274 



Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 



found in company with P. jern- 

 lacea. 



Only found once: 

 Store Nordsidebugt. 



St. Thomas : 



Fig.271. Polysiphoniasphærocarpa 



nov. spec. A nearly ripe cysto- 



carp. (About 200:1). 



5. Polysiphonia macrocarpa Harv. 



Harvey, W. H., in Mackay, Flora 

 Hibernica, part 3, Algæ, p. 206. Bornet, 

 E., Les Algues de P. K. A. Schousboe, 

 p. 306, pi. Ill, fig. 5. 



Polysiphonia pulvinata Harv., Phy- 

 cologia Britannica, pl.^ 102 B. Kützing, 

 Tabulæ Phycologicæ, vol. 13, pi. 36a— e? 



This plant is common on the 

 roots of the mangrove, and forms 

 dense, dark red-brown tufts, up to 

 10 cm or higher. The thallus has 

 four pericentral cells. There is no 

 cortical layer. The base (Fig. 272) of the plant consists of 

 decumbent, creeping, more or less ramified filaments, from the 

 lower surface of which rhizoids issue, fastening the filaments to 

 the substratum. The rhizoids grow out from the pericentral cells 

 and are in permanent 

 open connection with 

 the mother-cell, having 

 no walls, either at their 

 point of origin or else- 

 where. They have a 

 longer or shorter cylin- 

 drical stem with very 

 thick peripheral walls, 

 leaving only a very 

 narrow channel open 

 .in the middle, and end 

 in irregular lobes, of- 

 ten forming a small 

 disc. The rhizoids are 

 of variable length, 

 shorter or longer in 



nrODOrtion to the di- ^^^" "^^' Pf^ly^^P^^onia macrocarpa Harv. Base 

 •^ ^ of a filament with rhizoids and erect branches, 



stance from the sub- (About 20:1). 



