Some Plants from Tropical Sea Gardens 



By MARSHALL AVERY HOWE 



Curator of the Museums and Herbarium of the New York Botanical Garden 



CVJ 



en 



A VISITOR from the north is often dis- 

 appointed by his first sight of a 

 L tropical strand, which commonly 

 shows little or no conspicuous vegetation 

 between the tide lines. Particularly is this 

 true if he is familiar with the rocky coasts 

 of northern New England, where a large 

 share of the richly abundant marine plant 

 life is exposed freely to view with every 

 ebbing tide. Probably the usual poverty 

 of the strictly littoral marine flora in the 

 tropics is due chiefly to the scorching 

 effects of the tropical sunshine, although 

 there are, of course, here as elsewhere, nu- 

 merous more or less wide areas where a 

 bottom of loose shifting sand, allowing no 

 stable foothold or anchorage, precludes the 

 development of any conspicuous vegeta- 

 tion. 



But there are also extensive rocky 

 shores, submerged reefs, and bottoms 

 strewn with old corals or calcareous peb- 

 bles, where light, heat, aeration, and suit- 

 able anchorage combine to furnish ideal 

 conditions for the development of ma- 

 rine gardens. If the observer can wade 

 into such a place at low tide, especially on 

 a calm morning before the daily trade 

 wind arises to ruffle the surface of the 

 water, the sight is one that is long to be 

 remembered. Or perhaps he can row over 

 it on one of the calm days such as occa- 

 sionally occur in late spring or in summer, 

 or can view it even in less placid weather 

 from a glass-bottomed boat at some winter 

 resort. 



In addition to the graceful, often bril- 

 liantly colored or iridescent algae — the plants 

 proper — there are commonly also in such a 

 garden stately corals and sea fans, which 

 are colonial animals. These animals, because 

 they are attached and have no more power 

 of locomotion than a tree, are ordinarily 

 looked upon as plants by the uninitiated. In 

 fact, the "sea gardens" that are exhibited 

 through glass-bottomed boats to patrons of 



southern winter resorts are sometimes almost 



exclusively "zoological gardens." Besides 



£># the colonial animals firmly attached to the 



home spot there are often also gaily colored 



tropical fish swimming in and out among 

 the other organisms and giving a touch of 

 active life to these submarine beauty spots. 



Although the adjective "tropical" is used 

 in our title and elsewhere in this discus- 

 sion, the wealth of the marine vegetation 

 in the subtropics of our North American 

 coasts and adjacent islands is probably 

 even greater than that of the tropics, 

 strictly speaking. In respect to number 

 and variety of species of "seaweeds" or 

 algae the richest areas in the northern 

 half of the western hemisphere — at least 

 the richest visited by the writer — would 

 appear to be Bermuda, the Florida Keys, 

 and the coast of California. It is possible, 

 however, that Guadeloupe,! wholly within 

 the tropics, deserves to be considered in 

 this connection. Parts of the Bahamas, of 

 Cuba, Jamaica, and Porto Bico, and of the 

 Caribbean coasts of Panama are well sup- 

 plied with marine algae, but, taken as a 

 whole, they do not give the collector the 

 impression of wealth that he obtains from 

 prowling about in the waters of the Florida 

 Keys and Bermuda. 



The "Sargasso Sea," in any such magni- 

 tude and character as was described by 

 some of the early navigators and as was 

 represented on some of the maps made only 

 fifty years ago, seems to be more or less of 

 a myth. Yet, floating mats 2 of Sargassum, 

 several feet or, rarely, several rods in 

 width are frequently met with, as one 

 steams southward from New York or Hali- 

 fax, or cruises about among the West In- 

 dian islands. Floating Sargassum is found 

 particularly in the path of the Gulf Stream, 

 which sometimes brings it far to the 

 north, occasionally casting it ashore after 



1 The algal flora of this island has been inten- 

 sively studied by Frencli scientists and the list of 

 marine species and varieties attributed to it 

 reaches the imposing total of 811, a number con- 

 siderably greater than that thus far attributed in 

 any published paper to any of the three other 

 regions. The determinations on . which the 

 Guadeloupe list is based are not altogether criti- 

 cal, however, and the sum total is swollen by the 

 inclusion of numerous varietal or form names. 



- These mats consist chiefly of two species, Sar- 

 gassum natans and S. fluitans, which are cer- 

 tainly known only in a free floating condition. 



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