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at times washed over with salt or brackish water". If this defini- 

 tion had to be applied to the Danish West Indies, not only Lagun- 

 cularia- and ^^J^ceww^a-growths, but even those o^ Rhizophora have 

 often to be excluded from the mangrove formation, as all 3 species 

 as explained above, are found rather often where the bottom is 

 quite laid dry. As the tide is of no practical significance in the 

 Danish West Indies, the ground of the mangrove formation, what 

 the English call "tidal forests", is considerably diminished. More 

 often the three above mentioned species are growing in shallow water, 

 and then Rhizophora outermost in deepest water to which it is 

 particularly well adapted through its root-system, inside it Avicennia, 

 of which the pneumatophores are comparatively long, often more 

 than V2 metre, then Laguncularia with shorter pneumatophores 

 growing innermost on the almost, or quite, dry soil. This is 

 the rule, to which of course there are many exceptions. As the 

 ground is rising gradually below the mangrove formation, partly 

 from deposits from the sea, partly from material brought from land 

 and sometimes assuredly also by upheaval of the earth-crust, and 

 is at last laid dry, it is therefore far from always the case that 

 the Rhizophoras are excluded to give place to Avicennia and 

 Laguncularia. The most luxuriantly developed Rhizophora-forest 

 which, as far as I have seen, is to be found at present in the is- 

 lands, namely the one growing at the head of "Great Gruzbay" on 

 St. Jan, and of which the accompagning plate III shows a little 

 part, is thus growing on quite dry firm soil, only quite near the 

 sea was still found a little lagoon filled with water, which as well 

 as the whole Rhizophora ground was shut off from the sea by a 

 rather high sand-bank. Possibly the waves with very high sea 

 can wash over this sand-bank, but certainly a long time can pass 

 without this being the case. 



We may therefore in the Danish West Indies define the man- 

 grove as a formation of tree-like evergreen plants 

 growing on the sheltered shores, partly in shallow, salt 

 or brackish water, partly on low-lying soil which is 

 comparatively rarely, sometimes perhaps never co- 

 vered by salt or brackish water. 



That the mangrove formation may be found on quite dry 

 soil makes it more difficult to distinguish between the mangrove 

 vegetation and the transitional vegetation, which Sc him per in 

 Asia has called the iVi^^a-formation, and to which, with respect 



