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Full text of "The new flora of the volcanic island of Krakatau"

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THE NEW FLORA 

OF THE 

VOLCANIC ISLAND 

OF 

KRAKATAU 







CAMBRIDGE UNIVERSITY PRESS WAREHOUSE, 

C. F. CLAY, Manager. 

aonioti: FETTER LANE, E.C. 

flRiinburflfj : 100, PRINCES STREET. 




fUtpjta: F. A. BROCKHAUS. 

33ftlm: A. ASHER AND CO. 

#efo lork: G. P. PUTNAM'S SONS. 

Bombag anti Calcutta: MACMILLAN AND CO., Ltd. 



\_All Rights reserved] 



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THE NEW FLORA 

OF THE VOLCANIC ISLAND 

OF KRAKATAU 



BY 

A. ERNST, Ph.D. 

PROFESSOR OF BOTANY IN THE UNIVERSITY OF ZURICH 

TRANSLATED BY 

A. C. SEWARD, F.R.S. 

PROFESSOR OF BOTANY IN THE UNIVERSITY OF CAMBRIDGE 



WITH TWO SKETCH-MAPS AND THIRTEEN 

PHOTOGRAPHS 




Cambridge : 

at the University Press 

1908 



Cambridge: 

PRINTED BY JOHN CLAY, M.A. 
AT THE UNIVERSITY PRESS. 



(2K 
Kl67 



PREFACE 

P"PHE following pages consist mainly of an account of an expedition 
X to the volcanic island of Krakatau which I had an opportunity 
of making in the spring of 1906 in company with some other botanists. 
The work was originally published in the Viertcljahrsschrift der 
naturforschenden Gesellschaft in Zilrich (Jahrgang 52, 1907) : a 
few reprints only were available for purchase. I therefore agreed 
with pleasure to the proposal made to me by the Cambridge 
University Press to publish an English translation, particularly as 
Professor Seward, who carried out the preliminary negotiations, 
kindly offered to be the translator. I wish to express my cordial 
thanks to him. I would also thank the Syndics of the University 
Press for the care with which the volume has been produced. 

Four hitherto unpublished photographs have been added to those 
published in the German edition. I have also taken the opportunity 
of making a few corrections and additions, so that the English trans- 
lation may be regarded as a second edition of the original work. 

A. ERNST. 

Zurich, 

September, 1908. 



NOTE BY THE TRANSLATOR 

THE unique example, afforded by the development of the New 
Flora of Krakatau, of the colonisation of an island, completely 
deprived of vegetation by a series of volcanic eruptions, is a sufficient 
justification for the publication of Professor Ernst's pamphlet in an 
English form. 

The additional photographs (Plates V. and VII.) referred to by 
the Author in the Preface have been reproduced from prints kindly 
supplied by Professor Ernst from his own negatives. A few references 
and other additions for which the translator is responsible are enclosed 
in square brackets. To Professor and Mrs Ernst I am greatly indebted 
for several corrections and additions which they have made in the 
course of their careful revision of the English text : I am indebted 
also to Colleagues in the Botany School for help in regard to certain 
passages in the translation. 

A. C. SEWARD. 
Botany School, Cambridge, 
September, 1908. 



CONTENTS 



Introduction 



PAGES 

14 



I. Results of the visits of 1886 and 1897 58 

II. The Expedition of April 2427, 1906, to the Sunda Strait 

region and to Krakatau 8 37 

1. Vegetation and Flora of the Coral Island of Edam . 9 15 

2. On the beach at Vlakke Hoek (Sumatra) . . . 15 18 

3. In the Sunda Strait; winds and ocean-currents . . 19 23 

4. On the south-west coast of Java ; Java's First Point . 23 26 

5. On Krakatau and Verlaten Islands .... 26 37 

III. The present composition of the Flora of Krakatau . . . 3748 

IV. Biological conditions on Krakatau 48 53 



V. The relative importance of the different agents of plant-dispersal 

in the colonisation of the Krakatau Islands . . . 53 68 

1. Ocean-currents 54 53 

2. Seed-dispersal by birds 58 60 

3. Dispersal of fruits and seeds by wind .... 60 66 

4. Part played by the several agents of dispersal in the 

development of the present Flora of Krakatau . 66 68 

VI. Succession of plant-associations and the future character of 

the vegetation of Krakatau 68 72 



Bibliography 73 74 



PLATES 



I. Narrow Drift Zone and Pes-caprae Zone, Strand-forest 

(south-east coast of Krakatau) . . . Frontispiece 

II. Map of the Sunda Strait. 

Sketch-map of the Krakatau Islands (after Verbeek) . . To face p. 4 

III. Fig. 1. View of Krakatau from the North. 

Fig. 2. Peak of Rakata (832 m.) and the fractured rock-face 23 

IV. Fig. 3. Drift-zone on the south-east coast of Krakatau. 

Fig. 4. Level beach between the vertical rock-face and the 

promontory of Zwarte Hoek .... 27 

V. Fig. 5. Casuarina equisetifolia in the Strand-forest of 

Krakatau. 

Fig. 6. The new Strand-forest on the south-east coast of 

Krakatau 28 

VI. Fig. 7. Young coconut palm at the upper edge of the tide- 

level (south-east coast of Krakatau). 

Fig. 8. Pandanus on the beach (east coast of Krakatau) 30 

VII. Fig. 9. Luxuriant group of Pandanus plants on the east 
coast of Krakatau. 

Fig. 10. Spinifex squarrosus with spherical heads of fruit 30 

VIII. Fig. 11. Clearing in the Strand-forest. 

Fig. 12. Grass-steppe in the interior of Krakatau . 32 



INTRODUCTION 

A quarter of a century ago the small group of islands, Krakatau 1 , 
Verlaten island, and Lang island, lying in the middle of the Sunda 
Strait between Java and Sumatra, was the scene of the most violent 
volcanic outburst of historic times. The three islands enclose an 
almost circular basin approximately 40 square kilometres [25 sq. 
miles] in area. Before the terrific explosion, which lasted from 
August 26th to August 28th, 1883, the northern part of Krakatau 
which was then 9 kilometres long and 5 kilometres broad [5^ x 3 miles] 
was separated from the other two islands by narrow arms of the sea. 
On the south side the peak Rakata rose in the form of a steep cone 
to a height of 832 metres [2728 feet] ; on the slope of this, near the 
centre of the island, was situated the many-peaked hill of Danan, 
400 metres [1350 feet] high, the remnant of an annular crater- 
wall. Towards the north the hilly region of the Perboewatan, 

1 The official local names are Poeloe (island) Rakata for Krakatau, P. Sertoeng 
for Verlaten island, P. Rakata Ketjil for Lang island. Verbeek was unable to obtain 
any definite information as to the meaning of the word Krakatau either from pub- 
lished sources or as the result of enquiries. The official designation Rakata appears 
to be an altered form, as the word occurs in Malay writings also as Kalkata and 
Karkata. The last name appears as early as 1611 on a small map of the Sunda 
Strait. Possibly the name of the island conies from the Sanskrit Karta, Karkata, 
Kartataka, which means Crab. Junghuhn also states (Jara, seine Gestalt, Pflanzen- 
decke iind innere Bauart, Leipzig, 1854, Vol. iv. p. 1) that Rekata or Rakata is, in 
the old Javan language (the so-called Kawi language), the term for Crab ; hence the 
name Poeloe Rakata would possibly assume the form Crab-island. The present form 
Krakatau has perhaps arisen from the translation of Rakata into the language of 
sailors. Since the eruption the name Krakatau, which had already become more 
commonly used by the natives than Rakata, has passed into general use. Other 
forms such as Krakataoe, Krakatoa, Krakatoea, which occur in the literature, are 
uuknown in the Malay Archipelago. We therefore follow Verbeek in calling the 
island Krakatau and its highest peak Rakata. 

[In the Royal Society's volume on Krakatau (see note 1, p. 2), the form Krakatoa 
is used, and this spelling has become general in England; as, however, there appears to 
be no sufficient reason for departing from the more widely accepted form Krakatau 
I have followed Professor Ernst in adopting this form. A. C. S.] 

s. 1 



2 Introduction 

dominated by several small elevations, extended to the coast 1 . The 
whole island, from the beach to the summit of Rakata, was covered 
with an impenetrable forest. Verbeek who paid a short visit in July 
1880 to the northern part of the uninhabited island, which has since 
disappeared, found some lava-streams which reached the coast only in 
the Perboewatan region ; these were covered by a sparse vegetation 
and their surface was but slightly weathered. The lava-streams 
were probably formed during the only recorded eruption of 1680. 

For a long time the island had been regarded as an extinct volcano. 
On May 20th, 1883, a new crater on Perboewatan suddenly became 
active, the activity being accompanied hj loud explosions which were 
heard for a considerable distance over Java and Sumatra, and after 
a few days a large part of the island and a portion of Verlaten island 
were covered with a layer of ash and pumice to a depth of 1 metre. 
On the north side of the highest peak, and here and there over the 
whole of the northern part of Krakatau, stems of trees could still be 
seen rising above the grey ground as miserable remnants from the 
former luxuriant forest ; while on the south side of the cone, on 
Lang island and on a fourth island, Poelsche Hoed (Polish Hat), 
situated between Lang and Verlaten islands, which has completely 
disappeared since the eruption of August 2 7th, the vegetation suffered 
but little. 

In June a second crater was formed at the foot of Danan, which 
threw out ashes and pumice. At the beginning of August a third 
crater, together with numerous fissures which gave off steam and 
smoke, appeared on the southern slope of Danan ; this was after- 
wards completely shattered and served as the main crater during 
the last eruptions. 

The outbursts increased in frequency and culminated in the 
terrible catastrophe of August 26th and 27th, the effects of which 
were felt over almost the whole surface of the earth. The explosions 
were heard not only throughout the Malay Archipelago, but also in 
Ceylon, Burma, Manilla, New Guinea and on the west coast of 
Australia 2 . At Batavia and Buitenzorg in Java, 150 kilometres 
[92h miles] from the scene of the explosion, the noise resembled 
artillery fire at close range 3 . The vibrations made the window-panes 

I 1 See the outline section of Krakatau published in " The Eruption of Krakatoa 
and subsequent Phenomena" (Report of the Royal Society Committee), p. 6, fig. 4, 
London, 1888.] 

[ 2 For map showing the places at which the sounds of the explosions were heard 
on Aug. 26, 27, see Rep. Roy. Soc. PI. XVI.] 

[ 3 The most remote place at which sounds were heard is said to be Rodriguez, 
nearly 3000 miles from Krakatau. Rep. Roy. Soc. p. 79.] 



Eruption of 1883 3 

rattle and shook the houses to such an extent that objects were 
thrown from tables. 

During the eruption the volcano covered the whole neighbour- 
hood for a distance of 3o kilometres [22 miles] with glowing stones 
and hot ashes. Near the centre of activity, on the island of Sebesi, 
with 2000 inhabitants, villages suffered the fate of Herculaneum 
and Pompeii. A dense rain of ashes fell over the whole of South 
Sumatra, to Benkoelen and Palembang in the north, in West Java 
beyond Batavia and the residency of Preanger, while the finer dust 
was spread over a much greater area amounting approximately to 
600,000 square kilometres [234,000 square miles]. In a south-westerly 
direction the rain of ashes extended 1200 kilometres [750 miles], 
and it is well known that the finest particles mixed with aqueous 
vapour and suspended in the upper region of the atmosphere were 
carried round the world and caused the wonderful twilight effects 
which were observed everywhere in December 1883 1 . The total 
amount of material thrown out from the craters of Krakatau from 
May to August 1883 was estimated by Verbeek, after careful calcu- 
lation, at 18 cubic kilometres [4'4 cubic miles]. As a result of this 
enormous loss of material the chief crater and adjacent parts of the 
island were undermined and on the morning of August 27th the 
climax was reached : a large portion of the island and of the 
surrounding sea-floor fell in like an insufficiently supported vault. 
The sea was drawn after the debris from all sides into a funnel-like 
depression and, surging up again over the submerged crater, produced 
gigantic waves which rose to a height of 40 metres [131 ft.] and, carrying 
with them blocks of rock which reached 300 cubic metres in bulk, broke 
repeatedly on the coasts of Java and Sumatra. For a distance of several 
kilometres inland everything was destroyed ; whole villages disap- 
peared and about 30,000 people were drowned. In the shallow Java Sea 
the waves acquired less force. The low islands in the Bay of Batavia 
suffered considerable damage and in Tandjong Priok, in the harbour 
of Batavia, from midday on August 27th for the next 36 hours as 
many as 18 seismic waves were recorded, the first and highest of 
which reached a height of more than 2 metres. On the same day 
large waves were produced in all the harbours of the Indian Ocean 
where the deeper water furnished much more favourable conditions 
for their transmission. By August 28th the seismic waves had found 
their way into the North Atlantic Ocean and were recorded at 
Rochefort, Cherbourg, Havre and other places 2 . 

The geological expedition conducted by Verbeek, which under- 

P See Part IV. and PI. XXXVI., Rep. Roy. Soc. Committee.] 
[ 2 See Report Roy. Soc. Com. Part III.] 

12 



4 Introduction 

took the investigation of the group of islands two months after the 
eruption, found that enormous geographical changes had occurred 
(see Sketch-map, PI. II.). The small island Polish Hat, part of Lang 
island as well as two-thirds of Krakatau itself, embracing an area of 
22'85 square kilometres [8'9 square miles], had sunk. The line of 
fracture passed through the middle of Rakata, the highest peak of 
which still remained. The face of the mountain from summit to sea- 
level now formed a steep and almost vertical wall (Plate III.). At 
the foot of the cliff and beyond in the new area of sea which occupied 
the site of the former crowded group of islands, the lead touched 
bottom at a depth of 100, 200 and in places 300 metres. 

No lava-flows appear to have occurred during the whole period of 
volcanic activity, but on the other hand the three islands were 
covered with pumice and layers of ash reaching on an average a 
thickness of 30 metres and frequently 00 metres [98 196 ft.]. To 
this extent Verlaten island and Lang island were increased in 
height : the former had also increased in circumference. 

A new marginal belt was formed along the south-west to the 
south-east coast of Krakatau, 4*6 square kilometres of land being 
added to the zone of 107 square kilometres which remained. During 
the short period of two months after the eruption subaerial denuda- 
tion had already carved out of the loose strata deep valleys and gorges 
in some cases with vertical walls from 6 to 8 metres high. In the 
vicinity of the peak, where the newly formed deposit must have been 
thinnest, patches of the original rock surface protruded here and 
there exposing the blasted and carbonised remains of tree steins. 
The last remnants of plant-life which had withstood the first 
outbursts were everywhere destroyed and buried under a thick 
covering of glowing stones. The islands, which were formerly green, 
assumed the appearance of a desert of the most desolate type, a 
desolation, uninhabited and in all probability for a considerable 
period uninhabitable, separated by 19 to 25 kilometres [1215^ 
miles] from the neighbouring and half-destroyed islands of Sebesi 
and Seboekoe and by 35 to 45 kilometres [22 28 miles] from the 
nearest points of the Javan and Sumatran coasts. But the first 
pioneers of plant and animal life soon obtained a footing and to-day, 
25 years since the complete destruction of all organic life on the 
group of islands, these are again covered with a mantle of green, 
the growth being in places so luxuriant that it is necessary to cut 
one's way laboriously through the vegetation. 


































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Initial Stages in Colonisation 5 



I. Results of the visits of 1886 and 1897. 

Dr Melchior Treub, the distinguished and genial Director of the 
Botanical Institute at Buitenzorg in Java, rendered a great service to 
Science by initiating the study of the new Krakatau flora and thus 
paving the way for further investigations. The botanical explorations, 
made on three different occasions, of the islands which were entirely 
depleted of vegetation in Itttt'A have not only furnished results of 
general biological interest, but by demonstrating the successive 
stages in colonisation, they also afford one of the most important 
contributions towards the solution of the much discussed problem as 
to the source and history of the introduction of a flora into an island 
far removed from the mainland. The older literature 1 concerned 
with this interesting problem in plant-geography, so far as regards 
direct observation, deals with the history of colonisation of recently 
formed coral islands, that is of flat land surfaces, and with the 
investigation of the means of dispersal of plants from older coral 
reefs and volcanic islands. On Krakatau, Treub 2 had an opportunity 
of studying the more complex problem : how a volcanic island, which 
has lost the whole of its flora as the result of an eruption, acquires a 
new vegetation ; how, in other words, an island of considerable height 
suddenly emerging from the sea becomes stocked with plants ; and 
further by what successive stages the new floral elements appear on 
the island and by what external agencies the colonisation is effected. 

The first germs of land-plants are brought by ocean-currents 
which carry seeds and fruits, drifting on the surface of the water, to 
the low-lying beach of emerging coral islands. Some of these seeds 
on arrival are still capable of living ; they germinate and, provided 
the conditions are not too unfavourable, continue to grow and con- 
stitute the first plants of the island. It has long been known that 
only a comparatively small proportion of plants are capable of ex- 
tending the area of their distribution by this means. 

A comparison of island floras has shown that it is exclusively 
strand-plants in the Malay Archipelago there are about 320 species 
which have seeds and fruits possessing the necessary adaptations for 
this method of dispersal by ocean-currents, that is which are capable 

1 A complete list will be found in W. B. Hemsley's "Report on the present state of 
knowledge of various Insular Floras." Introduction to the first three Parts of the 
Botany of the Challenger Expedition, Botany, Vol. i. p. 69. 

2 M. Treub. "Notice sur la nouvelle Flore de Krakatau." Annates du Jar din 
botanique de Buitenzorg, Vol. vil. 1888. 

M. Treub. "Overhet nieuwe Plantenkleed van Krakatau." Natuurkundig Tijd- 
schrift root' Nederlandsch- Indie, Band 48, 1889. 



6 Krakatau 1886 and 1897 

of floating for weeks or months on sea-water without losing the 
power of germination. 

Among the agencies concerned in the colonisation of coral islands 
the second place may be ascribed to birds which use them as resting 
places or visit them in search of food. They serve in various ways to 
enrich island floras. Fruit-eating birds eject seeds which have 
passed uninjured through their intestine. In the process of cleaning 
and preening their plumage birds often rub off small fruits and seeds 
attached by hooks or other contrivances to their feathers or which 
are carried with earth or mud on their feet. 

Numerous coral islands owe their first and most widely spread 
plants to ocean-currents and to birds. Spores and seeds of other 
plants, as extended observations have shown, are introduced by wind 
and occasionally by other agencies ; these quickly fill up gaps in the 
vegetation, finding in the substratum already prepared by earlier 
arrivals, conditions favourable for germination and subsequent 
development. 

In the case of Krakatau, Treub expected to find phenomena 
analogous to those already referred to as characteristic of the 
progress of colonisation of recently formed coral islands 1 ; he wrote: 
" Le littoral de l'ile se couvre de plantes a l'aide des graines amenees 
par les courants oceaniques et par les oiseaux tout comme chez les 
iles de corail. Les elements qui composent la flore de cette bande 
littorale remonteront petit-a-petit les versants de File ; cela est 
possible parceque la plupart de ces plantes, bien que preferant une 
station saline, croissent vigoureusement encore eloignees de la plage 
et a une assez grande altitude. Cependant, plus la bande v^getale 
originaire de la plage remonte et plus sa marche se ralentira. 
Finalement ce sera presque uniquement par rentremise des oiseaux 
que les parties les plus elevees de File se peupleront de plantes. 
Une fois toute l'ile couverte d'un tapis vegetal peu dense encore, le 
terrain sera peu a peu prepare a recevoir d'autres plantes dont les 
spores ou les graines sont amenees par le vent ou par d'autres causes." 

The actual method of plant introduction has, however, proceeded 
along altogether different lines. In June 1886, when the island was 
first visited by Treub, the pioneers of a new vegetation were seen from 
the shore to the peak and he was able to establish the important fact 
that the re-stocking of the beach and of the interior, including the 
slopes of the cone, had been effected simultaneously, though in 
different ways and for the most part by different plants. It was 
shown that blue-green Algae were the first colonists on the 
pumice and volcanic ash as also on the exposed blocks of rock in 

1 Treub, loc. cit. p. 216. 



Vegetation in 1886 7 

the ravines on the mountain slopes. Investigations made during 
subsequent expeditions demonstrated the association of Diatoms and 
Bacteria with the blue-green Algae. The dark green gelatinous 
layer with which these minute, self-sufficient, and doubtless wind- 
borne organisms covered the pumice and ash formed a favourable 
nidus for the germination of the spores of mosses and ferns and of 
the seeds of such phanerogams as are adapted by their small size 
and weight to dispersal by air-currents. An especially characteristic 
feature of the first stage of colonisation was the preponderance of ferns, 
which were represented by 1 1 species widely spread in the Indo-Malay 
Archipelago ; only two of these, however, belong to the strand-flora of 
the islands. 

In addition to cryptogams phanerogams were also met with on 
the island in 1880, though in comparison with ferns they were at first 
represented by a relatively small number of species and individuals. 
In the Drift-zone of the beach, Treub found seedlings of nine species 
of phanerogamous plants, the seeds of which had germinated on being 
washed up by the sea, also the fruits and seeds of seven other 
phanerogams which, like the former, belong to the strand vegetation 
characteristic of the Malay Archipelago. In the interior and on the 
slopes of Rakata, the number of phanerogams amounted to eight 
species, two of which were identical with those found on the beach. 
The remaining six species, four Compositae and two grasses, plants 
with light fruits some of which were provided with special adapta- 
tions to wind-dispersal were obviously, like the minute spores of 
the cryptogams, transported by air-currents from the neighbouring 
islands to the new land surface of Krakatau. Plants introduced by 
animals or man were not found on the uninhabited and barely 
accessible island. 

The problem of the colonisation or re-stocking of a high volcanic 
island situated far from the mainland was thus solved in a remark- 
able manner by Treub's researches. It was demonstrated that the 
elements of the strand-flora played a very subordinate part in the 
composition of the new flora, a result entirely contrary to what one 
would expect from the analogy of coral islands Avhere these elements 
are the first colonists. The flora of the interior of the island had 
developed not only independently of the strand-flora but also with 
much greater rapidity : the number of species was greater and in the 
case of certain ferns the number of plants was sufficiently large to 
constitute a characteristic feature in the general facies of the 
vegetation. A few phanerogams were first met with as isolated 
plants among the ferns botli on the mountain and on the beach. 

To follow the gradual changes in this new plant-world of the 
island, poor in species and brought together in so remarkable a 



8 Expedition of 1906 

manner, would clearly have been of the greatest interest. A 
thorough investigation of the group of islands planned by Treub 
for the following years had unfortunately to be given up, and it was 
not until ten years later, in March 1897, that the project "was carried 
out, when Treub, Penzig 1 , Raciborski, Boerlage, and Clautriau took 
part in a second exploration of Krakatau. 

During the interval of ten and a half years between the first and 
second expeditions there had been a considerable increase in the 
number of species in both coast and inland floras. In 1897 the total 
number of species found on Krakatau and on the other islands visited 
by the expedition, Verlaten and Lang islands, which in 1886 were 
entirely destitute of vegetation, amounted to 62 species of vascular 
plants, including 50 phanerogams and 12 vascular cryptogams, in 
addition to the seeds and fruits of 26 phanerogamous plants washed 
up on the beach. The assemblage of plants had become denser and 
the ground was in places completely covered; the development of 
characteristic plant-associations (formations) had begun. On all 
three islands the Pes-caprae formation or association formed a 
dominant feature on the beach. Mangrove plants were unrepre- 
sented and the first sign of a strand-forest was noticed only 
on Verlaten island. 

Further inland the vegetation constituted a kind of grass- 
steppe characterised by grasses, occasionally reaching the height 
of a man, which in several places formed a thick jungle. Lower 
grasses grew on the hills and ridges in association with numerous ferns 
and sparse phanerogams. As in 1886 ferns largely predominated on 
the rock surfaces. Shrubs were poorly represented and trees were 
very rare. 

Of the 53 phanerogams found in 1897, Penzig estimates that 
32 species (60*39 %) na 6! reached the islands by ocean-currents, 
17 species (32*07 %) by wind-agency, and only 4 (7'54 %) had been 
transported b} r fruit-eating animals or by man. 



II. The expedition of April 2427, 1906, to the 
Sunda Strait region and to Krakatau. 

In 1905 another visit was paid to Krakatau, in which Th. Valeton, 
M. Golenkin and other botanists took part. The results of this 
expedition have not been published. 

During my residence at Buitenzorg I made application, in company 

1 Penzig, O. " Die Fortschritte der Flora des Krakatau." Annates da Jardin 
bvtanique de Baitenzorg, 1902. Vol. in. ser. 2, pp. 92113. 



Edam Island 9 

with C. A. Backer 1 , the author of a comprehensive "Flora of Batavia" 
which is now in the press, to Professor Treub to organise another 
expedition for the investigation of the Krakatau flora. As the 
result of his kind co-operation the authorities placed at our disposal 
a small coasting- steamer which was then on the point of visiting 
certain places on the coast of the Sunda Strait to relieve the lighthouse 
keepers. The excursion was to last four days and the departure was 
fixed for April 24th. Unfortunately Professor Treub was prevented 
by illness from accompanying us, but we were joined by two botanists 
who happened to be studying in the Buitenzorg botanic garden, 
Dr A. A. Pulle from Holland and Prof. D. H. Campbell of California. 

The plants collected by C. A. Backer and Dr A. A. Pulle in the course 
of our Krakatau excursion, on the island and at different localities 
on the coasts, were determined by the former, who was kind enough to 
undertake the revision and to some extent the identification of the 
vascular plants collected by myself. The list of phanerogams and 
vascular cryptogams which we collected, communicated to me by 
C. A. Backer, will appear either in Verslag van 's Lands Plantentuin 
te Buitenzorg or in the Mededeelingen uit 's Lands Plantentuin te 
Buitenzorg. As a matter of convenience I have arranged the plants 
in the following lists according to families, including the names of 
some species of widely distributed and well known plants of which, 
though no specimens were collected, records were made in my notes 
written on the spot. 

Since the appearance of the German edition of this account 
Dr Pulle 2 and Prof. Campbell 3 have published some of the results 
of their own observations, the former in a detailed abstract of this 
work and the latter in a paper on the distribution of liverworts. 

1. Vegetation and flora of the coral island Edam. 

In beautiful weather on the morning of April 24th, 1906, the "Snip" 
(Snipe) left the harbour of Tandjong Priok to steer a western course 
among the numerous small coral islands scattered along the north- 
west coast of Java. Our first objective was the island of Edam, barely 
12 kilometres distant, which like Onrust, Leyden and other small 
islands outside the harbour of Batavia, was formerly inhabited. To- 
day the European keepers of the large lighthouse and their Javan 

1 Backer, C. A. Flora van Batavia. Deel I. Dicotylcdoncs Dlalypetalae. 
Batavia, 1907. 

2 Bulle, A. A. " De nieuwe flora van Krakatau." Ovcrgedrukt uit De indische 
Merkur, April 21, 1908. 

3 Campbell, D. H. "On the Distribution of the Hepaticae and its significance." 
New Phytoloyist, Vol. vi. p. 203, 1907. 



10 Expedition of 1906 

servants are the only inhabitants. The inhospitable islands with 
their ruined houses and grass-grown streets are the home of a 
dangerous malaria. Swarms of gnats attack the inhabitants at night 
and are troublesome even in the daytime as one wanders through the 
thickets. The strong smell from decaying plants and marine animals, 
the moisture-laden air and almost intolerable heat bear eloquent 
testimony, even after a short visit, to the injurious consequences which 
are bound to follow a longer residence on one of these islands. The 
lighthouse keepers, in spite of a comparatively high scale of payment, 
remain a short time only and return with their families after 1 3 
months service on a long furlough to the healthier climate of Batavia. 
The island is encircled by surf; at the narrow entrance our boat 
bumped against the small stone pier which has been built on the coral 
reef for the convenience of landing. In the course of the repeated 
journeys of the boat necessary to land provisions for the small number 
of inhabitants, also the petroleum for the lighthouse lamp, and the post- 
bags and monthly wages, we had time to explore the island. After 
traversing streets overgrown with tall grass, and passing through a 
small vegetable garden and a plantation of coconut palms to a waste 
piece of formerly cultivated land, we reached the interior and the 
opposite beach, where broad strips of the original vegetation still 
remain. 

On the way we found several specimens of a large arborescent 
euphorbiaceous plant, Pkyllanthns Emblica, draped with tangled 
skeins and thick coils of yellowish green and brown threads. All the 
branches and twigs are covered by a dense network of similar threads 
and the same felted mass hangs from the grasses and herbaceous 
plants growing under the trees. These long threads are the steins of 
a climbing parasitic species, Cassytha Jiliformis, which bears a 
striking resemblance in habit to our native species of Omenta, though it 
is a member of the family Lauraceae, Avhich has no close affinity with 
the Convolvulaceae to which Omenta belongs. The vegetative system, 
like that of Cuscnta, consists of branched climbing shoots bearing 
adventitious roots modified as haustorial organs which attach them- 
selves to the tissues of the hosts. The true roots have disappeared 
and the leaves are reduced to small inconspicuous and functionless 
scales. The reproductive shoots, on the other hand, both flowers and 
fruits, are abundantly developed and occur in large spherical or 
elongated masses. The white fruits are in marked contrast to the 
tangled felt of host and parasite ; birds eagerly eat them and by 
ejecting the seeds contribute in an important degree to the dispersal 
of this interesting member of the strand-flora, which is not as yet so 
completely adapted to a parasitic life as Omenta. It has the power 



Edam, Island 11 

of independent assimilation and grows impartially on nearly all the 
plants of the strand vegetation. The interior of the island is occupied 
by a thicket of various trees and shrubs. With Phyllanthus Embliea 
and PhyUanthus simplex occurs Acalyphe indica, another repre- 
sentative of the family Euphorbiaceae which is rich in halophilous 
species ; also the leguminous plants, Bauhinia Blaucoi and Leucaeuo 
glaum, the young fruits and ripe seeds of which are eaten by natives 
in the Archipelago as a relish with their meals of rice. The ground 
is covered with herbaceous plants, bushes and shrubs, principally of 
the families Gramineae, Cyperaceae, Compositae, Labiatae, and 
Leguminosae. Our guide warned us to be careful in entering the 
bush, as in addition to the large but harmless snake, Pi/thon 
reticularis, which reaches a length of 3 to 4 metres, some smaller 
poisonous species are also met with. 

The south coast of the island is flat and sandy. A broad belt 
is covered with a low and almost shrubless vegetation, of which the 
two characteristic plants are Spinifex squarrosus and Ipomaea Pes- 
caprae. Each of these is admirably adapted to a strand habitat. 
Spinifex squarrosus is a stiff bluish glistening grass with tufts of 
rounded and sharply pointed leaves bound together by tough runners 
hidden in the sand. The low form of growth, the anchoring of the stems 
in the loose sand by deep roots, are adaptations to a habitat exposed 
to frequent and strong winds. 

The conditions, which are unfavourable for vegetative develop- 
ment, have been utilised in a remarkable manner by Spinifex for the 
dispersal of its fruits. The fruiting shoots are very large and com- 
pletely spherical. The spikelets are crowded in the centre of a ball as 
large as a man's head at the base of long stiff axes which spread out on 
all sides like bristles (PL VII., fig. 10). The ripe fruiting shoots fVdl off 
and are rolled as light balls 1 over the sand until they attach themselves 
to other plants or become the sport of the waves. Some of these 
small fruits are detached during the process, while others remain 
fixed to the shoot for a longer period and with it are carried by the 
wind over wide stretches of the beach or transported by currents 
to other islands. Single shrubs and taller herbaceous plants appear 
above the groups of Spinifex squarrosus, Ipomaea Pes-eaprae, and 
Ipomaea Pes-tigridis ; of these the most striking are the abundant 
and handsome plants of Taeea pinnatijida with its two to four large 
umbrella-like leaves and strong reproductive shoots. 

1 Goebel, K. Pflamenbiologische Schilderungen, Bd. i. 1889, p. 135. The 
peculiar method of dispersal of these fruiting branches is well known to the 
Javanese. The Malay name for the plant is djoekoet lari fori, that is "running 
grass" (Miquel, loc. cit. in. p. 474). 



12 Expedition of 1906 

On the north coast trees and shrubs extend to the water's edge or 
even into the water. We found in Edam a mangrove belt poor in 
species, an association not often met with on small coral islands. It 
consists chiefly of species of Rhizophoraceae, Rhkophora coujugata, 
Brugiera gymnorhiza, Brugiera caryophylloides, with two members 
of the Lythraceae, Souneratia alba and Pemphis acidula. 

A considerable area of the interior, formerly under cultivation, is 
now covered with grasses, especially with Imperata artmdinaeea, 
which exceeds the height of a man. By the sides of the paths we 
found several specimens of the common blue-flowered Javan verben- 
aceous species Stachytarplicta bidica and Lantana Camara, the 
inflorescences of which glow with different shades of yellow and red ; 
also numerous Compositae which, like Bideus pilosus, Vemonia 
cinerea, and Wedelia glabrata, occur in all the warmer regions of the 
world, or, like Tridax proeumbens and particularly SynedreUa nodi- 
flora, have spread from the New World over the tropics of the Old. 
The amount of material collected during our excursion, which lasted 
barely two hours, was remarkable. It consisted of 7o phanerogams 
and 2 vascular cryptogams. On the coral reef I was able to collect 
12 different green algae, the commonest being species of Caulerpa, 
Udotea, and Halimeda ; also some red and brown sea-weeds. 

As the composition of the flora on the neighbouring islands is 
probably similar to that of Edam and as our collection is of interest 
from the point of view of comparison with the floras of other coral 
islands such as Schimper 1 and Guppy 2 have described, the list of the 
species obtained on Edam is appended : 

Angiospermae : 

Fam. Compositae: Bidens pilosus L. 

fEclipta alba Hassk. 
Synedrella nodiflora Gaertn. 
Tridax proeumbens L. 
Vernonia cinerea (L.) Less. 
* Wedelia glabrata B. et H. 
Fam. Goodeniaceae : fScaevola Koenigii Vahl. 
Fam. Rubiaceae: fGuettarda speciosa L. 

fMorinda citrifolia L. 
*01denlandia umbellata L. 

1 Schimper, A. F. W. Die indomalayische Strandfl&ra. Jena, 1891, pp. 185 

188. 

2 Guppy, H. B. The dispersal of Plants, as illustrated by the flora of the 
Keeling or Cocos Islands. [See also Guppy, Obser cations of a Naturalist in the 
Pacific between 1896 and 1899. Vol. IL, Plant Dispersal. London, 190b.] 



Edam Plants 



13 



Fam. Labiatae 



Fain. Verbenaceae 



Fam. Borraginaceae : 
Fam. Convolvulaceae : 



Fam. A sclep iadaceae : 
Fam. Myrtaeeae : 
Fam. Rhizophoraeeae 



Fam. Lythraceae: 

Fam. Passijloraceae 
Fam. Sterculiaceae : 
Fam. Malvaceae : 
Fain. Vitaceae : 
Fam. Rhamnaceae : 



Fam. Sapiudaceae : 

Fam. A nacardiaceae 

Fam. Exphorbiaceae . 



Fam. Meliaeeae : 
Fain. Leguminosae : 



*Anisomeles albiflora Miq. 

Leucas linifolia (Roth) Sprang. 
*Ocimmn basilicum L. 
f Clerodendron inerme Gaertner 

Lantana Oamara L. 
fPremna foetida Reinw. 

Stachytarpheta indica Vahl. 
fVitex Negundo L. 
fCordia subcordata Lam. 

Calonyction asperum Cliois. 
f Ipomaea Pes-caprae Sw. [= I. biloba] 
*Ipomaea Pes-tigridis L. 
fHoya spec. 

* Eugenia Jambolana Lam. (?) 
f Brugiera caryophylloides Bl. 
fBrugiera gymnorhiza Lam. 
-f-Rhizophora conjugata L. 
fPemphis acidula Forst. 
fSonneratia alba Smith 
*Passiflora foetida L. 

Sterculia foetida L. 
fThespesia populnea Corr. 
*Vitis trifolia L. 
fColubrina asiatica Brongn. 
*Sageretia oppositifolia Brongn. 
fZizyphus Iujuba Lam. 
*Allophyllus Cobbe Bl. 

Schleichera trijuga Willd. 

Buchanania florida Schauer 
*Acalyphe indica L. 
f Euphorbia Atoto Forst. 
*Phyllanthus Emblica L. 
*Phyllanthus simplex Mull. Arg. 

Ricinus communis L. 
fCarapa moluccensis Lam. 
fAbrus precatorius L. 

Bauhinia Blancoi Baker 
fCanavalia obtusifolia D.C. 
*Crotolaria Saltiana Andr. 
fDesmodi urn triflorum D.C. 
*Indigofera tinctoria L. 

Leucaena glauca Benth. 
*Zornia diphylla Pers. 



14 



Expedition of 1906 



Fam. Lauraceae: 

Fam. Portulacaceae : 

Fam. Aizoaceae : 
Fam. Nyctaginaceae , 
Fam. Amarantaceae : 

Fam. Taccaceae: 
Fam. Pahnae: 
Fam. Cyperaceae : 



Fam. Gfra/mineae: 



Pteridophyta : 
Fam. Polypodiaceae 



fCassytha filiformis L. 
fHernandia peltata Meisn. 
*Portulacca australis Endl. 
fPortulacca oleracea L. 
fSesuvium portulacastrum Willd. 
fBoerhavia repanda Willd. 
*Aerua lanata (L.) Juss. 
fAchyranthes aspera Lam. 
f Tacca pinnatificla Forst 
fCocos nucifera L. 
fCyperus pennatus Lam. 
*Cyperus hyalinus Vahl. 
*Fimbristylis spathacea Roth 

Andropogon contortus L. 

Eleusine aegyptiaca Desv. 

Eragrostis tenella R. et Sch. 

Imperata arundinacea Cyr. 

Paspalum distichum L. 

Paspalum sanguinale Lamk. 
fSpinifex squarrosus L. 
fThuarea sarmentosa Pers. 
fZoysia pungens Willd. 

fPolypodium quercifolium L. 
Polypodium acrostichoides Forst. 
Drymoglossum spec. 



Not less than 36 of the plants (indicated in the list by f) ai'e 
included in Schimper's list 1 of the Indo-Malayan strand-flora as 
typical halophytes, and 19 additional species (distinguished by *) 
belong to genera which include characteristic strand species. In the 
case of the majority of these plants there is no doubt that the seeds 
and fruits are easily distributed by ocean-currents. A smaller number, 
in view of the comparatively short distance between Edam and Java, 
probably owe their introduction also to wind-agency. These are: 
Eclipta alba, Wedelia glabrata, Cyperus hyalinus, Fimbristylis 
spathacea, Polypodium quercifolium, or possibly introduced by 
birds : Scaevola Koenigii, Morinda citri folia, Clerodendron inerme, 
Premna foetida, Vitex Negundo, Allophyllus Cobbe, C assy tha fili- 
formis. 

In addition to the numerous representatives of the Indo-Malayan 
strand -flora, a large number of inland plants have become established 



1 Schimper, A. F. W., loc. cit. p. 100. 



Vlakke Hoeli (Sumatra) 15 

on Edam. Some of these, as Stereulia foct tela, Phyllanthns EmbUca, 
PhyUanthus simpler, Leucaena glauca, Sehleichera trijuga, Ricinus 
communis, and Indigo/era tinctoria, have been introduced by man ; 
others, such as SynedreUa nod [flora, Anisomeles edbiflora, Leucas 
lini/olia, Lcmtcma Camara, and Stachytarpheta indica, owe their 
introduction partly to man and possibly to some extent to birds. The 
two ferns, Poly podium acrostiehmdes and Drymogtossum sp., some 
of the Composites, Bidens pilosus, Trida.a procmnbens, and Vernonia 
einerea, the fruits of the grasses Andropogon eontortus, Eleusine 
aegyptiaea, Eragrostis tenella, Imperata arundinacea, Paspalum 
distich urn, and Paspcdum sanguincde were carried by wind from the 
neighbouring- mainland of Java. The flora of the other formerly 
inhabited islands off the harbour of Batavia, like that of Edam, is 
probably composed of typical strand-plants and introduced inland 
species ; while in the case of the more distant islands, like that of the 
Thousand Islands, some of which were visited by Schimper, the whole 
flora has been built up of species from the strand-formation of Java. 
The next stage of our voyage lay in the region of the Thousand 
Islands. Our steamer touched at the island of Pajoeng, 2."5 kilometres 
[15^ miles] distant, surrounded by the islands of Horn and Agenieten 
and situated about 20 kilometres from the coast of Java. On the most 
easterly of the three islands, which is encircled by a coral reef 100 
metres [328 ft.] wide, there is a lighthouse and some dwellinghouses. 
A low mangrove swamp, which reaches into the water, stretches 
along the coast in an easterly direction ; towards the west, the dark 
Barringtonia forest, diversified by grey-green Casuarinas, forms a 
background to the sandy shore overgrown with Ipomaea, Spiuifex, 
and Yigna lutea, which afforded a rich harvest of large and many 
coloured shells. 



2. On the beach at Viable Hoeli (Sumatra). 

Before nightfall we reached Poeloe Babi, a larger island with a 
wooded coast, and during the night the steamer passed between the 
islands of Sebesi and Seboekoe towards the coast of Sumatra. On the 
following morning before sunrise the " Snip " lay off the lighthouse- 
station Ylakke Hoek on the southern point of the most westerly of the 
three Southern Sumatran peninsulas. The iron tower, GO metres in 
height, rose above the sombre forest fringing the coast line. When 
the flood of August 2/th, 1883, swept over the flat beach, 103 kilo- 
metres [64 miles] distant from Krakatau, to a depth of 15 metres, 
the tower withstood the force of the waves ; the neighbouring 
structures of stone and iron were on the other hand destroyed, 



16 Expedition of 1906 

beams and pieces of iron being found afterwards at a considerable 
distance among the wreckage of the overthrown trees. 

Even to-day the vegetation of Vlakke Hoek still bears traces 
of the devastation which occurred 25 years ago. A new forest of 
coconut palms has sprung up in the neighbourhood of the small 
settlement. Part of the devastated cultivated land is covered with 
Imperata arnndinacea, the Alang-Alang grass widely distributed in 
the Archipelago, which everywhere spreads as a thick carpet over 
bare patches of forest and neglected fields and slowly retreats before 
new forest growth. 

The beach of Vlakke Hoek (Tandjong Rata of the natives) is flat 
and sandy. Towards the east the shore is fringed by a large rect- 
angular coral reef, on the outer edge of which the waves break into 
foam. Unfortunately the rising tide interfered with algological in- 
vestigations which, judging by the interesting finds on the beach, 
would probably have yielded a rich harvest. 

There is no mangrove vegetation in the neighbourhood of Tandjong 
Rata. Spinifex and Barringtonia formations alternate with one 
another. In many places the waves rush over the fine sand to the 
half-exposed network of roots of the outermost trees of the strand- 
forest. Where the forest is further from the coast larger and smaller 
patches are covered with Spinifex squarrosus and Ipomaea Pes- 
caprae ; shrubs of Hibiscus tiliaceus are met with, also Hernandia 
peltata, Colubrina asiatica, and Toumefortia argentea with its 
shimmering grey-green leaves. Below the low trees and shrubs of 
the Leguminous species Desmodium umbellatum, Pongamia glabra, 
Sophora tomentosa, one finds the beautiful flowering grass Thuarea 
sarmentosa ; also other members of the Gramincae, such as Zoysia 
pnngens and Oplismenus compositus, the Cyperaceous species Fim- 
bristylis spathacea, some ferns with singly pinnate leaves, Nephrolepis 
hirsutula and large clumps of Acrostichiwi aureum. The parasite 
Cassytha flifqrmis occurs on a variety of shrubs and herbaceous 
plants. Scaevola Koenigii, a Goodeniaceous species with tufts of 
fleshy light green leaves terminating long branches, grows in 
abundance, also crowded young plants of Terminalia Gatappa 
characterised by their formal habit. Groups of Barringtonia 
speciosa present a strange appearance. Numerous trees lie partly 
uprooted with the stem on the ground, the crown half-erect. These 
are veterans overthrown by the seismic wave of 1883 and which have 
preserved themselves in the midst of the subsequent growth : their 
thick stems and branches are overgrown by a thick mantle of small 
epiphytes, lichens, liverworts, and mosses, in contrast to the other 
strand-plants which are destitute of epiphytic species. Bushes of 



Vlcikke Hoeh Plants 



17 



Crinum asiaficwn, a handsome amaryllidaceous plant with long leaves 
and a wealth of white flowers, grow in the clearings. Tall Pandanus 
trees with dense crowns and sharp-pointed leaves present a fantastic 
appearance on the beach. The lower conically pointed ends of their 
stems are supported by prop-roots which spring from them at a height 
of 1 2 metres above the surface of the ground and spread obliquely 
outwards to the soil, while some of the younger adventitious roots, 
1 5 cm. in diameter, have not yet reached the ground. The tissue 
of these younger roots is exceedingly soft and full of water (peripheral 
layers of cork prevent excessive loss of water) and their bluntly conical 
apices are protected against injury and drought by a massive root-cap 
composed of several thin layers of tissue. Two hours only were avail- 
able for an exploration of the neighbourhood of the lighthouse. At 
nine o'clock we returned with our spoil to the boat. I append a list 
of the vascular plants collected (38 phanerogams, 4 ferns) : 



Fam. Compositae : 
Fam. Goodeniaceae 
Fam. Rubiaceae : 

Fam. A can thaceae : 
Fam. Verbenaceae : 



Fam. Borraginaceae . 
Fam. Convolvulaceae 
Fam. Myrtaceae : 

Fam. Combretaceae : 

Fam. Guttlfcrae : 

Fam. Stereuliaceae : 

Fam. Malvaceae : 

Fam. Vitaceae: 

Fam. Bhamnaceae: 

Fam. Sapindaceae : 



Fam. Leguminosae 



Fain. Lauraceae 



*Wedelia glabrata B. et H. 
fScaevola Koenigii Vahl. 
fGuettarda speciosa L. 
*Ixora paludosa Boerlage 

* Eranthemum diversifolium Miq. 
Lantana Camara L. 

f Premna foetida Reinw. 

Stachytarpheta indica Vahl. 
f Tournefortia argentea L. 
flpomaea Pes-caprae Sw. 
fBarringtonia speciosa Forst. 

* Eugenia formosa Wall. 
fTerminalia Catappa L. 
fCalophyllum Inophyllum L. 

* Pterospermum acerifolium Willd. 
f Hibiscus tiliaceus L. 

*Vitis lanceolaris Wall. 
fColubrina asiatica Brongn. 
*AUophyllus Cobbe Bl. 
Aphania montana Bl. 
fDodonaea viscosa L. 
*Crotalaria Saltiana Andr. 
f Desmodium umbellatum D.C. 
fPongamia glabra Vent. 
fSophora tomentosa L. 
fCassytha filiformia L. 
fHernandia peltata Meisn. 



18 



Expedition of 1906 



Fam. Moraceae: 
Fam. Casuarinaceae : 
Fam. Amaryllidaceae 
Fam. Flagellariaceae : 
Fam. Cypcraceae : 
Fam. Gramineae : 



Fam. Pandanaceae : 
Fam. Polypodiaceae 



*Ficus Leucantatoma Poir. 
tCasuarina equisetifolia Forst. 
fCrinum asiaticum L. 
fFlagellaria indica L. 
*Fimbristylis spathacea Roth 

Imperata arundinacea Cyrill. 

Oplismenus compositus Beauv. 
fSpinifex squarrosus L. 
fThuarea sarmentosa Pers. 
fZoysia pungens Willd. 
*Pandanus spec, 
f Acrostichum aureum L. 

Aspleimm nidus L. 

Nephrolepis hirsutula Presl $> 

Lygodium dichotomum Swartz 

The flora of Tandjong Rata, as the foregoing list shows, consists for 
the most part of typical halophytes. Not less than 22 of the 38 
phanerogams are included in Schimper's list of the Indo-Malayan 
strand-flora, and 11 other plants, belonging to genera which include 
species of Indo-Malayan strand-plants, may probably be reckoned as 
additional members of the strand-flora. Only eight of the vascular 
plants enumerated, three of which are ferns, have their chief centre 
of distribution in the interior. 

The old Barringtonia stems supported an epiphytic flora consisting 
of small mosses, liverworts, and lichens. The determination of these 
and the other cryptogams collected in the course of the Krakatau 
excursion was kindly undertaken by Prof. V. F. Brotherus (mosses), 
Prof. V. Schiffuer (liverworts), Prof. A. Zahlbruckner (lichens), Prof. 
P. Lindau (fungi), and Dr E. De Kruyfl" (bacteria). I take this 
opportunity of expressing my cordial thanks to these botanists. 

The small epiphytes on the Barringtonias of Vlakke Hoek in- 
clude : 



Musci : 



Hepaticae 



LlCHENES 



Trichosteleum hamatum Dz. et Mb. 
Calymperes Hampei Dz. et Mb. 
Hyophila Micholitzii Broth. 
Cheilolejeunea parvula Schifth. n. sp. 
Microlejeunea cucullata (Reinw., Bl. et Nees) St. 
Acrolejeunea integribractea Schifth. 
Lopholejeunea spec. 
Parmelia perforata Ach. 
Parmelia relicina Fr. 
Physcia spec. 



Sunda Strait: Winds and Currents 19 

3, In the Sunda Strait: winds and ocean-currents. 

On the same day we had an opportunity of botanising on another 
rarely visited locality of the Javan coast. The " Snip " steamed across 
the Sunda Strait at its broadest western part to the most westerly 
promontory of Java, "Java's First Point." In a strong wind and 
rough sea this passage in a steamer of only 300 tons was the reverse 
of pleasant and put the passengers to a severe test. The sky fortu- 
nately remained partially overcast and the temperature was bearable. 
During the night the thermometer sank to 27 C. and at midday in 
the shade registered only 29 G C. The preparation of the algae, 
which we had collected, and the work of drying the plants on the 
narrow deck of the rolling and pitching boat were carried out under 
difficulties. Even Sahib, my industrious servant and a seasoned 
traveller, at last found his accustomed duties no longer "enak" 
(palatable), and we followed the example of the others who had long- 
ago stretched themselves on chairs and forms in their endeavours 
to resist with more or less success the effects of the pitching and 
tossing of the ship. 

We were now (the Krakatau group lies approximately 105 25' 
east long, and 6 10' south lat.) in the middle of the equatorial belt of 
the monsoon disturbances both in the atmosphere and the water. A 
strong south-east monsoon drove the waves directly against us. As 
the boat steered her course against wind and waves towards the next 
port of call, the captain, Mr Nix, who had for many years made 
three voyages a month in his small coasting steamer in the Sunda 
Strait, visiting twenty-one lighthouse-stations on the north coast of 
Java and on the neighbouring coasts of Sumatra and Borneo, 
courteously gave us information as to the winds and currents in the 
Java Sea and especially in the Sunda Strait. The following details in 
regard to the air- and sea-currents, which are of the greatest import- 
ance from the point of view of the history of plant-colonisation of the 
Krakatau islands, are based in part on information supplied by Mr Nix 
and are extended and confirmed from data published in the sailing- 
handbook of the German Admiralty 1 and from other sources 2 . 

The south-east monsoon begins, in the wider regions of the Sunda 
Strait, on the north and south coasts of Java and in South Sumatra, 

1 Neumayer, G. (Direction der deutschen Seewarte.) Segelhandbuch fur den 
indischen Ozeav. Hamburg, 1892. 

- Neumayer, G. Ardeitung zn wisseuxcluiftlichen Beobachtungen auf Reisen. 
in. Autt. 1906. 

Hunn, J. Handbuch der Klimatologie. n. Bd. Stuttgart, 1897. 

Boguslawski, G. v., and Kriimmel. Handbuch der Ozeanographie. I. Bd. 1884. 
II. Bd. 1898. 

22 



20 Expedition of 1906 

during the month of April; during May it increases in force, 
reaching its maximum from June to September. The direction of 
the wind does not remain constant during this period but oscillates 
principally between south-east and east. The high steep coasts of 
Java, which extend in a north-westerly direction close to Sumatra 
and considerably reduce the breadth of the strait, frequently screen 
the strait and Sumatra from the south-east monsoon and a westerly or 
south-westerly wind takes its place. The south-east monsoon brings a 
fine season with prevailing dry weather and comparatively light 
winds. At the period of its maximum force, especially in July and 
August, the average strength of the wind reaches 3 degrees Beaufort 
(5'5 met. per second) ; stronger winds of 6 to 7 degrees Beaufort (13*5 
to 16*5 met. per second) are rare in the Sunda Strait area and in the 
more northerly region to which the data given in the following tables 1 
refer. 

The change of monsoon occurs between September and November ; 
it is introduced by the occurrence of southerly and westerly winds. 
The season of the typical north-west monsoon (which is the north- 
east monsoon deflected by the earth's rotation after crossing the 
equator) begins in November and lasts until March. This brings bad 
weather ; the rainfall increases in amount and reaches its maximum 
in January and February. The direction of the wind (table, p. 22) 
oscillates from west to north-north-west : its average force being 
approximately that of the south-east monsoon, about 3 degrees 
Beaufort. Tn the ship's log an intensity of 1 3 occurs frequently ; 
more rarely, for a period of several days, 5 6 and exceptionally 
an intensity of 7 is recorded (see the accompanying table). At the 
end of March or in April there is another change of monsoon. There 
is no prevailing direction for the winds of this period (table, p. 22) : 
winds blowing irregularly from all points of the compass alternate 
with calms, sudden gusts of wind and cyclones. At all seasons the 

1 Seyelhandbuch fur den indischen Ozean, p. 56. The scales for wind-velocities 
most commonly used are the Beaufort scale of twelve divisions (0 = calm, 12=hurri- 
cane) and the six- and ten-division scales derived from it. According to the most 
recent researches (Hann, J., Lehrbueh dor Meteorologie, Leipzig, 1901, pp. 376, 377) 
the following wind-velocities correspond, on an average, to the following values for 
wind-intensity according to the twelve-division Beaufort scale : 
Beaufort intensities 

(estimated): 1 2345 6 7 8 9 10 11 12 

Average velocity in 
metres per second 
(after Koppen): 1'7 31 4'8 67 3*8 10*7 129 154 180 210 26 4050. 

On reduction to the 10-di vision scale used above: 
Estimated intensity (010 Beaufort): 1 2 3 4 5 6 7 8 9 10 
metres per second : 2 3"5 5\5 8 105 135 16'5 225 28 30 



Winds in Stinda Strait 



21 



Frequency of the different wind-intensities (Beaufort) in the Java Sea region. 













Average of 

the values 

recorded 










* 


Lat. 


Long. 










*H '.IS 

s? 

^ o 


Average wind- 
intensity 





1 


2 


3 


4 5 


6 


7 


8 


9 


10 


South 


East 






January and February 






03 8. Lat. 
37 s. Lat. 


106 no 1 

107 119 2 




6 



6 


6 I 14 
15 31 


10 

8 


4 I 
7 j 5 


2 


| 




34 
80 


3-4 
3 










July and August 






03 s. Lat. 
37 s. Lat. 


106110 
107119 


10 
15 




7 


16 
15 


27 1 21 
38 | 31 


3 1 
13 | 1 


1 


1 




78 
120 


2-8 
3-0 



1 Karima Strait between the west coast of Borneo and the east coast of Billiton. 

2 Java Sea north of Sunda Strait. 

direction of the wind may change every day and it may happen that a 
southerly wind in the forenoon may shift to the north in the afternoon, 
with a short spell of calm between. 

In addition to the monsoons, storms, of which the lower limit of 
velocity reaches 17 to 23 metres a second, are not uncommon. During 
a hurricane the velocity rises to 30 or even to 60 metres a second. Of 
shorter duration and affecting a smaller area are the squalls, sudden 
gusty winds, which occur on the mountainous coasts of South-east 
Sumatra and West Java, as in other regions of the Indian Ocean, es- 
pecially in the monsoon period, with greatest frequency from February 
to April. The currents in the Sunda Strait are dependent on the winds. 
They are, however, of the nature of periodic currents. The direction of 
the current changes daily and during 24 hours there is only one change ; 
the northerly current brings high tide and the southerly current low 
tide. The influence of the prevailing wind is generally shown by the 
fact that during the south-east monsoon the ebb-current flowing to- 
wards the south-south-west is stronger both in duration and in in- 
tensity, while during the prevalence of the west monsoon on the other 
hand the flood-current running towards the north-north-east prevails. 

During the east monsoon, from May to October, the tide flows 
strongly for 18 hours continuously towards the south-west, during the 
next 6 hours with less force towards the north-east, or there may be a 



22 



Expedition of 1906 



Percentage frequency of the winds in the Sunda Strait district. 
(010 S. Lat. and 100105 E. Long.) 



Month 


Latitude 


K 








H 




m 


m 

02 


cc 


02 
02 


02 


02 


















Calms and 
Light Winds 


.2 

0) & 

r* 


Jan. 


5 S. 
5 10 S. 


20 

4 


4 


4 




















8 


8 
2 


16 


4 
24 


20 
15 


16 
22 


16 
17 


61 

5 


65 

57 


Feb. 


5 S. 
5_10 S. 


2 


2 


2 











2 








2 


3 
2 


3 
11 


3 
36 


20 
19 


52 
24 


13 

4 


40 
38 


70 
86 


March 


5 S. 
5 10 S. 


11 

2 


3 
1 


1 
5 


1 
9 


1 
11 


5 


5 





3 

2 
3 


1 
2 

2 
1 


3 
10 


6 

4 


16 

9 


21 
17 


20 
14 


13 

6 


39 
67 

73 

51 

70 
67 


208 
368 


April 


5 S. 
5 10 S. 


2 

4 


6 


4 


3 

8 


20 


2 
5 


2 
1 


2 


13 

7 


18 

5 


12 

3 


22 

17 


7 

io 


15 

4 


251 

482 


May 


5 S. 
5 10 S. 








1 
2 


4 
6 


15 
18 


11 
15 


17 
20 


2 
4 


25 

4 


9 
3 


4 
4 


2 
5 


6 
1 


2 
2 


1 
15 


1 
1 


414 

483 


June 


5 S. 
5 10 S. 


2 


1 


7 


5 

8 


3 
25 


10 
13 


37 
16 


11 

2 


5 
3 


10 
2 


G 
6 


1 

2 


7 
4 


3 
4 


2 
3 



2 


61 
59 


290' 

718 


July 


5 S. 
5 10 S. 


2 


1 

1 


1 


2 

8 


26 
19 


19 
25 


27 
12 


11 

3 


8 
4 


2 
5 


2 

1 


1 
2 


5 


4 


6 


2 


43 
56 


453 

751 


August 


5 S. 
5 10 S. 


1 


2 


2 
3 


4 
2 


20 
16 


22 
30 


29 
21 


8 
7 


4 
5 


8 
4 


7 


1 


1 


1 


2 





46 
47 

45 
48 


273 
486< 

366 
4164 


Sept. 


5 S. 
5 10 S. 





1 


1 


2 
3 


16 
34 


23 
26 


24 
17 

31 
35 


6 
3 

6 
2 


14 

6 


5 
2 


8 
4 


1 


2 

1 





1 





Oct. 


5 S. 
5 10 S. 


2 








6 
3 


18 
14 


11 
30 


10 

7 


9 

7 


4 
2 





2 





1 





64 

35 


276 
224< 

108* 

54 


Nov. 


5 S. 
5 10 S. 


2 


2 


2 


4 


22 


23 


6 


15 


1 


6 


4 





3 


3 


3 


4 


37 


Dec. 


5 S. 
5 10 S. 














21 


32 





'5 











5 


11 





26 





48 



[The numbers in thinner type in the above table denote that more than J (17 / ), the underlined 

numbers denote that more than J (33 / ) of all the winds come from one direction.] 

(From the Segelliandbuch fiir den indischen Ozean, p. 556.) 



Plate III 




Photo. A. Ernst. 



Fig. 1. View of Krakatau from the North (p. 26). 





MM 3Ie9 5bJ """ -^- 


" . 








i 


' ' ' > 


^^^| 












1at" "'ShHI 


tjV?." - ' <. .-.." I 


o V 


. r v" -$1 ^Jk- : ./,' 


j^? H 






*. 








~ 


1 


-.-_.,'' . 



Photo. A. Ernst, 

Fig. 2. Peak of Rakata (832 m.) and the fractured rock-face (p. 33). 



Java's First Point 23 

calm. On the other hand, during the months of the west monsoon, 
from December to February, the tides set strongly for about 18 hours 
towards the north-east and flow only for (3 hours with a feeble current 
towards the south-west. 

In the daytime the prevailing flow is interrupted by currents 
in the opposite direction or by calms ; at night the flow is continuous, 
reaching its maximum force at the time of new and full moon and its 
minimum at the quarter moon. During the intermediate period, 
November, March, and April, and at other times when the wind 
conditions are less strongly marked, the differences in duration and 
force of the two flows tend to disappear. 

The general direction of the currents is north-east and south-west, 
but local variations occur depending on the form of the coast-line. 
The direction is north-north-east and south-south-east at the northern 
entrance to the strait on the coast of Sumatra between North island 
and Strom Rock (Stroomklip), also on the coast of Java between 
Third and Fourth Point (derde punt and vierde punt); between 
Krakatau and Prince island (Prinsen Eiland) east-north-east and 
west-south-west, between Seboekoe and Hogspitze (Varkens Hoek) 
east-south-east and west-north-west. On the whole the current flows 
in the Sunda Strait throughout the year much more in a south- 
westerly than in a north-easterly direction. During the east monsoon 
the deflexion of the south-west current towards the north-east current 
is not infrequently so strong that, as the result also of the prevailing 
light winds of this season, sailing ships going north are delayed for 
days or are driven back into the strait {Segelhandbueh, p. 567). 

The current sets strongest in the northern entrance to the strait, 
where its velocity frequently exceeds 5 kilometres per hour ; in the 
broad channel between Krakatau and Prince island a velocity of 
3 4 km. is not uncommon, but on an average it is only 1*5 2 km. ; 
in the Prince Chamiel and on the Javan coast from the Second to the 
Fourth Point the current is considerably weaker, at least that which 
flows in a south-westerly direction. 

4. On the south-west const of Java : " Java's First Point." 

About three hours after leaving Vlakke Hoek we were in the 
middle of the Sunda Strait ; the peak of Krakatau was visible towards 
the east, rising above heavy clouds. Our next destination lay still 
further south. At 3 o'clock we sighted the coast of Java and in front 
of it Prince island. We were soon in calm water behind Prince 
island and reached the calm bay which is enclosed by the coast 
of Java and the small Gull island "Meeuwen Eiland." We had 



24 Expedition of 1906 

a glorious view of the wooded high ground and of the cone of Goenong 
Pajoeng, 470 metres high. 

On a rocky headland 40 metres high the masonry of the light- 
house, visible even in the daytime for a considerable distance, rises 
in front of us against a background of the dark green edge of the 
forest. Rather more to the left a solitary storehouse stands on the 
beach and next to it are the ruins of a large fort with its foundations 
projecting far into the water. It was to this wall that our boat 
brought us through the surf about 4 p.m. We were allowed to remain 
on shore collecting until sunset. The captain had taken the pre- 
caution to provide us with arms and ammunition from the ship's 
armoury, as tigers and rhinoceroses are still plentiful in the outlying 
parts of West Java. We endeavoured to ensure a safe passage through 
the dark strand-forest and the adjacent grass thickets by repeatedly 
firing our guns. 

Ipomaea Pes-ca/prae sprawls over the ground at the landing-place ; 
there are large bushes of Hibiscus tiliaceus, Scaevola Koemgii, and 
Touruefortia argentea in flower. Ischacmum muticum and Euphorbia 
Atoto, with Wedelia glabrata, Ageratum conyzoides and other Com- 
posites grow beneath tall plants of Galophyllum draped with the thick- 
leaved Hoya. Stout rhizomes of Polypodiwm quercifolium bearing 
two forms of leaf, bracket-leaves with the habit of large oak leaves 
alternating with simply pinnate fertile fronds, creep over stems and 
branches. The older parts of the rhizomes bear numerous and crowded 
brown skeletons of the hunius-collecting bracket-leaves, while the 
younger portions bear only ordinary fronds. Spiny Rotangs and low 
Pandanus plants render penetration into the interior difficult, where 
Saceharum spontanewm, various Cyperaceae, and ferns cover the 
ground ; tree stems and large blocks of coral rock, which had been 
swept by the flood of 1883 to a distance of several hundred metres on to 
the land, are decked with creeping and climbing plants. Nephrolepis 
exedtata occurs both as an epiphyte and growing in the ground; the 
plants of the undergrowth are overgrown by Lygodium diehotomum 
with its deeply palmate leaf segments. Aerides odorata and a Zingibe- 
raceous species, Costus speciosus, are conspicuous by the brightness of 
their flowers. The 36 vascular plants (32 phanerogams and 4 ferns) 
which we took back with us to the ship are enumerated in the following 
list: 

Fam. Compositae: Ageratum conyzoides L. 

*Blumea balsamifera D.C. 

Vernonia cinerea Less. 
* Wedelia glabrata B. et H. 



Javan Plants 



25 



Fain. Goodeniaceae 
Fain. Rubiaceae : 
Fain. Verbenaceae : 



Fam. Borraginaceae : 
Fam. Couvolvulaceae : 
Fam. ^i sc'/c/> ladaceae : 
Fam. Apoeynaeeae : 
Fam. Li/thraceae : 
Fam. Gutti/erae : 
Fam. Dilleniaceae : 
Fam. Malvaceae : 
Fain. Vltaceae : 

Fam. Euphorbiaceae : 
Fain. Legtiminosae : 

Fam. Orchidaceae : 
Fain. Zingiberacme : 
Fam. Amaryllidaceae 
Fam. Liliaceae : 
Fam. Cyperaceae : 



Fam. Gramineae : 

Fain. Pandanaceae : 
Fam. Sehizaeaceae : 
Fam. Polypodiaceae 



fScaevola Koenigii Vahl. 

Sarcocephalus cordatua (Roxb.) Miq. 

Gmelina villosa Roxb. 
fVitex pubescens Vahl. 
*Vitex Neguudo L. 
fTournefortia argentea L. 
flpomaea Pes-caprae Sw. 
*Hoya spec. 
fCerbera Odollam Gaertn. 

Lagerstroemia speciosa Pers. 
fCalopliyllum Inophyllum L. 
*Tetracera Assa D.C. 
f Hibiscus tiliaceus L. 

Leea sambucina Willd. 
*Vitis arachnoidea Backer 
f Euphorbia Atoto Forst. 
f Desmodium umbellatum D.C. 
fSophora tomentosa L. 

Aerides odoratum Lour. 

Costus speciosus Smith 
fCrinuin asiaticum L. 

Smilax spec. 
fCyperus brevifolius Valck. Sur. 
fCyperus cyperiims Valck. Sur. 

Cyperus umbellatus Benth. (Mariscus uni- 
bellatus Vahl.) 
f Ischaemum inuticuni L. 

Saccharum spoil taneum L. 
*Pandanus spec. 

Lygodium dichotomum Swartz 

Nephrolepis exaltata Schott 
*Polypodium quercifolium L. 

Pteris longifolia L. 



The flora in the neighbourhood of Java's First Point is essentially 
different in composition from that of Tandjong Rata (Sumatra) and 
Edam. The 36 species belong to no less than 24 different families. 
The marked decrease in the number of typical strand-plants is a 
particularly striking feature. 

While in the Edam flora the halophytes constitute 46 %> or > 
including the species indicated by *, 72 % f the total, and in Vlakke 
Hoek they constitute 57 / , or, with the additional species, 83 / of the 
total number, only 14 (39 / ) of the 36 plants obtained from Java's First 



26 Expedition of 1906 

Point, or, with additional species (* in the list), 21 (that is 58 / ) belong 
to the Indo-Malayan strand vegetation. The 15 remaining species 
belong to plants characterised by a wide distribution-area. The Compo- 
sites Ageratvm coiit/zoidcs and Vernonia cinerea inhabit the warmer 
regions of the world ; Sarcocephalus cordatm, Lagerstroemia speciosa, 
Tetracera Assa, and Leea sambucina extend from Further India to 
South China, from the Malay Archipelago to the Philippines and to 
Australia; similarly Aerides odoratum, Saccharum spoutaneum and 
Cyperm umbellatus are widely spread over Java and Sumatra and 
far beyond them. It is, therefore, not surprising that we afterwards 
found in Krakatau as many as six of these 15 inland plants, the 
wide range of which is clearly connected with the adaptation of 
their seeds and fruits to dispersal. 

As we returned to the steamer at six o'clock the sun was setting 
behind the lighthouse, the red sky glowing with brilliant colour, 
above the calm waters of the bay encircled by the sombre forest. 
The nocturnal life of the forest was awake ; bats of all sizes fluttered 
through the air, flying foxes (Kalong) passed noiselessly with slow 
flight over the bay in search of fruit, The screams of monkeys 
resounded in the forest, the wild boars were astir in the Alang-Alang 
thickets, while tigers, panthers, and wild cats slunk out of their hiding- 
places in search of prey. 

The "Snip" remained at anchor till midnight off Java's First 
Point. We spent the first part of the welcome leisure in arranging 
and pressing our collection of plants and afterwards enjoyed a well- 
earned rest in the deck-chairs. As the ship left the sheltered bay and 
steamed into the open Sunda Strait between Prince island and Java 
our rest was interrupted; the rolling began afresh and the waves 
breaking over the deck compelled the sleepers to beat a hurried 
retreat to the narrow and close cabin. 

5. On Krakatau and Verlaten island. 

At dawn on April 26th our steamer was slowly approaching the 
Krakatau group. Krakatau, the object of our voyage, with its 
characteristic volcanic shape, stood out a short distance ahead. The 
precipitous face reaching from sea-level to the summit of the fractured 
cone is a conspicuous object (PL III.). Towards the south-east the half- 
conical mountain slopes steeply to a flat base, in front of which is a 
small and level beach. Lang island lies to the right of Krakatau and 
Verlaten island is visible between them. Further to the right, in a 
north-easterly direction, we can see the high wooded islands of 
Sebesi and Seboekoe and the mountains of Sumatra, and to the south- 
east the Javan coast. 



Plate IV 








Photo. A. Ernst. 

Fig. 3. Drift-zone on the south-east coast of Krakatau. 

Strand-forest in the background (p. 27). 




Photo. A. Ernst. 

Fig. 4. Level beacli between the fractured rock-face and the promontory of 

Zwarte Hoek. 

In the foreground the long creeping shoots of Ipomaea Pes-caprae 
and Vigna lutea (p. 34). 



Flora of Krakatau 27 

As we approached the east coast of Krakatau we noticed with 
growing amazement the remarkable progress made by the vegetation. 
Almost the whole south side, from the beach to the summit and 
to the edge of the steep promontory, is covered with green. On the 
south-east coast, where we first thought of landing, a belt of forest 
runs parallel to the shore in which we could recognise from a distance 
numerous grey-green Oasuarina trees. Further to the south rose the 
dark green leaves of coconut palms in association with slender broad- 
leaved trees bearing whorls of branches. Isolated trees and shrubs 
were seen on the low-lying ground which rises gradually to the base 
of the conical mountain ; in some of the ravines half-way up the hill 
they form patches of forest, reappearing as scattered plants on the 
higher ridges and on the peak. 

At six o'clock the anchor was let go and after waiting impatiently 
we took the boat over the pumice-strewn water to the level beach. 
Here at the upper limit of the tide-swept zone (PI. IV., fig. 3) we 
examined the material which the waves are constantly throwing up 
on to the desolate shore. Amongst the debris of tree stems and 
broken branches, with which the beach is covered, blocks of coral of 
all sizes are scattered over the loose surface of pumice, in which one 
sinks ankle-deep at each step, mixed with brown sea-weeds, broken 
univalve and bivalve shells and green balls of algae. Fruits and seeds 
of land-plants are mixed in abundant variety with the flotsam of the 
waves : the cases of many of them, decayed beyond recognition or 
completely rubbed off, afford striking evidence of a long and stormy 
voyage. Some, on the other hand, are absolutely fresh, as if recently 
fallen from the tree. 

Several of the fruits have germinated and are anchored by long 
tap-roots to the ground ; others have been bored or completely 
hollowed out by animals, particularly those of the coconut, the 
largest of the drift-fruits. The ovate fruits of Cerbera Odottam, 10 cm. 
[3'9 inches] in length, are met with in abundance ; the outer coat has 
usually been removed, laying bare the loose floating tissue consisting 
of a felted mass of slender fibres. The brownish-black ribbed fruits 
of a strand-palm, Nipa fniticaus, frequently occur ; also the 
irregularly angular seeds from the golden yellow fruits of Carapa 
which reach the size of a man's head, single fruits and pieces 
of the inflorescence of Pandanus, the large four-sided fruits of 
Barriugtonia speclosa, the flat boat-shaped kernels of Term'malia 
Catappa, spherical fruits of CalophyUwn, the drupe-like seeds of 
Cycas, and many other large and small fruits and seeds. On the 
previous day we had collected almost the same set of fruits and seeds 
on the shores of the coral islands Edam and Pajoeng in the Java 



28 Expedition of 1906 

Sea or from the different localities which we visited on the coasts of 
Java and Sumatra. They all belong to strand-plants which are not 
confined to the coasts of Java and Sumatra and the numerous islands 
in the Java Sea or to the Malay Archipelago, but are widely dis- 
tributed from Africa to New Guinea, some species being met with 
throughout the whole of the tropics. It is these plants which 
constitute the first colonists of recently formed coral reefs and 
islands. They owe their lightness and buoyancy to air-spaces in the 
pericarp and testa or to the abundance of light floating tissue, while 
a hard and impervious inner coat affords protection to the embryo 
against the injurious effects of sea- water. It is by virtue of these 
features that the seeds and fruits of strand-plants are widely distri- 
buted and act as the pioneers of vegetation on land recently raised 
above sea-level. 

The species which we found in the new strand-flora of Krakatau 
are typical strand-plants. Within the Drift-zone we came to a low 
carpet of a tropical dune-flora, the Pes-caprae formation, as it has 
been called by Schimper, forming a zone in front of the forest-belt 
which varies in breadth according to the nature of the ground. We had 
previously met with the most striking and important representatives 
of this formation on the sandy littoral of Edam. Here, as in Edam, 
the runners of Spinifex squarrosus and the long trailing shoots of 
Ipotnaea Pes-caprae 1 rooted at the nodes and bearing large funnel- 
shaped flowers of a blue-violet colour and thick fleshy leaves form 
a network on the loose substratum. With these are associated shoots 
of some Leguminous species clinging close to the ground, the yellow- 
flowering Vigna Intea and Vigna lutcola and the large-leaved 
Canavalia obtusifolia. Here and there tall grasses and Cyperaceae 
rise above the regular network of creeping steins, a spurge, charac- 
terised by waxy glaucous leaves and low bushes becoming taller and 
more abundant as we approached the forest-belt. We found several 
old acquaintances from Edam and Vlakke Hoek, the widely spread 
Malvaceous species, Hibiscus tiliaceus, with its beautiful yellow 
flowers, also Scacvola Koeuigii, Clerodeudrou inerme, and Premna 
foetida ; a thick felt of the yellowish- green cylindrical threads of 
CassytJm filiformis, assuming a brown-red colour in sunny places, 
covered the grasses, herbaceous plants and bushes as well as the 
branches of the taller shrubs and trees of the neighbouring strand- 
forest (Plate V., fig. 6; PL VI., fig. 7). 

The young strand-forest of Krakatau which stretches beyond the 
low zone of the Pes-caprae formation, and is still characterised by 

[ x Compare an account of the Flora of the Ceylon littoral by A. G. Taasley and 
F. E. Fritsch published in the New Phytdogist, Vol. iv. p. 1, 1905.] 



Plate V 




*3B,^ 



Photo. A. Ernst. 

Fig. 5. Casuarina equisetifolia in the Strand-forest of Krakatau. 

In front of the oldest Casuarinas, festooned with Vitis trifolia and other climbing plants, 
is a belt of younger plants of Casuarina (p. 29). 




Photo. A. Ernst. 

Fig. 6. The New Strand-forest on the south-east coast of Krakatau. 

To the right occur Hibiscus tiliaceus, Pandanus. sp., Cycas circinalis; to the left 
a closed formation of Casuarina equisetifolia ; in the foreground a tree washed 

up by the sea (p. 28). 



Flora of Krakatau 29 

numerous clearings, is chiefly composed of such trees and shrubs as 
the botanist recognises in his first excursion into a. Javan strand-forest 
and as we had met with on Edam, at Vlakke Hoek and .Java's First 
Point. Tall Casuarinas, 12 15 metres [39 49 feet] high, form the 
largest portion of the closed forest-formation (PL V., fig. 5). Young in- 
dividuals of the same trees linked to the neighbouring shrubs by slender 
climbing plants, such as Gassytha, Vigna, Ccmavalia, Caescdpinia 
Bonducdla, Vitis trifolia, constitute an almost continuous mass of 
foliage ; the shoots of Vitis trifolia are especially abundant, winding- 
over the tallest Casuarinas and covering their stems and branches 
with a luxuriant mosaic of leaves. 

At the edge of the group of Casuarinas we discovered a fine specimen 
of a female plant of Cycas circincUis, bearing a handsome crown of 
fronds at the apex of a trunk 1 metre 65 cm. [5 feet 9 inches] high 
and 80 cm. in circumference ; the growing-point was surrounded by 
yellowish-brown carpellary leaves the ovules of which showed signs of 
shrinkage. Like those of previous years which lay on the ground, they 
were evidently destined to remain unfertilised. It is improbable that 
ripe Cycas seeds will be found in Krakatau in the near future, as in 
spite of diligent search Ave saw no male plants either on Krakatau or 
on Verlaten island, nor did we discover any other female plants 1 . 
Further to the south, slender stems of Calophyllum Inophyllvm and 
Terminalia Catappa with their whorled branches struggle upwards 
above the zone of trees and shrubs (Frontispiece). The leaves of both 
these trees are leathery, while in other species which we found here, 
such as Sopkora tomentosa, (Merodendron inerme, Pempln* addida, 
Morinda eitrifolia, they are fleshy, or like those of Tonmefortia 
argentea, especially on the younger branches of the plant, they are 
clothed with a dense felt of hairs. These plants like other trees 
and shrubs of the new forest-zone belonging to the Leguminosae, 
Euphorbiaceae, Rubiaccae, Lythraceae and other families, with the 
grasses, Lauraceae, Leguminosae and Compositae, which grow in the 
clearings, are all well adapted by their vegetative structure, particu- 
larly in the form and anatomical structure of their leaves, to an 
existence in ground rich in salt and which therefore, from a botanical 
point of view, despite the abundance of water, constitutes a physio- 
logically dry habitat. Above a clearing overgrown with tall grass we 
could see some specimens of the most beautiful tree of the tropical 
strand-forest, the Myrtaceous plant Barringtonia speciosa, after 
which the whole type of vegetation of these forests has been named 
the Barringtonia formation. The large white flowers present a 
striking appearance against the background of a dense canopy of 

1 See Addendum I., p. 72. 



30 Expedition of 1906 

gigantic lanceolate leaves. The lowest branches bear the mitre-like 
and light fruits in all stages of development in association with the 
flowers. 

Still further south coconut palms, the leaves of which we had 
seen through our glasses from the ship, tower above the groups of 
trees (PI. VIII., fig. 11). It was with some difficulty that we made 
our way to them over large blocks of pumice, through a tangle 
of reeds and grasses and thick bush. Half-way we came to a 
group of large-leaved fig-trees, Ficus fnlva and Ficus fistulosa, in 
full fruit, and, like many other tropical trees, bearing flower and 
fruit on the stem and older branches instead of on the younger 
shoots. The slender stems of Trichomnthes tricnspidata, a Cucur- 
bitaceous climbing plant, sprawl over the twigs and branches of the 
fig-trees, its light-red fruits standing out against the dark green 
foliage. The fig-trees, now represented by six species in Krakatau 
and Verlaten island, and Trichosanthes belong to those colonists the 
seeds of which are said to have been brought to the island by fruit- 
eating birds (endozoic). 

To our great delight we found the coconut palms laden with 
fruit. The large number of ripe nuts on the ground, several of which 
had germinated and produced plants reaching one metre in height, 
showed that they must have attained the fruiting stage some years ago : 
a renewal of the forest is thus amply provided for. We were all 
refreshed by a quantity of unripe fruits which one of our Javanese 
companions brought down from the crowns of the palm-trees. 

The region north-east of the Casuarina forest seemed to us to 
afford the most appropriate route by which to penetrate into the 
interior of the island and to the slopes of the cone. The strand- 
forest is here reduced to a very narrow zone and the girdle of creeping 
vegetation is at several points interrupted by the extension of the 
bush to the tide-level. Among taller plants which overlap the others 
are some coconut palms and handsome Pandanus clumps, reaching 
a height of 6 8 metres (PL VI., fig. 8 and fig. 9, PI. VII.), with their 
slender stems bent like snakes and anchored to the wave-swept beach 
by thick columnar roots ; the yellow and red masses of fruit as large 
as a man's head make a brilliant show in the dense crowns of narrow 
sharp-edged leaves. Close by we found a young coconut palm not 
yet at the fruiting age, a plant of the dwarf variety, termed by the 
natives " Kalapa gading," the fruits of which when fully ripe are of 
a beautiful orange-yellow colour. 

Following inland one of the broad stream-beds which the rapidly 
flowing water after the heavy rains had carved out of the soft strata, 
we soon found ourselves in the midst of a vegetation entirely different 
from that of the strand-flora. At the edge of the bed of the stream 



Plate VI 




Photo. A. Ernst. 

Fig. 7. Young coconut palm at the upper edge of the tide-level 

(south-east coast of Krakatau). 

To the left Ipomaea Pes-caprae ; to the right a shrub with Gassytha filiformis (p. 28). 




Photo. A. Ernst. 
Fig. 8. Pandanus on the beach (east coast of Krakatau). 
To the right Saccharum spontaneum ; iu the background, to the left, Casuariua forest (p. 30). 



Flora of Krakatau 31 

we found clumps of small mosses (Phikmotiis secunda [Dz. and Mb.] v. 
d. B. and Lac. and Bryvm coronatum Schwaegr.) and delicate ferns, 
especially Gymnogramme calomelanos with its young fronds covered 
with white calcareous scales. Blocks of pumice and lava lying in 
hollows below undermined banks were covered with a mantle of 
blue-green algae. By the sides of the stream, on undulating ground 
sloping upwards towards the mountain, some of the shore species of 
grasses and Cyperaceae predominated, and of the plants associated 
with them Sacehcvrum spontaneum, Gymnothrix elegans, and Phrag- 
mites Roxburgh it are remarkable for their unusual size. Their stems, 
3 4 metres high, form at first scattered bushes, in other places in 
company with Vigna, Ccmavalia and Cassytha, which occur here as 
climbing plants, they form regular thickets associated with shrubs of 
Tournefortia, Scacvola, and various ferns. 

A sudden rustling in the reeds in front of us was caused by a yellow- 
brown lizard (probably the strong swimming species, Va/ranm salvator 
Laur.), nearly 1 metre long, which had been lazily basking in the sun 
and made off in great haste. The fact that Selenka 1 and Sluiter 
found two specimens of Oalotes jubatus in 1894 renders it probable 
that other lizards, in addition to Varanus, occur on the island. 
Birds have also already established themselves on Krakatau. We 
occasionally saw gulls above the strand-forest, and in the interior of 
the island small birds flew noiselessly from the bushes to seek a 
quieter resting-place a short distance away. Beyond the strand- 
forest the whole gently sloping surface of the south-east side of the 
island was covered with the steppe-like vegetation which we have 
described and this extended in a dense mass into the wild ravines 
and on to the steep sides far up on the cone. The uniformity of the 
jungle of fresh and decaying stems of grasses and reeds is only 
occasionally broken by the occurrence of a fallen tree or shrub. 

Stretching in front of us half-way up the slopes of Rakata was 
a deep ravine the dark vegetation of which, rich in trees and shrubs, 
we had noticed as the ship approached the island. We attempted to 
penetrate the thicket and succeeded in reaching the first steep 
ridges which, with the intervening deep furrows and ravines, radiate 
in all directions on the slopes over the foot of the mountain (PI. VIII., 
fig. 12) a . We clambered up to the ridge through a tangle of grasses 
waving above us, then down the ravines ; it was tiring work, the 

1 Selenka, E. and L. Sonnige Welten. Oslasiatische Reiseskizzoi. Edit. n. 
Wiesbaden, 1905, p. 138; also a communication by letter from Prof. Sluiter of 
Amsterdam. 

['- This photograph (PI. VIII., fig. 12) was originally reproduced in Penzig's paper in 
the Annates du Jardin botanique de Buitenzorg, 1902, p. 104.] 



32 Expedition of 1906 

flora was monotonous and at first we found but few interesting 
plants. Ferns and grasses occurred everywhere ; rarely were our 
eyes gladdened by the stately inflorescence of some tall orchids of 
grass-like habit growing in the ground, Arundina speciosa, 
Spathoglottis plicata, Phajm or CyrnMdiwm and yellow-flowering 
Composites. We were, however, sorely tried by the representatives 
of the new fauna of Krakatau. In the lower Casuarina forest 
swarms of gnats flew about us and in collecting Pandanus fruits 
we disturbed small and dangerous wasps. Here on the higher 
slopes we found ourselves in the domain of a host of red and black, 
large and small ants. Their nests were partly hidden in a layer, 
1 metre thick, of decaying roots, broken and withered reeds and 
grasses, some of them hanging like nests on the shrubs and grass 
bushes. These small pests fall from their nests in showers on the 
intruders. 

We were still separated from our goal by many ridges always 
increasing in steepness and by deep ravines. Scorched by the 
burning rays of a vertical sun, we took turns, at the head of our small 
party, in handling the knife and cut our way step by step now up 
now down through the shadeless thicket. Our servants and carriers 
were barely able to keep up with us with the necessary luggage and 
the plant cases. At last Ave were reluctantly compelled to admit 
that with our primitive equipment and in the short time at our 
disposal it was impossible to reach the main gorge and the peak. 
In addition to the difficulties of the ascent due to the nature of 
the ground, we were confronted by a further difficulty presented 
by the thick growth of vegetation which afforded neither rest nor 
shade, so that our efforts, like those of the members of the earlier 
expeditions of 1886 and 1897, were not crowned with success. It 
may perhaps be possible for members of a fourth expedition pro- 
vided with a complete mountaineering and tropical outfit and with 
several days at their disposal to complete the investigation of the 
Krakatau flora ; but meanwhile the ascent of the cone and the 
examination of its unexplored plant-world are still to be accomp- 
lished. 

We retraced our steps ; by midday we had reached the ship 
which steamed at a short distance from the land along the east and 
north coasts of the island. The appearance of the coast rapidly 
changed. The level shore passes into a steep beach terminated 
above by the fissured spurs of the mountain like those which Ave had 
just attempted to scale. The north side with its almost vertical face, 
800 metres high, Avas an imposing sight. It showed the peculiar 
course of the variously coloured strata and veins, and afforded in an 



Plate VIII 




A. Ernst. 



Fig. 11. Clearing in the Strand-forest. 

To the left in the foreground Scaevola Koenigii; behind the grasses (Saccharum spontaneum) 

a group of coconut palms. South-east coast of Krakatau (p. 30). 




Photo. A. Clautrlau. 



Fig. 12. Grass-steppe in the interior of Krakatau. 
In the middle distance the first ravines and ridges on the slopes of Rakata (p. 31). 



Verbeek on Krakatau 33 

unique fashion a natural section of a volcanic cone (PI. III., fig. 2). 
Verbeek, in his monograph on Krakatau (loc, tit. II. pp. 107, 496), 
gives the following account of this precipice as he saw it in October 

1883 : "La paroi presque verticale de 832 metres de hauteur, avec la 
mer bleu fonce et profonde de 300 metres qui baigne son pied, fait 
sur tout le moncle, par son caractbre estrangement grandiose, une 
irresistible impression. Dans l'effondrement de 1883 la montagne 
fut coupee presque verticalement par le milieu, de sorte que la 
structure interne de ce volcan basaltique a et^ admirablement mise 
a decouvert. Quand on se trouve au nord de la paroi a pic, on voit 
a gauche apparaitre au pied de la montagne, sous les couches 
basaltiques et en discordance avec elles, les bancs massifs de la roche 
ancienne a tridymite et les couches de lapilli qui les recouvrent. 
Ces couches appartiennent au bord du cratere le plus ancien, et sont 
formees de la meme roche que Verlaten Eiland et Lang Eiland ; en 
cela elles different beaucoup des autres couches du pic, qui consistent 
surtout en matieres incoherentes, lapilli et fine cendre. Ces dernieres 
couches alternent avec quelques bancs de lave et sont coupees trans- 
versalement par des filons lithoides. Elles sont de couleur brunatre 
et tranchent fortement sur les matieres ponceuses r^centes, blanches 
ou gris clair, qui les recouvrent." Verbeek noticed a change in the 
appearance of the fractured surface in August and September 1884 : 
" La cendre gris clair mouille'e, qui a 1'origine avait degoutte vers le 
bas et recou vert la surface en divers points, surtout au milieu, etait 
maintenant en grande partie detachee par l'incessant eft'ritement de 
la roche. La trainee de cendre grise etendue sur le sommet avait 
entierement disparu, en laissant a decouvert une grosse veine 
pierreuse, qu'on peut suivre dans une direction presque verticale 
a travers les couches du pic, jusqu'a la moitie' de la hauteur totale de 
la montagne, ou elle se termine en un renflement lenticulaire." He 
adds to this description : " II est vivement a desirer que Ton reussisse 
bientot a obtenir de cette paroi une bonne representation photo- 
graphique, sur laquelle les diffeVentes couches et les differents filons 
soient nettement visibles. La tentative faite au niois de Septembre 

1884 a echoue' par l'insuffisance de la lumiere. Comine il n'existe au 
nord de la falaise aucune terre assez rapprochee, on est recluit a 
prendre la vue photographique a bord d'un navire ; l'exposition ne 
peut done avoir qu'une tres courte duree et dans ces conditions un 
e"clairement intense de l'objet est absolument necessaire." So far as 
I know none of the few visitors to Krakatau since this was written 
have had an opportunity of carrying out Verbeek's wish. I have 
therefore added to the photographs of the vegetation and plants 
which illustrate this account of the present state of the Krakatau 

s. 3 



34 Expedition of 1906 

flora the reproduction of one of the two views which the exception- 
ally favourable light and the stillness of the ship enabled me to obtain 
(PI. III., fig. 2) 1 . 

The face of the rock, like all the other parts of the island which are 
not covered with a thick carpet of vegetation, is continually under- 
going change of form. 

As we were on deck, taking our simple midday meal during the 
attractive voyage along the wild north coast, we suddenly became 
aware of an extraordinary phenomenon. Several small columns of 
smoke or steam appeared over a crater-like depression somewhat to 
the left of the highest peak, a spot rendered conspicuous by the 
absence of all trace of vegetation, and gathered into a light cloud 
over the mountain. Similar clouds rose above other points on the 
upper slopes. We asked ourselves : Is the volcanic activity of the 
island breaking out afresh ? During the last few months and weeks 
news had reached us of volcanic outbursts (Vesuvius, Hawaii), of 
terrible earthquakes (San Francisco), and in Java itself the crater of 
Merapi had become active ; in the highlands of Padang (Sumatra) 
the cone of Tandihat had broken out again after a long period of 
quiescence. Should we now have to take back to Batavia news of 
the reawakening of Krakatau ? Fortunately our anxiety proved to 
be groundless. With the help of our field-glasses and the captain's 
telescope we Avere able to discover the cause of this disturbing 
phenomenon : stones of all sizes and masses of sand were continually 
being dislodged and the air-currents which they produced in their 
headlong descent raised clouds of dust which hung over the peak 
like masses of smoke. As we came nearer we could see some large 
stones bounding in gigantic leaps over the rocks and forming screes of 
detritus at the foot of the rock precipice. Some of these screes are 
shown in the photograph (PI. III., fig. 2). 

We landed in a broad bay, which is enclosed by the western part 
of the precipice and a steep promontory, "Zwarte Hoek," which 
was formerly the most westerly point of the old island. At this point 
the waves have washed up on to the shore a considerable quantity of 
pumice and ash, forming a small beach, the colonisation of which by 
plants has not yet proceeded so far as on the east and south-east 
shores of the island. The surface of sand sprinkled over with blocks 
of pumice and large masses of black lava is partially covered with a 
network of Ipomaea, Canavalia and Vigna, the shoots of which in the 
absence of competing rivals reach a length of 20 metres [65 ft.] (PI. IV., 
fig. 4). Young coconut palms occur here and there with seedlings of 
Barringtonia spwiosa anchored in the sand by roots of 3 to 5 decimetres 

1 See Addendum II., p. 72. 



Zivarte Hoek 35 

long, while the tips of their stems are still enclosed in the fruit. Slender 
stems of Saccharum spontaneum with other grasses and Cyperaceae 
grow on the small cones of detritus at the foot of the rock-face in the 
loose stones of the lowest layers between the blocks of lava which 
cover the spurs of "Zwarte Hoek"; with these are associated 
plants of Casuarina, bushes of Scaevola Koenif/ii, with long panicles 
of white flowers hanging gracefully from the ends of branches above 
the rosettes of light green leaves, Sophora tomcntosa, with bunches 
of legumes constricted like strings of beads, De&modium iimbeUatum 
and other strand-species of Leguminosae. Plants of Splnifex 
squarrosus occur, and Nephrolejns cxaltata, a Polypodiaceous fern 
with simply pinnate leaves, monopolises large areas. Graceful 
specimens of Lycopodium cernuum grow in the shelter of the rocks, 
and Cassytha filiformis lives parasitically on a variety of hosts both 
at the foot of the rock-face and on the level ground. On the rocks 
we also collected delicate seedlings and numerous prothalli of Gi/mno- 
gra/mme and, in addition to other ferns and Lycopods, Polypodium 
querclfolium, one of the few epiphytes in the Barringtonia forests, 
which grows here in clefts in the rocks, as in the neighbourhood of 
solfataras and craters of the volcanoes of Java. Other ferns among 
those which we found on the lava and pumice boulders grow epi- 
phytically on the forest trees of Java and Sumatra. The conditions 
are approximately the same as in an epiphytic existence : a hard 
and comparatively dry substratum and intense sunlight have led the 
plants to return to a ground-habitat, and this is rendered easier by 
the fact that the struggle for a footing on the soil is not very severe. 

The sun remained vertically above us in a cloudless sky. Its burning 
and blinding rays on the white ground at the foot of the dark wall of 
rock produced an oppressive heat and a dazzling glare. Our servants 
were unable to follow us with bare feet over the hot sand and 
stayed behind on the edge of the shore which was cooled by the waves. 
We too were soon compelled to stop climbing over the loose blocks 
on the steep slopes of the Zwarte Hoek (black tongue of land) pro- 
montory, as it was impossible to bear our hands on the hot stones 
as we scrambled up the steep slopes. Before returning to the ship 
we rested in the partial shade afforded by a fallen boulder. The 
bay in front of us with the small trim steamer and the vertical rock- 
face glistening with coloured bands in the sunlight formed an im- 
pressive scene which made us forget our trouble and fatigue. 

A third landing on the west coast of Krakatau proved im- 
possible. We decided, therefore, to pay a short visit to one of the two 
neighbouring islands. Lang island which lay nearest to us, with its 
steep coast, is almost destitute of strand vegetation. Trees and 
shrubs are sparsely scattered on the broad grass-covered surfaces of 

32 



36 Expedition of 1906 

the island. We could see from the ship that the vegetation of 
Verlaten island had, on the other hand, reached a much more 
advanced stage of development. On the east coast, which faced us, 
we noticed not less than seven forest-like clumps of Casriarina 
equisetifolia, which with groups of other trees and shrubs formed an 
almost continuous belt parallel to the coast. As we steered a 
northerly course towards Verlaten island, approximately in the region 
of the sunken hill of Danan, our obliging captain stopped the ship 
in order to enable me to take a photograph of the island of Krakatau 
showing the whole of the north coast (PL III., fig. 1). Soundings 
taken as we neared Verlaten island showed that the figures on the 
charts no longer hold good, as considerable alterations have taken 
place in the contour of the sea-floor over the area of subsidence 
since the last observations were made. As the captain was anxious 
to get clear of the dangerous channel before nightfall he accompanied 
us to the shore in order to ensure our punctual return in the boat. 

The vegetation of Verlaten island, like that of Krakatau, consists 
of strand and inland floras. Here, as on Krakatau, fruits and 
seedlings of Nipa fruticans were found in the drift-zone associated 
with fruits and seeds of plants from the sandy and rocky beach, but 
there were no older individuals of this swamp-loving palm nor any other 
representatives of the Mangrove flora. The strand-flora of Verlaten 
island consists of members of the Pes-caprae and Barringtonia plant- 
formations. 

Between the single chimps of Casuarinas, in which many of the 
stems are thickly draped with climbing plants, Vitis trifolia and 
Mucuna pruriens, we noticed strand trees growing in company with 
Barringtonia, such as Terminalia and Calophyllum, Leguminosae 
and Pandanus litoralis. The leaves of Toumefortia argentea, to 
which a thick felt of hairs gives a silver-grey colour, were visible 
from a distance. Among widely distributed strand-plants occurred 
Erythrina indica, the Verbenaceous species Premna foetida, 
and two Rubiaceae, Morinda citrifolia, and Guettarda speciosa. 
Somewhat further inland we found several species of Ficus, coconut 
palms and another cultivated plant, Carica Papaya. Their seeds 
may have been brought to the island by birds or flying foxes which 
eagerly search for the soft fruits of the Papaw, or possibly this plant 
was introduced by man, as some years ago Verlaten island was 
inhabited for a time by a party of surveyors. On the other hand, 
Melastoma polyantJmm, a shrub with leathery leaves, large violet 
flowers and juicy berries which are eaten by several kinds of birds, 
is a widely spread species over the hills and valleys of Java, and has 
certainly been transported endozoically to this new locality by the 
agency of birds. 



Flora of Krakatau 37 

The tall grasses, Cyperaceae, ferns and Composites have spread 
through clearings in the strand-forest to the shore, reaching as far as 
the carpet-like mass of Ipomaea Pes-caprae, Spinifex, Ischaemum, 
Vigna, Canavalia and Cassytha. The interior of the island, as in 
Krakatau, is partially covered with an open and in part with a closed 
formation of grasses, Cyperaceae, and ferns interspersed with climbing 
plants, Composites and orchids and with scattered trees and shrubs. 
In 189/ fifteen species of phanerogams and vascular cryptogams were 
found on Verlaten island. Our collection, made by two of us during 
a visit of barely one hour, consisted of 42 species, seven of which 
(Vitex Negwirio, Carica Papaya, Colubrbia asiatica, Caesalpinia 
Bonducella, Mucuna pruriens, Ximenia americana, Ficus hirta) 
had not been previously found on Krakatau. It is highly probable 
that a longer visit to Verlaten island would have yielded a flora very 
similar in composition to that of Krakatau. The data we obtained 
are amply sufficient to demonstrate that the colonisation of Verlaten 
island has been accomplished in the same way and by means of the 
same agencies as in the case of the neighbouring island of Krakatau. 

Shortly after 5 o'clock we were again on board the steamer. 
Before sunset the whole group of islands was left behind us and the 
"Snip," making a wide sweep to the north, threading its way between 
Sebesi and Seboekoe, carried us into the island-studded Java Sea 
and next day to Tandjong Priok, the harbour of Batavia. 

III. The present composition of the flora of the 
island of Krakatau. 

The vegetation of Krakatau and Verlaten island has in the last 
ten years become considerably richer, in places even luxuriant. The 
results of our excursion enabled us to add considerably to the plant- 
list of the group of islands. The present flora of Krakatau includes 
representatives of all divisions of the plant-kingdom : Myxomycetes, 
Bacteria, Algae, Fungi, Liverworts, Mosses, Ferns, Gymnosperms, 
and Angiosperms. The total number of species collected in the 
group of islands during the excursions made in 1886, 1897 and 1900 
reached 137. 

In the following list the species obtained on the three occasions are 
arranged according to families and classes, beginning with the 
Angiosjjermae dicotyledoneae. The middle column shows on which 
of the three islands the plants were found and when (1880, 1897 or 
1900) the records were made. (Abbreviations: K. = Krakatau; 
V. = Verlaten island; L. = Lang island; 1= visit in June 1880; 
2 = visit in March 1897 ; 3 = visit in April 1900.) 



38 



Flora of Krakatau 



The information in regard to the area of distribution of the 
phanerogams and vascular cryptogams is taken from the Floras and 
systematic works mentioned below. 

A ngiospermae Dicotyledoneae. 
Fam. Compositae. 
1. Bluinea balsamifera D.C. K. 2. 3 ; V. 3 ; Coast vegetation of India and 



2. Blnmea hicraci folia D.C. 



3. Conyza angustifolia Ham. 

4. Conyza indica Miq. 

5. Emilia sonchifolia (L.) D.C. 



6. Erechthites hieracifolia (L.) K. 3 ; V. 3 
Raf. 



7. Pluchea indica (L.) Less. 

8. Senecio spec. 

9. Vernonia cinerea (L.) Less. 
10. Wedelia asperriina Boerl. 





L 


2. 


Further India and the islands 
of the Indian Ocean to the 
Philippines and Australia. 


K. 


2. 


3. 


India and Further India, Malay 
Archipel., Philippines, Aus- 
tralia, tropical and subtropical 
Africa. 


K. 


1. 


(?) 3. 


India, Malay Archipelago. 


K. 


]. 


3. 


Further India, Malay Archi- 
pelago, S. China. 


K. 


2. 




Widely spread in the tropics of 
the Old World and naturalised 
in the New World. 


K. 


3 


; V.3. 


All the warmer and temperate 
regions of America and intro- 
duced into the Old World. 


K. 


2. 


3; L. 2. 


Widely distributed from East 
India to Australia. 


K. 


1. 




Genus represented by several 
species in the Malay Archi- 
pelago. 


K. 


2. 


3. 


Abundant in the tropics of the 
Old World. 


K. 


2 


;L. 2. 


Java, Timor. 



1. Blume, C. L. Bijdragen tot de Flora van Nederlandsch Indie. Batavia, 1825. 

Enumeratio Plantarum Javae et Insularum adjacentium. Haag, 1830. 

Flora Javae, 1829. 

2. Boerlage, J. G. Handleiding tot de Flora van Nederlandsch Indie i. m. 

Leiden, 18901900. 

3. Christ, H. Die Farnkriiuter der Erde. Jena, 1897. 

4. Engler-Prantl. Natiirliche Pflauzenfamilien. i. Teil, 4. Abteilg. bis iv. Teil, 

5. Abteilg. 

5. Engler, A. Syllabus der Pflanzenfamilien. 4. Aufl. Berlin, 1904. 

6. Hooker, J. D. Flora of British India. Vol. I. vn. London, 1875 97. 
Hooker, W. J. Species filicum. Vol. i. v. London, 184664. 

7. Koorders, S. H. Notizen iiber die Phanerogamenflora von Java (rv.). Natuur- 

kundig Tijd8chrift voor Nederlandsch-Iudie. Bd. 60. 1901. 

8. Koorders, S. H., u. Th. Valeton. Bijdragen t. d. Kennis d. Boomsorten of 

Java. No. i x. 18731904. 

9. Miquel, F. A. W. Flora v. Nederlandsch Indie mit Suppl. : Prodromus florae 

Sumatranae. Amsterdam, 1855 60. 
10. Raciborski, M. Die Pteridophyten d. Flora v. Buitenzorg. Leiden, 1898. 



Flora of Krakatau 



39 



11. Wedelia glabrata B. et H. 

12. Wedelia scabriuscula Boerl. 

13. Wollastonia spec. 

Fam. Goodeniaceae. 

14. Scaevola Koenigii Vahl. 



K. l.(?)3. Java, Timor. 

K. 2 ; L. 2. Malay Archipelago, Java. 

K. 1. Several species in the Malay 

Archipelago. 

K. 1 . 2. 3 ; V. 2. Tropical East Asia, Malay Arclii- 



3 ; L. 2. 
Fam. Cucurbitaceae. 

15. Trichosanthes tricuspidata K. 3 ; V. 3. 
Lour. 



Fam. Biibiaceae. 

16. Guettarda spcciosa L. 

17. Morinda citri folia L. 



Fam. Labiatae. 
18. Hyptis brevipes Poit. 



pelago, Polynesia. 

From the Himalayas to Ceylon 
and Singapore, Malay Archi- 
pelago (Java and Sumatra), 
China, N. Australia. 



K. 3 ; V. 3. Almost all tropical coasts. 

K. 2. 3 ; V. 3 ; Tropical E. Asia, trop. Australia, 



L. 2. 



K. 3. 



Fam. Verbenaceae. 
19. Clerodendron inerme Gaertn. K. 3. 



20. Premna foetida Reinvv. 

21. Vitex Negundo L. 

Fam. Borraginaceae. 

22. Tournefortia argentea L 



K. 3 ; V. 3. 
V. 3. 



K. 1. 3; V. 3. 



Fam. Convolmdaceae. 
23. Calonyction asperum Choisy K. 3. 



Polynesia, in the interior (cul- 
tivated). 

Tropical America, introduced 
on the coast of Africa and 
tropical Asia. 

India and Further India, Cey- 
lon, Malay Archipelago, New 
Guinea, N. Australia. 

Java, Borneo, Moluccas. 

Nicobar Island, Ceylon, India, 
Malay Archipelago to the 
Philippines. 

Ceylon, Further India, Nicobar 
I., Malay Archipelago, New 
Guinea, trop. Australia. 



24. Ipomaea denticulata Choisy K. 3. 



Abundant in the Malay Archi- 
pelago. 

Ceylon, Further India, Malay 
Archipelago, Australia. 

25. Ipomaea Pes-caprae Sw. K. 1. 2. 3; V. 2. All tropical coasts. 

[-1. biloba] 3; L. 2. 

Fam. Asclepiadaceae. 

26. Cynanchum Blumei B. et H. K. 3. Sumatra, Java. 



Fam. Apocynaceae. 
27. Cerbera Odollam Gaertn. 



K. 1. 2. 3 ; V. 3 ; Tropical East Asia, Malay Archi- 
L. 2. pelago, Australia. 



11. Smith, J. J. Die Orchideen v. Java. Leiden, 1905. 

12. Schimper, A. F. W. Die Indomalayische Strandflora. Jena, 1891. 



40 



Flora of Krdkatau 



Fain. Melastomataceae. 

28. Melastoma polyanthum Bl. K. 3 ; V. 2. 3. Bast India, China, Malay Archi- 

pelago, Australia. 
Fam. Myrtaceae. 

29. Eugenia speciosa L. (?) L. 2. 

Fam. Combretaceae. 

30. Terminalia Catappa L. K.2. 3; V. 2. 3; Malay Archipelago, Keeling I., 

L. 2. Polynesia, New Guinea. 

Fam. Lecythidaceae. 

31. Barringtonia speciosa Forst. K. 2. 3 ; V. 3 ; Ceylon, Andaman I., Singapore, 



L. 2. 

32. Barringtonia Vriesei Teysm. L. 2. 
et Binnend. 



Fam. Caricaceae. 
33. Carica Papaya L. 



V. 3. 



Malay Archipelago, trop. Aus- 
tralia. 
Java (Prov. Bantam). 



Spread from America as a cul- 
tivated plant over the whole 
of the tropics. 



Fam. Guttiferae. 

34. Calophyllum Inophyllum L. K. 1. 3 ; V. 3 ; India, N. Australia, Polynesia. 

L. 2. 
Fam. Sterculiaceae. 

35. Melochia arborea Bl. K. 3 ; V. 3. 

36. Melochiaindica(Houtt.)A.Gr. K. 2. Malay Archipelago. 

Fam. Malvaceae. 

37. Hibiscus tiliaceus L. K. 2. 3 ; V. 3 ; All tropical coasts. 



Fam. Vitaceae. 
38. Vitis trifolia L. 



L. 2. 
K. 3. 



Fam. Rhamnaceae. 
39. Colubrinaasiatica(L.)Brongn. V. 3. 



Fam. Sapindaceae. 

40. Dodonaea viscosa L. 

Fam. Anacardiaceae. 

41. Spondias mangifera Willd. 

Fam. Euphorbiaceae. 

42. Euphorbia Atoto Forst. 

43. Euphorbia pilulifera L. 

Fam. Meliaceae. 

44. Carapa obovata Bl. 



K. 3. 



K. 3. 



K. 3 ; V. 3. 
K. 2; L. 2. 



K. 3. 



India and Further India, Cey- 
lon, Malay Peninsula, Java, 
Sumatra. 

India and Further India, Ceylon, 
Java, Borneo, trop. Australia. 

Tropical coast of S. Africa to 
Australia and New Zealand, 
also as an inland plant. 

Indo-Malayan region. 



Trop. and subtrop. E. Asia. 

Cosmopolitan in tropical and 
subtropical regions (also in- 
land). 

Ceylon, Malay Archipelago. 



Flora of Krakatau 



41 



45. 
46. 
47. 

48. 
49. 

50. 

51. 

52. 

53. 

54. 
55. 
56. 

57. 

58. 
59. 

60. 
61. 
62. 

63. 

64. 



Fam. Leguminosae. 
Albizzia stipulata Boiv. 



K. 2. 



Caesalpinia Bonducella (L.) V. 3. 

Roxb. 
Cassia siamea Lam. K. 3 



Trop. and subtrop. Asia, Malay 

Archipelago. 
All tropical coasts. 



Canavalia obtusifolia D.C. 
Derris uliinnosa Lour. 



Further India, Malay Archi- 
pelago. 
K. 2. 3 ; V. 2. 3 ; All tropical coasts. 

L. 2. 
K. 3. Trop. E. Asia to Hongkong and 

Polynesia. 
Desmodiuni umbellatura D.C. K. 3;V. 3;L. 2. Trop. E. Asia, Australia. 
Entada Pursaetha D.C. V. 2. Widely spread in the tropics of 

both hemispheres. 
Erythrina indica Lam. K. 1. (!) 3 ; V. 3 ; Indian region (also inland). 

L. 2. 
Erythrina ovalifolia Roxb. V. 3 ; L. 2. 

Indigofera Teysmanni Miq. K. 3. Sumatra. 

Mucuna pruriens D.C. V. 3. Tropics of both hemispheres. 

Pongamia glabra Vent. K. 3 ; V. 3. Indian region. 

Pithecolobium moniliferum K. 3. 
Bth. 

Sophora tomentosa L. K.3;V. 3;L. 2. All tropical coasts. 

Vigna lutea (Sw.) A. Gray K. 2. 3 ; V. 3 ; Andaman Islands, Malay Archi- 

L. 2. 
Vigna luteola (Jacq.) Benth. K. 2 ; L. 2. 



pelago, trop. Australia. 
Cosmopolitan in the tropics of 
the Cape and the Argentine. 



Fam. Hernandiaceae. 

Hernandia peltata Meissn. K. 1. 3. 

Fam. Lauraceae. 
Casytha filiformis L. 

Fam. Olacaceae. 

Ximenia americana L. V. 3. 

Fam. Urticaceae. 

Pipturus incanus AVedd. K. 3 ; V. 3. 





Fam. Moraceae. 




65. 


Ficus fistulosa Reinw. 


K. 3. 


66. 


Ficus fulva Reinw. 


K. 3 ; V. 3. 


67. 


Ficus hirta Vahl. 


V. 3. 


68. 


Ficus hispida L. 


L. 2. 


69. 


Ficus leucantatoma Poir. 


V. 3 ; L. 2. 


70. 


Ficus toxicaria L. 


K. 2 ; L. 2. 



Tropical E. Asia, New Guinea, 
Polynesia. 



K. 2. 3 ; V. 2. All tropical coasts (also inland). 
3 ; L. 2. 



Tropical coasts of the Old and 
New World. 

Malay Archipelago, Polynesia 
(also inland). 

Perak, Penang, Singapore, 
Malay Archipelago (Java). 

Java, Sumatra. 

Malay Archipelago, China. 

India, Further India, Ceylon, 
Malay Archipelago, China, 
Australia. 

Malay Archipelago, Java and 
Sumatra. 



42 



Flora of Krakatau 



Fam. Ulmaceas. 

71. Trema amboinensis Bl. K. 3. Subtrop. and trop. Asia and 

Australia. 
Fam. Casuarinaceae. 

72. Casimrina equisetifolia Forst. K. 2. 3; V. 2. 3; Further India, Malay Archi- 

ll. 2. pelago (also inland), N. Aus- 

tralia. 

A ngiospermae Monocotyledoneae. 
Fam. Orchidaceae. 

73. Arundina speciosa Bl. K. 2. 3. 



74. Cymbidium Finlaysonianum K. 3 
Lindl. 



K. 2 ; L. 2. 



Very common in Java in sunny 
places (volcanoes!), Borneo, 
Sumatra, Malacca, East India. 
Malay Archipel. (Java, Borneo, 
Sumatra, Celebes, Riouw, 
Singapore, Malay Peninsula). 
About 20 species in the Malay 
Archipelago. 
K. 2. 3 ; V. 3 ; Penang, Perak, Singapore, 
L. 2. Malay Archipelago (Java), 

Manilla, New Guinea. 
L. 2. Java. 

K. 3 ; V. 3 ; L. 2. All tropical coasts. 



75. Phajus spec. 

76. Spathoglottis plicata Bl. 

77. Vanda Sulingi Bl. 
Fam. Palmae. 

78. Cocos nucifera L. 

Fam. Gyperaceae. 

79. Cyperus digitatus Roxb. K. 1. (?)2; V.2. Widely spread in the tropics, 

India, Ceylon, Penang. 

80. Fimbristylis spathacea Roth K. 1. (?) 2. 3. Ceylon, Further India, India, 

V. 3; L. 2. Singapore. 
K. 3. From Africa to New Guinea, 

Java, Sumatra. 
K. 3 ; L. 2. All tropical coasts. 



81. Mariscus umbellatus Vahl. 



82. Remirea maritima Aubl. 

Fam. Gramineae. 

83. Gymnothrix elegans Biise 



84. Imperata arundinacea Cyr. 

85. Ischaemum muticum L. 
S6. Pennisetum elegans J.K. 



K. 1. 2 ; V. 2 ; Java. 
L. 2. 

K. 2. 3 ; L. 2. Cosmopolitan, Alang-Alang [Im- 
perata arundinacea] fields in 
the Malay Archipelago. 
K. 2. 3 ; V. 3 ; Malay Archipelago, Burmah. 

L. 2. 
K. 3 ; V. 3. Trop. America, Africa, India. 

87. Phragmites Roxburghii Stend. K. 1. 2; V. 2; Trop. Africa, India, Ceylon, 

L. 2. Sumatra, Java, Australia. 

88. Pogonatherum crinitum Trin. K. 2. 3 ; V. 3 ; India and Further India, Malay 

L. 2. Archipelago. 

89. Saccharum spontaneum L. K. 2. 3; V. 3; Tropics of the Old World; occurs 

L. 2. in the Alang-Alang [Imperata 

arundinacea] fields of the 
Malay Archipelago. 



Flora of Krakatau 43 

90. Spinifex squarrosus L. K.2. 3;V. 2. 3; India and Further India, Malay 

L. 2. Archipelago. 

Fam. Pandanaceae. 

91. Pandanus spec, (littoralis K.2. 3; V. 2. 3. Several species in the Indo- 

Jungh. ?). Malayan strand-formation, 

particularly common in Java 
and on the coral islands of 
the Java Sea. 

Gymnospermae. 
Fam. Cycadaceae. 

92. Cycas circinalis L. K. 3. India and Further India, Malay 

Archipelago (also inland). 

Pteridophyta. 
Fam. Lycopodiaceae. 

93. Lycopodium cernuum L. K. 2. 3. Islands and coast of the tropical 

zone ; especially in the Malay 

Archipelago. 
Fam. Ophioglossaceae. 

94. Ophioglossum moluccanum K. 2. Hills and lower forest-zone of 

Schlecht Java. 

Fam. Polypodiaceae. 

95. Acrostichum aureum L. K.J. 2. 3; V. 2. Mangrove swamps and Nipa- 

formation of all tropical 
countries. 

96. Acrostichum scandens J. Sm. K. 1. 2. Mangrove- and Barringtonia- 

formation. From N. India 
and S. China to N. Australia. 

97. Aspidium vile Kze. K. 2. Xerophilous ; volcanoes of Java. 

98. Blechnum orientale L. K. 1. 2; V. 2. From N. India and S. China to 

Polynesia, New Guinea, and 
Australia. 

99. Gynmogramme calomelanos K. 1.2. 3; V. 3. Tropics of the New and Old 

(L.) Kaulf. World. 

100. Nephrodium calcaratum (Bl.) K. 1. From E. Himalayas extending 

Hook. to the south of S. China ; 

Malayan region. 

101. Nephrodium cucullatum(Bl.) K. 1.2. 3. Malay Archipelago; plains and 

Bak. high ground. 

102. Nephrodium flaccidum Hook. K. 1. Malay Archipelago (Java). 

103. Nephrolepis exaltata Schott K. 1.2. 3;V. 3. Epiphytic and ground-fern, from 

N. India and Japan to Aus- 
tralia and New Zealand; Africa 
and America. 

104. Onychium auratum Kaulf. K. 1. Himalayas to the Philippines. 

105. Polypodium quercifolium L. K. 2. 3. N. India and S. China to Ceylon, 

Malay Archipelago. 

106. Pteris aquiliiia L. K. 1. 2. Cosmopolitan. 



44 



Flora of Krakatau 



107. Pteris longifolia L. 

108. Pteris marginata Bory 



K. 1.2. 3; V. 3. Warmer countries of the Old 

World ; very widely spread 

in Java. 
K. 1. From E. India and Ceylon 

through the Malay region to 

N. Australia. 



Bryophyta. 
K. 2. 



Fam. Anthocerotaceae. 

109. Anthooeros spec. 

Fam. Bartramiaceae. 

110. Philonotis secunda (Dz. et K. 1. (?) 3. 

Mb.) v. d. B. et Lac. 

Fam. Bryaceae. 

111. Bryum coronatum Schwaegr. K. 1. (?) 3. 



Fam. Agaricineae. 

112. Hygrophorus spec. 

Fam. Polyporaceae. 

113. Polystictns sanguineus (L.) 

Fries. 

114. Polystictus hydnoides 



Eumycetes. 
K. 2. 

K. 3. 
K. 3. 





Fam. Bacillariaceae. 


Zygojyhyta. 


115. 


Navicula spec. 


K. 2. 


116. 


Encyonema ventricosum 
Kiitz. 


K. 2. 


117. 
118. 


Nitzschia sigma (Kiitz.) Sm. 
Cystopleura gibba (Ehrenb.) 
Kunze 


K. 2. 
K. 2. 


119. 


Cystopleura gibberula 
(Ehrenb.) Kunze var. 
producta Grun. 


K. 2. 




Fam. Chroococcaceae. 


Schizophyta, 


120. 
121. 


Aphanothece Castagnei 

(Breb.) Rabh. 
Gloeothece rupestris (Lyngb.) 

Bor. 


K. 2. 
K. 2. 



Fam. Oscillatoriaceae. 

122. Lyngbya Verbeekiana Treub K. 1. 

123. Lyngbya minutissima Tr. K. 1. 

124. Lyngbya intermedia Tr. K. 1. 

125. MicrocoleuschlonoplastesThr. K. 2. 

126. Oscillatoria amphibia Ag. K. 2. 

127. Schizothrix vaginata Gom. K. 2. 

128. Symploca spec. K. 1. 



Flora of Krakatcm 



45 



Fain. Nostocaceae. 

129. Anabaena spec. K. ]. 

Fam. Scytonemaceae. 

130. Scytonema mirabile Boss. K. 2. 

131. Tolypothrix spec. K. 1. 

Fam. Bacteriaceae. 

132. Bacterium radicicola Beye- K. 3. 

rinck 

133. Bacterium Krakataui De K. 3. 

Kruyff 

134. Bacillus Mycoides Fliigge K. 3. 

135. Bacillus Moire (B. mega- K. 3. 

therium de Bary ?) 

136. Bacillus fluorescens liquae- K. 3. 

faciens 

Myocothallopkyta. 
Fam. Physaraceae. 

137. Physarumcinereum(Batsch) K. 2. 

Pers. 

The majority of the species which have found their way to the 
island during the last ten years belong to the phanerogamous plants, 
which now give the characteristic facies not only to the strand 
vegetation but to that on the plains and mountain slopes. While 
the ferns have not materially increased in number, the total number 
of phanerogams (15 species in 1886) has risen from 56 x in the 
year 1897 to 92 in April 1906. The additional species are almost 
equally distributed between the strand and inland flora. 

The following species belong exclusively or mainly to the strand- 
zone of Krakatau and Verlaten island : 



*Blumea balsamifera D.C. 
Conyza angustifolia Ham. 
Pluchea indica (L.) Less. 
*Wedelia glabrata B. et H. 
Wollastonia spec. 
*fGuettarda speciosa L. 
fHyptis brevipes Poit. 
*|Premna foetida Reinw. 
*fTournefortia argentea L. 
flpomaea denticulata Choisy 
Cynanchum Blumei B. et H. 
Eugenia speciosa L. 



Blumea hieracifolia D.C. 
f Conyza indica Miq. 
Wedelia asperrima Boerl. 
Wedelia scabriuscula Boerl. 
*fScaevola Koenigii Vahl. 
*fMorinda citrifolia L. 
*f Clerodendron inerme Gaertn. 
*Vitex Negundo L. 
* Calonyction asperum Choisy 
*fIpomaea Pes-caprae Sw. 
*fCerbera Odollam Gaertn. 
* f Terminalia Catappa L. 



1 Penzig gives 53 as the number ; he did not include in the list of the plants 
obtained in 1897 the two species of Conyza and Senccio sp. found by Treub. 



46 



Flora of Krdkatau 



*fBarringtonia speciosa Forst. 

*tCalophyllum Inophyllum L. 
Melochia indica (Houtt.) A. Gr. 
Vitis trifolia L. 

* f Dodonaea viscosa L. 
*f Euphorbia Atoto Forst. 

fCarapa obovata Bl. 

Cassia siamea Lam. 
fDerris uliginosa Lour. 

Eutada Pursaetha D.C. 
fErythrina ovalifolia Roxb. 

Mucuna prurieus D.C. 

Pithecolobium moniliferum Bth. 
fVigna lutea (Sw.) A. Gray 
*fHernandia peltata Meissn. 
fXimenia americana L. 

* f Casuariua equisetifolia Forst. 

Cyperus digitatus Roxb. 
fRemirea maritima Aubl. 

* f Spiuifex squarrosus L. 
*fCycas circiualis L. 
*fPolypodium quercifolium L. 



Barringtouia Vriesei Teysm. et 

Binnend. 
Melochia arborea Bl. 
*t Hibiscus tiliaceus L. 
*fColubrina asiatica(L.) Brongn. 
fSpondias mangifera Willd. 
t Euphorbia pilulifera L. 

* f Caesalpinia Bouducella (L.) 

Roxb. 
*fCanavalia obtusifolia D.C. 
*f Desmodium umbellatum D.C. 

* fErythrina indica Lam. 

Indigofera Teysmanni Miq. 
*f Pongamia glabra Vent. 
*fSophora tomentosa L. 

fVigna luteola (Jacq.) Benth. 
*fCassytha filiformis L. 

Pipturus incanus Wedd. 
*fCocos nucifera L. 

* Fimbristylis spathacea Roth 
*flschaemum muticum L. 

*Pandanus spec. 

* f Acrostichum aureum L. 



Two-thirds of the strand-flora of the island of Krakatau are made 
up of species which are ubiquitous on tropical coasts. Of the 67 
species in the above list, 42 (indicated by f) are included as typical 
strand-plants in the lists given by Schimper 1 and Hemsley 2 : 35 of 
these are widely spread and abundant beyond the Malay Archipelago 
and may occur over the whole tropical zone. The importance of 
these plants in the strand-flora on the coast of the Sunda Strait 
region is illustrated by an examination of the lists of the species 
which we collected on Edam, at Vlakke Hoek (Sumatra) and Java's 
First Point (pp. 1214, 17, 18, 24, 25). 

Of the 36 halophytes from Edam, indicated by f , 18 occur on the 
Krakatau islands ; the islands possess 21 of these widely spread species 
in common with the strand-flora of Vlakke Hoek and 14 with that of 
Java's First Point. An equally well marked agreement is shown by 
a comparison with other localities on the coasts of Java and Sumatra, 

1 Schimper, A. F. W. Die Indomalayische Strandjlora, p. 100. 

2 Hemsley, B. W. Report of the Present State of Knoicledge of Various Insular 
Floras, p. 42. 



Flora of Krakatau 



47 



with the islands of the Java Sea or the Sunda Strait region. Of the 
17 strand-plants which Guppy 1 records from the localities which he 
visited on the south-west coast of Java, 14 belong to the Krakatau 
flora. The Keeling or Cocos islands (south-east of the Sunda Strait 
in lat. 12 S. and 98 E. long.), visited by Darwin 2 (1836), Forbes 3 
(1878), and Guppy (1888), possess 18 representatives of the Krakatau 
flora out of a total of about 30 phanerogams. The five localities 
together (Edam, Vlakke Hoek, Java's First Point, S. W. coast of Java 
and the Cocos islands) include 36 species (shown by *f or * in the list) 
which are represented in the strand-flora of Krakatau. The 25 
additional species, which occur in the new strand-flora of Krakatau, 
belong to genera other species of which are mentioned as typical 
strand-plants in the lists of Schimper and Hemsley. 

In the interior of the island, on the gently sloping beach and on 
the sides of the cone, the following phanerogams and vascular 
cryptogams occur with several species which are also included in the 
list of strand-plants. 



Emilia sonchifolia- (L.) D.C. 

Senecio spec. 

Trichosanthes tricuspidata Lour. 

Carica Papaya L. 

Ficus fistulosa Reinw. 

Ficus hirta Vahl. 

Ficus leucantatoma Poir. 

Trema amboinensis Bl. 

Cymbidium Finlaysonianum Lindl. 

Spathoglottis plicata Bl. 

Mariscus umbellatus Vald. 

Imperata arundinacea Cyr. 

Phragmites Roxburghii Stend. 

Saccharum spontaneum L. 

Lycopodium cernuum L. 

Acrostichum scandens J. Sin. 
Blechnum orientale L. 



Erechthites hieracifolia (L.) Raf. 
Vernonia cinerea (L.) Less. 
Melastoma polyanthuin Bl. 
Albizzia stipulata Boiv. 
Ficus fulva Reinw. 
Ficus hispida L. 
Ficus toxicaria L. 
Arundina speciosa Bl. 
Phajus spec. 
Vanda Sulingi Bl. 
Gymnothrix elegans Biise 
Pennisetum elegans I.K. 
Pogonatherum crinitum Trin. 

Ophioglossum moluccanum 

Schlecht 
Aspidium vile Kze. 
Gynmogramme calomelanos 

Kaulf. 



1 Guppy, H. B. The dispersal of Plants, as illustrated by the Flora of Keeling 
or Cocos Islands. (Reprint, 1890, p. 30.) 

2 The plants collected by Darwin were determined by J. S. Henslow : " Florula 
Keelingensis," Ann. Mag. Nat. Hist., 1838, Vol. i. pp. 337347. The list is given 
also in the Challenger Reports, Botany, Vol. i. Pt. iii. p. 113. 

3 Forbes, H. 0. A Naturalist's Wanderings in the Eastern Archipelago, 
187883. Loudon, 1885. 



48 Biological Conditions 

Nephrodiumcalcaratum(BL)Hook. Nephrodium cucullatum (Bl.) 

Bak. 
Nephrodium flaccidum Hook. Nephrolepis exaltata Schott 

Onychium auratum Kaulf. Pteris aquilina L. 

Pteris longifolia L. Pteris marginata Bory 

The plants in this list, as the notes appended to the list of the whole 
flora show, are also characterised by a wide distribution. Some are 
cosmopolitan and, as in the case of Lycopodiwm ccrnuum, Pteris 
aquilina, and others, are met with in all parts of the world. Others 
are spread over the tropics of the Old World (Emilia sonchifolia, 
Vernonia cinerea, Saccharum spontaneimi, etc.), occurring throughout 
the whole of subtropical and tropical Asia or in the Malay Archipelago 
region. Within their respective distribution-areas they belong to the 
commonest plants and to such as grow indifferently in a great variety of 
habitats. These constituents of the new Krakatau flora owe their 
occurrence in the new habitat, as also their wide distribution, chiefly 
to the efficient adaptation of their fruits and seeds to distant 
transport. 

IV. The biological conditions on Krakatau. 

The new flora of Krakatau demonstrates in a remarkable degree 
how quickly plants are able to take possession of a sterilised region 
even under the most unfavourable conditions. It is by the co- 
operation of a variety of factors that living germs, which have been 
carried by some agency or other to new land like Krakatau, are able 
to continue their existence and even to produce new plants. A large 
proportion of the germs which reach the new land do not survive 
because they fail to find ground suited to their development or 
because of unfavourable climatic conditions. Seeds and fruits of 
other plants, for which the conditions of the new habitat may be 
congenial, have lost the power of germination during transport 
either by desiccation or by excessive wetting, or they may retain the 
power to germinate for a short time only after falling from the tree 
and this has been lost in the course of their long voyage. Many of 
the seeds which are capable of germination and further development 
are destroyed by animals either before or during germination, or they 
may have been killed by changes in the substratum. In the early 
stages of the colonisation of fresh ground, the struggle with other 
plants for space and light may be disregarded. 

On the other hand, a plant which has begun to grow requires such 
conditions as are favourable to the fertilisation of its flowers and the 



Pioneers of Vegetation 49 

ripening of its fruits. Anemophilous plants which have obtained 
a footing on the ground will presumably produce a large crop of 
fruit and thus be in a better position, from the point of view of dispersal 
over the virgin soil, as compared with others with special contrivances 
for the pollination of their flowers by particular insects which are un- 
likely to exist on a newly formed and isolated land-area. For the 
same reason dioecious species often fare badly in regard to dispersal. 
If only a single individual of such a species occurs (as in the case of 
Ci/cas on Krakatau), or if a few are spread over a wide area, the 
production of fruit is clearly impossible. Plants of this class will 
therefore cease to form a part of the flora if new seeds, capable of 
germinating and producing individuals of the opposite sex, do not 
reach the island before the death of the first arrival. 

During the first few years of the colonisation of Krakatau the 
injurious influences of intense insolation and of running water must 
have acted as a serious check to the pioneers of vegetation on the 
fields of pumice and volcanic ash. There is comparatively little rain 
in the dry season of the year which, presumably at Krakatau, as at 
Batavia and other places on the north-west coast of Java, continues 
with the south-east monsoon approximately from May to September. 
Every day, also on clear days in the rainy season, the temperature of 
the ground considerably exceeds the maximum for the growth and ger- 
mination of the majority of plants. The total rainfall of the island 1 
probably amounts to 2| metres [98 inches] a year, the greater part 
falling between December and March. The denuding force of the 
streams after each heavy downpour of rain, more especially during the 
first few years after the volcanic outburst, produced surface-changes 
and many seeds must have been swept away with the loose superficial 
rock ; many seedlings which had developed despite unfavourable 
conditions must have been "torn up or buried in sediment. 

The chemical composition of the substratum and its physical 
properties were, on the other hand, not so unfavourable to plant- 
colonisation as one would expect. The analyses of the ash and 
pumice made by C. Winkler and given by Verbeek (loc. tit. u. 
p. 305) show that they contain a sufficient quantity of all the inorganic 
salts necessary for a plant (excluding nitrogenous and phosphorus- 
containing compounds) and, a fact of primary importance in plant-life, 
the salts occur, in part at least, in a soluble form. The following results 



1 In West Java the average from 24 stations is 276 cm., in East Sumatra the 
average of 10 stations is 264 cm. ; for the whole Archipelago the mean rainfall may 
be reckoned at 252 cm. 

s. 4 



50 



Biological Conditions 



are given for the ash from the uppermost layers formed during the 
first eruption (a) and for the light coloured pumice, etc. (b) : 







(a) 






(&) 


Si0 2 




60-13 v 




68-51 > 


Ti0 2 




1-10 




0-82 




A1 2 3 




17-41 




15-96 




Fe 2 3 




4-30 




2-61 




FeO 
MnO 
CaO 
MgO 




1-68 
0-40 
3-36 
2*27 


Insoluble in 
y water 
99-56 % 


1-09 
0-28 
3-14 
1-07 


, Insoluble in 
V water 
99-31 % 


K 2 




2-46 




1-82 




Na 2 




4-88 




4-01 




CaS0 4 


(Anhydrite) 


1-57 









Organic 


substance 


traces' 






NaCl 




0*75' 




1-09 ' 




KC1 




traces 


Soluble in 


traces 


Soluble in 


Na 2 S0 4 




0-22 


water 




k water 


CaS0 4 




o-ii 


1-11 % 


0-22 


1-34 % 


FeS0 4 




0-03- 




0-03 > 





The soluble substances are derived chiefly from sea- water which 
percolated through the surface to the reservoir of lava or was driven 
into the crater at the time of the explosion, and in the course of 
subsequent eruptions became mixed with the volcanic ash. Possibly 
some of the gypsum has not come from sea-water but from older 
strata of the volcano ; this hypothesis derives support from the fact 
that v the insoluble portion of the ash contains a considerable amount 
of anhydrite. Among the other components of sea- water magnesium 
chloride is not represented in the soluble constituents of the ash ; it 
is probable that by contact with aqueous vapour at a high tempera- 
ture this was converted into the insoluble oxide of magnesium. The 
small amount of bromine and iodine in sea-water (about / o ) may 
well explain the absence of these elements both from the ash and the 
pumice. 

Some of the inorganic salts required for the nutrition of plants 
were present in the material produced by the eruption in more than 
sufficient quantity and in a soluble and available form. Such sub- 
stances as are unrepresented in the volcanic material may have been 
brought in the form of dust in the same way as organic germs are 
carried to islands by water and by wind. Moreover, tidal waves and 



Colonisation of bare Ground 51 

waves produced during storms constantly wash up on to the beach 
large quantities of organic material, sea-weeds and marine animals, so 
that a plentifully supplied nidus would always be found at a distance of 
50 metres or more from the coast ; from this the underlying porous 
pumice and ashes would derive organic and inorganic products of 
decay. 

As regards the establishment of conditions favourable for plant- 
life in the interior of the island, other sources must be considered ; 
clouds of dust blown by local winds from the shore ; minute particles 
of inorganic and organic substances brought by the monsoon together 
with micro-organisms and the spores of mosses and ferns; also the 
seeds of phanerogamous plants ; and lastly, the nitric and nitrous acids, 
which constitute the chief supply of nitrogenous food, provided by rain. 
We are justified in assuming that in equatorial regions the oxidation 
of nitrogen to nitrates and nitrous acid takes place under the in- 
fluence of electrical discharges, which accompany the almost daily 
storms, at least with as much activity if not with much greater 
activity than with us. 

Despite the comparatively small amount 1 of nitrogenous material 
which is added to the ground by rain in a single year, it would 
however be sufficient, together with the salts and traces of organic 
matter contained in the ash, to support even in the first years after 
the eruption a rich flora of micro-organisms. 

Three years after the volcanic outburst dark green gelatinous 
layers of "blue-green" algae were found on the surface of the pumice 
and ash and on the loose stones in the ravines of the mountain 
slopes ; these were correctly regarded by Treub as affording a 
satisfactory nutritive medium for the germination of the spores of 
cryptogams and the seeds of phanerogams. The important part 
played by algae, particularly the Cyanophyceae, in the colonisation 
of bare ground and poor soil has since been demonstrated in many 
other localities, and recently Fritsch 2 has dealt fully with this subject 
also in the case of tropical regions, especially in Ceylon. 

The Bacteria and Mould-Fungi may perhaps have played even 
a more important part in the'preparation of a favourable substratum 
for the higher plants in the earliest phase of colonisation. Researches 
into the Bacterial flora were first undertaken during our (the third) 

1 In Europe according to Boussiugault there are 1 6 milligrammes of nitric acid 
in a litre of rain-water; Von Ad. Mayer calculates that in a year the rain brings down 
about 1 kilogramme to each hectare [2 - 47 acres]. 

2 Fritsch, F. E. " The role of Algal Growth in the Colonisation of new ground 
and in the determination of Scenery." The Geographical Journal, November 1907, 
pp. 531-548. 

42 



52 Biological Conditions 

expedition ; it is, however, certain that these minute organisms were 
introduced on to the island and began to develope as soon as, possibly 
even before, the algae and spores. 

Dr E. De Kruyff, Bacteriologist to the Agricultural Department of 
Buitenzorg, was kind enough to provide me with sterilised tubes and 
appliances for obtaining samples of earth, also a culture-plate for 
the enumeration of Mould-Fungi ; he generously undertook the 
examination of our material. The bacteriological investigations based 
on four samples of soil (two samples from the Barringtonia and 
Casuarina forests, one sample from the strand-zone, one sample from 
the interior of the island) demonstrated the occurrence of between 
1,300,000 and 2,800,000 (the average of four samples 2,200,000) 
bacteria in 1 gramme of soil, figures which agree with those ob- 
tained by De Kruyff from an examination of the soil at Buitenzorg 
in Java and with the results of similar calculations in regard to 
various soils in Switzerland. 

The number of the bacteria species identified is not large, but it 
is important to notice that they belong to very different biological 
groups. Among the ordinary soil-bacteria, Bacillus mycoides and 
Bacillus Moire' (B. Megatherium De Bary ?) were abundant, and 
Bacillus fluoresceins liquaefaciens among typical putrefactive 
bacteria. 

All four samples afforded examples of bacteria which destroy 
cellulose, pectin, and starch, as well as Urobacteria, the bacteria 
which decompose urea, a fact of some interest in view of the feeble 
development of animal-life on the island. Several Moulds were found 
on the culture-plate, but it is remarkable that no Yeasts occurred 
either on the plates or in the samples of earth. By far the most 
important fact from the point of view of the nutrition of vascular 
plants on Krakatau is the occurrence of such bacteria as play an 
important part in the circulation of nitrogen, the nitrite- and nitrate- 
bacteria and the nitrogen-fixing bacteria. 

As the result of the disintegration of the nitrogenous substances 
of dead animals and plants by putrefactive bacteria and other micro- 
organisms the nitrogenous compounds are largely converted into 
ammonia. A portion of the ammonia which is thus produced is fixed 
by the soil and afterwards converted by the action of nitrite- and 
nitrate-bacteria into nitrous and nitric acids which are readily taken 
up in the form of salts by the absorbing organs of vascular plants. 
Another portion of the ammonia is given off into the air as gas and 
some of it is given back to the soil by the rain in combination with 
nitric, nitrous and carbonic acids. 

In the interior of the island also a considerable quantity of 



Means of Dispersal 53 

nitrogen is added to the soil in the form of ammonia, and this can 
be directly used by several of the green plants ; for others it is made 
available as a source of nitrogen by the nitrifying action of nitrite- 
and nitrate-bacteria. 

Another means by which the soil of Krakatau, which originally 
contained no nitrogen, becomes richer in nitrogenous compounds is 
afforded by the action of nitrogen-fixing bacteria. The well-known 
free-living forms Clostridium Pasteurianum and Azotobacter chroo- 
coccwm, which possess the power of fixing atmospheric nitrogen, 
were not detected in the samples of soil, but by the employment of 
Beyerinck's method De Kruyft' 1 succeeded in isolating a new aerobic 
nitrogen-fixing bacterium, Bacterium Krdkataui, from soil taken 
from the small forests and from the Pes-caprae zone. 

In addition to this free-living nitrogen -fixing bacterium, Bac- 
terium radicicola has also been carried to the island by wind-agency ; 
this species, which lives symbiotically in the roots of Leguminosae, is 
capable of fixing a considerable amount of atmospheric nitrogen. On 
the roots of all the Leguminous plants examined, Vigua, CanavaUa, 
Erythrina, I found the characteristic root-tubercles in abundance. 
As the result of their symbiosis with Bacterium radicicola, which by 
the assimilation of atmospheric nitrogen considerably reduces the 
intensity of the struggle for food on the substratum of pumice and 
ash insufficiently provided with nitrogenous and phosphorus-con- 
taining compounds, the Leguminosae have played an exceptionally 
important role in the colonisation of the island. This family is now 
represented by 16 species, belonging to 14 genera, partially in the 
Pes-caprae and Barringtonia formations in the strand-zone ; in 
the inland flora also the Leguminosae are represented by Vigna, 
CanavaUa, Caesalpinia, and Mucuna, and in both regions they 
exceed almost all other arborescent and shrubby plants in the 
number of individuals. 

V. The relative importance of the different agents of plant- 
dispersal in the colonisation of the Krakatau islands. 

Under the head of means of dispersal of fruits, seeds, and such 
vegetative organs as are specially adapted for reproduction, the 
same agencies were concerned in the colonisation of the Krakatau 
group, as in the colonisation of new islands in general ; namely 
transport by birds, by wind, and by sea-currents. 

1 E. De Kruyff. " Sur une bacterie aerobe, fixant l'azote libre de l'atmosphere : 
Bacterium KraJcataui." Bulletin (lit Dip. de I'agriculture aux hides Neerlandaises, 
No. iv. (Micro-Biologie n.), Buitenzorg, 1906. 



54 Means of Dispersal 



1. Ocean-currents. 

The seeds and fruits of strand-plants, such as occur everywhere 
in the drift-zone of the coasts, are transported, almost without 
exception, by sea-currents. In the case of many of these their 
capacity for floating a considerable length of time in sea-water or 
in salt-solution without losing the power to germinate, has been 
demonstrated experimentally by Guppy 1 ,' Schimper, and others. 
Floating capacity is not possessed in an equal degree by all strand- 
plants. Some of them swim equally well whether freshly fallen 
from the tree or in a dry state, while others can be carried by water 
only after being dried. It is well known that such large drift-fruits 
as coconuts, the fruits of Cerbera Odollam, Nipa fruticans, Bar- 
ringtonia, Calophyllum, and Terminalia Catappa possess the power 
of floating for a considerable time. Similarly small fruits and seeds 
float for long periods. In Guppy's experiments the seeds of Gkiet- 
tarda speciosa, Scaevola Koenigii, Morinda citrifolia, Tournefortia 
argentea and others among the strand-plants which occur on 
Krakatau, germinated after floating on sea-water for 40 to 53 days. 
In Schimper's experiments seeds of Dodonaea viscosa germinated 
after floating in a 3^ % solution of salt for 60 days, and Hibiscus 
seeds germinated after 121 days. Similar experiments have shown 
that other widely distributed strand-plants possess a much feebler 
floating capacity. According to Schimper the seeds of Euphorbia 
Atoto float for 4 to 5 days only ; Pemphis acidula seeds, as Guppy 
demonstrated, sink at once when freshly fallen, and if left to dry 
for 14 days they float only for 2 to 5 days. The cones of Casuarina 
equisetifolia are said to float only for 1 to 2 days. While the short 
floating period of 2 to 5 days is clearly insufficient to admit of the 
transport of the seeds of the latter plant to islands situated a con- 
siderable distance from the mainland, it is long enough to account 
for its occurrence in Krakatau. The distance of the Krakatau islands 
from the coasts of Java and Sumatra and many islands in the Sunda 
Strait region is comparatively trifling. The island of Sebesi, which 
was only partially deprived of its vegetation by the eruption of 1883, 
is only 19 km. [12 miles] from Krakatau and only about 15 km. 
[9 miles] from Verlaten and Lang islands. The distance of Krakatau 
from Seboekoe is only slightly greater. To the nearest points of the 
coast of Sumatra, Telong Kelapa and Varkenshoek, the distance is 

1 Gappy, H. B., loc. cit. The Solomon Islands, London, 18S7, p. 305. [The 
subject of seed-dispersal is exhaustively treated by H. B. Guppy in his more recent 
book, Observations of a Naturalist in the Pacific between 1896 and 1899, Vol. n. 
London, 1906.] 



Ocean-currents 55 

37 and 40 km. [23 and 25 miles]. To Java's Third Point the distance 
is approximately the same ; and to the northern point of Prince 
island it is 43 km. [27 miles]. 

Fruits and seeds of strand-plants may therefore be easily trans- 
ported to the shores of the Krakatau islands by currents, which are 
not constant in direction, from all the neighbouring - coasts of Java 
and Sumatra as well as from the islands in the Sunda Strait and in 
the Java Sea. The transport of floating plants and portions of plants 
by the current which sets to the south-west can be accomplished 
under favourable conditions in less than a day ; more especially is 
this the case from the northern entrance to the strait, from the 
Sumatran coast at Varkenshoek, the Zutphen islands, from the island 
of Dwars in the channel, St Nicholas Point and Java's Fourth Point 
on the coast of Java. During the east monsoon the direction of this 
current remains constant for 18 hours ; in the broader and middle 
part of the strait/ in the direction of Krakatau, its velocity is at least 
3 km. [1*8 miles] an hour and thus a transport for a distance of more 
than 50 km. [31 miles] is possible between two tides. Seeds and fruits 
with feeble floating capacity may thus be carried direct to Krakatau. 
It should be added that other possible means of transport such, for 
example, as Guppy has described in reference to the colonisation of 
the Cocos islands, are not excluded. 

Guppy has shown that small seeds of strand-plants such as 
Tournefortia argentea, Scaevola Koenigii, Pemphis acidula, etc. 
occur with sand in the crevices and cracks or in the holes 
and burrows made by molluscs and worms in stems and branches 
stranded on the beach. Seeds, like sand, are blown by the wind 
into every available cranny. The stems and branches are again 
floated off by high tides or storms and thus the seeds and fruits 
concealed in the crevices are transported to new localities without 
losing their power of germination. 

By this method of seed-dispersal it is possible, therefore, for 
strand-plants, the seeds of which do not possess special floating capacity, 
to take part in the colonisation of new coast-regions : inland plants 
may be introduced by the same means. 

There are also other methods by which germs may be trans- 
ported across water. 

Inundations and high tides on the coast and, in the interior, 
swollen rivers frequently carry freshly uprooted trees into the sea. 
The earth entangled in the mass of root above the surface of the 
water may contain various seedlings and seeds,, also Grasses and 
Cyperaceae ; epiphytes on the branches of the floating trees are out 
of reach of the injurious effects of sea-water. By the same means 



56 Means of Dispersal 

different kinds of animals may be carried across water. Semon 1 
attributes an important role to this means of distribution in the case 
of animals in the Malay Archipelago. The possibility of certain kinds 
of animals accomplishing a long sea voyage on floating wood has been 
demonstrated by the observations of Guppy, who states that in the 
course of a few years four living snakes were drifted to the Cocos 
islands on bamboo stems and tree trunks ; he records one instance 
of the transport of a crocodile on a large tree stem to the beach 
of the islands. 

Tree stems and branches played an important part in the colonisa- 
tion of Krakatau by plants and animals. Large piles of floating 
trees, stems, branches and bamboos are met with everywhere on the 
beach above high-water mark and often carried a considerable 
distance inland. Some of the animals on the island, such as the fat 
Iguana (Varcmus Salvator) which suns itself in the beds of streams, 
may have travelled on floating wood, possibly also the ancestors 
of the numerous ants, but certainly plants. On one of the trees 
stranded on the beach a long time ago I found the two tubular 
fungi Polystictus sanguineus and P. hydnoldes. Their mycelia 
had apparently survived the sea voyage in the interior of the wood 
and had since produced a considerable number of fructifications, 
those of the blood-red P. sanguineus being met with a considerable 
distance away. 

The blocks of pumice, which have been noticed since the great 
outburst on all coasts of the Sunda Strait and farther away on the 
beaches and covering the surface of the water in quiet bays, may, 
as Guppy states, serve for the transport of small fruits and seeds. 
Floating blocks of pumice and pieces lying on the beach may be 
swept by high tides as far as the strand-forest or to the sandy ground 
where the small fruits and sand collect in their numberless depressions 
and holes as in the crevices of floating wood. A succeeding tide 
carries back the pumice blocks with their freight of plants and they 
are drifted by currents to other coasts. The germination of Pem- 
phis acidida, Scaevola Koenigii and Triumfetta procwmbens from 
seeds hidden in the cavities of pumice has often been observed on the 
Cocos islands. That this means of distribution must have played a 
more important part in the colonisation of Krakatau than in the Cocos 
islands, is shown by the great quantity of pumice which is not only 
piled up on all the neighbouring coasts but also covers large areas in 
the Sunda Strait and is frequently drifted back again to its place 

1 Semon, R 1m Australischen Busch und an den Kiisten des Korallenmeeres, 
Edit, ii., Leipzig, 1903, p. 349. 



Ocean-currents 57 

of origin, the island of Krakatau, where it is strewn with other 
jetsam of the sea along the drift-zone (PI. IV., fig. 3). 

All these different possibilities of transport over water, the com- 
paratively short distance separating Krakatau from the coasts of 
Java, Sumatra, and other plant-covered islands, and especially the 
unusually favourable current-conditions have contributed to the 
result that the germs of a large number of plant species have been 
carried in a short time to the shores of Krakatau. The plants so 
introduced include species with seeds which are not adapted, or 
only in a slight degree, to dispersal by water. In addition to widely 
distributed strand-plants the Krakatau strand-flora includes also less 
well defined strand-species. 

The number of species of the strand-region (67) appears small in 
comparison with the number included in the Indo-Malayan strand-flora 
(ca. 320). Several typical and widely-spread members of the Pes-caprae 
and Barringtonia formations are still unrepresented. We searched in 
vain, for example, among the Spinifex bushes for Tacca pinnatijida, 
with its beautiful foliage, which occurs in abundance on the island of 
Edam. The handsome bushes of Crinum asiaticwn, which decorate 
with their white flowers the Barringtonia forest, do not occur, nor the 
tall Calotropis gigantea which in other places is a common plant on 
sandy beaches. The latter is an Asclepiad with large violet flowers, 
and seeds covered with long, shiny and silky hairs which distinguish it 
as one of the few sea-shore plants adapted to wind-dispersal. Even 
more noteworthy is the absence on the beach of Krakatau of the 
whole Mangrove association which is so rich in species characterised 
by morphological and ecological peculiarities. The absence of these 
and other typical strand-plants is attributable to different causes. In 
some cases the species do not occur, or only in small numbers, on the 
stretches of coast which supplied most of the fruits drifted to Kra- 
katau. Others may have reached the beach but failed to find the 
requisite conditions on the pumiceous and ash-streAvn ground. The 
fruits and seeds which we found most frequently in the drift-zone of 
Krakatau and Verlaten island are those mentioned in the lists given 
by Treub and Penzig ; they are represented in the new strand-flora by 
many individuals, some of which have already reached the fruiting 
stage. Other plants drifted to the shore in considerable quantity 
produce a few seedlings, which, however, as is the case of Nipa 
fruticans and like the large seedlings of Rhizophora which are washed 
up on to the beach, fail to develope further. The absence of certain 
strand-plants like Nipa and the Mangrove plants, the seeds of 
which reach the island but do not survive, is due to the special con- 
ditions which prevail on the shore of the island. Another type of 



58 Means of Dispersal 

selection, the destruction by animals of certain seeds and fruits among 
the drift-material, especially by hermit and other crabs, as Schimper 1 
and Guppy 2 have described in the case of other coasts, does not 
appear to have been operative in this instance. The small hermit- 
crabs which live in gasteropod shells, the busy peregrinations of 
which I have had an opportunity of noticing on the beach of 
Sumbawa and Noesa Kambangan, are not found on Krakatau or on 
Verlaten island. There appears to be no evidence of the occurrence 
of crabs such as Guppy has described as subsisting chiefly on the drift- 
fruits and seeds on the beach of the Cocos islands, though the name 
"Crab Island" formerly applied to Krakatau suggests their former 
occurrence. Out of fifty to sixty living seedlings of different species of 
strand-plants met with in the drift in the Cocos islands only about a 
dozen species escaped destruction by crabs, with the result that, despite 
the richness of the drift-material, a strand-flora containing only a 
small number of species was produced. On Krakatau a number of 
plants have succeeded which belong to species the fruit, seeds and 
seedlings of which are most eagerly sought after by crabs : for example 
Cerbera Odollam, Calophyllum, Carapa, Cocos nucifera. The large 
number of coconut palms on Krakatau is an especially remarkable 
feature. Statements occur in the literature 3 to the effect that coconuts 
from drift-material seldom germinate ; moreover in many places empty 
nuts only occur in the drift-zone. These nuts have not all been opened 
by crabs ; the presence of a circular opening, from 1 to 2 cm. in diameter, 
on many of them shows that the fruits were eaten by squirrels, which 
are common in the Archipelago, before their transport in the water. 

2. Seed-dispersal by birds. 

In addition to transport by water some of the strand-plants of 
Krakatau may have been introduced by birds. According to Guppy 
the seeds of Pemphis aeidula adhere freely to the feathers of birds 
which build in the bushes of the coast vegetation or obtain nesting 
material from them ; in many instances the seeds of Krakatau plants 
may have been introduced in the bodies of birds. 

The following plants included in the Krakatau list, Ximenia 
americana, Eugenia, Premna, Cassytlia filiformis, are among those 
mentioned by Hemsley as having been found by Guppy and Moseley 4 
in an uninjured condition in the crops and intestines of fruit-eating 
birds. Schimper considers that Morinda eitrifolia and Scaevola 

1 Schimper, A. F. W. Indomalayische Strandflora, p. 75. 

2 Guppy, H. B., loc. cit. p. 11. 

3 Engler, A. Entwicklangsgeschkhte der Pflanzenwelt, n. p. 183. 

4 Hemsley, W. B., loc. cit. Challenger Reports, Botany, Vol. i. pp. 43, 44. 



Birds 59 

Koenigii are possibly distributed in this way; further, the fleshy 
fruits of Clerodendron inerme, Viteoc Negundo, and Vitis trifolia 
serve as food for fruit-eating birds which frequent beaches and 
forests. In the case, therefore, of nine of the strand-plants the fruit 
is adapted for dispersal in the bodies of birds. Bearing in mind the 
fact, as stated by Guppy and Beccari 1 , that fruit-eating birds are often 
not over-critical in their choice of food, and do not feed exclusively 
on fleshy fruits, and that the large size of seeds is not a fatal obstacle 
to their being swallowed, it is probable that a still greater number 
may be distributed endozoically. The inhabitants of the Cocos islands 
often find the large spherical seeds of Caesalpinia Bonducetta, a 
Leguminous member of the Krakatau strand-flora, in the stomachs of 
frigate-birds. Seeds of considerable size (e.g. Muscat nuts) are often 
met with in the crops and stomachs of fruit-eating doves, and Beccari 
records the discovery of the seeds of a palm, Omnia aruensis, 6 cm. 
in diameter, in the stomach of a Cassiowary. 

The importance of the dispersal of seeds in the crops and stomachs of 
birds over long distances has often been called in question in view of 
the very short interval, in the case of many birds, between eating and 
ejecting their food. Kerner 2 found in thrushes' dung numerous seeds 
of Ribcs three-quarters of an hour after the berries were eaten. Seeds 
of Elder (Sambucus)?Lre known to have been ejected after an interval 
of half an hour. The interval in the case of most birds is 1^ to 3 
hours. In spite of the short period of digestion which characterises 
fruit-eating doves their co-operation in the colonisation of Krakatau is 
by no means impossible ; many birds fly with a velocity of 50 kilometres 
an hour [31 miles], while doves may cover 80 or more kilometres 
[50 miles] in an hour. It is therefore not impossible that birds which 
have eaten fruit on the coastal regions of the Sunda Strait may 
excrete digested but uninjured seeds on Krakatau after less than 
an hour's flight. 

Among the plants in the interior of the island there are un- 
doubtedly several which have reached the island by the agency of 
birds. The seeds of various species of Ficus in particular owe their 
introduction to transport in the stomachs or crops of birds. 

Schimper considers that the fig-trees which are abundant in the 
inland regions of the Malay Archipelago owe their distribution to 
this agency, and Guppy attributes the fact that fig-trees constitute 
with Casuariua the commonest and most important trees in the 
interior of the small coral islands of the Solomon Archipelago to the 

1 Beccari, O. Malesia, Vol. i. p. I. 

2 Kerner, A. Pflanzenleben,\i. p. 800. [The Natural History of Plants: English 
translation, edited by Prof. P. W. Oliver, Vol. n. p. 864.] 



60 Means of Dispersal 

dispersal of their seeds by fruit-eating doves. Penzig 1 has demonstrated 
the introduction of Melastoma polycmthwm by bird-agency. Among 
the latest arrivals on the island there is no doubt that Trema 
amboinensis, one of the Celtidoideae with small juicy fruits, must be 
included in the list of plants introduced by animal-agency. Carica 
Papaya, which occurs on Verlaten island, in addition to its dispersal 
by birds may also be carried by flying foxes (Pteropus) which, according 
to statements by Forbes (Joe. cit. p. 34), are capable of extended flight 
over water. As already pointed out, the fact that Verlaten island was 
inhabited for a short time some years ago renders it possible that this 
favourite plant in cultivation was introduced by man. 

3. Dispersal of fruits and seeds by wind. 

The third method of dispersal of fruits and seeds, by wind, is of 
exceptional importance as a factor in the development of the new 
flora of Krakatau. This was demonstrated in a remarkable way 
during Treub's first visit to the island. Previous to the publication 
of the results of the first Krakatau expedition of 1886, opinions in 
regard to the part played by wind in the colonisation of new land, 
especially in the case of distant islands, were divided 2 . The view was 
widely held that the dissemination of spores and seeds by air-currents 
was only of local importance, and only assumed a geographical 
significance after frequent repetitions in the course of generations. 
This opinion was based on many observations on the colonisation 
of freshly exposed surfaces on the mainland where ground had 
been either partially or completely deprived of vegetation and 
afterwards colonised from neighbouring districts. Patches of new 
ground may be formed by earthquakes, floods, the accumulation of 
detritus-cones, piles of boulders, glacial moraines in the mountains, 
sandbanks in river-beds and at the mouth of rivers and by the 
formation of lava- and ash-fields in volcanoes. Seeing that the action 
of wind as a factor in the dispersal of vascular plants 3 falls behind 
other agents of distribution when the newly exposed land is com- 

1 Penzig, 0., loc. cit. p. 111. 

2 Vide Schimper, A. F. W. Pflanzengeographie, 1898, p. 90. [Plant Geography, 
p. 80.] 

3 In the Alps, where disturbances in the surface of the ground occur much more 
frequently than in the plains, the anemochoric species (that is, those which owe their 
seed-dispersal to wind) predominate; Vogler ["Uber die Verbreitungsmittel der 
schweizerischen Alpenpflanzen," Flora, Bd. 89, 1901, p. 73 (Reprint)] has supplied a 
particularly good example of this, supported by statistics, in his account of the 
spread of vegetation over the ground which was left bare by the shrinkage of the 
Rhone glacier. 



Wind 61 

paratively near to plant-covered areas, at least in flat regions, it is 
intelligible that the possibility of wind-transport over great distances 
should be doubted, as, for example, the transport of seeds and spores 
to distant islands, or, at most, admitted only in the case of spores. 

The fact that a large proportion of the vegetation of volcanic is- 
lands, situated a considerable distance from continents, consists chiefly 
of ferns, and the occurrence on coral islands of ferns and certain 
species of flowering plants which could not well be introduced except 
by wind, afford evidence of the far-reaching influence of air-currents. 
There are, indeed, several observers who acknowledge the importance 
of wind-action as a factor in the colonisation of such districts. 
Engler 1 , in his work on island floras and the floras of tropical moun- 
tains, has laid stress on the view that light seeds are carried over wide 
areas in the higher currents of the atmosphere during periodically 
recurring strong winds. In his comparative treatment of the floras 
of the larger islands in the Pacific Ocean, especially of the Sandwich 
islands, he arrives at the conclusion, based on his study of the means 
of dispersal of fruits and seeds, that of the 675 species in the Sand- 
wich islands 140 spore-bearing plants and 14 seed-plants owe their 
distribution to wind ; in the case of 322 species dispersal by birds is 
possible (56 species by coast-birds ; 241 in the intestines of birds, and 26 
on their feathers). The fact that of the 669 indigenous species in the 
Sandwich islands not less than 500 (74'6 %) are endemic, demonstrates 
the exceptional dispersal of seeds by wind and by birds over such 
long distances as are in question as regards these islands. Before 
Treub called attention to the important role of wind in the dissemina- 
tion of plants, Beccari 2 had arrived at the conclusion, as the result 
of his observations in the Malay Archipelago, that a considerable 
number of species are confined to mountain-summits separated from 
one another by as much as 3200 kilometres [2000 miles], and further 
that nearly related species are separated from one another by long 
distances. 

According to Beccari the mountain-tops of the Malay Archipelago 
occupy a position where, during part of the year, particularly from 
November to April at the time of the west monsoon, the strength and 
constant direction of the wind are maintained for a longer time than 
in the lower regions and on the sea-coasts. It is therefore clearly 

1 Engler, A. Versuch einer Entwicklungsgeschichte der Pflanzenwelt, ir. Teil. 
Die extratropischen Gebiete der Siidlichen Hemisphare und die tropischen Gebiete, 
Leipzig, 1882. 

2 Beccari, O. Malesia, Vol. i. Fasc. iii., 1878, pp. 214-235. 

Beccari, O. " Beitrage zur Pflanzengeographie des Malayischen Archipels " (ab- 
stract by A. Engler). Bot. Jahrbiicher, i. Bd., 1881. 



62 Means of Dispersal 

possible that the north-west monsoon may carry dust and small dust- 
like seeds from the western part of the Archipelago to the peaks of 
the eastern islands. In this connexion Beccari calls attention to the 
long distances which volcanic ashes (eruption of Tamboro at Sum- 
bawa in 1815) may be carried by currents in the upper regions of the 
atmosphere; he also gives figures indicating the lightness of such 
seeds as he considers may be distributed by wind. A seed of Nepen- 
thes phyllamphora weighs 0'000035 grammes, seeds of Rhododendron 
verticillatum and Dendrobium attenuatum 0*000028 gr. and 
0*00000565 gr. respectively. As the north-west monsoon in the Malay 
Archipelago has a high intensity it is easy to understand why Rhodo- 
dendron, Nepenthes, and other plants peculiar to the mountains of 
the western region and to the mountains of Java occur on the 
mountain-summits of the Moluccas and New Guinea, and why, for 
example, several Alpine Indian plants are met with on the Pangerango 
(Gentiana quadrifaria BL, Ranunculus javanicus Reinw., Ranun- 
culus diffusus D.C., Valeriana javanica BL, Primula imperialis 
Jungh., Gnaphalium javanicwm Reinw., etc.). Beccari considers that 
these have been carried by the north-west monsoon, to some extent 
also by birds, from regions further west, first from Sumatra, and 
thither from the mountains of India. He attributes very great 
importance to the north-west monsoon, which is especially prevalent 
from November to April, as a factor in the transport of seeds, more 
particularly from the west part of the Archipelago to the eastern 
islands. 

The observations of Junghuhn 1 on the conditions of the monsoon 
wind in Java are not consistent with this conclusion. The west or 
north-west monsoon, which produces cloudy weather in Java from 
December to February, extends, according to Junghuhn, only a short 
distance above sea-level, at most up to 1600 metres [5250 ft] on the 
slopes of the mountains; while, on the other hand, the south-east 
monsoon blows the whole year round in all parts of the atmosphere 
at an altitude above 2000 metres [6600 ft.]. During the period of 
twelve years during which he observed the direction in which the 
steam-clouds of the volcano are drawn out as stripes in the atmo- 
sphere reaching miles in length, he found that this is always towards 
the west, W.N.W., sometimes W.S.W. and never towards the east, 
not even when, in the months of January and February, a strong 
westerly or W.N.W. wind brings the heaviest rain-showers over the 
low alluvial flats. His remarks in another passage (loe. cit. p. 408) 
diminish, to some extent, the force of these conclusions: he writes, 

1 Junghuhn, F. Java, seine Gestalt, Pfianzendecke and innere Bauart, Leipzig, 
1852, Bd. I. p. 165. 



Wind 63 

" The south monsoon wind blows steadily at these altitudes (7500 
10,000 ft.) the whole year, but as a rule it decreases in force at night 
or entirely drops. It frequently shifts from its normal direction to 
east-south-east, east and east-north-east and in the course of the day 
it increases spasmodically in intensity. During the rain-monsoon it is 
replaced by a north-west wind which blows at this season in the valleys, 
and this occurs the more rarely the higher the peak on which the obser- 
vations are made. On mountains of 10,000 ft. and higher I have never 
noticed a west wind, but at a height of 1)000 9500 ft. this was occasion- 
ally observed. The north-west wind then ascends the slopes on the 
opposite side of the conical mountain, covering everything with a dense 
cloud, and blows over the peak. But on these higher peaks it rarely 
retains the ascendancy which it has wrested from the east monsoon for 
more than half a day or at most a whole day. . .then the latter reasserts 
itself and an interval of several weeks or months elapses before the west 
wind succeeds in rising to so high a level." As my own excursions on 
the volcanic mountains of Java were made at the time of the west 
monsoon, November to March, I was able to convince myself of the 
correctness of Junghulm's conclusions. The south-east wind prevailed 
everywhere (Gedeh mountains, Dieng and Tengger mountains in Java, 
Merapi and Singalang), though I once had an opportunity of observing 
on the old crater of Aloen-Aloen of the Gedeh mountains a strong 
west monsoon wind accompanied by mist and cloud. Verbeek also 
states (Krakatcm, n. Teil, p. 149) that in Java the wind in the upper 
currents of the atmosphere blows constantly from the east (S.E., E. 
and more rarely N.E.) and this is the case when either an east or west 
wind is blowing in the lower strata of the air. He estimates the 
lowest limit of this high wind at 2000 metres [6600 ft.]. He is also of 
opinion that its velocity increases with the height and, on the data 
furnished by the distances to which ashes were carried during the 
Krakatau eruption, he estimates the velocity at an altitude of 50 
kilometres [31 miles] at 121 kilometres [75% miles] per hour. In 
other regions also, as, for example, in the Swiss Alps, Vogler 1 has 
demonstrated the possibility of wind-transport over long distances. 

From the results of numerous calculations as to the transport 
of leaves, etc., on glaciers and snow-fields in relation to the deter- 
mination of the nearest normal station of the plants, Vogler arrives 
at the conclusion that during storms seeds may be carried in the 
Alps to a distance of 20 kilometres [12 J miles]. As evidence of the 
probability of transport to a still greater distance, even in the case of 
fairly large seeds and fruits, he quotes the remarkable hail of salt on 

1 Vogler, P. " Uber die Verbreituugsruittel der schweizerischen Alpenpflanzen." 
Flora, Bd. 89, 1901. 



64 Means of Dispersal 

the St Gotthard which occurred on August 30th, 1870, when crystals of 
salt fell, weighing in some cases 0*76 grammes ; these had been brought 
by air-currents from North Africa or from the nearest points on the 
sea-coast, a distance of at least 250 kilometres [156 miles]. 

The stone-rain of February 20th, 1907, at Trelex sur Nyon, which 
Rollier 1 has described, is a more recent example of the same pheno- 
menon. White quartzose pebbles as large as peas and hazel-nuts 
were carried by air-currents from some region rich in siliceous rocks, 
presumably from the south of France or Spain, that is for a distance 
of more than 100 km. [62 miles]. 

The best proof of the transport of plant-germs over large 
distances is afforded by the observations on the colonisation of 
Krakatau. In this case we have definite proof of long-distance dis- 
persal: Sebesi, the nearest island with plants, is 18'5 km. [11^ miles] 
distant, and the nearest points of Java and Sumatra are situated 40*8 
and 37' 1 km. [25^ and 23 miles] respectively from Krakatau. 

The results of Treub's investigation of the island in the year 1886 
have already been described (pp. 6, 7). The first colonisation of the 
volcanic cone, and of the interior generally, was effected by entirely 
different means from that of the shore-region, and almost exclusively 
by the introduction of plant-germs by wind-agency. Cells of blue- 
green Algae, Bacteria, Diatoms, the spores of Liverworts, Mosses, 
and Ferns, and the seeds of at least six of the eight phanerogams 
which Treub found in the interior of the island were carried by air- 
currents. The first phase of colonisation was characterised by the 
predominance of Ferns, which were represented by 11 species widely 
distributed in the Indo-Malayan region. Since then there has been 
a considerable increase in the number of wind-borne species including, 
in addition to Ferns, members of the Gramineae, Cyperaceae, and 
Orchidaceae. 

Penzig estimates that the following seventeen species (32 / o of 
the total flora), recorded from Krakatau up to the year 1897, were 
introduced by the agency of wind : all the Composites (eight species : 
Wedelia asperrima, Wedelia scabriuscula, Blv/mea balsamifera, 
Blumea hieracifolia, Pluchea indica, Vemonia cinerea, Emilia 
sonchifolia, Wollastonia sp.), five species of Gramineae (GymnotJirix 
elegans, Phragmites Roxburghii, Imperata arundinacea, Saccha- 
rum spontancum, Pogonatlievum orinitmn), and the four Orchids 
(Spathoglottis plicata, Vanda Sulingi, Arundina speciosa and 

1 Rollier, L. "Une pluie de pierres survenue a Trelex (Vaud) le 20 fevrier, 1907." 
Archives des sciences physiques et naturelles, Oct. et Nov. 1907. (Comptes rendus 
des travaux presentes a la 90 session de la Societe helcetique des sciences naturelles 
a Fribourg, 1907, p. 73.) 



Wind 65 

Phajus sp.). He includes the Cyperaceae (Cyperus digitata, 
Fimbristylis spathacea, Lipocarpha foliosa) and the two Grasses, 
Spinifex squarrosus and IscJiaemum muticum in the group of 
" roophilous species," that is, species distributed by water. In April 
1906 the floras of the three islands included twelve Composites 
{Conyza august ifolia, Conyza indica, Erechthites hieracifolia, 
Wedelia glabrata, Senecio sp. 1 introduced since 1897); six Gramineae 
(excluding Isclmemum and Spinifeoc; Peunisetum elegcms added since 
1897) ; four Cyperaceae (Mariscus umbellatus, a new arrival since 1897) 
and five Orchids (Cymbidium Finlaysonianum since 1897). In the 
case of all these 28 species (30 % of the phanerogam flora) wind-agency 
has probably been the means of transport; in some instances other 
means of dispersal are also possible and were perhaps concerned in 
the colonisation of Krakatau. Of these 28 presumably wind-borne 
species, some are found also in the strand vegetation of Krakatau and 
occur on the coasts of Java and Sumatra as often as in the interior. 
The possibility of transport of the fruits by water is by no means 
excluded, at least as regards such members of the flora as Conyza 
indica, the species of Blumea, Wedelia and Wollastonia which are 
especially common on the beach and are reckoned by Schimper among 
the typical strand-plants. In the flora of the island of Edam, and at 
localities on the coasts of Java and Sumatra which we visited, Compo- 
sites were not uncommon ; on Edam we found six (two of which occur 
also on Krakatau, Vernonia cinerea and Wedelia glabrata) ; at Vlakke 
Hoek, the ubiquitous strand-plant Wedelia glabrata ; at Java's First 
Point four (three of which, Blumea bcdsamifera, Wedelia glabrata 
and Vernonia cinerea occur also on Krakatau). Some of the Grasses 
included in the list occur not only in the coast-flora of Krakatau, but 
are also common in that of Java, Sumatra and elsewhere: Imperata 
arundinacea, for example, is mentioned by Hemsley as a strand-plant 
which owes its distribution to sea-currents. On the other hand he 
expresses doubt as to the efficacy of this means of dispersal in the case 
of Composites, while Schimper lays stress on the fact that the small 
fruits of most of the strand Composites and those of the species 
Wedelia biflora, with the widest oceanic distribution, are not provided 
with a pappus and are therefore ill-adapted for dispersal by wind. 
We cannot go far wrong if, without accepting his argument against 
wind-dispersal as convincing, we follow Schimper in admitting that 
some of the Composites of the strand -flora may have been carried 
by sea-currents. 

1 Senecio sp., presumably also Conyza indica, Conyza angustifolia, the species 
which were found by Treub in 1886. (Treub, loc. cit. p. 218, "deux especes de 
Conyza.") 

5 



66 Means of Dispersal 

In the dispersal of seeds and fruits by wind over long distances, 
structural adaptations to flight are of less importance than reduction 
in weight. The greater the velocity of the wind the more efficient 
it is as an agent of seed transport. Seeds which are unaffected by 
the wind in the Swiss plains, or are carried for short distances only, in 
higher regions, as Vogler has shown, are blown much farther. The 
upper limit of weight of " light seeds " capable of flight is higher in 
the mountains where the winds are stronger than in the valleys where 
lighter winds prevail. Vogler considers that in the case of winds 
having a velocity of 30 metres [98 ft.] a second, a special apparatus 
for flight is unnecessary. Winds reaching this velocity are not in- 
frequent during storms in the Indo-Malayan region. In the Sunda 
Strait district it is possible, therefore, that light seeds and fruits 
which possess no special flight-apparatus may be dispersed by wind. 
Observations in Krakatau demonstrate that for dispersal over wide 
areas seeds with special structural adaptations (pappus-structures of 
the Compositae, hair-like flight-organs in the Gramineae, seeds with 
a membranous border as in the Orchidaceae) have an advantage. 
Very light seeds specially adapted to wind-dispersal, such as those 
of Orchids, the spores of Ferns and other cryptogams, are carried 
by the ordinary monsoon wind, while the introduction of larger and 
heavier seeds, some of which have no special flight-organs, is the result 
of more violent storms and cyclones. 

4. The part played by the several agents of dispersal in the 
development of the present flora of Krakatau. 

It is clear from the above enquiry into the significance of the 
various means of dispersal of plant-germs in the colonisation of the 
Krakatau islands, that the classification of the plants so far discovered 
according to their methods of distribution is by no means easy and 
cannot in any sense be carried out within sharply defined limits. As 
regards the five Orchids, which most probably owe their introduction 
to air-currents, other means of dispersal (as, for example, in crevices 
in tree stems) cannot be entirely excluded, and this applies to other 
presumably wind-borne plants, the seeds, or such vegetative parts 
of which as are capable of reproducing the species, may have been 
carried in the roots or tangle of branches of floating wood. Grasses 
and Cyperaceae, which are often found on the beach and in swampy 
places, may have been introduced on the feet or feathers of swimming 
and marsh birds. In the case of the strand-plants also, as already 
stated, in addition to the characteristic method of distribution of the 
fruits and seeds by currents, which has in several instances been 
demonstrated as the means of dispersal, there are possibilities of 



Means of Dispersal 67 

introduction on floating wood, on pieces of drifted pumice carrying 
sand and seed, while some of the plants may have been introduced by 
birds. Of the total number of phanerogams found on the group of 
islands up to 1 906, 36 (39%) have certainly been brought by ocean- 
currents. If we include such Krakatau strand-plants as belong to 
genera with well-known halophytic species and such typical strand- 
plants as may possibly have been distributed by birds, together with 
strand species of Compositae, Grasses and Cyperaceae, which may 
have been introduced by sea-currents as well as by wind and birds, 
the number of plants included in this group is brought up to 67, or 
72 % of the total. 

The number of plants brought to the islands by birds cannot be 
exactly estimated. It is almost certain that the nine inland species 
(10 % f the total) mentioned on page 58 and possibly nine species 
in the list of strand-plants were introduced by this means, that is 18 
species in all or 19 % of the whole flora; this estimate does not take 
account of the possible part played by marsh and water birds in the 
dispersal of Grasses and Cyperaceae. 

The data in regard to the number of wind-distributed species are 
equally doubtful. If we include only the Orchidaceae, the Gramineae, 
with the exception of Spinifex and Ischaemum, also Mariscus 
iimbellatus among the Cyperaceae, and excluding all the Composites 
which occur on the strand, the number amounts to 15 species or 
16 % j including all the Composites and the four Cyperaceae, 
28 species or 30% of the total. 

The facts given in the list of the Krakatau flora in regard to the 
distribution of individual plants show that they are almost without 
exception species which are ubiquitous in the tropical zone or at all 
events in the Malay Archipelago. Any attempt to explain the 
occurrence of the few species which are not widely distributed, by 
reference to the prevailing currents and winds from Java, Sumatra, 
and the other islands of the Archipelago, must for the present at 
least prove futile. This is due to the fact that the floras of the 
different localities in Java and Sumatra with which we are concerned 
and of the other islands in the Java Sea and Sunda Strait are too 
little known. 

Of the total number of phanerogams, according to the method of 
reckoning adopted, 39 72 % have been introduced by sea-currents, 
10 19% by birds, and 16 30 % by air-currents. In order to 
appreciate correctly the importance of the dispersal of germs by wind- 
agency it is necessary to bear in mind that the Ferns, of which there 
are 16 species, also the lower cryptogams, almost without exception 
(see Polystictus, p. 56) were introduced by this means. Wind- 



68 Formation of Plant-Associations 

borne species constitute 37 / (25 phanerogamous plants, 16 ferns) of 
the vascular plants. The large number of Ferns and other cryptogams 
is obviously explained by the fact that the prevailing winds in this 
region serve for the dispersal of germs over a distance of approximately 
30 kilometres [18^ miles], while as regards more distant islands the 
transport of even the lightest germs is effected only by unusually high 
winds and is therefore of comparatively rare occurrence. This is in 
accordance with the remarkable fact that in the Cocos islands, which 
have several phanerogams in common with Krakatau, Ferns are entirely 
absent and only three cryptogams, a moss {Hypnum fuscens, Hook, 
and Am.), a fungus (Polyporus luridus, Fries), and a lichen are re- 
corded by the three naturalists Darwin, Forbes, and Guppy who 
have visited the islands. 

VI. The succession of plant-associations and the future 
character of the vegetation of Krakatau. 

The comparatively advanced state of differentiation of the vegeta- 
tion into plant-associations or formations is no less surprising than 
the remarkably large number and the variety of species in the new 
flora of Krakatau. As Penzig showed, the development of plant- 
associations had already begun in 1897. On the beach the plants of 
the Pes-caprae formation predominated. In the interior of the 
island the vegetation presented the appearance of a grass-steppe. 
Ferns constituted the dominant plants on the slopes of the cone. 
Since 1897 the aspect of the vegetation has undergone considerable 
change ; the strand-flora is divided into two formations. An outer 
zone of varying breadth, reaching in places to the tide-level, consists 
of low creeping grasses and herbaceous plants, bushes and shrubs; 
the typical Pes-caprae formation. Behind this rises the strand- 
forest (Barringtonia formation), the composition of which is not 
yet equal in variety of species and in gloomy grandeur to the 
Barringtonia strand-forests on the coasts of Java and Sumatra, 
nor will it soon reach the same level. Neither of these strand- 
formations is as yet closed. Grasses, Cyperaceae, Ferns and 
Composites spread from the grass-steppe of the interior through 
clearings in the forest to the lower carpet of Ipomaea and Spinifex, 
while in other directions groups of strand-plants have penetrated 
inland for a distance of 300 500 metres. The beautiful group of 
coconut palms, 400 metres from the shore-line, represented in the 
photograph (PL VI., fig. 7, p. 30), affords an example of the latter. 
Groups of older plants of Barringtonia, Calophyllum, and Casuarina 
occur at various distances from the shore, while others, young coconut 
palms and Pandanus clumps, are so near the edge of the sea that their 



Formation of Forests 69 

stems are washed by the waves at high tide. The strand vegetation 
on the south-west corner of Krakatau, where it is most widely spread, 
is composed of elements of different ages, the oldest of which occur 
for the most part toAvards the interior, the youngest nearer to the 
tidal zone (see, for example, PI. V., fig. 5). This distribution of the 
recent littoral flora over a relatively broad zone is most readily ex- 
plained by the gradual growth of the island in the shore-region, a 
gradual seaward extension of the shore-line in the course of years. 

Measurements taken by Verbeek proved that even during the first 
few months after the eruption there were considerable alterations in 
the sea-floor all round the Krakatau islands. Some of the pumice and 
masses of ashes were carried hither and thither by high seas : some 
sandbanks which were formed shortly after the outburst completely 
disappeared, while in other places the light and easily moved material 
was piled up into new submarine hills and banks or deposited on the 
shores of the three islands. In this way the flat sandy shore has re- 
ceived important additions on the south and west coasts of Krakatau 
and on the south coast of Verlaten island. These accumulations of 
material on the beach remain, though reduced in size. It is obvious 
that the oldest strand-plants, which sprang from the seeds and fruits 
from the drift formed in the first year, have been gradually separated 
from the beach by a constantly increasing belt and that during this 
shifting of the shore-line new plant-germs were introduced with the 
pumice and took part in the formation of the present discontinuous 
strand-forest. Other factors may of course have been concerned in 
the building up of this forest, such as are responsible for the 
spreading of the strand-plants above the normal drift-zone in coral 
islands or other coast-lines, but these factors afford a less probable 
explanation than that already suggested. It is, for example, hardly 
conceivable, considering the present state of the fauna of Krakatau, 
that fruits and seeds were carried inland from the drift-zone by 
animal-agency. It has, however, elsewhere been shown that crocodiles, 
lizards, and turtles, that is, animals of which some already occur on 
the island, are of importance from the point of view of plant-dispersal. 
Beccari states that lie found a large quantity of Pandanus fruits in 
the stomach of Loplwra amboinensis, and that in Borneo certain 
turtles constantly eat the fruits of a Durio and deposit the seeds 
with their excrement. On the other hand the agency of crabs, by 
which, according to Guppy, the germs of certain plants, especially 
those of Morbida dtrifolia, Herncmdia peltata, and Cordia sitbcor- 
data, have been spread over the interior of the Cocos islands, may be 
disregarded, as the seeds and fruits (Cocos, Barringtonia, CalophyUvm, 
Pandanus) which have been carried farther inland are those which 

53 



70 Formation of Plant-Associations 

crabs most eagerly search for and which can least withstand their 
attacks. 

The level ground behind the strand-forest, gently sloping towards 
the foot of the cone, as well as the lowest ridges and valleys of the 
mountain, are still occupied as they were ten years ago chiefly by 
Grasses, Cyperaceae and Compositae, while the Ferns have already come 
to occupy a subordinate place. Two representatives of the phanerogams 
of the shore (Scaevola Koenigit and Tournefortia argentea) were 
found by Treub in the interior. Since then the trees and shrubs have 
increased in number in the steppe or desert-like regions. These have 
advanced either singly or in groups on to the flat ground beyond the 
strand-forest and, as we have already described, they have formed 
forest-like patches in the ravines of the cone. 

If the further development of the present Krakatau vegetation is 
not interrupted by a fresh volcanic outburst, the island, with the 
exception of the steep rock-face, may be completely clothed with 
vegetation in the course of the next fifty or sixty years. 

The volcano of Tamboro in the island of Sumbawa has become 
covered afresh with a dense forest within a similar period. In the 
shore-zone the extension of the forest-formation will lead to the 
disappearance of clearings which are occupied by herbaceous plants 
and bushes. During the development of a closed Barringtonia 
formation, some of the present members of this association will in 
the future have a difficult task in competing with the growth of 
new species. The building up and completion of the formation 
will, as elsewhere, be accompanied by a reduction in the number 
of species. Less well equipped forms will disappear or will be 
driven towards the shore, where they will mix with plants of the 
Pes-caprae formation and in some places oust them from their 
position. Low or slow-growing trees and shrubs which can no longer 
flourish in the high Barringtonia forest may spread inland almost 
unhindered. Those plants which have hitherto been facultative 
strand species, possessing seeds or fruits which, though not definitely 
wind-borne, may be carried inland by wind for short distances, will 
rapidly spread towards the interior ; similarly other plants, as, for 
example, the different species of Ficus, the fruits of which are readily 
eaten by birds, will spread in the same direction. It is possible that 
the forest in the principal gorge of the mountain is at present com- 
posed of these elements of the coast-flora ; perhaps future visitors to 
the island may find there many other plants, the germs of which have 
been introduced by birds, but more especially by wind, from the 
neighbouring islands and not from the littoral zone of Krakatau. 
We may indeed expect that plants will eventually be found in the 



Future Developments 71 

higher localities which have not, like those which we collected, come 
from the strand vegetation and from the low-lying parts of adjacent 
islands but from the higher regions of the Javan and Sumatran 
mountains; plants with light seeds which have been carried from 
the high volcanic cones of Java by strong winds which blow at the 
higher altitudes, especially by the south-east winds which prevail 
during the greater part of the year. Above all we may expect to find 
in the future those wind-distributed and animal-distributed species 
which in Java and Sumatra take possession of patches of ground in 
which volcanic eruptions have destroyed all traces of vegetation. 
In such situations, as Schimper 1 has shown in the case of Goenong 
Goentoer and as I propose to describe 2 in a further account of 
the colonisation of volcanic areas in Java and Sumatra (Gedeh, 
Pangerango, Papandajan, G. Goentoer, Dieng and Tengger mountains 
in Java, Merapi and Singalang in Sumatra), are found Grasses, Cypera- 
ceae, Ferns, and Orchids, also shrubby and arborescent phanerogams 
with wind-distributed seeds and fruits, especially species of Rhodo- 
dendron and G)tapha/i><m, while other plants, Varcirnum, GauUeria, 
Myriea, Aralia, etc., are distributed chiefly by birds. Many of the 
latter plants which live in the forests as epiphytes, assume the habit 
of ground-plants on a volcanic substratum where there is little com- 
petition with other plants, and at a later stage, when the vegetation 
becomes denser and arborescent plants occupy the ground, they revert 
to an epiphytic manner of life. 

In the mountain forests, which extend both upwards and down- 
wards, new conditions of life are produced. Spores of cryptogams and 
seeds of phanerogamous plants, which have not as yet met with con- 
ditions necessary for germination and growth, at a later stage form 
new elements in the flora. Lianes, epiphytic mosses, ferns and orchids 
make their appearance. The rocks on the mountain slopes become 
clothed with liverworts and mosses in shady places, and lichens spring- 
up in more sunny situations. The mycelia of mould-fungi and species 
of the Phalloideae and Agaricineae flourish in the decaying leaves 
on the ground of the forest. Possibly the bleached saprophytic 
flowering plants and parasites may also obtain a footing on branches 
and roots. 

Man plays no part either in opposing or accelerating this develop- 
mental process. The west regions of Java, and the whole of the 
southern regions of Sumatra are still sparsely populated ; many fertile 

1 Schimper, A. F. W. Pflanzengeographle, p. 201. [Plant Geography, p. 185.] 

2 Ernst, A. "Die Besiedelung vulkanischen Bodens auf Java und Sumatra." 
To be published in Vegetationsbilder, by G. Karsten and H. Schenck, Jena, 1908. 
7 Reihe, Heft 1 and 2. 



72 Formation of Plant- Associations 

areas are everywhere ready to hand to industrious settlers and 
Krakatau will long remain, as it was before the eruption, uninhabited 
and will be visited only for a short time by a few fishermen or by 
explorers. A fi*esh growth will continue to spread from the shore 
and from the slopes of the mountain, the grass steppes of the inter- 
mediate zone will grow less and less and finally disappear. At last 
after a long interval the vegetation on the desolated island will again 
acquire that wealth of variety and luxuriance which we see in the 
fullest development which Nature has reached in the primaeval forest 
of the tropics. 



ADDENDUM I 

(Footnote, p. 29.) 

Lotsy states in his Vorlesungen iiber Deszendenztheorien, Pt. ii. p. 479 
(G. Fischer, Jena, 1908), that an old Cycas found by Dr Valeton on the island a 
few years ago is supposed to be the only remnant of the original vegetation. As the 
results obtained during the expedition of 1905, in which Dr Valeton took part, have 
not been published it is impossible to say whether the " Old Cycas " is identical with 
the specimen which we found on the beach of the south-east coast of Krakatau. 
Although our plant had reached a considerable size relative to the short existence 
of the new flora, it certainly does not belong to the original vegetation of the island : 
it occurs on that part of the littoral zone which was formed as a result of the eruption 
of 1883 



ADDENDUM II 

(Footnote, p. 34.) 

While the English translation was in the press, Mr Verbeek informed me in 
a letter that on a third visit to the island of Krakatau, he succeeded in taking 
a good photograph of the middle part of the steep rock-face. A print) with a short 
explanatory note, was afterwards forwarded by the government of the Dutch East 
Indies to those libraries which had officially received a copy of his work on Krakatau. 
The copy at my disposal did not contain this photograph : hence the above statement. 
I take this opportunity of thanking Mr Verbeek for information which he kindly 
supplied at my request on this and other points. 



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