356 



20 



becomes muddy when one touchs the plant. The mangrove algæ and with them 

 Caiilerpa verticillata contribute therefore, probably not inconsiderably, to the gain 

 of land which is to be found where Rhizophora grows. 



By reason of the exceedingly dense mode of growth, arising from the fact 

 that the creeping rhizomes on the mangrove roots are woven together and form 

 often a thick? layer composed of the intertwined rhizomes, mud etc., and from the 

 fact that the older rhizomes die away by degrees, there will gradually arise a great 

 many separate plants the bases of which often consist of fragments of rhizomes 

 only, so that it is often rather difficult to see that the plant really has a creeping 

 rhizome. This has been, I think, the reason why Reinke, who most probably 

 had only such small dense clumps for examination, questions whether the plant 

 really has a creeping rhizome (27, p. 7). In my paper above cited I have pointed 

 out as already mentioned in the general part that this apprehension is not right 



and I have there given the figure which 

 I again reproduce here (Fig. 1). Svedelius 

 (30, p. 109) without knowing my paper has 

 emphasised the same point and has given 

 a similar figure. Caulerpa verticillata grows 

 in Danish West India in sheltered places 

 only and it shows also in this fact a dif- 

 ference in comparison with its occurrence 

 in Ceylon where as mentioned by Svedelius 

 it is to be found on rather exposed coasts ; 

 on p. 93 Svedelius (30) mentions it together 

 with C. lœteuirens i.laxa and C. sertularioides, 

 the species of Caulerpa which in Ceylon 

 grow on the most exposed localities. 



In the adjoining illustration, fig. 3 a 

 shows the uppermost part of an erect grow- 

 ing shoot (assimilator, Reinke) with two whorls of leaves of which the uppermost 

 is yet quite young consisting only of roundish swellings; the lowermost are already 

 dichotomously divided. Fig. 3 b shows a somewhat older more developed leaf. 

 In the fully developed leaf the outermost apices are 2 — 4 divided (fig. 3 c). Finally, 

 fig. 3 d shows the ends of a pair of rhizomes. 



Ørsted was the first who found the species in St. Croix and his specimens 

 have at any rate partly served J. Agardh as material for his description of the 

 species. It is very common on the shores of the Danish West Indies in sheltered 

 localities in lagoons with mangroves; f. charoides I have only found in Krause's 

 lagoon on the south coast of St. Croix, where it grows abundantly on the roots of 

 the Rhizophora on the outside of the mangrove forest in the south-west corner of 

 the lagoon. It grows here together with the forma typica but is recognizable by 

 the colour which is of much lighter green. 



Fig. 2. Caulerpa vcrlicillata i. Ag. f. charoides 

 (Harv.) Weber van Bosse. From the lagoon 

 of Krause (St. Croi.K). (About 1 : 1.) 



