271 



complanated, especially in the upper end of the shoots (Plate IV fig. 6 ). In speci- 

 mens from deeper water it sometimes happens that some of the branches assume 

 a special character, growing out as slender, unbranched, irregularly curved organs 

 taking not the upward direction but growing in a transversal direction or more 

 downwards. They resemble either rhizomes or tendrils but have usually not the 

 function of either of these organs (Plate IV fig. 7). It may however happen that 

 the end of such a branch fixes itself on any solid substratum, f. inst. molluscs, 

 Furcellaria, Zostera, developing an adhesive disc similar to the primary crustaceous 

 frond. It is connected with the ultimate joint by a genicle. Such adhesive discs 

 may also develop at the end of ordinary fronds coming accidentally in contact 

 with any solid body (fig. 195). These discs have the power 

 of producing new articulated fronds, in a similar manner to 

 the primary ones (fig. 195 B). 



The age of the articulated fronds is not known. They 

 reach a length of up to 16 cm, usually however only 10 cm. 

 Supposing that a long pinnated shoot is produced every year, 

 it seems probable that the age of the erect fronds does not 

 exceed 3 or 4 years. 



The joints consist of a central tissue of elongated cells 

 and a cortex not sharply limited from it, the cell-rows at the 

 periphery of the central tissue bending outwards and consisting 

 of cells becoming gradually shorter outwards. The cells of 

 the central tissue are usually 5 — 8 times as long as broad ; 

 they are disposed in transversal zones, their end-walls being 

 situated about at the same level, the limiting lines being, 

 however, convex upwards (comp. Mrs. Weber, Siboga pi. XVI 

 fig. 15, 1904). The cells are as usual connected with primary 

 pits at the end walls, while secondary pits do not occur^), but lateral fusions 

 between the cells of the central strand are very numerous and more than two cells 

 frequently fuse together. As mentioned above, p. 211, I found these fusions followed 

 by a fusion of the nuclei in a tetraspore-bearing plant. 



In a female specimen with ripe cystocarps collected in winter at Frederikshavn 

 similar cell-fusions were found, but the behaviour of the nuclei was different, those 

 of the central tissue having divided in two to four, while such divisions were not 

 observed in the tetraspore-bearing plants. It was therefore not easy to decide 

 whether fusion of the nuclei took place in the female plant. It should be of much 

 interest to decide whether there is such a constant difference between the tetraspore- 

 bearing and the sexual plants. 



The cortex of the joints is covered with a continuous layer of low cover-cells 

 (comp. Solms, Corall. p. 29). 



') PiLGER states, however, that the longitudinal walls in the central tissue of Corallina are pro- 

 vided with pits (1908. p. 252). 



Fig. 195. 

 Corallina officinalis. A, ad- 

 hesive disc developed at the 

 end of an ordinary shoot on 

 coming iu contact with a 

 shell. B, adhesive disc devel- 

 oped from the ultimate joint 

 of a shoot coming in contact 

 with a rhizome of Zostera; 

 scars after articulated fronds 

 developed from the disc but 

 fallen otT are visible. 3:1. 



