THE CEYLON SPECIES OF CAULERPA. 105 



8outh-west coast of Australia and Tasmania. It is very remarkable that this species is not known from 

 the Pacific, but, on the other hand, it has been collected on the west coast of Africa (Angola), that is, 

 in the Atlantic. 



Lastly, Ceylon is the north, or perhaps better the north-west limit for two species, the central 

 distribution of which seems to be Australia, even if they also occur in the West Indies — i.e., G. laetevirens 

 and C. sedoides. For the former, the central distribution of which seems to be North and West Australia, 

 southern Ceylon is certainly the north limit. C. sedoides has similarly its central distribution in 

 Austraha, but occurs also in the Gulf of Siam ; it is also found in the West Indies. In any case, Ceylon 

 forms its north-west limit, and it occurs there only on the south coast, not in the north at all. 



We find, therefore, that the main mass of the Ceylon Caulerpa vegetation consists of many species 

 with extensive distribution (from the Red Sea in the west across the Indian Ocean to the Pacific Islands 

 in the east, together with the West Indies) , but also of several species with a more easterly main distribu- 

 tion for which Ceylon and India form the western Umit. 



Finally, the Ceylon Caulerpa flora harbours some Australian elements and one species with a 

 pronounced western distribution and, of course, the endemic species mentioned above. 



(.3) The Geographical Distribution of Caulerpa in General. 



In this last chapter we will deal with the question of the geographical distribution of the Caulerpa- 

 species in general. They belong almost exclusively to the true tropical flora, and have their main distribu- 

 tion in the tropical and sub-tropical coasts of the Red Sea, the Indian Ocean, and the Pacific, and also 

 in the tropical Atlantic (to which must be added the Mediterranean), especially the West Indies. 



But it must be noted in this connection that the Indian Ocean and the Pacific ha.rboi;r far more 

 species than the Atlantic. Of the 50 to 60 Caulerpa-s]iecies known, the majority belong to the 

 ocean area of the Indian and Pacific Oceans, which too is considerably more extensive than the tropi- 

 cal Atlantic (including the Mediterranean), which does not harbour as many Caulerpa-sipecies. Many 

 of the species belonging to the former area have a wide distribution, from the Red Sea and the east 

 coast of Africa in the West to the easterly Pacific Islands in the East. Others, however, have a con- 

 siderably more limited distribution. 



Thus, especially southern Australia, including Tasmania, is the home of several characteristic 

 and closely related species forming some very natural groups within the genus, namely, J. G. Agardh's 

 groups, Hippuroidece , Lycopodioideoe , Sedoidece pedicellatce, and Opuntioidece, of which only an occasional 

 species occurs exceptionally beyond the Australian coasts. 



Of the species that occur in the tropical Atlantic (and Mediterranean) the majority are common 

 also to the Pacific and Indian Oceans, and there are but half a dozen Caiderpa-speciea at the most that 

 occur exclusively in the Atlantic, whereas the Indian-Pacific Ocean has many (30 to 40) species thai 

 do not occur in the tropical Atlantic. 



It seems from this that it may be asserted that the genus Caulerpa, at least at the present time, 

 has its main distribution within the Indian-Pacific Ocean area. 



Very remarkable is the distribution of the species, reaching a number of about 12, which the 

 tropical Atlantic has in common with the Indian-Pacific Ocean. Of the Caulerpa-STpecies occmring 

 in Ceylon the following also occur in the West Indies : — 



C. verticillata 

 C. crassifolia 

 C. taxifolia 

 C. serhdarioides 

 C. Freycinetii 

 C. cupressoides 

 49-06 



C. davifera 

 C. uvifera 

 G. Icetevirens 

 G. Ghemnitzia 

 C. sedoides 



