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



261 



Fig. 255. Acanthophora spicifera (Vahi) Børgs. 

 Summit of a filament showing the axillary 

 branches issuing from the basal cell of the 

 trichoblasts. The tissue in the middle has been 

 somewhat spoilt during the preparation. 

 (About 270:1). 



further seen from the 

 figure that the summit 

 of the plant is protru- 

 ding in the form of a py- 

 ramid and not "bisweilen 

 einer kleinen Scheitel- 

 grube eingesenkt" as 

 mentioned in Engler 

 und Prantl, Natürl. 

 Pflanzenfam., I Teil, 

 Abt. 2, p. 435-6. When 

 in full growth the sum- 

 mit of the plant is quite 

 enveloped and protected 

 by trichoblasts. As the figure shows, the plant has a large apical 

 cell, somewhat longer than broad, from the base of which flat 

 segments are cut ofT. Each of these segments bears a trichoblast, 

 the basal cells of which are developed before the segments are 

 divided. 



A transverse section (Fig. 256) of the stem shows the central 

 cell and the five pericentral ones surrounded by a thick paren- 

 chymatic layer of cells, larger and with thin walls inside, small 

 and thickwalled at the periphery. 



Plants have been found with tetraspores, antheridia and cy- 

 stocarps. 



The tetraspores are developed in stichidial ramuli provided 

 with spines (Figs. 254, 257 C), in contrast to the spineless, ovate 

 roundish stichidia of Acanthophora Delilei Lamx., as mentioned 



and described by Falkenberg, 1. c, 

 p. 229, tab. 22, fig. 3. But it is sel- 

 dom that I have found stichidia in 

 form like those of' Acanthophora 

 Delilei, in which case there was only 

 a single bare one in the upper end 

 of the filament, the other stichidial 

 branchlets all having spines (comp. 

 flg. 257 C). 



The stichidial branchlets of the 

 present species are very similar to 

 those of Acanthophora orientalis J. Ag. 

 as figured by Okamura in "Icones 



Fig. 256. Acanthophora spicifera 



(Vahl) Borgs. Transverse 



section of the thallus. 



(About 50:1). 



