— 55 — 



muddy bottom. On the muddy bottom in lagoons where the water 

 as a rule is not clear, it is of a lighter colour and less rigid, while 

 in limpid water it has a dark green hue and is more compact. 

 Udotea flab ell at a , Halimeda tridens and closely related species 

 often grow more scattered now in pure societies now again together 

 with Penicillus and Caulerpae. Whilst the more flaccid Gaulerpae 

 seldom bear epiphytes, the former Algae, being more rigid from 

 being incrustated with lime, often carry, a rather rich epiphytic 

 vegetation, among which may be especially mentioned crustformed 

 Algae (f. i. Melobesia) and large clumps of different Algae f. i. 

 Dictyota species, Flypnea musciformis, Siphonocladus etc. 



In the tranquil water of the lagoons finally we meet with the 

 formation of the unattached Algae. The only Alga which appears 

 here forming a society is Halimeda Opuntia. At the depth of a 

 few r fathoms it covers the bottom and may with the dredge be 

 brought up in large connected compact cakes, its rather stiff but 

 fragile branches are quite entangled into each other. Wherever it 

 is found, it appears to be absolute monarch and does not leave 

 room for any other Algae nor do any epiphytes as a rule seem 

 to fasten themselves upon it. Where I have found this species more 

 abundant (f. i. in the large lagoon on the eastend of St. Thomas) 

 it grows in turbid water. 



The lagoons however do not shelter only these Algae growing 

 in the soft, mud of their bottoms; a vegetation much richer in 

 species and quite as interesting is found on the numerous roots of 

 the mangroves. If we take up such a root from the water, we 

 shall tind it covered with a dense layer half a foot long of the 

 most different Algae. For not only do we here find Ghlorophyceæ; 

 but several Rhodophyceæ also find shelter under the shady vegeta- 

 tion of the mangroves. The Algae growing in these protected 

 places are nearly all of a fine structure and daintily and elegantly 

 formed. 



Thus the little dainty Caulerpa verticillata l ) (fig. 4) has its proper 



*) About this species Reinke in his interesting work: „Ueber Caulerpa" pag. 7 

 (Wissensch. Meeresuntersuch. N.F. V. Bd. H. 1. Kiel 1900) writes: Bildet dichte 

 Rasen, die bei allen von mir gesehenen Exemplaren nur aus den gabelig 

 verzweigten, aufstrebenden Assimilatoren bestehen, während in der Literatur 

 auch kriechenden Rhizome angegeben werden. Ich meinerseits sah farblose 

 Wurzeln aus dem untersten Theile solcher Assimilatoren entspringen. Ver- 

 mutlich werden Pflanzen, die den Raum fanden, sich vollständig zu ent- 



