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



285 



Fig. 285. Bn/othamnion Seaforthii 



(Turn.) Kütz. Part of the thallus. 



(.About 4:1). 



fellosen generischen Zusammen - 

 hörigkeit mit B. trianguläre ange- 

 nommen werden muss, dass die 

 schwach entwickelten Blätter von 

 B. trianguläre hier grösstentheils 

 ganz abortirt sind. Häufig abortiren 

 übrigens selbst die Blätter an den 

 erlöschenden Spross-Spitzen mehr 

 oder weniger." This has not been 

 altogether confirmed by the ex- 

 amination of my material. 



The figure 284 shows the 

 growing summit removed from the 

 surrounding protecting branchlets. 

 From this it is evident that the 

 growth of Bryothamnion Seaforthii 

 takes place in a very similar way to that of Bryothamnion tri- 

 guetrum. As in this species, trichoblasts issue from every second 

 segment; the trichoblasts are once forked, each of the filaments 

 consisting of 4 cells, and are upon the whole much like those 

 found in Br. triquetrum ; the only difference seems to be that the 

 cells are much shorter. On the other hand their diameter is 

 somewhat longer, about 20 /y.; sometimes one of the filaments 

 bears a short sidebranch. But while in Bryothamnion triquetrum, 

 the trichoblasts are placed in a screw line round the summit with 

 a divergency of 120, in the present species they are placed di- 

 stichously with a divergency of 180 ^. From the basal cells of 

 each of the trichoblasts an axillary branch issues. These branches 

 grow quickly and are bent inwards over the young summit. I can 



not say how far the 

 trichoblasts are placed 

 exactly with a diver- 

 gency of 180'^ or some 

 smaller variations are to 

 be found; in every case 

 some small oscillations 

 seem to be present as 

 the branches alternately 

 place their summits over 

 or under the following 



Fig. 286. Bryothamnion Seaforthii (Turn.) Kütz. 

 'Transverse section of the thallus. (About 30 : 1). 



branch. 



