1905.] NATURAL SCIENCES OF PHILADELPHIA. 695 



THE PLANT FORMATIONS OF THE BERMUDA ISLANDS. 

 BY JOHN W. HARSHBERGER, PH.D. 



No phytogeographic sketch has ever been pubhshed of this region, 

 which 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 

 about600 miles from the nearest land, Cape Hatteras in North Carolina. 

 It is evident from a study of the composition of the Bermuda 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 In- 

 dies and that region of southeastern North America where the West 

 Indian and North American types of vegetation overlap each other." 

 There being no running streams, the original flora of Bermuda was es- 

 sentially 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 con- 

 dition was when Bermuda was first discovered. The following for- 

 mations, 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 lime- 

 stone, 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, Dictyota Barteyresiana, Halimeda 

 tridens, H. tuna, Zonaria lobata, Haliseris polypodioides , Anadyomene 

 flabellata, C odium tomentosum, Neomeris dumetosus, Ulva lactuca, U. 

 latissima, Rhodymenia palmata, Padina pavonia, Galaxaura rugosa, 

 G. lapidescens and others. Those of the tidal pools formed in the 

 rock hollows are : Padina pavonia, Digenia simplex, Acetabularia cren- 



' Hemsley, W. Dotting: Report on the Botany of the Bermudas. Chal- 

 lenger Report. Botany, I, p. 14. 



