168 
Simmons, Remarks about tlie Relations of the Floras etc. 
referring of a species to one of tlie groups or another is solely 
based upon liow far southwards or northwards the writer thinks 
it to be found, there must be an everlasting interchange of 
species between the groups, especially the northatlantic and the 
subarctic series, as is easily seen by comparing the lists in the 
above mentioned treatises and those of Rosenvinge (44) and 
Börgesen (8). Comparisons of percentage of species, referred 
to those series, such as are to be found in the papers quoted, 
can not be of the slightest interest, as it is seifevident that, if 
species that have their distribution chiefly far northwards are 
ealled arctic, those with a somewhat more southerly area, sub- 
arctic, a. s. o., a coastline further to the north will always show 
a greater percentage of „arctic“ species, than one farther south- 
wards, and vice versa — if not some special circumstance plays 
in. Börgesen (8) for instance devotes severai pages to such 
examinations and comparisons, as the „result“ of which it appears, 
that in the flora of the Faeroes (lying in the northern Atlantic) 
there is a verv great percentage of „northatlantic species“. 
The table (VI) shows, that most of the arctic algae are also 
found in some parts of the Atlantic (87 per ct.). Of these 
again 64 (40 per ct. of total number) are also spread to the 
northern part of the Pacific. Among these we will find most of 
the species, which have a wide distribution in the arctic seas 
and also a few species with a very wide ränge, such as are 
found again in the Southern temperate region or even in the 
antarctic, and also such as are spread even to the warmer 
parts of the oceans. The species common to the arctic flora 
and that of the Pacific are much fewer than those, which the 
former has in common with the atlantic one, 70 species (44 per 
ct.:. Of these 6 only are not found even in the northern 
Atlantic, namely Älciria dolichorachis , * Laminaria cuneifolia, 
* Rhodymenia pertusa, Rhodomela larix, Ptilota asplenioides , *Dilsea 
integra. Hereto comes further Laminaria solidungula if that 
species really grows in the Pacific and not only young specimens 
of Gymathere triplicata are taken for it as Setchell (49, p. 260) 
thinks. Of the six species three, marked with *are found also in 
parts of the Polar Sea lying north of the Atlantic. Kj eil man 
(30, p. 53) sees in the existence of such a distribution a proof 
for the assumption of a centre of dispersion in the Polar Sea 
itself. I will not deny, that so may have been, only I think 
the continuity of the evolution within the Polar Sea very 
doubtful. There also are atlantic species that reach far into 
the arctic area, even north of Asia and America. Such are: 
Chantransia efflorescens , Turnerelia Pennyi, Rhodochorton 
penicilliforme, Lithothamnion foecundum ; more dubious are 
Laminaria digital a, L. longicruris , Rhodochorton sparsam, 
Cruoriella Dubyii. I do not however think there is too much 
stress to be laid on this fact. The three pacific-arctic species, 
which only go a short way into the arctic sea from Bering 
Strait, viz. Maria dolichorachis , Rhodomela larix , Ptilota asple- 
