THE CEYLON SPECIES OP CAULERPA, 89 



The same may be said of G. crassifolia. I only found it once in the littoral zone of Ceylon, and then in its 

 deeper parts at a depth of about 2 m. On the other hand it does not seem to be rare on the pearlbanks 

 in the Gulf of Mannar. No detailed information as to locality is present from other places. It is highly 

 probable, by reason of its appearance in Ceylon, that this species also belongs to those which prefer 

 somewhat deeper regions. On the other hand C crassifolia is, even if evidently bilateral and provided 

 with rather broad and flat main axes, so lobed that the danger of splitting is not really serious in this 

 species, even if it grows in exposed places in the upper littoral zone. What is true of C. crassifolia is true 

 also of C. iaxifolia (figs. 4, 5) and its different forms. It avoids exposed localities when it grows in the 

 upper littoral zone, where it is to be met with in pools. On the other hand, it is plentiful on the pearl 

 banks in deeper water. Collins only knows this alga from Jamaica as " washed ashore." The deep- 

 water form, f .asplenioides (fig. 4), has somewhat broader but shorter pinnules, directed straight outward, 

 the surface form smaller but longer, and sickle formed branches bent upwards. Remarkable is Harvey's 

 note on this species ('Phycologia australica,' III., PI. 178) : "There isfuUy as much difference among my 

 Friendly Island specimens, between those collected in the quiet waters of the lagoon and those from the 

 outer reef, as I find in those from opposite hemispheres." 



Haevey thus remarks in this species variations according to different situations, but without 

 characterizing the nature of the changes. 



An examination of the occurrence of the larger bilateral Caulerpa forms both in Ceylon and on 

 other coasts, where anything is known of them, consequently shows that in any case they have not their 

 main distribution in the Uttoral zone — even if isolated specimens occur there — but that this must be 

 located in deeper and quieter regions. 



(B). — The radial Caulerpas — The Analogy between the C. clavifera-uvifera type and the C. nummularia- 

 peltata type. 



Where do we find, on the other hand, the Caulerpas which have radial structm-e of their 

 assimilation system in the form of short-branches ? 



Of the Caulerpa species of Ceylon, besides the C. verticillata and Icetevirens which have already 

 been dealt with, we have in this group C. longistipitata , sedoides, clavifera, uvifera, peltata, nummularia 

 parvula, imbricata, and Chemnitzia. It should be observed at once that all these species occur in the 

 littoral region, and several of them belong to the commonest algse in the upper littoral region. Some 

 species with wide distribution are also to be met with deeper down, and these show very instructive and 

 interesting changes of form. More of this later on. A few species, as C. longistipitata and C. sedoides 

 have only been found in relatively very few places ; but as JoHS. Schmidt ("Flora of Koh Chang," IV., 

 p. 105) also mentions^them only from the littoral region, they seem most probably to be at home in this 

 region. 



Under what conditions do these forms live, and can we see any adaptations to their surroundings 

 in their organization ? 



Let us first examine C. clavifera (fig. 13). In the special part the characteristic mode of ^^rowth of 

 this species is dealt with. The form which is pictured in fig. 13 is a pronounced surface form, which at low 



water is often only laved by the waves. Its characteristic is its extended — almost flattened mode 



of growth, whicli depends on the vertical axes being so short and having only a small number of side 

 branchlets. When, at the same time, the root system and the horizontal axes are strongly developed, 

 the whole plant is firmly fixed to the rock, while the small short vertical axis offers few points of attack to 



the swell. It is to be noted that as a rule no Caulerpas at all — with the possible exception of Icetevirens 



are ever met with in the littoral region in really strongly exposed locaUties, but C. clavifera can sometimes 

 grow in places which, even if the sea there cannot be described as violent, are yet exposed to wear and tear 

 of a kind. In such places we often come across C. clavifera and others with similar construction, as 

 C. nummularia and others. It is rather remarkable that these Caulerpas are so often to be found among 

 small living corals and small colony-forming Actinians. The horizontal axes creep amongst the Actinians 

 49-06 



