PLATE IV. 



Figs. 39 — 51. Halimeda iucrassata. 



Fig. 39. Forma typica. (West-Indies). Nat. size. 



Fig. 40. Forma monilis. Nat. size. 



Fig. 41. Forma Lamourouxii. (Siboga-Exp.). Nat. size. 



Fig. 42. Forma ovata. (Pacific Ocean). Nat. size. 



Fig. 43. Forma tripartita. (Siboga-Exp.). Nat. size. 



Fig. 44. Forma pusilla. (Siboga-Exp.). Nat. size. 



Fig. 45. Forma rotunda (Siboga-Exp.). Nat. size. 



Fig. 46. Filaments of central strand, longitudinal view, shewing pits at point of fusion. < 140. 



Fig. 47. Filament of central strand from forma ovata, shewing its course without fusion from 

 one internode to the next. In the node the wall is much thickened ; this is represented 

 by the shading. x 65. 



Fig. 48. Optical transverse section through apex of plant, just below the ends of the fused 

 filaments, shewing the whole of the central strand. The external walls of the outer 

 filaments form one continuous line which sharply delimits the strand. At :; a few 

 peripheral cells are shewn. In the lower part of the figure three peripheral cells 

 are seen surrounded by central filaments. • 1 40. 



Fig. 49a, è. Two groups of peripheral cells, surface view. ■ 140. 



Fig. 50. Peripheral cells, longitudinal view. 140. 



Fig. 51. Rhizoids. 140. 



