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



45 



Cellulæ cylindricæ in inferiori parte filorum ca. 11// latæ 

 40// longæ, in superiori 7—8// latæ 40 /j. longæ, chromatophorum 

 parietale, pyrenoide laterali, instructum continentes. 



Sporangia sessilia, raro pedicellata in parte 

 basali ramorum uniseriata, monospora aut raro 

 hispora, ovalia, ca. 18 — 20/i longa et 9 — 12« lata. 



The basal part of this species is immersed 

 in the mucilage and chalk incrustation of the 

 host plant [Liagora elongata). 



On germination the spore does not divide 

 and remains throughout undivided ; its diameter 

 is about 16//. After the germination it produces 

 endophytic fdaments from its lower side ; these 

 creep downwards fixing themselves to the assi- 

 milating filaments of the host plant (Fig. 42 c). 



From the upper end an erect filam.ent (or 

 sometimes two) is given off (Fig. 42 a) ; this is 

 at first undivided but after having grown so 

 that it is quite free of the Liagora tissue it 

 becomes branched. The ramification is some- 

 what slight. The branches are given off at an 

 acute angle and the branches themselves are 

 ramified in the same way giving the plant a 

 cluster-like appearance. 



Towards the summit the branches taper 

 into hair-like filaments the cells of which are 

 long and nearly colourless and soon die away 

 at the end (Fig. 42 a). 



The cells in the filaments are about 10 — 11 /i 

 thick and about 27 — 40// long; near the base 

 the filaments are a little thinner, about 8 // ; 

 in the hairlike ends the cells taper to about 

 7—8,«. 



The chromatophore (Fig. 43) is parietal, 

 often with elongations towards the wall of the 

 cell and it encloses a lateral pyrenoid. 



The sporangia (Figs. 42 «, b, Fig. 43) are 

 sessile, oval-ovate. They are about 9 — 12 ß 

 broad and 18 — 20 a long. Monosporangia 

 mostly occur, but in a few specimens some 

 were divided by a transverse wall into two spores (Fig. 43). 



It is perhaps not impossible that Acrochæiium Barbadense 



Fig. 42. Acrochæ- 



tium occidentale 

 nov. spec, a, erect 

 filament with spor- 

 angia, b, part of a 

 filament with spor- 

 angia, the upper- 

 most divided into 

 two spores, the 

 lowermost emp- 

 tied, c, base of a 

 plant fixed to the 

 assimilating fila- 

 ments of Liagora. 

 {a, about 125 : 1; 

 b, 250:l;c, 200:1). 



