MARINE ALGAL FLORA 269 



zosterae, mapped in Fig. 3, ranges from Guadeloupe and Colombia to 

 the northeastern United States and Canada, and to the western Eu- 

 ropean coasts. Of Rhodophyceae, Dasya pedicellata, appearing in Fig. 

 4, ranges from the Virgin Islands and Venezuela to the northeastern 

 United States but not into Canada. 



Conversely, as examples of species which range southward from the 

 Caribbean, we select from the Chlorophyceae the common Caulerpa ser- 

 tulariotdeSj which, as Fig. 5 shows, ranges from Florida and Bermuda, 

 but not the Carolinas, to south-central Brazil. It is to be remembered 

 that the Florida and Bermuda floras are almost exclusively tropical in 

 their assortment of species. Of the Phaeophyceae, Dictyota dentata^ an 

 equally distinct species, shown in Fig. 6, ranges from Florida and Ber- 

 muda to Uruguay. 



Species which are, so far as we know at the present time, limited to 

 the Caribbean and the phytogeographically similar Bermuda and Florida 

 areas are represented from the Chlorophyceae by Cymopolia barbato. 

 This plant, as Fig. 7 shows, ranges from Puerto Rico through the 

 Greater Antilles only, to Mexico, Florida and Bermuda, and is as yet 

 not known from the Central or South American mainland. Of the 

 Rhodophyceae, Herposiphonia secunda, Fig. 8, ranges from Barbados 

 and Grenada and the Venezuelan mainland to Florida and Bermuda. 



In short, then, the Caribbean flora deserves this name only because 

 the Caribbean Sea is the area of its greatest known luxuriance and di- 

 versity. It extends but a little way north, as even 1000 kilometers to 

 the north less than 12 per cent of the Caribbean forms remain; contrari- 

 wise, 3000 or 40000 kilometers east and south of the easternmost Carib- 

 bean a third of the flora is of the Caribbean type. The conclusion is 

 readily made that the Caribbean flora is actually a west or American 

 Atlantic tropical flora which, in spite of the Brazil current and the North 

 Equatorial current, extends down the Brazilian coast to Rio de Janeiro, 

 with few replacements. By the time Uruguay is reached at 35° S.L., a 

 south temperate element has replaced many of the Caribbean species and 

 the aspect of the flora has changed fundamentally. 



Comparison with areas far afield is, in the present state of algal litera- 

 ture, of doubtful value. However, for the Canary Islands, corresponding 

 in latitude to Florida, we have a list by B^rgesen (1925-30), who knows 

 the West Indies, showing a few species in common, but many more which 

 differ. The Cape Verde Islands, corresponding in latitude to the southern 

 Caribbean, have a very much higher proportion of pantropical algae also 

 found in our area, types which Feldmann has listed (1946) in his 



