THE CEYLON SPECIES OF CAULERPA. 93 



Ceylon Caulerpa forms are more or less lobed, even the deep water forms. Furthest in this respect goes 

 C. sertularioides, which has very fine branchlets, whereby the whole shoot axis has the appearance of a 

 feather (fig. 10), to which it owes its former name of "plumaris.'' Strictly speaking C. sertularioides is 

 closely allied to the radiate forms in that its branchlets are cylindiical and subulate, and it need only 

 develop these radially as in /. Farlowi or C. Selago, for the organization to be perfectly radial. 



C. sertularioides occurs on the shores of Ceylon in a number of different forms. It is very common 

 in the uppermost exposed littoral region on coral reefs and rocks in the south-west. It is often of low 

 growth with the branches at the top as if chopped off sharp (/. brevipes, fig. 7). The branches are now 

 very fine, now somewhat coarser and with coarser rhizomes. The latter seems to be the case especially on 

 sandy bottom as at Jaffna. Sometimes it also seems able to form small tufts (fig. 8). It often grows, as 

 we have said, in very exposed places, and the feather-like axes wave to and fro in the swell. It is clear 

 that such fine subulate branches are very well adapted to a species with such a mode of growth. In this 

 respect C. sertularioides corresponds with C. Icetevirens /. cylindracea, of which it also reminds us in its mode 

 of growth, even if it does not occur in such exposed places as the latter. 



C. sertularioides also occurs in the deeper parts of the Uttoral region, as for instance at Weligama, 

 from a depth of about 3 metres. Johs. Schmidt has also collected this species in 1-2 fathoms of water. 

 In this case it has a somewhat different appearance (/. longiseta). It is longer, weaker, and not chopped 

 off sharp at the top (fig. 10). I observed quite similar forms in dark cavities in coral masses on the 

 reef at Galle, so that it seems very probable, in my opinion, that this lengthening of the axis in dark 

 localities and its shortening in intensely bright must be attributed to the influence of light. 



4. — On the Difference between Morphological and Adaptational Characters in Caulerpas, 



It should follow from what has been said above that Caulerpa can scarcely, in contrast to other 

 plants, lay claim to be able to show a multitude of variable types in which no correspondence can be 

 traced between the outer form and the surroundings, which Reinke has presumed. As I think I have 

 shown, several Caulerpa species, e.g., Icetevirens, are as evident ecologisms as one could wish, and 

 different localities are characterized by different Caulerpa types. 



The different localities are characterized by differences in the bottom (sandy bottom or rock), by 

 different degrees of exposure to the swell, by different depths, and by different intensities of light — and 

 all these differences in environment correspond with differences in organization. Thus, the sand 

 Caulerpas (C. Freycinetii, cupressoides , Lessonii, Fergusonii, and others) are distinguished by their long 

 creeping rhizomes with finely branched roots, whereas the coral and rock Caulerpas (C clavifera, num- 

 mularia) are often far less elongated, and their root system consists of adhesive roots with rather few and 

 short branches. Then we find that in more exposed localities — besides that the adhesive organs are 

 more strongly developed — the assimilation axes approach the cylindrical, at the same time being very 

 narrow, i.e., offer the least possible opposition to the tearing power of the waves (C. verticillata, Icete- 

 virens, f. laxa, sertularioides). On the other hand, the branchlets are numerous and cylindrically 

 arranged so that complete exposure is favoured by the continuous movements in the swell. The 

 different depths at which the Caulerpa lives is refiected in the organization ; the deep forms are often 

 leaf-like and reach the highest dimensions (C. scalpellijormis, pinnata, taxifolia) : the surface forms 

 have a shortened axis system, while at the same time the whole assimilation system is extended at the 

 sides in one level (C. clavifera, nummularia, parvula), whereby also the assimilation discs themselves 

 strive, as it were, to extend horizontally (C. nummularia). 



Reinke, as is well known, is of the opinion that in Caulerpas there is no difference between so- 

 called " morphologischen und Anpassungsmerkmale," so that " Wer es Hebt, auf die Unterscheidung 

 von morphologischer und Anpassungsmerkmale Werth zu legen der wird daher die Speziescharaktere 

 von Caulerpa sowohl zu den ersteren wie zu den letzteren rechnen miissen." ("Ueber Caulerpa," 

 p. 68.) 



