114 TENTH ANNUAL REPORT OF 



sea plant, and tlie one most resembling a Fuciis. All the xstuavie3 

 of this district produce Delesseria Leprieurii, and a Bostrychia, either 

 B. radicans, Mont,, or a closely allied species. These last are tropical 

 forms first noticed on the shores of Cayenne, where the former was 

 found both on maritime rocks^ and on the culms of grasses in the 

 tiestuary of the Sinnamar river. With us these plants grow on the 

 palmetto logs in Charleston harbor, and on Spartina glah^a as far 

 up the river as the water continues sensibly salt. Bel. Leprieurii wa& 

 collected by Dr. Hooker at New Zealand, accompanied by a Bostrychia, 

 No other habitats for it are known. 



4tli. Florida Keys, and Shores oe the Mexican Gulf. Here we 

 have a very strongly marked province, strikingly contrasting in vege- 

 tation with the East Coast, comprised in the three regions already 

 noticed. As yet the Keys have been very imperfectly explored, and 

 we are almost unacquained with the marine vegetation of the main 

 land of Florida, Alabama, Louisiana, and Texas. Of 130 species- 

 which I collected at Key West in February, 1850, scarcely one-eighth 

 are common to the East Coast, seven-eighths being unknown on the 

 American shore to the north of Cape Florida. With this remarkable 

 difference between the Algas of the Keys and those of the East Coast, 

 there is a marked affinity between the former and those of the South 

 of Europe. The marine vegetation of the Gulf of Mexico has a very 

 strong resemblance to that of the Mediterranean Sea. Nearly one- 

 third of the species which I collected are common to the Mediterra- 

 nean. Several of them straggle northwards along the coast of Spain 

 and France, and even reach the south of England ; but scarcely any 

 of these are seen on the East coast of America. We may hence infer 

 that they are not conveyed by the gulf-stream. My collection at Key 

 West included 10 Melanosperms, 5 of which are common to the Med- 

 iterranean ; 82 Khodosperms, 25 of which are Mediterranean ; and 38 

 Chlorosperms, of which 10 are Mediterranean. Besides these identi- 

 cal species, there are many representative species closely allied to Med- 

 iterranean types. This resemblance is clearly shown in the genus 

 Basya, of which seven out of eleveyi European species are found in the 

 Mediterranean. At Key West I collected eight species of this beau- 

 tiful genus. Among these, seven were new, and the eighth (D. ele- 

 gans) is found along the whole Eastern coast of North America. Three- 

 fourths, perhaps, of the masses of seaweed cast ashore at Key West 

 belong to Laurencia, of which genus several species and innumerable 

 puzzling varieties are profusely common. A fine Hypnea {H. Wur- 

 demanni, MS.) one of the most striking species of the genus, is also 

 abundant. Alsidiumtriangulare, Dig enia simplex, Acanthophora, Aman- 

 sia mtdtijida, and other common West Indian Rhodosperms, are abund- 

 antly cast ashore. Sargassum vulgare and hacciferurriy Padina Ba- 

 vonia, Zonar'ia lohata, and sundry Bictyotce, are characteristic Me- 

 lanosperms. But this region is chiefly remarkable for the abundance 

 and beauty of its Chlorosperms of the groups SiphonacecB and Cauler- 

 pacece. Ten species of Caulerpa were collected, some of which are of 

 common occurrence, and serve for food to the turtles, which, in their 

 turn are the staple article of diet of the islanders. Penicillus (at least 

 three species), Udotea, Halimeda, Acetabidaria, Anadyomene, Bictyo- 



