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



29 



Discus basalis bene evolutus, unistratosus, e filis repentibus 

 ramosis, cellulis fere isodiametricis, compositus. Fila erecta nume- 

 rosa, parce ramosa, ad apicem versus attenuata et in pseudopila 

 producta; in basi et media parte 5—6//, in superiori parte 2—3// 

 crassa, cellulis inferioribus c. 14^«, mediis c. 30/<, superioribus 

 10 fj. vel plus longis. Chromatophorum parietale, pyrenoide laterali 

 instructum. 



Ramuli sporangiferi numerosi, sparsi aut sæpe oppositi, 1 — 3, 

 rarius plures, cellulas continentes. Sporangia ovata, 7—8// lata 

 et 8—10// longa. 



This species was found upon Chætomorpha antennina upon 

 which it forms small dense nearly globular or semiglobular tufts. 



The basal part (Fig. 21) of the plant consists 

 of creeping ramified fdaments, more or less fusing 

 together and forming in this way a large disc. 

 The cells in the disc are rather irregularly shaped, 

 about as long as broad or a little longer i. e. 

 from 5 to 11 /< broad. 



From this basal part numerous erect fda- 

 ments grow up ; those in the middle are nearly 

 straight, those in the periphery are bent out- 

 wards in view of space and light. At the base 

 the erect filaments are about 5 — 6// broad and 

 the length of the cells about 14/«. Upwards the 

 length of the cells increases gradually reaching 

 in the middle of the filaments about 30/«. From 

 here the cells not only grow longer but the 

 filaments also taper towards their summits in 

 such a way that the uppermost cells only reach 

 a breadth of 2—3/« while the length of the cells 

 on the other hand is often more than 70/« 

 (Fig. 21). These thin unbranched prolongations 

 of the filaments are nearly or quite colourless and hairlike. While 

 the lowermost cells in the filaments taper a little at both ends 

 those higher up in the filaments are cyhndrical. The cells con- 

 tain a slightly developed parietal chromatophore lying near the 

 upper end of the cell and a lateral pyrenoid (Fig. 22). 



The erect filaments are multilaterally ramified but not much. 

 These branches contrast distinctly with the numerous short 

 sporangiferous branchlets. Along the whole length of the fila- 

 ments from their base and up to the beginning of the hair-like 

 prolongations nearly all the cells bear either a single or more 



Fig. 22. Acrochæ- 

 tium globosum 

 nov. spec. Part 

 of a filament with 

 branchlets bear- 

 ing sporangia 

 (some ones emp- 

 tied), (about 

 600:1). 



