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seagrass formation. I visited the locality several times during my 

 last stay on the islands, and on one occasion the water was so 

 low that a part of the formation was laid dry, as shown in fig. 1. 



The picture is looking towards the west, so that Krausse's 

 lagoon is behind the observer. The bottom consists of soft mud 

 mixed with sand, and is covered with a dense vegetation. As far 

 as I could see, and judging from the specimens which a negro 

 waded out and fetched for me, the vegetation essentially consisted 

 of Thalassia testudimim Sol., further some Cymodocea manatorum 

 Aschers. and Halodide Wrightii Aschers. were found. Great quan- 

 tities of algse were growing among these Phanerogams. As the 

 most common must be mentioned Udotea flabellata Lamour., and 

 especially several Halimeda-species such as forms of Halimeda in- 

 crassata Lamour. and H. Tmia Lamour., which at several places 

 covered the bottom quite densely, and lastly great numbers of 

 Penicillus capitatus Lam. And between these and the sea-phane- 

 rogams numerous Gaulerpas were found creeping, especially forms 

 of the species Caulerpa sertularioides (Gmel.) Howe, C. cupressoides 

 (Vahl) Ag., C. crassifolia (Ag.) J. Ag. var. mexicana, and C. prolifera 

 (Forsk.) Lamour. Here and there some young, newly rooted, 

 Bhizophora-seedVmgs appeared above the mud ; and in the middle 

 of the picture is seen a larger jRhizophora-p\sini, showing that the 

 mangrove vegetation of Krausse's lagoon spreading further west will 

 be likely to take possession of this ground soon. 



Halophila-species I did not see here, probably because the 

 locality is a little too exposed, as the sea can at some times be 

 rather turbulent with southern and western winds. Halophila, on 

 the contrary, are commonly found in bays and lagoons with fresh salt 

 water, e. g. in Ghristianssted's lagoon on the north side of St. Groix. 

 Here they often grow in shallow water extensively covering the 

 soft and muddy bottom with their delicate pale-green leaves. The 

 thin thread-fine rhizome creeps on the bottom, though often covered 

 by a thin layer of sand or mud. 



In Ghristianssted's lagoon Cymodocea manatorum Aschers. also 

 grows in great numbers. Its rhizome is altogether buried in the 

 mud, so that it is often only the uppermost part of the cylindric 

 leaves which appears above the mud. Thalassia testudinum Sol. 

 is likewise found here although more rarely. Between the sea- 

 grasses several species of Gaulerpas are commonly found, especially 

 C. cupressoides (Vahl) Ag., C. crassifolia (Ag.) J. Ag. f. mexicana, 



