THE CEYLON SPECIE8 OF (JAULERPAS. 87 



It is remarkable that O. tcetevircnn seems to live under similar conditions on the coast of Western 

 Australia as in Ceylon. Thus Harvey says (in "Phycologia Australica," I. , PI. XXX.) about C. cylindracea, 

 SoND. (=C. Icetevirens /. cylindracea. (Sond) Weber v. Bosse^ : "This plant is excessively common 

 on all the reefs at Rottnest Island, growing in shallow, exposed tidepools, as well as in sheltered spots 

 below low- water mark, and it varies much in luxuriance according to the locality." 



From these remarks it follows in any case that C. Icetevirens in Australia forms a special 

 association with its environment, especially in exposed localities, but that it also grows in deeper and 

 more sheltered places. Ajid, just as at Galle, the different forms also seem to be dependent on the 

 different localities. In what way these make their influence felt Harvey does not mention. He only 

 speaks in a few words of the variation of C. cylindracea " in luxuriance according to the locality." 



(6) The remaining rock and coral Caulerpas. 

 If, now, C. Icetevirens f. laxa is a pronounced, even though rare, example of a rock Caulerpa 

 growing in strongly exposed localities where no other alga happens to occur, on the other hand we find 

 a preponderant number of other species also growing on rocks, but in more sheltered places, where they 

 occur in company with other algae, and especially with living corals and small Actinians.* I have fre- 

 quently observed that amongst living corals and Actinians the Caulerpas must be considered as a character- 

 istic occurrence. With their long rhizomes they creep among the Actinians, and only the assimilation 

 branches are visible where they shoot up between the animal colonies. Such is the case with several 

 forms of C. clavifera, nummularia, &c. Especially noticeable is C. longistifitata (fig. 45) with its long 

 rhizomes creeping on rocks and among other algae, even if it does not occur on such strongly exposed 

 localities as C. Icetevirens f. laxa. All these have a root system without the very fine branching present 

 in the sand Caulerpas ; tlie root-branches, on the contrary, are fewer but coarser, and often as if flattened 

 at the top where they are fastened to the stones. But that there is no hard and fast difference between 

 such a root system and the one that occurs in the sand Caulerpas is best proved by the fact that the same 

 species has now the one, and now the other, depending on the substratum. Reimke has already pointed 

 this out {loc. cit., p. 58). 



3.— Different Ecological Types as distinguishbd by the varying Development of their 



Assimilation System. 



If, then, as we have already seen, there is a great difference in the root systems or adhesive organs 

 in general, at least within certain Caulerpa groups, the difference is much greater in the assimilation 

 branches and the shoot system. It is really Avith reference to this difference that Reinke ( ' Ueber Caulerpa , ' ' 

 p. 67) seems to have been led to the opuiion that the genus Caulerpa offers a special point of interest, 

 because it shows that even under similar external conditions and with essentially similar inner organiza- 

 tion, the external form can yet be variable : " AUe Caulerpen sind dem Lichtleben in Wasser angepasst : 

 jede Art ist ein Spezialfall dieser Anpasung, und alle sind verschieden geformt. Diese Verschiedenheit 

 beruht aber nicht auf be^ondere Anpassungscharakteren.t Die Assimilationsarbeit lasst sich bewerk- 

 steUigen eben so gut mit gleichartigen feinen Faden der C. fastigiata, wie mit den breiten ungetheilten 

 Blilttern der C. prolifera, den grossen fiederspaltigen Blattern der G. taxifolia und den kleinen einfachen 

 Blattem der C. racemosa und Lycopodium " . . . . and again we read : ' ' Wer es liebt, auf die Unterscheidung 

 von morphologischen und Anpassungsmerkmalen Werth zu legen, der wird daher die Speziescharaktere 

 von Caulerpa sowhol zu den ersteren wie zu den letzteren rechnen miissen." But none the less Reinke 

 has a feeling of the possibiUty that the Caulerpas may be, for all that, more or less adapted in their main 

 functions to their surroundings, and he adduces as an example how a fine-leafed species — as C. hypnoides 

 — has greater possibilities of profiting by and making the fullest use of the light in every situation than 

 for instance a C. taxifolia or C. prolifera, and these advantages show themselves chiefly in moving water. 



* These are chiefly Zoanthids.— En. | Italicised by the present author. 



