KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 61. NiO II. 49 



L. nigrescens in the shape of the leaves. The anatomical structure is not quite like 

 that in the latter, as the cortical cells are larger and the medulla more dense in L. 

 frulescens. Mucilage ducts are present. Still, it is possible that L. frutescens is nothing 

 but a local form of L. nigrescens, quite destitute of a prolonged stem and with smooth 

 leaf-margins, characters also observed in the narrow-leaved northern form of the 

 latter. 



Macrocystis Ag. 

 M. pyrifera (L.) Ag. — Skottsb. Ant. Meeresalg. I p. 80. 



I have little to add to my old description, but it may be mentioned that small 

 plants were observed in tide-pools in some stations and that fertile plants with sori 

 on the normal floating leaves were collected at South Georgia in April. 



Further, two forms of a very remarkable appearance were observed. 



1. A form from the narrow strait between Westpoint Island and the main 

 West Falkland Island. 



Table oj measurements in mm. 





V 



e s i c 



le 







L a m i n a 





Length of 

 internodes 



Length 



Diam. 





L:D 



Width of 

 pedicpl 



Length 



Width 



L:W 



148 



24,6 





6,1:1 



10 



835 



59 



14,1: 1 



230 



The length of the measured branch was almost 20 metres, the diameter of the 

 stem about 1 cm. The internodes (not fully developed ones not counted) were 83 

 in number; 75 vesicles were left, of which 59 bore more or less intact laminse. The 

 leaves were thick and firm, with an absolutely smooth surface and quite lacking the 

 longitudinal wrinkles otherwise so characteristic; they bore long, slender marginal teeth. 



lf we compare this form with the plants measured in 1902 (1. c. p. 115), we 

 shall find that it surpasses every one of them in the size of the vesicles. The leaves 

 are very narrow in comparison with their length, being about 14 times as long as 

 broad, while among the previously measured forms the relation 7,3: 1 comes nearest. 

 The length of the internodes is surpassed only by the form from the entrance to 

 Moraine Fiord in South Georgia, where there is a heavy surf on the submariue bank. 

 The present form with its thick, smooth leaves differed greatly from anything I had 

 seen before and certainly would have been described as a good species by the old 

 authors. Probably no form from such as locality as the Westpoint Passage, where 

 the tidal currents rush through with a velocity of 6 to 7 knöts an hour, had been 

 examined before. 



2. Just on the south side of Angostura de los Témpanos, the narrows in Canal 

 Gajardo between the Xaultegua Gulf and Skyring, where the tidal current is very 

 strong, probably stronger still than in the case just mentioned, there grows a Macro- 



K. Sv. Vet Akad. Harull. Band fil. N:o 11. 7 



