— 54 — 



the first mentioned often forms pure large societies in quite shallow 

 water (1 — 2 feet). With its almost awlshaped point the smooth 

 „rhizoma" bores itself easily through the mud and only at some 

 distance from the point with short intervals assimilating green 

 shoots appear in an upward direction, fine ramified roots in a 

 downward one (fig. °2). As I have pointed out elsewhere x ) this plant 

 in a striking manner puts you in mind of Carex arenaria, its shoots 

 frequently straight as a line and of the lenght of a yard or even 

 more growing as those of the former through the mud now and 

 then at short intervals bearing the green more or less ramified 

 shoots half a foot long or more. I have also found Caulerpa plu- 

 maris in muddy localities in shallow water forming a rather 

 extensive unmixed vegetation. But most frequently the different 

 species are mixed together. Caulerpa racemosa var. laetevirens? 

 I have only found in the lagoon of Ghristianssted , it was here 

 growing in abundance at a depth of about two fathoms in loose 

 bottom together with C. cupressoides. Caulerpa proliféra I have 

 only seen at Sandy Point, the sandy south westernmost point of 

 St. Croix; it was growing here in quite shallow water partly on 

 sand partly on rocks and thus forms a transition to the lithophile 

 Caulerpa. 



The Algae fixed to the same spot (fig. 3), as mentioned above, are 

 represented by the genera Pe?iicillus with the species capitata, Udotea 

 with the species flabellata and Halimeda with the species tridens 

 and probably some few other species; perhaps also Aurainvillea 

 longicauliß which in a hurry resembles an JJdotea and Chamœdoris 

 annulata belong to this group, but as I have not seen them esta- 

 blished, I cannot state anything about this for certain. They are 

 all characterized by having the lowest part of the thallus fixed 

 in the mud and thickened by a covering of numerous hyphalike 

 threads, which fasten themselves to the grains of sand and thereby 

 fix the plant. Penicillus capitatus is the most common and often 

 forms extensive pure Penicillus societies covering the bottom as a 

 thick low forest frequently dense enough to make it impossible to 

 see the bottom ; it is to be found as well on a sandy as on a 



] ) F. Børgesen og Ove Paulsen: Om Vegetationen paa de dansk-vestindiske 

 Øer. Det nordiske Forlag. Kjøbenhavn 1898 (and Botan. Tidsskrift 22) 

 pag. 3 the note, where it is called C. juniper vides; but this species it accor- 

 ding to Madame Weber van Bosse only to be considered as a form of 

 C. cupressoides. 



