F. Borgesen: Phæophyceæ of the Danish W. Indies. 53 



"Phycologia Barbadensis" have been of much help to me, the 

 more so since I think Dr. Bornet assisted her a good deal in 

 their preparation. 



While some of the species found seem to be fairly well 

 defined, others are much more variable and therefore often diffi- 

 cult to recognize. As is the case with many other algæ so also 

 here the external conditions of life seem greatly to alter the 

 appearance of the thallus. It seems therefore most probable 

 that an examination of a large collection from different localities 

 and in different stages of development will prove that some of 

 the plants now considered as distinct species are really only forms. 



1. Dictyota Bartayresiana Lamx. 

 Lamouroux, Exposition des caractéres du genre Dictyota (Journ. de 

 Botanique, t. II, 1809, p. 43). J. Agardh, Species Algarum, vol. I, p. 94. 

 J. Agardh, Till Algernes Systematik, V, p. 97. J. Agardh, Analecta algol., 

 cont. I, p. 66. Harvey, Nereis Bor.-Am., p. 110, pi. VIII C. A. Vickers, 

 Phycol. Barbad., pi. XII and XIII. 



The specimens referred to this species are rather variable ; 

 on the whole they agree well with the figures of M lle Vickers. 

 Some of the specimens also show some likeness with Dictyota 

 wlubilis and especially with Diet, partialis. The ends of the 

 branches are sometimes acute, sometimes more rounded; M me WEBER- 

 van Bosse 1 ) also mentions a form with rounded summits. 



Only tetrasporangia-bearing specimens were found. The tetra- 

 sporangia occur upon both sides of the frond. They are either 

 solitary or placed a few together and scattered over the whole 

 surface. 



This species mostly occurs in shallow water in sheltered places. 

 Often it is lying loose, covering the sandy bottom behind the 

 coral reefs. 



Once I dredged it at a depth of about 20 meters. 



With the exception of the more exposed coasts it is a common species 

 on the shores of the Danish Islands. 



Geogr. Distrib. West Indies, Indian Ocean, tropical Australia. 



2. Dictyota linearis (Ag.) Grev. 



Greville, Algæ Britannicæ, p. XLIII. J. Agardh, Species Algarum, 

 I, p. 90. J. Agardh, Till Algernes Systematik, V, p. 101. J. Agardh, 

 Analecta algol., cont. I, p. 77. Kützing, Tab. Phycolog., vol. IX, tab. 21, fig. II. 



J ) Weber-van Bosse, Liste des algues du Siboga, p. 182. 



