THE CEYLON SPECIES OF CAULRRPAS. 86 



Reinke has figured devcrai, as, i'oi' instance, C. flay elli for mis (Reinke, loc. cil., Hg. lOj, prolifera 

 (fig. 11), Freycinetii (fig. 38), paspaloides (fig. 52), and others. The characteristic of these species is that 

 the rhizome is rather coarse, sparsely branched, grows more or less deep in the sand, out of which only 

 the assimilation branches stick up in long rows, with small or great intervals between them. Of C. 

 Freycinetii we consequently only see as it were ball-shaped bundles of assimilation branches entangled 

 together. In Ceylon this type of Caulerpa is only met witli in the north, around Adam's Bridge and the 

 islands about Jaffna, where the shore is always sandy. On the coral reefs and rocky sliores of the south- 

 west, this type is scarcely to be met with. To judge from certain indications, this Caulerpa type 

 consists chiefly of still-water forms, which therefore often prefer somewhat deeply situated habitats. 

 Thus C. Lessonii has only been observed on the pearl banks at a depth of several metres. C. Fergu- 

 sonii, too, does not belong to the upper littoi'al zone, either. C. Freycinetii has been collected by me in 

 the upper littoral zone, it is true, but since it only appears there occasionally we are tempted to assume 

 that its main distribution lies deeper down. That this is not a mere chance guess, and that it has some 

 justification is supported by the fact that JoH.s. Schmidt collected C. Freycinetii in the Gulf of Siam 

 at no depth less than 2 metres, and as for C. cupressoides we are told that it occurs in such localities as 

 lagoons (BoRGESEN), which points to its being a still-water form. 



Besides being distinguished by its mode of growth — i.e., half hidden in the sand — this type is dis- 

 tinguished also by its root branchlets being very long and especially very closely and finely branched, 

 and between the fine root branches the particles of sand are pressed so tight that large lumps accompany 

 the plant when it is pulled up from the bottom. Reinke has described this type and given several 

 illustrations of it in his paper {loc. cit. figs. 20, 38, 42, 52, 73). As ecological adaptations to the con- 

 ditions of the life of these plants in the sand, we may consider their long-creeping rhizome axis and 

 especially the development of their root system. Such repeated branching in a great number of fine fila- 

 ments which fasten themselves firmly to the grains of sand may be taken as an excellent anchoring 

 apparatus for a plant living on a sandy bottom. In this type there is no organization of the shoots to 

 neutralize the danger of being oversanded — a danger which is not to be feared in sucli j^laces as those 

 where this plant is to be found. Approximating to this type are such species as C. crassifolia, C. dicho- 

 toma (fig. 23), C. uvifera (fig. 15), and others, which if not invariably, at least most generally, have a mode 

 of growth analogous with that of the sand Caulerpas just described. 

 (C.) Rock and Coral Caulerpas. 



The most numerous Caulerpas belong to a group which grows preferably on stones, corals, and 

 in general, fixed substrata. But here tlie conditions may be of most dissimilar nature, owing to the 

 different degrees of exposure to the swell, to the other local conditions affecting vegetation, to the presence 

 of Actinians and living corals, and so forth. 

 (a) C. Icetevirens type. 



Among these rock Caulerpas, C. Icetevirens f. laxa (fig. 19) takes a unique position inasmuch as 

 this species grows by preference in exposed localities, where it constitutes the sole vegetation (forming a 

 special C. Icetevirens association), and covers large areas, as at Galle, on the boulders north of Victoria Park. 



C. Icetevirens f. laxa there forms a typical algal association of a kind that has been described from 

 northern seas, and that has been called" boljslagsformationer" by Gran ('■ wave-beat formations" is the 

 Hteral rendering) , in " Kristianiaf jordens algflora, ' ' p. 9. Such formations or associations are, for instance, 

 the Nemalion formation of the west coast of Sweden (K.jellw an , '' Algenreg.und Algenformationen," p. 11 ) , 

 the Bangia-Urospora association of the Faeroese coasts (Borgesen, " The Algae- Vegetation of the 

 Faeroese coasts," p. 719) and the Gobia-Dictyosiphoniormaktion from the Baltic (Svedelius, " Ostersjons 

 Hafsalgflora," p. 29). What characterises all these formations* is that they are very exposed to the swell 

 and hence are in continual movement, waving to and fro, covered one moment, free the next, in never- 

 ceasing alternation. 



* Tliis use of the term " formation " is analogous with the sense in which it is employed in Geology Ed. 



