THE CEYLON SPECIES OF (^AULERPA. 



127 



especially in its mode of growth. The vertical axes are very short and closely set. The often flattened 

 branchlets are rather rigid, and turned either up or down, and mostly directed so that as much of the sur- 

 face as possible is exposed (fig. 22). This is often produced by a torsion of the branch, so that the flat 

 side gets turned upwards. Moreover, the branches sometimes become somewhat enlarged at the point : 

 in any case the result is that a close compact tuft-formation is produced with , at the same time, the ex- 

 posure of as much of the assimilation-surface as possible. To the rigidity of the tuft-formation contributes , 

 too, the fact that the branchlets are very rigid and not, as in the other forms, easily waved to and fro. 

 This form, so biologically different, was found by me on stones together with several other tuft-forming 

 seaweeds in somewhat deeper water, so that they were not laid bare at low- water and not so strongly 

 exposed to the swell as /. laxa. 



Finally, it seems to me to be by no means unimportant to point out that the laxa forms in Ceylon 

 showed themselves very constant and well defined from other Caulerpa forms. In every case transition 

 forms to the clavifera and the uvifera series were entirely absent. 



OeographicaZ ditribution. — Ceylon : Galle (/. laxa and /. depauperata in exposed places ; /. caes- 

 pitosa in somewhat deeper water or not so exposed places) ! Weligama ! Indian Ocean (Western 

 Australia) ; Atlantic (West Indies). 



Fig. 23. — C. dichotoma n. fip. (1 x 1). 



13 —CAULERPA DICHOTOMA, n sp. 



The horizontal axis enlarged, creeping, with the upward flattened vertical axis up to 4 cm. in 

 height with generaUy opposite, always flattened branchlets with generally furcate dicho- 

 tomous points (figs. 23, 24). 



C. dichotoma comes near to C. Icetevirens and C. Lamourouxii, but differs from both in having the 

 greater part of its branchlets dichotomous. 



I found this Caulerpa at WeUgama at a depth of from 1 to 2 m. on sandy bottom. 



What justifies its creation as a special elementary species is its characteristic quahty of the 

 branchlets being dichotomous (fig. 23). A typicaUy developed axis with such branchlets is to be seen in fig. 



