 
seeds is not the only important question here involved. If we could 
demonstrate that all these genera possess exceptional capacities for 
distribution over the ocean, we should prove too much, since the 
process has been in the main suspended for ages. If, on the other 
side, it could be shown that their fruits are not at all suited for 
such dispersal, we should prove too little, since the ancestors of 
these genera must have been transported to these islands in some 
fashion or other. This clearly indicates that other important 
factors have also come into play in determining the distribution of 
the early Compositae of the Pacific islands. 

It was long ago pointed out by De Candolle that the possession 
of a pappus does not, as a rule, increase the area of a Composite 
plant, although as regards hooks and barbed appendages, such as 
occur in Bidens, the greater areas of the plants thus provided may 
be, as he thought, in some measure explained. Even in respect to 
hooks and barbs it would be easy to point to cases where, as 
Bentham remarks, unusual powers of adherence are by no means 
indicative of wide dispersal in all cases. In any event it will be 
also incumbent on us to explain why these genera no longer possess 
facilities for distribution. This suspension of the means of dis- 
persal is not, however, peculiar to the age of the endemic genera of 
the Pacific islands. It is a character but in a less degree of the 
succeeding age, the age of genera found outside the group, but 
represented within it by endemic species ; and from this we may 
suspect that we have had in operation in the Pacific an influence, 
far-reaching both in time and space, to which the agencies of 
dispersal have been compelled to adapt themselves, an influence 
which has acted as a distributor of the distributing agencies. 

Coming to the fitness for dispersal of the achenes of the early 
Composite genera of the Pacific islands, it will be assumed that 
they have been, as a general rule, transported in birds' plumfage. 
The fruits are usually 2'5 to 12 millimetres ( T V to J inch) in length, 
and are provided either with a ,pappus of soft or stiff bristles, or 
with awns or teeth, but these appendages vary much in size in the 
different genera and in different species of the same genus. The 
instance of Lipochaeta is especially significant as indicating the 



2 4 o A NATURALIST IN THE PACIFIC CHAP. 

alterations which the appendages of the achene may have undergone 
in the cases of other genera. With most species there are usually 
two or three teeth or short awns, but in some species these are 
obsolete, and in others they are long and stout. 

Bearing these facts in mind we should hesitate to rely too much 
on the present condition of the achenes in the other genera as an 
indication of the fitness for dispersal of the fruits of their ancestors. 
In one genus, Carnpylotheca, which may be regarded as among the 
youngest of the genera, the achenes are provided with barbed or 
hooked awns which cause them to adhere as tenaciously to one's 
clothes as in the case of those of Bidens, an allied genus. In 
Fitchia, the Tahitian genus, which may be looked upon as one of 
the oldest of the Pacific genera of Compositae, the achene is 
furnished with two long awns or setae, which, as Drake del Castillo 
observes, recall those of Bidens. The achenes of the other Hawaiian 
genera, as regards their fitness for dispersal in plumage, may be 
said, to give less definite indications. In some, as in Dubautia and 
Raillardia, there is a typical pappus often to twenty long hair-like 
bristles. In others again, as in Wilkesia and Argyroxiphium, the 
pappus is much reduced, and in some species of Lipochaeta it is, as 
above remarked, quite obsolete. 

The chances of the achenes of the parent plants having in 
some cases been originally transported to the islands in the 
plumage of birds would be increased by a bird making its nest of 
the plant-materials or amongst the plants themselves, or by its 
pecking at the fruit-heads. In our own time different species of 
the grouse family on the slopes of the Californian and Columbian 
mountains make their nests on the ground under the shade of 
Artemisia bushes and find a portion of their sustenance in their 
fruits. Artemisias also form one of the features of the vegetation of 
the Hawaiian uplands ; but since they present only specific 
differentiation they are referred to a later era. Yet it will be on the 
slopes of the Rocky Mountains and of the Californian Sierra 
Nevada, amongst the " sage-brush " and the grouse, that we may 
have to stand when we look in thought across the Pacific towards 
far distant Hawaii and ask ourselves whence came its tree-like 
Raillardias, its shrubby Dubautias, its tall Wilkesias, and the 
silvery Ahinahinas (Argyroxiphium). 

It is possible that in some genera the achenes have, or had, a 
means of adhering to plumage through a " sticky " secretion, such 
as is sometimes found with Lagenophora, an Hawaiian genus of 
the next era, and also with the weed-plant Adenostemma viscosum ; 



xxi THE AGE OF COMPOSITE 241 

but this is a point that has not yet been investigated. Nor can we 
altogether exclude the chance of the achenes having in some cases 
been transported unharmed to Hawaii in a bird's stomach. The 
possibility of this has been above implied in the case of Artemisia ; 
and it is pointed out in Chapter XXXIII. that pigeons in Hawaii 
feed sometimes on the achenes of Compositae. The Hawaiian 
goose (Bernicla sandwicensis) lives, according to Mr. Dole, on 
Sonchus asper, an introduced plant, as well as on berries (Wilson's 
Aves Haivaiiensis}. There are numerous references of this nature 
in books about birds, and it should always be remembered that 
birds in pecking at the fruit-heads scatter the seeds on their 
feathers. (See Note 67.) 

From the foregoing remarks it may, I think, be inferred that 
the achenes of the ancestors of the original Composite genera of 
the Pacific islands were in all probability not unfitted for transport 
by birds, more especially in their plumage. Some of my readers, 
however, may express a doubt as to whether birds likely to disperse 
seeds would be found in any numbers at the great heights where 
some of the continental Compositae occur. But it is well known 
that birds of the grouse and partridge family frequent high levels 
in continental regions over much of the globe. Arborescent Com- 
positae are found at heights of 10,000 to 14,000 feet on the 
mountains of Central Africa ; and it should be noticed that Sir 
Harry Johnston observed " francolins " on the slopes of Ruwen- 
zori up to 13,000 feet (Uganda Protectorate, vol. I ; Trans. Linn. 
Soc. Bot., Ser. II. vol. 2). Sir Martin Conway in the Bolivian 
Andes found geese, ducks, gulls, snipe, &c., numerous in suitable 
places up to 17,000 feet (Journ. Roy. Geogr. Soc., 1899); whilst 
geese and teal were noticed by Sir Joseph Hooker and others at 
elevations of 17,000 feet in the mountains of Tibet (Hooker's 
Himalayan Journals ; Journ. Linn. Soc. Bot., vol. 35, p. 147). 
These are all birds, as shown in Chapter XXXIII., that are likely 
to disperse plants, and probably none more effectually than the 
goose, of which Hawaii possesses a particular variety or species. 
It may be remarked that geese, ducks, gulls, and other birds use 
Cotula plumosa in Kerguelen for making their nests (Dr. Kidder 
quoted by Mr. Dixon in his book on Birds' Nests). 

Sea-birds were probably the principal agents in carrying the 
aehenes of the early genera of the Compositae to Hawaii. Dr. 
Hillebrand attached importance to the tropic-bird (Phaethon) in 
the distribution of species flntrod., p. 30) ; and since these birds 
breed at the crater of Kilauea in Hawaii, 4,000 feet above the sea, 
VOL. II R 



242 A NATURALIST IN THE PACIFIC CHAP. 

and also high up in Tahiti (Moseley), its agency is not unlikely, 
I am inclined to think, however, that birds like the petrels and 
puffins, that in nesting burrow in the ground, choosing places where 
the vegetation is thickest, and where they would be likely to get 
seeds on their feathers, would be more efficient agents. This is 
the view expressed by Prof. Moseley in Wallace's Island Life, 
p. 250. He considered that albatrosses, petrels, and puffins have 
played a great part in the distribution of plants, and to some 
degree especially account for the otherwise difficult fact that widely 
distant islands in tropical seas have similar mountain plants. 
Birds, he says, that in high latitudes, as at Tristan da Cunha and 
Kerguelen, often burrow near the sea-level, in the tropics choose 
the mountains for their nesting-place ; and he refers to a puffin 
that nests on the top of one of the high mountains of Viti Levu at 
an altitude of 4,000 feet, to a petrel nesting among ferns at Tahiti 
at an elevation of 4,400 feet, and to another petrel breeding in like 
manner in the high mountains of Jamaica at a height of several 
thousand feet above the sea. He gives point to these interesting 
remarks, which might be supplemented by data from other parts of 
the world, by observing that it is not necessary that the same 
species should now cover the range of the plants concerned. The 
ancestor of the species might have carried the seeds, and the 
range of the genus is alone sufficient. It may be added that, as I 
have shown in Chapter XXXIII., sea-birds have been far more 
active agents in the distribution of plants than many people might 
imagine. The more recent observations of Ekstam in Spitzbergen 
have thrown considerable light on this subject. 

Having in the first place formed the opinion that the achenes 
of the early Hawaiian Composite are suited for dispersal by birds, 
and then shown that sea-birds were probably the principal agents, 
we are met with the curious difficulty that in the case of the early 
Hawaiian genera of Composite the complete suspension for ages 
of the means of dispersal is involved in the circumstances that 
these genera are confined to the Hawaiian group. We can attri- 
bute to the agency of existing sea-birds the occurrence of the 
genus Lagenophora in the uplands of Hawaii, on the mountain- 
tops of Fiji, and in Australia and New Zealand ; but the agency of 
birds as at present in operation does not assist us except indirectly 
in the case of the genera restricted to Hawaii or to Tahiti. Is it 
possible, we may inquire, to penetrate this mystery? Why, we 
may ask with Mr. Hemsley, has the agency ceased acting, and why 
have its operations been confined to the conveyance of seeds to 



xxi THE AGE OF COMPOSITE 243 

the islands and not from the islands as well (/;//;-. Bot. Chall. Exped.. 
p. 66) ? I need scarcely add that the same question presents itself 
with all the other peculiar genera of these islands, and in fact with 
endemic genera all over the world. What can be stranger, it may 
be remarked, than the limited distribution of the Pandanaceous 
genus Sararanga in the Western Pacific, although suited for 
dispersal by frugivorous birds. This is not, indeed, a special 
difficulty connected with oceanic islands ; it applies to the whole 
plant-world ; yet it is possible that, as it is exhibited by the Compo- 
sitae in these islands, we may be in a better position to grapple 
with the problem. But before doing so it will be requisite to look 
a little closer at these early Hawaiian genera of the Compositae. 

The distribution within the archipelago of the genera and 
species of the early Compositae of Hawaii is worthy of notice 
from the light it throws, not only on the relative antiquity of the 
genera, but also on the subsequent conditions of isolation. Of the 
nine genera here referred to five are distributed over most of the 
islands of the group. These include all the genera possessing a 
number of species, namely, Tetramolopium with seven species, 
Lipochaeta with eleven, Campylotheca with twelve, Dubautia with 
six, and Raillardia with twelve species. Of the four genera 
remaining all have only two species, and are restricted to two or 
three islands, Remya and Wilkesia being in both cases found in 
Kauai and Maui, whilst Argyroxiphium is confined to the adjacent 
islands of Maui and Hawaii, and Hesperomannia to those of Oahu, 
Lanai, and Maui. These four genera that are restricted to only 
two or three islands are the same before referred to as regarded 
by Hillebrand as the oldest, partly on account of their isolated 
generic position, and partly because in each case they only possess 
two species. 

Although the early Hawaiian Compositae were evidently 
originally transported to most of the islands of the group, it is 
noteworthy that their subsequent isolation from the rest of the 
world has in the later ages been repeated within the limits of the 
archipelago. Of the 56 species, all of which are now endemic, 
28, or just half, as shown in the table on the following page, are 
confined to a single island. Of the remainder, almost all are 
restricted to two or three adjacent islands. Hillebrand gives 
only a solitary species, Lipochaeta connata, as occurring in all 
the islands. This suspension, to a great extent, of the means of 
dispersal between the islands is also strikingly illustrated by the 
Lobeliaceae. 

R 2 



244 



A NATURALIST IN THE PACIFIC 



CHAP. 



We have only to mention the flora of Fiji and those of the 
adjacent groups of Samoa and Tonga to exclude them from any 
share in the early era of the Compositae in the Pacific. The pre- 
vailing adventitious character of the Fijian Compositae is indicated 
in the fact that the species of the majority of the genera are 
included by Seemann in his list of Fijian weeds. There are only 
one or two Fijian Compositae, such as the mountain species of 
Lagenophora and the littoral species of Wedelia, that merit the 
special attention of the student of dispersal. So also with Samoa, 
Reinecke enumerates eight species, of which six are weeds either 
of aboriginal or of European introduction, the others being the 
littoral Wedelia above alluded to, and a species of Blumea found 
also in Fiji. 

DISTRIBUTION OF THE ENDEMIC GENERA OF COMPOSITE IN THE HAWAIIAN 

ISLANDS. 



Genus. 


Distribution of the Species. 


Total. 

2 

7 
II 

12 

2 
2 

6 

12 
2 


One 

island. 


Two 

islands. 


Three 

islands. 


Four 
islands. 


General. 


Remya 


2 
I 

3 
5 

i 

2 

4 
9 

i 


4 
4 
4 

I 

I 

I 


2 

3 
3 

2 


2 


I 


Xetramolopium 


Lipochseta 


Campylotheca 




Wilkesia . 





Dubautia 


Raillardia 


Hesperomannia .. 






28 


15 


10 


2 


I 


56 



We have now, I venture to think, gone far to establish the 
existence of an early " Composite " flora with mainly American 
affinities in the Pacific islands, an ancient flora of which only the 
remnants now occur in the uplands of Hawaii, Tahiti, and Raro- 
tonga. That the achenes were originally transported in birds' 
plumage is, as we have seen, probable ; but we are still quite in 
the dark as to the causes of the subsequent suspension of the 
means of dispersal and of the resulting period of isolation, during 
which the original immigrant plants acquired their endemic 
characters. In our uncertainty, therefore, we will look to Fiji in 
the hope that in the absence of the early Compositae from that 



xxi THE AGE OF COMPOSITE 245 

group we may find a clue that will enable us to divest this problem 
of some of its difficulties. 

It might be at first considered that since these peculiar genera 
of Compositae occur in the higher levels of Hawaii and Tahiti 
their absence from Fiji might be connected with the relatively low 
altitude of those islands, a character that is concerned with the 
exclusion from the Fijian flora of many Hawaiian and Tahitian 
mountain plants (see Chapters XXIII. and XXIV.). But this view 
is at once negatived by the fact that Fitchia thrives in Rarotonga, 
an island which does riot far exceed 2,000 feet in elevation. It is 
negatived also by the extensive development of shrubby and 
arborescent Compositae in the Galapagos Islands, on the equator, 
in St. Helena in 16 South latitude, and in other tropical islands, 
which are less than, or do not exceed, the Fijian Islands in their 
altitude. 

During the age of the Compositae it is reasonable to suppose 
that the dispersal was general over the Pacific. The absence of 
genera indicating this era from the islands of the Fijian region, 
that is, from Fiji, Tonga, and Samoa, would become intelligible if 
these groups were submerged during this age of the general 
dispersal of the order over this ocean. In my volume on the 
geology of Vanua Levu in Fiji, I have shown that these island- 
groups of the Western Pacific emerged from the sea towards the 
close of the Tertiary period, a conclusion that would enable us to 
assign the age of the general dispersal of the Compositae over the 
tropical Pacific to an earlier portion of the same period. 

In order, however, to make further progress in the discussion of 
this difficult problem we are obliged to approach it from the out- 
side. We must in fact regard these genera from the standpoint of 
their position as members of the vast and ancient order of the 
Compositae. It is now more than thirty years since Mr. Bentham 
completed his remarkable memoir on the classification, history, 
and geographical distribution of the Compositae (Journal Linnean 
Society, Botany, London, Vol. 13, 1873). Like De Candolle, when 
dealing with the facts of distribution, he handled thousands of 
species, and as a result he drew certain inferences which are of 
prime importance to students of plant-dispersal. In his time the 
order included nearly 10,000 known species, and although this 
number has since no doubt been considerably increased, it is not 
likely that his main conclusions, in so far as they are free from 
purely hypothetical considerations, will be materially affected by 
the later discoveries. 



246 A NATURALIST IN THE PACIFIC CHAP. 

Accepting the antiquity of the order, and regarding it as 
probably dating far back in geological time, he observes that the 
evidence points to a very wide dispersion of its original stock at an 
early period. Africa, West America, and possibly Australia, 
possessed the order at the earliest recognisable stage. There 
must have existed, he contends, at this early period some means of 
reciprocal interchange of races between these regions. Then 
followed a stoppage of communication, or a suspension of the 
means of dispersal, between the tropical regions of the Old and 
New Worlds ; but long after communication was broken off in the 
warmer regions, it still existed, as he holds, between the alpine 
heights in those regions and also between the high northern 
latitudes of both hemispheres. Referring particularly to the 
Hawaiian Group, he considers that the large endemic element 
among the Compositae indicates that the ancient connection, 
whether with America or with Australasia, has been so long 
severed as not to have left a single unmodified common form. 
Fitchia, the Tahitian genus, as we have already remarked, is 
regarded as the only remnant of an ancient Composite flora in the 
tropical islands of the South Pacific. 

In the light of these reflections it will be interesting to glance 
at the general distribution of the shrubby and arborescent or woody 
Compositae. Mr. Hemsley, having generally discussed the subject, 
arrived at the conclusion that, " although they form so large a 
proportion of the floras of St. Helena, Juan Fernandez, the 
Sandwich Islands, and some other islands, they are not specially 
insular." There are scores of them, he goes on to say, in South 
America, Africa, Madagascar, India, Australia, and New Zealand 
from twenty to forty feet high, and more truly arboreous than the 
insular ones ; whilst nearly every sub-order has its arboreous 
representatives. He was, however, unable to form any definite 
opinion of the method of distribution of the woody Compositse. 
Taking those of St. Helena and Juan Fernandez, he observes that 
they are not more closely allied to the Compositse of the nearest 
continents than they are to those of more distant regions. The 
occurrence of arboreous Compositse, belonging in each case to 
different tribes, in so many remote oceanic islands, coupled with 
the distribution of the genera to which they bear the greatest 
affinity, seems, he observes, to indicate that they are the remains of 
very ancient types (Introd. Bot. Chall. Exped., pp. 19 24, 66, 68 ; 
also Parts ii. p. 61, and iii. p. 23). 

The further discussion of this subject would lead us into a wide 



xxi THE AGE OF COMPOSITE 247 

field of inquiry, quite beyond the scope of this work. There is, 
however, an inference that I think we may legitimately draw from 
geological evidence in this region. With respect to the antiquity 
of the woody Composite of the Pacific as illustrated by the 
endemic genera, both Mr. Bentham and Mr. Hemsley view them 
as belonging to ancient types. Mr. Wallace, in his Island Life^ a 
book that becomes more and more indispensable for the student of 
dispersal as years progress, dwells on the importance of these 
ancient Compositae in the floral history of the Pacific islands. We 
may look upon the Hawaiian Compositae, he remarks, as represent- 
ing the most ancient portion of the existing flora, carrying us back 
to a very remote period when the facilities for communication with 
America were greater than they are now. The date of this period 
of oceanic dispersal of the Compositae we can now approximately 
determine, since these plants are absent from the Fijian region, an 
area of submergence during the Tertiary era. Before the island- 
groups of the Fijian region had emerged towards the close of the 
Tertiary period the achenes of the early Compositae had been 
dispersed far and wide over the tropical Pacific. 

But this is not all that we can infer from the convergence 
of these independent lines of botanical and geological investiga- 
tion. Mr. Bentham observes that the tribes of the Compositae had 
acquired the essential characters now employed in classification 
before the dispersion of the order over the Pacific. Since this 
general dispersion took place, as we hold, during the Tertiary sub- 
mergence of the island-groups of West Polynesia (Fiji, Tonga, 
Samoa), it follows that the birth of the tribes of the Compositae 
antedates that period. If this interesting order could supply 
us with a " datum-mark " in the history of the Pacific floras, it 
would be stated in terms of the development of specific and generic 
characters, but not of those of a tribe. 



Summary of Chapter. 

(i) The Hawaiian Islands present the same contrast with the 
Fijian and Tahitian groups as regards the development of new 
species in the case of the flowering plants that they offer in 
the case of the vascular cryptogams (ferns and lycopods). But 
the contrast is intensified, and it is further emphasised as respecting 
the flowering plants by the evolution of a large number of endemic 
genera. 



248 A NATURALIST IN THE PACIFIC CHAP. 

(2) This great preponderance of peculiar species and genera in 
Hawaii is not to be connected with the relative antiquity of the 
group but with its degree of isolation. 

(3) The earliest stage of the flowering plants of the islands 
of Hawaii and of Eastern Polynesia (the Tahitian region) is 
indicated by the endemic genera, particularly those of the 
Composite and Lobeliaceae. Such genera are numerous in 
Hawaii, and occur also in the Tahitian region, as in Tahiti and 
Rarotonga ; but do not exist in the groups of the Fijian region 
(Fiji, Tonga, and Samoa). 

(4) The endemic genera of the Hawaiian Compositae are 
mainly American in their affinities. The relationship of the 
solitary Tahitian genus (Fitchia) is still a subject of discussion. 

(5) In the Hawaiian Islands, as well as in Tahiti and Raro- 
tonga, the plants of the endemic genera of Compositae are, as a rule, 
arborescent or shrubby ; and in the first two localities they are 
mainly restricted to the higher levels. 

(6) In discussing the mode of dispersal of the achenes of the 
original genera we have also to explain why the process of dis- 
persal has been in the main suspended. 

(7) It is shown that the achenes of these early Compositae were 
in all probability suited for dispersal in birds' plumage. 

(8) Yet the isolating influence that cut off these genera from 
the outside world has, in later ages, been active within the limits 
of the Hawaiian archipelago, with the result that half the species 
are not found in more than a single island. Inter-island dispersal 
has, therefore, been also largely suspended. 

(9) The absence of endemic genera of Compositae from Fiji, 
Tonga, and Samoa cannot be attributed to unsuitable climatic 
conditions connected with the relatively low elevation of those 
islands as contrasted with those of Hawaii, since a species of 
Fitchia abounds in Rarotonga, which is not far over 2,000 feet 
in elevation. Shrubby and arborescent Compositae of peculiar 
types also occur in the Galapagos and other tropical islands 
not more elevated than the Fijis. 

(10) These endemic genera are the remains of an ancient 
Composite flora in the islands of the tropical Pacific, and ages 
have elapsed since the severance of their connections with regions 
outside. 

(i i) According to Mr. Bentham the Compositae were distributed 
over Africa, West America, and possibly Australia, at an early 
period, but subsequent to the differentiation of the tribes of 



xxi THE AGE OF COMPOSITE 249 

the order. Some means of reciprocal interchange of races between 
these regions then existed. Then followed a suspension of the 
means of dispersal between the tropical regions of the Old and 
New Worlds except between the alpine heights of those latitudes. 
(12) It is inferred by the author of this volume that the general 
dispersion of the early Composite over the Pacific took place 
during the Tertiary submergence of the island-groups of the 
Fijian region (Fiji, Tonga, and Samoa), and that their absence 
from that region may be thus explained. At the time of this 
general dispersion, as above pointed out, the tribes of the 
Composite had been already differentiated. 



CHAPTER XXII 
THE ERA OF THE ENDEMIC GENERA (continued] 

THE COMPOSITE AND LOBELIACE/E (continued) 
THE AGE OF THE TREE-LOBELIAS 

The distribution of the arborescent Lobeliaceae. On the upper flanks of Ruwen- 
zori. The Lobeliaceas of the Hawaiian Islands. The Lobeliaceae of the 
Tahitian or East Polynesian region. The capacities for dispersal. The 
explanation of the absence of the early Lobeliaceae from West Polynesia. 
The other Hawaiian endemic genera. The Fijian endemic genera. 
Summary. 

THE Lobeliaceae rank with the Compositae in the prominence of 
their position in the early Pacific floras. Though absent, as far as 
is known, from Fiji, they are represented in Hawaii by 58 
species, all endemic and belonging to six genera, of which five are 
not found elsewhere. All possess, as Hillebrand remarks, a woody 
stem, by far the greater number being either tall shrubs, 5 or 6 feet 
high, or small trees, 10 to 20 feet or more in height. In the East 
Polynesian or Tahitian region, the order is represented by two 
genera containing in all five known species and restricted to those 
islands. One genus is common to the islands of Tahiti and 
Rarotonga, and the other is confined to Raiatea. The species may 
be shrubby or arborescent. 

It was for some time considered that the oceanic archipelagoes 
of the Pacific were the exclusive centres of these singular arbores- 
cent Lobeliacese (I am here quoting Baillon in his Natural History 
of Plants). And indeed this idea would receive some support from 
the circumstance that Dr. Hillebrand, in his work on Hawaii, says 
little or nothing about the affinities or general relations of plants 
which he enthusiastically termed " the pride of our flora." His 
death in 1886 deprived his work of its crowning piece, a discussion 



CH. xxn THE TREE-LOBELIAS 251 

of " the interesting questions of the origin and development of the 
Hawaiian flora " (see the Editor's Introduction, p. ix.). In no group 
of plants is this want more keenly felt than with the Lobeliaceae. 
Yet in his time the explorations had yet to be made that could set 
the student of plant-distribution on the road to investigate this 
problem. 

It was true, no doubt, that types analogous to those of the 
Hawaiian Lobeliaceae were known from the American and African 
continents. Thus Oliver in his Flora of Tropical Africa, published 
in 1877, gives an account of the species of Lobelia then known 
from the mountains of this region. The genus was, however, not 
entirely confined to mountainous districts, but it would almost 
seem that most of the high mountains of Equatorial Africa had 
their peculiar species, some of them being tree-like and others 
shrubby. Two mountain species were recorded from Abyssinia, 
one of them from an elevation of 11,000 to 13,000 feet and growing 
to a height of 12 to 15 feet, the other from an altitude of about 
8,000 feet ; another, Lobelia Deckenii, attaining a height of 4 feet, 
was recorded from the uplands of Kilimanjaro, 12,000 to 13,000 
feet above the sea, and yet another from the mountains of 
Fernando Po, at an altitude of 9,000 feet. So again, in the 
case of the American continent, Hemsley, writing in 1885 (Intr. 
Bot. ChalL Exped., p. 32), speaks of arborescent species of the 
American genera Centropogon, Siphocampylus, &c. ; and Baillon 
in his Natural History of Plants (Engl. edit. viii. 350) refers to the 
similar Tupas and Haynaldias from South America. But what 
the student of plant-distribution looked for was not merely the 
occurrence of " tree-lobelias " in other parts of the world, but also 
the reproduction of these wonderful plants under the same con- 
ditions and on the same scale as those familiar to him on the 
Hawaiian mountains. He has accordingly had to wait for the 
results of the more recent explorations of the mountains of Central 
Africa in order to obtain his wish. 

On the upper flanks of Ruwenzori, Kilimanjaro, and Kenya, at 
elevations of 9,000 to 13,000 feet and reaching to the snow-line, 
there flourish in boggy portions of the forest arborescent Lobeliaceae 
that attain a height of 15 or 20 feet. They have the habit some- 
times of a Dracaena and sometimes of an Aloe, and do not exhibit 
the branching trunks so characteristic of the Hawaiian genus of 
Clermontia. They all belong, however, to the genus Lobelia, and 
thus do not display the extensive differentiation of the endemic 
genera of Hawaii. Nor, apparently, has there been the same 



252 



A NATURALIST IN THE PACIFIC 



CHAP, 



degree of formative energy in the development of species, since 
only about half a dozen species are hitherto known. We find, 
however, produced on these lofty mountains of Equatorial Africa 
the same climatic conditions under which the arborescent Lobe- 
liaceae flourish in Hawaii, namely, the very humid atmosphere, 
the heavy rainfall, and the mild temperature ; and if there are 
important contrasts in their character and in the amount of differ- 
entiation which they have undergone in the two regions, the one a 
continental and the other an insular region, it will be from such 
contrasts that some of the most interesting results of this com- 
parison of a mountain of Central Africa with an island of the open 
Pacific will be ultimately derived (see Sir H. Johnston's Uganda 
Protectorate, 1902, and Kilimanjaro Expedition, 1886; also Trans, 
Linn. Soc. Bot.^ ser. 2, vol. 2, p. 341. 



THE LOBELIACEjE OF THE HAWAIIAN AND OF THE EAST POLYNESIAN OR 
TAHITIAN ISLANDS.* 

HAWAIIAN ISLANDS. 





<~ wi 








Nature of station. 


Genus. 


ol 

z& 


Distribution 
of genus. 


Distribution 
in the 
group. 


Height ot 
plant. 




Elevation. 


Station. 


Brighamia ... 


I 


Endemic. 


Molokai, 


5 to 12 feet. 


Islands not ex- 


Steep palis or 








Niihau. 




ceeding 3,500 


mountain gaps. 










feet. 




Lobelia 


5 


Non-endemic. ! General. 


4 to 6 feet. 


2,000 to 6,000 


Bridges, gulches 






i 




feet. 


and woods. 


Clermontia ... 


ii 


Endemic. General. 


Usually 10 to 


2,000 tO 6,000 


Open woods. 










20 feet, t 


feet. 




Rollandia 


6 


Endemic. 


Oahu. 


Usually 4 to 


Higher parts of 


Woods. 










6 feet, one 
species 10 to 


Oahu, which is 
4,000 feet high. 


i 










15 feet. 






Delissea 


7 


Endemic. 


General. 


5 to 10 feet. 


1,000 to 5,000 


Woods and 












feet. 


gulches. 


Cyanea 


28 


Endemic. 


General. 


Usually 6 to 


1,000 to 5,ooo 


Woods, ravines. 










1 5 feet. J 


feet. 


gulches. 



EAST POLYNESIAN OR TAHITIAN ISLANDS. 



Sclerotheca ... 
Apetahia 


4 

i 


Endemic in 
E.Polynesia. 
Endemic. 


(Tahiti, 
\Rarotonga. 
Raiatea. 


6 to 25 feet. 
3 to 6 feet. 


1,500 to 3,000 
feet. 
In the mountains. 


Humid wooded 
slopes. 












Elevation of is- 














land 3,400 feet. 





* The materials are nearly all derived from the works of Hillebrand and Drake del Castillo. Some 
of those relating to the elevations in Hawaii are supplemented from my notes. All the genera are 
endemic except Lobelia, of which all the species are apparently endemic, excepting perhaps one, which, 
according to Hillebrand, resembles greatly a species from the Liukiu Islands. 

t The range of the heights of different species of Clermontia is from 5 or 6 feet for shrubs to 25 feet 
for trees. 

\ The heights attained by different species of Cyanea range from 3 or 4 feet to between 30 and 40 
feet, thus : 

In 8 species 3 to 6 feet. In 3 species 15 to 25 feet. 

,> 9 i 6 I0 I M 3 40 ,, 

,, 7 ,i 10 ,, 15 



xxii THE TREE-LOBELIAS 253 

THE LOBELIACE/E OF THE HAWAIIAN ISLANDS. 

Having thus prepared the way, I will proceed to the discussion 
of the Hawaiian Lobeliaceae, dealing first with their "station." 
Their vertical distribution is well illustrated in the large and lofty 
island of Hawaii. Whilst the woody Compositae, as before de- 
scribed, are most at home on the open-wooded and often scantily- 
forested slopes between 5,000 and 9,000 feet, the Lobeliaceae are 
most characteristic of the middle or true forest zone that extends 
from 2,000 or 3,000 feet to between 5,000 and 6,000 feet above the 
sea. This lies within the region of clouds and mists, and it is here 
that the rain-belt or area of greatest rainfall is situated, the annual 
amount averaging probably 150 to 200 inches. It is in such humid 
conditions that, as Hillebrand observes, trees and jungle are 
developed in greatest luxuriance ; and it is here that " the Lobe- 
liaceae exhibit their most striking forms." The traveller, as he 
ascends the mountains, finds the Tree-Lobelias in the region of mist 
and rain-cloud ; and he is lucky if he escapes the usual downpour 
and encounters only a fine drizzling rain. 

The mild climate of this region is indicated by a mean annual 
temperature ranging probably with elevation from 65 to 55 F. 
It is secure from the frosts of the upper slopes of the mountain ; 
whilst at the same time it is above the regions of tropical heat. 
There is, however, no doubt that when the forests extended to the 
coasts, as they occasionally do now on the north side of Hawaii, 
the Lobeliaceae occurred much lower down than they do at present, 
though still only attaining their greatest development in size and 
number in the higher levels. Thus, at rare intervals, I noticed in 
the forests of Hamakua and Kohala, where they descended to the 
coasts, species of Clermontia at an elevation of only 500 or 600 
feet above the sea. 

Probably in no part of the Hawaiian Islands are the conditions 
under which the " Tree-Lobelias " thrive better illustrated than 
on the higher slopes of Mount Eeka, a bulky mountain mass about 
6,000 feet in height, forming the western portion of Maui. Its flat 
top, as Hillebrand observes, is wrapped in a cloud of mist nearly the 
whole year. On the boggy surface of the summit, where Acaena 
exigua gives a tussocky appearance, and Sphagnum or bog-moss 
abounds, flourish Cyperaceae, Lycopods, and Selaginellae ; and here 
Drosera longifolia and a peculiar species of marsh violet (Viola 
mauiensis) find a home. The upper slopes, down to 4,000 feet, 
present similar moist conditions, and here in an open-wooded 



254 A NATURALIST IN THE PACIFIC CHAP. 

district, associated with Cyrtandrae, Marattias, and true Tree-Ferns, 
the ground being covered with Lycopods, the " Tree-Lobelias " 
abound. I noted four kinds within two hundred yards. Of the 
humidity of the upper slopes of Mount Eeka I have a very vivid 
recollection, and my experience of passing a night on that mountain 
is described in Chapter XIX. 

The Lobeliacese, as Hillebrand remarks, occur invariably as 
isolated individuals. I was often struck, however, with the prefer- 
ence the genera showed for particular localities. Thus, Clermontia 
is well represented on the western slopes of Mount Eeka, Delissea 
on the northern slopes of Hualalai (3,800 to 4,500 feet), Cyanea on 
the Hamakua slopes of Mauna Kea (2,300 to 4,100), and Lobelia 
on the southern slopes of Mauna Loa behind Punaluu (2,000 to 
3,500 feet). 

To the student of geographical distribution the Hawaiian 
Lobeliaceae are of especial interest. Mr. Hemsley observes that 
they have their greatest affinities in America (Intr. Bot. Chall. 
Exped., p. 68). M. Drake del Castillo, in his " Memoire couronne 
par 1'Academie des Sciences" (Paris, 1890), remarks that these 
plants connect Hawaii with America just as the Goodeniacese link 
the same group with Australia. This is what we might have 
expected since the centre of the order is in America, principally in 
the Mexican and Andine regions (Drake del Castillo, Flore Polyn. 
Franc., xi.). 

Though five out of the six genera are endemic, the sixth, that 
of Lobelia, has a world-wide distribution. Here then, we have 
a genus that belongs strictly to the next or second stage of the 
plant-stocking of the Hawaiian Group, namely, when the non- 
endemic genera now containing endemic species were introduced. 
As with the Composite genera, Campylotheca and Lipochaeta, 
Lobelia marks the beginning of the new or the close of the old era. 
It is, however, necessary to point out that many of the conditions 
favouring luxuriant and rank vegetable growth are pre-eminently 
represented in the zone of the Lobeliaceae. In these soft-stemmed 
plants with their copious milky sap and large fleshy flowers, some- 
times two or three inches long, the very redundancy of growth 
would tend both to exaggerate and to disguise the generic distinc- 
tions. To the ordinary observer these " Tree-Lobelias " call up 
vague notions of a flora of a bygone age, and by their bizarre 
appearance he might with some excuse be led to give play to his 
imagination when describing them ; but the systematic botanist, 
seeing through their disguise, frames rather more prosaic notions of 



XXII 



THE TREE-LOBELIAS 



255 



their antiquity and degree of differentiation. According to my 
view, the first Hawaiian Lobeliaceae occupied open, exposed 
localities such as are held by the decadent genus Brighamia now, 
and acquired their monstrous form in the humid forests of a later 
age. (See Perkins in Note 80.) 

In his monograph on the Campanulaceae (Engler's Nat. Pflanz. 
Fam., teil 4, abth. 5, 1894), S. Schonland, speaking of the sub- 
family Lobelioideae, places the seven endemic Hawaiian and 
Tahitian genera in a group by themselves. Though, as he 
observes, the Hawaiian tree-forms appear at first sight to consti- 
tute a natural group, they cannot be sharply distinguished from 
other forms, and even in habit come near some Indian and 
Abyssinian types of Lobelia. In their treatment, he says, they 
should all go together, and he does not approve of the endeavours 
of some botanists to isolate one of them (Brighamia) from the rest 
and to connect it with the Australian genus Isotoma. 

It is also to be noted that whilst four of the Hawaiian genera 
are more or less dispersed over the group, one (Brighamia) with 
only one species is confined to the islands of Molokai and Niihau, 
the double habitat being suggestive of its approaching extinction. 
Another ( Holland ia) with six species is restricted to the island 
Oahu. Cyanea, which possesses twenty-eight out of the total 
of fifty-eight species, may, from the point of view of its formative 
energy, be regarded as in its prime. It is thus apparent that, as 
with the Composite, the early Lobeliaceous immigrants were not 
all contemporaneous arrivals. 

Another interesting fact of distribution, brought out by an 
analysis of Hillebrand's materials and illustrated in the subjoined 
table, is that out of the fifty-eight Hawaiian species, all of which are 

DISTRIBUTION OF THE LOBELIACEAE IN THE HAWAIIAN ISLANDS.* 



Hawaiian Lobeliaceae. 


Bri ? - 
hamia. 


Lobelia. 


Cler- 

montia. 


Rollandia. 


Delissea. 


Cyanea. 


1 


Species confined to one island. . 


_ 


_ 


6 


6 


4 


22 


38 


,, two islands 


i 


2 


2 





2 


5 


12 


three 





I 


2 





I 


i 


5 


Species generally distributed, 


































i 


5 


II 


6 


7 


28 


58 



All the species are endemic. 



endemic, thirty-eight, or 66 per cent., are recorded from only one 
island. In most of the other cases they are recorded from two or 



256 A NATURALIST IN THE PACIFIC CHAP. 

three islands, usually adjacent, like Maui and Molokai ; and except 
in the instance of two species of Lobelia and one species of Cler- 
montia they never range over the length of the group. 

These facts speak eloquently of the suspension to a great extent 
of the agencies of dispersal in recent times within the group. Some 
corrections of the figures will be rendered necessary by future 
investigations, but the main conclusion will not be materially 
affected. Such facts are paralleled in the distribution of the 
Hawaiian insects, mollusca, &c. ; but these matters need only 
be mentioned here. We might, indeed, have expected, apart from 
other considerations, that the isolation of the Hawaiian Lobeliaceae 
from their kindred in other parts of the world would not have been 
reproduced within the group itself. This, however, is not the case ; 
and we now see that not only have they been deprived for ages of 
their means of distribution over the Pacific, but that even within 
the archipelago their transportal from island to island has been 
largely suspended. We have before arrived at similar conclusions 
with regard to the early Compositae, when we saw that about half 
the species were not found in more than one island. It is there- 
fore evident that the same great principle regulating the operations 
of the distributing agencies has influenced to a similar extent both 
the Compositae and the Lobeliacese of the Hawaiian Group. 

THE LOBELIACE^E OF THE TAHITIAN OR EAST POLYNESIAN 

REGION. 

The order is represented in this region by two endemic genera, 
Sclerotheca of Tahiti and Rarotonga, and Apetahia of Raiatea. 
These islands are, however, not sufficiently large for the extensive 
development of the arborescent Lobeliaceae, such as we find in 
Hawaii. The species in both genera are either arborescent or 
shrubby ; but I do not gather that they give any character to the 
floras of these islands. According to the data given by Drake del 
Castillo for one of the two peculiar species of Sclerotheca occur- 
ring in Tahiti, these plants grow on the humid wooded slopes of 
the mountains at elevations of 2,000 to 3,000 feet. Whilst in one 
species the plants attain a height of 10 to 25 feet, in the other they 
do not exceed 10 feet. Rarotonga possesses a peculiar species of 
Sclerotheca, 4 to 6 feet high, which was discovered by Cheeseman 
growing plentifully on the upper slopes of the highest mountain of 
the island at altitudes of 1,500 to 2,200 feet. The same botanist 
also came upon a second species of the genus on another mountain 



xxn THE TREE-LOBELIAS 257 

in Rarotonga at elevations of 1,000 to 1,500 feet, but it was rare 
and has not yet been described. The other genus, Apetahia, has 
only been recorded from Raiatea, where it is represented by a 
solitary species (6 feet high) growing, according to Nadeaud, in the 
mountains of that island. 

It is apparent that the dispersal of these genera of the Lobe- 
liaceae amongst the groups of Eastern Polynesia ceased long ago. 
From the circumstance that Sclerotheca exists in Tahiti and in 
Rarotonga, which are about 650 miles apart, it may be inferred 
either that the genus was introduced into this region from outside, 
or else, which is perhaps more probable, that it was developed in 
Tahiti whence it was transported to Rarotonga. Hemsley speaks 
of this Tahitian genus as seemingly marking a former wide exten- 
sion of the Hawaiian arborescent type of the Lobeliaceae (Introd. 
Bot. Chall. Exped., p. 68). This is the view that will be adopted 
in this chapter, and it is precisely the view advocated by Bentham 
and followed here, in the case of the early Compositae of the 
Pacific. 

With regard to the absence of these arborescent Lobeliaceae 
from the island-groups of the Western Pacific, and notably from 
Fiji and Samoa, where no members of the order seem to occur, it 
is probable that, as in the case of the similar distribution of the 
early Compositae described in the preceding chapter, this is to be 
attributed to the fact that the Western Pacific archipelagoes were 
more or less submerged during the general dispersion of the Com- 
positae and Lobeliaceae over the Pacific in the earliest age of 
the floral history of these islands. The occurrence of the early 
Compositae and Lobeliaceae in Rarotonga, which is almost half- 
way between Tahiti and Tonga on the outskirts of the Fijian 
region, sufficiently indicates that they are not lacking in that region 
from inability to reach there in the past. During the age of 
general dispersal of these two orders over the Pacific, probably 
only a few rocky islets, tenanted perhaps by Conifers, marked the 
situation in the Tertiary period of the present archipelagoes of 
Fiji and Samoa. 

One may note in passing the general absence of these arbor- 
escent types of the Lobeliaceae from Malaya, since they do not 
seem to have been recorded either from the Owen Stanley Range 
in New Guinea or from Kinabalu in North Borneo, the highest 
mountain in the Malayan Islands, or from the mountains of Java. 

The consideration of the occurrence of these plants in other 
tropical or subtropical oceanic islands need not detain us long, 
VOL. II S 



258 A NATURALIST IN THE PACIFIC CHAP. 

since, with the exception of the solitary Lobelia scaevolifolia of St. 
Helena, they seem rarely to be found. This species, which is 
endemic, is a shrub growing on the upper slopes and summit of 
the island at elevations of 2,000 to 2,700 feet (Introd. Bot. ChalL 
Exped.) p. 40, and Part ii. pp. 54, 76). 

There are two herbaceous species of Lobelia in Juan Fernandez, 
of which one only, according to Hemsley, could be regarded as 
indigenous. This is a showy Chilian and Peruvian species (Lobelia 
tupa) noticed by Bertero as very common in 1829 (Bot. ChalL 
Exped., Part iii.). Since, however, it would belong to the present 
age of plant-dispersal in the Pacific, it does not require further 
mention here ; and indeed it would almost appear, when we bear 
in mind the geographical position and the history of this island 
since its discovery in 1563, that even as a truly indigenous plant it 
is not above suspicion. Lobelias of this type are now amongst 
the commonest plants of the coast regions of northern Chile, 
where I noticed some as much as 9 or 10 feet high. 

On the Capacities of Dispersal of the Lobeliacecs of the Pacific. 
Of actual observations, with the exception of the instance of birds 
pecking at the capsules of our garden Lobelias, I have come upon 
few that bear directly on this point. When writing of the flora 
of the Kermadec Group, many years ago, Sir Joseph Hooker 
referred (Journ. Linn. Soc. Bot.> vol. i.) to the minute seeds of 
Lobelia as not adapted for transport unless their minuteness and 
number fit them for it ; but since he associates in this connection 
the tiny seeds of Metrosideros, which is now represented by a 
species found all over the Pacific, it would seem that the difficulty 
in the case of Lobelia is not connected so much with the nature as 
with the suspension of these means of distribution during the later 
stages of the plant-stocking of the oceanic islands of the tropical 
Pacific. It will be gathered from the following remarks that the 
descendants of the early Pacific Lobeliaceae are probably as well 
fitted for dispersal as their ancestors, and that the break in the 
communication is the ultimate subject for inquiry. 

The fruits of the Hawaiian endemic genera are in four out of 
five cases baccate, with usually fleshy or pulpy contents. Such 
berries, which are generally yellow, but sometimes bluish in colour, 
vary in size from about half an inch in Rollandia and Delissea to 
an inch in Cyanea, and not infrequently to more than an inch in 
Clermontia. The fruits of Lobelia and Brighamia are capsular 
and dehiscent. With regard to the two genera of the Society 
Islands and Rarotonga, the fruits of Sclerotheca are hard-walled 



xxn THE TREE-LOBELIAS 259 

capsules, opening by two pores ; whilst those of Apetahia are 
seemingly dry and indehiscent. I do not imagine, therefore, that 
the character of the fruit has determined to any important degree 
the distribution of these plants. 

Nor is there reason to suppose that the fruits have acquired 
their baccate character in Hawaii, and that they were originally 
dry and capsular. Both types of fruit are found among the 
arborescent Lobeliaceae of America, with which the Hawaiian 
genera have their affinities. Centropogon, for instance, which 
occurs in Central America and in the warm parts of North and 
South America, has, according to Baillon, a somewhat fleshy berry. 
It is noteworthy that a similar question is raised with respect to 
Cyrtandra as to the relation between fleshy fruits in the Pacific 
islands and dry or capsular fruits in the continental home of the 
genus (see Chapter XXV.). 

The berries of the Tree-Lobelias would attract birds. We 
learn from Mr. Perkins that one of the Hawaiian Drepanids, the 
Ou, is very partial to the berries of some of the Tree-Lobelias 
and especially those of Clermontia, the seeds passing unharmed 
in the droppings. The mode of dispersal of the seeds of 
the dry-capsular fruits is not so apparent ; but the fruits could 
scarcely be less inviting to birds than the dry capsules of Metro- 
sideros, the small seeds of which have in some way or other 
been carried to almost every island-group of the Pacific. I have 
beside me the dark brown, smooth crustaceous seeds of a species of 
Clermontia. They measure -$ of an inch or 0*6 of a millimetre, and 
about 500 go to a grain. Mr. Wallace, in his book on Darwinism, 
advocates the paramount influence of winds over birds for carrying 
small seeds, like those of Orchis and Sagina, over tracts of ocean 
a thousand miles across. I am, however, not inclined to think that, 
except as regards the spores of cryptogams, winds have done 
very much for Hawaii. For small seeds we can appeal not only to 
the agency of birds and bats but also to insects (see Chapter 

XXXIII.). 

Observations of this kind, however, merely indicate that these 
early Lobeliaceae possessed the same capacities for dispersal that 
in the succeeding stages of the plant-stocking of the Pacific islands 
have belonged to Metrosideros, Cyrtandra, Ophiorrhiza, Freycinetia, 
and many other small-seeded genera. They go no way to explain 
why the same agencies which transported the minute seeds in a 
later age could not have been available for continuing the dispersal 
of the early Lobeliaceae. To find an explanation we are compelled 

S 2 



260 A NATURALIST IN THE PACIFIC CHAP. 

to go behind the mere capacities for dispersal and to appeal to the 
general laws of distribution in so far as our facts enable us to 
interpret them. 

We have seen that the two principal components of the early 
Pacific flora, the Compositse and the Lobeliaceae, have American 
affinities. The plants of the later ages are mainly Old World in 
their connections. Though containing often endemic species in 
the various groups, the genera occur also outside each group. 
The stream of migration that came from America during the early 
age of the Compositae and the Lobeliaceae, when the islands 
of the Western Pacific were more or less submerged, was during 
the later ages (after these islands had re-emerged) suspended 
or diverted, giving place to a stream that brought plants in 
numbers from tropical Asia, Malaya, and Australia. The general 
dispersion of the Compositae and Lobeliaceae took place during 
the Tertiary submergence of the islands of the Western Pacific, 
including the island-groups of Fiji, Samoa, and Tonga. The 
migration from the west, mainly Indo-Malayan in character, 
occurred after the re-emergence of those archipelagoes. Thus we 
get to understand how genera like those of the early Lobeliaceae 
and Cyrtandra, which possess, as regards the minute size of their 
seeds, closely similar capacities for dispersal, have such different 
distributions, the first confined to Hawaii and Tahiti and American 
in their affinities, the second widely spread over the Pacific with its 
home in Malaya. 

We have yet to inquire whether this suspension of the means 
of transport in the later ages of the Pacific Lobeliacese is confined 
to the tropics or whether it extends to the colder latitudes in the 
southern hemisphere. The indications of the Lobeliaceae of the 
" antarctic flora " go to establish that the dispersal of the order is 
still, or was very recently, in operation in these high latitudes. It 
is well illustrated, among other plants, by Lobelia anceps, which is 
found in extra-tropical South America, Australia and New Zealand, 
and South Africa. This, indeed, recalls Bentham's view concerning 
the Compositae, that whilst communication was broken off in the 
tropics, it was kept up in higher latitudes. 

Here ends, therefore, our consideration of the Tree-Lobelias of 
the Pacific islands ; but as it is not quite complete without a dis- 
cussion of the remaining endemic genera of other orders than 
the Compositae and Lobeliaceae which also belong to the same 
early age of the Pacific floras, I will proceed at once to their 
consideration. 



xxn OTHER HAWAIIAN ENDEMIC GENERA 261 

THE HAWAIIAN ENDEMIC GENERA EXCEPTING THOSE OF THE 

COMPOSITE AND LOBELIACE^E. 

It will not be possible for me to do more than point out a few 
general indications that can legitimately be drawn from these 
genera. The subject bristles with difficulties for the systematist ; 
but on one point there can be but little danger of going astray, 
namely, in imputing to them a high antiquity in the floral history 
of Hawaii. This can be said of all of them, whether or not the 
generic distinction adopted in Dr. Hillebrand's work is always 
adopted by botanists. It is therefore in this general sense that 
they may be regarded as belonging to the early age of the 
Hawaiian flora. 

Although the genera of Compositae and Lobeliaceae are pro- 
minent amongst the representatives of the original flora of the 
Hawaiian Islands, forming about two-fifths of the whole, the 
genera of other orders are by no means inconspicuous, and their 
variety is shown in the fact that though twenty-three in number 
they belong to twelve orders. It is possible to divide these genera 
into two groups one the older and perhaps more or less con- 
temporaneous with the Lobeliaceae and Compositae, the affinities 
when apparent being American ; the other the more recent and 
marking the close of the first era of the plant-stocking of these 
islands, the affinities being all with the Old World, and especially 
with Malaysia. This grouping is indicated in the list subjoined ; 
and it may be here remarked that whilst shrubs, undershrubs, and 
perennial herbs of the Caryophyllaceae, Labiatae, and Urticaceae 
form the features of the earlier group, trees of the Rubiaceae and 
Araliaceae are the most conspicuous members of the later group. 
At the close of the earliest era known to us of the floral history of 
the Hawaiian Islands we observe the commencement of those 
forests that now throughout Polynesia as well as in Hawaii betray 
their Asiatic origin. 

In making this distinction I am proceeding on the assumption 
that the stream of migration, at first chiefly American in its source, 
came ultimately in the main from the Asiatic side of the Pacific, 
The change commenced, as I hold, in the latter portion of the first 
era of plant-stocking, an era characterised by the arrival of those 
early plants that are now represented by the endemic genera of 
the archipelago. The genera of this early period that belong 
neither to the Compositae nor to the Lobeliaceae are, as above 
observed, arranged by me in two groups, one regarded as 



262 A NATURALIST IN THE PACIFIC CHAP. 

contemporaneous with, the other as of later origin than, the genera 
of these two orders. To the first belong the shrubby, highly dif- 
ferentiated genera of the Caryophyllaceae, Schiedea and Alsiniden- 
dron, and the Labiate genera, similarly differentiated, of Phyl- 
lostegia and Stenogyne. To the second belong the Rubiaceous 
genera Kadua, Gouldia, Bobea, and Straussia, the Araliads 
Cheirodendron, Pterotropia, and Triplasandra, and the Loga- 
niaceous Labordea. 

In the earlier group the fruits are dry in half the genera, and 
in such cases granivorous birds probably were usually the trans- 
porting agents. Only in one case (Nothocestrum) is the fruit a 
berry, and in the other cases we have fruits like the fleshy nucules 
of Phyllostegia and Stenogyne which would probably attract birds. 
In the later group two- thirds or three-fourths of the genera have 
moist fruits such as would be eaten by frugivorous birds. Of 
these most are drupes, possessing not a single stone, but two or 
more pyrenes. This is the first appearance of the drupe in the 
plant-history of the archipelago. The Rubiaceous type of drupe 
inclosing two or more pyrenes plays a very conspicuous part in the 
distribution of plants over the Pacific in the succeeding eras. 

I would here lay stress on an important characteristic of all the 
fruits of the endemic genera of the Hawaiian Islands. There are 
no " impossible " fruits of this era in Hawaii, such as we occasion- 
ally find in the succeeding eras. I mean by this term, fruits that 
defy the efforts of the student of distribution to explain their 
transport in their present condition. The discovery of a new 
inland genus possessing dry indehiscent fruits three or four inches 
long, or even of a single species of the coniferous Dammara, would 
play havoc with all our views respecting the stocking of these 
islands with their plants. The finding here of a large marsupial 
would scarcely produce more astonishment. The fruits indeed of 
this early era are very modest in their size, the dry indehiscent 
fruits and the stone-fruits rarely exceeding half an inch (12 mm.) 
in size. 

There is another interesting point which is connected with the 
deterioration of some of the fruits in their capacity for dispersal. 
Some of the species of Phyllostegia, and a few also of the Araliads, 
as well as those of Nototrichium, are ill fitted for dispersal by 
birds now, the coverings of the seeds being not sufficiently hard to 
protect them from injury in a bird's stomach. At the same time 
there are in some cases other species of the same genera that are 
better suited for this mode of transport. The effect of dispersal 



XXII 



OTHER HAWAIIAN ENDEMIC GENERA 



263 



by frugivorous birds is that only the hard-coated seeds propagate 
the plant in a new locality. When, however, as has occurred in 
the Hawaiian Islands, bird-agency largely ceases to act, this 
selective influence is removed (see Note 68). 



ENDEMIC HAWAIIAN GENERA, EXCLUDING THOSE OF THE COMPOSITE AND 
LOBELIACE-dE, AS GIVEN IN HILLEBRAND'S " FLORA OF THE HAWAIIAN 
ISLANDS.' 

[Those preceded by * are not usually regarded now by botanists as endemic, though they nearly 

take that rank.] 

THE EARLIER GROUP. 



Genus. 


Order. 


Number 
of 
species. 


Character. 


Fruit. 


Affinities. 


Isodendrion 


Violaceae. 


3 


Shrubs. 


Capsule. 


American (H). 


Schiedea 
Alsinidendron... 


Caryophyllaceae. 


17 

i 


Undershrubs, 
&c. 
Undershrubs. 


Capsule. f 

Capsule, with j 
fleshy calyx. I. 


Near Colobanthus of the 
Antarctic islands, tem- 
perate South America, 
and Australia (C). 


Platydesma 


Rutaceae. 


4 


Small trees or 


Capsule. 











shrubs. 






Hillebrandia ... 


Begoniacese. 


i 


Herbs. 


Capsule. 





Nothocestrum.. 


Solanaceae. 


4 


Small trees. 


Berry. 


South American (H). 


*Haplostachys .. 


Labiatae. 


3 


Herbs. 


Dry nucules. 


Regarded by Gray as a 
section of Phyllostegia. 


*Phyllostegia ... 


n 


16 


Undershrubs. 


Fleshy nucules, f 


Belong to the tribe Prasiae, 












which is mostly Asiatic. 












Two other species of 


Stenogyne 





17 


Trailers or 
climbers. 


Fleshy nucules, j 


Phyllostegia recorded 
from Tahiti and Pau- 










I 


motu Islands. 


Charpentiera ... 


Amarantacese. 


2 


Trees. 


Utricle. 


American (H). 


Touchardia 


Urticaceae. 


I 


Shrubs. 


Achene with 





Neraudia 




2 


Shrubs. 


fleshy perigone. 
Achene with 


Allied to Boehmeria, a 










fleshy perigone. 


genus of Old and New 












Worlds. 


THE LATER GROUP. 


*Pelea 


Rutaceae. 


20 


Trees. 


Capsular. 


Belongs to Melicope, an 
Old World genus (IK). 




Broussaisia 


Saxifragaceae. 


2 


Small trees. 


Berry. 


Malayan (H). 


*Cheirodendron. . 


Araliaceae. 


2 


Trees. 


Drupe. 


Referred to Panax, an 












Old World genus (IK). 


*Pterotropia 
Triplasandra ... 


> 


3 
4 


Trees. 

Trees or 
shrubs. 


Drupe. f 
Drupe. 


Malayan (H). 
Pterotropia referred to 
Heptapleurum of Old 
World (IK). 


Kadua 


Rubiaceae. 


16 


Shrubs, &c. 


Capsular 


Approaches both Asiatic 
and American types (C). 




Gouldia 


., 


5 


Small trees or 


Drupaceous berry. 


American (C). 








shrubs. 






Bobea 





5 


Small trees. 


Drupe. 


Malayan (H). Genus 
also in Malaya (IK). 


Straussia 


M 


5 


Trees. 


Drupe. 


Near Psychotria, a genus 












of Asia and America (H). 


Labordea 


Loganiaeeae. 


9 


Small trees or 


Capsule with 


Malayan (H). 








shrubs. 


pulp. 




*Nototrichium .. 


Amarantaces. 


3 


Trees or 


Utricle. 


Referred to the Aus- 








shrubs. 




tralian Ptilotus(IK). 



(H) = Hillebrand's Flora of the Hawaiian Islands. 
(C) = Drake del Castillo's Rentarques sur la. Flore de la, Polynesie. 
(IK) = Index Kewensis. 

NOTE. Probably Schumann's genus, Pteralyxia, should be placed in the later group (.see p, 154). 



264 A NATURALIST IN THE PACIFIC CHAP. 

Another feature of interest is to be found in the distribution 
within the archipelago of the species of the peculiar genera. As 
in the case of the Compositae and Lobeliaceae, but few of the 
species are generally distributed, most being restricted to one 
island or to two or three adjacent islands. The suspension of the 
dispersal among the islands is, however, not so marked as with the 
species of the two orders just named. 

NOTE. Some further remarks on some of these genera are 
given in Note 68. 



THE ENDEMIC GENERA OF THE FIJIAN ISLANDS. 

The interest that is associated with the endemic genera of 
Hawaii fails to attach itself to those of Fiji. For this there are 
several reasons. In the first place, our acquaintance with the 
Fijian flora is much less complete. In the next place, the group 
holds a much less isolated position, and the history of an endemic 
genus may have a significance quite different from that connected 
with it in Hawaii. Fiji also lacks, on account of its submergence 
in the Tertiary period, those highly interesting genera of the 
Compositae and Lobeliaceae that form the chief feature in the early 
history of the flowering plants of Hawaii. Then, again, on account 
of our imperfect knowledge of the floras of the neighbouring groups 
of continental islands to the westward, the New Hebrides, Santa 
Cruz, and Solomon Groups, we can never feel quite confident that 
any particular genus is really peculiar to the Fijian archipelago. 
This is well brought out in the later history of the genera 
designated by Dr. Seemann in his Flora Vitiensis as peculiar to 
Fiji. 

Of the sixteen genera enumerated by Dr. Seemann, and given 
in the table below, only about half now retain their character 
of being restricted to Fiji. Nor does it seem likely that future 
investigations will increase this number, since, judging from a 
remark made by Mr. Hemsley in his paper on the botany of 
the Tongan Group, explorations subsequent to those of Dr. 
Seemann. more especially those of Mr. Home, have not apparently 
added a single new endemic genus to the Fijian flora. It will 
be seen from the list that at least four of the sixteen genera have 
since been found in the Malayan region, and in one case (Smythea 
pacifica) the same species occurs in both regions ; whilst a fifth 
genus (Haplopetalon) has been recorded from New Caledonia. 



XXII 



THE FIJIAN ENDEMIC GENERA 



265 



There are, however, some peculiarities about the Fijian endemic 
genera that will attract our attention from the standpoint of 
dispersal. One remarkable feature is the paucity of species. 
Almost all the genera are monotypic, that is to say, they are only 
known by a single species. Amongst the twenty-eight Hawaiian 
genera that are strictly endemic, only four or five are monotypic, 
and they are mostly regarded by Hillebrand as worn-out, decadent 
types found in only one or two islands. In Hawaii there are 
on the average six species to each endemic genus ; and it is 
thus apparent that in the display of formative energy Nature has 
worked on very different lines in these two groups. Since the nine 
Fijian endemic genera belong to nearly as many different orders, 
the composition of this endemic generic flora is by no means 
homogeneous. It is, I venture to think, such a motley collection as 
one might expect in a region that has been exposed to wave after 
wave of migration from the west, with no lofty mountains, as 
in Hawaii, to afford a refuge against extinction. It by no means 
follows that all these endemic genera have been produced in Fiji. 
Some of them may represent genera that have become extinct in 
the large continental groups to the westward. 

SEEMANN'S SIXTEEN FIJIAN ENDEMIC GENERA. 



Genus. 


Order. 


Number 
of 
species. 


Character. 


Fruit. 


Affinities or other 
localities. 


Richella 


Anonaceae. 


i 


Tree. 


Baccate (?). 


Indian in type (C). 


Trimenia 


Ternstroemiaceae 


i 


Tree. 


Unknown. 




Pimia 


Sterculiaceas. 


i 


Tree. 


Small spinose 


Related to Australian 










capsule. 


genera (S). 


Graeffea 


Tiliaceae. 


i 


Tree. 


Unknown. 


Near Trichospermum, a 












Fijian and Malayan 












genus (S). 


Thacombauia... 


Humiriaceae. 


i 


Shrub. 


Drupe. 


Order mainly South 












American. 


Amarouria 


Simarubeae. 


i 


Tree. 


Dry drupe. 


Near Soulamea, a Ma- 












layan genus (S). 


*Smythea 


Rhamneae. 


i 


Straggling 


Capsule. 


Also in Burma, New 








shrub. 




Guinea, and Malaya 












(IK), (Sc). 


*Oncocarpus 


Anacardiaceae. 


2(H) 


Tree. 


Drupe. 


Also in New Guinea 












(IK). 


*Haplopetalon... 


Rhizophoreae. 


2 


Shrub. 


Unknown. 


Also in New Caledonia 












(IK). 


*Nesopanax 


Plerandreae. 


I 


Tree. 


Drupe. 


=Plerandra (IK). 


Bakeria 


Plerandreae. 


I 


Tree. 


Drupe. 




Pelagodendron . 


Rubiaceae. 


I 


Shrub. 


Berry. 




*Paphia 

*Carruthersia ... 
*Couthovia 


Ericaceae. 

Apocyneae. 
Loganiaceae. 


I 

2(H) 
2 


Shrub. 

Climber. 
Tree. 


Berry. 

Berry. 
Drupe. 


=Agapetes, a Malayan 
genus (IK). 
Also in Philippines (IK). 
Also in Kaiser Wilhelms- 












land, New Guinea (So). 


Canthiopsis 


Loganiaceae. 


I 


Shrub. 


Drupe. 





Those genera marked * have since been found outside the group. 

The authorities are thus indicated : (C)=Drake del Castillo ; (H)=Horne ; (ll)=Index Kewensis 
(S)=Seemann ; (Sc)=Schimper ; (So)=Solereder in Engler's Nat. Pflanz. Fam. 



266 A NATURALIST IN THE PACIFIC CHAP. 

The fact that several of them are fitted for dispersal by 
frugivorous birds is very suggestive of the lack of means of 
transport in later times. In the instance of Couthovia corynocarpa 
the drupes are known to be the food of fruit-pigeons at the present 
time (Seemann), whilst this is also true of Oncocarpus vitiensis, 
though this genus has since been found in New Guinea. Since, as 
will be pointed out in a later chapter, birds must still be fairly 
active in carrying seeds to Fiji from regions westward, it would 
seem that genera only become peculiar to Fiji when they fail 
at their source, and it is indeed doubtfu whether any of the 
Fijian peculiar genera are home productions. One may instance 
in this connection the genus Pimia, the fruits of which are especi- 
ally well suited for attachment to a bird's plumage, yet it is only 
known from Fiji. 

It should be here observed that no peculiar generic types have 
been recorded from the adjacent Tongan Group, and scarcely any 
from Samoa. Except perhaps with the Palmaceae, no peculiar 
genera seem to be mentioned in Dr. Reinecke's memoir on Samoa. 

Summary. 

(1) The Lobeliaceae, like the Composite, take a prominent 
place in the early Pacific flora, being represented, more particularly 
in Hawaii but also in the East Polynesian or Tahitian region, by 
endemic genera of tall shrubby and tree-like species. 

(2) Tree-Lobelias occur in other parts of the world, as in South 
America and tropical Africa ; but it is especially on the higher 
slopes of the mountains of Equatorial Africa that they attain a 
development comparable with that of Hawaii. 

(3) In Hawaii the Tree-Lobelias are most characteristic of the 
middle forest-zone (3,000-6,000 feet), where the temperature is 
mild, the rainfall heavy, and the atmosphere laden with humidity. 

(4) The affinities of these endemic genera of the Lobeliaceae are 
mainly American ; but their generic distinctions have been both 
exaggerated and disguised by redundant growth. 

(5) From the distribution of the genera and species within the 
Hawaiian Group it is evident that, as with the early Compositae, the 
original Lobeliaceous immigrants were not all contemporaneous 
arrivals. Some of the genera are on the point of extinction, whilst 
others are in their prime. 

(6) The absence of the Lobeliaceae from the groups of the 
Fijian area (Fiji, Tonga, Samoa) is probably to be connected, as in 



xxii SUMMARY 267 

the case of the absence of the early Compositae, with the circum- 
stance that the general distribution of these two orders over the 
tropical Pacific occurred during the Tertiary submergence of these 
archipelagoes. 

(7) These endemic genera of the Lobeliaceae possess the same 
facilities for dispersal that are owned by other genera with minute 
seeds, such as Cyrtandra, &c., that are dispersed over the Pacific ; 
but in the case of the Lobeliaceae the agencies of dispersal have 
been for ages suspended. 

(8) This suspension is to be associated with the diverting of the 
main stream of migration from its source in America, during the 
early age of the Lobeliaceae and Compositae, to a source on the 
Asiatic side of the Pacific. 

(9) The Hawaiian endemic genera other than those of the 
Compositae and Lobeliaceae arrange themselves in two groups an 
earlier group containing highly differentiated Caryophyllaceae and 
Labiatae, and belonging to the age of the Compositae and Lobelia- 
ceae ; and a later group, characterised by Rubiaceae and Araliaceae, 
which marks the close of the first era, as well as the change in the 
main source of the plants from America to the Old World, the 
beginning of the Hawaiian forests, the appearance of the Rubi- 
aceous drupe, and the first active intervention of frugivorous birds. 

(10) Though there are no "difficult" or "impossible" fruits 
(fruits, the dispersal of which is not easy to explain) amongst the 
forty and odd endemic genera of Hawaii and Tahiti, it is note- 
worthy that in some cases the fruits are seemingly little fitted for 
dispersal now, and that this deterioration in capacity for dispersal 
is to be frequently associated with more or less failure of the inter- 
island dispersal in the case of Hawaii. 

(n) The interest associated with the Hawaiian endemic genera 
fails to attach itself to those of Fiji, where genera only seem 
to have become peculiar because they have failed at their sources 
in the regions to the west. The endemic genera of the Compositae 
and Lobeliaceae are here lacking, and this is true also of the 
neighbouring Samoan and Tongan Groups, it being held that 
the age of the general dispersion of these orders over the Pacific 
corresponded with the Tertiary submergence of the archipelagoes 
of the Western Pacific. Those of Fiji, which do not amount to ten 
in number, belong to nearly as many orders and present a motley 
collection such as one might look for in a group much less isolated 
than Hawaii and exposed to wave after wave of migration from 
the west. 



CHAPTER XXIII 

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING 

PLANTS 

THE MOUNTAIN-FLORAS OF THE PACIFIC ISLANDS AS 
ILLUSTRATED BY THE NON-ENDEMIC GENERA 

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. 
Acaena, 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 AGE OF THE ENDEMIC GENERA OF FLOWERING 

PLANTS. 

WE are now entering an era distinguished from the preceding age 
of the endemic genera, the age chiefly of the Composite and 
Lobeliaceae, by the fact that the extreme isolation that followed that 
era no longer prevails. In a sense these island-floras are in touch 
again with the world around, though the main stream of plant- 
migration now comes from the south and from the west. Yet in a 
large number of cases, the amount varying greatly in the different 
groups, it is evident that this stream has not flowed continuously 
to the present day. The agencies of dispersal are often no longer 
active ; but the period of inactivity has not been sufficiently 
prolonged to produce generic distinction, and the differentiating 
energy has been restricted to the development of new species. 

Yet within these limits the development of new forms, as 
indicated in Table B on p. 233, has often been very great. Thus, 
nearly half the Hawaiian genera that are non-endemic are com- 
posed entirely of species not found outside the group ; and in 



CH. xxm THE HAWAIIAN MOUNTAIN- FLORA 269 

this sense they may be regarded as cut off from the regions 
around. In Fiji and Tahiti only about a fourth are in this 
manner isolated, the agencies of dispersal being still effective with 
the majority of the genera. It is apparent, therefore, that the 
same question concerning the cause of the failure of the means 
of dispersal presents itself in this era as in the last, and most 
markedly in the instance of Hawaii. 

The simplest and quickest plan for bringing into relief the 
prominent features of this age is first to regard the genera from 
the standpoint of the elevation of their stations. We have before 
remarked that in the occurrence of extensive regions of great 
altitude the Hawaiian Islands differ conspicuously from the groups 
of Tahiti and Fiji (and I may add Samoa) ; and that they present 
conditions for the development of a temperate mountain-flora that 
are not found at all in Fiji and are barely represented in Tahiti. 
That the Hawaiian flora responds to this contrast between the 
elevations of the three groups is well established ; and I will now 
proceed to refer more in detail to the subject. 

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 



270 A NATURALIST IN THE PACIFIC CHAP. 

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 Acaena 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 Dacrydiurn, 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. 

THE MOUNTAIN-FLORA OF HAWAII AS ILLUSTRATED BY THE 
NON-ENDEMIC GENERA. 

Let us look in the first place at Hawaii, where the breaking ofif 
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 Composite and 
Lobeliaceae and other orders is here again presented to us, and 



xxm THE HAWAIIAN MOUNTAIN-FLORA 271 

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 Acaena, 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 



272 



A NATURALIST IN THE PACIFIC 



CHAP. 



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). 



Genus 


Usual 
altitude of 
station in feet. 


Distribution outside 
Polynesia. 


Distribution in Hawaii, 
Fiji, and Tahiti. 


Fruit. 


+ + + + + + + 3 Both Worlds. 

* i 


Old World. 


New World. 


Antarctic flora. 


W 1 Australia and 
g | New Zealand. 


j>, 

13 



:3 

a 
Z 

m 

8 

EMIC 
'+ 


.Ji 

:^> 
h 

: 3 
I 


: fl 

| H 


1> U1 

1! 

^ fan 

< 


Ranunculus (2) ... 
Viola M 


i 

6,000 7,000 
2,000 6,000 
2,000 9,000 
s,ooo 10,000 
7,000 8,000 
5,000 10,000 
4,000 7,000 
5,000 6,000 
3,000 6,000 
6,000 8,000 
3,000 9,000 
6,000. 
4,000 8,000 
2,000 6,000 
3,000 8,000 

Coast to 10,000 
2,000 8,000 
3,000 6,000 
4,000 7,000 

2,000 6,000 

6,000 
3,000 5,000 
4,000 6,000 
3,000 6,000 
3,000 5,000 

WITH I 

2,000 10,000 

Coast to 6,000 
Up to 7,000 
Coast to 10,000 
2,000 7,000 
Up to 10,000 
Coast to 6,000 
Up to 10,000 

4,000 6,000 
4,000 
2,500 5,000 

3,000 10,000 


ALL 


SPE 


CIES 








Achene. 
Capsule. 
Capsule. 
Carpels. 
Pod. 
Pod. 
Berry. 
Spinose achene. 
Drupe. 
Prickly carpel. 
Drupe. 
Viscid achene. 
Achene. 
Capsule. 
Berry. 

Drupe. 
Capsule. 
Fleshy nut. 
Capsule. 
Berry. 
Toothed nutlet. 
Awned nutlet. 
Awned grain. 
Awned grain. 
Awned grain. 
Grain. 

Drupe. 
Capsule. 
Seed-like. 
Drupe. 
Nutlet. 
Nutlet. 
Grain. 
Awned grain. 

Fleshy. 
Capsule. 
Drupe. 

Capsule. 











-f. 








Silenek) 
Geranium (6) 
Vicia (i) 








+ 
















4- 
















-i- 








Sophora(i) 
















+ 












-j. 




Acaena(i) 
Gunnera (i) 
Sanicula(i) 
Coprosma(9) 
Lagenophora (i)... 
Artemisia (2) 
Lobelia (5) 






4. 




-j. 














4. 




_i_ 












_|- 






.}. 
















4- 








+ 








4. 






4. 




+ 

+ 
+ 










+ 
















_j_ 








Vaccinium (2) 

Myoporum (i) ... 
Plantago (2) . ... 
Exocarpus (2) 
Sisyrinchium (i ... 
Astelia(2) 
Oreobolus (i) 
















+ 
Samoa 








+ 


+ 
_l_ 






+ 




















+ 


+ 



























4. 










+ 








4- 




+ 












4. 




_l_ 








Agrostis (3) 
Deschampsia (3)... 
Trisetum (i) 
Poa<2) 


+ 

+ 
-f 
+ 

}NDE 

"+" 

+ 










-f. 
















-f 
















-j- 
















+ 








Cyathodes (2) 
Lysimachia (6) ... 
Chenopodium (2). . 
Santalum (3) 
Carex (5) 


WIC / 


LND '. 


^ON- 


ENDE 
+ 


MIC 

4- 


SPEC 


IBS. 

+ 












-f- 








-|- 














+ 


+ 
+ 

+ 
+ 

WIT 












-j- 




Rhynchospora (4). 
Panicum (14) 
Deyeuxia(3> 

Fragaria chilensis. 
Drosera longifolia. 
Nertera depressa.. 

Luzula campestris. 
















4- 
+ 
























+ 






* NO 


ENE 
+ 


EMIC 


SPE 


CIES. 
+ 








+ 










+ 












4- 








Samoa 


+ 












-f- 















xxin THE HAWAIIAN MOUNTAIN-FLORA 273 

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 europsea, 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 sand- 
wicensis 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 
VOL. II T 



274 A NATURALIST IN THE PACIFIC CHAP. 

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 only ... 20 
in Hawaii and Fiji . . 2 

,, in Hawaii and Tahiti . o 

in all three groups . . 4 

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 Raro- 
tonga ; 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 



xxin THE HAWAIIAN MOUNTAIN-FLORA 275 

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 erno- 
deoides, 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. Kramer, 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 i of an inch (5 mm.), and those of Myoporum 
scarcely of an inch (6 mm.) ; whilst the nuts of Exocarpus range 
in the Hawaiian species from -f^ to ^ of an inch (7-15 mm.), and 
the beans of Sophora chrysophylla do not at the most exceed 
I 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 Acaena 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 Lageno- 
phora and the seeds of Plantago display the capacity of adhesive- 
ness by means of a gummy secretion. 

One or two of these genera need further mention. I will first 
take Acsena, 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. 

T 2 



276 A NATURALIST IN THE PACIFIC CHAP. 

Captain Carmichael, in the instance of Acaena sanguisorbae 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 Acaena, 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 Lageno- 
phora, one of the Compositse. 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 



xxni THE HAWAIIAN MOUNTAIN-FLORA 277 

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, 1 894, 1 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 



278 A NATURALIST IN THE PACIFIC CHAP. 

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 moun- 
tains, 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 con- 
tracting 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 dis- 
cussed 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 Tetra- 



xxin THE HAWAIIAN MOUNTAIN-FLORA 279 

onidse published in the Transactions of the Linnczan 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 -^ of an inch, 
whilst those of A. vulgaris measure rS mm., or T X T 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 ani'mals. 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 



280 A NATURALIST IN THE PACIFIC CHAP. 

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> oo 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. anti- 
podum, 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. 



xxin THE HAWAIIAN MOUNTAIN-FLORA 281 

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. reticu- 
latum, 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 Poly- 
nesian (Samoa ?) species originally described by Baron F. von 
Miiller, 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 connec- 
tion 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 



282 A NATURALIST IN THE PACIFIC CHAP. 

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 physio- 
logically 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 tameiameiae, an Epacridaceous species found also in 
the uplands of Tahiti, occurs, according to Hillebrand, on all the 



xxiii THE HAWAIIAN MOUNTAIN-FLORA 283 

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 sand- 
wicheum 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. haleakalae, occurs as a tall shrub on Haleakala at eleva- 
tions 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. Kramer 
on the slopes of Mauna Loa, I found a number of the " stones " 
of Cyathodes tameiameiae, 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). 



284 A NATURALIST IN THE PACIFIC CHAR 

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 somegranivorous 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. 



xxin THE HAWAIIAN MOUNTAIN-FLORA 285 

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. 

TJie 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 eleva- 
tions 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. 



286 A NATURALIST IN THE PACIFIC CHAP. 

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, 



xxin THE HAWAIIAN MOUNTAIN-FLORA 287 

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 Acaena, 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 



288 A NATURALIST IN THE PACIFIC CH. xxm 

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 ex- 
emplified 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 Coniferae. Dammara, Podocarpus, Dacrydium. 
Not belonging to the present era of dispersal. The age of dispersal of the 
Coniferas in the Pacific. Earlier than the age of Composite and Lobeliaceae. 
The first in the Mesozoic period. The last in the Tertiary period. 
Summary. 

THE MOUNTAIN-FLORA OF THE TAHITIAN REGION AS 
ILLUSTRATED BY THE NON-ENDEMIC GENERA 

THIS floral region of the Pacific corresponds with the limits of 
Eastern Polynesia, and includes not only the Tahitian group 
proper, but also the Cook, Austral, Paumotuan, and Marquesan 
groups. It is only, however, in Tahiti, the peaks of which rise to 
over 7,000 feet above the sea, that we should expect to find such a 
mountain-flora, since the islands of the other groups are much 
lower, the highest of them in the Marquesan group barely exceed- 
ing 4,000 feet. Yet even in Tahiti it is not possible to speak of a 
mountain-flora in the sense that we attach to it in Hawaii. The 
elevated area of its interior is, as described in Chapter XIX., 
relatively very small ; whilst, as Drake del Castillo points out, the 
conditions presented by the steep mountain-slopes rarely afford a 
hold for trees of any size, ferns often predominating in the higher 
levels. Still, we can observe the traces of such a flora, and it is in 

VOL. II U 



2 9 o A NATURALIST IN THE PACIFIC CHAP. 

this sense only that the term " mountain-genera " is used in 
relation with this group. 



Mountain-Genera of the Tahitian or East Polynesian Region. 

Weinmannia, Saxifragaceae, from New Zealand. ' \ 

Coprosma, Rubiaceae, from New Zealand. I all species 

Vaccinium, Vacciniaceae, from the northern hemisphere, j endemic. 
Astelia, Liliacese, from New Zealand. 

Coriaria, Coriariaceae, from New Zealand 1 

Cyathodes, Epacridaceae, from New Zealand . . . . j " 

Nertera depressa, Rubiaceae, a species of the Antarctic flora. 
Luzula campestris, Juncaceae, from the northern hemisphere. 

The Tahitian non-endemic mountain-genera, though scanty in 
number, are of considerable interest to the student of plant- 
dispersal. Among those possessing only species that are confined 
to Eastern Polynesia, genera that would be regarded as belonging 
to a past era of dispersal, Weinmannia, Coprosma, Vaccinium, and 
Astelia may be mentioned. 

Weinmannia, a Saxifragaceous genus of trees and shrubs, not 
represented in Hawaii, but recorded from almost all the elevated 
oceanic groups of the tropical South Pacific, as well as from the 
New Hebrides and New Caledonia, has its home in South 
America, more particularly in the Andes, and also occurs in New 
Zealand, Tasmania, and the Mascarene Islands. One can scarcely 
doubt that, as in the case of Coprosma, the Pacific Islands 
derived their species originally from high southern latitudes, as 
from New Zealand, the absence of the genus from Hawaii 
negativing an American origin. Of the two Tahitian species, one 
is peculiar to Tahiti, whilst the other, W. parviflora, which is 
conspicuous on the mountain-crests at elevations of 3,000 feet and 
over, occurs also in the Marquesas. Another species grows in 
abundance in the interior of Rarotonga. Samoa possesses two 
species, one of which, W. affinis, occurs in Fiji, and the other, 
W. samoensis, which frequents the mountains at elevations of 
1,500 to 3,300 feet, is seemingly endemic. Fiji possesses four or 
five species of Weinmannia occurring at all altitudes up to 2,000 
feet, of which some are evidently peculiar. The capsular fruits of this 
genus contain hairy seeds that would probably become entangled 
in a bird's plumage. Dispersal by birds is distinctedly indicated 



xxiv THE TAHITIAN MOUNTAIN FLORA 291 

in the curious observation of Dr. Reinecke in the case of the 
Samoan peculiar species, The seeds, he says, appear to germinate 
by preference on the bark of other trees, young plants growing 
epiphytically being of frequent occurrence. 

There is some evidence that the species of Weinmannia, about 
ten in all, found in the tropical islands of the open Pacific are 
derived from one or two polymorphous species. As we learn from 
Mr. Cheeseman, the Rarotongan species, W. rarotongensis, has 
considerable affinity to several closely allied Polynesian species, 
and its nearest allies are a Fijian and Samoan species, W. vitiensis 
and W. samoensis. Possibly, he remarks, fuller materials may 
lead to the union of several of these forms under one species. 

The interesting New Zealand genus Coprosma, which we have 
noticed in Hawaii, occurs also in the Tahitian region and Fiji ; 
and it will be further discussed under the last-named locality. 
The genus Vaccinium has been previously dealt with in Chapter 
XXIII. 

The Liliaceous genus Astelia may be considered as represent- 
ing, like Coprosma, the Antarctic or New Zealand flora in the 
higher levels (usually) of the islands of the tropical Pacific, where it 
grows both on trees and on the ground. The genus, according to 
Hemsley, is chiefly at home in New Zealand, but is also found in 
Fuegia and in South-east Australia. It is represented in Hawaii, 
Tahiti, Samoa, and Fiji. In Hawaii there are two peculiar species 
ranging between 2,000 to 6,000 feet in elevation. The solitary 
Tahitian species, A. nadeaudi, is found in the central mountains of 
Tahiti, reaching to the crests of Mount Aorai, which attains a 
height of 6,700 feet. Fiji and Samoa possess a species in common, 
A. montana, which is only recorded by Seemann, from the summit 
of Kandavu, 2,750 feet above the sea ; whilst in Samoa it frequents, 
according to Reinecke, moist coast districts. The fruits of Astelia 
are berries with crustaceous seeds that would be dispersed by 
frugivorous birds. 

Amongst the Tahitian mountain-genera that possess species 
ranging far beyond this region as well as species confined to the 
group may be mentioned Coriaria and Cyathodes. It is to their 
non-endemic species that we look for further clues as to the 
general lines of migration by which the mountain-genera that only 
possess peculiar species reached this group. The evidence afforded 
by Coriaria is of some importance. The genus has not been 
recorded from Hawaii, and, so far as the collections of Seemann 
and Home show, not from Fiji. It is found in the Mediterranean 

U 2 



292 A NATURALIST IN THE PACIFIC CHAP. 

region, the Himalayas, Japan, New Zealand, and Antarctic 
America, including Chile ; and there are two particular species, 
C. ruscifolia and C. thymifolia, that occur in both cases in New 
Zealand and the adjacent islands and in South America (Introd. 
Chall. Bot. p. 53). The first of these, which is very common in 
Chile, exists also in Tahiti on the crest of Aorai, 6,700 feet above 
the sea. Drake del Castillo also describes a peculiar Tahitian 
species, C. vescoi, of which the altitude is not given. Here one is 
in doubt whether Tahiti derived its wide-ranging species from New 
Zealand or from Chile ; but in the New Zealand home of 
Coprosma, another Tahitian mountain-genus, we are afforded the 
clue. The fruits of Coriaria possess fleshy cocci that attract birds, 
though it would seem that the seeds of plants of this genus are 
poisonous for man. Among the numerous fruits that form the diet 
of the New Zealand fruit-pigeon (Carpophaga novae zealandiae) are 
included, as we learn from Sir W. Buller in his Birds of New 
Zealand, those of the " tupakihi " or " tutu " shrub, which Kirk 
identifies with C. ruscifolia, the species that also occurs on the 
summit of Tahiti. 

The Australian and New Zealand genus Cyathodes (Epacri- 
daceae) has been already noticed in the case of Hawaii (page 282). 
The two Tahitian species occur on the elevated mountain-ridges 
forming the summits of Tahiti, one of them, C. tameiameiae, occur- 
ring also in Hawaii, and the other, C. pomarae, being restricted to 
the group. I have shown that the fruits are dispersed by frugiv- 
orous birds, and I can only include the genus as another example of 
the representation of the New Zealand flora in Tahiti .... There 
remain of these so-called Tahitian mountain-genera the Antarctic 
Nertera and the north-temperate Luzula, each represented by 
a solitary widely ranging species, N. depressa and L. campestris, 
which I have fully discussed under Hawaii (Chapter XXIII), in 
which group they also occur. 

When we look at the evidence of origin supplied by the 
four Tahitian mountain-genera possessing species that are found 
outside the group, namely Coriaria, Cyathodes, Nertera, and 
Luzula, we find that the first three hail from high southern 
latitudes, and more especially from New Zealand ; and when with 
this clue in our hands we take up the four genera Weinmannia, 
Coprosma, Vaccinium, and Astelia, possessing only species 
restricted to the Tahitian region, we find that all but the third- 
named genus hail also from the south. It would thus appear that 
the element of the Antarctic flora is much more evident in the 



xxiv THE TAHITIAN MOUNTAIN FLORA 293 

Tahitian mountain-genera than with those of Hawaii. In the 
Hawaiian mountain-flora, excluding, of course, the endemic genera, 
it includes about a fourth of the mountain-genera, which number 
about thirty-eight or forty in all ; whilst in the Tahitian mountain- 
flora it comprises six out of the eight genera. It may, indeed, be said 
that the resemblance between the mountain-genera of Hawaii and 
Tahiti is mainly restricted to genera that are found in high southern 
latitudes, namely, Nertera, Coprosma, Cyathodes, and Astelia, the 
only other genera linking the mountain-floras of both groups 
together being Vaccinium and Luzula, which probably hail from 
high northern latitudes. The agency of the frugivorous bird 
is plainly marked in the case of five out of the six genera that 
connect the cloud-capped peaks of Tahiti and Hawaii. In two of 
these genera, Cyathodes and Nertera, the same species occurs 
in both archipelagoes. 

The Mountain-flora of Rarotonga. A word may here be said on 
the representation of these mountain-genera in Rarotonga, a small 
island 2,250 feet in height and about eight miles in length, which 
is, however, the most important island of the Cook group. The 
recent important explorations of Mr. Cheeseman show that its flora 
is essentially Tahitian in character. As in Tahiti, the early age of 
the Compositae and Lobeliacese is well represented in the high 
levels by peculiar species of Fitchia and Sclerotheca which are dis- 
cussed in Chapters XXI and XXII. On account, however, of its 
relatively low altitude and its small size, we could not expect any 
extensive representation of the eight non-endemic mountain-genera 
of Tahiti. Yet three of these occur, a Tahitian species of Vac- 
cinium (page 281) growing on its summits, whilst peculiar species of 
Weinmannia (page 290) and Coprosma (page 295) are found in its 
interior. The prevailing condition of many of the genera growing 
in the higher levels is one of isolation, since other genera, like Pittos- 
porum and Elaeocarpus, only possess peculiar species ; but seeing that 
in several cases the species are closely allied to others found in the 
Western Pacific, as in Samoa, Fiji, and the Kermadec group, it is 
apparent that the period of isolation has not long commenced. 



THE MOUNTAIN-FLORA OF THE FIJIAN REGION. 

Weinmannia, Saxifragaceae, Fiji and Samoa. \ Derived from 
Lagenophora, Compositae, Fiji. / New Zealand or 

Coprosma, Rubiaceae, Fiji. C from the 

Astelia, Liliaceae, Fiji and Samoa. J Antarctic flora. 



294 A NATURALIST IN THE PACIFIC CHAP. 

Vaccinium, Vacciniaceae, Samoa, from the northern hemisphere, 
Nertera depressa, Rubiaceae, Samoa, from the Antarctic flora. 
Dammara, Coniferae, Fiji. -\ Not as a rule belonging; 

Podocarpus, Coniferae, Fiji and Tonga, v to the present age 
Dacrydium, Coniferae, Fiji. j of dispersal. 

But little can be said of the mountain-flora of Fiji, since on 
account of the relatively low elevation of the islands there are but 
few special mountain-genera ; and as a rule we find only here and 
there a solitary species on some isolated peak that recalls the 
upland flora of the Hawaiian mountains. " None of the mountains 
of Fiji," remarks Home (page 60), " are high enough for an alpine 
flora to exist. Many of the plants found on the tops of the moun- 
tains are also found near the level of the sea. On the other hand 
sea-level plants may also be found on the tops of the hills." 

Fiji lacks the endemic genera of Compositae and of Lobeliaceae- 
that often give a character to the mountain-floras of the Hawaiian 
and Tahitian regions, though, as remarked in Chapters XXI and 
XXII., their absence involves something more than a question of 
station. We find, however, four genera of the Antarctic or New 
Zealand flora, Weinmannia, Lagenophora, Coprosma, and Astelia. 
The first-named genus possesses four or five species ranging up to- 
2,000 feet, some of which are endemic, and it has been already 
discussed in this chapter. The United States Exploring Expedi- 
tion found a single species of Lagenophora (L. pickeringii) on the- 
mountains of the Mathuata coast of Vanua Levu, and no other 
species seems to have since been found. The subject is dealt with 
in Chapter XXIII in the case of Hawaii, but it may be here 
observed that there is an Hawaiian mountain species, and that the 
route followed by the ancestor of the Fijian species from the New 
Zealand home of the genus is indicated by a species in the inter- 
mediate Kermadec group. The genus Astelia has been discussed 
on page 291. It is represented in Hawaii and in most of the oceanic 
groups of elevated islands. . The solitary species, A. montana, 
discovered by Seemann on the summit of Kandavu in Fiji, has 
since been found in Samoa, and probably Mr. Home's collections 
contain another species. 

The Rubiaceous genus Coprosma needs a few special remarks, 
since a particular genus of birds seems to have been concerned in 
dispersing it in the South Pacific. About fifty species are 
enumerated in the Index Kewensis, and if we include a few other 
species from the collections of Hillebrand, Home, Cheeseman^ 



xxiv THE FIJIAN MOUNTAIN FLORA 295 

&c., the total would be about sixty. Of these, about half are 
restricted to New Zealand, which may be justly regarded as the 
home of the genus, the rest being confined to Australia and the 
islands of the Pacific, excepting a Chilian and three or four 
Malayan species. Hawaii with its nine species, Tahiti with two, 
Rarotonga with one, and Fiji with two or three species represent 
approximately the distribution of the genus in the oceanic archi- 
pelagoes of the tropical Pacific. (It most probably exists on the 
high peaks of Samoa, though it has not yet been recorded from the 
group.) In all, or in almost all cases, the species are restricted 
to their particular groups, so that we may regard the dispersal of 
the genus over the Pacific as suspended, though, as will be observed 
below, the period of suspension in the South Pacific has not been 
of sufficient duration to obliterate the affinities of species in distant 
groups and to prevent us from tracing out the route followed by 
the genus. 

This genus of temperate latitudes, which in its New Zealand 
home ranges from near the sea-level to the region of the alpine 
floras, finds its usual station in the tropics on the summits of moun- 
tains. Thus, on Mount Kinabalu, in Borneo, it is found at altitudes 
of 10,500 to 13,000 feet (Stapf), and on the mountains of East Java 
at elevations exceeding 9,000 feet (Schimper). In Hawaii its 
species grow at elevations ranging from 3,000 to 9,000 feet, and in 
Tahiti at altitudes of 2,600 to 3,300 feet ; whilst in Rarotonga it 
grows in the hilly parts of the island, its elevation in Fiji not being 
recorded. 

When we come to consider the route by which the genus 
(Coprosma) entered the tropical Pacific, we must remember that 
unless we establish some special connection with its New Zealand 
home it will always be open for any one to suggest that the genus 
might have been derived, like Vaccinium, from other regions than 
the south, as from the summits of the Malayan mountains. How- 
ever, a curious connection has been discovered by Mr. Cheeseman 
in his examination of the Kermadec and Rarotongan floras, and it 
would indeed appear that he has traced the Rarotongan peculiar 
species to its New Zealand home. Thus, he says that Coprosma 
laevigata, his new Rarotongan species, is very closely allied to the 
Kermadec endemic plant, C. acutifolia, Hook., which itself comes 
near C. lucida, Forst, a New Zealand species. The connection 
between Rarotonga and New Zealand by way of the Kermadec 
group is rendered yet more probable by the occurrence of two 
New Zealand species of Coprosma in the Kermadec flora (Journ. 



296 A NATURALIST IN THE PACIFIC CHAP. 

Linn. Soc. i. 1857; Trans. Linn. Soc. Bot. vi. 1903; Trans. N.Z. 
Instit. xx. 1887). 

When speaking of the genus in Hawaii (page 275), mention 
was made of the inter-island dispersal of the fruits of one of 
the species by the native mountain-goose, Bernicla sandwicensis. 
We learn from Sir W. Buller's History of the Birds of New 
Zealand that when the Coprosma is in fruit the Swamp-Hens 
(Porphyrio melanotus) come out to feed on it. These birds, 
he says, are capable of prolonged flight ; and I chance to have 
beside me a cutting from the Field of July 9, 1904, in which 
" Hy. S." refers to a Black-backed Porphyrio that was captured 
in 1876 four hundred miles off the coast of New Zealand. This 
genus, which is widely dispersed in the tropics, the birds being 
commonly known as Sultanas, Blue Gallinules, Purple Water- 
Hens, &c., has probably been a very important factor in the 
dispersal of plants, especially in connection with insular floras. 
The birds live on a variety of food. The Messrs. Layard 
observed that Porphyrio vitiensis, which abounds in the swamps 
of New Caledonia, fed on maize, yams, &c. (Ibis, 1882) ; whilst 
in the stomach of a bird of the same genus shot in the Rewa 
swamps in Fiji I found a number of the stony fruits of Scleria, 
a genus of the Cyperaceae. According to Mr. Wiglesworth, each 
region in the South Pacific has its own species of Porphyrio. 
There is one in the Tahitian Islands, and another common to 
Fiji, Tonga, and Samoa ; whilst New Caledonia and the New 
Hebrides have their species (" Aves Polynesian "). However, it is 
evident that the power of dispersing seeds from group to group is 
not quite suspended, since, as we learn from Sir W. Buller, the 
New Zealand species, above named as partial to Coprosma drupes, 
is distributed over Tasmania and Australia, and reaches also Niue 
and New Caledonia ; whilst the Messrs. Layard evidently re- 
garded one species as common to Fiji and New Caledonia. 

It is doubtless to birds of this description that we owe some of 
the specific connections of Coprosma between groups of the Western 
Pacific. That the dispersal of the species over distant regions was 
recently in active operation is shown by the close affinity, according 
to Dr. Stapf, of two species growing on the summit of Kinabalu, the 
Bornean mountain, with certain species from New Zealand and 
South-east Australia. Other Rubiaceous species, like Nertera 
depressa, possessing Coprosma-like fruits and fitted for the same 
mode of dispersal, link the heights of Kinabalu with the flora of 
high southern latitudes. 



xxiv THE FIJIAN CONIFERS 297 

Being included in the Fijian area, the scanty mountain-flora of 
Samoa may be here referred to. As in Fiji, the endemic genera 
of Compositae and Lobeliaceae are not to be found, but we find in 
the central elevated district of Savaii, which rises to over 5,000 feet 
above the sea, a peculiar species of Vaccinium (4,900 feet), the 
Antarctic Nertera depressa (4,000 feet), and two species of Wein- 
mannia, a genus hailing probably from high southern latitudes. 



THE FIJIAN CONIFERS. 

It has been found most convenient to discuss here these 
interesting plants, which belong in a general sense to the mountain- 
flora of this archipelago. That which the Fijian flora loses in 
interest in the eyes of the student of plant-dispersal in not 
possessing the mysterious Composite and Lobeliaceous genera 
of Hawaii and Tahiti, it regains in the possession of its genera 
of Coniferae. If he felt loth to apply his empirical principles 
to the above-named Hawaiian and Tahitian endemic genera, he 
feels more than uneasy when he comes to deal with the three 
Coniferous genera of Fiji, Dammara (Agathis), Podocarpus, and 
Dacrydium. 

These three genera represent an order that has not found a 
home either in Tahiti or in East Polynesia generally, or in the 
more distant Hawaii ; and they present at first sight in their 
existence in Fiji a powerful argument in favour of the previous 
continental condition of the islands of the Western Pacific. But in 
advocating this view we should remember that it involves the 
original continuity of the Fijian land-area, not only with the 
neighbouring islands of the New Hebrides and of New Caledonia 
where these genera alike occur, but also with New Zealand, 
Tasmania, and Australia, where they sometimes attain a great 
development. 

In Fiji these trees often chiefly form the forests of the larger 
islands, extending in the moister regions from near the sea to the 
mountain-tops, and being often abundant on the great mountain- 
ridges of the interior. It may be at once remarked that, viewed 
merely from the standpoint of dispersal, there is no great difficulty 
in regarding it as probable that the seeds of Podocarpus and 
Dacrydium have been dispersed by frugivorous birds over tracts of 
ocean 500 or 600 miles across. Dammara, however, so far as my 
Fijian observations show, possesses none of the means of dispersal 



298 A NATURALIST IN THE PACIFIC CHAP. 

across oceans that we are at present acquainted with. The two 
first-named genera occur in South America as well as in the 
Australo-Polynesian region, some of the species in these two 
regions, though the Pacific Ocean divides them, being closely 
related. Dammara is, on the other hand, confined to a much more 
limited area, extending from New Zealand to Borneo. It is from 
the distribution of this genus that the continental theory derives its 
chief support. 

Yet it may be remarked that something more than questions 
relating to the capacity for dispersal are involved here. This is at 
once indicated by the circumstance that although Podocarpus is 
known to be dispersed by frugivorous birds, it is not found in 
Polynesia east of Tonga, and the same may be said of Dacrydium, 
which does not occur east of Fiji. In this connection it is 
necessary to notice the intrusion of Araucaria into the tropical 
Pacific from Eastern Australia to New Caledonia and the New 
Hebrides. The fact of this genus not having been recorded from 
Fiji or any of the groups east of the New Hebrides is very 
remarkable, and scarcely in accordance with the continental 
hypothesis. There is a persistence in type of these genera of the 
Coniferae during geological time that prevents us from dealing with 
them on the lines that are required by the mass of the flowering- 
plants. Other factors intervene, and we apply with hesitation the 
same canons of dispersal that we employ for the general bulk of 
the plants of the Pacific islands. If, as often happens, a specific 
distinction alone separates the Conifers of the same genus on 
either side of the Pacific Ocean, it must possess in point of 
time a very different value from that which we would usually 
attach to specific distinctions in the floras of the Pacific islands. 

DAMMARA (AGATHIS). The Dammara region includes 
Eastern Australia, New Zealand, New Caledonia, with the New 
Hebrides, Fijian, and Santa Cruz groups, and extends north-west 
to Java and Borneo. Only ten species are named in the Index 
Kewensis, and of these four are assigned to New Caledonia and 
two to Fiji, the focus of geographical distribution being, therefore, 
as Seemann long since pointed out, in the islands of the Western 
Pacific. The absence of the genus from the neighbouring Samoan 
and Tongan groups is very significant ; and it is evident that the 
ordinary agencies of dispersal, whether birds, winds, or currents, 
have here failed to extend the genus over a few hundred miles 
of sea. 

When by means of observation and experiment we turn to the 



xxiv THE FIJIAN CONIFERS 299 

fruits and look for a reply, we find in the first place that they are 
never to be noticed either whole or in part in the floating drift of 
sea or river, or amongst the stranded materials of the beaches. 
This is at once explained when we ascertain that the fresh cones 
sink in the river-water, and thus could never reach the coast in their 
entire condition. Nor could they do so in fragments, since the 
detached cone falls to pieces on the ground and the separate scales 
and seeds sink at once or float only for a few hours. In order to 
test the buoyancy of a cone after drying, it is necessary to bind it 
round with string to keep it from breaking down. One such fruit, 
after being kept for ten days, was placed in sea-water, where it 
floated heavily for eleven days and then sank. This is, of course, a 
most unnatural experiment, but it was well to have carried it 
out. That the entire fruit could never be transported by water is 
indirectly implied by Kirk respecting the fruit of Dammara 
australis, the Kauri Pine of New Zealand. In this case, when the 
fruit reaches maturity the scales, he remarks, fall away from the 
woody axis of the cone and the seeds are freed. 

The fleshy, unprotected seeds, which, as above noted, possess 
little or no floating power, could scarcely withstand the injurious 
effect of sea-water ; and they are absolutely unfitted for any known 
mode of dispersal by birds. It is observed by Kirk that the seeds 
of the New Zealand tree are widely spread by winds. But this 
could only avail them for local dispersion, and they appear ill-suited 
for being transported for more than a few paces. The seeds are 
winged, and are in form a little like the samara of the Maple 
(Acer) ; but they have not the same protective coverings, the wing 
being, however, only a little more than half the length of the 
entire seed. Those of both Dammara australis and D. vitiensis are 
about' two-thirds of an inch in length, and are heavy-looking ; and 
the agency of the wind could never be invoked except for local 
dispersion. 

Looking at these results, the cones of Dammara may be re- 
garded as most unsuited for any of the ordinary means of dispersal 
over an ocean except through the agency of man. There is, how- 
ever, no necessity to introduce man's aid here, unless the gum or 
resin which the Fijian burns in his torches and employs as a glaze 
for his pottery gave his ancestors an object in carrying the cones 
with them in their migrations. But in that case the same argument 
would have to be applied to all partially useful plants, and much of 
the Fijian flora would lose its indigenous reputation. The endemic 
character of the Fijian species also militates against such a view, 



300 A NATURALIST IN THE PACIFIC CHAP. 

and we should have to apply the same explanation to the New 
Zealand species, concerning which no one, so far as I know, has ever 
ventured to suggest that it was introduced by the Maoris. 

The native names of the trees seem to have been sometimes 
connected with general words for gums or resins ; whilst at other 
times the tree and the resin have separate designations. Thus the 
Fijians call the tree " ndakua " and the resin " makandre," which 
last Hazlewood in his dictionary seemingly connects with 
" ndrenga," the word for " gum." In my work on the Solomon 
Islands, page 190, I have endeavoured to show that the Maori 
name of " kauri " may be connected with " gatah," the general 
Malayan word for gums and resins, transitional stages being 
presented in the names of resin-yielding trees in the intermediate 
regions, as, for instance, by " gutur," a species of Canarium, 
on the Maclay coast of New Guinea, and by " katari," a species of 
Calophyllum, in Bougainville Straits, Solomon group. It may be 
pointed out that these facts of plant-nomenclature do not promise 
us any aid in determining the mode of dispersion of Dammara in 
the Western Pacific. There is a suspicious resemblance between 
the Fijian name of " ndakua " and " dundathu," the Queensland 
aboriginal name for Dammara robusta ; but even if the comparison 
is legitimate, its explanation may lie far back in the ages in some 
root-word as ancient as the Malayan " gatah." 

If there is a real difficulty in applying our canons of plant- 
dispersal to the distribution of Dammara, it is merely the same 
difficulty that has so often perplexed the botanist with other 
Coniferous genera in continental regions, such as, for instance, the 
occurrence of Pinus excelsa on the far-removed mountains of 
Europe and of the Himalayas, and the existence of the cedar in 
its isolated homes on the Atlas, the Lebanon mountains, and the 
Himalayas. Such difficulties largely disappear if we regard the 
present distribution of the Coniferae as the remnant of what it was 
in an ancient geological period. In the case of Dammara it seems 
almost as idle to puzzle over its means of dispersal as to consider 
the mode of dispersal of the Marsupials. The questions, indeed, 
that affect the Dammaras of Fiji and the Western Pacific far 
ante-date any questions concerning a previous continental condition 
of those regions. The attitude of the palaeobotanist to such 
questions would probably be one of indifference; yet to the 
student of plant-distribution they are of prime importance ; and 
nolens volens we must admit that Dammara may well be cited 



xxiv THE FIJIAN CONIFERS 301 

in support of any continental hypothesis affecting the Western 
Pacific. 

PODOCARPUS. In this connection I will mainly depend on 
Pilger's recent monograph on the Taxaceae (heft 18, Engler's Das 
Pflanzenreich, 1903). More than sixty species are here enumerated, 
which are distributed in Africa, Asia, Australasia, and South 
America. With a range that extends north to Japan and south to 
Southern Chile in latitude 48, this genus attains its greatest 
development in respect of species in Malaya, in the region com- 
prised by Australia, New Zealand, and New Caledonia, in South 
America, and in Africa. Eastward of New Caledonia it is found 
in Fiji and in Tonga, but not in Samoa, and it is altogether absent 
from the Tahitian region as well as from Hawaii. Of the four 
species accredited by Seemann to Fiji, two are enumerated by 
Pilger, namely, P. affinis and P. vitiensis. The first-named, 
according to Stapf, is allied to P. bracteata, which occurs on the 
upper slopes of Kinabalu, in Borneo, and is distributed not only 
over Malaya, but occurs in Japan and in the Himalayas. The 
Tongan species, P. elatus, is, according to Hemsley, found in East 
Australia. 

This Tongan tree is suggestive of bird-agency in the dispersal 
of the genus, and the same may be said of the occurrence of 
another species, P. ferrugineus, found in both New Caledonia and 
New Zealand. Since the seeds of the genus possess an outer 
fleshy and an inner bony covering, they would appear to be well 
fitted both to attract and to be dispersed by birds. In fact, we 
learn from Sir W. Buller that the New Zealand fruit-pigeon feeds 
on the seeds of the " matai " tree (Podocarpus spicata) and of the 
"kahikatea" (P. dacrydioides), and no doubt to the agency of 
frugivorous birds we can attribute the presence of the genus in 
Fiji and Tonga. Yet it is strange that bird-agency should have 
failed both with Tahiti and Hawaii. In point of size the seeds, 
which range from one-quarter to an inch across, present no 
great difficulty, and one would have thought that the birds that 
carried the "stones" of Elaeocarpus to Hawaii could have also 
carried the seeds of Podocarpus. 

It is, however, necessary to remember, in dealing with a genus 
that has a wide distribution both in time and space, that specific 
affinities may have a very different significance with the Gym- 
nosperms than with most other flowering plants. When Hemsley 
remarks (Introd. Chall. Bot. p. 56) that the New Zealand Podo- 



302 A NATURALIST IN THE PACIFIC CHAP. 

carpus spicata is closely allied to the South American P. andina, 
he does not imply that the two regions are in touch with each 
other though some 5,000 to 6,000 miles of ocean intervene. One 
is prepared to credit these seeds with a capacity of dispersal by 
birds over tracts of sea such as the extent of ocean separating 
New Caledonia and New Zealand, which are some 900 miles 
apart ; but one hesitates to admit that frugivorous birds could 
carry them across the Southern Ocean. If we assign a home in 
the high latitudes of the northern hemisphere to a genus that was 
well represented in Europe in the Tertiary period, a movement of 
migration southward would explain most of the difficulties in its 
present distribution. The great vertical range of some of the 
species leads us to attribute a corresponding power of adaptation 
to the genus in respect of widely different climates. Thus, 
according to Stapf, the vertical range of P. bracteata in the Malay 
Archipelago extends, including varieties, from the coast to an 
altitude of 12,000 feet. With such a capacity for adaptation, 
migrations of the genus would be rendered easy over the globe. 

DACRYDIUM. It may happen that some additional light on 
the mystery of the Fijian Coniferae may be afforded by Dacrydium 
elatum, a tree that occurs not only in Fiji, but in Further India and 
in Malaya. Pilger confirms Seemann's view in his identification of 
the Fijian tree, and this opinion is, in the main, shared by Stapf. 
This species, so to speak, affords us a point d'appui in the history 
of the distribution of the genus in the Western Pacific. This 
distribution somewhat resembles that of Dammara in extending 
from New Zealand (its principal centre) to Malaya and Further 
India ; but, unlike Dammara, Dacrydium is represented in America 
by a solitary species in South Chile. Of the sixteen species 
enumerated by Pilger, seven belong to New Zealand, four to New 
Caledonia, three to Malaya, one to Tasmania, and one to Chile. 
The seeds are, as a rule, smaller than those of Podocarpus, and on 
account of their somewhat similar structure would serve as bird- 
food, and might be distributed in this fashion. Yet the genus has 
been only recorded from Fiji, and is not only unrepresented in 
Hawaii and Tahiti, but is also not known from the Tongan and 
Samoan groups that belong to the Fijian floral region of the 
Pacific. Capacities for dispersal appear meaningless here, espe- 
cially when we have regard to the solitary American species, 
Dacrydium fonkii, that as a shrub finds a refuge in the bleak 
region of Southern Chile. 



xxiv THE FIJIAN CONIFER/E 303 

The three Fijian genera of the Coniferae, Dammara, Podocarpus, 
and Dacrydium, appear at first sight to be beyond the reach of our 
canons of plant-dispersal, by which we connect specific affinity 
with a continuity of range, and by which we co-ordinate means of 
dispersal and area of distribution. We begin to realise that there 
may have been an age of Coniferae in the Pacific islands that 
is even less amenable to our methods than the later era of the 
Compositae and Lobeliaceae in Hawaii and Tahiti. Such an age 
would be concerned only with that region in the Western Pacific 
which is now held by the genera Dammara, Podocarpus, and 
Dacrydium, a region that did not participate in the era of the 
Compositae and Lobeliaceae. We thus have evidence of an ancient 
era of the Coniferae that was confined to the Western Pacific, and 
of a later era indicated by the peculiar genera of Compositae and 
Lobeliaceae that was restricted to Hawaii and to Eastern Polynesia 
(Tahiti, Rarotonga, &c.). The key to the situation here presented 
seems to lie in the following considerations. 

It is assumed that there was an age of Coniferae in the Pacific, 
or rather that this region shared in an era of dispersion of existing 
genera of the order. In this age only the islands of the Western 
Pacific participated, neither the Hawaiian nor the Tahitian islands 
taking a part in it. Such a result is to be attributed either to the 
inability of these genera of Conifers to reach Hawaii and the 
islands of East Polynesia, or to the non-existence of the Hawaiian 
and Tahitian archipelagoes at that epoch. The first explanation 
seems scarcely acceptable, since, although the powers of dispersal 
of the genus Dammara are very limited, there seems no reason 
why the genera Podocarpus and Dacrydium could not have 
reached those distant regions of the Pacific. The second explana- 
tion is most probable, and it is the one suggested by Hillebrand 
(p. xxx) in the case of Hawaii, namely, that " the absence 
of Gymnosperms militates for the view that the islands were 
formed subsequent to the age in which these were universally 
distributed." 

If this conclusion is legitimate we have here a datum-mark in 
the history of the islands of this ocean. Before the appearance of 
the Hawaiian and Tahitian islands (using the term Tahitian to 
cover the East Polynesian region) there existed a land-area in 
the Western Pacific held by the Coniferae, probably in the late 
Secondary period. After the formation of the Hawaiian and 
Tahitian islands, perhaps in the early Tertiary epoch, came the 
age characterised by the ancestors of the present endemic genera 



3 o 4 A NATURALIST IN THE PACIFIC CHAP. 

of the Compositae and Lobeliaceae, and of a few other orders in 
Hawaii and Tahiti. In this age the islands of the Western Pacific 
do not seem to have participated, and it is to be inferred that this 
was an age of extensive but probably not of complete submergence 
in that part of the ocean, since at least the genus Dammara was 
able in places to hold its ground. Then ensued the great Tertiary 
emergence of the land-areas of the Western Pacific, when small 
islands that dotted the sea-surface in this region became the nuclei 
for the formation of the large islands of the present Fijian, New 
Hebrides, and Solomon groups. This prepared the way for the 
migration of Malayan plants which now predominate over the 
islands of the tropical Pacific ; and in a later age man, following 
the same track from Indo-Malaya, occupied these islands. 

In my volume on the geology of Vanua Levu it was shown that 
the Tertiary period was an age of submergence in the Western 
Pacific, and a disbelief in any previous continental condition was 
expressed. My later view is more in accordance with that of 
Wichmann, who, on geological grounds, contended that the islands 
of the Western Pacific were in a continental condition during the 
Palaeozoic and Mesozoic periods, and that their submergence and 
subsequent emergence took place in Tertiary times. The distribu- 
tion of the genus Dammara has thus led me to modify the views 
expressed in the final chapter of my first volume on the geology of 
Vanua Levu. Though still holding that there is no geological 
evidence that the various islands of the Fijian group were ever 
amalgamated, or that they were joined as such to the westward 
groups, it is quite possible that their position was indicated by 
a few small islands a few miles across and a few hundred feet 
in height in early Tertiary times. On these small islands, which 
probably represented the remains of a submerged Mesozoic land- 
area, such as is in part implied in Dr. Forbes' Antipodea, or in 
Mr. Hedley's Melanesian Plateau, the genus Dammara survived. 
Such islands merely indicated the situation of some of the present 
groups of the Western Pacific, which have been since largely built 
up by submarine eruptions, and the greater number of the islands 
were no doubt completely submerged. Between the groups as we 
know them now there never was any land connection, since they 
are the product of later eruptions, mainly submarine ; and they 
have acquired their present composite character during the emer- 
gence that followed the period of volcanic activity. Except, per- 
haps, in New Caledonia, which does not seem to have shared in the 
Tertiary submergence, the islands of the Western Pacific have 



xxiv THE FIJIAN CONIFERS 305 

a configuration acquired in comparatively recent times, and one 
that gives no idea of the character of the Mesozoic continent. 

Such, as I understand them, are the indications of the Fijian 
Coniferae and particularly of Dammara. In the distribution of this 
genus we have outlined an ancient, more or less continuous land 
area which, with the exception of a few isolated points, disappeared 
beneath the sea in Tertiary times to re-appear near the close of 
that period in the form of a number of archipelagoes that were 
largely built up by submarine eruptions, and probably altogether 
mask the form of the original land-area. It may be remarked that 
New Zealand, which largely shared in the Tertiary submergence, 
especially in the Miocene age, is included in the range of the genus 
Dammara, as well as in those of the genera Podocarpus and 
Dacrydium. 

Summary. 

(1) The evidences of a mountain-flora in Tahiti, as indicated by 
the non-endemic genera, though, as we would expect, of a scanty 
nature when contrasted with Hawaii, are nevertheless of consider- 
able interest. There is much kinship with the Hawaiian mountain- 
flora, but it is mainly confined to genera from high southern 
latitudes, such as Nertera, Coprosma, Cyathodes, and Astelia, 
which are all dispersed by frugivorous birds. Amongst other 
plants linking the Tahitian mountains with the region of the 
Antarctic flora, and with New Zealand in particular, may be 
mentioned Coriaria ruscifolia and the genus Weinmannia. 

(2) On account of their relatively low altitude the Fijian islands 
do not present the conditions for an alpine flora. Traces, however, 
of the Antarctic flora, or of the New Zealand flora, occur on 
occasional mountain-tops, as is indicated by the occurrence of 
species of Lagenophora, Coprosma, and Astelia. In Samoa 
the mountain-flora is also scantily developed, as we might have 
expected ; but here occurs the genus Vaccinium as well as a 
widely-ranging species of the Antarctic flora, Nertera depressa. 

(3) The route by which some of the representatives of the flora 
of high southern latitudes reached the mountains of the islands of 
the tropical Pacific is directly indicated by the genus Coprosma to 
have been from New Zealand by way of the Kermadec Islands. 

(4) In the distribution of plants possessing drupes or berries 
that connect the tropical islands of the South Pacific with New 
Zealand, it is highly probable that birds of the genus Porphyrio 

VOL. II X 



3 o6 A NATURALIST IN THE PACIFIC CH. xxiv 

(Swamp-Hens or Purple Water-Hens) have taken a prominent 
part. 

(5) In the possession of species of the three genera of Coniferae, 
Dammara, Podocarpus, and Dacrydium, which often largely form 
the forests of the mountain-slopes, Fiji is distinguished from all the 
other groups of the open Pacific with the exception of Tonga, 
which owns a species of Podocarpus probably introduced by birds. 
From the circumstance that Dammara has no known means of 
crossing a tract of ocean, whilst Podocarpus and Dacrydium could 
be dispersed by frugivorous birds, all three genera having, however, 
much the same limited distribution in the Western Pacific, it 
is apparent that something more than a question of means of 
dispersal is here involved. It is assumed that they mark the site 
of a Mesozoic continental area in this region, and that at this period 
the Tahitian and Hawaiian groups which possess no Conifers did 
not exist. This area was submerged during the Tertiary period 
with the exception of a few peaks that formed small islands 
on which the Conifers held their ground. During the Tertiary 
submergence of the Western Pacific region, the Hawaiian and 
Tahitian islands were built up by subaerial volcanoes and received 
the ancestors of the Compositae and Lobeliaceae that now exist as 
endemic genera in those groups. Then followed the emergence of 
the islands of the Western Pacific and their occupation mainly by 
Indo-Malayan plants that extended eastward over the Pacific. 
Thus in the Pacific there has been first an age of Conifers in which 
the islands of the Hawaiian and Tahitian regions could not partici- 
pate, since they did not exist. Then ensued an era of American 
forms of Compositae and Lobeliaceae in which only Hawaii and 
Tahiti participated, since the Western Pacific region was sub- 
merged. Lastly came the invasion of Indo-Malayan plants, which 
have largely occupied every group in the tropical Pacific. 



CHAPTER XXV 

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING 

PLANTS (continued) 

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 Age of Wide Dispersal over the Tropical Pacific. 

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

WE pass now from the consideration of the mountain-flora of 
Hawaii and its scanty representation in the Fijian and Tahitian 
regions to a discussion of the low-level Hawaiian flora, belonging 
to stations under 4,000 or 5,000 feet, and of the corresponding 
floras of the other two regions. It has been previously pointed out 
that in mass the plants of Fiji and Tahiti correspond to the low- 
level flora of Hawaii. 

There are numerous ways of comparing this era of the non- 
endemic genera of these three regions of the Pacific. The necessi- 
ties of space, however, compel me to treat the subject only in an 
illustrative fashion, and in adopting the plan which seems easiest 
and simplest I have also been obliged to keep my limitations 
mainly in view. 

THE WIDELY-DISPERSED GENERA WHICH POSSESS ONLY 
PECULIAR SPECIES IN HAWAII. 

Amongst the oldest denizens of the Pacific islands in this era of 
the non-endemic genera may be taken those genera of flowering 
plants which are found in all three regions, Hawaii, Fiji, and 

X 2 



3 o8 A NATURALIST IN THE PACIFIC CHAP. 

Tahiti, but possess in the first group only endemic species, whilst 
in the other two regions they may include species both confined to 
and occurring outside the respective groups. They represent an 
age of wide dispersal over the Pacific, an age which for Hawaii 
has long since passed away, since all the genera have been discon- 
nected from the outer world, whilst in the groups of the South 
Pacific they as a rule in each case remain in touch through some of 
the species with the groups around. 

The problem of plant-distribution in the Pacific thus assumes a 
different aspect in an age which we term Malayan or Indo- 
Malayan, since the bulk of the plants are thence derived. The 
earliest age of the Coniferae was, as we have seen in the previous 
chapter, restricted to the region of the Western Pacific. The 
following age of the Compositae and the Lobeliaceae was concerned 
with the regions of Tahiti and Hawaii. Now, however, in the 
Malayan era, the whole of the tropical Pacific is concerned. Yet, 
although we shall still regard, for purposes of convenience, the 
groups of Fiji, Tahiti, and Hawaii as the three foci of plant- 
distribution, it will soon become apparent that in future there will 
be in reality only two regions to deal with, the Hawaiian in 
the North Pacific, and the whole region of the South Pacific 
extending from Fiji to Tahiti and as far east as the islands 
stretch. It will be also seen that in making our comparison 
we shall sometimes have to regard each of the principal Hawaiian 
islands as the equivalent as a plant-centre of an entire archipelago 
of the South Pacific. 

The genera that are here selected to represent this epoch 
of wide dispersion are very characteristic of the floras of the 
Pacific islands. Genera like Pittosporum, Gardenia, Psychotria, 
Cyrtandra, Freycinetia, and others one meets with everywhere in 
the larger islands, and it should be observed that they are predomi- 
nantly Old World, and more especially Malayan, in their origin, 
not a single purely American genus, unless we except the decadent 
genus of fan-palms, Pritchardia, occurring among them. Here we 
notice [what we shall see is especially typical of the era of the non- 
endemic genera, excepting those of the lofty uplands of Hawaii] 
that the frugivorous bird has been the principal agent in dispersing 
the plants, quite two-thirds of the total genera possessing drupes 
or berries that would attract such birds. The transport of seeds 
or seedvessels in birds' plumage, which was a conspicuous feature 
in the case of the mountain-flora of Hawaii, is not a feature of this 
age of wide dispersal of tropical plants over the Pacific. 



xxv PITTOSPORUM 309 

The genera selected to represent this age are given in the 
following table. Those on which my observations directly bear, or 
in which I was particularly interested when in the Pacific, will be 
discussed in detail from the standpoint of dispersal ; whilst only a 
brief reference will be made to a few of the others, not, however, 
from lack of materials at my disposal, but merely to keep this 
volume within moderate bounds. 

Genera selected to represent the Age of Wide-dispersal of Indo- 
Malayan or Malayan Plants over the Pacific, and possessing in 
Hawaii only Endemic Species. Most of the genera of this age are 
exclusively from the tropics of the Old World, whilst those found 
on both sides of the Pacific can be shown in most cases to have 
been derived from the same source, and only very few, like 
Pritchardia, can be traced to America. 

Pittosporum (Pittosporeae). 
Sapindus (Sapindaceae). 
Reynoldsia or Trevesia (Araliaceae) 
Gardenia (Rubiaceae). 
Psychotria (Rubiaceae). 
Cyrtandra (Gesneraceae). 
Phyllanthus (Euphorbiaceae). 
Pritchardia (Palmaceae). 
Freycinetia (Pandanaceae). 



PITTOSPORUM (Pittosporeae). 

This genus, which contains nearly a hundred species, usually of 
small trees, is widely spread in the warmer regions of Africa, Asia, 
Australia, and New Zealand. It is also especially a genus of 
oceanic islands, occurring not only in those of the Pacific but also 
in Madeira and Teneriffe in the Atlantic. 

Though found in most of the larger Pacific groups, it has 
apparently never been recorded from Samoa. From Hawaii 
ten species are known, all peculiar to that group. About half 
a dozen have been described from Fiji, of which three at least have 
been observed outside the group in the neighbouring Tongan 
Islands. Rarotonga possesses a peculiar species which, however, is 
so near to two other Fijian and Tongan species that, according to 
Cheeseman's memoir, they may have to be subsequently united. 
Tahiti is credited by Drake del Castillo with a solitary species 



3 io A NATURALIST IN THE PACIFIC CHAP. 

widely distributed in the Old World, whilst in the Index Kewensis 
a peculiar species is assigned to it. They form small trees of the 
wooded mountain-slopes of Fiji ; whilst in Hawaii, beside occur- 
ring in the lower forests, they may extend to altitudes of between 
5,000 and 7,000 feet. In the connection that more or less exists 
between the species of the South Pacific archipelagoes, and in the 
endemic character of all the Hawaiian species, we see the principle 
exemplified that there are two regions of distribution in the islands 
of the tropical Pacific the Hawaiian region and the South Pacific 
region. 

Before their dehiscence, the wrinkled, woody capsules would 
seem very unlikely to attract birds ; but the observer on handling 
an opening fruit, with its orange or brightly coloured lining 
and displaying black or dark-purple seeds immersed in a semi- 
liquid pulp, would form a different idea of the plant's capacity for 
this mode of dispersal. The mature dehiscing fruits are very con- 
spicuous on the tree ; and the seeds covered with the " sticky " 
material of the pulp might possibly adhere to birds pecking at the 
fruit. But this would only aid in local dispersion, since the weight 
and size of the seeds, 5 to 8 millimetres (^ to -^-inch), would unfit 
them for this mode of transport across an ocean. They are, 
however, sufficiently protected by their hard tests to be able to 
pass unharmed through a bird's intestinal canal. 

Yet the distribution of the species of Pittosporum in the Pacific 
would show that their dispersal is more a matter of the past than of 
the present. Out of the ten peculiar Hawaiian species, Hillebrand 
designates none as generally distributed over the group. But it is 
evident that, though it is on the point of breaking off, some sort of 
connection still exists in the South Pacific between the Tongan and 
Fijian species, and until recently between the species of those two 
groups and of Rarotonga. 

REYNOLDSIA (Araliaceae). 

The Polynesian genus of Reynoldsia, originally established 
by Gray, is merged by Hooker and Bentham into the Malayan 
genus Trevesia, a step that brings the Pacific plants into line with 
many other of the plants hailing originally from the Old World. 
The significant fact in the distribution of this genus of small trees 
in the Pacific is that its dispersal over the ocean has ceased long 
ago, since the three species here occurring are restricted each to a 
particular group, namely, to Hawaii, Tahiti, and Samoa. Yet the 



xxv GARDENIA 311 

inter-island dispersal still continues in the Hawaiian Group, the 
species characteristic of that archipelago being found in all the 
islands. 

Reynoldsia sandwicensis came frequently under my notice 
in Hawaii, and the fairly fleshy drupes, about one-third of an inch, 
or 8 millimetres, in size, with their crustaceous pyrenes appeared to 
me well fitted for assisting the dispersal of the plant by frugivorous 
birds. Yet here the same question arises that presents itself with 
so many other Hawaiian plants, and that is, How has it happened 
that the birds have continued to disperse the species over the 
scattered islands of this group long after they ceased to transport 
fresh seeds from the outside world ? The answer is an obvious one. 
The birds that originally brought the seeds of the parent species 
from some distant region came at last to remain permanently 
in the Hawaiian Group, and not only the plant but probably also 
the bird has since undergone specific differentiation. This link 
between bird and plant in the floral history of a group of Pacific 
islands is the common theme of the story of most of the endemic 
species of plants in this region of the globe. 

GARDENIA (Rubiaceae). 

This genus, comprising about a hundred known species, is 
spread over tropical Africa, Asia, and America, and over all the 
groups of the tropical Pacific. On account of their handsome, 
white, scented flowers these shrubs are much appreciated by the 
Pacific islanders, who employ the flowers for personal decoration. 
Some ten species have been described from the groups of the open 
Pacific, all of which, with the exception of Gardenia tahitensis, 
which ranges the South Pacific from Fiji to the Marquesas and 
Tahiti, are seemingly peculiar to the different archipelagoes. 
Thus there are some six species endemic to Fiji, one to Samoa, 
and two to Hawaii. 

The Hawaiian Islands are, however, quite isolated in this 
respect, since the group possesses only peculiar species ; whilst 
a solitary species keeps up the connection between the groups on 
the south side of the equator. The Gardenias thus tell the 
same story of complete isolation in Hawaii, and of partial isolation 
in the archipelagoes of the South Pacific that is repeated by many 
other Pacific genera. Yet in Hawaii there has subsequently been 
some inter-island dispersal, since the species are not restricted each 
to a single island, but are found on two or three islands. The 



3 i2 A NATURALIST IN THE PACIFIC CHAP. 

significance of the relation of the Hawaiian Gardenias to those of 
the combined Fijian and Tahitian areas consists in regarding the 
two regions, the Hawaiian and the South Pacific, as of equivalent 
value, and each large Hawaiian island as equivalent to one of the 
southern archipelagoes. 

The Station of the Pacific Gardenias. Although they may occur 
in the forests, the Gardenias of the Pacific are most characteristic 
of dry, thinly vegetated localities, and they have an inclination for 
the vicinity of the coast. In the Tahitian Group, as we learn from 
the writings of Nadeaud and Drake del Castillo, Gardenia tahiten- 
sis thrives much better on coral islands than on volcanic soils, and, 
in fact, rarely quits the " region madreporique" It is sometimes 
planted in Polynesia near the houses, and both Nadeaud in Tahiti 
and Cheeseman in Rarotonga consider that it was probably intro- 
duced into those islands before the arrival of Europeans. The 
aborigines may have assisted in the dispersal of the genus to 
a small extent, but from the presence of peculiar species in 
Hawaii, Samoa, and Fiji it is apparent that the genus is truly 
indigenous in the Pacific islands, and long antedated their occupa- 
tion by man. This is also evident from the station of the 
species in Hawaii, Samoa, and Fiji. In Hawaii they may be 
found on the dry forehills in the vicinity of the sea-border. In 
Samoa, as Reinecke informs us, Gardenia tahitensis is very widely 
spread in the mountain-forests, whilst the endemic species is found 
thriving in inundated coast districts. In Fiji I found the Gardenias 
to be especially characteristic (as is also pointed out by Home) of 
the dry districts on the leeward side of the larger islands. On the 
rolling " talasinga " or " sun-burnt " plains of the north side of 
Vanua Levu they thrive in numbers ; and here their leaf-buds and 
the extremities of the young shoots are often tipped or covered 
over with an amber-like gum-resin which the natives chew. 

The Mode of Dispersal of the Pacific Gardenias. The fruits 
of this genus are usually described as indehiscent. If this were true 
of Pacific plants it would be very difficult to explain the dispersal 
of hard, dry fruits an inch in size over this region. In the case of 
two or three Fijian species, I paid especial attention to this point 
by examining the plants in fruit. As exhibited in Fiji the fruits 
are globose, hard, and almost stony, with persistent adherent calyx, 
the seeds lying horizontally in a pulp at first firm and subsequently 
softening as the fruit matures. The fruits are not as a rule to 
be observed opening on the plant ; but they are to be seen 
dehiscing septicidally on the ground beneath, the detached woody 



xxv GARDENIA 313 

valves being scattered around. If one of the fruits gathered from 
the plant is kept soaking in water for some time it will begin 
to dehisce ; and this is probably what occurs with fallen fruits 
in wet weather. Dr. Hillebrand regards the fruits of the Hawaiian 
species as indehiscent. I did not myself examine them, but it 
is not improbable that, like those in Fiji, they dehisce whilst lying 
soaking on the ground. 

Judged merely from the dispersal standpoint, the fruits of the 
Fijian Gardenias come near to those of Pittosporum, and both can 
be in a sense described as baccate capsules. The flat, crustaceous 
seeds of Gardenia, which are usually two or three millimetres in 
size, are also well fitted for passing without injury through the 
digestive canal of a bird. It is likely that the two genera have 
been dispersed in the Pacific by the same kind of birds ; and 
it should be remarked that their distribution is somewhat similar, 
both belonging to the warm regions of the Old World. 

It might at first appear from some experiments of mine made 
in Fiji that the dried fruits of Gardenia could be dispersed over 
oceans by the currents. This receives some support by the 
preference for a littoral station sometimes shown by G. tahitensis 
in Tahiti, and by the occurrence of G. zanguebarica in the East 
African strand-flora (Schimper's Ind. Mai. Strand-flora^ p. 131). 
It will, however, be pointed out that currents could only have 
aided the dispersal of the genus to a limited extent. The fresh 
fruits of Fijian species, with or without the adherent calyx, have 
little or no buoyancy, and the seeds sink even after drying for 
months. But it was ascertained that fruits which had been kept 
for three months floated after four or five weeks' immersion in sea- 
water. On examination, however, it was found that the valves 
gaped a little, being only held in apposition by the adherent calyx, 
and that water had penetrated into the interior, the pulp being in 
a state of decay. The fruits were, in fact, kept afloat in the latter 
part of the experiment partly by the investing calyx and partly 
by gas generated in the decomposing pulp. Ultimately they broke 
down altogether and the seeds sank. In the " rough-and-tumble " 
of ocean-transport this could scarcely be deemed an effective means 
of dispersal ; and in the open sea a fortnight would probably 
represent the limit of the floating power. It is to the agency that 
has distributed the genus Pittosporum over the Pacific that we 
must look for the explanation of the dispersal of Gardenia over the 
same ocean, namely, to birds. 



314 A NATURALIST IN THE PACIFIC CHAP. 



PSYCHOTRIA (Rubiaceae). 

We find in this large genus of the Old and New Worlds a 
typical example of the plants with fleshy drupes containing hard 
pyrenes that represent, from the standpoint of dispersal, a common 
Rubiaceous type of plant in the tropical Pacific. Such plants, 
of which those of Coprosma and Nertera may be cited as other 
instances, are in a generic sense always widely distributed in these 
islands. They are eminently suited for dispersal by frugivorous 
birds ; and it is a matter for surprise, therefore, that in a genus 
like Nertera the solitary Pacific species has such a wide range, 
whilst with Psychotria and Coprosma the numerous species are 
usually restricted to particular groups. Genera doubtless have 
their periods of development and decadence in the Pacific, and 
probably Nertera is to be regarded as a decadent genus. These 
Rubiaceous genera, however, appear to be well fitted for the 
investigation of the centres of dispersal of particular genera and of 
their relative age. 

The Psychotrias in these islands are typically shrubs of the 
shady woods, and they may be seen thriving best where the forest- 
growth is rank and the humidity greatest. Their bright red ovoid 
drupes, which range from eight to twenty-five millimetres in length 
(J to I inch), would readily attract birds, and their crustaceous 
pyrenes, that vary between five and eight millimetres (-J- to J inch) 
in length, would pass unharmed through a bird's digestive canal. 
That fruit pigeons can distribute their seeds over the Pacific has 
been long established, and Mr. Hemsley includes Psychotria 
amongst those genera which, from the collections of fruits and seeds 
found in the crops of fruit-pigeons, made by Professor Moseley, 
myself, and others, in the groups of the Western Pacific, are " known 
to be dispersed by birds in Polynesia" (Introd. Bot. Chall. Exped., 
p. 45). It is thus hardly necessary to point out that neither the 
entire fruits nor the separate pyrenes could be transported by the 
currents, my observations showing that in both cases they sink at 
once or in a day or two. 

Psychotria, however, is an enormous genus including, according 
to the Index Kewensis, some 600 or 700 described species, dis- 
tributed in the tropics all over the world, and also extending into 
subtropical regions, the greatest concentration being in America. 
It is described in the Genera Plant arum as a polymorphous genus 
distinguished by no certain characters from some other genera of 



xxv PSYCHOTRIA 315 

the tribe of the Rubiaceae to which it has given its name. We have 
here a genus that has overrun the tropical regions of the world, 
probably originating in America ; and we may contrast it with the 
relatively small Rubiaceous genus of Coprosma (with its three 
score of species, and quite comparable with it from the stand- 
point of capacity for dispersal), that, having its birthplace in New 
Zealand, is only beginning to reach the mainlands of the New and 
the Old World. 

One is a genus of the tropics and the other is a genus of 
south temperate latitudes ; and both have occupied the Pacific 
islands ; but Coprosma naturally finds its most appropriate station 
on the cool uplands of Hawaii and Tahiti. We may ask, indeed, 
whether the great contrast in the fecundity of the two genera, 
dispersed as they are in the same fashion by the agency of fru- 
givorous birds, is to be connected with questions of relative antiquity 
or with geographical position. It would certainly have been a 
more difficult task in the past, other things being similar, for a New 
Zealand genus to stock the temperate regions with its species than 
for a tropical American genus to overrun the warmer regions of 
the globe. However that may be, the age of dispersal of both 
genera is largely over now. 

A vast genus like Psychotria, that is not sharply defined from 
other genera, presents difficulties to the systematic botanist which 
are reflected in a complex synonymy ; but there are certain broad 
facts which the student of dispersal can gather for himself without 
much difficulty. When we look at its distribution in the islands 
of the open Pacific, we find that the genus attains its greatest 
development in the Western Pacific, there being from thirty to 
forty species known from Fiji and quite a dozen from Samoa, and 
that it shades away as we proceed eastward and northward, some 
six species being recorded from Tahiti and the Marquesas, two 
from Hawaii, and one from Juan Fernandez near the South 
American mainland. The arrangement of the species shows fairly 
conclusively that the genus Psychotria, as it is found in the Pacific, 
has, like most of the other plants of this era of non-endemic genera, 
been derived from the Asiatic side of the ocean. (The absence of 
species of this genus from Mr. Cheeseman's Rarotongan collections 
seems strange. It is represented by some species in Tonga, and it 
is extremely probable that it will be subsequently found also in the 
Rarotongan group.) 

That the age of dispersal of the genus Psychotria over the Pacific 
islands has almost passed away is evident from the circumstance that 



3 i6 A NATURALIST IN THE PACIFIC CHAP. 

of the half-hundred species known from these groups, all but some 
four or five are confined to particular groups. There is one species, 
P. insularum, that ranges over the South Pacific from Fiji to the 
Tahitian region ; and there are two or three others that keep up a 
connection between the adjacent groups of Fiji, Samoa, and Tonga, 
the last having no peculiar species ; but, apart from these indica- 
tions, isolating influences generally prevail. The two Hawaiian 
species are both endemic and are only recorded from the island of 
Kauai, so that in that archipelago there has not even been inter- 
island dispersal of the genus. For Fiji it would seem from the 
Index Kewensis and other authorities that at least two-thirds of 
the species are confined to the group. Of the dozen Samoan 
species only two or three are known outside the islands. Four out 
of the five Tahitian species are peculiar, and the only Marquesan 
species named by Drake del Castello is endemic. Even the solitary 
species of Juan Fernandez is endemic, there attaining the dimen- 
sions of a fair-sized tree. It forms the subject of an illustration in 
Schimper's Plant- Geography, page 491. 

Speaking generally, birds may be said to have almost ceased 
dispersing this genus over the Pacific. This is not because birds 
have ceased to be partial to the fruits, but because the frugivorous 
birds that used to range over the Pacific archipelagoes now restrict 
their wanderings to the limits of a single group. If we find 
occasionally in other parts of the world, as in the occurrence of a 
Florida species of Psychotria in the Bermudas, some evidence of a 
dispersal still in operation, this is nothing more than we observe 
in the case of a few of the Polynesian species now. The connection 
between birds and plants in the Pacific is discussed in Chapter 
XXX III. In this ocean the dispersal of the genus is now practically 
dead, and Psychotria presents no exception to that general 
tendency towards isolation and differentiation exhibited by most 
genera of the tropical Pacific as the result of failure of the means 
of dispersal. 



CYRTANDRA (Gesneracese). 

This remarkable genus of shrubs, which forms the subject of an 
important memoir by Mr. C. B. Clarke (De Cand. Mon. Phan. v. 
1883-87), offers, as Mr. Hemsley remarks, an example of a Malayan 
genus extending to Polynesia and there developing numerous 
species. Of some 180 known species, about 80 or nearly half are 
confined to Polynesia, the rest being mainly Malayan. Of the 



xxv CYRTANDRA 317 

Polynesian species about thirty are Hawaiian, twenty Fijian, fifteen 
Samoan, and twelve Tahitian ; whilst solitary species are restricted 
to Tonga and Rarotonga respectively. 

The most significant feature in the distribution of this genus in 
Polynesia is not only, as is pointed out by Mr. Clarke, that every 
group has its peculiar species, but that very few species are found 
in more than one group, and that even in the same archipelago 
each island has its own species. Thus, of the thirty Hawaiian 
species, all of which are peculiar to the group, only two or three, 
according to Hillebrand, are at all generally distributed over the 
islands, whilst four-fifths have not yet been found to be common to 
more than one island. So again, all the species found in the 
Tahitian Group proper are peculiar, with the exception of one ex- 
tending to the neighbouring Paumotu Islands ; and even Rarotonga 
has its own species. In the region comprising Fiji, Tonga, and 
Samoa the same rule prevails, only two or three species connecting 
the three groups together. There thus seems to be not only a 
complete suspension of the dispersal agencies between the various 
archipelagoes, but also often between the several islands of a group. 
This is particularly to be remarked with the relatively contiguous 
groups of Fiji, Samoa, and Tonga, since with most other genera a 
number of species are common to all three archipelagoes. " The 
polymorphism of the Hawaiian Cyrtandras," says Hillebrand, " is 
extraordinary : no single form extends over the whole group, and 
not many are common to more than one island. The variations 
affect nearly every part of the plant, and branch out and intercross 
each other to such an extent that it is next to impossible to define 
exact limits of species." Genera, however, run riot in other groups 
of the Pacific besides Hawaii, and Reinecke uses much the same 
language with reference to Elatostema, an Urticaceous genus in 
Samoa, attributing the wealth of forms to the sensitiveness of the 
plants to the varying conditions of station (see Chapter XXVII). 

The behaviour of Cyrtandra in the Pacific is rather startling to 
the student of plant-dispersal when he reflects on the suitability or 
the berries for dispersing the plant through the agency of birds. 
That the vegetation of oceanic islands should be of an endemic 
character is a fact, remarks Mr. Clarke, that is illustrated by many 
other orders besides the Gesneraceae. But the point we have to 
remember is that not only does the genus Cyrtandra display the 
same prolific character in the large continental islands of Malaya, 
such as Java, Sumatra, and Borneo, each of which possesses at least 
a couple of dozen species, but that this seems to be a feature of the 



3i8 A NATURALIST IN THE PACIFIC CHAP. 

tribe Cyrtandreae and of the whole order. The genera, as observed 
by Mr. Clarke, are very continuous in their areas of distribution, and 
in the tribe Cyrtandreae there are very few species that extend to 
more than one region, whether on the mainland or in an oceanic 
archipelago. In the Himalayas, he says, closely allied species of 
Didymocarpus are confined to single districts, although there 
appears no reason either in soil or climate why they should not 
spread to the adjacent valleys. 

There is therefore, we may infer, nothing peculiarly character- 
istic of insular floras in this prolific display of the genus Cyrtandra 
in the Pacific, except that it is rather more pronounced in an 
oceanic group than in a continent. The same general cause is 
working alike in an island in mid-ocean, in a large continental 
island bordering the mainland, and on the mainland itself. With 
the Pacific Cyrtandras as with the British species of Rubus the 
variability may be so great that the ordinary agencies of dispersal 
fail to keep it in check ; and when, as in the Pacific islands, the 
suspension of the activity of these agencies is complete, the 
formative energy of the species knows no bounds other than 
the determining limits of station. Our lesson from the Pacific 
Cyrtandras is therefore this. The isolation of the oceanic 
archipelagoes may not explain the endemic character of the flora, 
but only the extreme degree to which the endemism is carried. 
When a genus is in its prime, it can defy all the limiting condi- 
tions imposed by similarity of station and by free and unchecked 
means of dispersal, the essential marks of a species or a genus 
having probably in their development little or no connection with 
environment. 

The Cyrtandras of the Pacific Islands are most frequent where 
vegetation is rank, as in moist woods, in humid valleys, and in 
shady ravines and gorges ; but they may also occur in more 
exposed and drier stations. They often grow gregariously, and 
Schimper says the same of them in the Java forests (Plant- 
Geography, pp. 291, 297). 

The fruit of the genus is described by Clarke as a fleshy or a 
coriaceous berry. Almost everywhere in the Pacific groups the 
berry is white and fleshy ; but it is noteworthy that out of the nine 
Tahitian species where the fruit is particularised by Drake del 
Castello, in two cases it is designated a capsule and in seven a 
berry. It is in this connection worth remarking that in Malaya 
other genera of the tribe often have capsular or dry and coriaceous 
berries. The conspicuous white berries of the Pacific species would 



xxv FREYCINETIA 319 

readily attract birds, and their minute roughened seeds scattered 
through the pulp might readily adhere to their plumage or even be 
ejected unharmed in their droppings. As respecting the capacity for 
dispersal, the Pacific Cyrtandras come near the Hawaiian endemic 
genera of Lobeliaceae with baccate fruits and minute seeds. Speak- 
ing of Malayan genera of the tribe Cyrtandreae, Mr. Ridley says 
that their dry, dull-coloured, and inconspicuous corky fruits are 
often devoured by animals. The seeds, on account of their 
roughened surface, adhere to rocks and other surfaces and readily 
germinate. 

FREYCINETIA (Pandanaceae). 

If there is any genus of tropical plants to which the student of 
distribution can look for guidance in the region of the Pacific, it is 
to Freycinetia as dealt with by Dr. Warburg in his monograph on 
the order (Engler's Pflanzenreich, iv. 9, 1900). Its characters and 
its distribution are well defined ; and here, if anywhere, we might 
be able to work out the history of a genus. In the words of the 
German botanist, it stands quite apart from Pandanus and Sara- 
ranga, the two other genera of the order. When Hillebrand was 
preparing his work on the Hawaiian flora, more than a quarter of a 
century ago, only about thirty species were known. Warburg's 
list, excluding doubtful forms, comprises sixty species, and even 
this number the author surmises will be doubled in future years. 
The later investigators, however, have not materially extended the 
range of the genus ; and the statement of the botanists of a 
generation ago, that it extends from Ceylon through Malaya 
and Australia to New Zealand, and is found on almost every 
elevated island of the Pacific, can only be supplemented by extend- 
ing its area to the Asiatic mainland in Burma where a wide-ranging 
Malayan species exists. 

It is, however, remarkable that no endemic species can be with 
certainty accredited to the mainland of Asia either in Burma or in 
the Malay peninsula where the genus also occurs. The Malayan 
region from Java to the Philippines possesses quite three-fifths of 
the species, and it is singular how few wide-ranging species there 
are. The Philippine Islands, Borneo, Celebes, Sumatra, Java, New 
Guinea, &c., have all their own species, the only wide-ranging plant 
being Freycinetia angustifolia, which occupies the region from 
Burma to Java and Borneo. So also in the Pacific, there is no 
widely distributed species, every group possessing its own plant or 
plants, and there does not appear to be any Freycinetia that is 



320 A NATURALIST IN THE PACIFIC , CHAP. 

common to two groups. Thus, Hawaii and Tahiti each have their 
own species. Rarotonga, according to Cheeseman, owns a peculiar 
but not yet fully described form. Samoa has two and Tonga has 
one species. Westward from Tonga and Samoa the numbers 
of species increase, Fiji possessing five and New Caledonia four, 
Australia and New Zealand each claim two species as their own. 

Dr. Warburg, who has studied the genus in its home, remarks 
on page 43 that none of the species possess any means of dispersal 
enabling them to cross an ocean ; and he connects with this 
the fact that the genus is only found (to use his own words) 
on islands like those of Samoa, Tahiti, and Hawaii, that possess a 
" palaeobiotic " nucleus (falaobiotischen Kern), and not on islands 
like the Bonin Islands of new formation (auf Neubildungen). 
This attitude towards the problem of plant-distribution in the 
Pacific is backed by a great experience ; but it is one, of course, that 
is directly opposed to the line of argument followed in these pages ; 
and it is needless to say that it is not encouraging to the student 
of plant-dispersal. Yet one could hardly look upon the islands of 
the Tongan Group with their representative of the endemic 
Freycinetias as of more ancient origin than the Bonin Islands that 
have none ; and plants that find their homes on the peaks and in 
the forests of mountainous islands would rarely find a suitable 
station on the low coral islands of the Pacific. It is, however, 
noteworthy that Professor Schimper is inclined to include a species 
of Freycinetia as amongst the strand-flora of the coral islands of 
the Java Sea (Ind. Mai. Strand-flora, p. 1 34). With regard to the 
question of the means of dispersal of Freycinetias, it will at once be 
shown that these plants possess many opportunities for dispersal 
by birds. 

Though in our own time dispersal by birds between the various 
Pacific archipelagoes is often largely suspended, the inter-island 
dispersal in each group is usually active through the agency of 
birds, now like the plants they distribute confined to each group. 
Thus with Freycinetia we find that, notwithstanding that each 
Pacific group is, as regards this genus, isolated from the others, the 
separate islands, as in the case of those of Hawaii, may possess 
a common species dispersed over the area. The ripe fruit, which 
consists of a number of berries in a head or spike, is juicy and 
pulpy, and contains in each berry a large number of minute oblong 
or fusiform seeds, usually one or two millimetres long and possess- 
ing thick toughish tests. Birds, indeed, are fond of pecking at the 
ripe fruit-heads in Hawaii. Thus we learn from the Aves Hawaiienses 



xxv FREYCINETIA 321 

of Wilson and Evans that a Grosbeak (Psittacirostra) and the 
Hawaiian Crow (Corvus tropicus) feed principally on ripe Frey- 
cinetia fruits, the seeds having been often found by Mr. Wilson in 
the stomach of the former bird. No doubt these birds distribute 
the seeds over the islands of the group. Mr. Perkins tells me that 
the Grosbeak is found unmodified all over the group, and that it 
no doubt frequently gets carried nolens volens from one island 
to another. In his memoir on the birds in the Fauna Hawaiiensis, 
he remarks that the essential food of the " Ou," the native name of 
this bird, is the fruiting inflorescence of Freycinetias. The " Oo " 
(Acrulocercus) and the Hawaiian Crow above mentioned, as he also 
observes, feed on these ripe red fruits. Like Mr. Wilson, he some- 
times found the Crow absolutely filled with this food to the 
exclusion of all others (see Chapter XXXIII). Facts of a similar 
kind came under my notice whilst in these islands. Thus on 
one occasion I observed, on a leaf below a fruit-head that had 
been partly eaten by a bird, a pellet half an inch long composed 
entirely of Freycinetia seeds well soaked with the gastric juices 
and apparently only recently disgorged. Sir W. Buller refers 
to different New Zealand birds, as the Banded Rail (Rallus 
philippensis), the Kaka Parrot (Nestor meridionalis), and the 
" Tui " (Prosthemadera), that live on the " sugary flowering 
spadices" of Freycinetia Banksii. One can legitimately suppose 
that they also attack the juicy berries. It is singular that as 
we learn from Dr. Warburg (p. 17), Flying-Foxes (Pteropidae) feed 
on the flowers and top-leaves of many species of Freycinetia, and 
he considers that they would aid in fertilisation by carrying about 
the pollen in the hair of the head. Here again it would seem to 
us highly probable that whilst brushing past a ripe fruit-head these 
bats might readily carry away in their fur some of the minute 
seeds, which in the fresh berry are " sticky " or adhesive. 

Just as it was possible in the case of Coprosma in the South 
Pacific (see page 296) to connect its distribution with the range of 
the Purple Water-Hens (Porphyrio), so it may perhaps be legiti- 
mate to associate the range of Freycinetia over Polynesia with the 
distribution of the Honey-Eaters (Meliphagidae) in the Pacific, 
a family sometimes possessing peculiar genera as in New Zealand 
and Hawaii, and one in which the species have usually a very 
confined range, being sometimes limited to a single island 
(Newton in Encycl. Brit. xii. 139). To this family belongs the 
New Zealand " Tui " above mentioned ; and it may be remarked 
that these birds as a rule feed on soft fruits, such as figs, and 

Y 



322 A NATURALIST IN THE PACIFIC CHAP. 

bananas. It is to Acrulocercus, one of the Hawaiian genera of the 
Meliphagidae, that Mr. Perkins refers me, on my asking him to 
name some of the fruit-eaters in that group. 

These climbing shrubs, as Dr. Warburg observes, mostly fre- 
quent the tropical forests up to 4,000 feet and over. Though their 
most familiar habit is as tree-climbers in the forests, in localities 
where there are no trees they adopt a trailing habit and cover 
mountain peaks and ridges with a dense growth to the exclusion of 
almost all other plants. Many a peak in the Pacific islands would 
be inaccessible if it were not for the dense growth of these plants 
on their precipitous sides. It was owing to the friendly aid of 
a tangled mass of Freycinetia stems that Lieutenant Heming and 
myself were able to clamber to the summit of Fauro Island 
(1,900 feet) in the Solomon Group, where I discovered a tree that 
under the name of Sararanga forms the type of the third genus of 
the Pandanaceae. 

Whilst describing their station, it will be of interest to also 
record the altitudes at which these plants have been observed in 
the tropical Pacific. Since they can be independent of trees and 
are as much at home on treeless rocky peaks and mountain crests, 
the upper limit would usually be determined by climatic conditions, 
abundance of rain and great humidity being the chief requisites ; 
but, as will be seen below this limit, does not seem to be reached in 
the tropical islands of the South Pacific except perhaps in Tahiti. 
In the Fijis the Freycinetias ascend to the highest mountain peaks. 
Thus, three of the species discovered here by Seemann were found 
at elevations of about 4,000 feet on Voma Peak in Viti Levu and 
in the highlands of Taviuni. In Vanua Levu, as I found, they 
cover the highest peaks 3,500 feet above the sea. They are espe- 
cially abundant on the lofty mountain ridges, and clothe the higher 
slopes of the Mbatini Ridge which terminates in the highest peak 
of the island. In no locality did I find them growing in such 
densely tangled masses as on the long ridge-like crest that forms 
the upper part of Mount Freeland, 2,740 feet above the sea. For 
more than an hour in order to reach the summit I had to clamber 
along the crest of a ridge covered with a dense growth several feet 
deep of these trailing plants, without touching the ground beneath. 

In Samoa, as we learn from Reinecke, Freycinetias are common 
on the mountain ridges, climbing the trees and forming also a 
dense undergrowth covering the ground and concealing the rocks. 
They occur at all levels from 1,000 feet above the sea up to the 
highest region of Savaii, rather over 5,000 feet in elevation. In 



xxv FREYCINETIA 323 

Rarotonga, according to Mr. Cheeseman, the Freycinetias are very 
abundant on the mountains, which reach a height of 2,200 feet, the 
plants scrambling up the trunks of trees or over rocks and fre- 
quently rendering the forest almost impenetrable. In Tahiti, 
Nadeaud tells us, the Freycinetias often cover in an inextricable 
network the sides of the valleys at elevations of 2,000 to 3,300 feet, 
extending in their vertical range from the lower levels of the island 
to the highest inaccessible peaks which attain a maximum height 
of about 7,300 feet. 

These plants in the Hawaiian group are common in the lower 
woods as Hillebrand informs us, that is to say, at elevations of 
2,000 or 3,000 feet. During my descent from Mauna Kea through 
the Hamakua forests on the north-east side I observed that the 
Freycinetias commenced at an altitude of 3,900 feet, and that they 
attained their greatest development between 3,200 and 2,000 feet. 
These plants ascended quite a thousand feet higher on these 
mountain slopes than the Bird's Nest Fern (Asplenium Nidus), 
which reached an altitude of 2,800 feet. In the forests on the west 
side of Mauna Loa they were abundant at altitudes of 3,500 to 
4,000 feet and were not noticed above 4,500 feet. On the slopes of 
Mount Eeka in West Maui they abounded between 3,500 and 4,400 
feet. In those localities where the forest descends to the sea, Frey- 
cinetias occur at the coast, and on Oahu they are often found at 
elevations under a thousand feet. 

I have but few data showing, the altitude obtained by Freycine- 
tias in other regions, as, for instance, in their most southerly habitat in 
New Zealand, where they give a tropical luxuriance to the forests, 
or in their chief home in Malaya. From Schimper's observations 
{Plant-Geography, p. 293) it would seem that they thrive in the 
Gedeh forest of Java at elevations of about 5,000 feet. Except for 
the lower levels, Warburg makes but few references to this subject 
in dealing with the species. It appears to me that some very 
interesting results might be obtained by comparing the vertical 
range of this genus in different regions, as, for instance, in New 
Zealand and in Borneo or in Java. We might get indications that 
since the age of Freycinetia began the climate in tropical latitudes 
has been getting warmer, and that the erstwhile plants of the lower 
levels are now as a result climbing the mountain slopes. The 
student of distribution may find here a genus that has been 
" cornered " not only in space and time, but as regards its condi- 
tions of existence. Since it is obvious that during a gradual in- 
crease of temperature it would ascend the mountains and during a 

Y 2 



324 A NATURALIST IN THE PACIFIC CHAP. 

lowering of temperature it would descend to the plains, it follows 
that in the mountains of an oceanic island it might be driven into 
the sea or await extinction on a mountain-top. In the tropics also 
there would be no escape during a gradual increase of temperature. 
Here again it would make its last stand on the strand, and, forced 
to choose between Death and Adaptation, the genus might select 
the latter alternative and present us with a startling new form. In 
this sense Freycinetia seems to offer itself as " fair game " for the 
speculative botanist, and at all events he will be able to interro- 
gate it as to the connection between its existing range of altitude 
and the climatic conditions of the earlier phases of its history. 

The Freycinetias bear the same name over Polynesia, " ie-ie " 
in Hawaii, " ie " and " ie-ie " in Tahiti and Samoa, which appear 
in their full form in the Rarotongan and Maori " kie-kie." The 
secret of the wide distribution of the name lies in the circumstance 
that this is a mat-word over much of Polynesia, as in Fiji, Tonga, 
Samoa, the Gilbert group, Tahiti, &c., Freycinetia leaves being 
often employed for making mats, as in Samoa and New Zealand. 
The same word is applied in some groups to small species of 
Pandanus that were also used in mat-making. Thus in Fiji 
" kie-kie "was not only the name for a mat-dress, but also of Pandanus 
caricosus that supplied the material. In the home of the Poly- 
nesians in Malaya and its vicinity the same word for mat and 
Pandanus occur. Thus, " gerekere " in the Motu dialect of New 
Guinea and "keker" or " kekel " in Amboyna are the names of 
small species of Pandanus employed in mat-manufacture ; whilst 
" kihu " and " kiel " in Celebes are the words for the mats them- 
selves. Therefore in one form or another the word, originally 
applied to the mats, but now often restricted to the plants from 
which the materials were derived, ranges over the great region 
extending from Malaya to New Zealand, Tahiti, and Hawaii, and, 
as I have shown in the table given in my paper on Polynesian 
Plant-Names (Journ. Victor. Inst., London, 1896), it may be traced 
even to Further India, as in Annam, and to North-East Australia. 
It thus covers the area to which the migrations of the Polynesians 
of the Pacific have been confined, and it covers also the area of the 
genus Freycinetia. There is something far more than mere analogy 
between man and plants in their occupation of the Pacific islands. 
The plants are Malayan and the Polynesians are from Malaya also, 
whilst in both man and plants we experience the same difficulty in 
explaining their dispersal over the ocean. Divesting his mind of 
all previous conceptions, the ethnologist might profitably study 



xxv SAPINDUS AND PHYLLANTHUS 325 

de novo the dispersion of man in the Pacific from the standpoint of 
plant-dispersal (see Chapter XXVIII). 



SAPINDUS AND PHYLLANTHUS. 

Brief reference can alone be made to these two genera. Fore- 
most comes Sapindus, which is represented by two endemic species, 
one in Hawaii and one in Fiji, and by another species, found in 
Tahiti, the Marquesas, and Easter Island, which is identified by 
some botanists with the well-known American " soap-tree," S. 
saponaria. There are several difficulties connected with the 
presence of this genus of the Old and New World in the Pacific. 
Not the least of them is connected with the transport of the large 
seeds of this genus, an inch in size, to the isolated Hawaiian Group, 
where it is represented by a solitary endemic species in the island 
of Oahu. The fleshy mesocarp of the fruits might attract birds ; 
but it is not easy to perceive how birds could carry such large seeds 
over some 1,500 or 2,000 miles of ocean. Yet the same difficulty 
exists with a few other genera, such as Osmanthus and Sideroxylon, 
that are only represented in Hawaii by endemic species, genera 
which require the agency of birds to explain their occurrence 
unless we wish to postulate a continental connection for this group. 
(See under those genera in Chapter XXVII.) 

The large Euphorbiaceous genus Phyllanthus, spread uni- 
versally over the tropics and containing some 500 known species, 
clearly indicates by its distribution in the Pacific islands that 
genera with dry fruits, such as are typical of the order, are as 
widely distributed and just as much at home in these islands as 
the genera with fleshy fruits, such as Psychotria and Cyrtandra. 
The small trees and shrubs of Phyllanthus are common in dry, 
open, partially wooded districts near the sea-border. The genus 
attains its greatest development in this ocean in New Caledonia 
and Fiji ; and since the number of species diminishes the further we 
penetrate the Pacific, it can be scarcely doubted that the genus has 
entered this ocean from the west. In Fiji there are at least 20 
species, of which probably half are not recorded from elsewhere. 
In Samoa there are seemingly but few peculiar species. In 
Hawaii there is only one indigenous species, and that is endemic. 
The genus, however, has developed a lesser centre of distribution 
in East Polynesia, there being about a dozen species known from 
Tahiti and the Marquesas, of which half are peculiar to one 
or other of those groups. From experiments made by me in Fiji 



326 A NATURALIST IN THE PACIFIC CHAP. 

on the fruits and seeds of two species it was evident that they 
possessed little or no capacity for dispersal by the currents. We 
look, therefore, to the birds, and in this connection it is of interest 
to note that this genus is included amongst those known to be 
dispersed by birds in the Pacific, some of the fruits having been 
found in the crops of fruit-pigeons shot by Prof. Moseley in the 
Admiralty Islands (JBot. Ckall. Exped^ Introd. 46 ; iv. 308). 

PRITCHARDIA (Palmaceae). 

This genus of Fan Palms supplies an instructive lesson for the 
student of plant-distribution, more especially with reference to the 
loss of the endemic reputation of a genus. Regarded by the 
earlier botanists who visited the Pacific as identical with the 
familiar Asiatic Talipot Palm (Corypha umbraculifera), the Fan 
Palms of this region, as represented in Fiji and Hawaii, were 
subsequently placed by Seemann and Wendland in a new genus 
restricted to Polynesia and named after a former British Consul in 
Fiji. Since that time it has lost its reputation as a peculiarly 
Pacific genus, since a species (Pritchardia filifera) has been found 
lingering in a few valleys in Arizona, where it enjoys the distinc- 
tion of being the most northerly in station of all the world's palms 
(Linden in Illustr. Hort. vol. 24, 1876-77). It would thus appear 
that the Pacific islands have derived this genus of palms from the 
western part of North America, but the whole question is beset 
with many difficulties, and not the least is that connected with the 
confusion that seems to reign in several cases as regards the 
allocation and identity of the species. 

Six species are named in the Index Kewensis, viz. : Pritchardia 
macrocarpa, restricted to Hawaii ; P. martii and P. gaudichaudii, of 
the Pacific islands ; P. pacifica, assigned to Fiji ; P. vuylstekeana, 
from the Paumotus ; and P. filifera, from the west side of North 
America. Though it is sometimes difficult to reconcile this 
account of the distribution of the genus in the Pacific with views 
held by other botanists, it offers the safest basis for the future 
investigation of the subject. It would be, however, necessary 
to remember that Pritchardia gaudichaudii and P. martii are 
regarded by Hillebrand as peculiar to the Hawaiian Islands, 
and that the exact locality of the Paumotu species is not very 
definitely settled, if it depends on the remarks made on this species 
in the Gardeners' Chronicle for 1883. No mention is indeed made 
by Drake del Castillo of any Tahitian or Paumotuan species. 



xxv PRITCHARDIA 327 

Whilst in Hawaii and Fiji I was much interested in these 
palms, and the following remarks are merely intended to be a 
contribution to the subject. According to Seemann, Hemsley, 
Drake del Castillo, and Burkill, Pritchardia pacifica, which often 
attains a height of thirty to thirty-five feet, occurs in Fiji, Tonga, 
Samoa, and the Marquesas, but it does not exist in Tahiti, and 
Cheeseman does not include it in the Rarotongan flora. Except 
in the Tonga Group, where, according to Lister as quoted by 
Hemsley, the palms form conspicuous objects along the weather 
shore of the island of Eua, this species is rarely found in the wild 
state in the South Pacific. This especially applies to Fiji, as 
Mr. Home also observes ; and at most one is accustomed to see (to 
employ the words of Dr. Seemann) one or two trees outside 
a village which are reserved, as in many parts of Polynesia, for 
the use of the chiefs who employ the leaves for fans and for other 
purposes. But even this reason for preserving the palms scarcely 
now exists in Fiji, and at the time of my sojourn in Vanua Levu 
(1897-99) the trees were rare enough to be regarded as curiosities. 
In the Marquesas, according to Bennett (quoted by Seemann), they 
grow in groves in the valleys of the interior. Dr. Reinecke does 
not even include the species in the Samoan flora, but mentions it 
with the Date-Palm (Phcenix dactylifera) as if it were recently 
introduced. It was, however, found in that group by the United 
States Exploring Expedition about 1840, and this is evidently the 
palm referred to by Captain Cook as existing at his time in 
the Tongan Group. 

The Hawaiian species of the palm appear to be three in 
number, Pritchardia gaudichaudii and P. martii, both regarded by 
Hillebrand as confined to the group, and P. macrocarpa of Linden, 
also endemic (Ilhistr. Hort. vol. 26). The two first-named species 
are evidently on the road to extinction in the wild state, and often 
find their last refuge on rocky, almost inaccessible, inland cliffs. 
Pritchardia gaudichaudii, about twenty feet in height, is found in 
the wild state, as we learn from Hillebrand, on the islands of 
Molokai and Hawaii. It was at one time frequently met with near 
native dwellings ; but during my sojourn in 1896-97 on the last- 
named island it was not at all frequent, and as a rule only came 
under my notice occasionally in clumps of three or four trees 
on the Kona and Puna coasts, as near Kiholo, Milolii, and 
Kalapana. However, it was more frequent in the Waimanu 
district of Kohala in the same island. Here I noticed it growing 
in clumps in precipitous rocky situations at elevations ranging 



328 A NATURALIST IN THE PACIFIC CHAP. 

from 1,200 to 2,000 feet. The other palm mentioned by Hille- 
brand, P. martii, is only five or six feet high, and is confined mostly 
to Oahu and Molokai. 

The agency of man in introducing these interesting Fan-Palms 
into the Hawaiian Islands seems out of the question, since they are 
home productions in a specific sense and are doubtless ancient 
components of the flora ; and, of course, grave objections exist on 
ethnological grounds, if this genus had originally its home in 
America. With reference, however, to Pritchardia pacifica of the 
South Pacific, it is not unlikely that man has aided in the distribu- 
tion of a palm mainly preserved by planting in and about the 
villages and set apart from time immemorial for the use of the 
chiefs. 

In this connection the aboriginal names are of some import- 
ance and may be very briefly here referred to. The Fijian " Viu," 
the " Piu " of Samoa, Tonga, and Futuna, and the Tongan " Biu " 
are forms of the same name applied to this palm all over West 
Polynesia ; and I have shown in my paper on Polynesian Plant- 
Names that in the form of " Firo " in the Solomon Islands (Bougain- 
ville Straits) and of " Wiru " in Sundanese, one of the Malayan 
languages, the same name is given to another genus of Fan Palms, 
namely, Licuala. But since these West Polynesian names do 
not always conform with the laws of consonantal interchange 
in this region, they cannot all be considered as indigenous in 
the languages concerned. If, for instance, " Viu " is an indigenous 
Fijian name, as no doubt it is, since it follows the phonetic laws 
affecting the Malayan and Fijian languages, "Piu" must be 
a foreign word in Samoa and Tonga, and " Biu " must be another 
introduced Tongan name. . . . The Fijians have in " Sakiki " 
(contracted into " Saii " in the Somosomo dialect) another name for 
this palm. This is probably derived from " Kiekie," a mat-word in 
different forms in various Polynesian groups, and applied in many 
islands to the plants that supply the materials for mat-making, 
such as Pandanus and Freycinetia. 

The Hawaiian generic name of " Loulu " for these palms appears 
to be quite local ; but it may possibly have a common origin with 
" Roro," one of the Fijian names of Cycas circinalis. It is pointed 
'out by Hillebrand that the Hawaiian name of the edible kernels of 
these palms, " Hawane " or " Wahane," occurs in the Marquesas as 
" Vahana " applied to the palm, a comparison that is on linguistic 
grounds quite legitimate. " Vaake " is another Marquesan name, 
which recalls " Vakoa," the Malagasy word for Pandanus. 



xxv PRITCHARDIA 329 

When we compare the variety of the names of the Pritchardia 
fan-palms in the Pacific Islands with the prevailing uniformity of 
the names of cultivated plants transported by the aborigines in 
their migrations from Malaya, such as the taro, the yam, the sugar- 
cane, the coco-nut, and the Malay-apple, we perceive that the 
testimony of the names points to the same conclusion as the 
botanical evidence, namely, that the ancestors of the Hawaiians 
found these palms in the group at the time of its occupation. In 
the South Pacific much uncertainty prevails. The ancestors of the 
West Polynesian peoples evidently brought the word for a fan- 
palm from their Malayan home ; but it is doubtful if they found 
Pritchardia already established in all the islands ; and the apparent 
home of the genus in America prevents us from attributing to a 
palm, that is by some botanists regarded as confined to the Western 
Pacific, a home in the neighbouring regions to the west. There is 
thus a lack of agreement between the botanical and ethnological 
indications as regards the original American origin of Pritchardia 
in the South Pacific. 

There remain then the agencies of the currents and of birds. 
A singular feature in the distribution of the Hawaiian species, 
Pritchardia gaudichaudii, at once affords a clue as concerning the 
dispersal in the North Pacific. Dr. Hillebrand remarks that this 
palm covers part of Bird Island, a small volcanic rock forming an 
outlier of the Hawaiian group about 400 miles north-east of Kauai. 
Here the agency of birds is suggested, since it is scarcely likely, 
though, as shown below, not impossible, that stranded fruits of the 
palm could have established themselves in this fashion. Mr. 
Perkins has an interesting note on the food of Ciridops anna, an 
Hawaiian bird, now nearly extinct, that feeds principally on the 
blossoms and unripe fruits of the Loulu palms, probably of this 
species. The drupes when fresh have a somewhat fleshy mesocarp 
and are about T 9 F of an inch (22 mm.) across, and their crustaceous 
inner shell would undoubtedly fit the seeds for dispersal by frugiv- 
orous birds like pigeons. The fruits of the other two Hawaiian 
species are considerably larger, that of P. macrocarpa being, accord- 
ing to Linden, of the size of a nut of Juglans regia, that is, about 
li inch or 29 mm., whilst that of P. martii, as we learn from Hille- 
brand, is from i to 2 inches or 37 to 50 mm. Allowing for the 
variation in size of the fruits within the limits of the genus, there 
need be no more difficulty in assuming that the original species 
had fruits that could have been brought by birds, than in holding 
that the fruits of Elaeocarpus have been carried to Hawaii in the 



33 A NATURALIST IN THE PACIFIC CHAP. 

same fashion. The drupes of Pritchardia pacifica are barely half 
an inch in diameter. They are fitted by reason of their hard 
crustaceous endocarp for dispersal by fruit-pigeons ; and I may 
here add that these birds are known to distribute the fruits of 
other palms, such as Kentia and Areca, in the islands of the 
South Pacific (Bot. ChalL Exped. iv. 308, 312). 

Both in Hawaii and in Fiji I experimented on the capacity of 
Pritchardia drupes for dispersal by the currents. Those of the 
Hawaiian species, P. gaudichaudii, have when well dried a light 
buoyant rather fibrous mesocarp which enables them to float in the 
case of a good proportion of the fruits for at least five weeks. I 
had no opportunity of testing the buoyancy of the fruits of P. 
martii, another Hawaiian species ; but, judging from the existence 
in the coats of a fibrous layer as described by Hillebrand, they 
ought to display some floating power. The fruits of P. pacifica,. 
the South Pacific species, lack the light buoyant covering of the 
Hawaiian species above referred to, and display little or no floating 
power even after drying for weeks. Looking at the results of these 
experiments, it would seem that it is not impossible that Hawaii 
received the genus through the agency of the currents ; but it 
seems scarcely probable, since it could only have been derived 
from America, and the American species grows in the interior of 
the continent and not near the sea-border. The possibility of 
course exists ; but I am inclined to attribute the presence of 
Pritchardia in Hawaii to bird-agency. 

My position from the standpoint of dispersal with regard to 
Pritchardia in the Pacific is this. The Hawaiian species I would 
consider as American in origin. The Marquesan species, unless 
recently described, still awaits detailed investigation. The West 
Polynesian species of Fiji and Tonga, according to the principles of 
distribution prevailing in the South Pacific, ought to hail from the 
west. 

Summary. 

(i) Whilst the earliest age characterised by the Coniferae was 
restricted to the Western Pacific, and whilst the following age of 
the Compositae and Lobeliaceae, mainly American in their affinities, 
was concerned with the regions of Hawaii and Tahiti, we have now 
to discuss the Malayan era during which the bulk of the plants 
were derived from the nearest tropical regions of the Old World. 
Here we have to deal with the low-level flora of Hawaii, that is to 
say, with the plants of the levels below 4,000 or 5,000 feet, and with 



xxv SUMMARY OF CHAPTER 331 

almost the entire floras of the areas of Fiji-Samoa and of East 
Polynesia. The whole of the tropical Pacific is here concerned, 
and not a portion of it, as in the two preceding eras ; and in our 
comparison we shall see that there are two, and not as heretofore 
three, regions to be regarded the Hawaiian in the North Pacific, 
and the whole Polynesian area of the South Pacific extending from 
Fiji to Tahiti. 

(2) Here the frugivorous bird has been the principal agent in 
dispersing the plants, quite two-thirds of the genera possessing 
drupes or berries that would attract such birds. 

(3) The genera representative of the first part of this era are 
those which have only peculiar species in Hawaii, and are com- 
posed in the South Pacific either entirely of peculiar species or 
sometimes of a mixture of endemic and non-endemic species. It 
is an era of complete isolation in Hawaii and often of a partial 
connection between the groups of the southern region. Except to 
some extent in the South Pacific, the dispersing agencies are 
now no longer active between the groups. 

(4) Amongst the genera typical of this period are Pittosporum, 
Gardenia, Psychotria, Cyrtandra, and Freycinetia. 

(5) The two genera of the Rubiaceae, Psychotria and Coprosma 
(the last belonging to the mountain-flora), appear to be well suited 
for the investigation of the effect on distribution of the geographical 
position of the home of the genus, the first with 600 to 700 species 
distributed over the tropics of the Old and New Worlds, the second 
with some sixty species having its home in New Zealand. 

(6) From the Pacific Cyrtandras we derive the lessons that the 
display of great formative power in a genus may not be a peculiarity 
of an insular flora ; that the isolation of an oceanic archipelago does 
not necessarily induce " endemism," but merely intensifies it ; and 
that the production of new species within the limits of a genus like 
Cyrtandra may be nearly as active on the mainland as in an island 
in mid-ocean. 

(7) From the Freycinetias we learn that it may be possible to 
connect the distribution of a genus of plants with that of a genus or 
a family of birds. Just as in Chapter XXIV we endeavoured to 
connect Coprosma and Porphyrio (the Purple Water- Hens), so we 
here suggest a connection, in their range over the Pacific, between 
the Freycinetias and the Meliphagidae (the Honey-eaters), a con- 
nection that in the last case at least belongs to the past. 

(8) From the genus Phyllanthus we learn that genera with dry 
fruits may be as widely distributed and may display the same 



332 A NATURALIST IN THE PACIFIC CH. xxv 

formative power in the Pacific as those with fleshy fruits that would 
seem much more likely to be dispersed by birds. Here again we 
obtain an indirect indication that species-making in these islands is 
not altogether dependent on isolation. 

(9) In the case of the genus Sapindus we are apparently 
compelled to infer that its large seeds (in the present species an 
inch in size) have been transported by birds to Hawaii. Yet in 
point of size the difficulties here raised are no greater than those 
arising from the existence of such genera as Sideroxylon and 
Elaeocarpus in Hawaii, the fruits of which are known to attract 
frugivorous birds. 



CHAPTER XXVI 

THE MALAYAN ERA OF THE NON-ENDEMIC GENERA OF 
FLOWERING PLANTS (continued) 

THE AGE OF WIDE DISPERSAL OVER THE TROPICAL PACIFIC 

(continued) 

The widely dispersed genera that are as a rule not entirely represented by 
endemic species in any archipelago. Elaeocarpus. Dodonasa. Metro- 
sideros. Alyxia. Alphitonia. Pisonia. Wikstrcemia. 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. Boer- 
haavia. Polygonum. Pipturus. Dianella. Summary. 

A LATER period in the era of the general dispersal of Malayan 
plants over the Pacific is indicated by those genera that as a rule 
are never entirely represented by endemic species in any archi- 
pelago. Hawaii now comes into touch with the world outside, and 
all the groups possess some connecting link. But the beginning 
of the effect of the isolating influence is shown in the association in 
each principal archipelago of peculiar species with those that occur 
in other groups. 

We see here illustrated in all but the final stage that process by 
which a solitary widely-ranging species, alone representing its 
genus, becomes ultimately in each group the parent of a number of 
peculiar species. The polymorphous, or extremely variable, species 
plays in this period the all-important part. The earliest stage 
is exhibited by such genera as Alphitonia, Dodonaea, Metrosideros, 
Pisonia, and Wikstrcemia, that possess in the tropical Pacific 
a solitary widely-ranging species, varying independently in every 
group and giving rise to forms that, in their degree of differentia- 
tion, sometimes approach a specific value. Later stages are shown 



334 A NATURALIST IN THE PACIFIC CHAP. 

when the polymorphous species, having done its work of distri- 
buting the genus, settles down and " differentiates " in every group ; 
and this we see now illustrated in the genera Elseocarpus, Alyxia, 
Peperomia, and others. 

The bulk of the genera of this period, of which only a few can 
be mentioned here, hail from the tropics of the Old World through 
Malaya. Thus Alyxia, Elaeocarpus, Morinda, and Wikstrcemia 
are Malayan ; whilst genera like Eugenia, Peperomia, and Pisonia, 
that occur in the Old and New Worlds, can similarly be traced to 
the Asiatic side of the ocean by the distribution of their species. 
Others again have their home in New Zealand like Metrosideros, or 
in Australia, as with Dodonaea and Scaevola. None are exclusively 
American. Some of the genera, as Morinda and Scaevola, have 
littoral as well as inland species ; but, as shown in Chapter XIV, 
there is rarely anything to suggest a derivation of the inland from 
the coast species, both being, from the standpoint of dispersal, of 
independent origin. 

About half of the plants have fleshy or sappy fruits (drupes and 
berries) that would attract frugivorous birds, such as we find 
in Xylosma, Elaeocarpus, Eugenia, Scaevola, Wikstrcemia, &c., 
whilst the others have often dry capsular fruits, with minute seeds 
as in Metrosideros, or with larger seeds as in Dodonaea. Some of 
them, like Pisonia, have fruits that excrete a viscid material that 
causes them to adhere firmly to plumage. Birds both granivorous 
and frugivorous have been actively at work ; and there are few 
difficulties relating to dispersal connected with the genera, except 
with such as Gossypium and Elaeocarpus. 

I will adopt the method employed in the preceding chapter of 
discussing in detail from the standpoint of dispersal some of 
the genera that came most frequently under my notice, or in which 
I am greatly interested, and of dealing briefly with some of 
the rest. Those dealt with in other connections will not be 
treated. 

EL^OCARPUS (Tiliaceae). 

This is a genus of trees containing, according to the Index 
Kewensis, about 1 30 species, most of which are confined to tropical 
Asia, including Malaya ; but a fair number occur in the Pacific 
region, in Australia, New Zealand, and the islands of the tropical 
Pacific, and the genus is also found in Japan. It will thus be seen 
that Elaeocarpus is not only a continental but also a typical insular 
genus. It has reached not only some of the most isolated island- 



xxvi EL^OCARPUS 335 

groups of the Pacific, but it is to be found also in the smaller 
islands of the Indian Ocean, there being an endemic species in 
Mauritius. Amongst the Pacific Islands, a region with which 
we are more immediately concerned, it has been recorded from the 
Solomon Islands, New Caledonia, Fiji, Tonga, Samoa, Rarotonga, 
and Hawaii. It is strange that the genus is not accredited to 
Tahiti, but since it is represented in Rarotonga we may regard it as 
not altogether absent from East Polynesia. Reinecke does not 
include it amongst the Samoan plants, but Home, in a short 
list of plants collected in Upolu about 1878, mentions Elaeocarpus 
graeffei, a Fijian species ( Year in Fiji, p. 285). 

New Caledonia represents the principal centre of the genus 
in the tropical Pacific, thirteen species being accredited to it in the 
Index Kewensis. Seemann found six species in Fiji, a number that 
does not seem to have been added to by Home. Of these one is 
found in Tonga and Samoa, and of the rest perhaps most are 
peculiar ; but one of them is closely allied to a second peculiar 
Tongan species. Tonga possesses the two species just alluded to, 
whilst Rarotonga and Hawaii have each a peculiar species. 

From an interesting comparison made by Mr. Burkill of some 
of the Polynesian species, it would seem that Elaeocarpus, if not 
actually possessing a widely-spread polymorphous species in 
the tropical Pacific, presents us with the next stage in the differen- 
tiation of the species. Thus, he says in his paper on the flora 
of Vavau that an endemic Tongan species, E. tonganus, is allied to 
three different species E. graeffei from Fiji, E. floridanus from the 
Solomon Group, and E. glandulifer from Ceylon three species, he 
remarks, which are " so closely allied that it is possible to regard 
them as insular subspecies." It would thus appear that some of 
the species of the Western Pacific are almost in touch with Asiatic 
species. It would be of importance to determine whether some 
affinity can be detected between the species of this part of 
the Pacific and some of the widely-ranging species of Indo-Malaya, 
such as E. ganitrus and E. oblongus. Mr. Burkill goes on to say 
that the solitary Hawaiian and Rarotongan species are closely 
allied, an inference which is of interest as indicating the route 
by which Hawaii received its species. The genus, we may fairly 
infer, once possessed a widely-ranging polymorphous or very variable 
Asiatic species in the tropical Pacific ; and we see it now in the 
next stage of specific differentiation in various far-removed regions. 
In this connection Seemann significantly remarks that all the 
Fijian species are evidently very local in the group. 



336 A NATURALIST IN THE PACIFIC CHAP. 

It will be appropriate here to refer briefly to the station and 
mode of occurrence of the species. They occur most typically as 
forest-trees, often of considerable height. In New Zealand, accord- 
ing to Hochstetter, they form a feature in the temperate rain- 
forest ; and, as we learn from Kurz, they are similarly conspicuous 
in the tropical rain-forests of Pegu. To this seeming indifference 
to the varying thermal conditions of different latitudes we shall 
have subsequently to refer again. The tree of the Hawaiian 
Group, as Hillebrand tells us, is common in the forests of Oahu 
and Kauai, but is scarce in Maui and Hawaii, a singular distribu- 
tion that may be due to the inflorescence being " often monstrously 
deformed by oviposition of some dipterous insect." The Raro- 
tongan species, according to Cheeseman, is common throughout 
the island from the sea-level to the tops of the hills. In Vanua 
Levu I found that these trees preferred the crests of wooded 
mountain-ridges or the partially vegetated mountain peaks. They 
came under my notice in the forests of the island of Fauro, in the 
Solomon Group, associated with other large trees of the genera 
Canarium and Calophyllum. 

Much interest is attached to the mode of dispersal of this genus, 
since in some species the size of the drupes and of the included 
" stone " is so great that, judged by those species only, it might be 
deemed impossible to attribute the existence of the genus in 
isolated oceanic groups to the agency of frugivorous birds. We 
are, however, compelled to appeal to the bird, since, as my 
experiments in Fiji indicate, the genus has little or no capacity for 
dispersal by currents, the " stone " when containing a seed always 
sinking, whilst the entire fruit either sinks at once or floats heavily 
for a few days. 

The degree of fleshiness of the drupes of Elaeocarpus varies 
in different species, being sometimes slight and at other times 
pronounced, but, speaking generally, they would be expected to 
attract frugivorous birds. The colour of the fruits of some species 
is dark and purplish, whilst in others it is a bright blue. In the last 
case the fruits are very conspicuous and sappy. A Solomon 
Island species collected by me and a Malayan species observed 
by Ridley had bright blue fruits, and Cheeseman refers to the 
Rarotongan species as possessing fruits of this hue. Their colour, 
therefore, would often aid in attracting birds, and we are not 
surprised to learn that they form a favourite food with fruit-pigeons, 
parrots, and other frugivorous birds in different regions. Amongst 
the fruits found by Professor Moseley in the crops of fruit-pigeons 



xxvi EL^EOCARPUS 337 

in the Admiralty Islands were those of Elaeocarpus ; whilst in the 
Solomon Islands I noticed that the blue fruits of the "Toa," a 
species of the genus, were a favourite food of the same birds (Bot. 
Cliall. Exped., iv. 307, 308; Guppy's Solomon Islands^ 293, 295). 
We learn also from Hochstetter and from Sir W. Buller that the 
drupes of the " Hinau " (Elaeocarpus) form a favourite food of 
the parrots and fruit-pigeons of New Zealand (Hochstetter's New 
Zealand ; Buller's Birds of New Zealand). 

The question of size acquires considerable importance when we 
come to consider the transport of the seeds of the genus to a 
group of islands lying, like Hawaii, in the middle of the Pacific 
Ocean. The protection of the seed is also another important 
matter. There can, however, be no doubt that the hard woody or 
often osseous " stone " sufficiently protects the seed. With regard 
to size, if we were to judge from the dimensions of the fruits of 
some of the Fijian species, where, as I found, the "stone" measures 
from 3 to 5 centimetres (ij to 2 inches) in length, we might be led 
to form a very erroneous opinion of the capacity of the genus for 
conveyance through the agency of frugivorous birds to Hawaii. 
But when we turn to the Hawaiian species we find the difficulty 
much diminished, though still serious, the fruits being smaller and 
possessing a " stone " 2 \ centimetres or about an inch long. In 
other regions, however, the genus may possess fruits yet smaller in 
size. The Tongan endemic species, as described by Burkill, has 
fruits 17 cm. or T 7 ^ of an inch in length ; and closely similar 
dimensions are given by Kirk for a New Zealand species. In both 
these cases the " stone " would not be more than half an inch or 
I '2 cm. in length, and this would also apply to the Solomon Island 
species above mentioned. In another New Zealand species, where 
the drupe is only half an inch, the " stone " would be still smaller. 
It is thus evident that the fruits of different species vary greatly in 
size in different regions, and that there is no difficulty in assuming 
that a small-fruited species could be dispersed over the Pacific 
by frugivorous birds, and carried either to Hawaii or New 
Zealand. 

It might be an interesting point to determine to what extent 
a species in an oceanic island could effect its own isolation by 
developing a " stone " too large and too heavy to be transported 
across an ocean by birds, such as seems to have happened with 
some Fijian species. But a similar curious question is raised 
by the deterioration of a drupe in its capacity for dispersal by 
frugivorous birds, when, as in the case of the Hawaiian species 
VOL. II. Z 



338 A NATURALIST IN THE PACIFIC CHAP. 

of Elaeocarpus, the drupes become dry and almost sapless. As 
remarked in Note 68, this same feature is to be noticed in the 
fruits of some of the Hawaiian endemic genera. This, of course, 
would be quite in accord with what we should expect from the 
standpoint of dispersal. 

I will conclude these remarks on Elaeocarpus with a reference 
to the similarity of its distribution with that of Freycinetia. Both 
genera are at home in the temperate rain-forests of New Zealand 
and in the tropical rain-forests of the Pacific islands and of 
Malaya. Their capacities for dispersal are so different and so 
unequal, the dispersal of Freycinetia being seemingly so much 
more readily effected, that we can only suppose that time has long 
since discounted any special advantage one genus possesses over 
the other as regards distribution. 

DODON^A (Sapindaceae). 

This genus of small trees and shrubs includes between fifty and 
sixty known species, of which about forty are confined to Australia ; 
but a few species are found over the tropical and subtropical regions 
of the world, extending sometimes into temperate latitudes. There 
are, it seems, only three species known from the oceanic groups of 
the tropical Pacific : one, the cosmopolitan Dodonaea viscosa, that 
occurs in every island of volcanic formation ; and two others 
associated with it in the Hawaiian Group, to which they are 
restricted. We have thus repeated in this genus what is true 
of several other genera in Hawaii, such as Metrosideros and 
Wikstrcemia, namely, the occurrence in that group of a widely - 
ranging species accompanied by other species peculiar to those 
islands. In the case of Dodonaea in Hawaii we should not expect 
to find it very difficult to connect the endemic species with the 
widely-ranging D. viscosa, which is a very variable species. The 
extreme forms in different parts of the world are so different in 
character that Bentham viewed this species as probably including 
the whole of the extra- Australian species, excepting perhaps the 
Hawaiian endemic species and one or two South African and 
Mexican plants (Bot. ChalL Exped., iii. 136). 

Of the two Hawaiian peculiar species, one, Dodonaea eriocarpa, 
is a mountain shrub found in most of the large islands and occur- 
ring sometimes at elevations of 6,000 to 8,000 feet. The other 
species, D. stenoptera, is, according to Hillebrand, a very distinct 
species found only on Molokai. Bentham was only acquainted 



xxvi DODONAEA 339 

with the first-named, and his hesitation to include it as one of the 
innumerable forms of the widely-ranging D. viscosa is very sugges- 
tive. However, whether or not one or both of these peculiar forms 
are connected in their origin with this species, it is certain that the 
genus has been established for ages in Hawaii ; and from D. viscosa 
we can learn how a species of the genus can cross an ocean, and 
also how from a widely-ranging species exhibiting extreme varia- 
bility species peculiar to a group of islands could have been 
derived. 

The great variability of Dodonaea viscosa is associated with 
great adaptability to different stations. Thus, as Mr. Hemsley 
tersely puts it, it is one of those plants that thrive on the sea-coast 
as well as inland, and in almost any soil or situation provided, it 
may be added, that the station is well exposed to the sun. Although 
Mr. Ridley characterises it as a regular sea-shore plant in the Malay 
peninsula, and although Prof. Schimper places it in the Indo- 
Malayan strand-flora, it is as an inland plant that it is most charac- 
teristic of the Pacific islands ; and the key to its powers of adapta- 
tion to different stations is to be found in its xerophilous habit. 
It is essentially a plant of sunny places, and is equally at home on 
the parched inland plain, in the open wood, on the sandy beach, 
on an old lava-field, or on rocky declivities. It is not a plant of 
the rain-forest, preferring dryness to humidity and sunshine to 
shade. 

The following remarks on the mode of dispersal of the wide- 
ranging Dodonaea viscosa will serve to roughly indicate the 
capacity of the genus for distribution. It is a subject, however, 
that requires further detailed investigation. The light, inflated, 
winged capsules of this species, about an inch across, could be 
blown for long distances along the ground and carried for short 
distances in the air by strong winds, but, as is also remarked by 
Prof. Schimper (Ind. Mai. Strand-flora, p. 157), they are much too 
large to be transported by winds across a broad tract of sea. The 
currents, however, may have aided in the dispersal of the species 
in the case of island-groups 500 or 600 miles apart. Although the 
membranous capsules before dehiscing would be unable to with- 
stand the " rough-and-tumble " of ocean-transport for more than a 
few days, the seeds possess some floating powers of a purely acci- 
dental nature due to the imperfect filling up of the seed-cavity in 
some of the seeds. In an experiment made in Hawaii I found 
that only half the seeds floated in sea-water. Prof. Schimper, in an 
experiment conducted in Germany with seeds that must have been 

z 2 



340 A NATURALIST IN THE PACIFIC CHAP. 

well dried by keeping, found that they floated for from ten to sixty 
days. This limited capacity for flotation might possibly allow the 
species toreach Tahiti by easystages from Fiji ; but it is not sufficient 
to explain its occurrence in the more isolated Hawaiian Group. The 
fruits and seeds of this plant never, however, came under my notice 
in the floating or stranded seed-drift of Fiji ; and I am not inclined, 
for this and the reasons above mentioned, to consider that the cur- 
rents have been very effective agents in dispersing this plant over 
the Pacific islands. 

Hillebrand endeavoured to account for the wide distribution ot 
Dodonaea viscosa by " the glutinous capsules which would easily 
adhere to the plumage of birds." It may be here remarked that in 
the dried state specimens of the plant have a varnished appearance 
as respecting the leaves, branchlets, and capsules. In the living 
condition this is represented by a glutinous or viscid condition of 
the surface of these portions of the plant, rendering them adhesive 
to the touch. I found, however, that only the immature capsules 
are markedly " sticky," and that in any case the adhesive power 
was quite insufficient to allow of adherence for any length of time 
of fruits of this size to a bird's feathers. Mr. Ridley, who allows 
much latitude to birds in matters of dispersal, remarks that the 
stickiness only appears when the specimen is dry (Trans. Linn. 
Soc. Bot., 1888-94, p. 289). It is, nevertheless, likely that the crus- 
taceous seeds, which do not exceed \ of an inch (5 mm.) in size, 
when swallowed by a bird granivorous in its diet, might be voided 
unharmed, and the dispersal of the species assured. It is in this 
fashion, I imagine, that the plant reached distant groups like Tahiti 
and Hawaii. 

There is, of course, the possibility that man has in past times 
aided in the distribution of Dodonaea viscosa over the warmer 
regions of the globe. But such an agency seems largely discounted 
in the case of an isolated archipelago like Hawaii by the occurrence 
of endemic species. Nor does the usual station in the Pacific 
islands support the view that it was introduced by the aborigines. 
According to Hillebrand, it possesses a variety (var. spathulata) in 
Hawaii which seems also to occur in Tahiti and New Zealand. 
Nadeaud observes that in Tahiti it grows as a bush on dry crests, 
and as a small tree, ten feet in height, in the mountains. 

Nor do the aboriginal names of Dodonaea viscosa point in the 
direction of man's agency. It possesses a different name in every 
group, and is evidently not a plant with which the ancestors of the 
Polynesians were familiar in the home of the race. Thus it is 



xxvi METROSIDEROS 341 

named " aalii " in Hawaii, " apiri " in Tahiti, " ake " in Rarotonga, 
" lala vao " in Samoa, and I may add " usi " or, as Seemann writes 
it, " wase" in Fiji. 

Looking at these various facts, I am not inclined to exclude 
altogether any one of the three agencies above discussed ; but I 
should imagine that, placed in their order of effectiveness, we should 
have first birds, then the currents, and lastly man. 



METROSIDEROS (Myrtaceae) 

Whilst this genus of trees and shrubs has its home in New 
Zealand and Australia, there is an extremely variable Polynesian 
species, Metrosideros polymorpha, ranging over all the volcanic 
groups of the tropical Pacific, from Fiji to Pitcairn Island and 
from Hawaii to the Kermadec group, but seemingly only in the 
Hawaiian group associated with endemic species. According to 
the Index Kewensis the genus comprises about forty known species, 
of which two-thirds are confined to New Zealand and Australia in 
equal proportions ; whilst, among the rest, six species belong to 
New Caledonia, two to Hawaii, and three to Malaya, and there 
are solitary species in Chile, Madagascar, and South Africa. 

I will attack the problem connected with the distribution 01 
the genus through the widely-ranging Polynesian species, Metro- 
sideros polymorpha. " This genus," wrote Dr. Seemann, " is in a 
fair way of becoming in Polynesia what Rubusis in Europe. It is 
very much given to variation, and it is very difficult to find out the 
limits of the different species." In making these remarks he had 
this species in view, and his adoption of Gaudichaud's specific name 
of " polymorpha " to cover almost all the Polynesian forms has been 
generally followed. Although so widely distributed over the 
Pacific, it is in the Hawaiian Islands that this tree attains its greatest 
development, growing gregariously and often forming almost ex- 
clusively entire forests ; and it is here that it displays the greatest 
variation. But it was remarked by Seemann, and this was con- 
firmed by Hillebrand, that almost all the Hawaiian forms occur in 
the Society or Tahitian Islands. 

In connection with the great variability of Metrosideros 
polymorpha must be considered its variety of stations and its great 
range in altitude. Hillebrand describes seven Hawaiian forms of 
this species, and their various stations and characters are well 
illustrated in his descriptions. Thus, whilst the trees may attain a 
height of forty feet in the forests, in elevated exposed situations 



342 A NATURALIST IN THE PACIFIC CHAP. 

they may be small and gnarled or low and shrubby ; whilst in the 
bogs and swamps of the high levels of Maui and Kauai the plant 
grows as a prostrate shrub. It is not at all unlikely that the two 
peculiar Hawaiian species of the genus had a common origin from 
a widely-ranging species, which, if not the present M. polymorpha, 
was its immediate ancestor. One of them was, indeed, included by 
Dr. Seemann within the wide limits of this species, and the other 
was accepted with a doubt. 

To illustrate the great vertical range in the Hawaiian Group of 
Metrosideros polymorpha, I will take it as I found it in the island 
of Hawaii. Here it ranges from the coast up to about 8,000 feet 
above the sea. But it is in the middle forest-zone at elevations of 
2,000 to 4,000 feet, where it is often associated with the Koa and 
Olapa Trees (Acacia koa and Cheirodendron Gaudichaudii), that it is 
most at home and attains its greatest size. Higher up at heights 
of 5,000 to 7,000 feet in the more open forests it is still in the 
company of the trees just named together with Sophora chryso- 
phylla and Myoporum sandwicense. At 8,000 feet it becomes very 
stunted and is accompanied usually by bushes of Cyathodes and 
other plants of similar bushy growth. In the lower parts of its 
range, from 2,000 down to 1,000 feet, it forms forests with the 
Kukui Tree (Aleurites moluccana), mingled also with smaller trees 
such as the Hawaiian Olive (Osmanthus), and the Kopiko 
(Straussia). Below 1,000 feet, and wherever bold promontories reach 
the coast and the inland forest descends to the sea, we find it 
associated with such trees and shrubs as the Lama (Maba sandwi- 
censis) and different Akeas (Wikstrcemia). On the partially 
vegetated surfaces of old lava-flows near the coast it grows beside 
bushes of the Ulei (Osteomeles anthyllidifolia) and of Cyathodes. 

Compared with its behaviour in Hawaii, Metrosideros poly- 
morpha takes a relatively unimportant part in the vegetation of 
Fiji. As Home observes, the trees are most common in the dry 
parts of the two largest islands and grow in the poorest soil. I 
found them in Vanua Levu usually in open exposed situations, 
generally in the dry " talasinga " plains on the north side of the 
island, where they were associated with Acacia Richii, Dodonaea 
viscosa, and Casuarinas ; and sometimes they occurred in a shrubby 
form on the rocky peaks of the highest mountains. In Rarotonga 
also, as we learn from Cheeseman, it is on the tops of the rocky 
peaks and along the crests of the ridges that this species, which is 
abundant in the island, is frequently found. 

I may here allude to the curious fact observed by me on the 



xxvi METROSIDEROS 343 

upper open wooded slopes of Mauna Kea at elevations of 6,000 to 
7,000 feet, and therefore on the outskirts of the true forest-zone. 
Here the Ohia Tree, as the Hawaiians name Metrosideros poly- 
morpha, often grows in close association with the Olapa Tree 
(Cheirodendron Gaudichaudii). In one locality, for instance, a 
large Olapa was growing in the fork of an Ohia at about eight feet 
from the ground, and sending down roots on either side. Some- 
times the trunks of the Olapa and the Ohia were to be seen growing 
in such close contact as to look like one tree. In one such case a 
young tree, four feet high, of Myoporum sandwicense was growing 
in a fork of the Ohia, whilst in a fork of the Olapa a plant of 
Vaccinium penduliflorum, three or four feet in height, had 
established itself. This remarkable instance of epiphytic growth 
also proved to be quite a revelation with regard to the dispersal of 
seeds in this island. Amongst these four associated plants, which 
include three trees and one shrub, all except the Ohia, which was 
probably the original tree, have fruits that would attract frugivorous 
birds ; and in succession these birds had first dropped a pyrene of 
the Olapa in the fork of the Ohia, and afterwards the seeds of 
Myoporum again on the Ohia, whilst finally the Vaccinium seeds 
were dropped into the fork of the Olapa after it had developed into 
a tree. 

The mode of dispersal of the seeds of Metrosideros polymorpha 
now invites our attention. Since the fruits are dry, dehiscent 
capsules possessing minute fusiform seeds, we are not able to 
appeal directly to the agency of frugivorous birds to explain the 
wide dispersal of this species. The seeds are light in weight and 
remind one a little of those of the succulent fruits of Freycinetia. 
For purposes of dispersal, however, they must be placed in the 
same category with other plants with dry, dehiscent fruits and small 
seeds, such as the Vota (Geissois ternata) of Fiji, a tree that in 
those islands grows in similar stations. On a later page I have 
suggested that the seeds of the Vota are dispersed by large bats 
that visit the trees for the sake of the honey in the red flowers. 
With Metrosideros polymorpha birds act probably in the same way. 
We are, in fact, informed by Mr. Perkins that the nectar-feeding 
birds of the Hawaiian Drepanids now obtain their main supply of 
this food from the blossoms of this tree. If bats or birds visit the 
large red flowers of Metrosideros polymorpha for the same 
purpose, it is not difficult to imagine that they might carry away 
in their fur or in their plumage some of the small seeds shaken 
out of old dehiscent capsules. In this connection we may note 



344 A NATURALIST IN THE PACIFIC CHAP. 

that the Kaka Parrot (Nestor meridionalis) of New Zealand is 
said to feed largely on the scarlet blossoms and nectar of 
Metrosideros robusta (Evans' Birds, p. 374). 

The seeds of Metrosideros polymorpha might no doubt be 
carried by winds from one mountain-top to another and across 
narrow straits, but only whilst adherent to a bat or a bird could 
they be carried across a wide tract of ocean. Speaking of the 
genera Metrosideros and Lobelia in connection with their 
occurrence in the Kermadec Islands, Sir J. Hooker long ago 
referred to their minute seeds as not adapted for transport across 
oceans unless their minuteness and number fitted them for it (Journ. 
Linn. Soc., i. 127). The point that is raised here for these genera 
in the Kermadec Group can be raised for the same two genera in 
Hawaii and for a multitude of other small-seeded genera in those 
islands. 

ALYXIA (Apocynaceae). 

This genus of climbing or straggling shrubs tells its own story 
of the widely dispersed Indo-Malayan genera in the Pacific islands. 
Containing about forty known species, it is distributed over the 
tropical regions from Madagascar and the Mascarene Islands east- 
ward to the Paumotu Group and Pitcairn Island in mid-Pacific, 
and has its focus in the area comprised by Malaya, Australia, and 
New Caledonia. In the Index Kewensis about eight species are 
assigned to New Caledonia, seven to Australia, and seven to 
Malaya. One species, Alyxia stellata, ranges over nearly the 
whole of the area of the genus from tropical Asia, through 
Malaya, across the South Pacific to Tahiti. It will be for the 
future investigator to determine how far the present distribution of 
the genus can be connected with one or two widely-ranging poly- 
morphous species. The data at my disposal seem to show that in 
the open Pacific, at all events, the history of the genus has gone a 
step beyond this stage. 

Of the seven or eight species recorded from the Pacific islands 
east of New Caledonia, only two or three seem to be now 
recognised as restricted to particular groups, namely, one in Hawaii 
(Schumann), one in Fiji, and one in Rarotonga. The other species 
indirectly connect together all the groups, although no single 
species occurs over the whole region. Thus the Hawaiian species, 
Alyxia olivaeformis (Gaud.) has in recent years been found in 
Upolu, in the Samoan Group, by Dr. Reinecke, an exceedingly 
interesting though unusual specific link between these two 



xxvi ALYXIA 345 

archipelagoes. Two species, A. stellata and A. scandens, range 
over the South Pacific from Fiji to Tahiti, the last-named also 
occurring in the Paumotu or Low Archipelago ; whilst Rarotonga 
possesses a form closely allied to the first-named, and to it Cheese- 
man has given specific rank. Another species, A. bracteolosa, 
links together the contiguous Fijian, Tongan, and Samoan groups. 
This distribution is what we should have expected if one or two 
polymorphous species had originally ranged over the Pacific and 
were advancing towards that stage of differentiation when each 
group possesses its own peculiar species. (It may be here 
remarked that an undetermined species of Alyxia is accredited by 
Maiden to Pitcairn Island, which indicates that the genus has 
extended east in the Pacific almost as far as the extreme limit of 
the Polynesian region. Australas. Assoc. Reports, Melb., 1901, viii.) 

All visitors to these islands that are interested in their floras 
will be familiar with the Alyxias ; and there are few of their plants 
that the natives take more pleasure in pointing out to white men. 
They are readily recognised on account of their black moniliform 
drupes and their milky sap. All over Polynesia, whether in 
Hawaii, Tahiti, Samoa, or Fiji, the aborigines value the plants on 
account of the delicate fragrance of their foliage and bark. These 
materials they use for personal decoration and in making wreaths, 
stripping off the bark of the young branches with their teeth in the 
same fashion in Fiji and Hawaii and probably in all the Pacific 
islands. Throughout Polynesia, excluding Fiji, they bear the same 
name, which takes the form of " maile " in Hawaii and Samoa, and 
of " maire " in Tahiti and Rarotonga a name which the Maoris, 
remembering the Alyxias of their tropical home in the South 
Pacific, have applied to New Zealand species of Olea and Eugenia. 
The Fijian generic name for Alyxia is " vono." 

A word may be said about the station of these plants in the 
Pacific islands. In Hawaii they occur in the middle and lower 
forests, and usually between 2,000 and 4,000 feet in elevation. In 
Tahiti they frequent the crests and precipitous rocky slopes of the 
mountains at elevations of from 3,000 to over 6,000 feet. The 
Rarotongan species often forms extensive thickets in rocky 
localities on the hills. In Samoa they are found usually in the 
mountain forests. In Fiji they grow on the outskirts of the virgin 
forests and on rocky sparingly vegetated mountain peaks. I found 
them often in Vanua Levu growing amongst the open vegetation 
on the summits of isolated mountains at elevations of 2,000 to 
2,500 feet, where they were associated with other plants like 



346 A NATURALIST IN THE PACIFIC CHAP. 

Elseocarpus, Pleiosmilax, and Scaevola, possessing similar fleshy 
fruits likely to be dispersed by frugivorous birds. 

The Alyxias indeed seem well suited for dispersal by birds. 
The black fleshy drupes would readily attract them ; and the 
solitary seed protected by a very tough horny albumen might be 
ejected unharmed in their droppings. 



It would be possible to enter into similar detail with several 
other genera of this period ; but here I can only direct attention to 
their principal indications, permitting myself a little more license 
when discussing the means of dispersal. 

ALPHITONIA (Rhamnacese). Amongst other genera with 
polymorphous species closely following the lines taken by 
Metrosideros in the Pacific is Alphitonia, a small Malayan and 
Polynesian genus of tall trees, containing at most three or four 
species, one of which (A. excelsa) has almost the range of the 
genus and is found in most of the Pacific archipelagoes. So 
variable is this widely-ranging tree that Bentham suggested that 
there was only one species in the genus (Bot. Chall. Exped.^ iii. 
133), a suggestion especially interesting in connection with the 
role taken by polymorphous species in the Pacific. As bearing on 
the mode of dispersal of this species, it may be observed that my 
Fijian experiments show that the fruits are not fit for transport by 
currents. With the mature drupe the outer coverings become 
pulverulent, and the fruit breaks down, freeing the pyrenes which 
do not float ; nor have the seeds any buoyancy. Although the dry 
drupes would seem unattractive to birds, it is to birds we must 
look for the dispersal of the genus. 

PlSONiA (Nyctaginese). Like Dodonaea, Metrosideros, and 
Alphitonia, the cosmopolitan genus Pisonia possesses a poly- 
morphous species that displays its variation in every Pacific group 
and occupies a considerable number of stations. The earlier 
botanists in the Pacific differed much as to the species of this 
region, and this led Mr. Hemsley to observe in his paper on 
the Tongan flora that it is difficult to understand the various 
Polynesian and Australian species except on the assumption that 
there is one very variable species. Recognising this difficulty, 
Drake del Castillo deals somewhat summarily with nearly all these 
forms, uniting them under one comprehensive species, P. umbellifera 
(Seem.), thus constituting " une espece tres-polymorphe " that 
ranges (generally in maritime districts) over tropical Asia and the 



xxvi PISONIA 347 

islands of the Indian and Pacific Oceans, extending to North-East 
Australia and to New Zealand. On account of the unusual 
capacity for dispersal possessed by this species a subject to be 
immediately discussed the tendency to specific differentiation has 
been kept in check, though the process has gone farther in some 
groups than in others, as in the case of Hawaii, where Hillebrand's 
endemic species has, however, been included by Drake del Castillo 
in his polymorphous species, P. umbellifera. 

The fruits of this genus possess no capacity for dispersal by 
currents. They never came under my notice either in floating 
or stranded seed-drift, and have little or no buoyancy. Prof. 
Schimper, experimenting on the well-dried fruits of Pisonia 
aculeata, a seaside shrub common in America and in the Old 
World, and destined probably to be brought by the systematist 
into touch with the polymorphous P. umbellifera, found that they 
sank in a day or two (Ind. Mai. Strand-flora, p. 156). Dismissing 
the agency of the current, he looked to that of the bird for the 
explanation of the dispersal. The probability of the effectiveness 
of this last-named agency has long been surmised. It attracted 
the notice of Darwin and especially invited the attention of another 
student of plant-dispersal, Dr. H. O. Forbes. The long, narrow,, 
often fusiform fruits are invested by a somewhat coriaceous 
perigone and range from less than an inch to three inches in 
length (2 7-5 cm.). They excrete a very viscid fluid often in 
quantity, and sometimes also possess glandular spines. The 
Hawaiians, according to Hillebrand, used this material as bird- 
lime for catching birds, and the fruits, he says, will stick fast to the 
paper in the herbarium for years. In that group I often found the 
fruit adhering firmly to my clothes. Writing of these trees on 
Keeling Atoll, Forbes observes that their sticky fruits are often 
such a pest to birds roosting in their branches that they have 
proved fatal to herons and boobies by collecting in their plumage. 
" It is easy to perceive," he remarks, " how widely this tree might be 
disseminated by the birds that roost on it" (The Eastern Archi- 
pelago, p. 30). In New Zealand, as we learn from Kirk, the viscid 
fruits of Pisonia brunoniana attract small birds which become 
firmly caught and die miserably. A cat has been known to wait 
under a tree watching its opportunity of preying on the entangled 
birds. ' Sir W. Buller states that the New Zealand fruit-pigeon 
feeds at times on the green fruits of P. umbellifera ; and we can 
infer that it occasionally carries off some of the riper fruits in its 
feathers. 



348 A NATURALIST IN THE PACIFIC CHAP. 

WlKSTRCEMlA (Thymelaeacese). This is a small genus of shrubs 
and small trees, with red or yellowish drupes fitted for dispersal 
by frugivorous birds, that is confined mainly to tropical Asia, 
Australia, and Polynesia. Following Seemann and Drake del 
Castillo, we may say, that like several other genera of this period, 
this genus possesses in the tropical Pacific a widely-ranging 
species, W. indica, that occurs in Hawaii, the Marquesas, Tahiti, 
Samoa, and Fiji, growing amongst the vegetation immediately 
behind the beaches and in the plains and open wooded districts 
inland. In Hawaii it is associated with half a dozen peculiar 
species, and in Tonga there is also an endemic species. The widely- 
ranging species has its home in the Indian Archipelago and in the 
Asiatic mainland, and occurs also in Australia. According to 
Gray, the American botanist, it is represented by a different 
variety in almost every group in the tropical Pacific, and it presents 
us therefore with another example of a polymorphous species 
which links Polynesia directly with Malaya. As bearing on the 
dispersal of the genus by birds, it may be added that Mr. Perkins 
in the Fauna Hawaiiensis speaks of some of the Drepanids and of 
a species of Phaeornis as feeding at times on the fruits of these 
plants. 

PEPEROMIA (Piperaceae). All observers of tropical plant-life 
will be familiar with this genus of low herbs growing on tree- 
trunks, on the soil, on rocks, and on stonewalls, and comprising 
about 500 known species distributed over the warmer regions of 
the globe and sometimes extending into cooler latitudes. In 
Polynesia it attains its greatest development in Hawaii, where 
Hillebrand enumerates about twenty species, of which, after ex- 
cluding doubtful forms, at least a third must be endemic. Tahiti, 
Samoa, and Fiji are each known to possess three or four species, 
of which one is usually restricted to the group. Two species, 
P. reflexa and P. leptostachya, link together nearly all the groups 
of the tropical Pacific, including Hawaii, the first cosmopolitan, 
and the second hailing from North-East Australia and indicating 
that the genus has entered Polynesia from the west. . . . These 
plants possess spikes of small berries containing a single seed, 
and are evidently, like other Piperaceae, dispersed by frugivorous 
birds. It is to be noted that the presence of a West Indian and 
Mexican species in the Bermudian caves is attributed by Mr. 
Hemsley to frugivorous birds (Bot. Chall. Exped., Introd. 49, i. 62). 
In Vanua Levu they occur on the bare rocky peaks of some of the 
mountains under such conditions that the seeds could only have 



xxvi EUGENIA 349 

been brought by birds. Thus, on the bare surface of a large block 
of tuff forming the highest peak of Koro-Mbasanga, 2,500 feet 
above the sea, I found only two plants, Oxalis corniculata and a 
species of Peperomia. 

EUGENIA (Myrtaceae). This is a very extensive genus split up 
into different subgenera, and comprising some 600 or 700 known 
species scattered over the warm regions of the globe. Their 
fleshy, usually red, berries contain as a rule one or two large seeds, 
and attract birds and animals of all descriptions. The feature 
most interesting to us is the dispersal of the genus over the Pacific 
islands eastward to the Low Archipelago and northward to Hawaii. 
The track by which it has entered the Pacific from the west is 
indicated in the distribution of the species. The genus is only 
well represented in the Western Pacific, whilst eastward and 
northward of Samoa and Tonga the distribution is fitful and 
irregular, it being evident that the extension beyond these two 
groups has been accomplished with difficulty. 

There are at least twenty-five species in Fiji, of which perhaps 
half would be peculiar ; in Tonga eight species, of which two may 
be endemic ; in Samoa thirteen species, of which four are peculiar ; 
in Rarotonga none ; in Tahiti a single non-endemic species ; and 
in Hawaii two species, of which one is peculiar. Only truly 
indigenous species are here recorded, and Eugenia malaccensis, 
which has accompanied the aborigines in their migrations, is not 
included. A solitary species, E. rariflora, connects together all the 
principal archipelagoes from Fiji to Tahiti and the Gambier 
Islands, and northward to Hawaii. Nine species are known to be 
common to the region in which lie the three groups of Fiji, Tonga, 
and Samoa ; and since some of these species occur in the groups 
further west they may be regarded as keeping up the connection 
with the original home of their ancestors in the Malayan region. 

Looking at these facts of distribution of the genus Eugenia 
in the open Pacific, it is evident that whatever dispersal of the 
genus is now in progress in this ocean is mainly confined to 
an interchange between the groups of Fiji, Tonga, and Samoa 
in the Western Pacific, and doubtless between the islands further 
west of these groups. The smaller islands lying between and 
around these three groups participate in the distribution of the 
species common to all. Thus Wallis Island, according to Drake 
del Castillo, possesses two of these species. Over the rest of 
the ocean the dispersal of the genus seems to be no longer 
effective, since Eugenia rariflora, which links together Fiji, Tahiti, 



350 A NATURALIST IN THE PACIFIC CHAP. 

and Hawaii, shows signs of differentiation in nearly every group. 
In Hawaii, where it is very rare and is only recorded from two of 
the islands, it has developed a small-leaved variety. In Tahiti 
it displays the same variation ; and Seemann observes that there 
are differences between the Tahitian and Fijian species which may 
be almost specific in value. It would also appear that both 
in Hawaii and Tahiti the fruits have become less attractive to 
birds, being described as " dryish " and " dry," which is, as Dr. 
Seemann remarks, certainly not true of the Fijian plant. 

In Fiji the Eugenias, as small trees and shrubs, find their home 
usually on the banks of streams and rivers, on the outskirts of 
forests, and occasionally at the coast. One of them, E. richii 
(Gray), is a characteristic littoral tree in the group. A tree near it 
in character was found by me of common occurrence in the interior 
of coral islets in the Solomon Group {Solomon Islands^ p. 297). 
E. rariflora occurs also in the interior of coral islets in Fiji and 
amongst the vegetation at the back of the mangrove-swamps. 

Coming to the mode of dispersal of the genus in the Pacific, I 
may remark that all the species, with the doubtful exception of the 
Fijian and Samoan Eugenia neurocalyx (the Lemba of Fiji), are 
wild trees and shrubs useless to man, but much appreciated by 
pigeons, pigs, &c., on account of their fleshy fruits. Since exact 
observations on the possibility of their dispersal by currents 
seemed to be wanting, I made some experiments in Fiji. Out of 
six species, which included E. corynocarpa, rariflora, richii, and 
rivularis, the mature fruits of most species sank in sea-water 
in from seven to ten days. However, those of the beach tree, 
E. richii, floated for a fortnight. The cause of sinking in all cases 
lay in the decay of the outer fleshy covering. As I have observed 
in river and sea drift, fish bite at the floating fruits, and in this 
manner the seeds would soon be liberated and sink. The seeds of 
all the plants sank at once in my experiments except with one 
species, where the seed loosely filled its test and thus a floating- 
power of a few days was acquired. Currents, it is apparent, could 
never account for the dispersal of the genus over a broad extent of 
ocean, though in a few cases, as in that of the littoral tree above 
noted, it is quite possible that the fruits could be successfully 
transported across a tract of sea 200 or 300 miles in width. 

It has long been known that fruit-pigeons are fond of the fruits 
of wild species of Eugenia, and I found the Solomon Islanders and 
the Fijians well acquainted with the fact. The fruits of a tall 
Eugenia tree, near E. richii, common in the interior of the 



xxvi EUGENIA 351 

coral islets of Bougainville Straits in the Solomon Group, were 
found by me in quantities in the crops of fruit-pigeons shot by 
Lieut. Heming and Lieut. Leeper on the islets {Solomon Islands, 
pp. 293, 297 ; Bot. Chall, Exped., Introd. 46, iv. 312). Dr. Seemann 
remarks that in Fiji the red fruits of E. brackenridgei are eaten by 
pigeons. The somewhat thin coverings of the seeds of this genus 
would seem to offer but a slight protection in a bird's stomach, 
though in one species the test was almost crustaceous. 

Most species possessed only one or two large seeds in each 
fruit, though this number may vary in the same individual. Thus, 
out often fruits of Eugenia rariflora in Fiji, six had one seed, three 
had two seeds, and one had three seeds. In the fruit of E. neuro- 
calyx, however, the seeds range from three to five. 

It is the question of size that is of importance in considering 
the possibility of birds transporting the seeds over a broad tract of 
ocean. Eugenia rariflora, the species found all over the Pacific, 
has seeds that measure in the Fijian plant one-fourth to one-third 
of an inch (6 to 8 mm.) across ; and in Hawaii, according to Hille- 
brand, they would perhaps be rather smaller. In point of size 
there is less difficulty with regard to the transport by birds across 
the ocean to Hawaii of the seeds of Eugenia rariflora than with the 
"stones" and seeds of some other genera, like Elaeocarpus, 
Osmanthus, and Sideroxylon, that must have been conveyed there 
by the same agency. The fruits of several of the Fijian species 
are of the size of a large cherry ; but it is noteworthy that in those 
species like E. corynocarpa and E. neurocalyx, where the fruits are 
large and the seeds about an inch in size, the plants are confined to 
the Western Pacific only, namely, to the Fiji-Samoa region. 

There is therefore no difficulty, from the standpoint of size, in 
accounting for the distribution by birds of the widely-ranging 
Eugenia rariflora over Polynesia ; but at first sight there seems to 
be a real difficulty with regard to the protective coverings of the 
seed. Yet Nature speaks with no hesitating voice in the matter. 
The West Indian and Florida species, E. monticola, regarded as 
indigenous in the Bermudas, must have reached that group through 
the agency of birds that carried its seeds over quite 800 or 900 
miles of sea ; and it may here be noted that South Trinidad, lying 
some 600 miles off the coast of Brazil, and Rodriguez, distant 
about 330 miles from Mauritius, each possess species (Bot. Chall. 
Exped., Introd., 12, i. 32, ii. 128). If fruit-pigeons can transport 
Eugenia seeds across 600 or 800 miles of ocean, there would be 
no difficulty in accounting for the stocking of the Fijian, Tongan, 



352 A NATURALIST IN THE PACIFIC CHAP. 

and Samoan Islands with the genus from regions to the west. 
But the occurrence of the genus in Hawaii seems to compel 
us to assume that the seeds have been carried in a bird's 
stomach over 1,500 to 2,000 miles of ocean. This difficulty, 
however, does not really exist. Eugenia rariflora, the Polynesian 
species found in Hawaii, frequents, as before observed, coast 
districts and coral islets in Fiji, and if we suppose that the 
low islands of the Fanning and Phoenix Groups, lying between 
Hawaii and Samoa, have served as stepping-stones, a capacity 
of crossing 1,000 miles of ocean would be alone required. This 
is not much in excess of the distance that must have been 
traversed by the bird that first brought the seeds of Eugenia 
monticola to the Bermudas. 

Other genera like Morinda and Scaevola, possessing fleshy fruits 
dispersed by frugivorous birds, have been mentioned in different 
connections in other parts of this work, and will not be further 
dealt with here. But before concluding this chapter I will refer 
briefly to one of the disquieting mysteries in the flora of the 
Pacific which is presented to us in the genus Gossypium. Three 
species are, or were, truly indigenous in this region. One is 
Gossypium drynarioides, a small endemic tree found by Nelson, 
the companion of Captain Cook, in Hawaii, which was very rare in 
Hillebrand's time, and is perhaps now extinct. The second is G. 
tomentosum (Nuttall), which is also peculiar to Hawaii, where it 
is found on the beaches. I am following here the Index Kewensis ; 
but it should be remarked that this species occurs also in Fiji, though 
Seemann regards it as introduced. The third is G. religiosum (L.), 
found by Captain Cook's botanists growing wild in Tahiti, and hail- 
ing from the tropics of the Old World. The seeds of the first species 
are covered with a short brownish tomentum, and could never have 
been of any value. The tawny wool of the seeds of the second 
species has a staple too short for cultivation ; whilst the Tahitians 
do not seem to have made any use of the third species. It is 
difficult to draw any conclusion concerning the presence of these 
plants in the Pacific islands at the time of their discovery ; nor can 
Dr. Seemann, who was especially well informed in these matters, 
aid us much in our endeavours to solve the mystery. From the 
aboriginal names we get no clue. The Hawaiian name of 
" huluhulu " seemingly refers to the hairy covering of the seed ; 
whilst the Tahitian " vavai " and " ovari " simulate the Fijian 
" vauvau," which is merely the reduplicated form of " vau " (the 
word in many shapes for Hibiscus tiliaceus in Malaya and Poly- 



xxvi GOSSYPIUM 353 

nesia), and is applied by the Fijians to Hibiscus esculentus and to 
the introduced species of Gossypium. 

When in Hawaii I ascertained that neither the seeds of the 
littoral plant, Gossypium tomentosum, nor those of two cultivated 
species possessed any fitness for dispersal by the currents, the 
scraped seeds sinking at once, whilst when covered with the wool 
they floated only for a few days. Further references to G. tomen- 
tosum in Hawaii are given in the index of this volume. 

TJie Last Stage of the General Dispersal of Plants of the 

Malayan Era. 

We arrive now at the close of the era of the general dispersal 
of tropical plants, mainly Malayan, over the Pacific, and this 
brings us down to our own age. The few genera that are still 
dispersed have no peculiar species in particular groups. The 
species which often range over all the groups, and retain as a rule 
their characters in most of them, do not therefore display, except 
in a few cases, that extreme variation which would give them a 
place in the ranks of the polymorphous species. The dispersing 
agencies, in fact, are sufficiently active to check marked variations, 
and the process of isolation has scarcely begun. 

We perceive the reason of this when we look at the nine genera 
which are taken as samples of this period, viz., Rhus, Osteomeles, 
Viscum, Plectronia, Boerhaavia, Polygonum, Pipturus, Boehmeria, 
and Dianella, most of them being known to be dispersed by birds 
at the present day. Six of the genera possess fruits likely to 
attract frugivorous birds ; whilst one of them, Boerhaavia, has 
sticky fruits that would be apt to adhere to plumage. Actual 
observations in the cases of Rhus, Viscum, and Plectronia establish 
the fact of their dispersal by fruit-eating birds ; and there is no 
difficulty in postulating the same agency for Osteomeles, Pip- 
turus, and Dianella. A method by which Boerhaavia fruits 
would be transported in the plumage of birds has been 
observed by Mr. Lister ; whilst the nutlets of Polygonum are 
known to afford food to a variety of birds and to be thus 
distributed. 

In this period the plants all hail from the Asiatic side of the 
Pacific. Three of the genera, Plectronia, Pipturus, and Dianella, 
belong almost exclusively to the Old World. Five occur in both 
the Old and New Worlds, but, as with Rhus, Viscum, Boerhaavia, 
and Bcehmeria, are represented by Old World species in the Pacific, 
VOL. II A A 



354 A NATURALIST IN THE PACIFIC CHAP. 

or, as with Polygonum, possess a cosmopolitan species (P. glabrum) 
ranging over the warm regions of the globe. Even Osteomeles 
presents no exception to the rule, since the Pacific plant is the only 
one of its species that is not American. 

We have in Polygonum glabrum the only aquatic or semi- 
aquatic plant widely distributed over the Pacific islands that can 
lay claim in all groups to be indigenous. It is associated in 
Hawaii with species of Potamogeton and Naias, aquatic genera 
that have, however, a limited distribution in Polynesia. 

I will now make a few remarks on each genus such as bear on 
their distribution and on their mode of dispersal in the Pacific. 

RHUS (Anacardiaceae). The representation of this genus by 
indigenous species in oceanic islands not only in the Pacific but 
also in the Atlantic, as in the Bermudas, is of especial interest in 
connection with dispersal by frugivorous birds, since the drupes are 
typically dryish and might appear to be not very attractive to 
birds. There are two Old World species known from the Pacific 
islands : one being R. simarubaefolia (Gray), distributed over the 
South Pacific groups from Fiji to Tahiti and hailing from Malaya ; 
the other, R. semialata (Murray), alone recorded from the Hawaiian 
Group and derived probably from China or Japan. This indication 
that the groups of the North and South Pacific have derived their 
species, the first from Temperate Asia and the second from Tropical 
Asia, is of some interest. In Samoa, according to Reinecke, the 
fruits of R. simarubsefolia, which are of the size of a pea, form the 
favourite food of the fruit-pigeons. That birds disperse the seeds 
of the various Sumachs is familiarly known. In the United States, 
as we learn from Barrows, Beal, and Weed, crows, woodpeckers, 
and other birds feed extensively in winter on the fruits of different 
species of Rhus, including the Poison Ivy (R. toxicodendron). 
The crows discharge the seeds in pellets after retaining them for 
about thirty minutes. Some seeds we must infer would pass into 
the intestines, where they might be retained for ten to twelve hours 
(see Chapter XXX I II.), which would be long enough, according to 
Gatke's views of bird-velocity, to enable them to be transported 
over a thousand miles of ocean. 

OSTEOMELES (Rosaceae). One of the most interesting cases of 
dispersal in recent times over the Pacific islands is that of O. 
anthyllidifolia. Of the ten known species of the genus, nine are 
confined to South America ; whilst the Pacific species, which is 
not recorded from America, has been found in Upper Burma, 
Japan, the Liukiu and Bonin Groups, Hawaii, Pitcairn Island, 



xxvi PLECTRONIA 355 

Mangaia, and Rarotonga. The remarkable distribution of the 
Pacific plant at once attracts attention. I was very familiar with 
it in Hawaii, where it forms one of the commonest bushes in open- 
wooded and thinly vegetated districts at elevations usually ranging 
from the coast to 3,000 feet. Its small, white, somewhat fleshy 
fruits would attract birds, and the hard pyrenes would be able to 
pass unharmed through a bird's digestive canal. It seems probable 
that, like Rhus semialata, this plant entered the Pacific Ocean from 
the north-west, taking the route by Japan and the Bonin Islands, 
and following the trend of the archipelagoes over Polynesia (see 
Bot. ChalL Exped., Introd. p. 18; Journ. Linn. Soc. Bot., vol. 28, 
1891, &c.). 

VlSCUM (Loranthaceae). A single species, V. articulatum, 
which has its home in Southern Asia, is found in most of the 
Pacific groups, such as Hawaii, Marquesas, Tahiti, Rarotonga, Fiji, 
&c. The dispersal of the genus by frugivorous birds is well known. 

PLECTRONIA (Rubiaceae). I have found it more convenient to 
place this genus here, although there are probably one or two 
species peculiar to Fiji. This genus of shrubs, which is spread 
over the warm regions of the Old World, is represented by two 
widely distributed species in Polynesia, Plectronia odorata (B. and 
H.) and P. barbata (B. and H.), the first alone extending to Hawaii. 
I was very familiar with P. odorata in Hawaii and was much in- 
terested in its mode of dispersal, since the species has also been 
found in Fiji, Tahiti, the Marquesas, and Pitcairn Island (Maiden). 
In one locality, where an old lava-field was partially covered by its 
bushes then in fruit, the doves were feeding greedily on the drupes, 
the " stones " of which, as well as the partially digested fruits, were 
to be seen in quantity in their excrement near a water-hole. The 
stones are very hard and about a third of an inch (8 mm.) in length, 
and are exceedingly well suited for transport by frugivorous 
birds. It was very probably to one of these species of Plectronia 
that Peale alluded when he wrote of the berries of a species of 
Canthium forming the principal food, on one of the Paumotu 
Islands, of Numenius tahitensis, a curlew that has its home in 
Alaska, migrating south in autumn to Hawaii, Tahiti, and the 
Paumotu Group (Wilson's Aves Hawaiienses). 

BOERHAAVIA (Nyctagineae). Two or three Asiatic species or 
this genus, B. diffusa, B. tetranda, &c., are spread all over the 
Pacific islands from the Fijis to the Paumotus and northward to 
Hawaii. Similar or allied species occur on the coral islands of the 
Indian Ocean, as on Diego Garcia and on Keeling Atoll. Though 

A A 2 



356 A NATURALIST IN THE PACIFIC CHAP. 

these plants have often been accidentally spread by man with his 
cultivated plants, it is probable that sea-birds have regularly aided 
in their dispersal. The fruits, on account of their small size and 
their glutinous sticky surfaces, are well suited for transport in a 
bird's feathers. Mr. Lister, as quoted by Hedley (from Proc. 
Zoolog. Soc., 1891), made an interesting note in this connection on 
one of the islands of the Phoenix Group, where he found a fruit of 
Boerhaavia tetrandra entangled in some of the down that had been 
preened by a booby (Sula piscatrix) out of its feathers whilst 
roosting in a clump of Tournefortia trees. 

POLYGONUM (Polygonaceae). This genus is represented by the 
cosmopolitan Polygonum glabrum, the only aquatic or semi-aquatic 
plant that is generally distributed in the Pacific islands. It occurs 
in fresh-water swamps and beside streams and ponds in Tahiti, 
Tonga, Fiji, Hawaii, &c., and was gathered by Banks and Solander 
when Captain Cook first visited Tahiti. That this plant has been 
distributed by geese, ducks, and waterfowl over the tropics of the 
globe can scarcely be doubted. In England I have found the 
nutlets of Polygonum convolvulus, P. persicaria, and P. aviculare 
in the stomachs of a wild duck and a curlew ; and they came 
frequently under my notice in the crops and intestines of different 
kinds of partridges and of wood-pigeons. Though most of the 
fruits were generally injured, a few of them were not uncommonly 
obtained in a sound condition. 

PlPTURUS (Urticaceae). This is a genus of small trees and 
shrubs found in the Mascarene Islands, Malaya, Australia, New 
Zealand, and throughout Polynesia. Besides P. albidus, which is 
confined to Hawaii and Tahiti, there are two Malayan species,. 
P. argenteus and P. velutinus, which are widely distributed over the 
islands of the South Pacific, extending to Tahiti and the Marquesas. 
The fleshy receptacle and small achenes of the compound fruit of 
Pipturus give it the appearance of a white immature strawberry, 
and as such it would be likely to attract frugivorous birds. Plants 
of this genus are included amongst the numerous plants from the 
bast of which the natives used to prepare their native cloth or from 
which they obtained the fibres for their fishing-lines. 

BCEHMERIA (Urticaceae). There is an Asiatic species widely 
spread in the South Pacific and another closely-allied species in 
Hawaii ; but I possess no data relating to the dispersal of the 
genus. The fruits are dry and consist of an achene in a persistent 
perianth. 

DlANELLA (Liliaceae). This is a genus of herbs, possessing 



xxvi DIANELLA 357 

often pretty blue berries, that extends over tropical Africa, tro- 
pical Asia, the Mascarene Islands, Malaya, Australia, and New 
Zealand, and is found in all the larger Pacific archipelagoes. 
Of the twelve species named in the Index Keivensis only two 
belong to America, occurring respectively in Cuba and Vene- 
zuela. There are two species in the islands of the tropical Pacific : 
(a) Dianella ensifolia, found in Hawaii and ranging over the 
Mascarene Islands, India, China, Malaya, and tropical Australia ; 
and (U) D. intermedia, recorded from most of the groups of the 
South Pacific (Fiji, Tonga, Rarotonga, Tahiti), and occurring also 
in Norfolk Island and New Zealand. These two plants occur in 
similar stations all over Polynesia, sometimes growing in the grassy 
plains on the dry side of an island, at other times extending up 
the thinly wooded mountain slopes and reaching the hill-crests 
some 2,000 or 3,000 feet above the sea. Their berries would readily 
attract birds ; and their seeds, about one-fifth of an inch (5 mm.) 
in size in the case of D. ensifolia, could be carried uninjured in the 
stomach and intestines of a bird. 



Summary. 

(1) A later period in the era of the general dispersal of 
Malayan plants over the Pacific is indicated by the genera 
that contain species found outside each group as well as species 
restricted to it. . 

(2) In this period the extremely variable or polymorphous 
species plays a conspicuous part, as represented in such genera as 
Alphitonia, Dodonaea, Metrosideros, Pisonia, and Wikstrcemia. 

(3) The first stage is displayed by a solitary widely-ranging 
species found over most of the Polynesian archipelagoes, and vary- 
ing independently in every group. 

(4) The next stage is shown where the polymorphous species, 
having done its work of distributing the genus, ceases to wander 
and settles down and " differentiates " in all the groups ; and the 
genus thus includes both peculiar and widely-ranging species in each 
group. Most of the genera possessing polymorphous species are in 
this stage. 

(5) The following stage is displayed by those genera like 
Elaeocarpus, Eugenia, and Peperomia, where peculiar species are 
especially developed in particular groups, and we get subcentres 
of distribution for the genus, that is to say, small gatherings of 



358 A NATURALIST IN THE PACIFIC CH. xxvi 

peculiar species. A few species, however, still keep up a connec- 
tion with neighbouring island-groups. Should this be severed we 
get the type of genus belonging to the earlier period of the 
Malayan era as described in the preceding chapter, a genus pos- 
sessing only peculiar species and destined, after ages of further 
isolation through the failure of the dispersing agencies, to give rise 
to a new generic type or types. 

(6) Frugivorous birds were chiefly active in dispersing these 
genera over the Pacific. Some of the genera possess seeds or 
" stones " of such a size that at first sight their transport by 
frugivorous birds to Hawaii seems improbable ; but, as in the case 
of Elaeocarpus, it is shown that this difficulty does not apply to all 
species of a genus, some of them having much smaller seeds 
or stones. 

(7) The close of the era of the general dispersal of Malayan 
plants over the Polynesian Islands is indicated by those genera 
that are represented more or less entirely by widely ranging 
species. Though such species may vary among the different 
groups, they rarely take the rank of polymorphous species, the 
agencies of dispersal being sufficiently active to check marked 
variations. 

(8) Several of the genera of this concluding stage, like Rhus, 
Viscum, and Plectronia, are known to be dispersed by frugivorous 
birds, whilst others, like Osteomeles and Dianella, are equally well 
suited for this mode of dispersal. 

(9) Distinct indications are afforded by the genera Rhus, 
Osteomeles, and Dianella that the Hawaiian Group has been often 
supplied with its plants directly from the Old World by the 
Asiatic mainland, whilst the groups of the South Pacific have 
received different species of the same genus by Malaya and 
tropical Australia. 



CHAPTER XXVII 

THE MALAYAN ERA OF THE NON-ENDEMIC GENERA OF 
FLOWERING PLANTS (continued) 

THE AGE OF LOCAL DISPERSAL 

Synopsis of the Chapter. 

HAWAII. (i) The Hawaiian residual genera, being those not found in 
either the Fijian or the Tahitian regions. The genera especially 
discussed are Osmanthus, Sicyos, Jacquemontia, Cuscuta, Rumex, 
Dracaena, Naias, Potamogeton ; and amongst others mentioned are 
Perrottetia and Embelia. 

(2) The Hawaiian genera found in Tahiti and not in Fiji. Very few, 
and illustrated by Byronia, Reynoldsia or Trevesia, Phyllostegia, and 
Pseudomorus, though it is likely that most of these will be sub- 
sequently discovered in Fiji. 

(3) The Hawaiian genera found in Fiji and not in Tahiti. Illustrated 
by Eurya, Gouania, Maba, Sideroxylon, Antidesma, Pleiosmilax, 
Ruppia. 

(4) The absentees from Hawaii. Illustrated amongst the orders by the 
Sterculiaceae (see text), the Meliaceae, the Rhizophoreas, the Melastoma- 
ceae, and the Coniferae, and amongst the genera by Trichospermum 
Loranthus, Stylocoryne, Ophiorrhiza, Alstonia, Hoya, Ficus ; and a 
great many others might be cited. 

TAHITI. (i) The Tahitian residual genera. Only six in number Crataeva, 
Buettneria, Berrya, Coriaria, Bidens, Lepinia. 

(2) The Tahitian genera found in Hawaii and not in Fiji. See above 
under (2). 

(3) The Tahitian genera found in Fiji and not in Hawaii, (a) Those 
possessing only species confined to the Tahitian region or to East 
Polynesia, of which Meryta, Ophiorrhiza, Alstonia, and Loranthus 
are examples. 

(b) Those possessing widely-ranging species besides, often, species con- 
fined to the Tahitian region, such as Grewia, Nelitris, Melastoma, Randia 
Geniostoma, Tabernaemontana, Fagraea, Bischoffia, Macaranga, and 
Ficus. The widely-ranging species is in many genera polymorphous. 



360 A NATURALIST IN THE PACIFIC CHAP. 

(4) The absentees from Tahiti. Amongst the orders are the Meliaceae, the 
Rhizophorese, and the Coniferae. Amongst the genera, usually those 
with "stones" or large seeds an inch in size, such as Canarium, 
Dracontomelon, Myristica, Sterculia, Veitchia, &c. Numerous other 
absent genera might be named. 

FIJI. The Fijian genera not found either in Tahiti or Hawaii. These 
genera compose about half the Fijian flora, being at least 160 in 
number. Those especially discussed here are the following : Hib- 
bertia, Cananga, Sterculia, Trichospermum, Micromelum, Canarium, 
Dracontomelon, Begonia, Geissois, Dolicholobium, Lindenia, Myr- 
mecodia, Hydnophyturn, Couthovia, Limnanthemum, Myristica, 
Elatostema, Ceratophyllum, Gnetum, Veitchia, Rhaphidophora, 
Lemna, Wolffia, Scirpodendron. The Coniferse are dealt with in 
Chapter XXIV. 

Note appended on Marsilea. 

HAVING completed our discussion of the general dispersal of 
tropical genera, chiefly Indo-Malayan, over the Pacific islands, we 
pass on now to consider the more restricted distribution of non- 
endemic genera over this region. Here as before we take Hawaii, 
Tahiti, and Fiji as the three centres of distribution ; and here also 
we deal with the flowering plants after excluding the orchids, the 
sedges, the grasses, the mountain-plants, and all plants introduced 
either by the aborigines or by white men. 

HAWAII. 

After excluding the endemic genera as well as those that 
are confined to the mountains, we find that this group possesses 
very few genera that do not occur in the Fijian and Tahitian 
regions, and fewer still that it owns in common with Tahiti to the 
exclusion of Fiji. On the other hand, we observe that Fiji 
possesses a great number of genera, mostly Asiatic in origin, that 
have not reached Hawaii, and in several cases are not known, from 
the Tahitian region. These contrasts might have been expected, 
since the Pacific islands have in later ages been mainly stocked 
from the Asiatic side of the Pacific, the principal route lying 
through the Fijian region. 

As far as the flora of the lower levels (below 4,000 feet) is con- 
cerned, Hawaii only possesses a portion of that which Fiji has 
derived from the Old World, chiefly through Malaya. Although, 
as will be shown below, there is a noticeable contribution from 
America, it is very far from counterbalancing the loss which 
the Hawaiian flora has sustained in comparison with Fiji through 



xxvn HAWAIIAN RESIDUAL GENERA 361 

the isolated position of the group. The want of variety, however, 
in the flora of the Hawaiian lower levels, which up to 4,000 
or 5,000 feet represent the islands of the less elevated Fijian 
region, is in a small degree compensated for by the development 
of new genera and new species and by the great number of 
individuals. Trees like Metrosideros polymorpha and Aleurites 
moluccana, that in the southern groups form only one of many 
contributors to the forests, rise suddenly into prominence in 
the northern archipelago and form entire forests. Pandanus 
odoratissimus largely composes extensive forests in the province of 
Puna in the large island of Hawaii, extending several miles inland 
and nearly 2,000 feet up the mountain slopes. 

The remarkable contrast between the Fijian flora, which is 
almost entirely tropical, and the Hawaiian flora, which on account 
of the great elevation of the islands is temperate as well as tropical, 
is brought into yet greater prominence when we look at it more 
closely and treat it numerically. The Hawaiian Group, it must be 
first observed, though possessing the same area as Fiji and present- 
ing a far greater variety of climatic conditions, has only two-thirds 
the number of genera of flowering plants (see Chapter XXL, 
Table B). Whilst at least 200 of the Fijian genera of indigenous 
plants (excluding the orchids and the grasses) are not found 
in Hawaii, only about 100 of the Hawaiian genera are absent from 
Fiji, and the two groups possess about 100 genera in common. 
When we look more closely at the hundred Hawaiian genera 
not found in Fiji, we find that about sixty represent endemic 
genera (thirty-seven) and non-endemic mountain-genera (twenty- 
two), which naturally are not to be found in Fiji, so that there 
remain but a small number of genera distinguishing the tropical 
flora of Hawaii from the Fijian flora. When we take from 
them a few that occur in the Tahitian region, there is left a 
very small residuum characteristic of Hawaii alone to the 
exclusion of the Fijian and Tahitian regions of the South Pacific. 

THE HAWAIIAN RESIDUAL GENERA. 

It is my purpose now to deal in an illustrative fashion with this 
Hawaiian residual flora which is composed, as above explained, of 
the non-endemic tropical genera that are not represented in the 
Fijian and Tahitian regions. Up to the present we have been 
dealing with the characters that the floras of Fiji, Tahiti, and 
Hawaii possess in common as far as tropical genera are concerned. 



362 A NATURALIST IN THE PACIFIC CHAP, 

We will now proceed to discuss their differences in this respect, and 
will begin with the residual Hawaiian flora. 

After eliminating two or three genera that will probably be 
found in Fiji, but including one or two others that are best treated 
under the endemic genera, about twenty-seven present themselves 
for our purpose. Nearly all of them possess only endemic species, 
and belong therefore to an age of dispersal that has passed away. 
These residual genera plainly indicate that although Hawaii largely 
received its flora during the age of general dispersal of Old World 
genera over the Pacific, it was at the same time independently 
stocked with plants from other sources. They include among 
others Cocculus (4), Cleome (i), Perrottetia (i), Mezoneuron (i), 
Ly thrum, Sicyos (8), Peucedanum (2), Campylotheca (12), Senecio 
(2), Lobelia (5), Embelia (i), Chrysophyllum (i), Rauwolfia (i), 
Nama (i), Osmanthus (i), Jacquemontia (i), Breweria (i), Cuscuta 
(i), Lycium (i), Sphacele (i), Phytolacca, Rumex (2), Urera (2), 
Pilea, Dracaena ( i ), Naias, Potamogeton. Those printed in italics are 
regarded as derived from America ; whilst the figures in brackets 
indicate the number of endemic species, nearly all of the genera 
except the five above indicated possessing only peculiar species, 
and these five (Lythrum, Phytolacca, Pilea, Naias, Potamogeton) 
are only represented by species found outside the group. 

American genera form a more conspicuous element than they 
do amongst the genera that have been generally dispersed over 
the Pacific, those exclusively American being fairly represented, 
making a third of the whole. We find, for instance, in the 
Hawaiian " Olomea," Perrottetia sandwicensis, a small tree that 
represents in the woods of all the islands the Perrottetias of 
Mexico and the Andes ; whilst with some of those genera that, like 
Sicyos and Urera, are at home in both the Old and New Worlds, 
we obtain indications of America being the source of the Hawaiian 
plants. A few genera again, like Lythrum and Phytolacca, are 
represented in Hawaii by American species. 

Plants with drupes, berries, or other fleshy fruits likely to 
attract frugivorous birds compose about a third of the total number 
of these residual genera, whilst fruits or seeds, that were in all 
probability originally brought entangled in a bird's feathers, are 
represented by Sicyos. Some of the genera with stone fruits, such 
as Osmanthus, to which belongs the Hawaiian Olive, present 
special difficulties on account of the size of the stone, in this case 
two-thirds of an inch in length. There are also a number of genera 
with large dry fruits and sometimes large seeds, of which the 



xxvii HAWAIIAN RESIDUAL GENERA 363 

method of dispersal is not easy to discover. Thus, Mezoneuron, a 
Leguminous genus with seeds an inch across (2*5 cm.), and 
Peucedanum, of the Umbelliferae, with mericarps half to three- 
quarters of an inch (1*2 to r8 cm.) in length, offer serious difficulties 
to the student of plant-dispersal. In discussing the difficulty con- 
nected with Mezoneuron (see Chapter XV.) he will keep in view the 
possibility that the original species may have been a littoral plant 
possessing seeds dispersed by the currents, seeds that lost their 
buoyancy when the plant established itself inland, just as is now 
taking place with Afzelia bijuga, a Leguminous littoral tree 
of Fiji (see Chapter XVIIA 

He will also find much to puzzle him in the mode of dispersal 
of the Hawaiian residual genera of the Convolvulaceae (Breweria, 
Jacquemontia, and Cuscuta) that possess only endemic species, 
and he will speculate as to the manner in which seeds that would 
seem to possess but little attraction for birds and have no capacity 
for transportation by the currents could ever have reached these 
islands, and he will ask himself why it is that the agencies of 
dispersal, whatever they are, have now ceased to be active. He 
will perhaps see a way out of his difficulties when he perceives that 
if isolation has led to the development of peculiar species in 
Hawaii, it has strangely enough in the case of the Myrsinaceous 
genus Embelia produced the same effect over the whole range of 
the genus, and that Hawaii has in this respect derived no advantage 
from being an oceanic group. According to Carl Mez, nearly all 
the ninety species of this Old World genus are restricted in their 
areas, whether continental or insular (" Myrsinaceae," Das Pflanzen- 
reich, 1902) ; and indeed we do not seem justified in assuming that 
the isolating influences in the case of this genus have been more 
effective in Hawaii in the mid-Pacific, or in Mauritius in the Indian 
Ocean, than they have been in continental regions like the Deccan 
and Nyassa Land, in all of which localities endemic species occur. 

The remarkable development of the Cucurbitaceous genus 
Sicyos, in Hawaii alone of all the tropical Pacific groups, will 
attract his attention, and he will find here another instance of that 
predominant principle in the distribution of Pacific plants, where 
in a widely- ranging genus we find one of its species covering most of 
its area, whilst the other species are more or less localised. He 
will wonder at the limitation to Hawaii of a genus like Dracaena, 
that is so well adapted for dispersal over the Pacific by frugivorous 
birds ; and in endeavouring to explain the presence in the 
Hawaiian forests of the gigantic Rumex, R. giganteus, he will 



364 A NATURALIST IN THE PACIFIC CHAP. 

remember that the small group of Tristan da Cunha, equally 
isolated in the South Atlantic, possesses an endemic species of the 
same genus. He will discover in the recognised dispersing 
agencies of wild ducks and other waterfowl an explanation of the 
occurrence in Hawaii of the aquatic genera Naias and Potamogeton ; 
but he will be puzzled at their restriction to this group alone of the 
three tropical Pacific archipelagoes here especially discussed. 

Amidst these various perplexities he will probably look with 
relief on the appearance of Phytolacca brachystachys, an endemic 
species of the American " pokeweeds " ; and he will feel grateful to 
the American botanists like Professor Weed when they tell him 
that in the United States crows, blackbirds, and other birds 
successfully disperse these plants, the seeds of which are some- 
times able to pass through the alimentary canal undigested. 

But by far the most significant lesson that the student of 
distribution will carry away from his study of the Hawaiian 
residual genera will be that which he learns from the genera 
Embelia and Naias. He perceives here that not only with a 
typical land-genus has specific differentiation occurred to much the 
same extent in the continental and insular localities of its range, 
but that even with a typical genus of submerged aquatic plants, 
where the conditions of existence are as uniform as they are varied 
in the case of land plants, the process of differentiation has pro- 
ceeded on the same broad lines in the interior of a continent and 
in an island in mid-ocean. 

The following notes on some of the residual genera refer more 
particularly to matters connected with distribution and dispersal. 

Osmanthus (Oleaceae). This genus, according to the Index 
Ke^vensis, contains six species localised in their several habitats 
of North America, Hawaii, Japan (two), Hongkong, and the 
Himalayas. Its representative in this group is the Hawaiian Olive, 
the Olea sandwicensis of Gray, a prevailing tree in the lower and 
middle woods (1,000 to 4,000 feet) of all the islands, which, like 
other Hawaiian plants, such as those of the genera Eurya and 
Antidesma, indicates that the group has been sometimes indepen- 
dently stocked from the regions of the northern hemisphere. The 
drupe of this tree contains a stone two-thirds of an inch (17 mm.) 
in length, and suitable for dispersal by frugivorous birds ; and 
birds have evidently distributed the tree all over the group. 
In fact Mr. Perkins in mentioning the favourite food of birds of 
the Hawaiian genus, Phaeornis, refers to the fruits of this tree as 
well as of the Opiko (Straussia) and of the Olapa (Cheirodendron). 



xxvn SICYOS 365 

When, however, we come to consider the feasibility of the stones 
of the genus having been thus originally carried to Hawaii either 
from Japan or from North America, we meet with the difficulty 
presented to us by other Hawaiian genera with stone-fruits, such 
as Elaeocarpus, or with berries containing large seeds, such as 
Sideroxylon. 

Sicyos (Cucurbitaceae). This genus comprises about thirty-five 
known species, of which three-fourths are confined to the New 
World, being mainly South American, whilst the remainder are 
restricted to Hawaii, with the exception of two species in the 
Galapagos Group and Norfolk Island, and a widely-ranging 
species, S. angulatus. The plant just named, the small fruits 
of which possess hooked spines, adapting them for dispersal in 
a bird's plumage, occurs in Africa, Australia, New Zealand, and 
America, but has only been recorded in the Pacific islands from 
the Kermadec Group. 

North America was probably the home of the original 
Hawaiian species. Hillebrand describes eight species, of which 
five are not found in more than one island, whilst one species is 
spread over most of the islands. The fruits vary much in size, and 
only in a couple of species do they now possess any fitness for 
attaching themselves to plumage, some of them being pubescent or 
even glabrate, so that deterioration in the capacity for dispersal has 
here taken place. Their size is usually a quarter to half an inch 
(6 12 mm.) ; but it is noteworthy that the species with the largest 
fruit (Sicyos cucumerinus, one to two inches, or 25 to 50 mm.) is 
the species most widely dispersed over the group. This appears to 
indicate that there is some other means of inter-island dispersal in 
this archipelago than by attachment to birds' plumage. The 
isolation of the genus in Hawaii from the rest of the world is, 
however, complete, since all the species are endemic ; and when, 
therefore, we come to ask how Sicyos angulatus, that has been 
dispersed in the recent era over America, Australia, and New 
Zealand, is not found in these islands, we are brought face to face 
with the ever-recurring difficulty, the suspension in later times of 
the agency of dispersal in the tropical North Pacific. 

Jacquemontia (Convolvulaceae). This genus, which is chiefly 
American, is represented in Hawaii by a peculiar species, J. sand- 
wicensis. This species grows occasionally on the sandy beaches 
associated with Heliotropium anomalum and Tribulus cistoides ; 
but it is most at home on rocky ground and on old lava-flows near 
the sea-border, making its abode often in the pockets of black 



366 A .NATURALIST IN THE PACIFIC CHAP. 

sand produced by the disintegration of the lava. Its small seeds 
sink in sea-water even after prolonged drying ; and it can perhaps 
be supposed that the original seeds were brought from North 
America in the crevices of a drifting log. According to Ridley, 
Fernando Noronha possesses a peculiar species also growing near 
the sea ; and it may be that the drifting log has here been the 
agent also : but in neither case would this explanation account for 
the endemic character of the species. 

Cuscuta (Convolvulaceae). It would seem that with the ex- 
ception of Hawaii, where an endemic species, C. sandwichiana, 
occurs, no other oceanic group in the globe possesses a peculiar 
species of the Dodders. With the exception of an endemic 
species in New Zealand, and an introduced species in Fiji which is 
found usually near the gardens of the white residents on Viti Levu, 
the genus takes but little part in the Pacific floras. The Hawaiian 
species is a characteristic beach-plant growing on Ipomea pes 
caprae, Scaevola Kcenigii, Tribulus cistoides, and on other plants 
that find a permanent or a temporary abode on the beaches. We 
learn from Ridley and Moseley that Cuscuta americana in 
Fernando Noronha finds its host also in Ipomea pes caprae. Since 
the seeds of the Hawaiian plant and of the introduced Fijian 
species possess no buoyancy, even after drying for years, we cannot 
look to the agency of the current unless we call the drifting log to 
our assistance, and in that case the endemic character of the 
Hawaiian species would present the difficulty already alluded to in 
the case of Jacquemontia. The seeds of the Hawaiian plant are 
about one-twelfth of an inch (2 mm.) in diameter, and as far as size is 
concerned they might have been transported in a bird's stomach ; 
but, on account of the rapidity with which the seeds of the genus 
absorb moisture and swell up, it is most unlikely that they would 
escape injury. This is one of the several difficulties in plant- 
dispersal which New Zealand and Hawaii share in common. 
Further remarks on the germination of the Hawaiian species are 
made in Note 69. 

Rumex (Polygonaceae). Hawaii possesses two peculiar species 
of Rumex, a genus not recorded from any other of the Polynesian 
groups. One of these species, R. giganteus, is a very remarkable plant, 
growing to a height of thirty or forty feet when supported by trees. 
It is noteworthy that the small group of Tristan da Cunha in the 
South Atlantic possesses a species, R. frutescens, confined to those 
islands (Bot. Chall. Exped., ii. 154). Both Hawaii and Tristan da 
Cunha lie in mid-ocean, cut off from the nearest continent by some 



xxvn NAIAS 3 6 7 

1, 800 or 2,000 miles of sea; and we may have to choose between 
the bird and the current in selecting the agency concerned with 
the transportation of the original seeds ; or perhaps they have 
co-operated. Birds could disperse the nutlets of Rumex as readily 
as they do those of Polygonum, and I have found these fruits at 
times in the stomachs of partridges. On the other hand, Rumex 
fruits occur amongst the drift stranded on beaches in England and 
in Scandinavia ; and, as indicated by the observations of Sernander 
and myself in these two localities, they float through the winter in 
ponds and rivers, germinating afloat in the spring. The nutlets 
sink, but they owe their buoyancy to the persistent perianth. In 
my sea-water experiments the fruits of Rumex hydrolapathum and 
R. conglomeratum were still afloat after from six to twelve months' 
immersion, and their seeds subsequently germinated. It is quite 
possible, therefore, that currents can carry these fruits unharmed 
to oceanic island-groups like Hawaii and Tristan da Cunha. 

Dracana (Liliaceae). This Old World genus, which on account 
of its berries is eminently suited for dispersal by frugivorous birds, 
is represented in Polynesia by a solitary species (D. aurea) peculiar 
to the Hawaiian Group. Attaining a height of twenty to twenty-five 
feet, it often forms a striking feature in the vegetation of the open 
wooded regions up to altitudes of 3,000 feet. I found it growing 
in abundance in the large island of Hawaii between Waimanu and 
Waipio, and on the northern slopes of Hualalai. It grows in a 
variety of stations, and I came upon it once in the broken-down 
caverns of an old lava-flow that were frequented by pigeons which 
no doubt brought the seeds. Its conspicuous yellow berries have 
hard rounded seeds a quarter of an inch (6 mm.) across and weighing 
two to three grains when dry, which would probably withstand injury 
in a bird's stomach, the minute embryo being protected by a very 
tough albumen. Neither the entire berry nor the seed could be 
transported by currents, the last sinking even after drying for six 
years. 

Naias (Naiadaceae). If we except New Caledonia, where two 
or three species have been found, Hawaii is the only island-group 
in the tropical Pacific from which this interesting world-ranging 
genus of submerged aquatic plants has been recorded. Chamisso, 
the celebrated naturalist of Kotzebue's expedition, collected Naias 
marina in Oahu in the early part of last century ; but apparently 
it did not come under Hillebrand's observation in the group. 
However, in 1897 I found it in another locality, namely, just within 
the mouth of the Waipio, a river on the north-west side of the 



368 A NATURALIST IN THE PACIFIC CHAR 

island of Hawaii. The mature fruits of this genus have never been 
experimented on by me ', but there is nothing in the structure of 
the fruits to indicate that they have any buoyancy, or to show that 
they differ in this respect from the fruits of other completely 
submerged aquatic plants like Ceratophyllum, Ruppia, and some 
of the Potamogetons. It is to ducks and other waterfowl that we 
must attribute the dispersal of this and the other genera just 
mentioned over wide tracts of ocean, a subject dealt with in dis- 
cussing those plants. 

The Hawaiian Group probably represents the most isolated 
locality occupied by this genus, since none of the other islands from 
which species have been recorded, such as New Caledonia, Mauritius, 
and Bourbon, are so far removed from continental regions. The 
source of the Hawaiian form of Naias marina lies evidently on the 
Asiatic side of the Pacific, since it is referred by Mr. Rendle to the 
variety " angustifolia," an Asiatic plant found also in the island of 
Bourbon and in West Australia, but not recorded from the New 
World. The important little monograph of the genus by Mr. Rendle 
(" Naiadaceae," in Engler's Das Pflanzenreich, 1901) is full of sugges- 
tiveness for the student of plant-distribution. His interest is excited 
when he discovers that one of the most typical genera of aquatic 
plants displays the same principle of differentiation at work that is 
so well illustrated by many of the land genera of the Pacific islands. 
I refer to the principle implied in the existence of a widely-ranging 
genus comprising " a polymorphic species occurring over almost 
the whole area of the genus," as well as a number of less widely 
distributed species, most of which have " restricted areas and fall 
for the most part into small geographical groups." I have just 
been quoting Mr. Rendle's description of the distribution of Naias, 
the " polymorphic " species concerned being N. marina ; but it need 
scarcely be remarked that it would apply just as well to several of 
the land genera dealt with in the previous chapter (XXVI.), such as 
Alphitonia, Metrosideros, Pisonia, &c. 

Although there is such a contrast in the degree of uniformity of 
their life-conditions between land and water plants, a strictly 
aquatic plant being but slightly affected by changes in the physical 
conditions that are accompanied by a complete transformation in 
the character of the terrestrial vegetation, yet and this is the 
important point we find the same principle of differentiation at 
work with both land and water plants. If one wished to produce 
proof of the contention that the production of new species is largely 
independent of external conditions, one could not do better than 



xxvn POTAMOGETON 369 

take the cases of Elaeocarpus, Metrosideros, and Naias. In all 
cases we see a widely-ranging polymorphous species settling down 
and " differentiating " in particular localities or regions, and forming 
subcentres for the distribution of the genus. 

Potamogeton (Potameae). Though well suited for dispersal by 
waterfowl, the Potamogetons have been recorded from the 
Hawaiian and Marianne Islands alone among the tropical groups 
of the open Pacific. The genus, though not so well represented in 
insular floras as we might have expected, is still not infrequently 
to be found. Widely-ranging species have been observed in the 
Azores, Madeira, and the Canaries in the Atlantic, as well as in 
Hawaii in the Pacific ; whilst species have been recorded that are 
peculiar to Martinique, the Mascarene Islands, and to the Marianne 
Group. Hillebrand gives for Hawaii, Potamogeton fluitans, a plant 
of the Old and New Worlds, and P. pauciflorus, a North American 
species ; whilst in the Index Kewensis a peculiar species, 
P. owaihiensis of Chamisso (which is, however, regarded by 
Hillebrand as a form of P. fluitans), is also accredited to the 
group. Owing, however, to the paucity of streams and rivers this 
genus takes no prominent part in the Hawaiian flora, and the 
species seem to have been recorded alone from Oahu. As they 
were discovered by Chamisso in the early part of last century they 
are in all probability truly indigenous in Hawaii, even if none are 
peculiar to the group. 

That ducks and similar birds are the agents in carrying the 
seeds of Potamogeton to oceanic islands cannot be doubted. 
About twelve years ago I examined the stomachs and intestines of 
thirteen wild ducks obtained in the London market. Three of 
them contained in all forty-one Potamogeton seeds, or rather 
"stones," most of which subsequently germinated in water. In one 
of my experiments, carried out in the month of December, I fed 
a domestic duck with the fruits of Potamogeton natans. They 
appeared in quantity in the droppings, for the most part divested 
of their soft coverings, but otherwise uninjured. Sixty per cent, 
germinated in the following spring ; whilst of those left in the 
vessel, from which the duck had been fed, only one per cent, 
germinated in the next spring, and another year elapsed before any 
number did so. These results were published in Science Gossip 
for September, 1894. 

One often reads in books of travel interesting remarks bear- 
ing indirectly on the dispersal of the Potamogetons. Thus, when 
Sir Joseph Hooker (then Dr. Hooker) noted in his Himalayan 
VOL. II B B 



370 A NATURALIST IN THE PACIFIC CHAP. 

Journals the occurrence of P. natans in the Neongong Lake in the 
Himalayas, and the presence of coots, he most probably mentioned 
the bird that brought the plants, coots being active distributors of 
the seeds of water plants. It is of importance to remember that 
(as shown in my experiment on the duck) seeds of water-plants are 
voided in a condition peculiarly favourable to early germination. 
Ducks, coots, and other water birds might often be characterised as 
" travelling germinators." My experiment showed that seven to 
eight hours at least were occupied by Potamogeton nutlets in 
passing through the digestive canal of a duck, and that probably 
nine or ten hours would be required after an average full meaL 
But this does not represent the possible maximum period, since the 
bared " stone " may remain in the gizzard for a long time with 
ordinary gravel. Most of the Potamogeton fruits found by me in 
wild ducks were obtained from the gizzard, where they were mixed 
with gravel and other hard seeds or seedvessels, as described in 
Chapter XXXIII. Such fruits afterwards germinated. With 
regard to the chances, therefore, of the fruits of Potamogeton being 
carried by a bird without injury across an ocean, we may infer that, 
whether they are retained in its body for only ten hours or for as 
long as three or four days, they will preserve in some cases their 
germinating power. 



HAWAIIAN GENERA FOUND IN TAHITI TO THE EXCLUSION 

OF FIJI. 

Taking only the genera that are strictly indigenous, and 
excluding therefore all those introduced by the aborigines, the 
number available for establishing an independent connection 
between the Hawaiian and Tahitian regions is exceedingly few. 
Amongst the Hawaiian shore-plants not found in Fiji proper but 
occurring in the Tahitian region are Heliotropium anomalum and 
Sesuvium portulacastrum. The last-named, however, has been 
recorded from Tonga, which lies within the Fijian area ; whilst the 
first will probably be found in the same region. Amongst the 
Hawaiian and Tahitian mountain genera not recorded from Fiji 
proper are Nertera, Vaccinium, Cyathodes, and Luzula. As is 
pointed out in Chapter XXIIL, the absence of these genera from 
Fiji is connected with the relatively low elevation of those islands, 
though it is quite possible that one or more of them may yet be 
found on the highest summits of Fiji ; and indeed Nertera depressa 



xxvii BYRONIA 371 

and Vaccinium have been discovered in the more elevated uplands 
of Savaii in Samoa. 

After removing the littoral plants and the mountain genera, 
there are probably not more than half a dozen inland genera that 
connect the Hawaiian lowlands with the Tahitian region to the 
exclusion of the Fijian Group ; and Byronia (Ilicineae), Reynoldsia 
or Trevesia (Araliaceae), Phyllostegia (Labiatae), and Pseudomorus 
(Urticaceae) may be taken as examples. Of these, Pseudomorus, 
which has a small drupaceous fruit suitable for dispersal by 
frugivorous birds, has been recorded from New Caledonia, and not 
improbably it exists in the Fijian area ; and the same may be 
postulated of Reynoldsia, which is discussed in a later page, since it 
has been found in Samoa. We may almost form the same opinion 
of Byronia, since it exists in Australia. This genus of small trees 
contains only three known species, one in Australia, one in Tahiti, 
and one in Hawaii. Its fleshy drupes, about a third of an inch 
(8 mm.) in size, would attract birds, and their numerous cartila- 
ginous pyrenes would probably pass unharmed through a bird's 
alimentary canal. Phyllostegia, a Labiate genus with fleshy 
nucules that might attract birds, is, with the exception of a 
solitary Tahitian species, entirely confined to Hawaii (see Chapter 
XXII.). 

From these data it may be inferred that the interchange of 
plants between the regions of Hawaii and Tahiti to the exclusion 
of Fiji has been very slight. The facts of distribution are just 
such as we might look for in the case of a general dispersal over 
the oceanic groups of the tropical Pacific, with the altitudes of the 
islands playing a determining part. In this general dispersal 
Hawaii has shared ; and except in the case of Phyllostegia it is 
evident that this group has kept nearly all it received and has 
distributed but little. 



HAWAIIAN GENERA FOUND IN FIJI TO THE EXCLUSION OF 

TAHITI. 

We shall be able to throw further light on the floral history of 
Hawaii by discussing the few tropical genera, not a score in all, 
that it possesses in common with Fiji to the exclusion of the 
Tahitian region. The following genera offer themselves for treat- 
ment : Eurya (Ternstrcemiaceae), Gouania (Rhamnaceae), Maba 
(Ebenaceae), Sideroxylon (Sapotaceae), Antidesma (Euphorbiaceae), 
Pleiosmilax (Smilaceae), and Ruppia (Potameae). 

B B 2 



372 A NATURALIST IN THE PACIFIC CHAP. 

These seven genera, which with the exception of Ruppia, an 
aquatic genus, are only represented in Hawaii by peculiar species, 
possess in all cases, except Gouania and the last-named genus, 
drupaceous or baccate fruits likely to attract frugivorous birds. 
Two of them, Eurya and Antidesma, have their home in Malaya 
and in the Asiatic continent ; three of them, Gouania, Maba, and 
Sideroxylon, are found on both the Asiatic and the American sides 
of the Pacific Ocean ; whilst Pleiosmilax should, strictly speaking, 
be regarded as a Polynesian subgenus of Smilax, a world-ranging 
genus ; and Ruppia is a cosmopolitan brackish- and salt-water 
genus. 

It is highly probable that Fiji received almost all these genera 
from the Old World through Malaya ; and in some cases the 
resemblance between the Malayan and the Fijian species is so close 
that, as in Gouania, Dr. Seemann questioned if they were not forms 
of the same species. In other instances, as with Maba, we find a 
widely-ranging Asiatic and Malayan species, like Maba buxifolia, 
extending into Western Polynesia, where it is accompanied by 
other species peculiar to that region. But if the genera were able 
subsequently to extend their range thence to Hawaii, it is difficult 
to understand why they have not reached the Tahitian region. It 
is therefore likely that Hawaii received most of these genera by a 
northern route and not through the South Pacific ; and it is 
legitimate to suppose that when Old World genera like Eurya 
and Antidesma occur in north-eastern Asia, as in Japan and in 
the neighbouring mainland, Hawaii received the genus by that 
route. In the case of Eurya it is noteworthy that Fijian and 
Samoan forms, regarded by Seemann and Gray as distinct species, 
are viewed by Reinecke as forms of E. japonica, an extremely 
variable species found in Japan. With genera like Gouania and 
Maba, that exist on both sides of the Pacific, it is possible that they 
may have originally reached Hawaii from America. 

A noticeable feature in the instance of genera like Maba and 
Sideroxylon is that hard seeds or pyrenes | to I inch (18 to 25 mm.) 
in length have seemingly been transported by frugivorous birds 
across the ocean to Hawaii. This at first sight seems improbable; 
but it is known that fruit-pigeons can swallow very large drupes, as 
in the case of those of Canarium, Dracontomelon, and Elseocarpus, 
afterwards disgorging the " stones." They have carried such stones to 
Fiji, across some 500 or 600 miles of ocean ; and unless we impute a 
continental origin to Hawaii we must assume that in some cases, as 
with Elaeocarpus, Maba, and Sideroxylon, they have been able to 



xxvii SAPOTACE^E 373 

transport these large stones or pyrenes to that group. The extent 
of ocean to be crossed is no doubt much greater, but this area of 
the Pacific is not without some small half-way groups that would 
serve as resting-places. 

That fruits of the order Sapotaceae are much appreciated 
by fruit-pigeons is already known. We learn from Kirk that 
the fruits of Sideroxylon costatum (Sapota costata) are a favourite 
food of the New Zealand fruit-pigeon, the fruits, about an inch 
long, containing three hard crescentic bony seeds nearly as long as 
the fruit. The natives of Vanua Levu informed me that a Fijian 
species of Sideroxylon with hard seeds about an inch long was 
much appreciated on account of its fruit by the pigeons. I found 
the hard, sound seeds of a species of Sapota, two-thirds of an inch 
(or 1 6 mm.) in size, in the crop of a Fijian fruit-pigeon. The 
similarly large seeds of a species of Achras were identified by Mr. 
Charles Moore, of Sydney, amongst a collection of seeds, &c., 
found by me in the crops of fruit-pigeons shot in the Solomon 
Islands (Guppy's Solomon Islands, p. 293). It may be added that 
the difficulty concerned with Sideroxylon in Hawaii is the difficulty 
concerned with other large-seeded Sapotaceous trees in Fiji and 
New Zealand, and the same explanation must be applied to all. 
Some further remarks on the Sapotaceae in the Pacific are given 
below. 

The mode of dispersal of some of these genera is illustrated 
in other regions. The berries of Pleiosmilax, a subgenus of 
Smilax, are well suited for aiding the dispersal of the genus by 
frugivorous birds ; and we learn from Prof. Barrows (Weed, p. 42) 
that in the United States crows feed on the fruits of Smilax 
rotundifolia and disperse the seeds. On the other hand, it is not at 
first sight easy to understand how a genus like Gouania has been 
distributed over the tropics of the globe, since it possesses dry 
capsular fruits about half an inch across, separating into three 
woody cocci that appear most unlikely to attract birds. The same 
difficulty exists, however, with other dry-fruited widely-ranging 
genera like Alphitonia and with many of the Euphorbiacese. 

Amongst these genera found in Hawaii and Fiji to the 
exclusion of Tahiti we can at times detect indications of the 
operations of a polymorphous species as described in Chapter 
XXVI. , when a widely-ranging highly variable species is associated 
in some groups with peculiar species. We see some evidence of this 
in the genera Gouania, Maba, and Eurya, alluded to on a previous 
page. (See also Bot. Chall. Exped., iii. 134, under "Gouania.") 



374 A NATURALIST IN THE PACIFIC CHAP. 

One of the mysteries of the Pacific is concerned with the dis- 
tribution of the Sapotaceae, the dispersal of which by frugivorous 
birds has been dealt with above. It is strange that whilst the 
order seems to have found a rendezvous in Tonga, no one except 
Home appears to have recorded any of the genera from Samoa. 
They are fairly well represented in Fiji; but it is in Tonga that we 
especially note the gathering together of several Sapotaceous trees 
with large heavy seeds, of the genera Bassia, Mimusops, and 
Sideroxylon. Besides owning one or two species of Sideroxylon 
in common with Fiji (Burkill), this small group possesses Bassia 
amicorum and Mimusops kauki, both of which were found there by 
Forster at the time of Cook's visit. In a list of a small collection 
of plants made by him in Upolu in the Samoan Group about 1879, 
Home includes two species of Sideroxylon ( Year in Fiji, p. 286) ; 
and according to Seemann there is a Sapotaceous tree in Wallis 
Island. A species of Bassia exists in Rarotonga, the seeds of 
which, from Mr. Cheeseman's description of the fruit, must be 
almost an inch long. Drake del Castillo refers to an endemic 
Tahitian tree near Mimusops ; but its fruit was not known to 
him. 

As already indicated, the difficulties connected with the 
Sapotaceae affect the whole Pacific from New Zealand north to 
Hawaii and from Fiji east to Tahiti. We are driven to appeal to 
the agency of frugivorous birds, at least in the case of Sideroxylon, 
since some fruits experimented on by me in Fiji sank at once or in 
a day or two, the seeds having no buoyancy. That birds actually 
disperse the seeds of this and other genera of the order has been 
already pointed out, yet it is possible that currents have at times 
aided in the dispersal of some of the genera. This is indicated 
by the circumstance that, as we learn from Schirnper, some 
Sapotaceous trees are to be included in the Malayan strand-flora, 
namely, Sideroxylon ferrugineum, Mimusops kauki, and M. littoralis, 
all occurring as well on the Asiatic mainland, the first growing also 
in the Liukiu Islands, and the last in the Andaman and Nicobar 
Groups. 

Ruppia maritima (Potamese). This cosmopolitan aquatic 
plant has only been recorded in Polynesia from Hawaii, Samoa, 
and Fiji. It had not been collected in Fiji before my dis- 
covery of it in 1897. Amongst other oceanic islands where 
it occurs may be mentioned the Bermudas, where, according to 
Hemsley, it exists as an indigenous plant in the lagoons. 
Chamisso first noticed it in Hawaii, and Hillebrand remarks that 



xxvn THE ABSENTEES FROM HAWAII 375 

it grows in shallow waters along the coasts. Amongst other 
localities where I noticed it in this group may be mentioned the 
north-west coast of the large island of Hawaii between Kailua and 
Keahole Point. Here in 1896 it was thriving in brackish- water 
ponds, with Sesuvium portulacastrum growing at the edges. 
Reinecke observes that it occurs in similar ponds in Samoa. 
In 1897 I found it in abundance in the Rewa estuary (Fiji), both 
in the creeks and in the main channel. In the following year 
it was not to be found in this locality, a circumstance noticed 
both by the natives and by resident whites. The fruits of this 
plant possess no floating power, sinking, even after prolonged 
drying, in a few hours. It is to ducks and to birds of similar habit 
that its dispersal must be attributed. 

THE ABSENTEES FROM HAWAII. 

It has been before remarked that of the 330 or 340 genera 
of flowering-plants recorded from Fiji some 200 are not known in 
Hawaii. It will only be possible to deal with the absent genera in 
a cursory manner ; but enough will be done to show that we 
are face to face here with a multitude of the seeming inconsis- 
tencies that so often beset the study of plant-distribution. 

A host of plants are unrepresented in Hawaii, of which it may 
be said that their seeds or fruits are not less suited for being 
carried across the Pacific than those of many that are now in that 
group. On the other hand, a number of genera exist there 
which we should never expect to have been endowed with the 
capacity, and to have received the opportunity, of crossing nearly 
2,000 miles of ocean. Yet perhaps when Nature acts in a whole- 
sale fashion and excludes entire orders we may be able to perceive 
the dim outlines of a principle of exclusion at work. But even 
here much caution and some clearing of the ground are needed. 

For example, having regard to the several modes of dispersal 
possessed by the great variety of fruits and seeds of the Stercu- 
liacese, it would be almost meaningless to remark that the order 
so well represented in Fiji is practically non-existent in Hawaii as 
far as truly indigenous plants are concerned. It is true that 
two species of Waltheria are here present, but one of them 
W. americana, is a weed probably introduced by the aborigines 
whilst the other, W. pyrolaefolia, recorded from a solitary locality 
by the Wilkes Expedition, has seemingly never been found since. 
From the standpoint of dispersal the genera Sterculia, Heritiera, 



376 A NATURALIST IN THE PACIFIC CHAP. 

Kleinhovia, Melochia, and Commersonia, that are represented in 
Fiji but not in Hawaii, cannot be discussed together. With 
Sterculia is concerned the dispersal by birds of large seeds, an inch 
in length, not particularly well protected, the genus being confined 
to Fiji alone of all the oceanic Pacific groups. Heritiera is only 
represented by a littoral species, the large fruits of which are 
carried great distances by the currents ; and no other agency 
of dispersal is here possible. The last three genera are distributed 
over the South Pacific, their relatively small seeds being probably 
in the main dispersed by granivorous birds ; whilst the setose fruits 
of Commersonia may have been at times transported in birds' 
plumage. 

It is more legitimate, perhaps, to speak collectively of the 
orders Meliaceae and Melastomaceae as absent from Hawaii ; but 
even here the issue raised is one concerned rather with oppor- 
tunities than with capacities for dispersal. Several years ago, 
M. Casimir de Candolle remarked that " it is hardly credible 
that the Meliaceae should be entirely absent from the Sandwich 
archipelago" (Trans. Linn. Soc. Bot. } vol. i. 1880). Yet it can 
scarcely be said that this is a matter connected with means of 
dispersal. Amongst the Meliaceous genera represented in Fiji, 
Vavaea and Aglaia have a berry, Melia has a drupe, and Dysoxy- 
lum has a capsule. So again with the Melastomaceae ; it possesses 
at least six genera in Fiji, two in Tahiti, and none in Hawaii. 
Whilst the genera Melastoma and Medinilla have baccate fruits 
with minute seeds, Astronia has a capsule with similar seeds, and 
Memecylon has a single-seeded berry. Since, however, minute 
seeds are most typical of the order, those of Melastoma denti- 
culatum being about one-fiftieth of an inch or *5 mm. in size, 
it would seem that this character has not aided its dispersal in the 
Pacific so far as Hawaii is concerned. From the circumstance that 
berries, drupes, and capsules are represented in these two Fijian 
orders we may form the opinion that their non-occurrence in 
Hawaii is due not so much to lack of capacities for dispersal as to 
failure of opportunities. 

This opinion is much strengthened when we come to deal with 
the individual genera, where the predominant cause of the absence 
of so many Fijian genera from Hawaii is concerned with the 
failure of the agencies of dispersal. It is not a question of a 
difference in size between the groups, since, although the surface- 
area is approximately the same in both groups, Hawaii possesses 
only two- thirds of the number of genera occurring in Fiji. It is not 



xxvii THE ABSENTEES FROM HAWAII 377 

a question of capacity for dispersal across an ocean, since birds 
have transported across the Pacific to Hawaii the " stones " and 
large seeds of genera like Elaeocarpus and Sideroxylon, a feat that 
would have been deemed impossible by many botanists. It is no 
lack of capacity for dispersal that has excluded Loranthus from 
Hawaii and has admitted Viscum. 

Few genera, indeed, would seem to be better fitted for dispersal 
by frugivorous birds in the Pacific than that of Ficus. Its fruits 
are known to be eaten by birds all over the area of the genus ; and 
we find the species distributed over the South Pacific from Fiji to 
Tahiti, but they are quite absent from Hawaii. This is the more 
remarkable on account of the occurrence of a species of Ficus 
resembling a banyan in Fanning Island about 900 miles south 
of the group (Bot. ChalL Exped., iii. 116, 194), and because the 
Hawaiian Islands possess the Meliphagidse or Honey-eaters, 
which are widely distributed in Polynesia and are known to feed 
on these fruits a matter further discussed in my treatment of Ficus 
later on in this chapter. 

Of several Rubiaceous genera with fleshy fruits that are repre- 
sented both in Fiji and Tahiti, such as Stylocoryne and others, and 
of those Rubiaceous genera with minute seeds that, like Ophiorrhiza, 
are distributed over the South Pacific, none occur in Hawaii. Here we 
find represented other genera of the order, like Gardenia, Plectronia, 
and Coprosma, that do not appear to be better fitted for dispersal 
by frugivorous birds than many of the genera not existing there. 
If birds have carried to Hawaii in their plumage the fruits of 
Pisonia and Sicyos, it cannot be merely a question of capacity for 
dispersal that is concerned with the restriction to the South Pacific 
of genera with hairy seeds, such as Trichospermum, Alstonia, and 
Hoy a. 

It is unnecessary to dwell longer here on the subject of the 
Hawaiian absentee-genera, since many of the absent plants will be 
discussed when dealing with the peculiarities of the Fijian flora. 
The data there given all go to show that mere lack of capacity for 
dispersal over the Pacific often counts for little in supplying us with 
an explanation of the absence of so many likely genera from the 
' Hawaiian flora. Hawaii has only been stocked with those genera 
common to Fiji and Tahiti that could have reached it during each 
age of general dispersal over the Pacific. In later eras the dispers- 
ing agencies have been mainly active in the tropical South Pacific ; 
and thus it is that, as will be pointed out in a later page, the bulk 
of the plants of the Malayan era are confined to the region between 



378 A NATURALIST IN THE PACIFIC CHAP. 

Fiji and Tahiti. In a still later period the dispersing agencies have 
confined their operations mainly to Western Polynesia and the last 
immigrant genera have not reached beyond the Fijian region. 

The whole story of plant-life in the tropical Pacific is bound up 
with these successive stages of decreasing activity of the dispersing 
agencies. The story of plant-distribution in this region is well 
illustrated in its earlier phases of general dispersion in the floral 
history of Hawaii, in its later phase by those Asiatic genera that 
have only crossed the South Pacific to Tahiti, and in its last phase 
by those genera that have never extended beyond the groups of 
the Fijian area. The area of active dispersion, that first comprised 
the whole of the tropical Pacific, was afterwards restricted to the 
South Pacific, and finally to the western portion of that area. It 
can scarcely be doubted that these successive stages in the con- 
traction of the area of active dispersion of plants in the Pacific were 
accompanied by a corresponding diminution in the general distribu- 
tion of birds in the same ocean, to which it stood in the relation of 
an effect to a cause. 

TAHITI. 

The peculiarities of the Tahitian flora as compared with Hawaii 
and Fiji may be discussed by treating first those genera that are 
alone represented in Tahiti, the " residual " genera ; then those that 
it possesses in common first with Hawaii and then with Fiji ; and 
lastly by pointing out the more noticeable gaps in the flora. By 
Tahiti is typically signified the whole Tahitian region, which 
includes the Austral and Cook Groups, the Society Islands, the 
Paumotus, and the Marquesas. 



THE TAHITIAN RESIDUAL GENERA. 

The non-endemic genera occurring alone in the Tahitian region 
and not found either in Hawaii or in one or other of the three 
groups of the Fijian region (Fiji, Tonga, Samoa) are not more than 
half a dozen. These six genera are exceedingly interesting ; but 
since each tells a different story and gives its own independent 
indication they cannot be treated in a collective sense. Nor are 
they all to be regarded as anomalies in plant-distribution, since 
with a single exception there is scarcely one concerning which it is 
not in some way possible to give an explanation of its isolation 
without coming into conflict with the principles of plant-dispersal. 
The exception is Lepinia tahitensis, which, without presenting any 



xxvn LEPINIA TAHITENSIS 379 

very evident capacity for dispersal, has not been recorded from any 
other localities in the Pacific than the far-separated Solomon and 
Tahitian Groups. There is a suspicion that, as in the case of the 
residual genera of Hawaii, America may have contributed some of 
the original plants, since three of the genera, Buttneria, Coriaria, 
and Bidens, occur in that continent, and in the case of Coriaria 
Tahiti possesses a species found in South America as well as in 
New Zealand. 

One of the trees in question is Crataeva religiosa, an Asiatic 
species, which may be placed among a group of trees, including 
Cananga odorata and Fagraea Berteriana, which, whilst they are 
much esteemed by the inhabitants of the South Pacific for their fruits 
or their flowers, and are often- planted in and around their villages, 
possess fruits that attract birds, and in the case of Cananga are 
known to be dispersed by fruit-pigeons. Probably the aborigines 
and the birds have worked together in the distribution of these 
trees. 

The genera Buttneria of the Sterculiaceae and Berrya of the 
Tiliaceae are represented in this region by species that must owe 
their dispersal to birds, though I have no data relating to the matter 
of their dispersal, their fruits being capsular, in the first case prickly. 
Coriaria is a mountain genus in Tahiti and will be found dis- 
cussed in Chapter XXIV. in connection with the Tahitian mountain- 
flora. Its absence from the West Polynesian groups is no doubt 
to be connected with their insufficient altitude. In addition to 
the introduced Bidens pilosa, a common tropical weed, Tahiti 
possesses two other truly indigenous species of Bidens, of which one 
at least is peculiar to the region. The achenes of this genus are 
well known to be adapted for dispersal in a bird's feathers ; and 
since the genus has its principal home in America, no other indi- 
genous species having been recorded from South Polynesia, it is not 
unlikely that the parent species was American. 

One of the numerous enigmas of the Pacific floras is con- 
cerned with the presence in the islands of Tahiti and Moorea 
(Eimeo), in the Society Group, of the Apocynaceous tree, Le- 
pinia tahitensis. The genus contains this solitary species, which 
has been collected only in one other locality, namely, in the 
Solomon Group, where it was obtained by the Rev. R. B. Comins. 
Such an instance of disconnected distribution is rare in the Pacific 
Islands, and undoubtedly it represents one of the difficulties of the 
Tahitian flora. The fruits, which are indehiscent and five or six 
inches in length, possess a fibrous pericarp and a single seed. 



380 A NATURALIST IN THE PACIFIC CHAP. 

No data are to hand relating to the capacities for dispersal possessed 
by this plant, but it is certain that it has had some means of cross- 
ing the sea between the adjacent islands of Tahiti and Moorea. 
(See Hemsley, Journ. Linn. Soc t Bot., xxx. 165.) 

TAHITIAN GENERA FOUND IN HAWAII TO THE EXCLUSION OF 

FIJI. 

This subject has been already discussed in this chapter in 
dealing with the genera restricted to Hawaii and Tahiti. 

TAHITIAN GENERA FOUND IN FIJI TO THE EXCLUSION OF 

HAWAII. 

Excluding the orchids, sedges, and grasses, as well as the 
few endemic genera, between sixty and seventy genera, or rather 
less than half of the genera of the flowering-plants of Tahiti, are 
found in Fiji to the exclusion of Hawaii. Of these, rather over a 
half are Old World genera ; about a third occur in both the Old 
and the New World ; four are confined to Polynesia, and not one 
is exclusively American. One-third are genera now possessing in 
the Tahitian region endemic species either entirely or in part, 
and in such cases we may consider that the agencies of dispersal 
are now inactive or partially suspended ; the others belong 
entirely to the present era of dispersal. About half have more 
or less fleshy fruits fitted for dispersal by frugivorous birds. About 
a fourth have capsular or other dry fruits that must have been also 
dispersed by birds preferring a drier diet. Three only possess 
hairy seeds or fruits suitable for being carried in a bird's plumage, 
namely, Commersonia, Weinmannia, and Alstonia. There remain 
about a fourth of the total that are shore-plants dispersed by the 
currents, being in two cases (Ximenia and Kleinhovia) assisted 
by birds ; whilst Triumfetta, another littoral genus, is probably 
distributed by birds alone. 

There are no cases of special difficulty from the standpoint of 
dispersal in these sixty and odd non-endemic genera that Tahiti 
possesses in common with Fiji to the exclusion of Hawaii. The 
lack of difficulties connected with the dispersal of all these 
Tahitian genera is worthy of note, because there are very few 
difficult genera amongst the rest of the Tahitian flora. Excluding 
Lepinia tahitensis, which has been already referred to, there are 
scarcely any " impossible " plants in the Tahitian region ; and even 
in this case, when the modes of dispersal of Lepinia come to be 



XXVII 



TAHITI AN GENERA 381 



investigated, it is likely that much of the difficulty will disappear. 
Hawaii, as we have before seen, abounds with perplexing questions 
of this nature. When dealing with the absentee Tahitian genera, 
later on in this chapter, it will be shown that " size " has played a 
prominent determining part in the exclusion of genera from 
Tahiti, genera with seeds or " stones " exceeding half an inch or 
twelve millimetres in dimension being, as a rule, unrepresented 
amongst the truly indigenous plants. 

My further remarks on these Tahitian genera found in Fiji but 
not in Hawaii will be limited to some general observations from 
the standpoint of dispersal. I will first discuss some of those 
genera that possess only peculiar species. They belong to an era 
of dispersal that, as far as Tahiti is concerned, is passing or has 
passed away. Here we have the species of each genus more or 
less localised in the various South Pacific archipelagoes ; but, as 
with Meryta, Alstonia, and Loranthus, it is often apparent that, 
although the Tahitian region is mainly outside the zone of present 
dispersal, the different groups of the Western Pacific are kept in 
touch by the possession of species in common. This testifies to 
the activity of dispersal in that region after it had become sus- 
pended in Eastern Polynesia. The connection between the isolated 
endemic species of Eastern Polynesia and a species ranging over 
the Western Pacific can sometimes be shown, as in the case of 
Loranthus, where a species confined to the Society Islands and to 
the Marquesas is very closely related to L. insularum, a widely- 
ranging West Polynesian species that reaches eastward as far as 
Rarotonga. 

We next have those genera like Grewia, Nelitris, Melastoma, 
Randia, Geniostoma, Tabernaemontana, Fagraea, Bischoffia, Maca- 
ranga, and Ficus, that possess in Polynesia one or more widely- 
ranging species. The agency of the polymorphous species, which 
I have described in the preceding chapter in connection with the 
general dispersal of Malayan plants over the whole of Polynesia, 
is evidently also active when the work of dispersal is restricted to 
the South Pacific. Its operation is to be distinctly traced in all 
the genera above named except in Fagraea and Ficus. Thus, in 
the genera Grewia, Melastoma, Randia, Geniostoma, and Macaranga 
we find a single variable species ranging over the South Pacific 
from Fiji to Tahiti, keeping all the groups in touch, but associated 
in each, as a rule, with one or more peculiar species. A yet earlier 
stage in the process is to be seen in those genera which, like 
Nelitris, Tabernaemontana, and Bischoffia, possess only a solitary 



382 A NATURALIST IN THE PACIFIC CHAP. 

species ranging over the South Pacific, varying in each group, but 
not usually associated with endemic species. As with Melastoma, 
Macaranga, and others, we can often trace the widely-ranging 
species of Polynesia back to its =home in Malaya, and with these 
and other genera the connection between a species confined to 
a group and a variable species ranging through all the archipelagoes 
of the South Pacific can sometimes be detected in the affinity of 
their characters. 

It is thus seen that one of the principal determining causes of 
the differentiation of species in Polynesia lies in the failure of the dis- 
persing agencies, a widely-ranging species becoming in consequence 
gradually isolated in the various groups. With some genera, as 
with Ophiorrhiza, it is possible to show that the resulting endemic 
species pass into each other by intermediate forms. 

My further remarks on the Tahitian genera occurring in Fiji 
but not in Hawaii will be devoted mainly to those with which I 
was most familiar from the standpoint of dispersal. 

The Tiliaceous genus GREWIA offers a good example of those 
Polynesian genera which possess in the South Pacific a single widely- 
ranging species associated often with endemic species in the indi- 
vidual groups. It is likely that a polymorphous form, including 
most of the Polynesian species, could be here constituted. The 
fruits are dryish drupes, becoming black and moist when over-ripe, 
and containing three or four pyrenes suitable for distribution by 
birds and five or six millimetres in size. 

The berries of NELITRIS, a genus of the Myrtaceae, contain a 
few hard seeds that are well fitted for dispersal by frugivorous 
birds. I am inclined to follow Drake del Castillo, who considers 
that there is only one varying species, N. vitiensis (Gray), which is 
distributed over the whole of the South Pacific from the Solomon 
Islands to Tahiti. The tendency of this widely-ranging species to 
vary in different groups is indicated in the fact that some botanists 
have distinguished other species within these limits. It is note- 
worthy that N. paniculata in Indo-Malaya and N. vitiensis in the 
Pacific cover the whole range of the genus. It would be interest- 
ing to establish a connection between them. 

MELASTOMA, an Old World genus of forty and more species, 
has one very variable species, M. denticulatum, which, as defined by 
Bentham, has the range of the genus from tropical Asia across the 
Pacific to Tahiti. This plant is associated in some groups, as in 
Fiji, Tonga, and Samoa, with other more or less localised species, 
and it affords a good example of the principle of polymorphism in 



xxvii LORANTHUS 383 

species-making. The berry-like fruits contain an abundance of 
minute seeds, half a millimetre in size, which, when rendered 
adhesive by adherent pulp, might readily stick to feathers, or they 
might pass unharmed through the alimentary canal of a bird. It 
is noteworthy that amongst the plants regarded by Prof. Penzig as 
introduced by frugivorous birds into Krakatoa since the eruption 
is a species of Melastoma. 

Few genera in these islands would better repay a careful study 
of their species with regard both to the influence of station on 
specific characters and to the question of " mutations " than 
OPHIORRHIZA. I found the three Fijian species of this Rubiaceous 
genus so often in close association, that I cannot doubt there 
is some connection between them. Seemann and Gray, indeed, 
characterise two of them as confluent species. The island of Tahiti 
alone possesses five peculiar species, and it is evident that this 
island has been a centre of development for species of Ophiorrhiza, 
just as Samoa has become the birthplace of many species of the 
Urticaceous genus Elatostema. The minute angular seeds of 
Ophiorrhiza would probably be transported in a bird's feathers or 
in adherent soil. As my experiments showed, they do not become 
adhesive when wet. 

The genus LORANTHUS as distributed in the South Pacific has 
already been briefly noticed. There is a species confined to the 
Tahitian region, and there is another peculiar to Samoa, whilst one 
widely-ranging species, L. insularum, that connects these regions 
together, reaching east to Rarotonga, is closely related with the 
Tahitian species. There was no doubt originally a single poly- 
morphous plant that ranged over the tropical South Pacific. With 
regard to the mode of dispersal of the seeds of this genus of 
parasites, I should at once refer to the systematic and careful 
observations made by Mr. F. W. Keeble in Ceylon (Trans. Linn. 
Soc., v. 1895-1901). He formed the opinion that the seeds of 
Loranthus usually reach their host without passing through the 
alimentary canal of a bird, being merely wiped off its -bill. This 
method would never carry the seeds to Tahiti or even to Fiji ; and 
since this observer remarks that, although most of the seeds in the 
droppings were completely rotten, some of them " possibly pass 
through the gut uninjured," we may accept this possibility as 
sufficient for the purpose of dispersal in the Pacific Ocean. 
Mr. Keeble notes the observation in Teil 3 of Engler's Die 
Natiirlichen Pflanzenfamilien that the seeds may germinate after 
passing through a bird's intestine ; and we may therefore infer 



384 A NATURALIST IN THE PACIFIC CHAP. 

that whilst the method he describes is typical of local dispersal, the 
other method is required in the instance of oceanic dispersal. 

ALSTONIA, an Apocynaceous genus of tropical Asia and 
Australia, yields the caoutchouc of Fiji. Besides possessing in Fiji 
and Samoa peculiar species, the islands of Western Polynesia 
have in A. plumosa a species common to Fiji, Samoa, and New 
Caledonia. Another species, A. costata, is restricted to Eastern 
Polynesia, occurring in the different islands of the Tahitian Group 
as well as in Rarotonga. It is possible that the Pacific species 
may be connected with A. scholaris, a species possessing the range 
of the genus with the exception of Polynesia. The long ciliated 
or hairy seeds, six to nine millimetres in length, are fitted for 
transport by the winds and in birds' plumage. The follicles 
dehisce on the tree, and, according to Home, the light seeds are 
distributed locally by the wind. It is probable that the thick 
white juice oozing from a broken branch would at times aid the 
adhesion of the seeds to a bird's feathers. 

GENIOSTOMA, a genus of the Loganiaceae, is found in Malaya, 
Australia, and New Zealand. It possesses in G. rupestre a species 
that ranges across the South Pacific from New Caledonia to Tahiti, 
being associated with one or more endemic species in most of the 
groups. The fruit is a dehiscent capsule containing numerous 
small seeds imbedded in a yellowish pulp ; and from the stand- 
point of dispersal it may be placed in the same category with 
Pittosporum and Gardenia (see pages 310, 313). 

The same principle involved in the occurrence of a species 
ranging the South Pacific from New Caledonia to Tahiti, and 
associated with one or more endemic species in most of the 
principal groups, is illustrated in the Euphorbiaceous genus 
MACARANGA. It is specially noteworthy that M. tanarius, which 
ranges from India to East Australia and the New Hebrides, comes 
in touch in the group just named with M. harveyana, the widely- 
ranging plant of the South Pacific above alluded to, and itself an 
Asiatic species (see Burkill ; Bot. Chall. Exped., iii. 191 ; Index 
Kewensis). The connection between M. harveyana, the widely- 
ranging species of the South Pacific, and the endemic species in 
the various groups is indicated by its affinity with M. reineckei, a 
Samoan species. The Macarangas in Fiji grow in a variety of 
situations, on the borders of estuaries, in the mountain forests, and 
on the isolated mountain peaks. It is to birds that we must look 
for the dispersal of the genus. In the case of a species, apparently 
M. seemanni, common in the Rewa delta, the seeds, which soon fall 



xxvn FAGRJEA 385 

out of the cocci, are not infrequently found in the drift of the estuary, 
but they sink in a week or two. Other species examined showed 
no capacity for dispersal by currents. The fruit of M. harveyana is 
provided with a few prickles, but since it breaks up into the cocci, 
from which the seeds soon fall out, these appendages could scarcely 
aid its dispersal. 

Like many other genera, TABERNyEMONTANA, an Apocynaceous 
genus distributed through the tropics, is represented in Polynesia by 
a widely-ranging species, T. orientalis, which extends from Malaya 
and Eastern Australia through all the large groups of the South 
Pacific from the New Hebrides to Tahiti, and is associated in Fiji 
with one or two peculiar species, one of which, according to 
Mr. Burkill, is nearly related to it. This genus therefore seems 
to illustrate the earliest stage in the Pacific of that process by 
which a widely-ranging species takes on a polymorphous habit 
and through its variations gives rise to different species in various 
groups. Prof. Schimper ranks T. orientalis amongst the Malayan 
strand-flora ; but in Fiji the Tabernaemontanas are only littoral 
where the soil is rich as in alluvial regions ; and they have no 
capacity for dispersal by currents that is worth speaking of, the 
seeds in the case of T. orientalis and another species sinking after 
drying for years, whilst the follicles soon open in water and go to 
the bottom in a few days. The observations of Gaudichaud and 
Moseley indicate that some Malayan species are dispersed locally 
by the currents (Bot. Chall. Exped., iii, 279, 293) ; but the fruits 
of the genus are evidently quite unfit for oceanic dispersal by 
this agency. We find in the bird the agent that has carried the 
genus to the distant island-groups of the Pacific ; and from the 
standpoint of dispersal the fruits may be placed with those of 
Pittosporum and Gardenia, being follicular, and in the Fijian 
plants possessing seeds, 5 to 10 millimetres in size, embedded in 
a pulp. 

FAGR/EA, an Asiatic and Malayan genus of the Loganiaceae, is 
represented in the Pacific by F. berteriana ranging through all the 
groups and islands of the South Pacific from the Solomon Islands 
and New Caledonia to Tahiti and the Marquesas, and by one or 
two other species in Fiji. It is with Fagraea berteriana that we are 
entirely concerned. The tree is often planted by the Pacific 
islanders near their villages ; and since they value its timber and 
use its large fragrant flowers for personal decoration and for other 
purposes, it is probable that they have aided in its dispersal. But, 
as shown below, it behaves in most localities as an indigenous 
VOL. II C C 



386 A NATURALIST IN THE PACIFIC CHAP. 

plant ; and its berries are well fitted for promoting its dispersal by 
frugivorous birds. 

I was familiar with Fagraea berteriana both in the Solomon 
Islands and in Fiji ; and in the last-named locality I especially 
studied it from the standpoint of dispersal. All over the South 
Pacific, whether in the Solomon Islands, in Fiji, in Rarotonga, or in 
Tahiti, this tree, though thriving also in the lower levels, especially 
frequents rocky scantily vegetated or open-wooded hill-tops and 
crests up to 2,000 or 2,500 feet above the sea. In the rich alluvial 
soil of the Rewa delta in Fiji it attains a height of 25 or 30 feet or 
more, whilst in the poor, dry soil of the " talasinga " plains in this 
group it is much dwarfed, and often does not exceed 10 feet, and 
may be only 6 feet high. It is in these "talasinga," or "sun- 
burnt," plains of Fiji, especially in the Mbua province of Vanua 
Levu, that the tree, although dwarfed, seems most at home. Here 
it flowers and fruits abundantly whilst associated with Acacia, 
Casuarina, and Pandanus trees, and it is in such dry localities that 
this tree reflects in its choice of station the behaviour of different 
species of the genus in the Malay Peninsula, where they grow in 
open heath-country and sometimes on sandy heaths (Ridley in 
Trans. Linn. Soc. Bot.> iii, 1888-94). The fruits and seeds of F. 
berteriana have little or no capacity for dispersal by currents. On 
the Fijian plains the berries partially wither and rot on the tree. In 
the western part of its area this tree almost comes in touch with 
the Asiatic species, F. obovata, that ranges from India and 
Ceylon to the Malayan region, a species that must be indebted to 
frugivorous birds for its wide distribution. 

The Euphorbiaceous genus BlSCHOFFIA seems to offer another 
example of polymorphism in a wide-ranging species. Following 
Drake del Castillo, I take the genus as including only a single 
species, B. Javanica, a tree distributed over tropical Asia, Malaya, 
and Polynesia as far east as Tahiti. The variable character of the 
species is indicated by the different views held by the several 
botanists who have discussed the South Pacific species. Whilst it 
is a common forest-tree in Indo-Malaya, it affects in the Pacific 
islands the open-wooded districts of the lower levels, and it is not 
uncommon on the dry " talasinga " plains of Fiji. The fruits and 
seeds displayed in my experiments little or no capacity for dispersal 
by currents ; nor do these dryish berries, with seeds four or five 
millimetres long, seem to be especially attractive for fruit-eating 
birds ; and it is likely that the same birds that distribute Macaranga 
seeds also disperse those of this genus. The tree bears the same 



XXVII 



FICUS 387 



name over the South Pacific, "koka" in Fiji and Rarotonga, and 
" oa " in Samoa. Like many other Polynesian trees, it has its uses, 
but there is no reason to believe that the natives have aided 
materially in its dispersal. 

FlCUS, a large genus comprising several hundred species, attains 
its greatest development in tropical Asia and in Malaya. It is well 
represented in the Western Pacific from the Solomon Islands to 
Fiji and Samoa ; but in Eastern Polynesia the species are very 
few, and the genus is altogether absent from Hawaii, although a 
species has been found in the North Pacific in Fanning Island, 
about 900 miles south of the Hawaiian group (see page 377). 

The Polynesian species are for the most part restricted to the 
Pacific islands, but there are only two species that range over the 
South Pacific as far east as Tahiti, namely, Ficus prolixa, the 
Tahitian banyan, and F. tinctoria. Some species are confined to 
Western Polynesia, such as F. obliqua, the Fijian banyan, F. scabra, 
and F. aspera, the last occurring in East Australia. Among the 
individual groups Fiji possesses probably fourteen or fifteen species, 
of which, perhaps, a third would be peculiar. According to Dr. 
Warburg, as cited in Dr. Reinecke's paper, Samoa owns eight species, 
of which six may be endemic. In Rarotonga and Tahiti we find 
only F. prolixa and F. tinctoria. The species in the groups where 
they are best represented belong to three or four sections of the 
genus. 

The banyans of the South Pacific are represented by three or 
four species, namely, Ficus prolixa, the Tahitian banyan, found all 
over the tropical groups of the South Pacific from the New 
Hebrides and New Caledonia to Tahiti, the Marquesas and 
Pitcairn Island (Maiden) ; F. obliqua, the Fijian banyan, confined 
to the islands of the Western Pacific from the New Hebrides to 
Tonga ; and two new banyans in Samoa, as described by Dr. 
Warburg in Dr. Reinecke's paper. In my paper on Polynesian 
plant-names it is shown that the banyans possess two names in the 
Pacific, one being "aoa," the Polynesian name, found in all the 
groups from Samoa eastward, and connected linguistically with the 
Malayan and Malagasy banyan-words ; the other, the Melanesian 
name typified in the Fijian " mbaka," and represented in a variety 
of forms in the New Hebrides and neighbouring groups. 

It is probable that the Pacific islanders have assisted in the 
dispersal of one or two of the species of Ficus, such as F. tinctoria, 
which they employ for different purposes, but, generally speaking, 
birds are active agents in distributing the genus. I need scarcely 

C C 2 



3 88 A NATURALIST IN THE PACIFIC CHAP. 

say that the agency of the currents is quite insufficient to explain 
the distribution of Ficus. When in Fiji I experimented on three or 
four different species of Ficus belonging to the sections of the genus 
there represented. The fruits may float at first, but within a week 
or ten days they break down, and the seeds escape and sink. 
Beneath a tree of F. scabra growing on the banks of the Wai 
Tonga in Viti Levu, I noticed a number of its fruits floating in a 
sodden condition among the reeds at the river-side. 

It is with the banyans that the dispersal of the seeds by 
frugivorous birds becomes most evident. This is at once indicated 
by the frequent occurrence of these trees in the interior of coral 
islets in the Western Pacific, as in Fiji and in the Solomon Islands. 
Fruit-pigeons roost in their branches, and birds shot on these islets 
often contain the fruits in their crops (Bot. ChalL Exped., iv, 310). 
The process may also be seen in operation in Krakatoa. Professor 
Penzig found in 1897 that three species of Ficus had established 
themselves there since the eruption of 1883 through the agency of 
frugivorous birds. Besides pigeons, we find that parrots, hornbills, 
honey-eaters, &c., feed on these fruits, and I possess a large number 
of references to this subject. The Messrs. Layard in New Caledonia, 
Dr. Meyer in Celebes, Mr. Everett in Borneo, Dr. Forbes in 
Sumatra, and several other contributors to Ibis might be here 
mentioned. Dr. Beccari, in his Wanderings in the Great Forests of 
Borneo, speaks of " the facile dissemination of the various species of 
Ficus through the agency of birds," and he arrives at certain 
important conclusions which are discussed in Chapter XXXIII. 

I have before alluded to the absence of Ficus from Hawaii. 
This group possesses the Honey-Eaters (Meliphagidae), birds well 
suited for dispersing species of Ficus over Polynesia ; but this 
family of birds is only represented by peculiar genera in Hawaii, 
and therein lies the explanation. At the time when the Honey- 
Eaters roamed over Polynesia, the genus Ficus had not arrived 
from Malaya. The connection between the bird and the plant is 
well shown on Fernando Noronha, which possesses a peculiar 
species of Ficus and a peculiar species of dove, the only fruit-eating 
bird in the island (Ridley). 

THE ABSENTEES FROM TAHITI 

Generally speaking, all the " difficult " genera which puzzle the 
student of plant-dispersal in Fiji and Hawaii are absent from the 
Tahitian region. Those with stone-fruits and with large seeds. 



xxvii THE ABSENTEES FROM TAHITI 389 

where the stone or seed is an inch in size and over, are absent from 
Tahiti. Thus the genera Canarium, Dracontomelon, Myristica, 
Sterculia, and others, of which the three first-named are known to 
be dispersed by fruit-pigeons, have not advanced into the Pacific 
eastward of the Fijian region. We miss in the Tahitian islands the 
large-fruited palms of Fiji, such as the Veitchias with fruits two to 
two and a half inches (5 to 6 cm.) long, and we find in their place 
a Ptychosperma, evidently very rare, and the widely spread 
Pritchardia pacifica, that may have been introduced by man, both 
with drupes not far exceeding half an inch (i'2 cm.) in size. The 
islands of the Tahitian region also lack the Coniferae ; and genera 
like Dammara, Dacrydium, and Podocarpus that give such a 
character to the Fijian forests are not to be found. In this region 
we do not find many of the large-seeded Leguminous genera, such 
as Cynometra, Storckiella, and Afzelia, that occur in Fiji, the only 
large-seeded genera that it possesses being such as are brought by 
the currents, namely, Mucuna, Strongylodon, Caesalpinia. The 
difficulties presented by the occurrence of the inland species of 
Canavalia and Mezoneuron in Hawaii do not offer themselves in 
Tahiti (see Chapter XV). Tahiti also lacks, as often before 
observed, the mangroves and most of the plants of the mangrove- 
formation. 

As above remarked, the Fijian trees with large " stones " and 
heavy seeds an inch in size are not to be reckoned amongst the 
indigenous Tahitian plants, " size " being an important determining 
factor in the exclusion. The occurrence of Elaeocarpus in Rarotonga 
presents no real difficulty, as I have explained in Chapter XXVI. 
An apparent exception is presented by the existence in Tahiti of 
-Calophyllum spectabile, where the stones are about an inch across ; 
but since its fruits can float in sea-water for nearly a month, and on 
account of the value placed on its timber by the Polynesians, we 
cannot altogether exclude the agencies of man and the currents. 
One seeming exception is also offered by the presence of Serianthes 
myriadenia, a tree which in Fiji grows both in the forests and on 
the banks of the tidal estuaries. Its seeds, which are six to seven- 
tenths of an inch (15 to 18 mm.) in length, have no buoyancy, and 
the pods float only two or three weeks. The case of Lepinia 
tahitensis is alluded to elsewhere, but it may be added that these 
and other difficulties await further investigation. 

A great many Fijian plants are not found in the Tahitian 
region, such as Micromelum, those of the order Meliaceae, the 
Melastomaceous genus Medinilla, Myrmecodia, Ophiorrhiza, &c., 



390 A NATURALIST IN THE PACIFIC CHAR 

which are often quite as well fitted for over-sea transport as are 
several of the plants already established there. But it should be 
remembered that crowding out would often come into play in such 
a contracted region. The area, however, has been very generously 
dealt with as regards plant genera. Though the total land-surface 
cannot be more than one-fourth or one-third that of Fiji or Hawaii,, 
it possesses more than half the number of genera found in Fiji, and 
four-fifths of the number found in Hawaii. 



FIJI 

The Fijian Genera not found in either the Tahitian or 
Hawaiian Regions 

We have already in some degree dealt with Fiji in so far as the 
partial dispersal of genera over the Pacific islands is concerned. 
We have seen that it possesses very few genera (not a score in all) 
in common with Hawaii that are not found in the Tahitian region, 
and it is assumed that in most cases such genera reached Hawaii 
independently and not through the South Pacific. On the other 
hand, excluding the grasses, sedges, and vascular cryptogams, Fiji 
owns in common with Tahiti between sixty and seventy genera, 
that do not occur in Hawaii. This shows unmistakably the trend 
of plant migration in the Pacific islands. Several interesting 
features in plant-distribution have been already brought out, and 
notably the fact that Indo-Malayan genera with large seeds or 
" stones " an inch in size have been arrested in the Fijian region 
in their passage into the South Pacific. Thus Canarium,, 
Dracontomelon, Myristica, and Sterculia have not extended east- 
ward of the Fijian area. 

Yet a very large proportion of the Fijian genera, quite half of 
the total number, are not represented either in the Tahitian or in the 
Hawaiian region ; and of many of them it is obvious that they are 
as well fitted to be carried over the Pacific as are those that have 
actually reached Tahiti and Hawaii. Take, for instance, Begonia, 
which has not extended east of Fiji, though Hillebrandia, a genus 
of the order, is peculiar to Hawaii. Nor can we explain why with 
three genera like Geissois, Dolicholobium, and Alstonia, possessing 
seeds dispersed by the winds, only the last-named has passed 
beyond Fiji. However, as before remarked, it is probable that lack 
of opportunity rather than capacity for dispersal has determined the 
matter, and we must, therefore, assume that many of the genera have 



xxvn STERCULIA 391 

halted in the Fijian region because they entered the Pacific after 
the age of active general dispersal over that ocean. 

Occasionally we notice in this region that which we have 
observed in the case of Cyrtandra in different Pacific groups, 
namely, a sudden development of what Hillebrand terms " formative 
energy " in a genus, such as we find in the case of Elatostema in 
Samoa, and in that of Psychotria in Fiji and Samoa. The principle 
of polymorphism in the development of species is also illustrated 
by Micromelum and by Limnanthemum. In the last case we 
possess a typical polymorphous species in Limnanthemum indicum 
that has played in this respect the role of Naias marina in the warm 
waters of the globe. 

With several genera that like Gnetum, Myristica, and Sterculia 
occur both in the Old and the New World, it is evident that in 
explaining their distribution we are dealing with something more 
than questions of means of dispersal. With these genera, and with 
others like Lindenia, it seems almost futile to talk of means of 
dispersal, when to all appearance their existing distribution is but 
the remnant of an age of general dispersion over the greater part 
of the warm regions of the world. These genera, with others, might 
be cited in favour of the continental hypothesis relating to the 
islands of the Western Pacific. Trees with stone-fruits, such as 
Canarium, Couthovia, Dracontomelon, and Veitchia, where the 
stones are an inch and more in length, might be also adduced by 
some in evidence of this theory. But in these cases the lesson of 
Elaeocarpus (Chapter XXVI) should always be remembered, since 
the "stones" of drupes may vary greatly in size amongst the 
different species of a genus, and species seemingly " impossible " 
from the standpoint of dispersal in one group may be represented 
in other groups by species where the size of the " stone " presents 
no difficulty in attributing the dispersal of the genus to frugivorous 
birds. 

Sterculia 

The problem connected with the presence of this genus in Fiji 
is but a part of the still more difficult problem connected with the 
dispersal of the genus over the tropics. The riddle presented by 
the Fijian species seems, indeed, difficult enough ; but it merely 
presents in miniature the great mystery surrounding the whole 
genus. According