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



227 



The basal cells in the branchlets are small, nearly quadratic 

 (comp. Figs. 213 and 214), while the other cells in the rachis are 

 nearly cylindrical, a little thicker upwards where the pinnæ 

 issue. The basal cell is very persistent, more or less immersed 

 in the mother cell and remains after the branchlets have died; as 

 pointed out by Howe^) for A. densiim so in the present species 

 also, rhizoids grow out from this cell ; adventitious, erect fila- 

 ments too arise from it. 



The cells in the rachis of the branchlets are from 20 — 24 fi 

 broad and 50 — 150// long or more. The pinnæ are simple 

 or ramified and generally provided 

 with a single pinnule growing out 

 mostly from the secund cell from 

 the base on the distal side of the 

 pinnæ (Fig. 215). These pinnules 

 (Fig. 216 b, c, d) consist generally of 

 two to four, seldom more, cells about 

 1^/2 times as long as broad (long, 

 cell. = 10 f/, lat. 13 /i). Nearly every- 

 one of these small pinnules carry 

 a large, oval, clear gland-cell on 

 their upper (inner) side. This is 20/^ 

 long and 13/^ broad. 



As to the development and 

 position of the glands the present 

 plant seems to come near to A. cru- 

 ciatum according to the description 

 by Nestler"), still a few small differ- 

 ences occur. While in the latter 

 plant the gland-cell is in contact with 

 3 — 4 cells, in my plant, as a rule, it 

 abuts on to two cells, or more seldom three cells (Fig. 216 

 h, c, d). Nor have I ever in my plant seen the "stab-oder leisten- 

 förmigen Bildungen" which Nestler found in A. cruciatiim; but, 

 of course, it must be remembered that I have not been able to 

 examine living material. As to the development of the gland- 

 cells I have once come across (in the very scarce material at hand) 



Fig. 214. Antithamnion antilla- 



num nov. spec. Part of a plant. 



(About 85 : 1). 



^) Howe, M, A., The marine Algæ of Peru. (Memoirs of the Torrey Bot. 

 Club, vol. XV, 1914, p. 151). 



-) Nestler, a., Die Blasenzellen von Antithamnion Plumula (Ellis) Thur. 

 und Antithamnion cruciatum (Ag.) Näg. (Wissensch. Meeresunter- 

 suchungen, III. Bd., 1, 1899). 



15* 



