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



377 



few branches of quite the same shape as their own; sometimes 

 it may happen that such a branch is given off from the blunt 

 apex of the mother branch. 



The plant has a fine, clear-rose colour; it is somewhat dia- 

 phanous, of a fleshy succulent 

 consistency. When dry it collapses 

 completely, and it adheres mostly 

 very well to the paper. A trans- 

 verse section (Fig. 365 c) shows 

 that the greater part of the 

 tissue consists of large, transpa- 

 rent and thin-walled cells; out- 

 wards these become smaller and 

 they are surrounded by a corti- 

 cal layer consisting of one or two 

 layers of rather small, thick-wal- 

 led cells. Seen from the surface 

 the cortical cells are irregularly 

 polygonal (Fig. 365 B). 



In the tetrasporic plant the 

 tetrasporangia occur scattered 

 or in small irregular groups in 



the cortical layer (Figs. 365 B, C). The tetrasporangia are round- 

 ish of shape, their diameter reaching a length of about 40 fi. 



The female plant bears the warty, dark-red cystocarps scat- 

 tered over the surface. 



The plant does not seem to approach any known Gracilaria. 

 From Gracilaria Blodgetti it differs especially by the scarcer rami- 

 fication and the obtuse apices of the branches. 



The plant was found with tetraspores and cystocarps in the 

 month of March. It was dredged in deep water about 10 — 15 

 fathoms. 



The Callithamnion cordatum is a common and characteri- 

 stic epiphyte upon this Gracilaria. 



St. Jan.: Found in many places in the sound between this island and 

 St. Thomas; and in the sea to the north of America Hill. 



Fig. 365. Gracilaria cylindrica 

 nov. spec. 

 A, transverse section of the thal- 

 lus (about 8:1); B, surface of the 

 thallus with tetraspores; C, trans- 

 verse section of epidermal layer 

 with tetraspores. 

 {B and C about 80:1). 



