96 K.JELLMAN, THE ALG^ OF THE ARCTIC SEA. 



paid special attention to the present form, I have found that it is ever like itself every- 

 where in the Arctic Sea and does not show any variation at all in the direction of 

 L. fasciculatum, from which it is easily distinguished at first sight even by the external 

 shape, besides differing from it by general and essential diversities of structure. The 

 only species I know, to which it shows any greater affinity, is L. intermedium described 

 below, which differs however rather considerably in external characteristics, besides bearing 

 regularly tetrasporic sporangia. Thus the present alga seems to me to be a good species, 

 and I have consequently had no hesitation in giving it a separate name. The genus Litho- 

 thamnion has been hitherto rather much put aside, on account of the difficulties con- 

 nected with a nearer investigation and characterization of the forms; in consequence 

 whereof certainly only some of the most remarkable of its numerous forms have been 

 hitherto described and cleared up satisfactorily. After the publication of Solms-Lau- 

 bach's excellent work (Corall. Monogr.) and Hauck's comprehensive researches, the 

 Mediterranean forms may be considered to be essentially cleared up. That much re- 

 mains to be done with regard the northern species, is a fact of which I have clear evidence. 



Hah. The present plant is a deep-water form. Most often and in the greatest 

 number it is met with at a depth of 10 — 20 fathoms. It thrives best on a bottom 

 consisting of shingle, gravel, and shells, and is found on open shores as well as in 

 sheltered bays. It is gregarious. On the coasts of Spitzbergen and Novaya Zeralya 

 it covers the bottom in deep layers for several miles, and altogether determines the 

 general aspect of the vegetation, wherever it occurs. In the formation of future strata 

 of the earth's crust in these regions it must become of essential importance. On the 

 coast of Norway I have met with it only occasionally, amongst other Lithothamnia. 

 At Spitzbergen it bears ripe sporangia both in summer, in July, and in mid-winter, in 

 the months of November and December. On the coast of Norway and the west coast 

 of Novaya Zemlya, specimens with such organs have been collected in summer, in July 

 and August. I have never seen specimens bearing carpospores. 



Geogr. Distr. The species is dispersed over the greater part of the Arctic Sea. 

 Only from the Kara and Siberian Seas it is not known. It attains its most vigorous 

 development, as far as I know, at Spitzbergen and on the west coast of Novaya Zemlya, 

 where it occurs also in the greatest numbers. The northernmost place where it has 

 been found, is Treurenberg Bay on the north coast of Spitzbergen Lat. N. 79° 56'. 



Localities: The Norwegian Polar Sea: Nordlanden at several places in deep 

 water; Finmarken rather scarce and local, as at Maaso, Gjesvaer, and in MagerO Sound. 



The Greenland Sea : common and plentiful on the west and north coasts of Spitz- 

 bergen. 



The Murman Sea: the coast of Russian Lapland and the west coast of Novaya 

 Zemlya, in the latter locality common and abundant. 



The American Arctic Sea: Probably the plant reported from here by Dickie (Alg. 

 Sutherl. 1, p. 142) under the name of L. fasciculatum, is the present species. 



Baffin Bay: I have seen specimens from the west coast of Greenland, collected 

 there by Prof. Th. M. Fries. 



