F. Borgesen: Phæophyceæ of the Danish W. Indies. 31 



Occasionally from the basal cell in the sympodium rhizoid- 

 like fdaments grow downwards between the larger barrel-shaped 

 cells of the main filaments (Fig. 18 a). 



Below the growing point the cells in the filaments remain 

 short, further down they grow longer, nearly barrel-shaped, reach- 

 ing a length of up to 200 fi or even more and a breadth of up to 

 80/*. The cells are nearly colourless and as mentioned above 

 firmly connected ; upon a transverse section (Fig. 19 d) we find 

 this central tube to be composed of several layers of cells. 



This central tube is entirely surrounded with the dense layer 

 of assimilating filaments. From the outer side of nearly all the 

 cells in the peripheral filaments short branches grow out (Fig. 19 

 b, d). Their basal undivided part mostly consists of a single cell 

 or rarely of two or three, these cells bear the assimilating fila- 

 ments sometimes also a hair. 



The assimilating filaments consist of a series of cells, the 

 lowermost nearly cylindric and thin, those higher up thicker and 

 moniliform; they have all, especially the uppermost cells, well- 

 developed chromatophores. The diameter of the basal cylindrical 

 cells reaches a length of about 8 tu, that of the upper moniliform 

 cells of about 13 p.. 



The diameter of the hairs is about 11 (u long and the upper- 

 most cells in these reach a length of up to 12 times the diameter. 



The plurilocular sporangia are formed by outgrowths from 

 the uppermost cells of the assimilating filaments (Fig. 19 a). These 

 cells, often several together, grow out to conical, or sometimes 

 quite irregular, or even branched bodies which are divided by 

 means of transverse and longitudinal walls. The gametes escape 

 through an opening in the upper end of the sporangia (Fig. 19 a, d). 



A few unilocular sporangia were found together with the 

 plurilocular sporangia in the same plant (Fig. 19 c) ; these are 

 placed at the base of the assimilating-filaments. They are oval- 

 ovate of shape, about 40// long and 60 p broad. 



The description of the method of growth of Castagnea (Eudesme) 

 virescens given by Reinke 1 ) and especially by Schmitz 2 ) differs, 

 it cannot be denied, most essentially from that I have found in 

 my plant. Besides Castagnea, Schmitz also examined a Mijrio- 

 cladia sp. and as to them he writes as follows: "Dabei fand ich 

 nun, übereinstimmend bei den beiden genannten Arten, dass in 



J ) Reinke, J., Algenflora der westlichen Ostsee, p. 76. 

 2 ) Schmitz, Fr., Kleinere Beiträge zur Kenntniss der Florideen, V. (Nuova 

 Notarisia, vol. 5, 1894, p. 707). 



