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



205 



often comes very near to true dichotomy, . but when exam- 

 ined more carefully one finds that one of the young cells 

 is always formed a little earlier and is larger than the other 

 (comp. Fig. 192 c, d). Lewis, too, (1. c. p. 250) considers the 

 ramification to be lateral, "true dichotomy appears never to occur". 

 In Griffithsia corallina Kylin^) found the ramification to be 

 lateral, and Oltmanns says in Handbuch the same for Griffithsia 

 on the whole. 



As pointed out by Lewis, and according to my material also, 

 by far the greater part of the specimens were tetrasporic. The 

 tetrasporangia form a 

 ring at the upper end 

 of the cell (Fig. 192 a). 

 As a rule three of them 

 are found together, one 

 of them placed termin- 

 ally, the others later- 

 ally upon a basal cell 

 (Fig. 193 a, d) ; the 

 development of this 

 tetrasporic branch is 

 given by Lewis. 



On the outside this 

 tetrasporic ring is pro- 

 tected by a circle of 

 short, thick somewhat 

 inwardly curved cells, 

 together forming a kind 

 of involucrum (Fig. 



192 a). As pointed out 

 by Lewis these cells 

 grow up immediately 

 from the cells in the 

 main filaments (Fig. 



193 a). In Griffithsia 



corallina Kylin (1. c, p. 116), on the other hand, describes and 

 beautifully delineates the protecting cells as excrescences from the 

 basal cell in the tetrasporic branch. A cell is cut off from the 

 basal cell, and this cell is divided into two cells, the uppermost 

 being very enlarged and becoming a protecting cell. This way 



') Kylin, H., Die Entwicklungsgeschichte von Griffithsia coraUina (Lightf.j 

 Ag. (Zeitschr. f. Botanik, 8. Jahrg., 1916, p. 99). 



Fig. 192. Griffithsia globifera (Harv.) J. Ag. 



a, part of a tetrasporic plant, b, a dwarf shoot. 



c and d, upper ends of main filaments showing 



ramification, (a, about 25: 1 ; b, about 250 : 1); 



c and d, about 30 : 1). 



