Plants, seeds, and currents in the West Indies and Azores; the results of investigations carried out in those regions between 1906 and 1914

Preface

With the exception of the section on the Azores, this work was practically completed before the war began; and it is now presented very much as it was written in the pre-war period. Unfortunately I greatly under-rated the task involved in the production of the fair copy; and for this reason, as well as through sickness and other causes, there has been considerable delay in its preparation for the press.

Associated with my observations on seeds and fruits, the results of which were published in 1912 under the title of Studies in Seeds and Fruits, the work embodied in these pages represents about ten years of my life. The two winters of 1906-8 were spent in Jamaica, that of 1908-9 mainly in Grenada but also in Tobago and Trinidad, and that of 1910-11 in the Turks Islands. Subsequently two sojourns were made in the Azores, the first from the middle of February to the end of April 1913, and the second from the middle of June to the middle of August 1914.

The great lesson that I have learned from the numerous difficult distribution-problems presented in the West Indian region, is that one can no longer fight shy of accepting in principle the conclusions relating to past changes in the arrangement of land and water in the Caribbean area, which have long been formulated by English and American geologists and zoologists. The witness of the living plant is often quite as insistent as the testimony of the rocks. Yet, although the original holders of such views stood more or less alone in their advocacy of them forty or fifty years ago, some of them, like Mr. Lechmere Guppy, who died recently at Port-of- Spain, lived to see their final justification.

The inclusion of the Azores within my field of investigation arose from a desire to come in contact with some of the problems presented by the floras of the Atlantic Islands. In the previous decade, 1896-1906, I had been brought face to face with problems offered by the islands of the Pacific. Polynesia and the history of its plant-stocking had occupied much of my thoughts during a long period, and I turned to Macaronesia with the hope that as typified in the Azores this region might bring me once again under the spell cast by the problems of oceanic distribution. Yet the outlook was at first far from encouraging, and it was suggested to me that it was scarcely worth while to take up the study of islands, concerning which we had long known all that was worth knowing. However, a re-perusal of Hooker's famous lecture on insular floras whetted my curiosity, and I soon found that the Macaronesian vi

PREFACE islands were rich in distribution-problems almost as fascinating as those presented by Hawaii and other Polynesian groups.

Yet but few of these problems were directly indicated in the catalogues of the floras accessible to me ; and I realised here, as I did in the Pacific, that the work of the systematist in framing a catalogue of a flora represents the means to an end and not the end itself. In other words, with a list of a flora in our hands we stand only at the threshold of the study of distribution. Here also I realised that there is no region so well known that it would not greatly benefit by a thorough overhaul of all the data from a generally accepted standpoint of distribution; and the conviction forced itself upon me that the student of distribution will find his task nearest-at-hand, not in the discovery of new facts, but in the elaboration of old ones, and in the adoption of a uniform method of treatment. The elimination of the introduced plant should be the first goal of the student of distribution. Yet it is not possible for him to procure intelligible results, since he employs one method for the British Islands, another for the Azores, another for New Zealand, and a fourth for the Hawaiian Islands. The story of the weed all over the globe is full of significance, but only for the student of the early history of man.

H. B. Guppy.

"Bosario" Salcombe, South Devon.

LIST OF SOME BOTANICAL AND OTHER WORKS QUOTED IN THESE PAGES IN CON- NECTION WITH DISTRIBUTION IN THE WEST INDIAN REGION AND ELSEWHERE

(Other lists dealing with special subjects are given at the end of chaps, ii, iii, xi, xiii, xv, xix.)

Catesby, M., Natural History of Carolina, Florida, and the

Ernst, A., The New Flora of the Volcanic Island of Krakatau, trans.

by A. C. Seward, Cambridge, 1908.

p^^^A^B jFlora of Jamaica, vol. iii. 1914.

Grisebach, A. H. R.. Flora of the British West Indian Islands, 1864.

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

Plant-Dispersal, 1906 (vol. ii. of Observations of a Naturalist in the Pacific).

Plant-Distribution from an Old Standpoint, Trans. Vict. Inst., London, 1907.

Distribution of Plants and Animals, Petermann's Mitteilungen, 1910, heft 2.

Studies in Seeds and Fruits, 1912.

Harshberger, J. W., Phytogeographic Survey of North America (Engler and Drude's Die Vegetation der Erde, vol. xiii. Leipzig and New York, 1911).

The Vegetation of South Florida, Trans. Wagner Free Institute of Science of Philadelphia, 1914.

Hart, J. H., Herbarium list, Botanical Department, Trinidad, 1908. Hemsley, W. B., Reports on the Scientific Results of the Voyage of H.M.S. Challenger, Botany, vol. i. 1885 (reference to this work is often abbreviated to Chall. Bot.).

Hooker, W. J., The Niger Flora, 1849, including sections by G.

Bentham, J. D. Hooker, and others.

Millspaugh, C. F., Plantae Utowanae, 1900 (plants collected in the Antillean cruise of the yacht Utowana).

Plantse Yucatanae, 1903-4.

Flora of the Sand-keys of Florida, 1907.

Praenunciae Bahamenses, 1906-9.

(All publications of the Field Columbian Museum, Chicago.)

vii viii LIST OF SOME BOTANICAL AND OTHER WORKS

S afford, W. E., Classification of the genus Annona, Contributions from the United States National Herbarium, vol. 18; Smithsonian Institution, Washington, 1914.

(Numerous botanical papers by this author, which are of great importance both to the botanist and to the student of the races of man in the tropics of the New World, have appeared in the last few years in the Journal of the Washington Academy of Sciences, 1912-15; in the Volta Review, Washington, 1912; in the Bulletin of the Torrey Botanical Club, 1912 ; in the Journal of Heredity, Washington, 1915; and in the Smithsonian series of publications above named.)

Scharff, R. F., Distribution and Origin of Life in America, London, 1911.

Schimper, A. F. W., Die Indo-Malayische Strandflora, Jena, 1891.

Spruce, R., Notes of a Botanist on the Amazon and Andes, 1908 (edited by A. R. Wallace).

Contents

CHAP. PAGE

I WEST INDIAN BEACH-DRIFT 1

II WEST INDIAN DRIFT ON EUROPEAN SHORES ... 20

Chapter I

The study of the stranded seed and fruit-drift of the West Indian region, as in the case of my previous investigations in the Pacific Islands, offered a means of approaching the great problems of plant distribution. The inquiry was extended over four winters (1906- 1911), and was principally carried out in Jamaica, the Turks Islands, Trinidad, Tobago, and Grenada. The last winter was spent in the Turks Islands with the object of studying the seed-drift most fitted for the traverse across the North Atlantic in the Gulf Stream, since in those small islands one is able to discriminate with confidence between the drift of local Origin and that brought from outside regions by the currents.

Generally speaking, the drift has much the same character over all this region, except perhaps in Trinidad and the adjacent island of Tobago, where there is added a quantity of strange seeds and fruits brought by the Equatorial Current from the Amazon and the Orinoco and from the estuaries and shores of the Guianas and Brazil. It is also highly probable, as is shown in the discussion of the bottle-drift data in a later chapter, that West African seed-drift is transported by the same current to the West Indies ; but there are obvious difficulties in the way of recognising it, since most of the littoral plants that constitute the principal sources of the drift are common to both sides of the tropical Atlantic.

Its Sources. — The seeds and fruits found in the floating drift of these seas are derived partly from plants growing on the beaches, partly from plants of the n angrove swamps, and partly from inland plants growing on river-banks and on the slopes above. They are to be found in quantities on the beaches, especially in the vicinity of estuaries. But the scanty materials stranded on the coasts of Europe, as described in Chapter II., are but the residue of a vast amount of vegetable debris brought down by rivers to the coast and washed off the beaches by the currents. By far the greater mass of these materials must soon find a resting-place amongst the deposits at the bottom of the sea in the vicinity of their source.

B

The Sifting Process. — This sifting out of the less buoyant materials is well illustrated when we compare the vegetable drift thrown up on the small islands of the Turks Group with that deposited on the beaches of the larger islands in the neighbourhood of estuaries, as in the case of the Orinoco drift piled up on the south side of Trinidad, or, to take a less conspicuous example, of the drift stranded on the south coast of Jamaica in the vicinity of the Black River. These matters will be mentioned in a later page; but here it may be said that the foreign drift, which makes up nearly all of the larger materials stranded on the Turks Islands, presents us with the seeds and fruits that are most likely to be carried in the Gulf Stream across the Atlantic. The beach-drift of this small group displays the West Indian drift in transit at an early stage of the North Atlantic traverse.

If we desired to know what seeds and fruits of the floating drift of the West Indian seas we ought to find on the shores of Europe, we must look for them, not on the beaches of the larger islands where they would be mixed with and sometimes lost among a mass of vegetable materials of local origin, but on the coast of some low, scantily vegetated, outlying islet standing well removed from the main islands. Such an islet would receive on its beaches a sample of the drift after it has lost all the less buoyant constituents during a flotation of some weeks in the open ocean. These are just the opportunities which are offered in the several small islands and islets of the Turks Group. Here in sample we see the oceanic drift that is carried swiftly by the Gulf Stream through the Florida Channel and then past Cape Hatteras eastward to the shores of Europe.

General Description of Drift. — With this object in view I will at first generally describe West Indian beach-drift, referring in passing to some of its special characters in particular localities.

In the West Indies, as elsewhere, the local drift is generally predominant, that is to say, the drift derived from plants growing in the vicinity, whether at the border of the beaches, or in the coastal and estuarine mangrove swamps, or in the interior along the sides of rivers. It is from the beaches near a large estuary that we can form the best idea of the nature of the materials that any particular region supplies to the currents for oceanic transport. If we confined our attention entirely to the drift brought down by rivers, or to the materials supplied by shore vegetation, our conception of its general composition would be incomplete. It is on a beach near an estuary, where the seeds and fruits derived from the beach plants are mingled ' with those from the mangrove vegetation and from the riverside plants of the interior, that we can learn our lesson concerning local drift.

Yet this would take no cognisance of the foreign drift, the materials brought from a distance, often from a continental coast or from some island hundreds of miles away. This is liable to be masked by the local drift on a beach near an estuary. It is best sought for and most easily recognised on some long stretch of beach far from an estuary, since it is often not difficult there to differentiate between it and the drift supplied by the beach vegetation. But here again obstacles may arise. Some knowledge of the flora must be acquired, and in a large island like Jamaica this is not a light undertaking. Even with Grisebacfrs Flora of the British West Indian Islands at my disposal, a work that bears especially on Jamaican plants, it was not possible to say with certainty that three of the most interesting plants represented in Jamaican beach-drift, Carapa guianensis, Manicaria saccifera, and Sacoglottis amazonica, though not accredited to the island, did not still survive in some of its extensive coastal swamps. It will, however, be subsequently shown that in the light of more recent investigations the probability of their not existing there is very great.

These are difficulties likely to crop up in the case of all large tropical islands. Yet the incrusting cirripedes, Serpulce, and other organisms will frequently aid us in determining whether any particular fruit or seed is from beyond the sea. It is only the outlying sand-key, such as occurs in the Turks Islands, that affords the opportunity of safely differentiating the foreign drift on a beach. Here after a few weeks spent in examining the local flora there is little or no trouble in making the discrimination.

The riverside vegetation above the mangroves, the mangrove formation of the estuary and of the coast swamp, the plants of the beach and its border, all contribute to the floating drift of these seas.

River-drift above the Mangroves. — A good deal of the materials brought down by the river, and I have in this sketch the Black River of Jamaica chiefly in my mind, consists of aquatic plants, such as Pontederias and Pistias, and of foliage, portions of tree-branches, etc., which do not count in distribution, and in the case of the floating plants are soon destroyed by the salt water or dry up when stranded on the beaches. These aquatic plants form a special feature of the floating drift of rivers of tropical America, and I have referred to them in the instance of the Guayas River in Ecuador in my book on Plant Dispersal (p. 488). Yet the plants of the riverside and of the wooded slopes of the river-valley above the mangrove-bordered estuary add a great variety of fruits and seeds to the drift floating in the stream, as illustrated in the description of the Black River given near the close of this chapter.

Many of these floating fruits and seeds have little or no effective value for distribution except along the same river-system. Thus in the Black River drift occur in numbers the germinating fruits of Grias cauli 'flora, the germinating seeds of Symphonia globulifera, of Crinnm. and of Crudya spicata ; and one may add the seeds of Fevillea cordifolia, which even when they escape the fate of germination in the river-drift are far from suited for dispersal over the sea. It is of importance to remember that through this tendency to germinate when afloat many of the seeds and fruits of the drift of tropical rivers are rendered useless for purposes of dispersal even across narrow tracts of sea.

But amongst the fruits and seeds found afloat in West Indian river-drift, excluding those supplied by the mangroves and their associates, many others have no effective value for purposes of distribution. Although the gourds of Crescentia trees and the fruits of Acrocomia palms are characteristic of this floating drift, the first named carry seeds that have a fleeting vitality and the second float only for a few days. Acrocomia fruits, it is true, are represented in the drift of the Turks Islands, but merely in the form of the empty 44 stones," which, after being freed by the decay of the outer coverings of the stranded fruit, acquire buoyancy only through the loss of the seed. Then again both Andira inermis, a tree of the riverside, and Mammea americana, a tree of the forested slopes of the river- valley, add their fruits as a rule to the floating drift ; but it is very doubtful whether their seeds would be fit for germination when the fruits are stranded on some distant island.

The fruits and seeds carried down by a West Indian river from the interior to the sea that would be fitted for crossing unharmed a broad tract of ocean are comparatively few. Taking all the kinds of seeds and fruits brought down to the sea by the Black River from its basin above the mangroves, I don't suppose that twenty per cent, would be capable of reproducing the plant after a traverse of a hundred miles of ocean. The seeds which are brought down by a Jamaican river from the interior to the coast in a sound condition and capable of sustaining without injury the effects of prolonged flotation in the sea, would include such leguminous seeds as those of Entada scandens, Mucuna urens, and Dioclea reflexa, all of which figure in the West Indian drift stranded in a sound condition on the shores of Europe. Then there would be the 44 stones " of Spondias lutea and the long pods of Cassia grandis, which, after they have been transported by the rivers to the sea, would still be able to carry some of their seeds unharmed far across the ocean.

Drift supplied by the Mangrove Formation. — We come now to the vegetation of the mangrove formation as a source of the floating drift of West Indian seas. We have to distinguish here between the true mangroves and their associates. Together they form colonies everywhere, whether on the surface of some newly raised islet or key, or on the coast, or in the estuaries of the larger islands. Rhizophora mangle, Laguncularia racemosa, and Avicennia nitida are the mangrove trees proper ; and one of their most prominent characteristics is their viviparous habit, which, however, is less pronounced with Laguncularia than with the others. The occasional associates of the mangroves in the larger islands are Anona palustris and Carapa guianensis. In Trinidad we find also Manicaria saccifera and Sacoglottis amazonica together with a species of Bactris, a palm that grows in similar situations. The Manicaria and Sacoglottis trees are conspicuous constituents of the estuarine floras of the great rivers of Venezuela, the Guianas, and Brazil. Though they only just enter the West Indian region, their fruits are distributed by the currents far and wide over the Caribbean Sea.

All the above-named trees of the mangrove swamps contribute to the floating drift of these seas, the true mangroves being represented in the case of Rhizophora by long seedlings, in the case of Avicennia by the germinating fruits and seedlings, and in that of Laguncularia by the fruits, which are often in the germinating condition. Uninjured by flotation in sea- water these seedlings and germinating fruits are cast ashore, and very soon establish themselves.

On the other hand, with the associates of the mangroves the floating fruit or seed has many difficulties to contend with that considerably restrict its capacities for distribution. Thus the seeds of Anona palustris and of Carapa guianensis are very apt to germinate when afloat in river-drift ; and my observations indicate that the germinating seed would soon be killed when it reached the sea-water, though the dead seed might float a long time and be thrown up in a more or less empty or unsound condition on some distant shore. So again with Manicaria saccifera, the seeds do not seem to be able to withstand sea- water immersion for a long period, though the fruit with a decaying or dead seed may be transported by the currents for a great distance. Sacoglottis amazonica is rather better adapted in these respects,

Drift supplied by the Plants of the Beach and its Borders. — In the last place we will deal with the plants of the beach and its borders that add their buoyant seeds and fruits to the drift of the West Indian seas. Those which are most generally distributed, being those which are most characteristic of the drift, are enumerated below. In point of size the drift derived from beach plants in the West Indies offers a great contrast to that supplied by the beach vegetation of the tropical islands of the Indian and Pacific oceans. In the West Indies we miss the large fruits of Barringtonia speciosa, Cerbera cdollam, Ochrosia parri flora, Heritiera littoralis, Cycas circinalis, Pandanus, etc., trees that give character to the vegetation of the beaches of many an island and many a tract of continental coast in those oceans. The largest fruits of the common West Indian beach-drift, such as those of the Manchineel (Hippomane mancinella), Thespesia popv.lnea, and Ecastaphyllum brozvnei, are not more than lj inches (37 mm.) across ; and most of the other plants contribute seeds and seed-like fruits varying from a sixth to three-quarters of an inch (4-18 mm.) in size.

The Beach Plants commonly represented in the Floating and Beach Drift of the West Indies.

(One or two of the plants, like Conocarpus erectus, are perhaps most characteristic of the borders of the mangrove swamps, but since they thrive also amongst the vegetation bordering the beach they are here included.)

Canavalia obtusifolia (seeds).

Chrysobalanas icaco (stones).

Coccoloba uvifera (stone-like fruits).

Colubrina asiatica (seeds).

Conocarpus erectus (achenes).

Ecastaphyllum brownei (legumes).

Guilandina bonducella (seeds).

Hibiscus tiliaceus (seeds).

Hippomane mancinella (stones).

Tpomoea pes-caprce (seeds).

Scoeiola plumieri (stones).

Sophora tomentosa (seeds).

Suriana maritima (seed-like nucules).

Thespesia populnea (seeds liberated by the decaying fruit). Tournefortia gnaphalodes (pyrenes).

Vigna luteola (seeds).

There are one or two trees typically represented in West Indian beach-drift which ought to be mentioned, their fruits being carried long distances by the currents, such as Terminalia katappa and Cassia fistula. Both have been introduced from the Old World. The last named is discussed at length on a later page. The first is dealt with in my book on Plant Dispersal. It is a typical littoral tree of the tropics in the eastern hemisphere ; and in the West Indies it is tending to escape from cultivation to find a home on the beach.

Cirripedes, Serpulce, and similar organisms, that have attached themselves to floating drift, often enable one to distinguish the larger seeds that have been brought from a distance before being stranded. Where the plants concerned grow in the neighbourhood it is not easy, as before remarked, to discriminate between the foreign drift and the drift of local origin. The difficulties are well exhibited in an island like Jamaica. The large seeds of Entada scandens are common on the beaches of the north coast; but the plant grows in the island, and one cannot in the absence of incrusting shells of marine organisms determine whether a weather-beaten seed lying on the beach came originally from some neighbouring coast, such as from Cuba, or whether it has acquired its weathered appearance from lying exposed for a long period on the shore. On the other hand, the fruits of Manicaria saccifera and Sacoglottis amazonica would be rightly regarded as of foreign origin, since there is little probability of the plants growing in the island.

The Sorting Influence of the Waves. — The waves often sort out the finer beach-drift, and deposit it in a line above the larger and heavier fruits and seeds which are usually mixed up with Sargasso weed, drift-wood, and similar materials. Small pumice pebbles and Spirula shells mark the line of deposition of the smaller seeds and fruits belonging to such plants as Hibiscus tiliaceus, Ipomcea pescaproB, Suriana maritima, Tournefortia gnaphalodes, Vigna luteola, etc. It is, however, the larger drift that usually claims attention, the smaller materials being often overlooked.

From my observations at St. Croix, Turks Islands, Grenada, Tobago, Trinidad, Jamaica, and Colon, it is evident that the beach-drift displays much the same general characters over the West Indian region. At the same time in addition to the seeds and fruits that are found on most of the coasts, whether insular or continental, each locality often presents some peculiar feature. Thus on the Colon side of the Panama Isthmus there are to be found on the beaches the large fruits of Prioria copaifera and empty palm fruits of Astrocaryum, etc. In Jamaica we find the fruits of Grias cauliflora ; and in Trinidad the ordinary seeds and fruits of the drift are often masked by the large amount of strange fruits and seeds brought down by the Orinoco and stranded on its south coast.

Method of Identifying the Constituents of the Drift. — My previous experience of the seed-drift of the islands of the Pacific and more especially of the American borders of the ocean, as in Ecuador and at Panama, had made me familiar with many of the constituents of West Indian drift. On the other hand, my later West Indian experiences helped me to identify constituents in the drift on the Pacific coasts that I had not before recognised. The method employed was to search for the parent plant. In some cases a long time passed, as in that of Dioclea reflexa, before success crowned my efforts. This plant is of particular interest, as it is one of the few possessing seeds that are transported by the Gulf Stream in a sound condition to the shores of Europe. Ultimately I tracked it to one of its homes in the mountains of Grenada, and one of my chief objects of making a sojourn of some weeks in that locality was to investigate the conditions that led to its supplying its seeds to the drift.

The same plan was followed in Jamaica whenever I came upon some new seed or fruit on the beaches. With the aid of my coloured companions, who were very zealous in helping me to find its source, it was often not very difficult. Thus it was not long before I found the parent plants of the Anchovy tree (Grias cauliflora) and of the large seeds of the Antidote Vine (Fevillea cordifolia) so common on beaches in the Black River district.

Certain seeds and fruits common in the Jamaican drift eluded my efforts in this direction, and usually because the plants did not grow in the island. Two conspicuous offenders in this way were the fruits of Sacoglottis amazonica and Manicaria saccifera, two of the most interesting components of West Indian beach-drift. However, I was introduced to them by the late Mr. Hart of Trinidad. The source of the fruits of the first named was for a long time unknown, and Mr. Hart played a prominent part in the inquiry that led to their identification. Though not Jamaican, both are included in the Trinidad flora, growing mostly as I learnt in the swamps on the south side of the island. But as found on the Trinidad beaches the fruits often display evidence of long flotation in the sea in the marine organisms incrusting them. They have their chief home in the swamps of the Amazon and the Orinoco, and many of the fruits found in the Trinidad and Tobago beach-drift are doubtless thence derived. It was the presence of these fruits of Manicaria and Sacoglottis on the beaches of the south coast of Jamaica that long ago led Sir D. Morris to recognise an element of drift hailing from the Orinoco and the Amazon, a subject dealt with in connection with Jamaican beach-drift in a later page.

Orinoco and Amazon Drift distributed over the West Indian Region. — " Orinoco drift " is a term often on the lips of residents in Trinidad, Tobago, and Grenada. They apply it to all the drift brought by the Equatorial Current, much of which must come from the Amazon as well as from the shores of Brazil and of the Guianas. Most of this drift finds its way into the Caribbean Sea between Barbados and the Spanish Main, either entering the Gulf of Paria and emerging through the Bocas, or floating through the passages separating Trinidad, Tobago, and Grenada. As indicated by the bottle-drift data, to be dealt with in a later chapter, most of the vegetable drift carried by this current would be borne across the Caribbean Sea in the direction of the coasts of Honduras. The materials that escaped being stranded on the shores of Central America or on the south coast of Jamaica, on the Cayman Islands, and on the south-west shores of Cuba, would be carried through the Straits of Yucatan into the Gulf of Mexico, some portion being beached on the shores of that gulf, the remainder ultimately reaching the Straits of Florida.

Reference will subsequently be made to several bottles that have accomplished this passage in part, and to others that have done so in its entirety. Occasionally one of them stranded on the beach tells the story of the seed-drift lying around it. Thus, a bottle from Ceara on the north coast of Brazil, which Mr. Savage English mentions as cast up on Grand Cayman, clearly demonstrates the part played by the Equatorial Current in carrying drift to the Cayman Islands. " The quantity of living seed afloat at this western end of the Caribbean Sea " (thus he writes in the Kew Bulletin, 1913) " must be immense, for it is hardly possible to examine more than a few feet of the windward beaches of Grand Cayman without finding a seed of some sort ; leguminous, probably, if it is not one from a Manicaria palm, though there are plenty of others."