218 KJELLMAN, THE ALGM OF THE ARCTIC SEA. 



The stipe, i. e. that part of the cauloid portion which does not produce sporo- 

 phylls, is alw;iys short, usually 1 — 4 cm., seldom even 6 cm. long, terete, or upwards 

 very slightly compressed, in old individuals even 8 mm. in diameter (tab. 25. f. 12). 



The rhachis, or that part of the cauloid portion which produces sporophylls, be- 

 comes longer as the plant grows older. In certain specimens I have examined, it has 

 a length of even 15 cm. It is compressed in its whole length, most so in the part 

 that bears sporophylls at the time; there a transverse cut shows the narrowest ellipse 

 with the longest longitudinal axis. Above the sporophylls it tapers swiftly, passing 

 abruptly into the costa. Cp. tab. 25 fig. 13 — 15. Even in older specimens the rhachis 

 is easily distinguished from the stipe, because through all its length it bears cicatrices 

 of fallen sporophylls, the cicatrices being downwards thin, upwards very dense and 

 forraing small elevations on a ridge running on each side of the rhachis. 



The lamina is linear-lanceolate. In regard of the form of its base the lamina re- 

 sembles that of A. esculentn f. musoefolia. I have not seen specimens with longer lamina 

 than about one metre. In older individuals the lamina is usually 4 — 8 cm. broad at its 

 broadest part; however, I have seen individuals in which the breadth of the lamina attained 

 11 — 12 cm. In younger specimens the lamina is richly plicate and wavy, in older it is 

 more plane and at the same time of firmer consistency. The lamina is thinner than 

 in A. esculenta f. typica, resembling that of A. membranacea (tab. 20 and 21). 



The costa is broad, and vei-y prominent, sometimes rising equally on both sides, 

 sometimes more on the one side, passing immediately into the lamina (tab. 25, fig. 10). 



The sporophylls are elongatedly linear-linguiform, in younger specimens shorter, 

 in older even 20 cm. long, usually 1,5 cm. broad below the top, sometimes even 2,5 cm. 

 They taper strongly, but evenly, towards the base, passing almost imperceptibly into a 

 pedicel 2 — 4 ram. long. While sterile they are raembranaceous in the greater part of 

 their length, and even after the zoosporangia have been developed, they are far more 

 slender and less firm than in A. esculenta. They are alvvays richly wavy and almost 

 always twisted spirally several times downwards. Those first developed are thinly 

 placed and distinctly separate, the following are densely crowded. In older individuals 

 they are very numerous, densely clustered, sometimes 60 or more in one individual. 

 The sorus reaches from the base of the sporophylls to about two thirds of their length 

 and is surrounded at the sides by a narrow, finely wavy margin. The zoosporangiferous 

 part of a sporophyll is membranaceous-coriaceous, the rest of it is membranaceous 

 (tab. 21). 



The zoosporangia are cylindrically spindle-shaped with blunt ends, about 40 ^. 

 long and 10 — 12 ,«. in diameter. As to these measurements it ought however to be 

 reraarked that I have had only a little nnmber of specimens with fully developed zoo- 

 sporangia at my disposal. 



The paraphyses are elongatedly wedge-shaped in optical longitudinal section, about 

 10 ,«. in diameter at the top. The outside of the membrane is thick and strongly 

 gelatinized. 



Structure of the frond. In anatomical structure the present species offers several 

 differences from A. esculenta. A cross cut of the stipe and the lower part of the rhachis 



