112 KJELLMAN, THE ALG^. OF THE AECTIC SEA. 



pogon has not, from some cause or other, coiue to a normal development. It is also 

 possible, that in certain cases the branch-systems destined to the formation of tetra- 

 sporangia may, after some few reproductive cells are produced, develop themselves for 

 vegetative purposes. 



The structure of the fr ond. Fig. 7 is a part of a cross-section, fig. 8 of a longi- 

 tudinal section, of the main axis of the frond, near the base, of an older specimen. 

 These sections show that the largest part of the frond consists of a parenchymatous 

 tissue, whose thin-walled cells, that are destitute of or very poor in endocrom, dimi- 

 nish gradually in size from within outwards, where they are surrounded by a cortical 

 layer of small cells rich in endocrom, which layer is sharply defined from the inner 

 mäss of the tissue. The pericentral siphons as well as the central siphon are of in- 

 considerable width. 



The organs of i^o^yagation. The sporocarpia are ovato-urceolate, with a short 

 neck. The spores are pyriform, about 100 u. long and 50 ,</. thick. The tetrasporangia 

 are large. The antheridia are slenderly cylindro-conical, greatly variable in size, but 

 in general about 100 ,m. in diameter near the base. 



The other species of Rliodomela from Bohuslän, the Rh. subfusca f. extratceniensis 

 vel normalis of J. E. Areschoug is clearly identical with Fucus subfuscus Woodw., Tuen., 

 Stackh. and FL Dan., and accordingly ought to be called Rhodomela. subfusca (Woodw.) 

 Ag. It is certainly a well-known species,. But in order to point out its discrepancies 

 from the preceding one, I give figures on plate 8 referring to it, together with a de- 

 scription of specimens from Bohuslän. 



A fi-rst years plant, sterile, from a specimen from Bohuslän, taken in the month 

 of December; iig 1. 



The plant becomes altogether black in drying and adheres firmly to the paper. 

 The axes retain tlieir terete forin, or are at least only almost imperceptibly compressed. 

 The hold-fast is a callus, from which issue oftentimes several systems of axes, in ge- 

 neral uiiequally developed. My description refers to an one-stemmed, thinly branched 

 specimen. A main axis is traceable only for some dlstance upwards in the frond. As 

 elements of ramification we may consider, I think, 1) short cylindrically subulate 

 branches, about 5 — 6 mm. in length; 2) fastigiate branch-systems of the same length 

 with the preceding, whose primary axis bears a few side-axes only near the top; 

 3) branch-systems, 5 — 8 cm. long, generally slenderly lanceolate, whose main axis bears 

 side-axes of the two preceding types. These elements are combined in a more or less 

 distinctly racemose manner. The racemnse arrangement often becomes, however, diffi- 

 cult to follow, because the main stem, as well as the primary axes in the branch-system 

 of the iirst order, becomes sooner or låter untraceable, a branch-system of the next 

 higher order being developed of equal strength with the general axis above the point 

 where the branch-system springs out. The difference in thickness between axes of next 

 different orders in not considerable. The varieties I have observed with regard to the 

 äbove-mentioned ramifications, are limited to the elements 1 being sometimes more 

 numerous, sometimes less nuraerous tlian elements 2, and to elements 3 being now and 

 then shorter than I have stated above. 



