84 CEYLON MARINE BIOLOGICAL REPORTS. 



belong, for instance, C. scalpeUiformis , Freycinetii, cupressoiilen, Fergusonii. In abundant individual 

 occurrence, but with very limited distribution, we have C. verticillata and loetevirens. Lastly, to the com- 

 monest and most widely distributed belong C. clavifera, uvijera, peltata, imbricata, and others; in a word, 

 all those species belonging to the very critical mccmosa group, according to Weber v. Bossb's defini- 

 nition, a variable group very difficult to define. 



If we compare the different situations in which the Ceylon species of Caulerpa grow from the point 

 of view of the character of the substratum, we shall find in a preponderating number of cases that 

 it consists of firm rocky or coral ground. But very commonly, too, Caulerpa grows on soft bottom, in 

 sand or coarse gravel formed by decomposition products of the reefs, remains of corals andlithothamnia, 

 or again in soft mud cai'ried out to sea by rivers and streams. 



2. — Different Ecolooical Types a.s distinguished by varying Develof.ments of THEixt 



Root-System. 

 (A.) C. verticillata type. 



Do the Caulerpas show any diiferences in their organization and mode of growth upon the different 

 bottoms ? 



Let us first examine C. verticillnta (fig. I), which I observed at the mouth of a river on rocks 

 partially and at times, during the south-west monsoon, entirely covered by sand and mud carried 

 out to sea, as was the case at Galle. The tufts grow in very thick masses which all arise from more 

 or less deep growing axes, now horizontally (fig. la), now obliquely growing upward (fig. 16), and which 

 higher up form side axes which grow out horizontalh'. Evidently this mode of growth is very favour- 

 able to a Caulerpa growing in localities exposed to tlie danger of being covered by sand, and this whole 

 mode of growth is quite analogous witli that of the dune grasses or certain bog mosses, which are 

 characterized by a continuous succession of djangs-off in the basal parts in proportion as they sink deeper 

 down. This comparison, first suggested by Retnke, is really very striking, and is strengthened 

 by the fact that down in the mud we find remains of verticil branches which have been killed and buried 

 in the sand. 



Through the stimulus to upward growth wliich the over-sanding exercises, this plant can always 

 keep its assimilation brandies in the hght where they stick up out of the mud and wave to and fro in the 

 swell. Thus Caulerpa verticillata seems to show, in its system of shoots, an example of an organization 

 adapted to the surroundings in which it Uves. The information about the situations wherein this plant 

 lives in other countries is very scanty. Both JoHS. Schmidt ("Flora of Koh Chang," IV., p. 104) and Collins 

 ^'Algse of Jamaica." p. 245) only mention that it grows on coral reefs without any further specification. 



Mile. ViCKERS (" Liste des Algues marines de la Barbade," p. 57) only says, 'Flaques, abritees, a 

 basse mer." Remarkable, on the other hand, is Collins's note on the /. charoides, which is closelj'^ 

 related to the main species, C. verticillnta He says of it {loc. cit., p. 245) that it grows " in soft mud 

 near Mangrove swamp," conseijuently in localities to some extent similar to those where C. verticillata 

 occurs at Galle. I5ut if, in other respects, there can be discovered any analogies in the formation of the 

 shoots, cannot of course be determined as far as this form is concerned, any more than is the case with 

 the other related Caulerpas belonging to the Vaucherioidece- and the Charoide(B-group , all of which 

 are distinguished by finer and weaker shoot systems than are to be found in otiier Caulerpas. In C. 

 verticillata, therefoie. we have found a type of Caulerpa which grows in soft, muddy bottom, where 

 the danger of oversanding is present, and I have not seen another CattZerpa-species in Ceylon belonging 

 to the same biological group, nor do any other Caulerpas occur together with C. verticillata in the 

 localities where it grows. 

 (B.) Sand Caulerpas. 



Another ty^Q of the Caulerpas that grow in a movable substratum is represented by such species 

 as C. Freycinetii, cupressoides , Lessonii , and Fergusonii. The figure of C. Lessonii (fig. 11) gives us 

 a good idea of this rhizome type, vvliich seems to be rather common among the Caulerpas and of which 



