KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 20. N:0 5. 135 



Geogr. Distrib. It is known only from the Atlantic region of the Polar Sea, 

 reaching its maximum of frequency at Nordlanden. Its northernmost locality is Gjes- 

 vaer about Lat. N. 71°. 



Delesseria Montagnei novum nomen. 



Delesseria denticulata Mont. Syll. p. 408. Cfr. Ann. d. Sc. 9, p. 62. 

 Descr. Hypoglossum denticulatum KiJTZ. Tab. Phyc. 16, p. 6. 

 Fig. » » » » » M t. 15. 



Syn. Delesseria alata /? angustifolia Lyngb. Hydr. Dan. p. 8. 



Remark on the species. In the collections of Greenland alga) belonging to the 

 Copenhagen Museum there is a pretty great quantity of specimens, evidently gathered 

 at different occasions and by different persons, of a Delesseria bearing the name of D. 

 alata. Some of these agree very well with the above-quoted figure in Kutzing, others 

 approach more nearly to D. alata. However, they all differ from the latter species 

 by their more spreading branches which are never so obliquely out out at the base 

 and consequently more regularly linear or elongated-cuneiform than in D. alata. Besides, 

 the branches, especially those of the last order, are always distinctly, sometimes den- 

 sely, serrate. Thus there can be no doubt, 1 think, that the specimens from Greenland 

 are not to be referred to D. alata, but to D. denticulata Mont., which must be regarded 

 as a species distinct from D. alata and most nearly related to D. spinulosa Rupr. J. G. 

 Ag. known from the Pacific, if it be not indeed quite identical with this. It is difficult 

 to draw any definite limit between them. Montagne has himself declared that his 

 species is identical with D. spinulosa. Ruprecht states that D. spinulosa is closely 

 allied to D. alata f. denticulata, but differs from it by the narrowness of the branches of 

 the frond which are crispy at the margin, by the more spreading lower secondary axes 

 which spring out almost at right angles, by some difference in regard to the lateral 

 nerves which I do not quite understand, and by the tetrasporcs being developed some- 

 what farther down from the tips of the axes. With regard to the breadth of the frond, 

 the specimens from Greenland vary much, from 4 mm. to 1,5^ — 1 mm. and even less, 

 in case D. alata ft angustifolia Lyngb., as is most probable, is a slender form of the 

 present species. Broader specimens from Greenland often have a distinctly crisp mar- 

 gin. The branches are in general very much expanded, so that the lower ones, in 

 several specimens of D. denticulata, form a right or nearly right angle to the main axis. 

 In D. denticulata the development of tetraspores both begins and extends farther down 

 than in D. alata. Cp. Ruprecht, Alg. Och. p. 244. 



J. G. Agardh has some doubts about the identity of D. spinulosa and D. denti- 

 culata, chiefly because the latter, as figured by Kutzing, wants the microscopic lateral 

 nerves, which are to be seen in D. spinulosa. But it should be remarked that it is 

 stated expres.sly in the diagnosis that accompanies the figure in Kutzing 1. c. p. 6, 

 Msegmentis .... a costa ad margines venis obliquis percursisM, and that the lateral nerves 

 in the specimens of D. denticulata from Greenland are always, especially in broader 

 sterile individuals, distinctly apparent on microscopical examination, sometimes even 



