— 340 — 



layer (mesoderma A). Braun) forms the greatest part of the membrane of 

 the head and the wliole substance of the stalk inside the external layer. 

 The middle layer is homogeneous in the head and usually also in the 

 stalk, but 1 have sometimes found it consisting of several curved, trans- 

 verse layers (fig. 2, h) especiahy in the upper part of the stalk ; also this 

 has been noticed by Al. Braun (1. c, Tab. I fig. 15—16). 3° a thin 

 internal layer turning yellow by chlor-zinc-iodide. Both the stalk and 

 the membrane of the head do not consist of cellulose, but all the layers 

 of the membrane, both in head and stalk, seem to consist of a pectose, 

 as they turn red by ruthenium oxychloratum ammonia. 



'^I'he head contains one large, parietal chromatophore of a net-like 

 structure and of a shape resembling a sack with a longitudinal opening, 

 from which inside some bandlike thickenings are going inwards inio the 

 cell, as pointed out by Schmitz (Ghromatophoren p. 44) ^). The chrom- 

 atophore contains numerous , irregularly distributed pyrenoids surrounded 

 by a starch-envelope, but singly occurring granules of starch are also 

 frequent and sometimes in large quantities. The cell contains only a 

 single, rather large nucleus, as pointed out by Al. Braun (I.e.); it is 

 situated at about the middle of the head or somewhat above the middle, 



Codiolum gregarium Al. Braun is the most fully described species of 

 the genus, and as the Icelandic plants very well agree with it, I have 

 referred them to it without hesitation. The other species of the genus 

 are more or less unsufficiently known and are essentially separated by 

 very variable characters, as the size of the frond, the shape of the head 

 and the relation between the length of stipe and head. Judging from my 

 material, described above, I think that these characters are of no essential 

 value as specifically distinctive characters. Both Kjellman (Arct. Alg. p. 319) 

 and Bdrgesen (1. c.) seem to be of the same opinion -). Codiolum lon- 

 gipes Fosl. has already by Batters (Marine Algae p. 264) and by Borgesen 

 (1. c.) been identified with G. gregarium Al. Br. Borgesen (1. c.) maintains 

 the two first-described species, G. pusillum Lyngb. and G. gregarium Al. 

 Braun, and proposes to refer the other species of the genus, with excep- 

 tion of G. Petrocelidis, as forms to the one or the other of these species. 

 I am also of the opinion that G. pusilhuii (Lyngb.) and G. gregarium Al. 

 Braun, at all events provisionally, ought to be regarded as independent 

 species, and possibly G. Nordenskioldianum Kjehm., G. brevipes Fosl. and 

 G. intermedium Fosl. will turn out to be forms of G. gregarium Al. Br., 



') Schmitz (I.e.) describes the shape of the chromatophore of Codiolum as 



orbicular (^scheibenformig"). 

 '') Cfr. also Fosl. Nye havsalg. p. 191. 



