The most interesting strand plant of the open beaches of the keys along the mainland is Agave decipiens widely distributed along the strand of tropic Florida, being disseminated almost wholly by bulblets produced in place of flowers. On sandy stretches occur Hymenocallis caymanensis, Coccoloba, Ipomoea, Ernodes and Alternanthera floridana.

Shell Bank Formation. On the seaward side of mangrove islands shell banks are formed by the action of the tides and waves and these become occupied by vegetation which consists of Forestiera porulosa, Myrsine rapanea (= Rapanea guyanensis), Coccoloba uvifera and Juniperus virginiana with Iva imbricata, Cakile maritima and Ipomoea pes-caprae at the margin of the water. The shell islands of the coast consisting of oyster shells are inhabited by Yucca aloifolia, Forestiera porulosa, Quercus virens (= Q. virginiana), Opuntia pes-corvi, O. vulgaris, Mentzelia floridana, and Vincetoxicum scoparium climbs over these plants while Passiflora suberosa and Cocculus carolinus carpet the pavement of white shells. Chiococca racemosa and Psychotria rufescens also occur 1).

Cypress Swamp Formation. This formation is found in many parts of southern Florida, but nowhere better developed than in the Big Cypress Swamp west of the everglades and limited on the gulf side by the mangrove swamps which fringe the coast. It can be located by its proximity to Gallivans Bay and Cape Romano. The southeastern limit of Taxodium distichum, the principal tree of this formation, has been placed by Professor SARGENT at Mosquito Inlet (about lat. 29°) on the east coast and at Cape Romano (about lat. 26o) on the west coast, but SMALL has found it extending down the Miami River and has found it in the everglades nearby.

Little is known of the composition of this formation in Florida. The larger and smaller trees form with the lesser vegetation an almost impassable growth. The larger trees are buttressed and large root growths the so-called "knees" project from the soil or above the surface of the water. This forest is so dense that perpetual twilight is found beneath the trees and the silence is relieved only by the occasional splash of an alligator in the streams which sluggishly meander through the depths of the forest.

Everglade Formation. The everglades historically speaking may be older than the pine woods. Their origin is as follows 2):

The chain of keys surrounded by the everglades are duplicated by the outer series of Florida keys. Before these everglade hammock islands were raised to their present altitude, they were probably surrounded by a shallow sea. This being the case, we can easily account for the tropic American flora now inhabiting them. After sufficient elevation had taken place, the surrounding sea was transformed into the vast spring known as the everglades and a northern flora advanced into this area thus surrounding and isolating a totally different tropic flora. (See ante Part III, page 201, 229.)

The everglades cover an area about one hundred miles wide and perhaps one hundred and fifty miles long, the elevation being about eighteen feet above 1) CURTISS, A. H.: A Visit to the Shell Islands of Florida. Botanical Gazette IV: 117, 132, See also Bibliogr. p. 67.

154.

2) HARSHBERGER, JOHN W.: The comparative Age of the different floristic Elements of eastern North America. Proc. Acad. Nat. Sc. Phila. 1904: 613. SMALL, J. K.: Southern Florida (1907) see Bibliogr. p. 92.

sea-level. This formation consists of an extended saw-grass swamp (Cladium effusum) merging in places with pine land, prairies, cypress swamps, custard apple (Anona glabra) swamps and traversed by winding river channels, occasionally filled with water lettuce, Pistia stratiotes, with the water perfectly clear and pure, and covered with scattered hammock-lands. Its flora consists of grasses, sedges and other herbaceous plants, among which are many aquatic and mud-inhabiting species (f. e. Peltandra virginica, Saururus cernuus) less than one-half as many species as grow either in the hammocks or the pinelands. This formation partially surrounds and intersects the sandrock ridge. Structurally it consists of a marsh with scattered hammocks, while its flora is composed of plants (Apios tuberosa etc.) of far northern range and therefore mainly of a different character from those found in either the pinelands, or the hammocks, which are characterized by tropic palms, cycads, orchids and bromeliads.

The shores of the streams by which the everglades are entered are covered with rank growths of the cocoa-plum, Chrysobalanus icaco. This same species grows about the edges of the glades producing blue fruit on the eastern edge and white fruit toward the west.

Savanna- and Prairie Formation. With the appearance of level plains by the removal of the shallow sea over a sandy bottom, the isolated trees, which associated together constitute the savanna formation, appeared and clothed the ground. Imperceptibly these savannas are transformed into pine-land. When the swamps, or everglades are raised a few feet by the deposition of decaying vegetable matter and silt the character of the vegetation completely changes. Grassland is formed and the hard, rank grasses, palmetto scrub and reeds give place to growths of "blue joint”, Andropogon virginicus and other grasses (Syntherisma, Panicum virgatum) which can be used for fodder and hay.

Pine Barren Formation. (See plate VI to page 306: Southern Florida.) When the grassland is invaded by trees, pineland results, if that invasion is sufficient to close up the grassy stretches with a continuous forest growth. It may also be formed by the encroachment of trees on the savanna formation. Pinus caribaea (= P. heterophylla P. cubensis) is the dominant tree of the pine barrens associated with numerous shrubs, shrubby herbs and herbaceous perennials. The exposed coral rock of the slight elevations maintain not only more species than the slight depressions, but also more individuals, or in other words the more eroded and needle-shaped the condition of the coral rock with apparently barely enough soil to support plant life, the more diversified and abundant the vegetation. Pinus clausa occurs in the pine scrub associated with Ceratiola ericoides.

These pinelands are light and airy, the timber affording little shade. Besides Pinus caribaea several palms are conspicuous elements of the landscape, viz: Serenoa serrulata, Coccothrinax jucunda (= Thrinax argentea), C. Garberi (on dry coral ridges along Biscayne Bay), Sabal megacarpa (= S. Etonia), and Zamia floridana. The most abundant fern of the pine barrens is Pteridium aquilinum var. pseudocaudatum found in dry soil.

The keys on the western side of Bahia Honda are covered with low and thin forests composed of Pinus caribaea, Coccothrinax jucunda together with Serenoa serrulata and Myrica cerifera. The central portion of Big Pine Key, according to Stewardson Brown, is covered with Pinus caribaea (70-80 feet) with palms underneath and the same is true for Little Pine Key, while Croton linearis, Galactia volubilis, Dolicholus parvifolius, Chamaecrista grammica, Mikania heterophylla, Pteridium caudatum, Dichromena colorata and Pteris longifolia are abundant plants in the pine lands of the keys.

There are two types of pine barrens in Florida: first, the "flat woods", with numerous slight depressions, which are ponds in wet weather and are usually grown up with cypress and gum; second, the rolling barrens drained. by small streams, which are bordered by almost impenetrable thickets and stretches of swamp ').

Hammock Formation. The hammocks consist of isolated groups of hardwood trees, shrubs and vines. These hammocks have an overlying soil thicker than the pine-lands due to the accumulation of vegetal detritus, occasionally 1-2 feet deep, and they vary in size from an acre to many hundred acres, and are scattered as islands in the everglades and pine forests. The trees, shrubs and vines harbor a large number of plants of various categories. The growth of epiphytes is especially striking, for in numerous cases the tree trunks and branches are loaded with air plants, and the growth is so crowded that many of the orchids and bromeliads are forced to grow on the ground, or on the neighboring pine trees. This hammock formation includes the great majority of flowering plants now known to be common to the West Indies and Florida. The area occupied by the hammocks is insignificant as compared with that of the pineland, yet there are nearly as many species of flowering plants growing in these small areas, as there are in the vast pinelands.

SMALL2) describes a hammock which is actually being destroyed by the excessive development of epiphytes. The epiphytic bromeliads and orchids having taken possession of every available bit of surface on the larger trees have broken to the ground, where the epiphytes completely cover the floor of the hammock and the smaller trees beneath the larger ones. In addition to the bromeliad-orchid flora, the hammocks are characterized by ferns of a tropic type, such as: Polypodium incanum (on oaks), P. phyllitidis, Pteris cretica, Adiantum tenerum, Aspidium trifoliatum. Some of the species of ferns are confined to the trees, others to the curious and treacherous sink holes, while the ground is often carpeted with filmy ferns or gigantic sword ferns. Several of the hammocks are characterized by the presence of palms: Pseudophoenix Sargentii (Elliott's Key), Oreodoxa (Roystonea) regia (Royal Palm Hammock) and such orchids as Dendrophylax Lindenii (on the trunks of the royal palm), Epidendrum nocturnum, E. rigidum. The gumbo limbo Bursera simaruba is a constituent of the hammocks on Boca Chica Key. The Great Gulf Hammock according to GARBER3) yielded the following plants: Chrysobalanus oblongifolius, Galactia Elliottii, Sclerolepis verticillata, Boltonia diffusa, Senecio lobatus, Vaccinium tenellum, Sabbatia gracilis, Asclepias perennis, Sagittaria graminea, Calopogon multiflorus, Smilax Beyrichii, Dichromena colorata, Rhynchospora macrostachya, Carex gigantea, C. cherokeensis, C. verrucosa, Paspalum undulatum, Panicum gymnocarpum, etc.

1) CURTISS, A. H.: Among Florida Ferns. Plant World V: 68 April 1902.

2) SMALL, J. K.: Report upon further exploration of southern Florida. Journal New York Botanical Garden V: 157 August 1904.

3) GARBER, A. P.: The April Flora of Cedar Keys, Fla. Botanical Gazette II: 112.

The chain of everglade islands or keys are similar to the Florida Keys both in its crescent shape and in its flora. It is surrounded by the everglades, except where the upper islands touch Biscayne Bay. Before these hammock lands were elevated to their present level above the sea, they were probably surrounded by a shallow sea later transformed into the everglades. Their total area is perhaps about 150 square miles. SMALL) who has explored them more carefully than any other botanist finds that between five and six hundred species of native flowering plants occur on them. He has now established the fact that considerably more than one half of the species found on the islands south of Miami are also native in Cuba and the Bahamas, and so it happens that an older tropic flora is completely surrounded by a newer vegetation introduced from higher northern regions.

These islands, or hammocks, scattered through the everglades are covered with luxuriant virgin forests. Quercus virens (= Q. virginiana) and Persea borbonia are present in large numbers interspersed with wild lemon Citrus limonium, wild orange Citrus aurantium and the wild cucumber while on Royal Palm Hammock occur Smilax laurifolia, Salix longipes, Magnolia glauca, Ampelopsis (Parthenocissus) quinquefolia, Diospyros virginiana, Callicarpa americana and Cephalanthus occidentalis. Carica papaya, Anona glabra, Zanthoxylum Clava-Herculis are of frequent occurrence, and here and there, governed by the size and elevation of the islands, are the cabbage palmetto, Sabal Palmetto, Pinus caribaca and Ficus aurea grow to enormous size in some of the hammocks strangling other forest trees). Throughout there is a phenomenal growth of lianes. Wherever the land is dry enough, the coontie Zamia floridana flourishes.

There are several other plant formations to be recognized in southern Florida, but information concerning them is so meagre that it is impossible to give an exact statement concerning them. It is one of the phytogeographic surprises that we have such little information about a region of such marked botanic interest3).

1) SMALL, J. K.: Exploration of Southern Florida. Journal New York Botanical Garden VIII: 23-28 February 1907; Torreya VII: 83. Apr. 1907.

2) BESSEY, ERNST A.: The Florida strangling Figs. 19th. Rep. Mo. Bot. Gard. 1908: 25-33 with 9 plates.

3) In addition to the above text references see CURTISS, A. H.: The fern Flora of Florida. Fern Bulletin XII: 33-38 April 1904; Flora of the Florida Keys. Garden and Forest I: 279; BRITTON, N. L.: Explorations in Florida and the Bahamas. Journal New York Botanical Garden V: 129-136 July 1904; SMALL, J.-K.: Report on Exploration in tropical Florida. Journal New York Botanical Garden V: 49-53 March 1904; GARBER, A. P.: The April Flora of Cedar Keys, Fla. Botanical Gazette II: 112; CALKINS, W. W.: Notes on the winter Flora of Florida. Botanical Gazette II: 128; SMALL, J. K. and NASH, GEO. V.: Report upon a Trip to Florida. Journal New York Botanical Garden III: 29-35 Feb. 1902; DIX and MAC GONIGLE: The Everglades of Florida. Century Magazine Feb. 1905; WEBBER, H. J.: The water Hyacinth, Bulletin 18. U. S. Division Botany. 1897; DIMOCK, A. W.; On to Marco Pass. The Outing Magazine LIII: 397-412, Jan. 1909; COCHRANE, J. S.: A Cruise to Okeechobee. Recreation Mch. 1909: 105; SMALL, J. K.: Exploration in the Everglades. Torreya IX: 100-103. May 1909.

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3. Bermudan Region.

This region comprehends the archipelago of larger and smaller islands lying south of the Gulf Stream in the western Atlantic between 32° 14′ and 32° 23′ N. latitude and 64° 38′ and 64° 53′ W. longitude, thus being about 600 miles from the nearest land, Cape Hatteras in North Carolina. This region is placed in our classification in the West Indian section because its flora shows affinities to that region, but yet the vegetation is distinct enough with its thirten endemic species to merit its separation into a Bermudan region with such plants as Erigeron Darrelianus and Carex bermudiana with no living American relatives. It is evident from a study of the composition of the Bermudan flora, that it is of comparatively recent introduction. Briefly, says HEMSLEY): "it is not of purely West Indian origin, but was derived from the West Indies and that region of south-eastern North America where the West Indian and North American types of vegetation overlap each other". BRITTON emphasizes the fact that the flora is almost wholly West Indian and Floridan.

There being no running streams, the original flora of Bermuda was essentially of a xerophytic type. The islands have been settled so long that the character of the original vegetation has been altered and we must infer from the appearance of the flora at the present what its condition was when the Bermudas were first discovered. The following formations according to the observations of the writer) in June 1905 may be distinguished.

Marine Algal Formation. The marine algae of Bermuda are mainly those which have accustomed themselves to living on a shore composed of limestone rocks (reef rocks, or eolian rocks) exposed to the action of the surge or which live in a limestone, or coral sand in the comparatively placid water of salt water lakes, bays, or lagoons.

According to my observations, the algae of the rocks exposed to the surge are Sargassum bacciferum, Halimeda tridens, H. tuna, Avrainvillea nigricans, Anadyomene flabellata, Codium tomentosum, Neomeris dumetosus, Ulva lactuca, U. latissima, Rhodymenia palmata, Padina pavonia and others. Those of the tidal pools formed in the rock hollows are: Padina, Digenea simplex, Acetabularia crenulata, Caulerpa crassifolia, C. racemosa var. occidentalis, Ulva etc. The sandy bottoms beneath mangrove trees, or in the channels leading from salt-water sounds, or ponds to the sea are characterized by Halimeda tridens, Penicillus capitatus, Caulerpa cupressoides var. mamillosa, Padina. The salt

1) HEMSLEY, W. B.: Report on the Botany of the Bermudas Challenger Report Botany I: 14; MOORE, A. H.: List of Plants collected in Bermuda in 1905; 22 pages Cambridge March 12, 1906; BRITTON, N. L.: Bermuda in September Journal New York Botanical Garden VI: 154; SMALL, H. B.: Botany of Bermuda, 56 pages. 1900.

2) HARSHBERGER, J. W.: The plant Formations of the Bermuda Islands Proceedings Academy Natural Sciences of Philadelphia 1905: 695-700; The hour-glass Stems of the Bermuda Palmetto do. 701-704. The Comparative Leaf Structure of the Sand Dune Plants of Bermuda. Proceedings American Philosophical Society XLVII: 97-110.