F. Børgesen: Rhodophyceæ of the Danish W. Indies. 271 



fig. 246 E. The distance between tlie branches is great; as pointed 

 out by Falkenberg these are most often found upon every fifth 

 to eighth joint. 



The tetrasporangia (Fig. 266) are found in the upper part of 

 the branches in shorter or longer rows. The tetrasporangia are 

 proportionately small, and the branches in which they are im- 

 bedded are not much swollen. The cystocarps are broadly ovate 

 or nearly spherical and have short stalks. 



The antheridia I have not found; these are beautifully figured 

 by Thuret in Recherches sur les anthéridies des cryptogames 

 (Ann. sc. nat., Bot., 3. sér., vol. 10, pi. 6) and in Etudes Phyco- 

 logiques, 1. c. 



This species is a characteristic lagoon-plant living in the often 

 very dirty water found here. Together with other algæ it often 

 forms a dense coating upon the roots of the mangroves, and like 

 these its tufts are more or less covered with mud. In clear water 

 it does not seem to occur. Harvey, in Phycologia Britannica, pi, 

 155, has already mentioned this peculiarity, as to its occurrence 

 and this has later on been pointed out by Falkenberg, Rhodo- 

 melaceen, p. 119. 



Plants with tetrasporangia and cystocarps have been found 

 in January. 



St. Thomas: Bovoni Lagoon. St. Croix: The Lagoon of Christiansted, 

 Salt River Lagoon. 



Geogr. Distrib.: The Atlantic coast of North America, the West 

 coast of Europe, Mediterranean Sea. 



4. Polysiphonia sphærocarpa nov. spec. 



Frons dense cæspitosa, cæspitibus parvis, circiter 1 — IVg 

 cm altis. 



Fila non corticata siphonibus pericentralibus quatuor. 



E filis repentibus decumbentibusque, rhizoideis substrato ad- 

 fixis, fila erecta gignuntur. Fila in parte basali circiter 100 ^ 

 crassa; cellulis ca. 150// longis. 



Ramificatio subdichotoma; ramis erectis extra axillis tricho- 

 blastorum ortis, angulis acutis. 



Tetrasporangia in superiori parte filorum, sæpe furcata, posita, 

 seriata. Lat. tetrasporangiorum = 60 /^. 



Cystocarpia fere sphærica, ca. 80^^ longa et lata. 



