Wa
THE BOTANY

ICELAND

EDITED

BY

L. KOLDERUP ROSENVINGE

PH. D.
AND

EUG. WARMING — eon aia

PH. D., SC. D.

PART I

\ 1. THE MARINE ALGAL VEGETATION BY HELGI JONSSON, jd 0 fe D.

ee
te oie sear

(PUBLISHED BY THE AID OF ‘THE CARLSBERG FUND)

COPENHAGEN
J, FRIMODT

LONDON
JOHN WHELDON & CO.

1912

THE BOTANY
ICELAND

EDITED

BY

L. KOLDERUP ROSENVINGE

PH. D.

AND —

EUG. WARMING

PH. D., SC. D.

PART I
1. THE MARINE ALGAL VEGETATION BY HELGI JONSSON, PH. D.

(PUBLISHED BY THE AID OF THE CARLSBERG FUND)

COPENHAGEN
JP RIMO DS?

LONDON
JOHN WHELDON & CO.

1912

PREFACE.

[ was mentioned in the preface to the “Botany of the Ferées’’ (Co-
penhagen & London, 1901—1908) that, on the completion of that
work, Iceland would be the one island among the dependencies of the
Danish kingdom in the Atlantic which was in most need ofa thorough
and systematic investigation as regards its botany, and the hope was
expressed that this would be commenced as early as the year 1909.
This hope has been so far realized that we, the undersigned, are now
able to publish the first paper on the subject, viz. “The Marine Algal
Vegetation” by Dr. HELa1 JOnsson of Reykjavik. Iceland, however, is
so large compared with the Fero6es that the investigation will not only
be far more difficult to carry out, but will also extend over a far longer
period.

We hope that specialists in botany may be able, at short intervals,
to visit the island and make collections and notes. Thus, even in 1910
a young bryologist, A. HESSELBO, studied the moss-vegetation — when
he took the photographs, published in the present paper — and this
summer he is again paying a visit to the island, after which he will
prepare an account of the moss-flora and the moss-vegetation of Iceland.

Next summer we hope that a young lichenologist will be able to
set to work in a similar manner, and will be followed by others, until
the work can be completed with a general account of the vegetation and
the plant-geographical position of the island.

L. KOLDERUP ROSENVINGE. EUG. WARMING.

COPENHAGEN, Aug. 1912.

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1.

THE MARINE ALGAL VEGETATION
OF ICELAND

BY

HELGI JONSSON

PH. D.

WITH 7 FIGURES IN THE TEXT

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CONTENTS.

Page

UE OG AISES TE 6 op gal IIe a calor 26) CIRC DS 1
Pee nemie Mabie ALR 82 oe oa wes ba Wile oe RL a ide Was Nadie ee bs 5
II Life-conditions of the Marine Algal Vegetation....................4. Tr)
MMC MNAtUEe OL ‘The COASE heats alls URS OPP bl 25

PoE CROCEAN St 7m i dente Coe RN OAs ara uRhh, OMS. Pie scaes <P an clans bie 27
Aumiinen Movements of the Ocean iH0 61652 nerd A Sale claw eee oa ea ee 27
ae Wh eImPerAavUre ORME VWALER HAI MYO RIAA TIA. a dine wie we we 32
Creare SaAlimIeyA Mr Poe Seah Me Be RUN wide ve Ro aN GMA s cea we we» en 40
mmbber ies. has oss SAI. LERAMTI aay Ds aed Pe Sa Mr 42
meg eTEDELALITGNe” se cients, Hae SEER aa ls ates, stk clale Nie Sake eke 42
EmMincwelumnidityers sont cathe tren RANE Ae To VS coed 44

C. Precipitation, Amount of Cloud, Foggy days, Wet days.......... 44

DEN EILOS 6 stisa' Me aies. 5 uted diaaete lak eh Sah BMA Hans tutte, ayancane At is 46

dey UGE TATE) TES cae ie ae OM ect RES Exe Medes og: Weer ee ts 0 Ps Sen 47

III The Horizontal Distribution of the Species and the Components of the

PMA M LOR Awe Sees tvs yin ehe ne Gate daa RER e Ri eee Sig! akvRalai des was 642% 48
iweeGomponents ot the rAlaal Flora vaso ccc. oote oh ee eee ee ew oe ees 58
AC SAT CEICe Croup tii: Leh Sey MD ee i Ede R Eee, 58
eR SO A OCLC AGO’ Poot 'cs.., sah sca eae ena ard Segue meee A Oe el ges ee es 59
Cr, ther boreal-Aretic- Group... ssi ees seb e ss EAEoR Ne PER BIR Oe 60
Drie Gold Bored le Groupits ick s Uh sa Sees Sie ahs el eyalnatesle wloales Hae, s 61
Bie lie: WW ania Onedle, GROUP joo, 22 sid cals ss ya el ene Bees & oh a Sed 62
PL ORISVICM ls OUMGARLESH s. 08 5.280 Ts ot ab oat bleu OaOnia Duid ds. eo ale Oe sa ale ee 66
IV Comparison with neighbouring Floral Districts ........................ 68
Ve, Dhe Vertical Distribution of the Spegies..c:.. 0... 6.5 ccc swan ve emes 80
Aes CAPER mE AthOral YZOME hamlets ope eee) oh ehacaph vr Aadal wh eee ede eae aealsas 85

B. The lower Littoral Zone and the Belt below down to a depth of
PUD IO Me ORME ER ESE one Modi. cities at. Veen apse eG ewiishiin siete pee aiaeW @ 6 6 ¥ cash ses ak 88
MMe E SUIITCLOrAl SPECIES) ajc soc cPeo8 see Sod vow ee ha, olha ote eee awe ew N 91

MOE ee GITLES Obs GLO WGEEowe nian giciaie kon a's, oS aim ache ga ee bie wa ela aie eine we wees 92

VI Marine Algal Vegetation and Sea-grass Vegetation. 2. &: vcd os sce. 95
Account of the Marine Algal Vegetation and the Sea-grass Vegetation... 98
A> The, Marine Algal Vesetationwy. otc i. sent e eroie, cuant Gene <' diiaeeen
a: “fhe: Littoral Zone ices tae eee se atie ices ons ae 99
aa. The Photophilous or strictly Littoral Communities....... 99
1. The Prasiola stipitata-association .............)..2 mee 100
2. The Gommunity of Filiform Alpe 7... 2... 4 102
3. The Community of Fucaces ).. 0005.4. 5.5>.. 7. cee 106
4. The Enteromorpha-association.. -9..... =... -)eeeee 120
5. The Acrosiphonia-association® ...5..:%.. 5 -.- eee 121
bb. The Shade-vegetation .2)...0405)..% «oon Hae Sis oe 123
6. The Hildenbrandia-association <<... .5: 2.2. . «2s 123
7. The Rhodochorton-association, the Sphacelarietum bri-
tannici and the Polysiphonietum urceolate .......... 123
cc. “The Vegetation “of “Yide-Pools... 02. 2 a. ee le 125
b, ‘The ‘Semi-littoral Zome |... . os. <5 May oh. oe eee 128
8. The Monostroma-association. .«...-:....-. 4)... eee 129
9... The Chorda-association: : -o.d1.4% ossitiecee be oe 130
10.. The Community of /Rhodymenta:;;:.~.:\..4-- 4) eee 132
11. The Polysiphonia urceolata-association ..............., 133
12. The Community. of Corallina .......-.....5th ose 135
13. The Crustaceous alga-association...........6.-.+.ese see 138
ce... The: Sublittoral Zone ¢ 2.25366 vey ban onl tee 139
14. The Community of Laminariacez .................... 140
15, . The Desmarestia-association......)...... 2s. Heltete eee 151
16. The Deep-water Community of Floridee.............. 152
17. ‘The. Lithothamnion-association , ... .. 2.22), - ose eee 154
18. The Community of Crustaceous Alga.).).>5...c pee 155
B. The Sea-prass Vegetation 2... 0.255... bs. Ve. ons ot wenoh Oe 157
The >Zostera-association 3: <.)..0 cs. seueoe: sce beo eo eke 157
VII Differences in the Vegetation in East and South Iceland ............... 159
VIII Some Notes on the Biology of the Algz along the coast of Iceland..... 166
1: "Duration “of Life 1), foci e fis cus oe Oak Oho 166
2. Periodical Changes ©... 0 5 <6 so 169
3. Littoral Winter-vegetation of Reykjavik............... 180
Bibliagraphiy execu s.t. eet eek fee aes . eS 183

INTRODUCTION.

T is far from being a fact that the Marine Algal Flora and

Marine Algal Vegetation of Iceland can be regarded as sufficiently
known; this does not apply in the same degree, however, to all
parts of the coast. East Iceland, South Iceland and South-west
Iceland are better known in this respect than North-west Iceland
and North Iceland. Also, as is very natural, the littoral vegetation
is better known than the sublittoral, as it is easier of access and
may be investigated directly on the spot, while, as regards the sub-
littoral vegetation, one has to be content with what is obtained
from dredgings.

Very little has previously been written with regard to the marine
algal vegetation of Iceland. Stré6mfelt, who travelled in Iceland
in the summer of 1883, has treated the algal flora exhaustively (see
Jonsson, 31) in his valuable work “Om Algevegetationen vid Is-
lands kuster” (70) and has given a critical review of the older lite-
rature of the marine algal flora of Iceland; but, on the other hand,
he has dealt very briefly with the marine algal vegetation. He fol-
lows Kjellman in dividing the vegetation in question into a litto-
ral and a sublittoral vegetation. Str6mfelt found the littoral vege-
tation poorly developed in many places — he records, however,
a luxuriant littoral vegetation from Reykjavik, Eyrarbakki and
Eskifj6rdur. The sublittoral vegetation is mentioned even more
briefly, and is emphasized as being more uniform than the littoral
as regards its distribution and the species which compose it. Str6m-
felt does not make any definite statement regarding the elittoral
vegetation, owing to his not having dredged in sufficiently deep
water, but he considers it improbable that any vegetation worthy
of notice occurs at that depth, as he did not find any rich vegeta-
tion at a greater depth than 10—12 fathoms.

The reason why Strémfelt found the littoral vegetation on the
north coast so poorly developed may be two-fold: it may result

The Botany of Iceland. I. 1

y H. JONSSON

from the drift-ice having remained at the coast during the whole
summer of the previous year (1882), but it may also be due to the
fact that, in this case, Stré6mfelt went by steamer from port to
port, and could scarcely have obtained a thorough knowledge of
the coast in as much as the steamer usually stops only a short
time at each port.

Str6mfelt mentions the following algal formations: the Fucacee-
formation which is reported from H6lmanes and Seley in E. Ice-
land; the Laminaria-formation, under which a subvegetation of
red alge is mentioned. Further, a Monostroma-vegetation is recorded
as occurring near Ekifj6rdur at a depth of two fathoms on a sandy
bottom, and a Halosaccion-formation at extreme low-water mark on
Holmanes. Strémfelt expresses the opinion, moreover, that a
Corallina-formation formed by Lithothamnion-species must exist,
but he does not say anything definite regarding this point, as he
received almost all the Lithothamnion-species from the fishermen
(70, pp. 10, 11). The description of the vegetation is evidently based
on observations made in places where Strémfelt stayed for a
longer time, viz. Eskifjé6rdur and Reydarfjérdur in E. Iceland, and
Eyrarbakki in S. Iceland. I have incorporated Strémfelt’s obser-
vations with my own in my description of the vegetation.

Stré6mfelt, on the other hand, treats exhaustively of the dis-
tribution of the species along the coasts. Thus he is the first to
substantiate the existence of two floral districts in the sea on the
coasts of Iceland: a cold-water flora in NE. Iceland and a warm-
water flora in SW. Iceland. In a table he gives a summary of the
distribution of the species along the coast of Iceland, and states
whether they are found in the Norwegian Polar Sea, the North
Atlantic and the Greenland Sea. He records 33 species as common
to NE. Iceland and SW. Iceland, 33 species as growing in NE. Ice-
land and absent from SW. Iceland, and 28 species as growing in the
latter district and absent from the former. Thus 66 species in all
are recorded from NE. Iceland and 61 species from SW. Iceland.
Of the species given by Strémfelt as being found in or absent
from NE. Iceland and SW. Iceland respectively, later investigations
have proved that far the greater number are common to both
places, but then, again, other species have been found which are
characteristic of the different districts. |

My description of the algal vegetation along the coast of Ice-
land is based mainly on my own observations, and further on

MARINE ALGAL VEGETATION 3

Stré6mfelt’s work, as well as on Ostenfeld’s observations. The
latter mainly concern the littoral zone, and originate from E. Iceland
(Hélmanes), SW. Iceland (Reykjavik, Njarévik) and S. Iceland (Stadur
on the south side of Reykjanes).

Ostenfeld, moreover, has given information of the sublittoral
vegetation of Myrakollur in NW. Iceland.

My own observations are drawn from various places encircling
the whole of Iceland. In E. Iceland I have especially investigated
Berufjérédur, Reydarfjérdur and Seydisfjéréur, and everything which
is narrated of the algal vegetation from E. Iceland originates from
these fjords. In N. Iceland I have examined Eyjafjéréur fairly ac-
curately, from its innermost part to the submarine ridge off Hrisey,
and I have, moreover, in the course of my journey, investigated the
head of Hunafléi. When travelling by the mail steamer “Laura”
round NW. Iceland I visited all the fjords from Skutulsfjéréur to
Patreksfjéréur. I stayed only a short time in each fjord, as I ac-
companied the boat from port to port, and was only able to dredge
and investigate the littoral zone in the vicinity of the towns. In SW. Ice-
land I have been at the south side of Breidifjéréur, and have dredged
along the stretch of coast from Rést in Hvammsfjéréur to Hjallasand-
ur, and have also examined the littoral zone over a far larger area,
not only round Sneefellsnes but also in Dalasysla. Round Reykjavik
I have dredged and investigated the littoral zone many times. In S.
Iceland I have investigated the Vestmannaeyjar most thoroughly and
have, in addition, dredged and examined the littoral zone at Eyrarbakki.
All remarks concerning the algal vegetation of S. Iceland are based
on observations: drawn from the western part of the south coast.
The eastern part of the south coast from about Stokkseyri eastward
is, as far as I know, a sandy coast, a “desert’’ devoid of algal vege-
tation. I have not dredged further east than round the Vestmanna-
eyjar, but on my trip through S. Iceland in 1901 I saw very few alge
cast ashore, which may be regarded as a sure sign that a desert lies
beyond, because, where algal vegetation exists, it is quite common,
with a landward wind, for large, often astonishingly large quantities
of algee to be thrown up on the shore. What might not be found
then, on the south coast, where the swell of the Atlantic rolls up
onto the flat shore, if any algal vegetation existed further out! Nor
can it be expected that anything but a desert exists off this coast,
as the bottom consists of sand, and the coast lies exposed to the
sea, like the west coast of Jutland. Where, on the other hand, there

1%

4 | H. JONSSON: MARINE ALGAL VEGETATION

are rocks, there vegetation is sure to occur. At Vik in Myrdal near
the southern point of Iceland there was, for instance, a poor vege-
tation on the rocks.

When one considers how great is the extent of Iceland’s coast-
line, one cannot expect this to be sufficiently elucidated as re-
gards the distribution of marine algze by the few and scattered
investigations which have been undertaken. For a long time, then,
I nourished the hope of being able to undertake further investiga-
tions, and therefore constantly deferred publishing a comprehensive
description of the algal vegetation. Now, however, I have decided
to delay no longer and hope in the future to be able to make a
more extensive contribution in several respects towards the eluci-
dation of the algal vegetation.

I. LIST OF THE MARINE ALGE.

HE following List of the Marine Algze of Iceland is extracted
from my earlier publications (JO6nsson, 31, Bérgesen and
J6énsson, 14) and from the paper by Henning Petersen (57)
on the species of Ceramium. It gives only the names of the species
with synonyms, their distribution in the different coastal districts
and some new habitats. The limitation of species is unchanged
except in the case of the genus Ceramium and in Clathromorphum
circumscriptum (Strémf.) which is included in Clathromorphum com-
pactum (Kjellm.) as proposed by Foslie. One species, Vaucheria
spherospora Nordst. (Bérgesen and Jénsson, 14), is omitted from
the list as it can scarcely be called a Marine Alga. Of Ceramium
5 species are added.
Thus the number of species is: —
76 Rhodophycez
67 Pheophycez
51 Chlorophycez
6 Cyanophyces

Total... 200 species.

The coastal districts are the following (see the map, p. 7): —

East Iceland (E. Icel.), from Lonsheidi (Eystra horn) to Langanes.

North Iceland (N. Icel.), from Langanes to Hornbjarg (Kap Nord).

Northwest Iceland (NW. Icel.), from Hornbjarg to Latrabjarg.

Southwest Iceland (SW. Icel.), Breidifjordur and Faxafléi from Latra-
bjarg to Reykjanes.

South Iceland (S. Icel.) from Reykjanes to Vestmannaeyjar and east-
wards to Lonsheidi (Eystra horn).

In “The Marine Algez of Iceland” (Jénsson, 31) the district NW.
Icel. is larger; it reaches from the inner end of Hunafldi to Latra-
bjarg instead of as now from Hornbjarg to Latrabjarg. Localities
from the part of the coast which stretches from Hunafldi to Horn-

6 H. JONSSON

bjarg are referred to NW. Icel., in the paper mentioned above, but
in the present work (cf. Jonsson, 33, p.11) to North Iceland. These
localities are: Hrutafjérdur, Prestsbakki, Kolbeinsa, Skalholtsvik,
Kollafjardarnes, Broddanes and Grimsey in Hunafldi.

RHODOPHYCE#.
BANGIOIDE#.
Fam. Bangiacee.

Bangia fuscopurpurea (Dillw.) Lyngb., K. Roseny., 61, p. 831.
Exicel: ~Neicel SW. Jcel..S. leek:

Porphyra umbilicalis (L.) J. Ag., K. Rosenv., 61, p. 830; P. laciniata
Strémf., 70, p. 34.

Common in all parts of the coast of Iceland.

Porphyra miniata (Ag.) Ag., K. Rosenv., 61, p. 826; Diploderma m.,
D. tenuissimum, D. amplissimum Strémf., 70, p. 33.
Found in all parts of the coast.

Porphyropsis coccinea (J. Ag.) K. Roseny., 65, p. 69; Porphyra
coccinea JOénsson, 31.
SW. Icel.: Reykjavik, S. Icel.

Conchocelis rosea Batters.
Found in all parts of the coast.

FLORIDEZ.

Fam. Helminthocladiacee.

Chantransia virgatula (Harv.) Thur., K. Rosenv., 61, p. 824.
NW. icel., SW. Icel.

Chantransia secundata (Lyngb.) Thur., K. Rosenv., 61, p. 824.
Found in all parts of the coast.

Chantransia Alarize H. Jonsson, 31.
SW. Icel., S. Icel.: Eyrarbakki.

Chantransia microscopica (Naeg.) Fosl. On Cladophora gracilis in
the littoral zone. Thallus has long hairs. Published in Bérgesen
and Jonsson, 14.

N. Icel.: Kolbeinsa.

The specimens mentioned under this name belong most probably
to another species of Chantransia with a unicellular base.

MARINE ALGAL VEGETATION 7

Fam. Gigartinacee.

Chondrus crispus (L.) Stackh., Stromf., 70, p. 31.

NW. Icel. (cast ashore), SW. Icel., S. Icel.

Gigartina mamillosa (Good. et Wood.) J.Ag., Strémf., 70, p. 31.
Found in all parts of the coast, common in SW. Icel. and S. Icel.
Ahnfeltia plicata (Huds.) Fries, Strémf., 70, p. 31.

Cast ashore on N. Icel. and NW. Icel.. common in SW. Icel. and S. Icel.

a ayes : SSS SSS -
SS Nioy ids iT ys Loacmad uty 56
LS San e Horndjarg 4q Crimsey eae
< aera Melrakka= Langanes
2 Op yy 2 sljetta
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SN , pnp Z ;
ay z
wi wn ey \
Ki Be GS : ) Huna ‘ o
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Zz,
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Latrabjarg Z Brodie) ® 9) j ee |
ce ee yore pe)
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nm Breidif}. 33
ye,
Loa ai an or re
ep Stykkisholnurs Sa res fy |
Ce Sa. J TY barf |
a}
é ong ae Magee 2 Wig i! sD oe)
@ : |
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tao) Maxat lon
a : gor ? Lfyst whore
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rykjavik
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Njarbvik ws
« Eyrarbakhy, p
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ped a K XK
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ob 0 So Kilometer ibe
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Fig. 1.

Phyllophora Brodizi (Turn.) J. Ag. *inferrupta (Grev.) K. Rosenv.,
GL, p21.

E. Icel., NW. Icel.

Phyllophora membranifolia (Good. et Wood.) J.Ag., Stromf., 70, p. 30.
SW. Icel., S. Icel.

Actinococcus subcutaneus (Lyngb.) K. Rosenv., 61, p. 822.
E. Icel., NW. Icel.

Ceratocolax Hartzii K. Rosenv., 62, p. 34.
NW. Icel.

Fam. Rhodophyllidacee.
Cystoclonium purpurascens (Huds.) Kiitz., Strémf., 70, p. 30.
N. Icel., NW. Icel. (cast ashore), common in SW. Icel. and S. Icel.

8 H. JONSSON

Turnerella Pennyi (Harv.) Schmitz, K. Rosenv., 62, p. 29.
E. Icel., N. Icel.

Euthora cristata (L.) J. Ag., Strémf., 70, p. 27.
Common around the coast of Iceland.

Rhodophyllis dichotoma (Lepech.) Gobi, Strémf., 70, p. 26.

Common around the coast of Iceland.

Fam. Rhodymeniacee.
Rhodymenia palmata (L.) Grev., Kjellman, 36, p. 147; Strémfelt,
70, p.27; R. pertusa Strémf., 70, p. 28.
Very common around the coast of Iceland.

Lomentaria clavellosa (Turn.) Gaill.; Le Jol., Liste des Algues mar.
de Cherb., p. 132, var. sedifolia Ag.
S. Icel.

Lomentaria rosea (Harv.) Thur., Le Jol., Liste des Alg. mar. de
Cherb., p. 131, Fig. Harv. Phyc. Brit., T. 358 and 301.
S. Icel.

Plocamium coccineum (Huds.) Lyngb., Strémf:, 70, p. 27.
S. Icel.

Halosaccion ramentaceum (L.) J. Ag., Kjellm., 36, p. 153; Strémf.,
70, p. 29; H. scopula Strémf., 70.

Common around the coast of Iceland.

Fam. Delesseriacez.

Delesseria alata (Huds.) Lam., Strémf., 70, p. 24.
SW. Icel., S. Icel. 3

Delesseria Baerii (Post. et Rupr.), J. Ag.: *corymbosa (J. Ag.) K.
Rosenv., 61, p. 806.

There is a specimen of this plant in the herbarium of the Botanical
Museum in Copenhagen; it is labelled “Islandia d. Morck.”

Delesseria sinuosa (Good. et Wood.) Lam., Strémf., 70, p. 24.
Common around Iceland.

Delesseria sangvinea (L.) Lam.; Hydrolapathum s. Strémf., 70, p. 26.
E. Icel.; rather common in SW. Icel. and S. Icel.

Fam. Bonnemaisoniacez.

Bonnemaisonia asparagoides (Wood.) C. Ag.

In the herbarium of the Botanical Museum in Copenhagen there
are three specimens of this species, said to have been collected in Ice-

MARINE ALGAL VEGETATION 9

land. On one of the labels is written “misit Faber.” In Flora Danica T.
2579 a specimen of this plant is figured, regarding which Liebmann
writes: “ad littora Islandiz pr. Reykjavik legit beatus Faber, cujus spe-
cimina mecum communicavit cl. Hofman-Bang.”

Fam. Rhodomelacee.
Pterosiphonia parasitica (Huds.) Falkenberg, Die Rhodomelaceen
des Golfes von Neapel. Polysiphonia p. Kjellman, 36, p. 117; H.
Jonsson, 31, p. 142.
S. Icel.

Polysiphonia urceolata (Lightf.) Grev., Strémf., 70, p. 24.
Common around Iceland.

Polysiphonia fastigiata (Roth) Grev., Strémf., 70, p. 24.
NW. Iceland.; common in SW. Icel. and S. Icel.

Polysiphonia arctica J. Ag., K. Rosenv., 61, p. 800.
E. Icel., N. Icel. and NW. Icel. common; SW. Icel.

Polysiphonia nigrescens (Huds.) Harv., Kjellman, 36, p. 126.
N. Icel., SW. Icel.

Rhodomela lycopodioides (L.) Ag., Strémf., 70, p. 23.
Common around Iceland. -
Odonthalia dentata (L.) Lyngb., Strémf., 70, p. 23.

Common around Iceland.

Fam. Ceramiacez.
Callithamnion Arbuscula (Dillw.) Lyngb., Strémf., 70, p. 32.
Rather common in SW. Icel. and S. Icel.
Callithamnion scopulorum C. Ag., Spec. Alg. (2), p. 176.
SW. leel’ S: Icel:
| Plumaria elegans (Bonnem.) Schmitz, Syst. Uebersicht der bisher
bekannten Gattungen der Florideen, Flora oder allgem. bot. Zeit.,
1889; Ptilota e. Kjellman, 36, p. 172.
SW. leel-, “S: Icel:
Ptilota plumosa (L.) Ag., Strémf., 70, p. 32.
N. Icel.; common in NW. Icel., SW. Icel. and S. Icel.
Ptilota pectinata (Gunn.) Kjellm., Strémf., 70, p. 32.
Common in E. Icel., N. Icel. and NW. Icel.; rather rare in SW. Icel.
Antithamnion Plumula (Ellis) Thur. 6 boreale Gobi, K. Rosenvy.,
61, p. 787. A. boreale Strémf., 70, p. 32.
E. Icel., N. Icel., NW. Icel., SW. Icel.

10 H. JONSSON

Antithamnion floccosum (Mill.) Kleen, Strémf., 70, p. 32.
E. Icel., SW-tcel:;'S. teel:

Ceramium acanthonotum Carm., Kjelim., 36, p. 171.
SWtcel:S: Teel:

Ceramium Deslongchampii Chauv., Petersen, 57, p. 108; Ceramium
rubrum ex pte. Jénsson, 31.
SW. Icel.: Reykjavik (L. Kolderup Rosenvinge, °/¢ 1886).

Ceramium fruticulosum Kiitz., Petersen, 57, p. 108.
SW. Icel.: Seltjarnarnes (Helgi Jénsson, 78/3 1907).

Ceramium circinnatum Ag., Petersen, 57, p. 111; Ceramium rubrum
ex pte. Jonsson, 31.

SW. Icel.: Stykkishélmur (Helgi Jénsson, 1!°/6 1897), Skerjafjérdur
(Helgi Jénsson, !°/7 1905).

Ceramium arborescens J. Agardh, Petersen, 57, p. 112; Ceramium
rubrum ex pte. Jénsson, 31.

N. Icel.: Hrisey (Helgi Jénsson, ?/7 1898); NW. Icel.: Latravik in Adal-
vik (C. H. Ostenfeld, °/7 1896); SW.Icel.: Reykjavik (L. Kolderup Rosen-
vinge, °/6 1886). |

Ceramium atlanticum Petersen, 57, p. 112; Ceramium rubrum ex
pte Jonsson, 31.

SW. Icel.: Grétta (Helgi Jonsson, 17/6 1908), Hafnarfjérdur (Hjalmar
Jensen, ‘/5 1890); S. Icel.: Stadur (C. H. Ostenfeld, 17/6 1896), Eyrarbakki
(Helgi Jonsson, 34/5 1897), Vestmannaeyjar (Helgi Jonsson, 1/5 1897).

Ceramium rubrum (Huds.) Agardh, Petersen, 57, p. 113; Jénsson,
Jl, ex pte.
Nilicela NW. Teel: SW. dcels S-lcel:

Rhodochorton Rothii (Turt.) Naeg., K. Rosenv., 61, p. 791.
E. Icel., N. Icel., NW. Icel., SW. Icel. (common), S. Icel.

Rhodochorton repens H. Jonsson, 31.
S. Icel.

Rhodochorton minutum Suhr. Descr. in Reinke’s Atlas (59), Fig.
Reinke’s Atlas T. 40. |
SW. Icel.

Rhodochorton penicilliforme (Kjellm.) K. Rosenvy., Les Algues ma-
rines du Groenland in Ann. Sc. nat., 7° Sér., XIX.
E. Icel., N. Icel., NW. Icel., SW. Icel.

MARINE ALGAL VEGETATION 11

Rhodochorton membranaceum Magnus, K. Rosenv., 61, p. 794; P.
Kuckuck, Beitrage zur Kenntniss der Meeresalgen, 1897.
E. Icel., N. Icel., NW. Icel., SW. Icel.

Fam. Dumontiacee.
Dumontia filiformis (Fl. Dan.) Grev., Stroémf., 70, p. 30.
E. Icel., SW. Icel. (rather common), S. Icel.
Dilsea edulis Stackh., Sarcophyllis edulis Kjellm., 36, p. 152.
SW. Icel.

Fam. Squamariacee.
Petrocelis Hennedyi (Harv.) Batters, A list of the Marine Algze
‘of Berwick-on-T weed.
— N. Icel.; Hraunakrokur (O. Davidsson), NW. Icel., SW. Icel., S. Icel.

Cruoria arctica Schmitz, K. Rosenv., 61, p. 784.
SW. Icel.

Cruoria pellita (Lyngb.) Fries, Kjellm., 36, p. 142.
SW. Icel., S. Icel.: Eyrarbakki.

Peyssonellia Rosenvingii Schmitz, K. Rosenv., 61, p. 782; Hzema-
tostagon balanicola Strémf., 70, p. 25?
Petcel. N.tcel, NW. icel.. SW..Jcel,

Rhododermis parasitica Batters, A list of the Marine Alge of
Berwick-on-T weed.
NW. Icel., SW: Icel., S. Icel.

Fam. Corallinacez.

Lithothamnion glaciale Kjellm., Strémf., 70, p. 18.
H, leet, N. Icel.;: SW. Icel.

Lithothamnion Ungeri Kjellm., 36, p. 91 excl. syn.; L. intermedium
Strémf., 70, p. 19. |
F_tcel., N: Icel. NW. Icel.

Lithothamnion tophiforme Unger, Foslie, The Norwegian forms
of Lithothamnion, 1895, p.119; L. soriferum Strémf., 70, p. 18.
E. Icel., N. Icel., SW. Icel.: Hvalfj6rdur (Horring), S. Icel.

Lithothamnion flavescens Kjellm., 36, p. 98.
E. Icel.

Lithothamnion foecundum Kjellm., 36, p. 99.
Bm Acel N: Teel.

12 H. JONSSON

Lithothamnion leve (Strémf.) Foslie, List of species of the Litho-
thamnia p.7; Lithophyllum leve Strémf., 70, p. 21.
E. Icel.; Nv Iecel.,. NW. Icel., SW Teeli;.S.iicel

. Lithothamnion Lenormandi (Aresch.) Foslie, The Norwegian forms
of Lithothamnion, 1895, p. 150.
SW. Icel.

Phymatolithon polymorphum (L.) Foslie, List of species of the
Lithothamnia p.8; Lithothamnion polymorphum Strémf., 70, p. 19.
Setcel: |

Clathromorphum compactum (Kjellm.) Foslie, Lithothamnion com-
pactum Kjellm., 36, p. 101; Clathromorphum circumscriptum (Strémf.)
Fosl., Lithothamnion circumscriptum Strémf., 70, p. 20.

In all parts of the coast.

Lithophyllum Crouani Fosl., List of species of the Lithothamnia,
p10:
N. Icel., NW. Icel., S. Icel.: Eyrarbakki.

Dermatolithon macrocarpum (Ros.) Fosl., Revised systematical survey
of the Melobesiez, p. 21; Melobesia macrocarpa Strémf., 70, p. 23.
SW. Icel., S. Icel.

Corallina officinalis L., Stromf., 70, p. 18.
N. Icel., NW. Icel., SW. Icel., S. Icel.

Hildenbrandia rosea Kutz, Stromf., 70, p. 24.
Common around the coast of Iceland.

PH OPHYCE.

Fam. Myrionemacee.
Lithoderma fatiscens Aresch., emend. Kuck., Bemerk. I (47), p. 238.
E. Icel., N. Icel., NW. Icel., SW. Icel.

Petroderma maculiforme (Wollny) Kuck., Bemerk. II (47), p. 382.
N. Icel.

Ralfsia ovata K. Rosenv., 61, p. 900; 62, p. 94.
N. Icel.: Husavik (Ove Paulsen), Prestsbakki; SW. Icel.

Ralfsia clavata (Carm.) Farl., Mar. Alg., p. 88; Reinke (59) Atlas
T.5 and 6, figs. 14—20; Stragularia adherens Strémf., 70, p. 49, T.
II, figs. 13—15.

E. Icel., N. Icel., NW. Icel., SW. Icel.

MARINE ALGAL VEGETATION 13

Ralfsia verrucosa (Aresch.) J. Ag., Reinke (59), Atlas T.5 and 6,
figs. 1—13.

FE teels N: Teel SW: Icel.

Ralfsia deusta (Ag.) J. Ag., K. Rosenv., 61, p. 898.

E. Icel., N. Icel., SW. Icel., S. Icel.

Myrionema vulgare Thuret, Sauvageau, 66, p. 185.

N: Icel., SW. Icel.

Myrionema Corunne Sauvag., 66, p. 237.

S. Icel.

Myrionema globosum (Rke) Fosl., New or critical Norw. Alge, p.
17; Ascocyclus globosus Rke, 58, p. 46; Atlas (59) T. 17; aches
globosus K. Rosenv., 62, p. 86, figs. 19—20.

E. Icel., N. Icel., NW. Icel., SW. Icel.

Myrionema feréense Borgs., 13, p. 424.

SW. Icel.

Myrionema Laminarie (K. Roseny.), Dermatocelis Laminariz K.
Rosenv., 62, p. 89, fig. 21.

SW. Icel. 7

Ascocyclus islandicus H. Jonsson, 31, p. 149.

N. Icel.

Probably this species will prove to be identical with A. sph@rophorus
Sauv., cf. J6nsson, 31, p. 151 and Kylin.! The last-named author
writes that A. islandicus without doubt is identical with A. spherophorus,
but he gives no particulars as to the chromatophores of the last-named
species, I therefore must still regard the Icelandic plant as a distinct
species.

Fam. Ectocarpacee.

Microsyphar Polysiphonie Kuck., Beitrage (48) p. 29.

NW. Icel., SW. Icel.

Streblonema ecidioides K. Rosenv., 61, p. 894; 62, p. 80; Phyco-
celis ecidioides Kuck., Bemerk. I (57), p. 234.

E. Icel., N. Icel., SW. Icel.

Streblonema Stilophore Cr. var. cespitosa K. Rosenv., 61, p. 892.

Found in all parts of the coast.

Pylaiella littoralis (L.) Kjellm.; Ectocarpus littoralis, Kuck., 48,
p. 7; Rosenv., 61, p. 881; Pylaiella littoralis, Pylaiella varia Kjellm.,
do, p. 83.

Common around the coast of Iceland.

1 Harald Kylin, Zur Kenntnis der Algenflora der Norwegischen Westkiste, «

Arkiv foér Botanik, Bd. 10, No. 1, 1910.

14 ; H. JONSSON

Ectocarpus tomentosoides Farl., New or imperfectly known Algze
of U.S., reprint from Bull. Torr. Bot. Club, Vol. XVI, 1889, p. 11,
T. 87, fig. 4; K. Rosenv., 61, p. 180; Gran, En norsk form af Ectoce.
tomentosoides Farl., Christiania Vidensk. Selsk. Forhandl. for 1883,
No. 17; Kuckuck, Ueber Polymorphie bei einigen Phzosporeen in
Festschrift fiir Schwendener, p. 370, figs. 5—7.

E. Icel., N. Icel., NW. Icel.; common in SW Icel. and S. Icel. .

Ectocarpus tomentosus (Huds.) Lyngb., Hydr. Dan. (51) p. 132;
Kjellman, 35, p. 73. |

SW. Icel., S. Icel.

Ectocarpus confervoides (Roth) Le Jol., Kuck., 48, p. 19; Kjell-
man, 35, p.77, ex pte.; K. Rosenv., 61, p. 883, ex pte.
Found in all parts of the coast.

Ectocarpus siliculosus (Huds.) Lyngb., Hydr. Dan. (51) p. 131;
Kjellman, 35, p. 78; Kuck. 48, p. 15.
N. Icel., SW. Icel.

Ectocarpus penicillatus (Ag.) Kjellm., 35, p. 76; E. confervoides
f. penicillata Kjellman, 39, p. 79.
E. Icel., N. Icel., SW. Icel.

Ectocarpus fasciculatus (Griff.) Harv., Kjellm. 35, p. 76.
SW. Teel:;-S: Icel.

Ectocarpus Hinksiz Harv., Manual, p. 59; Phyc. Brit., T. 22;
Sauvageau, Observations relatives 4 la sexualité des Phéosporées
(Journal de Botanique, 1896).

S. Icel.

Fam. Elachistacez.
Leptonema fasciculatum Rke, 58, p. 50; var. subcylindrica K.
Rosenv., 61, p. 879.
N. Icel., NW. Icel., SW. Icel.

Elachista fucicola (Vell.) Aresch., emend. K. Rosenv., 61, p. 878;
E. fucicola Strémf., 70, p.49. a typica is the most common, / lu-
brica (Rupr.) K. Rosenv. is rather common.

In all parts of the coast.

Fam. Sphacelariacee.

Sphacelaria britannica Sauvag., 67, p. 50.
N. Icel., SW. Icel., S. Icel.

MARINE ALGAL VEGETATION £5

Sphacelaria radicans Harv., Sauvag., 67, p. 27, fig. 14; Reinke, 60,
a AT hie. 15, Kuek., Bemerk. 1) (47), p: 229, fig. 4.
Bowleels Neteel: SW. lIcel), Si Icel.

Sphacelaria olivacea Pringsh., emend. Sauvag., 67, p. 54.

NW. Icel., SW. Icel., S. Icel. .

Chetopteris plumosa (Lyngb.) Ktitz., Sauvag., 67, p. 44; Strémf.,
70, p.52; K. Rosenv., 61, p. 903; Reinke, 59, Atlas T. 49—50.

E. Icel., N. Icel., NW. Icel., SW. Icel.

Fam. Punctariaceez.
Omphalophyllum ulvaceum K. Rosenv., 61, p. 872, fig. 19.
etcel,
Punctaria plantaginea (Roth) Grev., K. Rosenv., 61, p. 871; 62, p.
71; Strémf., 70, p. 50.
Ea tcel,N. icel.;.NW. Icel.

Litosiphon filiformis (Rke), Pogotrichum filiforme Rke (59), Atlas,
p. 62, T. 41, figs. 13—25; K. Rosenv., 61, p. 869; Kuck., Ueber Poly-
morphie bei einigen Phaeosporeen, Festschrift fiir Schwendener,
p. 360.

Ealtcel. No icel:, SW. Icel.;\'S:Icel:

Isthmoplea sphezrophora (Harv.) Kjellm., 36, p. 276; Reinke (59),
Atlas: T. 30; Pylaiella curta Foslie, Nye havsalger, in Troms6é Mu-
seums Aarshefter, X, 1887, p. 181; Kjellman, 35, p. 85; Fosliea curta
Rke, Atlas, p. 45.

melcelewN W..lcel..15 W. Icel., S_ lcel:

Stictyosiphon tortilis (Rupr.) Rke, Atlas, T. 31--32; K. Rosenv.,
61, p. 868; Phloeospora tortilis Stroémf., 70, p. 51; Phloeospora sub-
articulata Kjellman, 39, p. 78.

BY iceln aN, ice! 99N W: Icel.,, SW. Icel

Phzostroma pustulosum Kuckuck, Ueber einige neue Phezosporeen
d. westl. Ostsee, Bot. Zeit. 1895, p. 182, T. VII; K. Rosenv., 62, p.
68, fig. 15.

E. Icel., NW. Icel., SW. Icel.

Scytosiphon Lomentaria (Lyngb.) J. Ag., K. Rosenv., 61, p. 863;
62, p.62; Strémf., 70, p. 50.

In all parts of the coast.

Phyllitis zosterifolia Rke, 58, p. 61; K. Rosenv., 61, p. 862.
FE. Icel., NW: Icel., SW. Icel.,. S. Icel.

16 H. JONSSON

Phyllitis fascia (O. F. Mill.) Kiitz., K. Rosenv., 61, p. 862.
Gathered in all parts of the coast.

Fam. Dictyosiphonacez.
Coilodesme bulligera Stromf., 70, p. 48, T. II, figs. 9—12; K. Ro-
senv., 61, p. 862; 62, p. 61, fig. 13.
E. Icel., NW. Icel., SW. Icel.

Dictyosiphon Ekmani Aresch., Obs. phyc. 3 (7), p. 33.
SW. Icel.

Dictyosiphon Mesogloia Aresch., Obs. phyc. 3 (7); Reinke, 58,
p. 64.
N. Icel.

Dictyosiphon Chordaria Aresch., Obs. phyc. 3 (7); Reinke, 58, p.
63; K. Rosenv., 61, p. 861; Coilonema Chordaria Strémf., 70, p. 51.
E. Icel., SW. Icel.

Dictyosiphon corymbosus Kjellm., 36, p. 267; Strémfelt, 70, p. 51.

N. Icel.

Dictyosiphon hippuroides (Lyngb.) Kiitz.; Kjellm., 36, p. 268; Strém-
felt, 70, p. 51.

N. Icel., NW. Icel., SW. Icel., S. Icel.

Dictyosiphon foeniculaceus (Huds.) Grey., Kjellman, 36, p: 269;

K. Rosenv., 61, p. 859; Strémf., 70, p. 52.
E. Icel., N. Icel., NW. Icel., SW. Icel.

Fam. Desmarestiacee.
Desmarestia viridis (Mull.) Lam., K. Rosenv., 61, p. 859; Dichloria
viridis Strémf., 70, p. 51.
Common around the coast of Iceland.
Desmarestia aculeata (L.) Lam., Strémf., 70, p. 51; K. Rosenv.,
61, p. $57.

Common everywhere along the coast.

Desmarestia ligulata (Lightf.) Lam.
S. Icel.: Vestmannaeyjar (Ove Paulsen).

Fam. Chordariacez.
Castagnea virescens (Carm.) Thur., K. Rosenv., 62, p. 58; Eudesme
virescens Stromf., 70, p. 47.
E. Icel., N. Icel., SW. Icel.

MARINE ALGAL VEGETATION 17

Leathesia difformis (L.) Aresch., Kjellm., 36, p. 252.

N. Icel., SW. Icel.

Chordaria flagelliformis (Miull.) Ag., Strémf., 70, p.47; K. Rosenv.,
61, p. 854.

Common everywhere along the coast.

Fam. Chordacee.
Chorda tomentosa Lyngb., Hydrophytologia Danica, p. 74; K.
Rosenv., 61, p. 854.
E. Icel., N. Icel., SW. Icel.
Chorda Filum (L.) Stackh., K. Rosenv., 61, p. 853; Strémf., 70, p. 47.
Be eel., \N. Icel., NW. Icel.,. SW. Icel.

Fam. Laminariacee.
Saccorrhiza dermatodea (De la Pyl.) J. Ag.; K. Rosenv., 61, p. 850;
Phyllaria lorea Stroémf., 70, p. 42.
E. Icel., N. Icel., NW. Icel., SW. Icel.
Laminaria saccharina (L.) Lam., Kjellman, 36, p. 229; 35, p. 24;
Strémf., 70, p. 42.
f. typica ;
f. linearis J. Ag., Kjellman 36, p. 229; 35, p. 25; Strémf., 70,
p. 42; Borgesen, 13, p. 451, fig. 85;
f. latifolia Kjellm., 35, p. 26; Laminaria saccharina f. latis-
sima Kjellm., 36, p. 230; Strémf., 70, p. 43?
This species is common everywhere along the coast, especially the

principal form; f. linearis is rarer and f. latifolia is only met with in E.
Icel. and NW. Icel. where it occurs gregariously.

Laminaria feroensis Borges., 13, p. 454.
E. Icel., N. Icel.
Laminaria nigripes J. Ag., emend. K. Rosenv., 61, p. 842.
6 atrofulva (J. Ag.) K. Rosenv. (I. c.); Laminaria discolor, La-
minaria nigripes f. oblonga Strémf., 70, pp. 483—44.
Ee. Icel.
Laminaria digitata (L.) Lam., Kjellman, 36, p. 240; 35, p. 22; Strémf.,
70, p. 45.
f. genuina Le Jol. 49; Kjellman, 35, p. 23;
f. stenophylla Harv. Phyc. Brit., T. 338; Laminaria stenophylla
Strémf., 70, p. 45; J. Ag. De Lam., p. 18; Kjellm., 35, p. 24;
f. cucullata Le Jol., 49.

F. genuina is common everywhere; f. sfenophylla: E. Icel., SW. Icel.,
S. Icel.; f. cucullata: E. Icel., NW. Icel.

The Botany of Iceland. I. D)

|

18 H. JONSSON

Laminaria hyperborea (Gunn.) Foslie, 20, p.42; Strémf., 70, p. 44;
Laminaria Cloustoni Le Jol., 49, p.577; fig., Fosl., 20, T.1.

E. Icel., N. Icel., NW. Icel.; common in SW. Icel. and S. Icel.

Alaria Pylaii (Bory) J. Ag., emend. K. Rosenv., 61, p. 838; Alaria
Pylaii and Alaria membranifolia Strémf., 70, p. 39.

f. typica K. Rosenv.;
f. membranacea (J. Ag.) K. Rosenvy.

Common everywhere along the coast.

Alaria esculenta (L.) Grev., Kjellm., 36, p. 212; 35, p. 19; Alaria
esculenta, Alaria linearis and Alaria flagellaris Strémf., 70, pp. 38—
41; A. flagellaris K. Rosenv., 62, p. 49. :

f. australis Kjellm.;
f. fasciculata Stromf.;
f. pinnata (Gunn.) Kjellm.

This species is exceedingly common everywhere along the coast.

Fam. Fucacee.

Fucus spiralis L., Kjellm., 36, p. 202; Strémf., 70, p. 35; Bdorge-

sen, 13, p.472; Fucus Areschougii Kjellm., 35, p. 11.
f. typica;
f. borealis Kjellm.

Ey icel N. icel- SW. tcel.s.icel:

Fucus inflatus L., M. Vahl, Fl. Danica (30), T. 1127; Foslie, Krit.
Fortegnelse, Troms6 Mus. Aarshefter, IX, p. 109; Kjellm., 35, p. 11;
K. Rosenv., 61, p. 834; Borgesen, 13, p. 465; Fucus evanescens Strémf.,
70, p. 35; F. edentatus, F. furcatus and F. evanescens J. Ag., 3, p.
40; F.furcatus Kleen, 43, p. 29; F.edentatus De la Pyl., 15, p. 84.

f. typica.
F.furcatus Kleen ex pte.; F.evanescens auct. ex pte.;
F. edentatus De la Pyl.;
fig. Flora Danica (30) T. 1127; Borgesen, 13, figs. 90 and 91.
f. evanescens (C. Ag.)
F. evanescens C. Ag., Sp. p. 92 et auct. partim.
f. linearis (Huds.) K. Rosenv., 61, p. 834; F. linearis Hudson
Flora anglica London 1762, Oeder Flora Danica (30) T. 351.
f. eacposita.
F. distichus Lyngb. Hydr. Dan. (51) p. 6, exclus. syn.;
F. distichus a, robustior J. Ag. 3, p. 37, Kjellman 36, p. 210;
F. inflatus f. disticha Borgesen, 13, p. 465.
This species is common everywhere along the coast.

MARINE ALGAL VEGETATION 19

Fucus serratus L., Kjellm., 36, p. 196.

SW. Icel., S. Icel.

Fucus vesiculosus L., Kjellm., 36, p. 198; Strémf., 70, p. 34.
f. typica, fig. Harv. Phyc. Brit. T. 204.
f. turgida Kjellm.
f. spherocarpa J. Ag.

This species is common everywhere.

Pelvetia canaliculata (L.) Dec. et Thur., Strémf., 70, p. 38.
SW. Icel., S. Icel.

Ascophyllum nodosum (L.) Le Jol., K. Rosenv., 61, p. 832; Ozo-
thallia nodosa Strémf., 70, p. 34.
Common along the coast.

CHLOROPHYCE.

Fam. Protococcacee.
Chlorochytrium Cohnii Wright, K. Rosenv., 61, p. 963.
SW. Icel. |

Chlorochytrium inclusum Kjellm., 36, p. 320, T. 31, figs. 8—17;
K. Rosenv., 61, p. 963; 62, p. 119.
Reteel, N. Icel., NW. Icel., SW. tcel.

Chlorochytrium dermatocolax Rke, 58, p. 88; K. Rosenv., 61, p.
964; Svedelius, 71, p. 72.
Ne lcels,. SW: Icel.

Chlorochytrium Schmitzii K. Rosenv., 61, p. 964; 62, p.119.
SW. Icel.

Codiolum Petrocelidis Kuck., Bemerk. (47), p. 259, fig. 27.
SW. Icel.

Codiolum gregarium Al. Braun, Algarum unicellularum genera
nova et minus cognita, Lipsiz, 1855, p.19; Boérgesen, 13, p. 517.

E. Icel. |

Codiolum pusillum (Lyngb.) Kjellm., Bérgesen, 13, p. 518; Vau-
cheria pusilla Lyngb. Hydr. Dan. 51, p. 72, T. 22.

N. Icel. |

Fam. Ulvacee.
Percursaria percursa (Ag.) K. Rosenv., 61, p. 963.

SW. Icel.
2%

20 H. JONSSON

Enteromorpha aureola (Ag.) Ktitz., Tab. phyc., Vol. VI, T. 40, II;
Ulva aureola Ag. Ic. alg. europ. (1), T. 29; Capsosiphon aureolus Gobi;
Ilea fulvescens J. Ag., Ulvacez p.114; ? Solenia fulvescens Ag., 2, p.
420; Enteromorpha quaternaria Ahlner in Wittr. et Nordstedt Alg.
exsicc., Nos. 138 and 139.

N. Icel.

Enteromorpha Linza (L.) J. Ag., Ulva enteromorpha a, lanceolata
Le Jol., 50, p. 42. |

SW. Icel., S. Icel.

Enteromorpha intestinalis (L.) Link., emend. K. Rosenvy., 61, p. 957;
Bérgesen, 13, p. 487.

f. genuina K. Rosenv. I. c. p. 957;
Enteromorpha intestinalis Strémf., 70, p. 52.

f. micrococca (Kiitz.) K. Rosenv. 1. c. p. 957.

f. compressa (L.) K. Roseny. 1. c. p. 958;
Enteromorpha compressa f. typica and
E. complanata f. subsimplex Strémf., 70, p. 53.

f. minima (Naeg.) K. Rosenv., |. c. p. 959;
Enteromorpha minima Strémf., 70, p. 53.

f. prolifera (O. F. Miller) Bérgesen, 13, p. 490.
Enteromorpha prolifera K. Rosenv., 61, p. 960.

This species is common everywhere along the coast.

Enteromorpha clathrata (Roth) Grev., Kjellm., 36, p. 287; Ulva
clathrata Le Jol., 50, p. 48 (partim) ; Enteromorpha compressa f. race-
mosa Strémf., 70, p. 53.

E: Icel., N. Icel., SW. Icel., S. Icel.

Monostroma groenlandicum J. Ag., K. Rosenv., 61, p. 954, fig. 53.
E. Icel., N. Icel., NW. Icel:

Monostroma Grevillei (Thur.) Wittr., emend. K. Rosenv., 61, p. 946.

var. typica K. Rosenv. |. c.
Monostroma Grevillei Wittr., 76, p. 57; Strémf. 70, p. 54
partim (e specim.).

var. arctica (Wittr.) K. Rosenv. l. c.
Monostroma arcticum Wittr., 76, p. 44; Monostianet latis-
simum Strémf., 70, p. 54.

var. intestiniformis K. Rosenv. 1. c.
Enteromorpha intestinalis Strémf., 70, p. 58 partim (e spec.).

Var. typica and var. arctica are common along the coast; var. inte-
stiniformis: E. Icel., SW. Icel.

MARINE ALGAL VEGETATION 21

Monostroma undulatum Wittr. 76, p. 46, T. III, fig. 9; K. Rosenv.,
61, p. 945; Monostroma Grevillei Strémf., 70, p. 54 partim (e specim.).

In all parts of the coast.

Monostroma fuscum (Post. et Rupr.) Wittr., emend. K. Rosenv.,
61, p. 940; M. Blyttii, Strémf. 70, p. 54.

f. typica is common along the coast; f. grandis.: E. Icel., N. Icel.

Ulva Lactuca L., K. Rosenv. 61, p. 839; Strémf., 70, p. 54.
N. Icel., NW. Icel., SW. Icel., S. Icel.

Fam. Prasiolacez.
Prasiola polyrrhiza (K. Rosenv.).
Gayella polyrhiza K. Rosenv., 61, p. 936;
Prasiola crispa subsp. marina Bérgesen, 13, p. 482;

Prasiola crispa f. submarina Wille, 73, p. 13.
SW. Icel., S. Icel.

Prasiola furfuracea (Mert.) Menegh. Imhauser, 29, p. 266; Foslie
Contrib., I, p. 127; Borgesen, 13, p. 486.
E. Icel., N. Icel., SW. Icel.

Prasiola stipitata Suhr; Imh4user, 29, p. 272; Kjellman, 36, p. 303.
leek: N: leel:, SW. Icel.,.S.Icel.

Fam. Ulothricacee.

Ulothrix consociata Wille, 73, p. 25.
var. islandica H. Jénss.
N. Icel.

Ulothrix subflaccida Wille, 73, p. 29.
E. Icel., N. Icel.

Ulothrix pseudoflacca Wille, 73, p. 22, T. II, figs. 64—81.
E. Icel., SW. Icel., S. Icel.

Ulothrix flacca (Dillw.) Thur., K. Rosenv., 61, p. 935, fig. 44; Wille,
73, p.18, T. I—II, figs. 54—63.

Common around the coast of Iceland.

Fam. Cheetophoracee.
Pseudendoclonium submarinum Wille, 73, p. 29, T. III, figs. 101—134.
_E. Icel.

Entoderma Wittrockii (Wille) Lagerh., K. Rosenv., 61, p. 934.
N. Icel., SW. Icel., S. Icel.

22 H. JONSSON

Acrochete parasitica Oltm. Bot. Zeit. 1894, p. 208; K. Rosenv., 62,
p. 114.
SW. Icel.

Acrochete repens Pringsh., Beitrage p. 2, T. II; Huber, 28, p. 306.

NW. Icel.

Bolbocoleon piliferum Pringsh., Beitrage p. 2, T. Il; Huber, 28,
p. 308, pl. 13, figs. 8—12.

E. Icel., N. Icel., NW. Icel.

Fam. Mycoideacee.

Ulvella fucicola K. Rosenv., 61, p. 926, fig. 40. Pseudopringsheimia
fucicola (Rosenv.) Wille in Engler u. Prantl: Die natirlichen Pflanzen-
familien, Nachtrage zu I. Theil, Abtheil 2, p. 89. :

E. Icel., N. Icel., SW. Icel., S. Icel.

Pringsheimia scutata Rke, 58, p.81, Atlas T. 25.
NW. Icel., SW. Icel.

Ochlochete ferox Huber, 28, p. 291, T.X; K. Rosenv. 61, p. 931,
fig. 41.
N. Icel.

Fam. Cladophoracee.
Urospora mirabilis Aresch., K. Rosenv., 61, p. 918, fig. 35; 62, p. 106.

Common along the coast.

Urospora Hartzii K. Rosenv., 61, p. 922, fig. 38.
E. Tcel.,, SW. Icel: *S: Icel:

Urospora Wormskioldii (Mert.) K. Rosenv., 61, p. 920, fig. 36.

In all parts of the coast.

Cheztomorpha tortuosa (Dillw.) Kleen, K. Rosenv., 61, p. 917.
E. Icel., N. Teel; “SW.1cel.

Chetomorpha Melagonium (Web. et Mohr) Kitz., K. Rosenv., 61,
p. 917; Strémf., 70, p. 55.

Probably common along the coast of Iceland.

Rhizoclonium riparium (Roth) Harv., K. Rosenv., 61, p. 913; 62,

p. 103.
f. polyrhiza K. Rosenv., 1. c. p. 913.

f. valida Fosl., K. Rosenv., 1. c. p. 915.
f. implexa (Dillw.) K. Rosenv., I. c. p. 915.
FE. Icel., N. Icel., SW. Icel.

MARINE ALGAL VEGETATION 23

Spongomorpha vernalis (Kjellm.) Wille, Acrosiphonia vernalis
Kjeilm., 41, p. 82.
SW. Icel.

Acrosiphonia albescens Kjellm., 41, p. 55, T. IV, fig. 21; Bérgesen,
13, p. 507, fig. 103; Spongomorpha arcta Strémf., 70, p. 54, ex pte.

Common along the coast of Iceland.

Acrosiphonia incurva Kjellm. 41, p. 61.
Common along the coast.

Acrosiphonia hystrix (Strémf.) H. Jénss., 31.

f. typica H. Jénss., Spongomorpha hystrix Strémf., 70, p. 54,
Cladophora diffusa Strémf., 70, p. 55 ex pte. (e specim.);
Cladophora (Spongomorpha) arcta y hystrix K. Rosenv.,
Oke p: 907.

f. littoralis H. Jénss.

Beteel, ON» Icel;.NW:1céel., SW. Icel.

Acrosiphonia flabelliformis H. Joénss., 31.

S. Icel. :

Acrosiphonia penicilliformis (Fosl.) Kjellm., 41, p. 80 forma.

Eieteel 6.

Cladophora rupestris (L.) Kiitz., K. Rosenv., 61, p. 909; Strémf.,
70, p. 55.

N. Icel., NW. Icel., SW. Icel., S. Icel.

Cladophora hirta Kiitz., Kjellm., in Wittr. et Nordstedt Exsicc.,
No. 1041.

SW. Icel., S. Icel.

Cladophora sericea (Huds.) Aresch., 8, p. 194, forma.

Ne lee eS. tcel:, Ss Icel.

Cladophora glaucescens (Griff.) Harv., Phyc. Brit. T. 196; Le Jol.
Alg. mar. d. Cherb. Exsicc., 66.

SW. Icel.

Cladophora gracilis Kiitz., Kjellm. in Wittr. et Nordstedt Exsicc.,
No. 1040.

Em téeleN: Tcel., SW. Icel.

Fam. Gomontiacez.
Gomontia polyrrhiza (Lagerh.) Born. et Flah. sur deux nouv. gen.
d’Algues perfor. Journ. de Bot. Tom. II, 188, p. 163.
E. Icel., N. Icel., NW. Icel., SW. Icel.

24 H. JONSSON: MARINE ALGAL VEGETATION

Fam. Phyllosiphonacee.
Ostreobium Queketti Born. et Flah., Sur quelques plantes vivant
dans le test calcaire des mollusques, p. 15, pl. IX, figs. 5—8.
E. Icel., N. Icel., NW. Icel., SW. Icel.

CYANOPHYCER.

Fam. Chamesiphonacee.

Pleurocapsa amethystea K. Rosenv., 61, p. 967, var.
E. Icel., N. Icel.; common in NW. Icel., SW. Icel. and S. Icel.

Fam. Oscillatoriacee. |
Plectonema norvegicum Gomont, Bull. de la Soc. bot. de France,
tome XLVI, 1899.
N. Icel.

Phormidium autumnale (Ag.) Gomont, emend. Johs. Schmidt, 68,
pp. 348 and 410. :
E-icel:

Spirulina subsalsa Orsted, Beretning om en Excursion til Trin-
delen, Krogyers Tidskrift 3. Bd., pp. 566, 1842.
N: cel. “S: Teel.

Fam. Rivulariacee.
Calothrix scopulorum (Web. et Mohr) Ag., emend. Johs. Schmidt,
68, pp. 390 and 414.
E. Icel., N. Icel.

Rivularia atra Roth, Catalecta botanica, III, p. 340, 1806.
SW. Icel.

I]. LIFE-CONDITIONS OF THE MARINE ALGAL
VEGETATION.

1. THE NATURE OF THE COAST.

HE coast of Iceland consists partly of rock and partly of sand.

The rocky coasts are rich in algal vegetation, while the sandy
coast is most frequently a “desert.” Here and there vegetation may
be found, however, on the sandy coast, where this is not exposed
to violent movement during any length of time. The vegetation then
consists of short-lived species.

The Rocky Coast. This abounds in indentations of various
size: inlets, fjords and bays. The size of the fjords varies greatly;
for example, the largest, Faxafléi, is ten geographical miles long —
and twelve geographical miles broad, and Breidifjérdur is eighteen
geographical miles long and ten geographical miles broad. The
smaller fjords, on the other hand, are short and narrow indenta-
tions. Thus, owing to the indentations on the coast, the exposure
is apt to vary greatly. The extreme points and the outer portions
of the fjords have, as a rule, an exposed position, while in the
interior of the fjord the water is generally calm.

The rocks on the coast consist of basalt; in some places, how-
ever, tuff-coasts exist, and especially on the south coast. The fjord-
coasts of Iceland, which comprise South-west, North-west, North
and East Iceland, are mainly composed of basalt. The basalt varies
considerably but, as far as I have seen, it has no significance as
regards the distribution of the species, and no difference is seen,
for example, in the vegetation on the dolerite and the ordinary
basalt coasts. What is of prime importance to the vegetation is
not the rock itself but the nature of its surface. The surface is, as
a rule, very uneven, being eroded by water, weather and wind, and
furrowed by numerous fissures. Its nature is, therefore, such that
the alge can easily attach themselves to it.

26 H. JONSSON

The rocky coast is, as a rule, of solid rock, consisting of preglacial
basaltic lava. Postglacial basaltic lava is found, nevertheless, in some
places, as for example on Sneefellsnes. In many places, large stretches
of the coast are covered with debris (Urd) from the mountains.
Where the debris or the new lava predominates the surface is ge-
nerally very uneven, and one then finds distinct elevations with
- large and small depressions interposed; such a coast is usually
covered with an abundant and multifarious algal vegetation, if the
conditions are in other respects favourable to the existence of alge.

There is no range of skerries (Skzrgaard) as there is, for example,
on the coast of Norway. Yet a number of islands and rocks occur
in the fjords, especially in Breidifjérdur. In this fjord are found
indications of a range of skerries running parallel with the coast
and along a considerable stretch of it, and marking the outward
limit of the Zostera-vegetation.

The Sandy Coast. Almost the entire coast of S. Iceland is
sandy shore or gravel shore. As a rule, such bottoms afford a mobile
substratum because each wave which breaks on the beach shifts the
particles backwards and forwards. A sandy coast is also met with,
here and there, in other parts of the country, but is then found,
as a rule, alternating with rocky parts; thus, the sandy or gravelly
shore is often predominant at the head of small indentations which
at the sides are bounded by projecting masses of rocks.

Clayey Shore is also found fairly frequently in the interior
of the fjords. ‘OLE

The rocky coast is, as a rule, abundantly overgrown, and this
is frequently the case also with the sublittoral gravel-bottom, while
the sand and gravel bottoms laid bare periodically by the shifting tide
are not, as a rule, overgrown, and, in any case, only with short-
lived species. On clayey and muddy bottoms, on the other hand,
algee are seldom or never found, while Zostera often covers such a
bottom and forms submarine “green meadows.”

Despite the small “desert” areas, one may say that the coasts
are covered with a zone of continuous algal vegetation — if we ex-
clude the eastern portion of S. Iceland. This algal zone varies greatly
in width, accommodating itself to the precipitousness of the coast.
In a bay as shallow as Faxafldi the algal vegetation has a great
extension seawards, while it is far more limited, for example, on
the steeply descending submarine declivities in the fjords of the
east coast.

MARINE ALGAL VEGETATION za

2. THE OCEAN.

As regards the ocean, the chief points are its movements, tem-
perature and salinity.

A. The Movements of the Ocean.

These are — tides, waves and currents. All these movements
of the ocean are of very great importance to the life of the alge.

a. Tides. By the alternate rise and fall of the tide a part of
the shore is laid bare, and the vegetation growing there must then
be capable of maintaining life in the air for a longer or shorter
period. Those plants which grow highest up in the zone thus left
dry, are exposed during the greater part of the period between the
one flood-tide and the next, or for about 10—11 hours in every 12.
The plants occurring lowest down in the zone, on the other hand,
are not exposed during spring-tide for more than one hour in every
12, and they are submerged the whole time during neap-tide. The
upper limit of the algal vegetation is, moreover, dependent on how
high the tide rises, i. e. the height of the flood-tide.

The Height of the Flood-tide. The following data regarding
the height of the flood-tide are taken from “Den islandske Lods”
(1903) and from the alterations and additions to it which have been
published. The height of the flood-tide is greatest in SW. Iceland
and least in E. Iceland. The height of the flood-tide at spring-tide
is recorded as being about 14 feet from Reykjavik (SW. Iceland),
10—11 feet from NW. Iceland, 5—51/2 feet from the north coast
and 5 feet from E. Iceland.

In many places there is a great difference as regards the height
of the flood-tide during the spring and neap tides. To illustrate
this more fully I give the following figures from some localities on
the different parts of the coast: —

Spring-tide Neap-tide

South Iceland, Vestmannaeyjar ....<.....6. 8—10 feet 4 feet
= Ei aD Ka iss, stcashawes vay shes Oe) Gs 10:7 "= Gh iis
South-west Iceland, Reykjavik ............. cir. 14 - 4 -
= Stykkisholmur 00). acc. LA = 6 -
North-west Iceland, Dyrafjérdur ........... 1 5-6 -
North) Iceland, Akureyri’. <4... 2. ...<24.6++- 51/2 - 11/2 -
Bastetceland, DyapivOeur ..’< <p )bel wince eh = - 71/2 - 21/2 -

From Ellidaey near Stykkishédlmur in SW. Iceland the height
of the flood-tide during spring-tide is recorded as being 14 feet and

28 H. JONSSON

during neap-tide 7 feet, and it is also recorded from the latter place
that the low-water at neap-tide lies about 3 feet above that at
spring-tide.

When extraordinary conditions prevail the height of the flood-
tide may be still greater; thus, 18—19 feet has been recorded from
Reykjavik and 18 feet from Stykkisholmur.

- From this it is seen that the height of the flood-tide varies
greatly, which must necessarily affect the algal vegetation in several
respects, especially as concerns the upper limit of its growth. Thus
there is a great difference in the highest flood-mark (at spring-tide)
and in the lowest flood-mark (at neap-tide). The tidal wave or the
tide, moreover, shows irregularities, because neither the highest
flood-mark (spring) nor the lowest flood-mark (neap-tide) is constant.
The limit of the flood-tide fluctuates perpetually between a high-
mark and a low-mark. The high-mark or the highest limit of the
flood-tide is seen distinctly on rocky coasts from the action of the
sea on the rock. On flat coasts, the high-mark can be distinguished
by detached algze and various other bodies which accompany the
tidal wave and remain at the highest level reached by the water.
This high-mark lies considerably higher than the upper limit of the
algal vegetation.

The low-mark is not as easy to distinguish as the high-mark,
but it will almost coincide with the upper limit of the Pelvetia- —
Fucus spiralis association. Above this the Bangia association (Ulo-
thrix, Bangia, and others) is found, the extreme limit of which will
almost coincide with an average water-level which, however, does
not lie midway between low-mark and high-mark, but rather nearer
the former. The upper limit of the algal vegetation thus lies some-
what above the limit of the flood-tide at neap-tide. The same rule
holds good, of course, on a very exposed coast. That the place is
exposed means that there is a heavy swell, which causes the sea
to rise higher up on the coasts, both at neap-tide and at spring-tide.

By the upper limit of the marine algal vegetation is meant that
boundary line above which marine alge do not occur in the form
of associations; on the other hand, no account is taken of single
individuals or groups of individuals being found higher up, in
crevices or pools, as such an occurrence must be considered accidental, —
because they are carried up to this height with the high water or
by far-reaching breakers. They do live, of course, but do not thrive,
and have evidently gone beyond their real area of distribution. In

MARINE ALGAL VEGETATION 29

this respect, however, those species should be excepted which can
grow both in salt and in fresh water, as for example, Enteromorpha
intestinalis (the principal form) and others. Naturally, such species
cannot be taken into account when defining the upper limit of
srowth of marine algal vegetation.

If we compare the upper limit of the marine algal vegetation
in Iceland with the same limit in Greenland it appears that they
agree almost completely, as Rosenvinge (63, p. 89) sets the limit
in Greenland almost at flood-mark at neap-tide. On the other hand
there seems to be an incongruity with the Ferées, as Bérgesen
(11 and 12) sets the limit far above highest flood-mark in exposed
places and almost at uppermost flood-mark in sheltered places.

If we institute comparisons with more distant coasts, for instance
with the west coast of Sweden, the algal vegetation of which has
lately been described by Kylin (43), we find that, as regards the
upper limit, the case is the same as in Iceland, that is, the upper
limit is coincident with an average water-level which lies higher in
exposed places than in sheltered ones.

In Iceland, indeed, on a very exposed coast, marine algz can
be found rather high up, and if the sea is smooth and calm they
may appear to be rather far away from the water; but on returning
to the same place when the sea is in motion we see that it
washes over them, and we no longer think it strange that they
grow in so high a position. While the marine algal vegetation, as
mentioned before, only extends upwards to an average water-level,
it frequently happens on flat coasts that the land-vegetation is sub-
merged at spring-tide. This occurs both in the interior of the fjords
and on the lower islands, and may generally be distinguished by
the appearance and the components of the vegetation; marine alge,
however, do not occur among such vegetation.

Some phanerogams, e. g. Atriplex, Mertensia, Cakile, etc., also
grow below the upper limit of the littoral zone. According to Ro-
senvinge it happens in Greenland also that the land-vegetation is
submerged at spring-tide.

b. The Swell. Here, those inequalities in the surface of the
ocean which in every-day language are called waves, and that
volume of water which, with a sea-wind is forced in towards the
land, are treated collectively. The volume of water which is driven
towards the coast by a sea-wind raises the water-level. While the
tidal wave rises, the sea moved by the wind works together with

30 H. JONSSON

it, but when the water falls it counteracts the tidal wave; this circum-
stance is of great importance on exposed coasts where the wind blows
frequently, as it shortens the period of desiccation. These move-
ments in the sea are naturally somewhat irregular, but the irregu-
larities are quite equalized in the long run, and therefore the effect
of these movements may very well be regarded as constant. The
high-mark which the water leaves on the coasts is due to the tide
and to these movements jointly.

A frequent sea-wind has a favourable eaeel on the vegetation
in the zone laid bare by the tide, as mentioned above, but where
a frequent land-wind is blowing the effect is the reverse, as this
counteracts the rise of the tidal wave and accelerates its fall, whereby
the period of desiccation is prolonged. 7

The effect of the waves beating on the algz is great. In ex-
posed places, that is in places where the swell is heavy, the plants
must be able to withstand the drag of the waves. The species
which grow in these places therefore have a tough, leathery and
narrow frond, whereas species in quiet waters have a delicate frond,
often broad and brittle. The consistency of the frond thus accom-
modates itself to the force of the beat of the waves, and in partially
exposed places, or in places where the beat of the waves is not
strong, but yet fairly considerable, we find the consistency of the
frond to be about midway between what it is in exposed and in
calm places.

Like all other movements of the sea, the waves also are of
great importance to the algal vegetation by the fact of their con-
stantly providing fresh particles of water.

c. Currents (Fig. 2). Along the coast of Iceland the warm water
of the Atlantic Ocean meets the cold water of the Arctic Ocean.
The Gulf Stream washes the south coast of the country and sends
an arm northward along SW. Iceland and NW. Iceland, and along
the entire north coast warm water can be traced (the eastern arm
of the Irminger Current) to Langanes; and from thence the arm
turns toward the south along the coast of E. Iceland (Nielsen, 52,
p. 13), where it mixes with water from the East Iceland polar cur-
rent, which comes from the Norwegian Sea (Helland-Hansen
and Nansen, 27, p. 287, where the current is called the East
Iceland Arctic Current). In this manner characteristic coast-water
arises at E. Iceland. Regarding this Nielsen (52, p.13) writes that
the Irminger Current “gives the waters over the coast shoal of East

MARINE ALGAL VEGETATION ol

Iceland a physiognomy different from that of the surrounding sea,
the distribution of temperature being different even if the tempera-
ture is not in any important degree higher than in the East Ice-
landic polar current itself.”

The conditions of the currents in N. and E. Iceland are evidently
very complicated, and only the direction of the current of the
warm water has been given above in outline, but as the observations
are so few it is difficult to form an opinion as to how the condi-

Fig. 2. Map of Currents.

(Helland-Hansen and Nansen.)

tions of the currents along these coasts vary in other respects from
year to year or according to the seasons.

Further, other current-movements occur in the coast-water
which may be deemed to be of importance to the vegetation,
that is, such movements as are due to varying specific gravity. In
the summer (Nielsen, 52, p. 8) the surface-water along the coast
is lighter on account of its mixing with fresh water. A surface-
current from the coast outwards then arises, and an under-current
from the depth towards the coast. In the winter the surface-water
along the coast becomes heavier owing to cooling, and sinks. Then
a surface-current from the ocean towards the coast arises, and an
under-current from the coast towards the depth.

52 H. JONSSON

B. The Temperature of the Water.

a. The temperature of the ocean around the coasts is not suf-
ficiently known, and consequently the mean values cannot be given.
I give, therefore, as an example, some actual measurements, as
even these may be instructive in several respects. As regards NW.
Iceland, N. Iceland and the northernmost part of the coast of E.
Iceland I rely on the measurements carried out during the year
1904 on board the Danish Deep Sea Exploration ship “Thor” (Niel-
sen, 52).

East Iceland just south of Langanes.

. 66° 09/ N. lat.
24S:
en se 14° 26’ W. long.

178 m.
Depth (m.) Temp. (C°) Salinity °/oo
0 0.63 34.70
25 0.74 34.72
50 0.73 34.72
100 0.71 34.72
66° 10’ N. lat. 66° 16/ N. lat.
Aug. ibe St. 2S) 44° 99/ W. long. Aug. 13: St. 100, 130 36/ W. long.
189 m. 284 m.
Depth(m.) Temp.(C®% Salinity 9/oo Depth (m.) Temp. (C°) Salinity °/oo
0 7.60 34.43 0 8.57 34.51
10 Lo 34.44 10 8.31 34.51
25 6.90 34.51 25 6.00 34.69
30 5.89 34.69 395 4.87 —
79 5.20 34.78 50 3.08 34.88
100 4.61 34.85 1D 3.32 34.91

North Iceland east of Eyjafjéréur.

66° 32/N. lat. _ 66° 33¢N. lat.
April Dae St. 14, 17° 50: W. July 2 tt St. 74

long. > 18° 10‘ W. long.
175 m. (om:
Depth (m.) Temp. (C°) = Salinity °/oo Depth (m.) Temp. (C°) = Salinity °/oo

0 1.50 34.85 0 8.40 33.91

25 1.65 34.87 10 “TAG 34.79

50 1.68 34.87 17 7.19 } (34.85

100 170 34.85 21 6.34 © —

25 5.49 34.82

50 5.06 34.87

MARINE ALGAL VEGETATION 3a

66° 14/N. lat. 914/N. lat.
aie: St. 73, 500 59. ee Aug. 15. St. 104, se hy a ieee
197 m. 226 m.
Depth (m.) Temp. (C°) Salinity °/oo Depth (m.) Temp. (C°) Salinity °/o0

0 10.5 31.62 0 8.60 34:27

10 GA2 oid 10 8.52 Be |
7 6.52 34.43 2 7.84 34.47
25 6.74 34.69 oD 71 34.60
50 5.95 34.76 50 5.90 34.82
75 yay, 34.88 75 5.63 34.86
100 4.84 34.96 100 5.40 34.91

North Iceland west of Eyjafjéréur.

0 4 0 4
April 23. St. 13, ae - fee Aug. 23. St. 106. a age eae
220 m. 222 m.
Depth (m.) Temp. (C°) = Salinity °/oo Depth (m.) Temp. (C°) = Salinity °/oo
0 254: 34.94 0 4.50 32.18
25 2At 34.96 10 4.70 32.94
50 ZA 34.97 17) 5.65 cee
100 — 2.46 34.97 25 6.30 33.89
30 6.11 33.93
od 4.42 39.90
50 4.27 34.54 ©
62.9 5.45 34.75
75 5.62 34.83
90 5.84 34.94
100 6.12 35.05

66° 31/N. lat.
April 23. St. 12, 990 95. w. long.

62 m.
Depth (m.) Temp. (C?) Salinity °/oo

0 1.20 34.76

40 1.05 34.81

60 1.05 34.81

66° 29/N. lat. 66° 30’ N. lat.
J une De St. OL; 929 25/ W. long. : Aug. aA: St. 107, 92° 27° W. long.
62 m. 46 m.
Depth (m.) Temp. (C°) Salinity °/oo Depth (m.) Temp. (C°) = Salinity °/oo

0 552 34.67 0 8.91 34.58
10 3.49 34.67 10 8.96 34.58
DAS 3.49 34.70 20 8.93 34.58
60 3.49 34.70 30 8.91 34.58

45 8.72 34.61
The Botany of Iceland. I. . 3

34 H. JONSSON

North-west Iceland.

5 66° 17’ N. lat.
April Daas St. 10: 23° 14’ W. long.
125 m.

Depth (m.) Temp. (C°) — Salinity °/oo
0 1.42 34.69
50 2.82 34.99
120 2.94 35.05

66° 20’ N. lat.
June 2. St. 52; 23° 31/ W. long.

142 m.
Depth(m.) Temp.(C®) Salinity °/oo

0 4.25 34.92

10 4,24 34.92

25 4.17 34.98

50 4.19 34.99

75 4.25 34.99
100 4.34 39.01

: 66° 33’ N. lat.
April Doe Stil? 239 37 W. long.

84 m.
Depth(m.) Temp.(C°) Salinity °/oo
Os 2.40 34.97
82 2.97 =

66° 19’N. lat.
Aug. 24. St. 108, 93° 27°‘ W. long.

115 m.
Depth (m.) Temp.(C°®) Salinity °/oo
0 9.42 34.67
10 9.52 34.66
295 9.46 34.66
30 9.39 =
50 8.16 34.85 _
79 1.30 34.91
110 6.76 35.01

Almost at the boundary between NW. Iceland
and SW. Iceland.

65° 32" N dat
June 26. St. 61, 940 34. w. long.

41 m.
Depth (m.) Temp. (C°) Salinity °/oo
0 8.17 34.13
5 7.93 34.25
10 MATOS 34.34
20 7.66 34.90
40 7.61 34.52

65° 29’ N. lat.
Au = ZirS 109, 940 375 W. long.

43 m.
Depth(m.) Temp. (C®) Salinity °/oo
0 10.26 34.54
10 10.20 34.54
15 10.20 34.53
25 10.21 34.54
40 10.21 34.57

The measurements recorded show distinctly the range of the

temperature in April and August, 1904. By taking successively the
stations 11 (April 23rd), 13 (April 23rd), 14 (April 23rd) and 15
(April 24th) it is distinctly seen how the temperature of the surface-
water of the ocean along the north coast of Iceland decreases from
west to east, as shown by the following figures: —-

St. 11 St. 13 st.14 St. 15
2.40° 2.34° 17500 0.63 °

A similar decrease of warmth from west to east, but in a far
lesser degree, appears to occur in the month of August. :
Station 106 (Aug. 23rd) shows a much lower temperature than

MARINE ALGAL VEGETATION 30

was to be expected, which is unquestionably due to the water from
the East Greenland polar current, as the ice was still, or had re-
cently been, in the neighbourhood.

South Iceland.
From the ocean south of Iceland there are also measurements
to hand carried out on board the “Thor” (Nielsen, 53).

South coast west of Dyrhé6laey.

63° 32’ N. lat. ; 63° 08/ N. lat.
106 m. 662 m.
Depth (m.) Temp. (C°) Salinity °/oo Depth (m.) Temp. (C°) Salinity °/oo
0 10.89 35:14 0 10.44 35.16
Zo 9.77 35.14 25 10.18 35.16
50 8.06 35:14 50 8.07 35.16
104 7.85 35.16 100 1:67, 35.19

63° 16/N. lat.

63° 25/N. lat.
ee et 2 19917 Wolong, OS OF St E14, 1904 55003/W- long.

765 m. 150 m.

Depth (m.) Temp. (C°) — Salinity °/oo Depth (m.) Temp. (C°) = Salinity °/oo
0 11.45 35.03 0 11.70 34.49
25 10.09 39.14 10 11.70 34.51
50 8.14 3) eral! 20 11.55 34.65
100 era a0.20 30 1i3od 34.92
40 1135) 35.03
45 10.95 30.07
50 9.78 35.04
79 7.97 39.22
100 114 JDO

South coast east of Dyrhdlaey.

63° 51° N. lat.
May 23. St. 46, 1905, 460 95. w. long.

60 m.
Depth (m.] Temp. (C°) Salinity °/oo
0 7.91 34.81
10 7.14 34.99
25 6.87 35.14
58 6.90 35.16

There are moreover some notes, given by Knudsen (44), on
the temperature and salinity of the surface-water of the ocean south
of Iceland. They are based upon the measurements carried out on

3*

26 H. JONSSON

board the mail steamer “Laura” on its route from Scotland to Ice-
land during the years 1897—1904.

Between longitude 17° and 18°, near the coast of Iceland, in a
south-easterly direction from Dyrhdlaey, the mean temperature of
the year (1897—1904) is stated (44) to be 8.8° and the mean salinity
during the same period 35.19.

The main features regarding the temperature of the ocean
around Iceland then are as follows — At the south coast warm,
pure Atlantic water of a high (above 35 °/oo) and somewhat varying
salinity occurs; at SW. Iceland there is a somewhat. similar sea; at
NW. Iceland and N. Iceland there is Atlantic water mixed with cold
water of low salinity from the East Greenland polar current; and
lastly, at E. Iceland Arctic water occurs (with a temperature of 0° to 2°
and salinity from 34.6 per cent. to 34.9 per cent. [Helland-Han-
sen and Nansen, 27, p. 287]): the East Iceland polar current mixed
with water from the Atlantic current.

The change of temperature in the surface-layers of the water,
the cooling process during winter and the heating process during
summer, reaches down almost as deep as the algal vegetation, and
is consequently of no slight importance to the latter.

b. The Temperature in the Fjords. Respecting the tempe-
rature of the surface-water of the ocean throughout the year infor-
mation is given in the “Meteorologisk Aarbog” (Meteorological Year-
book) regarding three stations in Iceland: Papey, Grimsey and Styk-
kishélmur. The following figures show the seasons’ mean tempera-
ture of the ocean for a period of five years (1902 —1906), chosen
arbitrarily. Grimsey is omitted, however, as the observations there
have often been incomplete.

Winter Spring Summer Autumn
Papey (E.Iceland) ..... . 0.9° 1.79 6.0° 4.39
Stykkishélmur (SW. Iceland). 0.4° 1.8.8 9.6° 6.4°
Vestmannaeyjar? (S.Iceland). 4.1° 621% 10.4° 708

The winter in Papey is warmer than in Stykkishélmur, and the
monthly mean temperatures during the winter, of the period mentioned,
are there all positive; while in Stykkishélmur, February (— 0.8) and
March (-— 0.2) have negative numbers. The summer is much warmer

* The figures for the Vestmannaeyjar constitute the mean of the period from
July 1st, 1877 to Dec. 31st, 1906. According to borvaldur Thoroddsen, Lysing
Islands, 2. Bd., pp. 350—351, Kaupmannah6fn 1910.

MARINE ALGAL VEGETATION a

in Stykkishélmur. A comparison of these two places is, however,
not equivalent to a comparison between E. Iceland and SW. Iceland,
the situation of the stations being quite different. Papey is an island
lying isolated in the ocean; Stykkishélmur, on the other hand, is
a good example of the thermal conditions existing in the calm fjords.

Regarding the temperature at various depths in the interior of
the fjords some observations are to hand made during the summer.
These are, however, too few and scattered to be given in mean
values. I give, therefore, as an example, some actual measurements
from different parts of the coast of Iceland.

In East Iceland the measurements of temperature were car-
ried out on board the Survey vessel “Diana” (Fisheries’ Report
(“‘Fiskeri-Beretning’’) for the financial year 1899—1900), and of these
the following are given: —

Depthinfathoms Temp. (C?)

RfellistjorOur (9/5). 4. ...5. ees « us 0 1%
10 1.6
Laémundarfjorour ("/6).......... 0 5.0
7 | cir. 33 1.5

iactcleat |OPOUE)(2°/ 6)... 22 da cia wens 0 8.0
ih 2.5

BooMeMOROUE (29/6) 2.0 0. - + sss | 0 4.5
131/2 1.8

fommasorour (146)... mes bi als esac 0 3.8
81/2 2.4

RaMAVOMOUT (C°/7) . aa... ou ee 0 6.5
5 6.3

Bretodalsyik (o/s). sc). 4.75 bk nek 0 4.6
Bottom 4.3

The low bottom-temperature in June is probably due to the
East Iceland polar current.

In addition to these Semundsson!? has published the fol-
lowing measurements of the temperature and salinity of the surface
of the fjords in East Iceland.

Temp. of the Salinity

surface (C°) °/o0
Diupivogur (°/s) ..... 9.0 29.47 high-water.
a ae ee 7.4 33.14 low-water.
Faskridsfjordur (19/s).. 10.0 33.67 | at Buoir.
—- ee 9.5 32.23 at Mjdeyri.
— re 9.4 33.54 at Brimnes.
a oe 9.0 32°19 erat Hotton:
- Crla).. 7.0 ' 34.71 at Kolfreyjusstadur.

1 Bjarni Semundsson, Fiskirannsdknir, 1898, Andvari, XXIV arg.

38 H. JONSSON

Temp. of the Salinity

surface (C°) °/o0
Vattarnes (71/s)....... 8.5 34.58 near land.
Eskilj@nour 2/8) e 9.3 1.31 in the fjord, after rain.
— ais) wee wee 5.0 6.73 near land, outflowing current.
os ET: See ad 5.0 23.71 out in the fjord, in outflowing
current. ;
~~ SO a aa 5.0 34.45 out in the fjord, in inflowing
current.
Norofjoréur (27/3) ..... 7.5 34.45 near land.
Mjoifjordur (°9/s) ..... 6.5 33.00 at Brekka.
Seydisfjérour (“/s) .... 9.5 9.23 head of the fjord.
- (Aire 7.5 22.01 =
— ana te 8.0 22.01 out in the fjord.
— ase A Ce oe 8.5 25.04 ——
= ae ee 7.8 S005" —
— Sy A 7.5 31.96 —-
= (Ue) cw 7.0 34.45 at Skdlanes.
— (iio)! steam 7.0 34.45 at Brimnes.
— (3/9) mea 6.5 33.01 at Dvergasteinn.
Borgarfjordur (4/9) .... The 34.45 out in the fjord.
Vopnafjéréur (°/9) .... 7.5 33.27 near land.

From the most westerly part of the north coast and from the
northern part of the north-west coast as also from Breidifj6rdur
measurements are to hand of the temperature and salinity of the
ocean at various depths in the interior of the fjords taken by
Bjarni Semundsson (Fiskirannsoknir, 1908, Andvari, XXXIV arg.)
of which the following are given: —

Depth Temp. Salinity
North coast, in metres ce °/oo
SicingrimsfjorouriGt/7)). (be. seen mee 0 10.8 274
15 9.7
30 9.2 34.3
595 3.2 a40
SteingrimsfjoroummG/e)aa- ie tee 0 10.6 34.0
15 9.9
a0 7.8 34.6
70 5.8 34.7
100 4.2 34.7
Hritatjorour (1/3). ee eee 0 7.5 34.6
15 6.0
30 4.8 34.7
44 4.5 35.0
North-west coast,
Mjoifjorour, the inner part (°/7)...... 0 11.8 30.6
25 6.5 — (34.5
50 5 34.9

MARINE ALGAL VEGETATION

Depth
: in metres
Sk6tufjoréur, the inner’ part (16/7)..... 0
15
35
70
. 105
Isafjardardjip, 11/2 mile NW. of Ogur-
rie. (72/5) (aS aioe oe comes 0
18)
S15
70
100
South-west coast,
Skardsst66 in Breidifjérdur (13/s) ...... 0
(outside) 8
oA TUSSUCC) ee 0
(near land) 6

Salinity
°/o0

30.5

34.3
34.7
34.7

o2.2

34.0
34.9
35.9

34.0
34.5
24.8
34.3

39

Bjarni Semundsson has kindly given me the permission,
moreover, to make use of his hitherto unpublished measurements
of the temperature of the ocean at SW. Iceland (Breidifjé6rédur and
Faxafléi), in the interior of the fjords, from the summer of 1909.

Of these the following are given: —

Depth

Breidifjordur
Stykkishélmur (the port °/7):........ 0
About 1/2 a mile SE. of Vadstakksey (7/7) 0

About 4/2 a mile SE. of Hrappsey (2°/7) 0
Kolgrafarfjéréur, the interior (27/7) .... 0

Kolgrafarfj6rdur, the mouth (18/7) ..... 0

Hvammsfjérdur about 2 miles SE. of
ibambey 00/7) 6. 3... - i: es oO 0

in metres

Temp.

Cc?
10.6
10.1
10.1
Gal
10.0
11.5
10.8
10.7
10.5

Salinity
°/o9
oo.1
34.2

34.6
30.1
33.9

34.0
34.2
33.9

34.2
34.1
34.7
34.8

32.7

Jo.
34.1

40 H. JONSSON

Depth Temp. Salinity
ESreariten in metres aga ok °/o0
5 miles SW. of Akranes (26/7) 0 115 34.4
15 10.6
30 9.2 34.7
60 7.8 34.9
Knanarnes.c.. St ok ite. sae AE 0 14.0 34.0
About 2 miles SE. of Por-
moossker (@!/7)eh . 2. sahes 0 12:2 34.6
15 10.2
30 9.5 34.6
45 9.1 34.7
Borgarnes((/s) it. 2. aoe 0 12.4 26.9 high-water.
= (Ciig)s'c eee eae 0 12.4 18.9 low-water.
With Seleyriu itis”. ste 0 11.2 8.8 .
5 10.6 14.7
Borgarfjéréur, the mouth (7/s) 0 11.7 28.9
10 11.6
20 eS 34.4
Hvalfjérdur, Hvammsdjup
(ois amet ae eae eek 0 11.6 33.4
15 11:4
30 Tee 34.0
60 ip te 04.2
Hvalfjordur, Galtarvikurdjup 0 147 33.9
5) ss
30 i 0 ie 34.0
50 it BGI 34.4
85 11.0 34.3

From the measurements given above it will be seen that the
temperature of the water in the interior of the small fjords is nearly
the same from surface to bottom, while a regular decrease of warmth
is immediately felt with the increase of depth in the more open
waters. The temperature of the fjord-water is evidently dependent
on the climate of the country; but regarding the temperature, during
winter, for instance, we know nothing. Nor am I prepared to treat
of the distribution of warmth in the coastal water in a more exact
manner, as from the scattered observations made during the summer,
which are at our disposal, no satisfactory results can be arrived at
regarding the thermal conditions in which the algal vegetation exists
all the year round.

C. The Salinity.

The degree of salinity is given above, together with the tem-
perature.

MARINE ALGAL VEGETATION Al

a. The Sea. South of Iceland the salinity varies but slightly,
with the exception of the coastal water itself. During the summer,
at any rate, the salinity of the coastal water must be considerably
lower on account of the great amount of fresh water brought down
by all the rivers of the south. On the other coasts and especially
those of N. and E. Iceland the salinity varies according to whether
the layers of water originate from currents which are deficient in
salt or from the Irminger current, and also with the amount of
fresh water streaming out from land. At station 106 (see above) the
inferior salinity is evidently due to cold water from the Greenland
current, and at station 73 it is probably due to fresh water.

b. The Fjords. The salinity inside the fjords varies consider-
ably and the variation is dependent upon the amount of fresh water
which intermingles with the water in the fjord, partly in the form
of river water and partly in the form of precipitated moisture. The
lowest salinity in the fjords was 1.31 °/oo in Eskifjéréur after rain.
Heavy rainfalls must be capable of causing such an inferior salinity
in other places also, especially in narrow fjords, but this will not
last long, and as the littoral alge can endure heavy showers during
-low-tide, they will not suffer to any extent worth mentioning.

In places where the salinity is as low as in Seydisfjérdur
(9.23 °/oo), where a rather large river disembogues, the algal vegeta-
- tion occurs sparingly, although alge are found, especially green and
brown algz. At a place like Borgarnes, where the salinity is low
(18.9; 26.9) on account of fresh water from Hvita, the algal vegeta-
tion occurs more abundantly than at the very head of Seydisfjéréur.
by the river, but the inferior salinity excludes certain species, for
instance, Polysiphonia fastigiata, although Ascophyllum occurs abun-
dantly. Further out, where the sea is more saline, it is not absent.

It is especially in the surface-water of the fjords that the sali-
nity varies so much. It is greater in the large open fjords, such as
Faxafléi, than in the small land-locked fjords, such as Hvalfjérdéur,
a circumstance which must certainly be due to river-water. The
figures given show also that the salinity of the surface-water of the
smaller fjords is less in the inner part than in the outer part. The
same difference seems to appear also between the deeper layers of
water of the inner and outer parts.

As a rule, the salinity of the deeper layers is higher and more
stable, which must be beneficial to the vegetation in the depths.

42 H. JONSSON

ah PBCATR:

The climate is of special importance to that part of the algal
vegetation which is exposed during low-tide. The temperature is
possibly of least importance in a climate where high and very low
degrees of temperature do not occur, or are, at any rate, rare. The
degree of humidity of the air and the cloud-covering are, on the
other hand, highly important to the algal vegetation which is left
dry. The movements of the air are also of importance, especially
as it produces movements in the sea.

A. The Temperature.

The following means (19 years)! from a number of stations on
different parts of the coast are here given for the elucidation of the
thermal conditions.

E. Iceland Winter Spring Summer Autumn The year
Papey ot eee: AG Ge eae 0.1 6.0 5) 2.1
BenuijGrOumy .ayiee epee clio. Beene —1.4 0.8 7.6 3.9 2.6
N. Iceland
PVA AH OLE ae ids Oe ee keene —40 —19 6.5 1.6 0.5
GTTMSEY* o-oo Bete ete es Sa esis ee ba 6.1 2.9 1.3
SW. Iceland
StykkiSholmpr ce shccks ogres ately. eee 0.8 8.9 3.9 2.9
S. Iceland :
Vestmannaeyian gti <9. os ora at 3.8 37 5.2 5.0
my rarbalkka (ei Perccate st etactre. S711) Ze 10.2 3.5 3.9

From the figures given above it will be possible to form an
opinion of the thermal conditions in the places mentioned, and
these are altogether such that an algal vegetation left dry can thrive
everywhere along the coast. The extremes will not have a sufficiently
injurious effect on the vegetation for it to be noticeable in the long
run. High degrees of temperature, about 20°C for example, occur
rarely in the summer, and will have no permanent effect. Very low
degrees of temperature in the winter will not injure the vegetation
left dry to any extent worth mentioning, as it is then partly pro-
tected by snow (at the very top) and partly by ice.

I do not consider the cold in the winter injurious to the vege-
tation which is left dry, as the algz certainly endure being frozen
fairly well. At least I have seen uppermost in the littoral zone,

* Willaume-Jantzen, Meteorologiske Middeltal og Extremer for Fzeréerne,
Island og Grénland, Kj6benhavn, 1899.

MARINE ALGAL VEGETATION 43

early in May, algz which had been frozen hard during the night,
apparently quite unharmed and alive when thawed, nor could one
perceive next day that they had suffered at all; but, as I was tra-
velling, I was not able to observe them more than these two days.
It is also a foregone conclusion that the alge left dry must freeze
in the winter when the cold is severe, but it does not appear that
they suffer thereby.

If the cold cannot be said to have any directly injurious effect,
yet indirectly it may hurt the vegetation (though not to any great
extent) by the fact that the water freezes and the beach becomes
ice-covered. During severe winters a covering of ice may be found
during the greater part of the winter in the smaller fjords, and
especially where the fjord-water is abundantly mixed with fresh
water, and even if the winters are quite mild, yet from time to
time the water next the beach may freeze. In the littoral zone and
on rocks which are laid bare during low-tide, the ice forms in ac-
cordance with the substratum, and if this is uneven the ice breaks.
At high-water the ice-covering is lifted up; the pieces of ice may
then freeze together again, and break once more with the next ebb-
tide. During spring-tides in particular these movements are rather
considerable and the plant-covering may be a good deal damaged
thereby: but if one regards the coasts in their entirety these distur-
bances will prove to be of small importance.

The drift-ice is much more dangerous to the algal vegetation
as the icebergs scrape the rocks with which they come in contact.
Stromfelt, when travelling in Iceland in 1883, the year following
one of the years notable on account of the great quantity of ice,
found the littoral vegetation poorly developed in the north country.
This most certainly resulted from the drift-ice having blockaded the
coast during the whole summer of 1882. In the summer of 1898, I
saw on the promontory between Seydisfj6réur and Lodmundarfjéréur
distinct signs of the drift-ice which had been there in the spring.
The injurious influence of the drift-ice consists mainly in the fact
that it scrapes away the vegetation from the parts with which it
comes in contact; possibly also in the fact that it reduces the tem-
perature to far below normal. That the plants suddenly find them-
selves in a much colder medium than they are accustomed to must
produce a check upon them, particularly on the more sensitive
species. The marine plants, however, are less affected by this than
the land vegetation. As a rule, ice-years occur at fairly long intervals;

44 H. JONSSON

consequently the damage which the ice causes is not noticeable in
the long run, it is noticed chiefly in the same year or-the year
following, and is remedied comparatively quickly.

B. The Humidity.

Very great importance must be ascribed to this as regards the
algal vegetation left exposed. During the period of desiccation there
is always the danger of the evaporation becoming too great, espe-
cially if the air is dry. The more humid the air, the better the
algee will be able to maintain life in it. The following figures from
four places, each situated on a different part of the coast, show the
mean humidity of the air as percentages (Willaume-Jantzen
len)

. Winter Spring Summer Autumn
E. Icel, Berufjordur @3 years): 20.4... 77 78 81 80
N= icel. (Grimsey . (2a veGars) c's 8. en eeee 83 83 85 86
SW. Icel. Stykkishélmur (20-23 years) . 88 85 83 86
S. Icel. Vestmannaeyjar (12 years) .... 81 79 82 81

As a comparison with the Ferédes might be of interest, the
figures showing the mean humidity as percentages at Thorshavn
Willaume-Jantzen, |.c.) are appended.

Winter Spring Summer Autumn

Thorshavn in the Fer6es (25 years).. 81 79 84 84

From these figures it appears that the humidity of the air in
Berufjérdur is less than in the Ferées while the humidity of the
air at Grimsey and also at Stykkishédlmur is greater than in the
Feerdes. The humidity of the air in the winter and the spring in
the Vestmannaeyjar and in the Ferdées is the same, while at the
latter place it is a little greater in the summer and autumn.

C. Precipitation, Amount of Cloud, Foggy days, Wet days.

a. Precipitation. The following figures show for purposes
of comparison the mean downfall in millimetres at four places in
Iceland, one on each coast, and at Thorshavn in the Ferées (Wil-
laume-Jantzen, 1. c).

Winter Spring Summer Autumn The year
E, Icel.. Berufjérdur (23, years)... 348.0. | 222.7 | 203.7. 34035 eae
N. Icel. Grimsey (16-22 years)... 83.5 64.8 85.6 139.9 373.8
SW. Icel. Stykkish6lmur (18-22 yrs.) 191.5 115.2 113.6 203.8 624.1
S.Icel. Vestmannaeyjar(15 years).. 354.1 257.3 2521 402.2 1265.7
Thorshavn in the Ferées (25 yrs.). 510.9 485.2 272.4 3246 1593.1

MARINE ALGAL VEGETATION 45

As shown by the figures there is a considerable difference in
the amount of precipitated moisture. That of Thorshavn is greatest,
next come the Vestmannaeyjar, followed by Berufjéréur. The preci-
pitation at Stykkishélmur is not more than half that in the Vest-
mannaeyjar, and that of Grimsey is not more than a fourth part
of that in the Vestmannaeyjar.

b. Mean Amount of Cloud (Willaume-Jantzen, 1. c).
Scale 0—10.

Winter Spring Summer Autumn
E. Icel. Berufj6rdur (23 years).:...... 6.4 6.6 6.9 6.6
Nelieel Grimsey, (22 years).....1..... 8.5 8.2 7.9 8.5
SW. Icel. Stykkishélmur (22 years).... 7.1 6.4 6.0 6.9
S. Icel. Vestmannaeyjar (18 years)..... 6.2 6.1 6.1 6.3
Thorshavn in the Fer6ées (25 years).. 7.4 Ppa via 7.9

The amount of cloud is greatest in Grimsey, and there is no
great difference between the remaining three coast-stations in Ice-
land. In Thorshayn, however, the amount of cloud is considerably
greater and consequently this place approximates to Grimsey.

c. Foggy and Wet days. Mean number of Foggy days (Wil-
laume-Jantzen, |. c.).

Winter Spring Summer Autumn The year
E. Icel. Berufjérdur (23 years). 44.0 52.0 67.0 49.0 212
N.Icel. Grimsey (22 years)... 2.4 13.0 31.0 7.0 53
SW.Icel.Stykkish6lmur(22 years) 1.0 2.6 4.1 13 9
S.lcel. Vestmannaeyjar (18 years) 7.0 12.0 21.0 12.0 De
ThorshavnintheFeroes(25yrs.) 3.0 10.0 29.0 9.0 SM!

The number of foggy days in Berufjéréur is remarkably high,
and at Stykkishélmur is extremely low. In Grimsey the number is
much lower during the winter months, and higher during the
summer months than it is in the Vestmannaeyjar; there are also
small differences during spring and autumn. There are only small
differences between the Fzerées and the Vestmannaeyjar, except in
the winter, when the Vestmannaeyjar have twice as many foggy days.

Mean number of Wet days (Willaume-Jantzen, l. c.).

Winter Spring Summer Autumn The year
E. Icel. Berufjérour (23 years). 52 43 34 48 177
N. Icel. Grimsey (22 years)... 40 29 29 45 143
SW.Icel.Stykkishélmur(22 years) 958 47 40 52 197
S.Icel. Vestmannaeyjar(18 years) 64 595 47 59 225
Thorshavn inthe Feroes(25yrs.) 81 66 58 74 279

At all seasons the number of wet days is highest in the Fzrées

46 H. JONSSON

and in the Vestmannaeyjar, yet considerably higher in the former
place. Grimsey has the fewest wet days, and Berufjéréur and Styk-
kisholmur have somewhat similar numbers.

It is in the spring and the summer especially that the desicca-
tion, during the period of exposure, may have an injurious effect
in the zone laid bare along the coast. The amount of cloud is of
course important, since clouds diminish the ‘danger of desiccation,
but the mean figures are not sufficiently elucidatory. Bright sunny
days are not propitious to the vegetation left exposed, especially if
several such days occur in succession; and if this takes place at
neap-tide, the vegetation which is found above Pelvetia-Fucus spiralis
is in danger. Although the weather in Iceland varies greatly, longer
periods which are damp or dry often occur. Clear days are not
uncommon in the spring and summer, and. periods of even a week
or more of bright weather are not rare. On bright sunny days in
summer the temperature may rise rather high; I have measured
20° C. on such a day in a pool in the littoral zone, in the plant-
covering itself, and the temperature of the air may rise even higher.

The periods of bright and dry weather are certainly of impor-
tance as regards the upper limit of growth of the algal vegetation
during the summer. The Ferées are probably less favoured by
clear weather than Iceland, and the difference in the upper limit
of growth of the algal vegetation in Iceland and in the Ferées may
possibly be partly explained by this.

D. Winds.

The following figures show the annual percentage (Willaume-
Jantzen, l.c.) of the winds: —

Berufjordur Grimsey Stykkisholmur Vestmannaeyjar
IN aii Re Rca hance teeeveee 6 8 5) 13
NE th aS cae 24 18 18 2
| RNA A ra Se fa RE + 20 20 23
SIE B8o0o ye adenine v5, cee 6 16 16 9
Ro ENS Ia Sa ARM Ff 8 4 ii 8
SW ASME Si crn bhebe eer sheng 15 5 10 10
WW SENSE ie nceuaue aust cee ooh + 2 7 8
IN WV cicero aca eects a 23 7 3 +
Gali 22% Se Bt aye facets: 10 10 12 22

MARINE ALGAL VEGETATION 47

It happens rather frequently that the winds are stormy and,
as an example, the annual percentage of storms for Stykkishélmur
(from */9 1845 to *4/2 1892) may be given: — N. 32, NE. 61, E. 13,
SE. 17, S.44, SW. 31, W. 26, NW. 11.

The frequency of “calm” is 10 °/o at Grimsey and in Berufjéréur
and the frequency of “wind” is therefore .90 °/o in both places; at
Stykkisholmur the frequency of “calm” is 12 °/o and that of “wind”
88 °/o; in the Vestmannaeyjar the frequency of “calm” is 22°/o and
that of “wind” 78 °/o.

At Thorshavn, in the Ferées, the annual “calm” is 11 °/o and
the frequency of “wind” 89 °/o, somewhat the same, therefore, as
at Stykkishélmur and greater than in the Vestmannaeyjar.

4. LIGHT.

The influence of light on the distribution of the algal associa-
tions and on their appearance is, as is well-known, exceedingly
great. Without doubt most investigators assume that the main di-
vision of algal vegetation into a green, a brown and a red zone is
due to the quality of the light, but one cannot on that account
consider the intensity of the light to be of no importance. To what
extent the shades of colour in the red alge are to be regarded as
an adaptation to the intensity of the light or to the quality of the
light, I find rather difficult to decide.

I agree with Berthold and Oltmanns in thinking that the
Floridee may be characterized as shade-plants in the same sense
that we speak of shade-vegetation in lava-clefts and in other places
where there is a faint light. By shade-plants I understand plants
which prefer feebly illuminated spots, and do not, as a rule, thrive
in the full light of day. In the tidal region (Part VI) the littoral
Floridee evidently prefer crevices and grottoes, i. e. feebly illuminated
places, and thus prove themselves to be shade-plants.

I shall not enter more fully into the question of light, as I
have made no experiments in that connection and, moreover, the
subject requires to be reinvestigated (Oltmanns, 54).

Il. THE HORIZONTAL DISTRIBUTION OF THE
SPECIES AND THE COMPONENTS OF THE
ALGAL FLORA.

| the following list (Table I) of the hitherto known Marine Algee
of Iceland a letter (A, B,, B,, C, D, E,, E,) is placed before
each species, showing to which plant-geographical group I refer it
(cf. B6rgesen and Jénsson, 14). A indicates the arctic group,
B, sub-division 1 of the subarctic group, B, sub-division 2 of the
subarctic group, C the boreal-arctic group, D the cold-boreal group
and E the warm-boreal group. The letter c placed after the name
of the species indicates that it has been found in all the five
coastal districts (E. Icel., N. Icel., NW. Icel., SW. Icel. and S. Icel.,
see above, p. 5); a (c) placed after the name of the species indi-
cates that it probably occurs in all parts of the coast.

Table 1. The Distribution of the Species along the coast.

E. Icel. | N. Icel. |NW.Icel.|SW.Icel.| S. Icel.
Rhodophycez. |

C Bangia fusco-purpurea (c) ........... + ak a = “bh
C Porphiyra, ambilicalas"ey,o. 60. ee + + + a a
B, Pvininiatatic 208 Sok RR. ee heer ae + + + + ==
D Porphyropsis¢occimead .rsit 4) diet. . oe Bs a 4 +-
188 Conchacelis rosea. 682500 Ms ose | + oa a a ok
C Chantransia microscopica (c)......... + ye i
D C. Alarize Gamer ee. fore cam ee ee ee as 4: a ak
C Esecunidataehege we se) Aa, MRS a + > + +
B, G. wingatulas(@) geseiaons Lier Weta’: eee + + my
Ee. Chondrus .crispusie fe: eee ee eo is +) + +
D Gigartina’ mamillosa (6) 2: (224.5020 + le i? + _
Cc Abnfeltia: plicata (Wet se eee Ne tH) bi + ab
B, Phyllophora Brodizi * interrupta.... | —+ ts ab ae Res
D P; membranifolia.<: ee ee | Ee ob _
B, Actinococcus subcutaneus ........... a _ 73 ty
A Ceéeratocolax, Hartzii 2a ee | os zi

D Cystoclonium purpurascens.......... + | ak + +

Table 1.

H. JONSSON: MARINE ALGAL VEGETATION

e - to to

tw

—

we

Lom i~)

to

pr

H rm

-

ol les tesla > oh iles| Lelie coll loli utes oll lelslo| te) tell} 12)

DWUOMODWDOrPOoOM ee nroraroawrnwre

MienerellamPeMmnyl:... cece tose 5d. 442
PAMOnA ETIStata Co 2 0.05. 2 SP Seed ede
Rhodophyllis dichotoma (c)..........
Muodymenta palmata’c.....:...05. >
omentaria -clavellosa:.....2:02.. 5.2:

WeBaerw ~ corymbosa ..... 222.0. sss
PESOS yh sys 1. Sas hs Sale se S58 RN
Ws aIOUINed sy. a). Heh Lk Se Nk Pe:
Bonnemaisonia asparagoides..........
Eteresiphonia parasitica’... . 2.2...
Eolysrphonia ureeolata ¢.... 20.26.26:
2 TRIS OTE ee ne ae ee eae
121, Qu GUU OE gs IN oie eye Cee ee nea
Pee SECINS! Mets Site uss ie RS a ada oe
Rhodomela lycopodioides c..........
Wdentwalia dentata Ch. 20i.66 6.6.2.6.
Callithamnions Arbuseula.... 2.021... 5.
PSCOPMMOnUIMIEN. fei. 5 . ws ayo Daisies © Aisha
PMI APAMELEBATIS © (2/55 60. ve spose > Sos
Renocwrplimosa 25 oho als se lew ee Se
CCUM ALA tie ee 2 2 cos agehs, Mags Steers SS
Antithamnion Plumula v. boreale (c).
NSTI OYGRO SUS 0 Ig (Sp a a er ae
Ceramium acanthonotum..........

PEPESHONPCMAMIPL 00%. 055 2 = + ales eyes
PEGINICMMOSUMMN chi. oss. wp. se see Oe
POUL CORO AIIM. oa) «occ. occ Steins ¢
PApOR SECIS eric to 8c, 2 sees Geta
PAPIMUMUVCTIINE 2. aor stom) Sis. ticle ete tees
SOLO OTT aN CE), Some et cane nee oe ee
Rhodochorton Rothii c...
RRS UCM S cate Reta gal vonis «ene + viowere et
Sue MIDI EN ATE) Ce OA re ec ea
Ee PeMIc forme (6) <.\...2 ema wok os
R.amentbranaceam (¢) 0.7 Wen ih.ee.
Piamorntiafrliformis “(C) hod <s. cne a oy
WEISCAMEONIIS es. 9) a shete ees Shs hes
Petrocels (HeEMned yin... So as eee
Cruotiay Arete! «0528 cs ths war ered eee
Berge Mbit s Stee a ole: aghats saw iaiey ettve ss
Peyssonellia HOsenvingil 65/20... 0.

Diglar lewplepii Lg

eve, wy er 6 Le Ve, ese Xe,

HRhododermis: parasitica’... 6. 6..c66 03 /

The Botany of Iceland. I.

49

The Distribution of the Species along the coast (continued).

|
E. Icel. | N. Icel. |

NW.lIcel. SW. Icel.| S. Icel.

a
+
—
aa

+44:

+++:

|
|
|

oe
—
—
—

+:

a te te cca is a a eae a

yaa

+4:

a isig pia

++: +44:

+++

ti itt: t+:

++:

FEEEFEFHEEHS FEE HEHETHEFEEHEEHHTHEHHFHH:

a

++: +4:

++teo44+: $++4+4+44: 45

++++4++4:

tea

+444:

5 ee

+:

+: +:

50

H. JONSSON

Table 1. The Distribution of the Species along the coast (continued).

te

i i

_—

Sees ee oa - oon

_

i

tS

_

a

to m u

ele eile ieiews! terl ig le) ed ele) tes teh este) tor tes) We) desl lech be) to2

is} iS}

i

_

rWeoOooOww

Lithothamnion glaciale (c)...........
Me AW gem: (Gan ected aoe Sea eee
le tophiformen(G)a i ho. Went eben o ste
Lc BlAVESCOM'S Ro ocho cyAe aud Meta ettnn, idee is
A AOCCUINGIIT 9 Arley: Gonenero sheneanhen Sarees

Phymatolithon polymorphum ........
Clathromorphum compactum c.......
Lithophyllum Crouani...............
Dermatolithon macrocarpum.........
Corallina officinalis suis) ane,

Phzophycee.

Lithoderma fatiscens (€)..3..2:....-.
Petroderma:maculiforme: ...S.¢0: :-..
Ralisiatovatan(e): <« Sodan oie. a oars
Reclavatar(G)ae ss seen aes ceed wees
IVs VET OSA 716) si: tent Net bin os oe Pee
RO destagG) 9 ai. tetas Sebo tneeeh a eee
Myrionema vuleare. i ocon. oan ota
I Oost Go) STUN Cu cae ee eet WP Seep earet eee MGs
Wi SlOWOSMMAUA(G). oars. ass. de sass he Oh eee
IM TET OCRSC® srtereca ioc ein nse Pools wo Ske Stop
M.\Laminarizey (©) 2a .4- <b cae ine
Ascocyclus ‘tslandicus:5. tn 8. Coes ae
Microsyphar Polysiphoniz (c)........
Streblonema ecidioides (c)...........
S: sulophorzV- cespitoSa: C.. 4 ..265 a:
Pylarellaniittoralisve 2 Faten , thx te eee
Ectocarpus tomentosoides c..........
COMTEMEOSUSS V2 i nic. Mae's Wee op RG

SSIMEHIOSHSACE)AS Wire seul ae tate wi ee
Mpemicilatise(C)ne acc. 5 Mees eee s et oa e
fascicullatus sees. Mths eee wea oe
BB Wo co Fe Sine SSR reins 2, ee a Mn Uae Cas
Leptonema fasciculatum v. subcylin-

Orica, (Ce) AN oc games a alt etetae cea aae
Elachista fucicola¢2h e434 3.4) ose bee
Sphacelaria britannica (c)............
Siradicans "(C) ins ye hen ieee ae awe ane
S: olivacea .. Fos. in pees ore eae ae eee
Cheetopteris plumosa (c).............
Omphalophyllum ulvaceum..........

eos eoRcoes

E. Icel. | N. Icel. |NW.Icel.|SW.Icel.| S. Icel.
ogee)
+ +4 | +) ade ae
“bi |i oob o/oa eee
+ |...
Sl ieee oem a se
+} +})+]+)4
ae at.
% 2 ca “ee
+) +]+)4+/+
|)
ln
|) 4 Lose one
+|+)+)4+]+4+
+/+ ]+ ]4
=p a;
|) ea
+) +) +) 4
+ | + oh oe
+) + + 1s
+ + |
+ | +) ee
+
4 Je
| ae
Me pes,
4 | shall
+/+]+])+]4
+i) +) +)4+] 4
+} +]+)4+)4
_ x eh
+ | +3) oe
Bl ae +
+ | + 4 0
+ | +
+
ooh
+) +)+)+)4
‘cla + | +
+o] cb fo-aio ee
6g . | 4
+} + )+)4
+

MARINE ALGAL VEGETATION

51

Table 1. The Distribution of the Species along the coast (continued).

rs i

i

we

pels eriel eelleleleteelNok les). lee t=) (ee!

Punctaria plantaginea (c)............ |

kitosiphon filiformis (¢) 4...........-

Isthmoplea sphzrophora (c).......... |
Stictyostpbon .tortilis(c)......:...... !
Pheostroma pustulosum (c) ......... |

Scytosiphon Lomentaria c...........

Phyllitis zosterifolia (¢)......:....:.. |

BIAS CIA Cle Be hy ey oe ce ee ssi
Coillodesme ‘bulligeran) ©... 05s. o ss aes os
Dictyosiphon. Ekmani.... <6.) .. 4+ ce...
BPEMVESOCLOVA Sothern eo asics os ce se ee

Wathnordatia, (CO) sok. sos oe oe |

DACOnVMIDOSUS, 64! veka Sik eo we
Dei PUT OLAESs (GC)! ode vc we cs aie wn ake d
Dpocmienlaceus,(C). i... es ens ss
MICSHINARESUIAr VITIGES! Ce. ue. aa See oc nt al
DP ACMneaAba Ces Pe Sah. ts de ee ee

We lieulatas2 2.2... case Soke wah aah. secs Maks |
G@astagnea: viréscems (C) oi... 2.00. + i
-Leathesia difformis

* ete, (ee) 0) ey/e) fal) wp. 0 40) 4) sa) ©, ele

Chordaria flagelliformis c

eee es ee eo we ew ww

Ghordas tomentosa’ (G).. 0.0.20. 25%. |

CC) PDI ((O) 2 ee eee) a
Saccorrhiza dermatodea (c) ..........
PamimartaSaceharina Ci. .66 ue eee
MEPIEELOCIISIS tee Saya ade Phin ey ae we 8
Ue TUTTO OSS ee ch eae Ra
| 55, GIENICTIG SG ecg oP eo
EME ICE DOUCA, (6. fA che 5% ass0ye wiahtyeeeee in

PM MRA be RALU RG ee ite a o%e aye «ne eres 0%

PVPCSCUNGMEANC A, rk vi bic) ats .o sce es lene ee otis
RUCUS PS pIrAlisn(G) ike. ho. Se eee
STE ISOC ee ee EE

Chlorophycee.

Chlorochytrium Cohnii (¢).’.).....-...
Germelusiiaa (6). 2 vig Ge os ey ese ees ee Fs
ca dermatecolax (6)iid.i Gig. Wels a aie o's
Ge Senate CE). 5 .5s-eeiesls So aelated wes
Codioham. Petrocelidis: 20.0.5 wsh.. ss.»
CPs G SARC (CC) oe s-asm se ses oars 0s ose

|
| E. Icel.

+2: +4+4+4+4+4+4+4+

+++:

+:

fod: $t+4+tt++tt+stt+:

Gmomstilum (GC). eee cote ee cc es 8

N. Icel. |NW.Icel.|SW.Icel.| S. Icel.
+} +].
Se
2
+ + {+4
CVG he oe ae
+/4+)+]4
a
+ + 4 4

+) +
a +
ste 3
st -
Slips ete UI 2g
+ +/+ > 4
+ +/+.
+ + > 4+ +
+) +f) +] +
- oy. (oa
+ +
2 eae rete Se
+/+ ])4+)]+
+. +
+ + 4
+ +) 4...
+ +) +4 4
_
+ +) +) +4
+ + + 4
+) + 4+ 54
+ +) + 4
spi hacmaniaee 1a
+) +) 4+ 4+
pat ar aa ae
+) +] +i+
Bia | abe 0
+) +) 4+ 4+
re sy +
+} + | 4+
4 +
+
+-
+
4*

52 H. JONSSON

Table 1. The Distribution of the Species along the coast (continued).

E. Icel. | N. Icel. |NW.Icel.|SW.Icel.| S. Icel.
B, Percursatia,, percursa (¢) see ea Abe a.
D Enteromorpha aureola.)j9 ae + we =
De oR cimizaeee ee ee Ec, | eee eee EBD i y: Mk + =
C BE imtestimalis. c 472.96.) othe eer + a + — +
C EY clathir altar) (Cy ies, teak octane eer + + ne -. =
A Monostroma groenlandicum.......... + - 4. se big
B, MES Grevallei ens ©) ra alice eae -- + + + +
B, Mipuind ulate ete er nt one. ovate + + a. + +
B, NES PUSCW INC ee ee eo orn Ae +- + aL ~ +
C Wiva slactuica’ (G) yn cers. wee ae +- + a +
D Prasiola? polyrthizai(e).. 4. thet eer a fs + +
D Pp; furiiracean (oe. 7s 8. eee a era ee: a + + Me)
D Pistipibata’.(e) Mc. ny oe ee ete ae - | + + + +
B, Ulothrix consociata v. islandica. . J + wa
B, W..subilaccidat(e) im ache ante <2 av + + es ne
By Wipseudoilacca (Giese are tase + Hy + +
B, UAC Cach aaa Cee at eee weee | ob +) + + +
B, Pseudendoclonium submarinum (c)... + ig ;
D Entoderma Wittrockii (c)............ + + +
Bi Acrochwte parasitica: (6) a.via0..8 ee oe Me +
D A SREPEUIS Bapres 2 in, corps apes Sia Wen tvacoee aie af fs aa
B; Bolbocoleon: piliferunm (G)i.2 2.2. os. i od + + os re
B, Wivellattucicola (Ce 6 ae eee ok ai ve + +
B Pringshermuiacscutata (C)es: 25.5 aot ae + +
D Ochlochzeteferomi(G).. 0a. ft eee a, + - .
B, Urosporacmailralsilis cen eoiteece sr tenes + aL, + + +
B, LOAD CUS A SI (e) i wate os WA ICN NR Ss + i Nee + +
Bb, Ws Worniskioldiivenen sae sO: Ae on + =: + + 5
C Chetomorpha tortuosa (c)........... +. = dig + oe
B, C. Melagoniumme tao itera a.4c 2a eee ee os + + a
C, Rhizoclonium riparium (c)........... +- + aa
B, Spongomorpha vernalis (c)........... “ae ey Ad; +
D Acrosiphonia albescens c............. -+ == + + +
B, AS MCU MAC CRN. co oineiomenae an et ae + ok + + +
B, A Hy Strixcn(@) in chistes aa ag — + +- —_ oe
D A; flabeliittonmiste.. 3c) a eco ee ae +
B, A. peniciMORMIS eR : oe en we eee + eS BY os os
By Cladophorayrupestris icant ots. ha BA = + +
B; | Gahintay(On eee ee ee Cann i ae
B, CSericea (C) ee Ge Re ee ate + +
D Cuglaticescens (0) eae ok ee eee ts & +
C Gigracilis:(C) en wine. 6 eee cee + as Ke +
C Gomontia polyrrhiza (c) ............. a + + +
B, Ostreobium Queketti (CG). ss. + + + + |

MARINE ALGAL VEGETATION 53

Table 1. The Distribution of the Species along the coast (continued).

E. Icel. | N. Icel. [|NW.Icel.|SW.Icel.| S. Icel.
Cyanophycee. .
B, Pleurocapsa amethystea c............ ok aa = | + +
D Electonema norvesicum (c).........- — ae fe a
E Phormidium autumnale (c).......... ae owe we
C Spirmlina subsalsa (c)i 202... oe eh a2 aS +
C Calothrix scopulorum: (c)...2......2+ + - 1 a
C SAMARIA ALAN (G)) or) a 2 ob ele ek. cle a 8 ae - be: +

From Iceland (31, 14 and 57) there are published 76 species of
red alge, 67 species of brown, 51 of green and 6 af blue-green —
200 species in all. All of these, of course, are not equally common
along the coast, and their habitats, as far as these are known, in
the five districts into which the coast is divided, are given in the
above table. That table shows that comparatively few species occur
in all the coastal districts (in the table, such are indicated by the
letter c placed after the name of the species). In all parts of the
coast are found 15 species (20 °/o) of red algze, 18 species (26.8 °/o)
of brown, 10 species (19.6 °/o) of green and 1 species (16.6 °/o) of
blue-green. Thus, of the 200 species there are 44 species (22 °/o)
which are common to all the coastal districts.

If we take into consideration the fact that the great stretch of
coast round the whole of Iceland is as yet far from accurately investi-
gated, we may expect, after future investigations, not only that several
more species will be found, but also that the distribution of the
species in the different parts of the coast will prove to differ from
what is at present stated to be the case. Therefore, in the above
list of the distribution of the species along the coast I have placed
a (c) after the name of those species which, as I surmise, are pro-
bably to be found in all parts of the coast. I base this supposition
partly on the position of the habitats already known along the
coast, and partly on the occurrence of the species in the adjacent
floral districts, e. g. the Feerédes and Greenland.

The mark (c) is subjoined to 14 species of red alge, 29 species
of brown, 32 species of green and to 5 species of blue-green. On
adding to this the above-mentioned species which have the letter c
subjoined we get 29 species (38 °/o) of red algze, 47 species (70 °/o)

of brown, 42 species (82 °/o) of green and 6 species (100 °/o) of blue-
| green. Thus, of the 200 species 124 prove to be common to all parts

54 H. JONSSON

of the coast. The percentage of each group is of the greatest im-
portance, and for the sake of explicitness I have arranged these
figures in a tabular form, both those which refer to c and those
which refer to. c + (c).

Species common to all the coastal districts, given as
percentages.

Red Brown Green Blue-green All the groups
algze algze algze alge collectively
Ce a ae 20 27 19 17 22
C +-(€) sre 38 70 82 100 60

On considering these two series of figures it becomes evident
that the figures given for c + (c) come nearer to the real facts,
while those given for c merely indicate an incomplete knowledge
of the coastal distribution of the species. The fact is that, where
there is not a greater climatic difference between the different parts
of the coast than is the case in Iceland, it may always be expected
that, as regards the common species, the highest numbers will fall
to the green and to the blue-green alge; and where the hydrographic
differences between the different parts of the coast are as pronounced
as they are in Iceland, it is natural that the smallest number will fall
to the red algz, and just as naturally the brown alge will in this re-
spect be placed almost midway between the red and the green alge.

Therefore, as regards the floristic difference between the different
parts of the coast, particular stress is laid on the remaining 76
species. In the following table they are arranged according to their
habitats. Under A, those species are given which either occur in E.
or N. Iceland only, or are most common there, and thence are dis-
tributed southward along the north-west coast as far as SW. Ice-
land. Under B are given species which either have been found in
S. or SW. Iceland only, or are most common there, and thence have
a distribution northward along the north-west coast, many of them
having, moreover, an eastward distribution along the north coast.

Table 2. The Distribution of the 76 species not common to all
the coastal districts.

3 3\¢ a/s|3\¢
ae =
i) c) iP) o i?) Vv
A sf rm. | Sai oS (| Cee prea f= seal] psa wan tb sea B
— — = & — — — > = —
PT Ne az mz ee | el Z| a n

1. Lomentaria clavellosa
2. L. rosea
3. Plocamium coccineum

bar

1. Lithothamnion flavescens |

+

MARINE ALGAL VEGETATION 55

Table 2. The Distribution of the 76 species not common to all
the coastal districts (continued).

lee

pe ap aie) eal eee ah mi gee
x $| 3) 2) 2| 2/3) 2) 2) 8) 3 3
colt tc dle |e ere =
|
2. Omphalophyllum ulva- | ? | 4. Bonnemaisonia aspara-

SES oy. oy ear airs ORT Paste goides
5. Pterosiphonia parasitica
6. Rhodochorton repens

3. Laminaria nigripes ..... SriSredcoe ecu eeee TMP linea eoe HOR pOIN Uae!
phum
4. Acrosiphonia penicilli- 8. Myrionema Corunnze
PED AA AA oo a + | 9. Ectocarpus Hinksize
|. 10. Desmarestia ligulata
5. Delesseria Baerii........ ae: | 11. Acrosiphonia flabelliformis

1 | 12. Porphyropsis coccinea
| 13. Chantransia Alariz

6. Turnerella Pennyi Sioa op eee + + 14. Phyllophora membrani-

folia

Ftttttt+ t+t+++++ 4444444 +44

7. Lithothamnion foecun- 15. Delesseria alata
APG | 3.7. fy thr al Re . Callithamnion Arbuscula
17. C. scopulorum
ae Ae 18. Plumaria elegans
8. Laminaria feroénsis. ../+ + ).. IEA a eee ta A
| 20. Cruoria pellita
9. Petroderma maculiforme.,..|-+)|.. 1 21. Dermatolithon macro-
1 carpum
10. Ascocyclus islandicus .. +).. | | 22. Ectocarpus tomentosus
23. E. fasciculatus
, A ; 24. Fucus serratus
11. Dictyosiphon Mesogloia.. + ).. ! 5b. Pele ctandanticulota
| | 26. Enteromorpha Linza
a2 DL CorymbpOsus........... + ).. | 27. Ceramium Deslongchampii
28. C. atlanticum
- || 29. C. fruticul
13. Enteromorpha aureola . ae we apie Hs

30. C. circinnatum

- |31. Rhodochorton minutum

- || 32. Dilsea edulis

- | 33. Lithothamnion Lenor-
mandi

34. Myrionema fzroénse

14, Ulothrix consociata v. is-| ee
EVI? 0 aia ee a

+++++tt+ F+tt+ttetts++ F444444+ +44:

42. Acrochzte repens

cir 2 ae bet + 35. Dictyosiphon Ekmani
Aine -- || 36. Codiolum Petrocelidis
- +4) + ||37. Chondrus crispus
Soe otal) Brodist:., v. 45/35 |-Hlgs\pelysiphotiia fstigiata
“IME 2ST ae a lala dl + | + | 39. Rhododermis parasitica
+ + | 40. Sphacelaria olivacea
17. Actinococcus subcutaneus | + | .. | +- + =| 41. Cladophora rupestris
a

56 H. JONSSON

Table 2. The Distribution of the 76 species not common to all
the coastal districts (continued).

A al} 2|2| 2] ole lz FE] ui i
18. Ceratocolax Hartzii..... +. | +);+/+ ..|43. Ceramium arborescens
| | . Dob 4+ +) 44. Ahnfeltia plicata
19. Polysiphonia arctica .... |/4+/)/+)+/+.. |. +/)+')+ | +-| 45. Cystoclonium purpura-
| yee scens
20. Ptilota pectinata........ +)+)+)+)..]).:}/4+:)+|+| +146. Ptilota plumosa
Ra .. +/+ > + +47. Petrocelis Hennedyi
21. Peyssonellia Rosenvingii. | + + |-+ |-+- .. +/+) + +) 48. Corallina officinalis
| - +/+)... |) --) 49. Lithophylum Crouani
22. Coilodesme bulligera.... |) ..)+)+ | ..i/+)..) +) .. || 50. Polysiphonia nigrescens
eye af-| 51. Myrionema vulgare
23. GEOriA, arctica nn jsvarten.s Bi 2 a a eet + ..| 52. Leathesia difformis
| (+)).. + +) 53. Delesseria sanguinea
Total... 15/13] 8 | 5° ..|| 1 |10|13| 40; 40] Total

To illustrate more distinctly how the species with a north-
eastern distribution (A) and those with a south-western distribution
(B) intermingle in N., NW. and SW. Iceland I subjoin the following
figures taken from the preceding table: —

E. Icel. N. Icel. NW. Icel. SW. Icel. S. lcel.
Ge) 10 13 40 40 B
A 15 9+4 8 5

Notes on the species. Of the 4 species (A, 1—4, Tab. 2)
which have been found only in E. Iceland, Nos.1 and 3 occurred
in great abundance in several of the fjords, while Omphalophyllum
was found only in Reydarfjéréur, where it occurred abundantly,
and Acrosiphonia in one place only. Delesseria Baeriti, I suppose
(31, p. 140), has originated from either E. or N. Iceland.

Turnerella is most common in E. Iceland, and in addition to
the habitat in N. Iceland which has been published (31, p. 135) has
been found by B. Semundsson in Steingrimsfjéréur in the most
western part of the north coast; consequently it must have a wide
distribution along this coast. With regard to Lithothamnion foecun-
dum and Laminaria feroensis it must be assumed that they are
more frequent in E. and N. Iceland than is known at present, and
as the latter species occurs in the Feerées, it may well be expected
to be met with on other parts of the coast of Iceland.

MARINE ALGAL VEGETATION 57

With respect to the 6 species (A, 9—14) which have been found
only in N. Iceland, it cannot be assumed that they are confined to
the north coast, and it is highly probable that they have a much
wider distribution on both sides. Dictyosiphon corymbosus and Ulo-
thrix consociata v. islandica must, however, be assumed to belong
more closely to E. and N. Iceland.

As regards the 8 species (A, 15—22) which occur so far west
or south as NW. Iceland or SW. Iceland, it must be supposed that
their absence trom N. Iceland (and E. Iceland /Ceratocolax, Cruoria/)
is due merely to insufficient knowledge regarding their distribution.
Of these species, those which extend to SW. Iceland have not been
found, however, further south than in Breidifjéréur, with the ex-
ception of Peyssonellia which has been found in Faxafléi near -
Reykjavik.

Of the species given under A, Nos. 1—8, 12 and 14—23 must
consequently be supposed to have an east-northward distribution
along the coast of Iceland, while Nos. 9, 11 and 13 must be sup-
posed to have some other principal distribution; one species (10) is
endemic in the most western part of the north coast.

Under B, 53 species are recorded. Of these 10 have been found
only in S. Iceland, the majority of these in the Vestmannaeyjar
only; to these must be added Bonnemaisonia (31, p. 141) which I
believe to have been found in S. Iceland. That is, 11 species in all,
one of which, however, Rhodochorton repens, is endemic. 17 species
have been found only in S. and SW. Iceland (B, 12—28) and 8 species
in SW. Iceland only. Thus, there are in all 36 species which are
known from S. and SW. Iceland only. 6 species (B, 37—42) have a
more northern distribution, as they have been found in NW. Ice-
land. Consequently, there are 42 species which are known only
from S. and W. Iceland (NW. Iceland included), but of these species
there are two, Cladophora rupestris and Codiolum Petrocelidis which
probably have a more northern distribution. 10 species (B, 43-52)
which have principally a south-western distribution (the fact that
some of them have not been found in NW., SW. and S. Iceland is
probably due to insufficient knowledge regarding their distribution)
have been found also in N. Iceland. But all these species do not
reach eastward along the north coast to the same extent, Ptilota
plumosa and Corallina officinalis have been found furthest east in
the eastern part of the north coast; Lithophyllum Crouani and
Myrionema vulgare in Eyjafjéréur; Ahnfeltia and Petrocelis extend to

58 H. JONSSON

Skagafjéréur; while Cystoclonium, Polysiphonia nigrescens and Leathesia
do not extend further than the most western part of the north
coast (the small fjords in Hunafldi). Only Delesseria sanguinea now
remains; strictly speaking, this appears to belong to the south and
south-west coast, but has on one occasion been found in E. Iceland,
cast up on the shore. It did not appear to have come from a
distance, and it probably grows there, though I did not come across
it in the dredgings.

Thus all these 53 species have on the whole a southern and
western distribution in Iceland.

The above shows that there is a large neutral territory where
the species with a south-western and those with a north-eastern
distribution meet and intermingle. This boundary area comprises
almost the whole of the north coast, the north-west fjords and, to
a certain extent, the northern part of the south-west of the country.
(For further details see below under the Floristic Boundaries.)

THE COMPONENTS OF THE ALGAL FLORA.

At present 200 species of Marine Algze are known from Iceland.
In the plant-geographical groups established by Bérgesen and my-
self (B6rgesen and Jénsson, 14) these are distributed in the
following manner. The definition of the groups is here reproduced
almost literally from the publication mentioned.

A. The Arctic Group.

The species of this group belong to the arctic area of the sea.
The southern limit of this area extends from the north and east of
Norway southward to the south-east point of Iceland, where the
boundary is sharply defined. From E. Iceland the boundary line
extends to the north of Iceland between Iceland and Greenland,
and then turns considerably southward to the North Atlantic coast
of America. The flora of the boreal area of the Atlantic passes
without any distinct limit into the arctic algal flora on both sides
of the Atlantic. In Iceland the limit is distinct only at the south-
east point whereas the boundary is very indistinct on the north-
east part of the coast.

Some of the species of this group occur, but only rarely,
south of the border-zone.

MARINE ALGAL VEGETATION 59

Rhodophycee.

Ceratocolax Hartzii.
Turnerella Pennyi.

Delesseria Baerii * corymbosa.
Polysiphonia arctica.

Cruoria arctica.
Lithothamnion flavescens.
L. foecundum.

Pheophycee.

Omphalophyllum ulvaceum.
Dictyosiphon corymbosus.

Laminaria nigripes.

Chlorophycee.

Monostroma groenlandicum.

B. The Subarctic Group.

Subdivision I.

The species of this subdivision are common in the Arctic Sea,
and are rather common in the cold-boreal area of the Atlantic Ocean
as far south as the Ferédes and Nordland; some of them occur,
although rarely, as far south as England.

Rhodophycee.

Rhodophyllis dichotoma.
Halosaccion ramentaceum.
Ptilota pectinata.
Rhodochorton penicilliforme.

Peyssonellia Rosenvingii.
Lithothamnion tophiforme.
i leeve:

Clathromorphum compactum.

Pheophycee.

Lithoderma fatiscens.

Ralfsia ovata.

R. deusta.

Myrionema globosum.

M. Laminarie.

Streblonema ecidioides.
Sphacelaria britannica.

Cheetopteris plumosa.
Coilodesme bulligera.
Saccorrhiza dermatodea.
Laminaria fzr6oensis.

L. digitata.

Alaria Pylaii.

Chlorophycee.

Chlorochytrium Schmitzii.
Monostroma undulatum.

M. fuscum.

Ulothrix consociata v. islandica.
U. subflaccida.

U. pseudoflacca.
Acrocheete parasitica.
Urospora Hartzii.
Acrosiphonia hystrix.
A. penicilliforme.

Subdivision II.

This subdivision includes species, which are either common
in the Arctic Sea and the North Atlantic from western France—
England northward, or which, if not common, are at least all
equally frequent.

60 H. JONSSON

Rhodophycee.
Porphyra miniata. Rhodymenia palmata.
Conchocelis rosea. Delesseria sinuosa.
Chantransia virgatula. Rhodomela lycopodioides.
Phyllophora Brodizi * interrupta. Odonthalia dentata.
Actinococcus subcutaneus. Ptilota plumosa.
Euthora cristata. Lithothamnion glaciale.
Pheophycee.
Ralfsia clavata. Phzostroma pustulosum.
Ectocarpus tomentosoides. | Dictyosiphon hippuroides.
Leptonema fasciculatum v. subcylin- D. foeniculaceus.
drica. Desmarestia viridis.
Elachista fucicola. D. aculeata.
Punctaria plantaginea. Chordaria flagelliformis.
Litosiphon filiformis. Chorda tomentosa.
Isthmoplea spherophora. C. filum.
Stictyosiphon tortilis. Fucus inflatus.

Chlorophycee.

Chlorochytrium Cohnii. Pringsheimia scutata.

C. inclusum. Urospora mirabilis.

C. dermatocolax. U. Wormskioldii.

Codiolum gregarium. Chetomorpha Melagonium.

Percursaria percursa. Spongomorpha vernalis.

Monostroma Grevillei. Acrosiphonia incurva.

Ulothrix flacca. Cladophora rupestris.

Pseudendoclonium submarinum. C. hirta.

Bolbocoleon piliferum. C. sericea.

Ulvella fucicola. Ostreobium Queketti.
Cyanophycee.

Pleurocapsa amethystea.

C. The Boreal-Arctic Group.

The species of this group are common in the Arctic Sea and
the boreal area of the Atlantic at least as far south as the Atlantic
coast of North Africa; probably some of them have a far greater
southern distribution. Some of them might possibly be considered
cosmopolitan. |

Rhodophycee.
Bangia fuscopurpurea. Antihamnion Plumula v. boreale.
Porphyra umbilicalis. Ceramium rubrum.
Chantransia microscopica. Rhodochorton. Rothii.
C. secundata. R. membranaceum.

Ahnfeltia plicata. Hildenbrandia rosea.

MARINE ALGAL VEGETATION 61

Pylaiella littoralis.
Ectocarpus confervoides.
E. siliculosus.
Scytosiphon Lomentaria.

Enteromorpha intestinalis.

E. clathrata.
Ulva lactuca.
Chetomorpha tortuosa.

Spirulina subsalsa.
Calothrix scopulorum.

Pheophycee.
Phyllitis fascia.
Fucus vesiculosus.
Ascophyllum nodosum.

Chlorophycee.

Rhizoclonium riparium.
Cladophora gracilis.
Gomontia polyrrhiza.

Cyanophycee.

Rivularia atra.

D. The Cold-Boreal Group.

The species of this group have their area of distribution from

western France—England northward to S. Iceland,

the FeerG6es

and Nordland—Finmark. Some few species have occasionally been
found in the Arctic Sea, especially in the White Sea and the
Murman Sea, and some few reach as far south as the Mediterranean

and North Africa.

Porphyropsis coccinea.
Chantransia Alariz.
_ Gigartina mamillosa.

Phyllophora membranifolia.
Cystoclonium purpurascens.

Lomentaria rosea.
Delesseria alata.

D. sanguinea.
Polysiphonia urceolata:
P. fastigiata.

P. nigrescens.
Callithamnion Arbuscula.
Plumaria elegans.
Antithamnion floccosum.

Ceramium acanthonotum.

C. Deslongchampii.

Petroderma maculiforme.

Ralfsia verrucosa.
-Myrionema vulgare.
M. Corunne.

M. feerodense.

Rhodophycee.

Ceramium fruticulosum.

C. circinnatum.

C. altanticum.

Rhodochorton repens.

R. minutum.

Dumontia filiformis.

Dilsea edulis.

Petrocelis Hennedyi.
Rhododermis parasitica.
Lithothamnion Ungeri.

L. Lenormandi.
Phymatolithon polymorphum.
Lithophyllum Crouani.
Dermatolithon macrocarpum.
Corallina officinalis.

Phzeophycee.

Ascocyclus islandicus.

Microsyphar Polysiphonie.
Streblonema Stilophore v. czespitosa.
Ectocarpus tomentosus.

E. penicillatus.

62 H. JONSSON

Ectocarpus fasciculatus. Castagnea virescens.
E. Hinksie. Laminaria saccharina.
Sphacelaria radicans. L. hyperborea.
S. olivacea. Fucus spiralis.
Phyllitis zosterifolia. F. serratus.
Dictyosiphon Ekmani. Pelvetia canaliculata.
D. Mesogloia. Alaria esculenta.
D. Chordaria.

Chlorophycee.
Codiolum Petrocelidis. Entoderma Wittrockii.
C. pusillum. Acrochete repens.
Enteromorpha aureola. Ochlocheete ferox.
Prasiola polyrrhiza. Acrosiphonia albescens.
P. furfuracea A. flabelliformis.
P. stipitata. Cladophora glaucescens.

Cyanophycee.
Plectonema norvegicum.

E. The Warm-Boreal Group.

The majority of the species referred to this group extend at least
as far south as the Mediterranean and the Atlantic coast of North
Africa. According to the different distribution northward the group
is divided into three parts of which only the one reaches as far
north as S. Iceland.

1. Species extending as far north as S. Iceland, the Ferées and
Northern Norway, and at least as far south as the Mediterranean
and North Africa.

Rhodophycee.
Chondrus crispus. Callithamnion scopulorum.
Lomentaria clavellosa. Ceramium arborescens.
Plocamium coccineum. Cruoria pellita.

Bonnemaisonia asparagoides.
Pterosiphonia parasitica.

Pheophycee.
Desmarestia ligulata. Leathesia difformis.
Chlorophycee.
Enteromorpha Linza.
Cyanophycee.

Phormidium autumnale.

According to the above the number of species in the groups Is
as follows: — |

MARINE ALGAL VEGETATION 63

Rhodo- Phzeo- Chloro- Cyano-
phyceze phyceze phyceze phyceze

ine arctic sroup..... J J 1 >» =11species (5.5°/o)
2. The subarctic group:

Subdivision I.:...... 8 13 10 mo == SA (155° /0)
3. The subarctic group:

Subdivision Il....:.. 12 19 20 1 = 50° — «(25.09 /o)
4. The boreal-arctic group 10 7 ji Br aaa Dey em. Aye gy)
5. The cold-boreal group. 31 25 12 ti 690-450)
6. The warm-boreal group 8 2 i Bo 12 = (G08 /p}

76 67 51 6

If we divide the six groups into two parts, A: the first three
groups, and B: the last three! groups, we obtain the following
figures: —

A, 92 species (46 °/o) and B, 108 species (54 °/o).

The floral district must therefore be determined as boreal, be-
cause more than half of the species belong to the last three groups.
Of these groups the cold-boreal is the most important because its
species form 64°/o of the total number of species (108) in all three
groups. This floral district has not, however, a purely boreal cha-
racter, as the subarctic group is rich in species and gives a rather
high percentage (41 °/o). The floral district, then, is characterized to
a very high degree by a boreal element, and next by a subarctic
element.

If we consider only the red and the brown algz, 143 species
in all, the cold-boreal character is a little more strongly pronounced
than the subarctic. The figures are: — Arctic 10 species (7 °/o), sub-
arctic 50 species (35 °/o), boreal-arctic 17 species (12 °/o), cold-boreal
56 species (39 °/o) and warm-boreal 10 species (7 °/o). The first three
groups have 60 species (42 °/o), the last three 78 species (58 °/o).

If we compare the five divisions of the coast with respect to
the number of species in the different groups, we obtain the figures
given in Tables 3, 4. |

If, for instance, we select the red and the brown alge (Table
4) as a basis, then the difference which exists in the different parts
of the coast is very evident. In E. Iceland the arctic group contains
the greatest number of species, and this number — if we follow
the divisions of the coast in the order of the tables — decreases

1 The boreal-arctic group is included in the boreal groups, as its species,

though common in the arctic district, have a far larger area of distribution out-
side this.

64 H. JONSSON

Table 3. Red alge, Brown alge, Green algz, Blue-green alge

collectively.
| !

E. Icel. N. Icel. NW. Icel. | SW.Icel. | S. Icel.

a 3g 3| = s ees site
ESS; % | 9°38) % Eos % Eos % | §°3 %y
Z a | 4 zal iA a Za zy Oo :
Arctic group... 0. tne. 8 | 7 SP ek 3 3 2 1 > >
Subarctic group I...... 25 22 2 20 VGA abil 2 ie ee 12)
Subarctic group Il..... | 38| 34] 37] 30].39 | 41,]| 44] 98 | Om eae
Boreal arctic group....! 20 | 18 260° Deal 1G Ly 23 | 15 16 |} 15
Cold-boreal group...... | 20 | 18] 29.| 24] 18 | 20] 53] 34 | 43 | 39
Warm-boreal group....| 1 ¢1) 2 |e Pa Bi crap a ea 4 9 9

aa eee a
Total, | 2) aes hh aa 155 108

Table 4. Red and Brown alge collectively.

Tl I 3
| E. feel}. Nueel... ||, NWi cel, |) SW. Teel.) Siieet
(2.2 o/ \3_2 0 2.2 0 \3.3 0 ER 0/
|Eog /o Beg /o Fog lo Sor lo 5 Ome
1A @ Zw a @ ae a3 Cae
Arctic proup.) i.a04e00) Wes} 8 | 4] 5 | 2y)'| wes epee 2 > >
Subarctic group 1...... | 18 | 23 | 19 | 22 093 | 18 |, 200) am 8 | 10
Subarctic group II..... | 25 31 24 28 Dias 37 26 | 23 17) 20
Boreal arctic group.... | PS A DGrs te LT | 19. || 13.) 18. |. 2G.) TASS ies | 15
Cold-boreal group...... | 17, | 21 | 21.) 24]. 16 | 92 || .46 | AON eee
Warm-boreal group....| > > Dea a hy ao eee 8 10
| | | | |
Total...) 80 | 87 [pda anes | 8 |

uniformly in the other parts of the coast, and is reduced to 0 in
S. Iceland. In E., N., NW. and SW. Iceland the number of the
species in the subarctic group I is practically identical in propor-
tion to the number of species, taken as a whole, in these parts of
the coast; S. Iceland has a distinctly smaller number, only 10 °/o.
The subarctic group II is represented most abundantly in NW. Ice-
land; E. and N. Iceland come next; but S. and SW. Iceland have
a considerably lower percentage (about 20 °/o). The percentage in
the boreal-arctic group is practically identical in all parts of the
coast. The cold-boreal group presents almost the same percentage
in E., N. and NW. Iceland, while the percentage in the group in

MARINE ALGAL VEGETATION 65

SW. and S. Iceland is almost double this. The warm-boreal group
is not represented in E. Iceland, and only with extreme rarity (1
species) in N. and NW. Iceland. SW. Iceland has only 4 species,
while S. Iceland has 8 (10 °/o).

There is a very great similarity between S. Iceland and SW.
Iceland, if the arctic group in SW. Iceland is excluded; on the other
hand, the difference is greatest between E. Iceland and S. Iceland,
as is shown by the following figures: —

East Iceland South Iceland

PRE? OROMG coco. gcse: 2. fe ts 9 %/o 0 °/o
subarctic eroups 20h. 54 %/o 30 °/o
Boreal-arctic ‘group's ...) 0.0 - 16 °/o 15 %/o
Cold boreal erowp i, .yii./.\s.. 08 eee os 7 Veer fe 45 °/o
iiamn-boreal Sronp . 0 o6 cj... 0 °%/o 10 °/o

If we assume that the species marked (c) (Table 1) are to be
considered as common to all parts of the coast (see above), the
distribution of the 76 not-common species becomes decisive with
reference to the floristic difference between the parts of the coast.
In the following table, therefore, it is shown how these 76 species
are arranged in the six plant-geographical groups of alge.

Table 5. Group-division of the 76 not-common species (see Table 2).

A E. Icel. | N. Icel. [NW.Icel.|SW. Icel.| S. Icel. | B

\|

| Arctic group.

MECC STOUP ......-.- 8 5 3 DAs }
se hate | | Subarctic group I.
Subaretic group I.... || 5 3 EL. me ae
| 1 7st ane 2 | Subarctic group II.
Subarctic group II1.... 2 Be 2 |
lip, oat 1 LES ar 1 | Boreal-arctic group.
Boreal-arctic group... | .. a BPS NG m|
hea oa 6 8 31 | 28 | Cold-boreal group.
Cold-boreal group .... is 4 ee | |
2 2 6 9 | Warm-boreal group.

Warm-boreal group... ae Si i oe am ial
f 10 13 40 | 40 | Total number ofspecies
Total number of species | 15 (9 +4 Sip ly 25

16 23 21 | 45 | 40

|

The figures in this table show what has been already shown
by those which I have given in Tables 3 and 4; but the arctic

The Botany of Iceland. I. 5

66 H. JONSSON

element in E. Iceland and the boreal element in S. and SW. Iceland
are much more sharply defined; and this is natural, as the species
assumed to be common are omitted. Even if we consider: only the
known distribution of the species, in its entirety (see Table 1), the
distribution of the here-mentioned 76 species will still be the most
essential reason for the floristic difference between the parts of the
coast.

The species assumed to be common are 124 (see above). Of
these none are arctic, 25 belong to the subarctic group I, 46 to the
subarctic group II, 26 are boreal-arctic, 26 cold-boreal, and one
(Phormidium autumale) is warm-boreal. Of the 76 not- common
species, 11 are arctic, 6 belong to the subarctic group I, 4 to the
subarctic group II, one (Ahnfeltia plicata) is boreal-arctic, 43 are
cold-boreal and 11 warm-boreal. If we add together the numbers
representing the species of the corresponding groups as regards the
124 species assumed to be common and the 76 not-common species
(Table 5), and compare with Table 3, we find that the species are
more numerous in each district, but that the percentages are almost
the same.

If the groups are divided in two parts, A and B (see above) so
that A includes the arctic and subarctic groups, and B the three
other groups, the following figures are obtained (see Table 4): —

E. Icel. N. Icel. NW, Icel. SW. Icel. S. Icel.
A:... 50(63%o) 47(54°%/o) ~ 42:68 °%/0) 48:42 %o) Seana
B.... ) 30(87.%/0) 40 (46 °%/o) 31 (42%) 67 (58/0) aOrG@ te a

The arctic group is poorly represented in all the districts of
the coast (see Table 4) and therefore the figures mentioned above
under A apply chiefly to the subarctic group; the floral districts of
KE. Iceland, N. Iceland and NW. Iceland are thus subarctic. E. Ice-
land is subarctic to a greater extent than N. and NW. Iceland. SW.
Iceland is a boreal floral district with a very considerable subarctic
element, and thus resembles the coasts of Iceland taken as a whole
(see above). S. Iceland is a boreal district with a slightly subarctic
element.

Floristic Boundaries.

The mixed character of the flora in N. and NW. Iceland has
been alluded to several times in the foregoing pages, and is clearly
seen from the tables given, as, for example, Tables 2 and 5. Here

; b)

MARINE ALGAL VEGETATION 67

neither, is any distinct boundary found between the boreal and
subarctic floral districts, and the north and north-west of the country
must, strictly speaking, be considered a large boundary-area, a view
which accords well, also, with the hydrographic conditions. Here,
the boreal, subarctic and arctic species intermingle.

At the south-eastern point of Iceland there is, on the other
hand, a rather distinct hydrographic boundary along the stretch
from Vestrahorn to Eystrahorn (or Lonsheidi). The greater part
of this coast is sandy, and difficult of access for the investigation
of the algal vegetation. From my own observations I can only say
that Berufjordur, the most southerly point in E. Iceland which I
have examined with regard to its algal vegetation, has a cold-water
flora, and that the Vestmannaeyjar, the most easterly locality on the
south coast which I have examined for the same purpose, have a
warm-water flora. The boundary must lie between them, and I
conclude, especially from the hydrographic conditions and the dis-
tribution of the Plankton-associations, that it is situated just on the
stretch of coast already mentioned. Ove Paulsen (55 and 56) has
given valuable information respecting this boundary, and it is
evident from his investigations that the boundary varies to a slight
extent, the facts being that in May-June it has been found in the
vicinity of Eystrahorn (see 55, map J), but in July-August at Vestra-
hern (see 55, map Ii). If alge grow on this stretch of coast, one
may conclude that there exists a mixed flora resembling that of
N. and NW. Iceland. Whether boreal species can be carried to E.
Iceland in this manner is at present not easy to say with certainty,
yet it seems to me that the occurrence of Dumontia filiformis and
Delesseria sanguinea, both of which are absent in N. and NW. Ice-
land, can be most easily explained in this way.

IV. COMPARISON WITH NEIGHBOURING
FLORAL DISTRICTS.

l° Table 61 is given a survey of the plant-geographical distribu-
tion of red and brown alge collectively, in certain subarctic
and boreal floral districts. These are so arranged that those
floras with the largest arctic element stand furthest to the left. The
arctic and subarctic percentages decrease while the boreal percentage
increases to the right. The boreal-arctic group is practically similar
everywhere, which is also natural according to the geographical dis-
tribution of the group. The warm-boreal group is not represented
in the subarctic floras, and the arctic group is quite infinitesimal
in SW. Iceland and Nordland, and is entirely absent from S. Iceland
and the Feerédes. In regard to species, the cold-boreal group is ex-
tremely poor in East Greenland and Spitzbergen, somewhat richer
in West Greenland and considerably richer in E. Iceland.

By grouping the species, as is done above (cf. B6rgesen and
Jonsson, 14), the character of the floral districts can be deter-
mined according to those groups which are richest in species. Thus,
I characterize a group as subarctic when more than half of its
species are reckoned to the subarctic group. In a similar manner a
district is boreal when more than half of its species belong to the
boreal groups (bor. arct., cold-bor., and warm-bor.).

Similarly, in an arctic district the species belonging to the arctic
group must constitute more than half of the number of species be-
longing to the district, and, in addition to the subarctic group, only
the boreal-arctic will be represented. Of the floral districts men-
tioned by Bérgesen and Jénsson (14) none are arctic according

* With the exception of Iceland the numbers of the species of red and brown

alge are taken from Bérgesen and Jénsson l.c. (14, p. 22). In regard to East -

Greenland the numbers are corrected according to Rosenvinge (64), and to West
Greenland two species have been added: Ectocarpus maritimus and Chantransia
collopoda.

\

H. JONSSON: MARINE ALGAL VEGETATION 69

to the definition here employed. The Siberian Sea, however,
comes nearest to it. From here 23 species are known (14), of
which 9 (39 °/o) are arctic, 11 (48 °/o) subarctic and 3 (13 °/o) boreal-
arctic. This district is at the boundary between arctic and sub-
arctic. Regarded superficially it may appear strange that none of
the districts are arctic, but on closer inspection this is easily under-
stood, the reason being that some of the districts (14) are too large
and consequently acquire a mixed character. In this respect I shall
merely point out, for instance, that both Spitzbergen and East
Greenland (and probably West Greenland) ought to be divided into
two districts.

As already mentioned, none of the districts recorded in Table 6
is arctic. East Greenland, Spitzbergen and West Greenland have almost
the same percentage as regards the arctic species (Table 6), and as
this percentage is rather high in proportion to that of the boreal
species, these districts could be termed arctic-subarctic, in contra-
distinction to E. Iceland where the arctic percentage is four times
less than the percentage of the boreal species. The boreal districts
recorded here (Table 6, p. 70) should, strictly speaking, be called
cold-boreal.

If we call the first three groups (in Table 6) A and the three
last B the percentages will be as follows: —

E.Greenl. Spitzb. W.Greenl. E. Icel. Finm. SW.'Icel. S. Icel. Feer. Nordl.
| ee, a 81 ra 72 63 46 42 30 29 20
Boe ee. : 19 23 28 ah 54 28 70 @1 73

As the table shows, SW. Iceland agrees most closely with Fin-
mark, while S. Iceland and the Ferdées are nearly alike, as Borge-
sen (12, p. 804) also supposes.

If we take Iceland as a whole, we get 143 species (red and
brown alge collectively), 10 (7 °/o) arctic, 21 (15 °/o) subarctic (sub-
division I), 29 (20 °/o) subarctic (subdivision II), 17 (12 °/o) boreal-
arctic, 56 (39 °/o) cold-boreal and 10 (7 °/o) warm-boreal. These figures
are almost the same as those given for Finmark (see Table 6) and
differ, essentially from the figures given for SW. Iceland,. only
by the higher percentage of arctic and warm-boreal species. If, on
the other hand, we take the first three groups collectively and
the three last groups in a similar manner, we obtain the same
percentages as for SW. Iceland. On combining different parts of the’
coast, as for instance, E. Iceland and N. Iceland, we get almost the

in certain Subarctic and Boreal flora! districts.

Table 6. Distribution in groups of Red and Brown algz collectively

ATGUE-SLOUP: oe). «ec. ee:
Subarctic group I.....

Subarctic group II....

la

H. JONSSON

Subarctic group I-+ II
Boreal-arctic group....
Cold-boreal group.....

Warm-boreal group...

70

Subarctic

Boreal

East Spitz- West . : : hes,

Grecai: bergen Crean 3 E. Icel. Finmark || SW. Icel. S. Icel. Feer oes Nor dland
mf Be an ar my ee oA een Bon ean eae)
oe a4 alee oe Blac ae Bless a8 ee
Bee) Mo ESR) Mo ESR Me BS) Mh | Ser Eee Peel eee a) Le el
Zz 2 Zoe inna Z 2 Za 2 Zo a Z 2 Ze 7. ye)

. 15 18 10 7 18 9 y 6 2 2 ae Bm Kg eae 1 1
; 26 30 14 2S} 26 Te Oe [erty 20 | 17 8 10 14 9 12 | 10
: 28 33 22 oY 28 St 29m 23 26 | 23 lye 20 31 | 20 20 | 16
‘ 54 63 36 60 54 54 50 | 40 46 | 40 25 30 45 29 Se exh)
: 12 14 i) 15 16 16°] 18) 14 16 | 14 13 15 Lee ae 16 | 13
‘ 4 5 5 8 12 21 45 | 36 46 | 40 38 45 15a) Ad 61 | 49
5 Ber = tM ”, sae bie 5 4 5 4 8 10 20 | 13 Spel
Total. 85 60 125 115 84 157 123

eS eS SS SS SE SS SS

1 According to Petersen ‘57) 2 species of Ceramium (C. Areschoughii [assigned to the subarctic group II] and C. septentrionale
[assigned to the arctic group|) have here been added to West Greenland. To the Ferées have been added Ceramium Boergesenti and

Ceramium atlanticum, both of which I assign to the cold-boreal group.

MARINE ALGAL VEGETATION Eig |

same figures as for E. Iceland, and on combining NW., SW. and
S. Iceland we get almost the same figures as for SW. Iceland. E.
Iceland and N. Iceland have 101 species of red and brown alge
collectively. Of these 8 (8 °/o) are arctic, 20 (20 °/o) subarctic (sub-
division I), 28 (27 °/o) subarctic (subdivision II), 17 (17 °/o) boreal-
arctic, 26 (26 °/o) cold-boreal and 2 (2 °/o) warm-boreal. NW., SW.
and S. Iceland have 131 species of red and brown algz collectively.
Of these 3 (2 °/o) are arctic, 20 (15 °/o) subarctic (subdivision I), 29
(22 °/o) subarctic (subdivision II), 16 (12 °/o) boreal-arctic, 53 (41 °/o)
cold-boreal and 10 (8 °/o) warm-boreal.

As regards the components of the flora, both Iceland taken as
a whole, and SW. Iceland resemble Finmark; S. Iceland resembles
the Fer6ées and Nordland, and E. Iceland resembles the White Sea.!

It is evidently not.due to chance that the resemblance of the
floral districts happens thus. The situation of Iceland just south of
and at the boundary between the arctic and the cold-boreal districts
corresponds exactly with the situation of Nordland—Finmark— White
Sea in relation to this boundary. Iceland and the White Sea are
at the boundary itself, and in Finmark it certainly will be possible
to distinguish parts of the coast with a similar mixed flora as in
N. and NW. Iceland; the southern part of Finmark will then be
something like SW. Iceland, while S. Iceland, as already mentioned,
corresponds with Nordland.

This comparison shows only the relation between the quantity
of the species of the floral districts within the different groups, but
gives no information as to how far the species are common to all
those districts. Then it remains to be investigated how many species
Iceland has in common with the other districts. At the present
time a comparison of the floras will, however, scarcely give any
satisfactory results, because all the districts in question are not
equally well-known. By future investigations a greater number of
species will unquestionably be found in the majority of the floral
districts, and the quantity of the species will thus be altered, but
the relation between the number of the species of the different
groups will, however, undoubtedly remain unaltered.

1 According to Bérgesen and Jénsson (14) 52 species are known from the
White Sea, of which 3 (6 °/o) are arctic, 10 (19 %/o) subarctic (subdivision I), 19
(37 %/o) subarctic (subdivision II), 8 (15 %/o) boreal-arctic and 12 (23 °/o) cold-boreal.
The subarctic species constitute 56 °/o of the entire number of species and the

character of the flora is consequently subarctic in the same degree as that of E.
Iceland.

72 H. JONSSON

If we compare S. Iceland and the Fzrées with regard to common
species, the following figures are obtained: —

South Iceland 84 species? The Feer6es 157 species
not common common not common
10 (6 °/o) 74 (44 °/o) 83 (50 °/o)

Here it should be noted that S. Iceland is so very little known
that one is scarcely justified in comparing it with such a well in-
vestigated district as the Ferées. Many of the species which in this
respect are peculiar to the Feerdes will certainly be found in S.
Iceland and, at any rate, 32 of them are known from other parts
of Iceland, principally from SW. Iceland.

If we choose a larger district of the coast of Iceland, for in-
stance, the boreal district (S. Iceland and SW. Iceland) for compa-
rison with the Ferées, the following figures will be obtained: —

S. and SW. Iceland 126 species The Ferées 157 species
not common common not common
25 (14 7/0) 101. (55 °/o) 56 (31 °/o)

On comparing Iceland with the Ferées we obtain the following
figures: —

Iceland 143 species The Feerées 157 species
not common common not common
37 (19 °/o) 106 (55 °/o) 51 (26 °/o)

The 37 species which grow in Iceland and are absent from
the Ferées are the following: —

fChantransia microscopica. +Petrocelis Hennedyi.

Ceratocolax Hartzii. Cruoria arctica.

Turnerella Pennyi. tPeyssonellia Rosenvingii.

Delesseria Baerii. +Rhododermis parasitica.

Bonnemaisonia asparagoides. Lithothamnion flavescens.

Polysiphonia arctica. L. foecundum.

Ceramium Deslongchampii. rL. tophiforme.

C. fruticulosum. TL. Ungeri.

C. circinnatum. fRalfsia ovata.

C. arborescens. R. deusta.
fRhodochorton minutum. fMyrionema Laminarize
7R. repens. rAscocyclus islandicus.
TDilsea edulis. tEctocarpus penicillatus.

* These and the following figures apply to red and brown algz collectively.
* I attach no importance to the fact of this species having occurred in Ice-
land, as it has not yet been found again.

MARINE ALGAL VEGETATION 73

TSphacelaria radicans. TDictyosiphon Chordaria.
TS. olivacea. D. corymbosus.
Omphalophyllum ulvaceum. Saccorrhiza dermatodea.
fPheostroma pustulosum. Laminaria nigripes.
Coilodesme bulligera. fFucus serratus.

fDictyosiphon Mesogloia.

Which of these species may be found in the Ferdées is not
easy to decide (cf. also Borgesen, 12, p. 795). But it does not
appear altogether improbable that 19 species (marked with a +
before the name) could occur there.

The 51 Feerdese species which are not found in Iceland are
the following: —

fErythrotrichia ceramicola. +Rhododermis elegans.
tPorphyra leucosticta. Phymatolithon levigatum.
7Chantransia efflorescens. Lithophyllum incrustans.
TC. Daviesii. _L. hapalidioides.

Choreocolax Polysiphoniz. rSorapion Kjellmani.
tHarveyella mirabilis. fMyrionema foecundum.
Callophyllis laciniata. 7M. speciosum.

Callocolax neglectus. . rChilionema reptans.
Sterrocolax decipiens. Microsyphar Zostere.
fLomentaria articulata. Ectocarpus velutinus.

Nitophyllum laceratum. TE. lucifugus.

Laurencia pinnatifida. E. dasycarpus.

Polysiphonia violacea. E. granulosus.

TP. Brodizi. Elachista scutulata.
TP. elongata. Sphacelaria czspitula.

P. atrorubescens. S. furcigera.

Rhodomela subfusca. TS. cirrhosa.

Griffithsia setacea. Cladostephus spongiosus.
7Callithamnion polyspermum. Desmotrichum undulatum.
TC. corymbosum. Punctaria latifolia.

C. granulatum. yAsperococcus echinatus.
7Ceramium Boergesenii. yLitosiphon Laminarie.

Rhodochorton seiriolanum. +Phzeostroma parasiticum.
7Furcellaria fastigiata. y7Himanthalia lorea.
fPolyides rotundus. ;Halidrys siliquosa.

7Cruoriella Dubyi.

Possibly many of these species, perhaps almost half of them,
are to be found in S. and SW. Iceland. The 26 species marked with
a + before the name may possibly be found in Iceland, though
with many of them this is doubtful.

If it should appear from further investigations that some of the
species considered not common to the Feerées and Iceland are com-
mon to them, it should not be assumed from this that the floristic

74 H. JONSSON

resemblance is increased, as it is highly probable that other species
which are not common would be simultaneously found.

From the coast of Norway I select Finmark for comparison
with Iceland, which comparison gives the following figures: —

Iceland 143 species Finmark 125 species
not common common not common
45 (26 °/o) 98 (58 °/o) 27 (10)! 70)

A comparison between Finmark and SW. Iceland gives the
following figures: — |

SW. Iceland 115 species Finmark 125 species
not common common not common
7h es AS ch) 86 (56 °/o) 39 (25 °/o)

The following are the 45 species which are found in Iceland
and are absent from Finmark: — |

1 Porphyropsis coccinea. 24 Ralfsia ovata.

2 Chantransia Alarie. ; 25 R. clavata.

3 Phyllophora membranifolia. 26 R. verrucosa.

4 Ceratocolax Hartzii. 27 Myrionema Lamimarie.
5 Lomentaria rosea. 28 M. Corunne.

6 L. clavellosa. 29 M. globosum.

7 Plocamium coccineum. 30 M. feerdense.

8 Delesseria Baerii. 31 Ascocyclus islandicus.

9 Bonnemaisonia asparagoides. 32 Microsyphar Polysiphonie.
10 Pterosiphonia parasitica. 33 Ectocarpus Stilophore.
11 Callithamnion Arbuscula. 34 E. tomentosoides.

12 Ceramium acanthonotum. 35 E. tomentosus.

13 C. fruticulosum. 36 E. Hinksie.

14 C. arborescens. 37 Sphacelaria radicans.

15 C. atlanticum. 38 S. olivacea.

16 Rhodochorton minutum. 39 Omphalophyllum ulvaceum.
17 R. repens. 40 Litosiphon filiformis. —
18 Dilsea edulis. 41 Phzostroma pustulosum.
19 Petrocelis Hennedyi. 42 Phyllitis zosterifolia.

20 Cruoria arctica. 43 Dictyosiphon Mesogloia.
21 C. pellita. 44 Desmarestia ligulata.

22 Rhododermis parasitica. 45 Laminaria feroensis.

23 Petroderma maculiforme.

Of these species ten (Nos. 3, 6, 7, 10, 11, 12, 18, 21, 26 and 35)
are known from Nordland and therefore might possibly be found
also in Finmark. Furthermore, nine of the species (Nos. 2, 5, 9, 25,
33, 34, 35, 40, 44) are known from West Norway, and the majority
of these will also be found, without doubt, in Nordland and Fin- ©

MARINE ALGAL VEGETATION 75

mark. Of the remaining 23 species the greater number will cer-
tainly be found in Finmark. But I| think it less probable that Om-
phalophyllum ulvaceum and Laminaria feréensis are to be met with
there, while one can form no opinion as to whether the endemic
Icelandic species (17 and 31) exist in Finmark, as their distribution
outside Iceland is unknown. On the other hand I think it somewhat
probable that the Icelandic-Feréese species Myrionema fcréense may
occur in Finmark.

The 27 species, which are present in Finmark and absent from
Iceland, are the following: —

Chantransia efflorescens. . Ectocarpus terminalis.
C. Daviesii. — E. nanus.

Harveyella mirabilis. E. ovatus.
Polysiphonia elongata. Myriotrichia filiformis.
Spermothamnion Turneri. Sphacelaria racemosa.
Furcellaria fastigiata. S. cirrhosa.

Polyides rotundus. Pheosaccion Collinsil.
Petrocelis Middendorfii. Asperococcus echinatus.
Phymatolithon investiens. Delamarea attenuata.
Lithothamnion intermedium. Dictyosiphon hispidus.
L. fornicatum. Laminaria Agardhii.
Lithoderma lignicola. Haplospora globosa.
Myrionema foecundum. Halidrys siliquosa.

Chilionema reptans.

The majority of these species may be expected to occur on the
coasts of Iceland, but there is less probability of Laminaria Agardhi
being met with there.

If we turn to E. Iceland and compare this with the White Sea
we obtain the following figures: —

E. Iceland 80 species White Sea 52 species
not common common not common
43 (45 °/o) 37 (39 °/o) 15 (16 °%o)

The floristic similarity is somewhat considerable, and ten of
the species peculiar to the White Sea are known from other parts
of the coast of Iceland. These ten species are Dilsea edulis, Cysto-
clonium purpurascens, Polysiphonia nigrescens, Delesseria alata, Ptilota
plumosa, Lithothamnion Lenormandi, Corallina officinalis, Dictyo-
siphon hippuroides, Fucus serratus, and Pelvetia canaliculata.

Of these species, however, only an extremely small number
can be expected to occur in E. Iceland.

The five species present in the White Sea and entirely absent
from Iceland are: —

76

Chantransia efflorescens.
Furcellaria fastigiata.
Polyides rotundus.

Sphacelaria racemosa.
Laminaria Agardhii.

With the exception of Laminaria Agardhi all these species
certainly may be met with on the coasts of Iceland, but in E. Ice-
land one can scarcely expect to find others than Chantransia efflo-

rescens and Sphacelaria racemosa.

If we compare Iceland and E. Iceland with West Greenland and
East Greenland we get the following figures: —

Iceland 143 species

not common common
62 (36 °/o) 81 (48 %/o)
Iceland 143 species
not common common
79 (48 °/o) 64 (39 °/o)
E. Iceland 80 species
not common common
11 (9 °/o) 69 (58 °/o)
E. Iceland 80 species
not common common
23 (21 °/o) 57 (53 °/o)

West Greenland 108 species

not common
27 (16 °/o)
East Greenland 85 species
not common
21 (13 %/o)

West Greenland 108 species

not common
39 (33 °/o)
East Greenland 85 species |
not common
28 (26 °/o) .

The species present in Iceland and absent from West Greenland

are the following: —

Porphyropsis coccinea.
Chantransia Alariz.
Phyllophora membranifolia.
Ahnfeltia plicata.

Chondrus crispus.
Gigartina mamillosa.
Cystoclonium purpurascens.
Lomentaria rosea.

L. clavellosa.

Plocamium coccineum.
Delesseria alata.

D. sangvinea.

Bonnemaisonia asparagoides.

Polysiphonia fastigiata.

P. nigrescens. .
Pterosiphonia parasitica.
Odonthalia dentata.
Callithamnion scopulorum.
C. Arbuscula.

Plumaria elegans.

Ptilota plumosa.

Ceramium acanthonotum.

C. Deslongchampii.

C. fruticulosum.

C. circinnatum.

C. arborescens.

C. atlanticum.
Rhodochorton minutum.

R. repens.

Dumontia filiformis.

Dilsea edulis.

Petrocelis Hennedyi.

Cruoria_ pellita.

Rhododermis parasitica.
Phymatolithon polymorphum.
Lithothamnion Lenormandi.
L. flavescens.

L. Ungeri.

Lithophyllum Crouani.
Dermatolithon macrocarpum.

MARINE ALGAL VEGETATION a7

Corallina officinalis. Dictyosiphon Ekmani.
Petroderma maculiforme. D. Mesogloia.

Myrionema Laminarie (in E.Greenl.) Desmarestia ligulata.

M. vulgare. Leathesia difformis.

M. Corunne. Laminaria saccharina (in E. Greenl.)
M. feeroense. L. feerdensis.

Ascocyclus islandicus. L. hyperborea.

Ectocarpus tomentosus. Alaria esculenta (in E. Greenl.)
E. fasciculatus. Fucus spiralis.

E. Hinksie. F. serratus.

Sphacelaria olivacea. Pelvetia canaliculata.

Of the 57 species here mentioned three are found in East Green-
land; viz. Myrionema Laminarie, Laminaria saccharina and Alaria
esculenta. It is most probable that none of these 57 species will be
met with in West Greenland, with the exception, perhaps, of some
of the Myrionema-species.

There are 74 species absent from East Greenland which are found
in Iceland. Of these, 54 species have already been mentioned (see
above), and to these must be added 20 species which are absent
from East Greenland but present in West Greenland and Iceland.
These species are the following: —

Bangia fuscopurpurea. Ectocarpus Stilophore.
Porphyra umbilicalis. E. tomentosoides.
Chantransia secundata. E. penicillatus.

C. virgatula. Sphacelaria radicans.
Polysiphonia urceolata. Litosiphon filiformis.
Antithamnion floccosum. Phyllitis zosterifolia.
Ceramium rubrum. Dictyosiphon Chordaria.
Ralfsia ovata. D. corymbosus.

R. verrucosa. D. hippuroides.
Microsyphar Polysiphonie. Castagnea virescens.

It seems most probable that these 20 species are to be met
with in East Greenland.

The 11 species present in E. Iceland and absent from West
Greenland are included in the above-mentioned figure. They are: —

Gigartina mamillosa. Laminaria saccharina (in E. Greenl.)
Delesseria sangvinea. 3 L. feerdensis.

Odonthalia dentata. L. hyperborea.

Dumontia filiformis. Alaria esculenta (in E. Greenl.)
Lithothamnion flavescens. Fucus spiralis.

L. Ungeri.

The 23 species present in E. Iceland and absent from East Green-
land have also been already recorded. With the addition of the 9
of the above-mentioned species they are the following: —

78 H. JONSSON

Bangia fuscopurpurea. Ectocarpus tomentosoides.
Porphyra umbilicalis. E. penicillatus.
Chantransia secundata. Sphacelaria radicans.
Polysiphonia urceolata. Litosiphon filiformis.
Antithamnion floccosum. Phyllitis zosterifolia.
Ralfsia verrucosa. Dictyosiphon Chordaria.
Ectocarpus Stilophore. Castagnea virescens.

These species might possibly also be found in East Greenland,
as they are already known from West Greenland (see above), and
in that case there could be only 9 E. Iceland-species which were
not known from East Greenland.

In West Greenland there are 27 species which are not found
in Iceland. These are: —

@ Harveyella mirabilis. M Sphacelaria racemosa.
Callymenia sangvinea. Pheeosaccion Collinsii.
Delesseria Montagnei. @ Symphyocarpus strangulans.
Polysiphenia elongata. Kjellmania subcontinua.
Ceramium Areschoughii. Coelocladia arctica.

C. septentrionale. @ Delamarea attenuata.

® Rhododermis elegans. Dictyosiphon hispidus.
Lithothamnion intermedium. Myriocladia cailitricha.
Chantransia collopoda. @ Laminaria solidungula.

@ Sorapion Kjellmani. © L. longicruris.
Ectocarpus Pringsheimii. L. cuneifolia.

@ E. ovatus. @ L. groenlandica.

@ E. pycnocarpus. @ Agarum Turneri.

-@ E. maritimus.

Of these species 13 (with @ prefixed) are found in East Greenland.

In East Greenland 21 species are found which are not known
from Iceland. In addition to the 13 above-mentioned species, they
are the following: —

Chantransia efflorescens. Ectocarpus helophorus.
Dilsea integra. Haplospora globosa.
Petrocelis polygyna. Punctaria glacialis.
Cruoriopsis: hyperborea. Myrionema foecundum.

The greater number of the West Greenland and East Greenland
species here mentioned will probably be met with in Iceland, espe-
cially on the north and east coasts. It is less likely, however, that
the following species will be found in Iceland: — Callymenia sanguinea,
Delesseria Montagnei, Dilsea integra, Petrocelis polygyna, Laminaria
solidungula, L. cuneifolia, L. groenlandica and Agarum Turneri.

According to the above comparisons Iceland most nearly resembles
Finmark, and next to that place the Feerées; the resemblance to West

MARINE ALGAL VEGETATION 79

Greenland is rather less, and to East Greenland is least of all, as
the following figures show: —

common not common
keceland —Pinmark::. «...-..:..- 58 °%/o 42 %7/o
feclaud——the -F2eroes .. 6. sass) es 55 °/o A5 %o
Iceland—West Greenland ....... A8 9/9 52 %o
Iceland—East Greenland........ 39 %o 61 °/o

S. Iceland is too little known to be compared with other districts,
as has already been emphasized above. The resemblance to the
Fer6des will certainly prove to be much greater than is shown by
the figures now known.

common not common
S. Iceland—the FeerGes ......... 44 9/9 56 °/o
- §. and SW. Iceland—the Ferées. 55 °/o 45 %/o

S. Iceland and SW. Iceland together resemble the FerGées to the
same degree as do the coasts of Iceland taken as a whole. The fact
that S.Iceland least resembles the FerGes is merely due to a de-
ficient knowledge of its coasts.

As regards SW. Iceland—Finmark the percentage of species
common to both places is 56 and that of not common 44. Thus,
the resemblance is somewhat less than that between Iceland and
Finmark.

If we now turn to E. Iceland we obtain the following figures: —

common not common
E. Iceland—West Greenland...... 58 °/o 42 %/o
E. Iceland—East Greenland...... 53 %7/o A7%/o
PE fecland—-White Sea... .4 <n. 39 %/o 61 °/o

E. Iceland has thus the greatest floristic resemblance to West
Greenland, resembles East Greenland somewhat less and the White
Sea least of all, although the floral districts of E. Iceland and the
White Sea resemble each other most closely when the species are
grouped according to geographical distribution (see above).

V. THE VERTICAL DISTRIBUTION OF THE SPECIES.

[' we walk along the beach at low-tide we see a belt laid bare,
the breadth of which varies according to the degrees of declivity
of the coast and according to the tides — that is according to
whether it is spring-tide or neap-tide. At spring-tide the belt is
broad and at neap-tide narrow. The low-water mark of neap-tide
divides the belt laid bare into two parts, an upper part which is
laid bare during every low-tide and a lower part which is laid bare
only at and about spring-tide. The upper part, between the upper
limit of growth of the algal vegetation and the low-water mark of
neap-tide, which almost coincides with the lower edge of the Fucacee-
belt, I call the Upper Littoral Zone. The lower part, from the
lower edge of the Fucacee-belt to the usual’ low-water mark of
spring-tide, I call the Lower Littoral Zone. Below low-water mark
of spring-tide begins the vegetation which is constantly submerged.
That the vegetation of the lower littoral zone is closely connected
with that in the upper part of the constantly-submerged zone is
natural and will be discussed subsequently.

In the following table a dash (—) denotes a habitat (depth) in
which the species has been found many times, and a dot (-) one
in which it has been found either once or comparatively rarely.

Table 7. The Vertical Distribution of the Species.

Litto-|
ral Depth (metre)

zone

46—50

51-55

36—40
41—45
61—65

56—60

| | | |
Rhodophycee. | | |

| Bangia fuscopurpureal?. (a1. 0.0.7 4 |

sl: Porphyrayimimiataly ce eee [===

1 No notice is taken of the extraordinarily low ebb-tides which occasionally
occur and by which large Laminari@ are often exposed.

H. JONSSON: MARINE ALGAL VEGETATION 81
Table 7. The Vertical Distribution of the Species (continued).

Litto-|
ral |
samy Depth (metre)
sl a] o/2/2|s/4| 2/2) 3/3] 2/3] 2/ 4/2
Mere Sr Ghul We Ile siai Ct i tP Lala Clb et las
BS) 2) “)o) a S\a|&[a) 3] 3/S)5/ 8) 5/8

Eeeerpliiyra umbilicalis.............
Se-OLpiynropsis coccinda............
Sme@omemocelis rosea... 2... ew eee
s] Chantransia microscopica ........
(Ch. 2 IS 03 2 Se
SMO MSCOUMCALA. ws sale ne ce cw ad ee
3°. Cy. WLNE2CI Ee a eae
SEOnoOnGruUsS CrISPUS.......66.....:.
s] Gigartina mamillosa .............
sleauimtielita’ plicata..........0......
s Phyllophora Brodizi v. interrupta.
Sheemmenuoranifolia.... 2.6.62 5 26 ey ee
s Actinococcus subcutaneus.........
seCerarocolax Hartzil....0...........
sl Cystoclonium purpurascens.......
Smlummerciia Pennyl ......:5..666-%
SM mrMOray ChmStata... 6.
s Rhodophyllis dichotoma..........
sl] Rhodymenia palmata............
s Lomentaria clavellosa....... ue
3 Ly: IRD SS2) Hee Skene al eee
SeEIGeamium COCCINCUM™....:.......
s] Halosaccion ramentaceum........
smelesseria aldta. 5.00... c ee vce
Webaernt corymbosa... 0.2. 6665.
SaOeStIuOSa.....:.:.
SMS AUGUIITCA .) 0052 c cel we os eee
Bonnemaisonia asparagoides......
s Polysiphonia urceolata...........
| IP, UES ESE 102 en ee ee
GS [P, SUAS ICES ame
SIBEPPIIPIEESCEDS als. epee coke oe hess
s Pterosiphonia parasitica......... :
s] Rhodomela lycopodioides.........
SmOdeanenalia dentata 0.5.6. 0..0 0%
s] Callithamnion Arbuscula.........
SUCMSCOMMNGORUIN 2.2. 2 eee ee ols ee
Seeluimanria elegans ...-.. 0. 6s. iced es
SAMO UA DIUIMOSA ... ec eles so els
SUPE OLIMACA Ss Ge ae oe Se sie ele os
s Antithamnion Plumula v. boreale.
SIMAPIOCCOSUIM ets cs be es efels wee we
sl] Ceramium Deslongchampii .......

The Botany of Iceland. I.

82 H. JONSSON

Table 7. The Vertical Distribution of the Species (continued).

Litto-
ral Depth (metre)
zone i
51 siio| 2|3| 8/8131 3] 9/3) S) ee idee
Per ent) Tl al at Te) Et) a
BSI" oS A Sa Re eS) S)/ 5/8) s/s
Peelers" ee
s] Ceramium fruticulosum.......... | || / | Loti
SG 2clrCInAcU |.) ols. se ee 4 2 See ea | PS aa |
SUIG@zanbORescens © 50.0.0 aout ac | |
SiC satlantiquimys J. waters weer + -] ¢| eon | |
Si Gaqubnunas. 2g 2ise oss ge ty Sele ae .
sl. acanthonotum- 25.60 400 souk. | |
1 Rhodochorton Rothii............. -l oo. |
SANT repens. 6" atnteces teh eos en | “ leet | |
SRGminutumn. 2 Soe e oe ere - | |
sane penicilliformeys jay gee see eee sll gE Al acne SMe
sR. membranaceumy: oF fs0.56. ps 33 a4 “| - - sili |
sl Dumontia filiformis: 2... .2.02. <. a5 eS | |
sliDilsea ‘edulis. sete soars. kc eee = | | |
s ‘Petrocelis Hennedyi. 22.5229... |= | |
s Crupmagarcticae sth. Aare eee - | elie /
SIG: elite sa.) Wate ahd, ig cul ak ae I Rea |
s Peyssonellia Rosenvingii.......... | -|—|—] +] - |
s Rhododermis parasitica .......... | etl cele :
s Lithothamnion glaciale........... (at | |. >| <1 Sas
Sula. Umsertiy. {eee ei). Sn tees aee | of lo ;
S MLS POP TTORin Gree en ok a ctee es | -|°] *|— t= 2) 2
S SLOHAVeESCeNS. Ferre ater ce aol eno aiece | 1° | cghechl Sela
SE. Teecimad wim Aetna oe ee ! Sa fey?
& AL eB Ves! aes C ipiaee S AA ei ha a <2 °5) aie :
s LL Lenormandis. 3. foo ieee sal |. |
sl Phymatolithon polymorphum..... we ae | |
s Clathromorphum compactum..... | SS -| :
s ‘Lithophyllaum Grouani . 22.2... 2 | |.
s Dermatolithon macrocarpum ..... | IL = SS
siCorallina somieinalis (7 0) we ee =
1 Hildenbrandta moses a7. be ==
Phzophycee. |
s Lithoderma fatiscens............. = SS =
1 Petroderma maculiforme ......... |
s. Ralistaovata."...45 5) ce wera eee
1) Ba yelawallaak. c10 2 ca) 2 cree ian ee eee = | | |
1 Ry Vermueasal. 20. 2 Sen eee ee ee ae
sl Rs demstar css se ntt, 6 ea sero ee — | | 7 |
sl Myrionema vulgare .............. | / ||
s* Mi) (Gorumie* 22h See. ea eee ee | | |
s] M. globosum.: 30s. ae |: —| | | | |
sk M, ferGense x.).ecaou asks Sec eee | |

MARINE ALGAL VEGETATION

Table 7. The Vertical Distribution of the Species (continued).

83

Depth (metre)

6—10
Wl 15

1—5
21—25

26—30

31—35
36 — 40

56—60
61— 65

66—70

sl Myrionema Laminariz...........
Sewscoeyelus islandicus ..../........
sl Microsyphar Polysiphoniz........

s Streblonema ecidioides........... |

Sls. stilophore v. czespitosa.........
tepeamelia: LtOralis) .... jo. 6. ce ees
s Ectocarpus tomentosoides ........
PE TEOMPENLOSUS 4.6 ee ees
SPE MEOMNERVOIMES).. kw ee eee
SIPEISUMCMILOSUS! . Visa eee ee
SPP EPBEMMUCINALUS 5. 6 ee ee ee ee
SIE ICISENCUIAUUIS 9% es ee ede
ROMMIINDEIS ICO eS ee ole ow eee

s] Leptonema fasciculatum v. subcy- ||

UDC TS G3\ ea Deeeors
Peeiaenmista tucicola .........6.-6..
1 Sphacelaria britannica ........
SUS) SEU G2
SMPMOMINGIGEAR ke he ee
Sec m-ectopreris. plumosa ...........-
s Omphalophyllum ulvaceum.......
Seconeraria plantaginea............
sl] Litosiphon filiformis......... bs, A
1 Isthmoplea spherophora.........
slsueuyasiphon tortilis..............
s] Pheostroma pustulosum .........
s] Scytosiphon Lomentaria..........
See bytes zosterifolia ............
S012. TES CIE) se ee
Siu@otodesme: bulligera.............
SEpictyosiphon Ekmani............
SU MesOsIGIAy a. ee nee
31D. OVC Pi ENG | ea
SWMOPCOUVIMNOSUS 2... ae eee oes
SiO SUP PUNOIdES. 1... ose ee eee
SUDstoemiculaceus . 2.2... 66 ee eee se
Se Mesimarestia ViTidis .... 006 sero
RD MAGCTICALAS: 6 6 uy-s ee as eee eee es
=, 1D. G1 a a
siiCastagnea, VIrescenS .....:..5.+++>-
slbbeatuesia difformis ........ +++.
sl Chordaria flagelliformis ......-...
s) Chords tomentosa ......0.....- +.

16—20

SS |

cS

84 H. JONSSON

Table 7. The Vertical Distribution of the Species (continued).

Chrordaicilim: anc ee See ed ct
Saccorrhiza dermatodea ..........

I SeROCMSIS Es Af oe Ws oe Sie ee cows
Li MIBTIPCS ee sks be awed ses ae aoe es
Teclasubeita ss oy ard Macatawa gs ieiee rae
Eeihiy perbOredsns his Ses ere ee
ANAM ARE VA Cots Yale ew hecee aia os ot
Ameseuleniter< Ak dusts the, sco-fersusee oe
PUCUS Spirals 297 s0 cine Bie oe eee
Ear habs Rae ae aus de eee ae ES a oe
PONSCUEALUSES erent erie we es ee ae
EP AVESICUIOSUS Ser. aos Sos ee ee
Pelvetia, canaliculatal.. «220. 256...
Ascophyllum nodosum...........

—— ie P OND nnn nA A

Chlorophycee.

1 Chlorochytrium Cohnii...........
SCI CLUSUNET UNGER Oe sa yan oes

leg GeSelinaitianies foams 2-0 ee 2
“sl Codrolum Petrocelidisy: |... 2.2.5.
PCyeresaniuin . csec etic cle eee
PC sul lie os ee 3 ees pectic oe
I -Percursarial pereursa 2. fu. ccs aes oe
1 Enteromorpha aureola ...........

TNA pe ttemte, os a eG Sa wie x

1
]
DAS Clacton ete, eee e Soe. whats
1 Monostroma groenlandicum ......
slMMGrevillleim ah vik

ly Prasiola*potyrrhizal erence back
PSR tuniuracea..) S42 ie eee ee
1 (PSstipitatats i525 Shoat Ore ees a
1 Ulothrix consociata v. islandica...
l Ussubilaccidas ojo OR eee oe
lU. pseudoflaccassac..c. Seen
] AU, Hee ear ee ae on a heh Ge
1 Pseudendoclonium submarinum...
sl Entoderma Wittrockii: ... 2.22...

Laminaria saccharina .:........::

!

Litto-
ral Depth (metre)
zone
tel sy ol si el elel slo! s!e|elel/sle
DO) Oo] Sim] al | op oo | | atl | us| S] | |
Berti Ti Ti tl tl alt] 1) et ite eee
O}] = wt Of] mt Om] OY] me] Ol | OO] I
3/ = Sha a] NI AN oo) oo] | S| |! wo] wo] SS
{ |

|

| eae ie

i)

MARINE ALGAL VEGETATION 85

Table 7. The Vertical Distribution of the Species (continued).

Litto- ||
| ral Depth (metre)

! |

6—10

11—15
16—20
21—25
26—30
31—35

| 36—40
41—45 |

| 46-50

| 51—55.
56 — 60
61—65.
66—70

88

be
5)
Q
Q
=|

beaekochzete parasitica,............. ! | :
o) 2. PE OS 2 ||?
s] Bolbocoleon piliferum............ -|—
feWiveliafucicola. ..... 22.0002. al
shPrmegsheimia: scutata..0/2........
Memlaclieete. TETOXP. 6. fat oe oe viele»
Mewmespora mirabilis... 0... ......... — :
| iUle [5/21 1/211 ale rh or ae — |
Sue wWormskioldit .:. 2. ).6 0.0.20 0% —||-
1 Chetomorpha tortuosum......... oss ; |
Phe MMelarOMiUM':.......). 0%. s00+0 —|—|—
1] Rhizoclonium riparium.......... Ses
s] Spongomorpha vernalis........... | j—
1 Acrosiphonia albescens........... =
Sh LI CUDA 2 eS ae —| -
SPM NUS EINE: oak ele ci os a wis seie cle wes es —|—|—
PeemANeWIIOFINIS. -. 3... soe yoo
IeAeepeMICMUTOVIMIS ....5........-65%
le@ladophora Trupestris..:.:..... 2.10. oss
Cartas oy, os Le. ecco Part aie ahs

1 (Cr, Sr (CCE a —
l

]

S

S

WAAPANECSRENIS 7. oo io ols et ss
Ay RITES ae aa Oe Beem

Gomontia polyrrhiza .............
Ostreobium, Oueketti.’.. 0-4... .6... |

Cyanophycee.
Pleurocapsa amethystea.......... =
Plectonema norvegicum.......... il
Phormidium autumnale.......... . )
Spinmina, subsalsa ... 2... 2... +-->
Calothrix scopulorum............ —
IM VUNlARIA ALTA SoS. ee. oes

ee ee ee)

Fungi.

Dothidella Laminariz.........%.-.-- — | — | |

A. Upper Littoral Zone.
The preceding table shows that 18 species of Rhodophycee, 18
species of Phwophycee, 36 species of Chlorophycee and 6 species
of Cyanophycee grow in the upper littoral zone; that is, 78 species

86 H. JONSSON

in all. Of these species some are common and others rare; some
are found exclusively in the upper littoral zone and others extend
further downwards. In order to show this more distinctly, each
group will here be dealt with separately and in detail.

Rhodophycee. Of the 18 species mentioned 5 are common,
and the remaining 13 rarer. The following are the commonly dis-
tributed species: Bangia fuscopurpurea, which is found exclusively
in the upper littoral zone; Porphyra umbilicalis which is found also
in the lower littoral zone; Polysiphonia fastigiata which occurs ex-
clusively on Ascophyllum nodosum in the upper littoral zone; Rho-
dochorton Rothit which extends to a depth of 10 metres, and Hilden-
brandia rosea which extends to a depth of 5 metres. The three
first-named species are common in places exposed to the light in
the littoral zone; Rhodochorton and Hildenbrandia, on the other —
hand, occur most frequently as an undergrowth, or in shady clefts
(Rhodochorton), and at the bottom of pools (Hildenbrandia). These
two species are met with more rarely in places exposed to the
light. The 13 species which occur in the upper littoral zone, but
which must be called somewhat rare, are there shade-loving, and
are then found either as an undergrowth or in shady clefts and
depressions. Some are epiphytes, and are then protected against de-
siccation by the host-plant. The greater number of these 13 species
are common in the lower littoral zone, and the 3 Ceramium-species
which are recorded exclusively from the upper littoral zone may
doubtless be expected to occur also in the lower littoral zone.
Conchocelis does not occur in the lower littoral zone but is found
at a depth of 6—35 metres.

Pheophycee. Of brown alge the Fucacee play the most
important réle. The species are few in number, but are of social
growth, and occur in such quantities that they comprise by far the
greater portion of the bulk of the plants in the upper littoral zone.
Of the 18 species mentioned above, 12 are commonly distributed,
and 6 are more rare, in the upper littoral zone. Of the 12 common
species, 9 are found exclusively in the upper littoral zone, viz., 6
species of Fucacew, Sphacelaria britannica, Ectocarpus tomentosus
and Ralfsia clavata; Pylaiella littoralis, Elachista fucicola and Isth-
moplea, on the other hand, range to a depth of about 10 metres.
Of the rarer species, Petroderma is found exclusively in the upper
littoral zone, Ralfsia verrucosa is most frequent in the upper littoral
zone, but is also met with in the lower littoral zone, as an epi-

MARINE ALGAL VEGETATION 87

phyte; the remaining 4 species are common in the lower littoral
zone, and occur in pools in the upper littoral zone, consequently
they cannot, strictly speaking, be reckoned as belonging to the upper
littoral zone.

Chlorophycee. In the table, 36 species of green alge are
mentioned from the upper littoral zone. Of these, 15 are charac-
terized as common and 21 as rarer. 31 species are recorded ex-
clusively from the upper littoral zone; 2 species, Entoderma and
Bolbocoleon are more frequent in the lower littoral zone; one species
Chlorochytrium dermatocolax is as frequent in the lower littoral zone
as in the upper littoral zone, one species Ulothrix flacca, which
must be considered a decidedly littoral species, grows to a depth
of about 10 metres. Ulvella fucicola also grows to a depth of 5
metres, but must nevertheless be considered littoral. In addition
to these 36 species, others may be found in the upper littoral zone,
which have a more downward extension (e. g. Monostroma Grevillei
var. arctica, M. fuscum, Acrosiphonia incurva, and others), but they
generally keep to the pools.

Cyanophycee. All the species hitherto found (6) grow in
the upper littoral zone.

The species which are recorded from the upper littoral zone
may be put into two divisions. The one comprises the species
which are common in the upper littoral zone and are adapted to
growth in places exposed to the light and the wind during the
period of exposure; these species, then, might be termed strictly
littoral. The other division comprises species which are common
in the lower littoral zone or extend even further downwards. The
greater number of these species does not occur in the open littoral
zone, but is found as an undergrowth or in shady clefts, or in
pools. The real home of these species is lower down than in the
upper littoral zone, and for this reason they can scarcely be de-
signated littoral species.

According to the above, there are in all 58 strictly littoral species:
Rhodophycee 5 species, Pheeophycee 14 species, Chlorophycee 33
species and Cyanophycee 6 species.

The upper littoral zone is thus essentially characterized by a
paucity of species of red alge, by many species of green algz and
by a preponderance of Fucacee. The number of the species of
brown alge is of less importance; it is three times as large as that
of the red alge and about half as large as that of the green alge.

88 H. JONSSON

If we reckon, in percentages, the number of species of each
group of the total number of species in the upper littoral zone we
obtain the following figures. The strictly littoral species (58 in all)
are indicated by a, the other species (20 in all) not strictly littoral
are indicated by b, but no attention is paid to those species which
may be found in the upper littoral zone and appear to grow by
preference in pools.

Rhodophyceze Phzeophycece Chlorophyceze Cyanophycez
aE PORES RED STEMS SR 5 (9%o) 14 (24 %/o) 33 (Tle) aa

UW ah ey avy SEE EME ltr 18 (23 °/o) 18 (23 %0) 36: (46-°/o), VOCS ia)

So far as the abundance of species is concerned I lay special
stress on the red alge, green algz and blue-green alge. It would
be confusing, especially as regards the red alge, to reckon the b-
species as strictly littoral, nor can this be done, because they are
not adapted for life in the open littoral zone. As regards the brown
and green algze, on the other hand, it is of no essential importance
whether the b-species are included or not, as they are so few in
number.

If we calculate how great a proportion the strictly littoral
species form of the combined number of each group we obtain the
following figures: —

Rhodophyceze Phzeophycece Chlorophycee Cyanophycez
Species known at pre-
sent from Iceland.. 76 67 a1 6
Strictly littoral species 5 (6.6 °/o) 14 (20.9 °/o) 33 (64.7 °/o) 6 (100 °/o)
a+ b (see above).... 18 (23.7 °/o) 18 (26.8 °/o) 36 (70.6 °/o) 6 (100 °/o)

B. The Lower Littoral Zone and the Belt below down to
a depth of about 10 metres.

1. The Lower Littoral Zone. From this are recorded 93
species in all (Table 7), viz. 39 Rhodophycee, 37 Pheophycee and
17 Chlorophycee. Of these 93 species, the upper and lower littoral
zones have 15 species in common (8 red, 5 brown, 2 green) which
do not extend further downwards; the greater number of these
belong, strictly speaking, to the lower littoral zone, as, in the upper
littoral zone, they usually occur in pools or very shady spots. 19
species (8 red, 11 brown) have been found only in the lower littoral
zone; but the majority of them probably occur also below the limit
of low-tide, and, in any case, some have their area of distribution

MARINE ALGAL VEGETATION 89

close to this limit; 6 species (1 red, 3 brown, 2 green) have their
area of distribution in the upper and lower littoral zones, and to
a depth of 10 metres, these species are mentioned under the Upper
Littoral Zone, and there, 5 of them are reckoned as littoral. 35
species (10 red, 15 brown, 10 green) grow in the lower littoral
zone, and to a depth of about 10 metres. They appear to be about
as common in the lower littoral zone as in the belt between the
limit of low-tide and the depth mentioned. 18 species (12 red, 3
brown, 3 green) grow in the lower littoral zone, and to a depth
of more than 10 metres; these belong to the species which have a
lower downward range, 15 of them have their uppermost limit in
the lower littoral zone, and 3 of them in the upper littoral zone.

The species characteristic of the lower littoral zone are especially
the 19 species which are found there only, and the 35 species
which extend to a depth of about 10 metres, for some of these (e. g.
Rhodymenia and Halosaccion), by occurring in masses, often cha-
racterize large portions of the lower littoral zone.

_ 2. The Belt down to a depth of about 10 metres. In
the table 103 species are recorded from this belt. Of these, two
occur also in the upper littoral zone, and have been previously
mentioned (Rhodochorton Rothii and Hildenbrandia), 6 occur also
in the upper and lower littoral zones and are mentioned above,
35 occur also in the lower littoral zone (see under this heading);
while 9 species are found only at this depth, but of these some
mav be presumed to extend further downwards and some may
possibly occur in the lower littoral zone. 19 species extend down-
wards, with their uppermost limit in the upper and lower littoral
zones, as, for example, Conchocelis rosea which occurs in the upper
littoral zone and is absent from the lower littoral zone, besides the
18 species mentioned under the Lower Littoral Zone. 32 species
with a downward range have their uppermost limit at a depth of
about 10 metres. :

Besides the 9 species which are found only in this belt, it is
especially the 35 species which this belt has in common with the
lower littoral zone which characterize the belt, as some of them —
those mentioned under the Lower Littoral Zone — by occurring
in masses often characterize large portions of the bottom.

By comparison it can easily be seen that the lower littoral
zone is much more closely related to this belt than to the upper
littoral zone, which, amongst other things, is evident from the great

90 H. JONSSON

number of red alge in the lower littoral zone. This can be dis-
tinctly seen from the following figures: —

Upper Littoral Zone Lower Littoral Zone
58 species (a) 93 species.
not common common not common
Dl (39.427 /o) 7 (4.86 °/o) 86 (59.72 °/o)
Upper Littoral Zone - Lower Littoral Zone
78 species (a + 5) 93 species
not common common not common
54 (36.73 °/o) DANI. 33 9/0) 69 (46.94 °/o)
Lower Littoral Zone From the limit of low-tide to a
93 species depth of about 10 m. 103 species.
not common common not common
34 (24.82 °/o) 59 (43.06 °/o) 44 (32.12 °/o)

The figures show that the upper littoral zone is very unlike
the lower littoral zone, especially if only the species which are
characteristic of the latter, or which occur in the open littoral zone
(a), are taken into consideration, which is most correct, as the
shade-loving species in the upper littoral zone must be regarded
as stragglers from associations lower down. As previously mentioned,
the lower littoral zone bears the greatest resemblance to the belt
which exists lower down (to a depth of about 10 metres).

The species which have their lower limit of growth at a depth
of about 10 metres and which are commonly distributed in the
lower littoral zone I designate semi-littoral because they are found
both laid bare during low-tide in the lower littoral: zone and con-
stantly submerged in the belt below; as these species especially
characterize the lower littoral zone and the belt below to a depth of
about 10 metres I designate this area the semi-littoral zone. It must
not be concluded, however, that semi-littoral vegetation covers the
bottom everywhere down to a depth of 10 metres; below the limit
of low-tide the semi-littoral vegetation appears rather to consist of
stragglers from the lower littoral zone into the Laminaria-belt. Thus
the semi-littoral zone is situated between the Fucus-belt and the La-
minaria-belt. The species which specially occur in the semi-littoral
zone I designate on the whole as semi-littoral, also those which are
found in the lower littoral zone and are not found below the limit of
low-tide; they will probably be found also below this limit. Species
which are common in the lower littoral zone and are rare in the

MARINE ALGAL VEGETATION 91

upper littoral zone, but not known below the limit of low-tide I
have also designated semi-littoral as they might be expected to
grow lower down.!

C. The Sublittoral Species.

These species play the principal réle in the sublittoral vegeta-
tion. This may be characterized in a somewhat similar manner as
the vegetation of the upper littoral zone, although conversely as
regards red and green alg, viz. by a large number of red alge
and an extremely small number of green alge and by the occur-
rence of a mass of Laminariacew. In Table 7, these species are
marked with an s before the name. Their number is shown by
the following figures: —

Species
Littoral Semi-littoral Sublittoral
Week) bbw as Sar 5 30 39
ISOs i Lt Sh rr 14 31 22
SE EID eee aa cae ar ae 1 3
iie-STeEM 2). oie) )s 2 6
d 6) 7 58 76 64

From a comparison of the number of species of the sublittoral
zone with that of the littoral and semi-littoral zones it is seen that
it is smallest in the littoral zone, somewhat larger in the sublittoral
zone and considerably larger in the semi-littoral zone. Species of
green algze occur most abundantly in the littoral zone, and their
number is infinitesimal in the sublittoral zone. Red alge are most
numerous in the sublittoral zone and very scarce in the littoral
zone. The brown algz are more evenly distributed in the different
zones, yet they are richest in species in the semi-littoral zone. The
blue-green algz are found exclusively in the littoral zone.

In the semi-littoral zone the large brown alge do not occur in
masses like, for example, the belt of Fucus in the upper littoral

1 As regards the majority of the species (see Table 7) it is easy to decide
whether they are littoral, semi-littoral or sublittoral, but there are some species,
nevertheless, which it is difficult to refer definitely to any one of the three zones
mentioned, and therefore it is sometimes a matter of opinion whether they should
be reckoned in the one or the other. By perusing the table these species are
easily detected.

2 Two species, Delesseria Baerii and Bonnemaisonia asparagoides are not in-
cluded as their habitat is unknown to me (see 31, pp. 140, 141).

92 H. JONSSON

zone and the belt of Laminaria in the sublittoral zone. This is
possibly the reason why the semi-littoral zone is richest in species.

In Table 7, 64 species are recorded as sublittoral. Besides
these, semi-littoral species occur in this zone, especially as epiphytes,
or, more rarely, as undergrowth. 12 species, almost all semi-littoral,
which extend to a greater depth than 10 metres are mentioned in
the table. In addition, about 14 species can be regarded as epi-
phytic, particularly in the upper part of the sublittoral zone. The
sublittoral vegetation is thus composed of 64 sublittoral species and
of about 26 semi-littoral species, or about 90 species in all.

Lower Limits of Growth.

As far as the lower limit of growth is concerned the species
which are found below low-tide must be dealt with collectively.
In the following table, which shows the lower limits of growth, all
the depths at which species have been known to occur have been,
as a rule, taken into consideration, and thus the table does not
indicate the depth of their general distribution or the depth at
which they form associations (see under Vegetation). In the table,
2 red alge are omitted, as I have no further knowledge regarding
their habitats (31, pp. 140, 141). These species are Delesseria Baerti and
Bonnemaisonia asparagoides. As regards the green alge it must also
be stated that I have not taken into consideration the records from
greater depths than 10 metres. I myself am responsible for some
of these records; the alge often were detached, but sometimes it
appeared as if they really had been growing at the depth recorded.
I always, however, have entertained some doubt concerning this,
and consequently prefer at present not to consider records from
such depths. Regarding Chlorochytrium inclusum the record is cor-
rect, as it grew in Turnerella, which was attached to the bottom
at a depth of 30 metres. For Gomontia and Ostreobium I have given
the most common depth, down to about 40 metres, but I have also
obtained these species, growing inside an old shell of Mya, from a
depth of about 60 metres.

It should be further stated that I do not know the depth to
be given for Desmarestia ligulata. This species has been found by
Ove Paulsen between the Vestmannaeyjar and South-Iceland; I
presume that it grew at a depth of about 20 metres.

MARINE ALGAL VEGETATION 93

Lower Limits of Growth in metres (see Table 7).

About 5—10 About 15-20 About 25-30 About 35—45 About 60
mearalige ...... 13 10 10 15 ii
Brown alge.... r9 8 4 4) 3
Green algz..... 16 ae 1 2
Total... 48 18 15 22 10

37

In the above table 113 species are mentioned, of which 48 do
not extend to a greater depth than about 10 metres, 18 extend to
about 20 metres, 15 to about 30 metres, 22 to about 40 metres and
10 to about 60 metres and more. Thus there appears to be a flori-
stic boundary at a depth of about 10 metres; while another boundary
can be faintly distinguished at a depth of from about 30 to 40
metres, as there are 37 species which appear not to extend further
downwards; and here, also, is situated the lower limit of growth
of most of the Laminariacee which play the same role on the sub-
littoral bottom as the Fucacee play in the littoral zone. Exactly
where the lower limit of growth, as regards the marine alge in
Iceland, is situated — whether it lies at a depth of about 60 to 80
metres or deeper — I cannot at present decide, but it is most pro-
bable that the vegetation at greater depths than 60 metres is, in
any case, extremely poor in species.

According to the above statements the lower limits of the algz
are as follows: —

The littoral limit (Upper Littoral Zone) ......... 53 species 26.77 °/o
erat tr Hl. LOW-E... 6 = vaso ¢ oon cs oo c.e ne oe os abe a teem 0
mmepeurel metres... 2). 2). SPS. PSS Me SP DAO Ty
Ampamt 20; mmmetresii. <h. 2k. fea pal ons LS eoe= 9.09 °/o
At about 30—about 40 metres................. 37 — 18.68 °/o
freabout 60. metres and. more... ... 2.08 os. 10 — 5.05 °/o

198 species.

By future investigations all these figures will undoubtedly be
altered and many of them to no inconsiderable extent; but the four
principal boundaries, namely the littoral limit, the 10-metre limit,
the 30—40 metre limit and the absolute depth-limit will always
remain evident.

As regards the absolute depth-limit I cannot make any definite
statement. The dredgings which I myself have undertaken have all
been conducted with a small dredge from a small rowing boat.

94 H. JONSSON: MARINE ALGAL VEGETATION

The positive results which are obtained with this small dredge are
satisfactory enough when the material is inspected with sufficient
criticism, but it should not be concluded with certainty from a
negative result (that is, when absolutely nothing comes up from the
bottom) that no plants grow there. In great depths, also, dredging
is difficult from a small rowing-boat. In some places only, in SW.
Iceland and E. Iceland, have I undertaken dredgings in a depth of
about 80 metres, and the result has been negative. In those places
where the plummet revealed a clayey bottom, it was certain that
no plants were growing there. Off S. and SW. Iceland I have met
with no vegetation at a greater depth than about 40 metres, but in
Reydarfjoréur in E. Iceland, on the other hand, I have come across
plants at as great a depth as about 60 metres. This might indicate
that the vegetation extends further downwards in E. Iceland; but
as the observations are too few, this point must remain undecided
until further investigations are forthcoming.

It was a fairly common occurrence, especially in the fjords of
E. Iceland, to encounter sunken fragments of algz (often strictly
littoral species) and of mosses in depths of more than 22 metres.
In Seydisfjéréur I came across leaves of Betula and Salix at a depth
of 14—20 metres.

C. H. Ostenfeld (the Ingolf Expedition) found Lithothamnion
laeve in great quantities at a depth of 88 metres off the north coast
of Iceland, and R. Hérring (on board the “Diana,” off E. Iceland)
found Lithothamnion tophiforme at a depth of 70 metres. In depths
of from 60 to about 100 metres Hoérring found, in addition, frag-
ments of various algz, amongst which were strictly littoral species,
and of mosses which had evidently fallen to the bottom. In order
to draw the attention of future investigators to this matter it must
further be mentioned that Hérring brought home in spirits a
young plant of Laminaria saccharina from a depth of from 81 to
104 metres (Mjoifjérdur, 14.5.1898, St. XIII) and on the label was
written “In the trawl were many large Laminarie which had been
torn away from the bottom.” The Laminaria brought home appeared
normal, and, if it had fallen to the bottom could only have lain
there for a short time. What is most likely is that the trawl passed
over an uneven bottom, and that the Laminari@w grew at a lesser
depth than that mentioned; or is it possible that the deep-water
form of Laminaria saccharina ranges so far downwards? I leave it
to future investigation to decide this question.

VI. MARINE ALGAL VEGETATION AND SEA-
GRASS VEGETATION. |

6 aa vegetation of the sea is naturally divided into two principal
groups: the Plankton composed of the small plants floating
passively in the water, and the Benthos which comprises the
species attached to a substratum. In this article only the latter is
dealt with.

The Benthos?* falls naturally into two divisions, viz. the litho-
philous vegetation, the communities of marine alge (subformation
of marine alge, Halo-nereid communities, Warming, 72, p. 170),
and the vegetation of loose soil (Enhalid-formation, Warming,
fa. pe177).

The Benthos has been divided in different ways. J.G. Agardh
in 1836 (Novitiz Flore Sveciz) divided the marine vegetation into
three zones, a green zone above, a brown zone in the middle and
a red zone lowest of all. Lyngbye in the same year, also divided
the vegetation into three zones (Rariora Codana, printed 1879—80),
a zone of green alge (Ulvacew) being above, a zone of red alge
in the middle and a zone of Laminariew below this. Orsted (77),
like Agardh, also divided the vegetation in the Oresund into three
zones, but @rsted has the merit of being the first to explain that
the division of the zones depends upon the depth to which the
light penetrates, and upon the colour of the light at the various depths.

Kjellman has divided the algal Benthos into regions. Where
there is a tide, the littoral region is reckoned as being between the
highest high-water mark and the lowest ebb-tide mark; where, on
the other hand, there is no tide Kjellman reckons the littoral
region as extending from the uppermost limit of the algal vegetation
to a depth of 11/2—2 fathoms (34, p.7). The sublittoral region ex-
tends from the lower limit of low-tide, or else from a depth of 1'/2

1 No notice is taken of the bacterial flora of the sea.

96 H. JONSSON

—2 fathoms, down to a depth of 20 fathoms; and finally the
elittoral region stretches from the 20-fathom contour downwards.
This division, unchanged in its main features, is generally employed.
The boundary between the littoral and sublittoral regions is, I think,
commonly supposed to be rather sharply defined in places with
tides, and less sharply defined where tides do not occur.

By this division into three regions the algal Benthos is divided
into three belts of different depth. Although the boundary lines thus
drawn may be described as floristic boundaries, as regards many
species, yet they cannot always be regarded as natural limits of
vegetation. If natural limits of vegetation are to be drawn, several
factors must be taken into consideration. From depth-records, pure
and simple, a somewhat clear idea may naturally be formed of the
conditions of light, but not of the salinity and warmth. If the
conditions of light, salinity and warmth in those layers of water
where the algal vegetation lives were known all the year round it
would be easy to characterize the limits of the vegetation. The
great importance of the salinity to algal vegetation is well-known
and is emphasized by Rosenvinge (63), Svedelius (71), Bérge-
sen (12) and Kylin (45), amongst others.

The ecological factors in the coastal waters round Iceland are
not so well known that I am able to draw the natural limits of
the vegetation by means of them. My starting point is, therefore,
the vegetation itself, and from the appearance of the vegetation it
is possible, to a certain extent, to form an opinion as regards the
ecological factors, in the same way as an opinion may be formed from
these concerning the appearance and composition of the vegetation.

The marine algal vegetation divides itself into several zones as
the Benthos does in fresh water. The divisions between the zones in
the sea are very distinct: some species seem to be spot-bound or
very sensitive to changes of level; other species may occur in two
or several zones; but it depends especially, I think, on the quality
of the water, the intensity of the light and, where there are tides,
on the period of exposure (in the littoral zone).

By studying the vertical distribution of the species and asso-
ciations, I have come to the conclusion that the marine algal vege-
tation may be divided into three zones almost parallel one with an-
other: the Littoral Zone, the Semi-littoral Zone and the Sublittoral Zone.

The Littoral Zone understood in a more restricted sense is
identical with the upper littoral zone and extends almost to the

MARINE ALGAL VEGETATION 97

low-water mark of neap-tide, and is exposed during each low-
tide; the upper littoral zone is, then, the littoral zone proper,
which doubtless corresponds exactly with Kolderup Rosenvinge’s
limitation of the littoral zone in Greenland, but not entirely with
Boérgesen’s limitation of the littoral zone in the Fer6ées, as some
of the Feerdese littoral associations seem to belong to the next belt.

The semi-littoral zone extends from about the low-water
mark of neap-tide to a depth of about 10 metres, and thus extends
over the lower littoral zone, and even lower than that. In reality
this zone comprises the lower littoral zone including stragglers below
the low-water mark of spring-tide to a depth of 10 metres. That
part of the zone lying in the lower littoral zone is laid bare at and
about spring-tide, but is submerged at neap-tide.

The sublittoral zone extends from the low-water mark of spring-
tide to the absolute depth-limit.

There seems to me to be no reason for calling any part of the
Benthos elittoral. Even if the 40-metre contour is a lower limit of
growth in the case of several species, and is, approximately, the
lower boundary of the Laminaria-community, yet the upper bound-
ary of the red-algze communities which extend further downwards
than 40 metres lies much higher, and the 40-metre contour thus
cuts straight through natural communities. It cannot, therefore, be
considered the principal boundary as regards the whole of the
constantly-submerged vegetation. Strémfelt (l.c.) is of the opinion
that, possibly, elittoral vegetation does not exist on the coasts of
Iceland. According to Kjellman the elittoral vegetation is extremely
poor in species, and probably has a limited distribution everywhere
in the northern seas. From what+has been said above respecting
the 40-metre line, and from a comparison with Greenland (Rosen-
vinge, 63) and the Ferées (Bérgesen, 11 and 12), it is obvious
that a division of the constantly-submerged vegetation at this depth-
line is not quite natural in the northern seas. It is more correct,
therefore, to do as Rosenvinge and Boérgesen do, and to class
the vegetation as sublittoral down to the absolute depth-limit.

In the following I do not employ the term “region,” which is
now generally used to describe somewhat limited subdivisions of

The Botany of Iceland. I. 7

98 H. JONSSON

the vegetation, as I have thought it better to designate the algal
Benthos taken as a whole by this word, and to call it the “algal
region.”

I have also avoided the term “formation.” The algal formations
established by Kjellman and others are not real formations, but
only associations (Warming, 72, p. 171), and the entire marine
algal vegetation is given as a subformation of marine algz (Halo-
nereid; Warming, 72, p. 169). I do not think that the term “forma-
tion” should be used in connection with the algal region in any
other sense than that in which it is used in connection with land
vegetation. As the term “facies” cannot be used in English to de-
note a vegetation-unit (Warming, 72, p. 146, foot-note) I have
avoided it.

I divide the vegetation in each of the three zones into asso-
ciations, and where I| think they are closely allied I combine them
into communities.

Sometimes by the suffix “etum” is meant the subordinate part
of an association, and sometimes a vegetation-unit which almost
corresponds with an association.

ACCOUNT OF THE MARINE ALGAL VEGETATION AND THE
SEA-GRASS VEGETATION.

A. The Marine Algal Vegetation.
a. The Littoral Zone.
aa. The Photophilous or strictly Littoral Communities.
1. The Prasiola stipitata-association.
2. The Community of Filiform Algez.
3. The Community of Fucacee.
+ The Pelvetia-Fucus-spiralis-belt.
++ The Fucus-belt.
4. The Enteromorpha-association.
5. The Acrosiphonia-association.
bb. The Shade-vegetation.
6. The Hildenbrandia-association.
7. The Rhodochorton-association.
cc. The Vegetation of Tide-pools.
b. The Semi-littoral Zone.
8. The Monostroma-association.
9. The Chorda-association.

MARINE ALGAL VEGETATION 99

10. The Community of Rhodymenia.
11. The Polysiphonia urceolata-association.
12. The Community of Corallina.
13. The Crustaceous Alga-association.
ce. The Sublittoral Zone.
14. The Community of Laminariacee.
15. The Desmarestia-association.
16. The Deep-water Community of Floridez.
17. The Lithothamnion-association.
18. The Community of Crustaceous Alge.
B. The Sea-grass Vegetation.

1. The Zostera-association.
4

A. The Marine Algal Vegetation.
a. The Littoral Zone.

The Littoral Communities. The littoral vegetation is com-
posed of several communities. These are left dry during low-tide,
with the exception of the pool-vegetation; but the period during
which the different communities are left dry varies greatly. I am
not prepared to state accurately the period of exposure, but I pre-
sume that the lowest littoral communities will be laid bare for
about 1—2 hours under normal conditions, while the uppermost
communities will be submerged for about one hour, and will be
laid bare for about 11 hours. On exposed coasts the period of ex-
posure is shortened by the beat of the waves. The ecological factors
differ not a little in the uppermost and lowermost part of the littoral
zone, and because of this difference the vegetation is divided into
longitudinal belts along the coasts. The littoral vegetation falls na-
turally into three divisions: the light-loving or strictly littoral com-
munities, the shade-loving communities, and the pool-vegetation.
In the following description of the vegetation, the communities in
each of the three zones are arranged as far as possible according to
depth, and in such a way, that the uppermost come first and the
lowest come last. This rule, however, cannot always be adhered to.

aa. The Photophilous or strictly Littoral Communities.

These communities are found in places in the littoral zone
which. are directly exposed to light during low-tide.

They are composed of blue-green, green, brown and red alge; the
7*

100 H. JONSSON

brown algz are found most abundantly, the green alge come next,
red alge occur less frequently, and blue-green alge are found in
the smallest quantity. The substratum is either rock — solid rock
or else talus of debris — or pebbles, or in many places consists
of gravel, clay or mud. The perennial species prefer almost
exclusively the rock-substratum; but they occur, though
very seldom, on other substrata, and are then, as a rule, dispersed
here and there on small stones, viz. on a gravel-clay soil at the
head of the fjords. The annual, short-lived species also occur most
frequently on a rock-substratum, but they also occur fairly frequently
on the pebbles of the littoral zone.

1. The Prasiola stipitata-association.

This association extends furthest upwards and is found well
developed on the rocks in several places round the coasts. It is
usually almost on a level with the Verrucaria-maura belt and, up-
wards, sometimes approaches the outposts of the land-vegetation.
At the highest water-level it is covered by the sea for a short period,
or is, at least, washed by the breaking waves; but such high water
occurs only rarely, and in normal conditions this association must,
without doubt, be content with the spray from the waves during
spring and summer. On less exposed coasts this association is, as
a rule, sharply defined from the community of filiform algze which
exists ‘below, but on a very exposed coast the boundary is more
variable. | :

The dominant species in this association is the small, leaf-like
Prasiola stipitata, which grows very socially upon the tops of flat
rocks. As it has its distribution almost exclusively in this belt it
seems natural to designate the association by its name. It is essen-
tially adapted to live in the air, and is capable of withstanding
desiccation well, which may be perceived, inter alia, by the fact
that it does not seek clefts and crevices but grows on surfaces
which are exposed to light, wind and weather. The density of the
vegetation must also afford each individual some protection against
desiccation. In spring and summer long periods must occur during
which this association is not wetted by the sea, and, during summer
drought, I have often seen Prasiola stipitata as dry as a bone upon
the rocks. Prasiola furfuracea also occurs side by side with this
species, but is rarer.

Species and varieties of species, such as Enteromorpha intesti--

MARINE ALGAL VEGETATION 101

nalis f. micrococca and Rhizoclonium riparium, which essentially be-
long to the lower belts, but can accommodate themselves to life in
the air, are also included as members of this association. They are
species which, owing to their structure or their manner of growth,
are capable of enduring desiccation. Enteromorpha intestinalis f.
micrococca has, as is well known, small cells, the walls of which
are very thick, the inner walls, in particular, being highly thickened,
serving possibly as reservoirs for water. It prefers fissures in the
rocks, where, as a rule, it is less exposed than the species charac-
teristic of the association. Sometimes, however, I have come across
f. micrococca growing, like Prasiola stipitata, on flat rocks manured
by birds, but then it had a different aspect and, at first sight, some-
what resembled Prasiola. Rhizoclonium also occurs in fissures, where,
owing to its manner of growth — that is to say its pulvinate form
— it is protected from desiccation during the long periods of drought.
‘Calothrix scopulorum also occurs as a member of the Prasiola-
association and forms Calothriceta of limited dimensions; the indi-
viduals are procumbent and are placed so closely together that the
rock is completely covered, and thus they protect each other from
desiccation. From a biological point of view, the manner of growth
of this species, in the dry condition, is similar to that of the cru-
staceous alge. Enteromorpha intestinalis f. minima also occurs in
this community.

The species in this community grow, as a rule, in small, pure
societies which form a narrow, though not a continuous belt along
the coast. This belt is situated higher on exposed coasts than it
is on those which are less exposed.

The Prasiola-association is undoubtedly commonly distributed
in neighbouring countries, but the constituting species may be dif-
ferent. In Greenland (Rosenvinge, 63, p. 200) Calothrix scopulorum,
Ectocarpus maritimus, and Rhizoclonium riparium occur .only in the
uppermost part of the littoral zone. This vegetation, however, scarcely
corresponds with the Prasiola-association, but rather with that
‘occurring below. In the Fezrées, however, an exactly corresponding
association is’ found, which Bérgesen calls the Chlorophycee-
formation (12, p. 712). The Feréese Chlorophycee-formation, how-
ever, appears to be more luxuriant and is composed, in part, of
other species. A Prasiola-association (Foslie, 18, p. 127) similar to
that of Iceland is evidently found in Finmark.

102 H. JONSSON

2. The Community of Filiform Alge.

It is not easy to find a suitable name for this community. It
is composed of several species which are all equally common and
are all dominant to almost the same degree. As almost all the
species are filiform and non-branching, it seems to me that the
community may fitly be named in accordance with the form of
the frond. 3

The community of filiform alge forms a narrow belt, which
is often continuous along fairly considerable stretches of the coast,
at about the average limit of high water. The vertical height of
the belt is inconsiderable, about one foot, but the breadth conforms
somewhat to the slope of the coast, and may attain to 3—4 feet,
or even more. This vegetation is very well developed on the face
of vertical rocks, and the various associations of the community
can be distinctly seen, one above the other, as parallel bands of
varying colour. The species which occur most frequently are the
following: —

Ulothrix flacca. Bangia fuscopurpurea.

Urospora mirabilis. Porphyra umbilicalis f. typica.
Monostroma groenlandicum.

These are all dominant species, and form extensive associations,
of which some are pure and others mixed. Other species may also
occur, but only in lesser quantities.

The Ulothrix-association, as a rule, reaches highest up
the cliff. The principal species is Ulothrix flacca, which forms a
distinct belt, extending rather far in a horizontal direction. On
rock-walls, the filaments are often comparatively long, and are
moved to and fro over the entire belt by the beat of the waves
or the ripple of the sea at flood-tide; during the period of exposure
they hang down, pressed closely against the face of the rocks. The
outer filaments protect the underlying ones from desiccation during
low-tide, and thus it happens rather frequently that the outer layer
is dry while the protected layer — that nearest to the rocks — is
moist. In this way the social growth of the plants protects them
against desiccation (cf. Rosenvinge, 63, p. 201), at any rate under
normal conditions, and so long as no exceptionally long periods
of drought occur. It happens rather frequently, however, that the
Ulothrix-vegetation becomes quite dry during low-tide. This is espe-
cially the case when the vegetation occurs on boulders in the lit-
toral zone where, when the water subsides, the filaments radiate

MARINE ALGAL VEGETATION 103

from the highest point of the stone. Such a stone-surface is smooth
and dries more quickly and completely than the uneven face of
the rock. This vegetation appears to maintain itself well in spite
of being completely dried up, day after day, during low-tide, —
during the nocturnal low-tides, naturally, it is dried up to a much
lesser extent. As a rule, such a dried-up Ulothrix-vegetation is so
tightly adpressed to the surface of the stone that it can only be
removed by being scraped away with a knife. Thus, owing to de-
siccation, it appears, from a biological point of view, to have as-
sumed a crustaceous form, which evidently diminishes the evapora-
tion from its surface.

The other species which occur in great quantities in this as-
sociation, such as Urospora mirabilis and Monostroma groenlandi-
cum, act biologically in a similar manner to Ulothrix flacca. Both
these species are found fairly frequently growing among Ulothrix
flacca; and as I think that these species may in several respects
be comprehended in one biological unity, I consider them members
of the same association, although they both occur in pure growths
(Urosporetum, Monostrometum).

While Ulothrix flacca and Urospora mirabilis are commonly
distributed, the distribution of Monostroma groenlandicum is more
restricted, for this species can be reckoned as commonly distributed
only in E. Iceland.

Of the species which are rare or of local occurrence, and which
are reckoned in this association, the following may be mentioned:
Ulothrix pseudoflacca, Ulothrix consociata var. islandica and Urospora
Hartzii. In addition, Enteromorpha intestinalis f. micrococca and
Rhizoclonium occur here as they do in the Prasiola-community.

Of these species Ulothrix consociata var. islandica requires to
be described most fully. It is very social, and grows in cushion-
like masses higher up, as a rule, than the other species of the as-
sociation. It appears to be protected from desiccation both by its
manner of growth and by the thickness of its cell-walls.

Codiolum gregarium | have found to be of very social growth,
covering comparatively large stones as pure Codioleta. It is most
nearly related to this association.

The structure of the frond in this association displays various
peculiarities, which must be considered as being beneficial to the
plant during the period of desiccation; for instance, the interior
of the frond of Monostroma groenlandicum is filled with a gelatinous

104 3 H. JONSSON

mass. Rosenvinge (63, p. 201) has pointed out that-this mass
must be of importance as a reservoir for water during low-tide.
Ulothrix flacca also has very thick cell-walls, especially in- the fruit-
bearing filaments (cf. Rosenvingel.c.). The remaining species also
are rather thick-walled.

Although the Ulothrix-association is distributed to an extra-
ordinary extent, yet it cannot be expected to be found everywhere.
It prefers that part of the littoral zone which is rocky and stony,
and grows luxuriantly on a somewhat exposed coast, and even,
indeed, on one which is very exposed. It also extends right’ into
the fjords, if the nature of the shore is favourable to it.

The succession of the associations of filiform algee is seen most
distinctly on vertical rocks on somewhat exposed coasts, where the
Ulothrix-association appears uppermost; but where the substratum
is uneven — a talus of debris or irregularly heaped-up fragments
of rock — the zonal division of the community becomes less ap-
parent, and it may then well happen that the Bangia-association
extends above the Ulothrix-association. |

The Bangia-association prefers the rocky part of the litto-
ral zone, and vertical rock-walls in particular, and is only rarely
found in the stony part of that zone; it occurs normally below the
Ulothrix-association, but where the latter is absent ‘the Bangia-
association is not infrequently the algal vegetation which reachest
highest. In many places it has an extremely wide horizontal dis-
tribution, and is often perceived at a considerable distance as a
reddish-brown band in, and at the edge of, the water. This Bangia-
belt may attain a considerable breadth, as much as three feet, and
it often displays several shades of colour. Thus, in a less exposed
spot facing the south, I have seen the uppermost part coloured
green, the middle part brownish and the lowest part a fresh reddish-
brown. This is certainly connected in some way. with the long
period of drought which, when the weather is calm or the wind
blowing off the land, may well continue from neap-tide till about
spring-tide. During the period of drought Bangia behaves somewhat
similarly to Ulothrix flacca. The filaments are rather long, as long
as 10 cm., and are very closely packed together; on vertical rocks
they hang straight down during low-tide, and are, on the whole,
protected by their structure and manner of growth from too
severe desiccation, in the same way as has been mentioned in
connection with the Ulothrix-association. The Bangia-belt is, as a °

MARINE ALGAL VEGETATION 105

rule, distinctly separated from the Porphyra-association which exists
below, but sometimes the two belts are concurrent, even over rather
large areas.

The Porphyra-association is formed by Porphyra umbili-
calis f. typica. It might be justifiable to incorporate this association
in the Bangia-association, but I prefer to reckon it as a distinct
association; partly on account of the difference in the form of its
thallus, and partly because Bangia is confined to its narrow belt,
while Porphyra occurs also in other associations in and below the
Fucus-belt.

The Porphyra-association occurs on a rocky substratum. On
vertical rock-faces it is very luxuriant, and then forms a continuous
belt below the Bangia-association. Where the littoral zone has large
fraginents of rock, that is to say consists of a talus of debris, this
species grows higher than any others upon the fragments at the
water’s edge. In such places no continuous belt is formed, but the
species occurs in small scattered patches on the upper part of the
blocks of stone. This patchy distribution of the vegetation may
extend horizontally over either a small or a wide area, according
to the form of the coast. The vertical height of the belt is always
inconsiderable.

During the period of drought Porphyra hangs down on the
vertical rock-faces, the thallus being repeatedly folded, according
to its length; the individuals in the upper rows of the association
often, to some extent, covering those below and thus, in some ways,
recalling the behaviour of the above-mentioned filiform alge; on
the blocks of stone, also, the thallus is folded up in accordance
with its length, and rests on the surface of the stone. The folding
apparently serves to reduce evaporation during low-tide, as the
‘evaporating surface is thereby diminished; the folding may well be
of importance also in counteracting the effect of the light. As the
folds of the thallus are produced while the water is subsiding, it
is probable that some of this is retained between them, especially
on a flat substratum; on a sloping or vertical substratum, however,
the quantity of included water would be very small. This circum-
stance is probably of some importance, and has also been empha-
sized by Bérgesen (12).

The Porphyra-association seems to maintain its freshness for
a considerable time, and I saw it with its usual dark purple colour
in several places in E. Iceland in the summer; but round about

106 H. JONSSON

Reykjavik, especially later in the summer, it frequently has a yel-
lowish-brown tinge.

These associations, owing to local conditions, naturally are not
found everywhere along the coasts. At times they are all present,
and then generally in the succession here recorded; at other times
only one or another is present. Thus, in some places, the upper
limit of the marine algal vegetation is indicated by the Ulothriax-
association, and in others by the Bangia or the Porphyra associa-
tion; in places the entire community is absent, and then the boun-
dary is marked by Pelvetia, Fucus spiralis or other Fucacee.

A comparison with the adjacent coasts shows that this community
is found both in Greenland and in the Ferées though it does not
behave in quite the same manner in both places. In Greenland a Mono-
stroma groenlandicum-association is found which is composed of
Monostroma groenlandicum, Ulothrix flacca and Urospora mirabilis,
all intermixed with Bangia fuscopurpurea. This association occurs
in the middle part of the littoral zone. A Porphyra umbilicalis-
association occurs also in the upper part of the littoral zone. Thus,
the same species occur in Greenland as in Iceland, although pos-
sibly they are not present in the same numerical proportion. But
one great difference exists, namely that the Greenland community
is found in the middle of the littoral zone, while the Iceland com-
munity is found much higher up. There is a similar difference in
the occurrence of the Porphyra; as it is found in fissures of the
rocks in the upper littoral zone in Greenland, while in Iceland it
grows upon the surface of the rocks. This difference is probably
due to a difference in the climate.

It is possible that the same community (Bérgesen, 12, pp.
716, 719) may be found at an even greater height in the Ferdes
than in Iceland. In the Feerdes the species are only partially
similar, because Monostroma groenlandicum is wholly absent, and
Ulothrix flacca does not seem to play such an important part there
as it does in Iceland. The community of filiform algz is, in all
probability, common along the coast of Norway (Foslie, 18; Bér-
gesen, 12, pp. 719—720; Boye, 10, p. 20).

3. The Community of Fucacee.

This community is the dominant one in the httoral zone and
comprises six associations, of which the first two, the Pelvetia-
association and the Fucus spiralis-association, are more closely

MARINE ALGAL VEGETATION 107

connected with each other than they are with the remaining asso-
ciations, which also are mutually very closely connected. In this
way the community may be divided into two belts, of which the
first comprises the two first-mentioned associations, and the second
the remaining four. The Pelvetia-Fucus-spiralis-belt is narrow. It
is situated in the upper part of the littoral zone, at, and just below,
lowest high-water mark, i. e. flood-mark at neap-tide. It has only
one layer of vegetation, as there is no undergrowth worth men-
tioning, and it is entirely devoid of epiphytes; it is submerged in
normal conditions for a very short time.

The second, the Fucus-belt is broad; it occurs in the lower part
of the upper littoral zone, just above low-water mark of neap-tide.
The vegetation occurs in two, and sometimes in three, layers and
epiphytes are present in abundance. The vegetation is submerged
much longer than in the first belt. Thus, these two belts differ so
greatly that they cannot be treated together.

The Pelvetia-Fucus-spiralis-belt.

This belt is of common occurrence, and its vegetation is luxuriant
in S. and SW. Iceland, but in the other parts of the country is
sparse and devoid of Pelvetia. This belt is not continuous except
along short distances, and its vertical height is inconsiderable; but
the breadth may sometimes be fairly considerable, especially on
very gently sloping coasts. It grows on rocky coasts, and in places
where these consist of a talus of debris the vegetation is distributed
in patches which is a natural consequence of the surface, the limit
of the association being rather sharply defined downwards. Pelvetia
and Fucus spiralis do not grow intermixed, but occur in two pure
and distinct associations. They grow luxuriantly on exposed coasts;
in the most exposed parts of the coast, however, they seem to
recede. Thus, this belt was either absent from, or was poorly re-
presented on the most exposed points at the extremity of Sneefellsnes
and of the Vestmannaeyjar and at the extreme end of Reydarfjérdéur;
but there occurred in its place surf-forms of Fucus inflatus (f. ex-
posita and f. dendroides).

The Pelvetia-association (Fig. 3) always occurs highest of all.
As already mentioned it is found in S. and SW. Iceland only, but
there it occurs in great abundance in many places; in some places its
vegetation is poor, and sometimes only a few scattered individuals
are found. This is more particularly the case in places where Pelvetia

108 H. JONSSON

appears to have extended too high upwards, and where, when the
weather is calm, it is not wetted daily by the sea at and about
neap-tide. On a warm summer’s day Pelvetia can become so dry
in such places that, when gathered, it needs no further drying —
the same may also be the case with Fucus spiralis. The individuals
of Pelvetia which grow at that height, i. e. sometimes right up in
the Verrucaria maura-belt, are usually very small (about 2 cm. in
height) and occur closely pressed to the rock; then they are often

Fig. 3. Pelvetia canaliculata above, Fucus spiralis below. Illustration of a typical Pelvetia-
Fucus-spiralis-community. Reykjavik, Aug. 13, 1909. (From phot. by Hesselbo.)

found especially in crevices, and the new fronds may bear a sur-
prisingly close resemblance to a rosette. Lower down, where the
vegetation is luxuriant, the plants are about 8 cm. in height. Pelvetia
is the smallest of the Fucacew on these coasts; it differs from the
others not only by its small size, but also by its lighter, yellowish-
brown colour, and its channelled frond, etc. The channelled frond
must be useful to a plant which is so exposed to the desiccating
action of the air as is the case with Pelvetia, because, by reason of
their being rolled, the under-side of the fronds is less exposed to
wind and weather. |

It is characteristic of the zonal division of the Fucaceew on the

MARINE ALGAL VEGETATION 109

coast that the smallest species (Pelvetia, Fucus spir alis) are arranged
in a separate uppermost belt, while the larger species are arranged
in belis lower down, and the largest species (f. inflatus, if the large
broad-fronded forms are included) occurs lowest of all.

The Fucus spiralis-association (Fig. 4) is more Juxuriantly
developed than the Pelvetia-association and occurs just below it. On
flat or very gently sloping rocks this association forms a compara-
tively broad belt, but on a steep coast only a narrow one. Its relation

; Fig. 4. Fucus spiralis. Part of a luxuriant Fucus spiralis-vegetation below the Pelvetia-
association. Reykjavik, Aug. 13, 1909. (From phot. by Hesselbo.)

to exposed coasts has already been discussed. It may happen with
Fucus spiralis, as with Pelvetia, that it extends to so great a height
that at times it is not wetted daily by the sea. In such a case the
individuals are as a rule smaller, and are often rather strongly
spirally twisted; they may be found lying quite dried up on the
rocks, apparently without being damaged thereby. The twisting of
the fronds may possibly result from the drying process.

This belt is, as a rule, somewhat sharply defined from the
Fucus vesiculosus-belt situated below. Although it does not always
happen that there is any distance worth mentioning between F.
spiralis and the upper outposts of the Fucus vesiculosus-association,
yet the boundary is almost always sufficiently distinct.

110 H. JONSSON

This belt behaves similarly in the Ferées (B6rgesen, 12, p.
744). Both Boye (10) and Hansteen (25) mention a Pelvetia-forma-
tion from western Norway without mentioning Fucus spiralis. In
Finmark Fucus spiralis has the same manner of growth as in Ice-
land (Foslie, 18, p. 66).

The Fucus-belt.

The four associations which belong to this belt are the most
extensive in the littoral zone and three of them are found everywhere
on rocky coasts. The breadth of the belt naturally is dependent on the
degree of the declivity of the coast in addition to the nature of the
substratum. This belt occurs everywhere along the coast, but it is not
luxuriant to the same degree everywhere. Its vegetation is so dense
that the bottom is entirely covered, or almost so, by the Fucus
plants which during low-tide partly lie prostrate upon the rocks
and partly hang on them; seen from a distance it appears as a
brown-coloured belt of varying width along the coast. These asso-
ciations are usually found on a rocky substratum, but they may
also occur on a fairly firm gravelly bottom; the latter is especially
the case at the head of the fjords. In such places their vegetation
is poor and the species grow scattered, attached especially to small
stones which are somewhat firmly embedded in the gravelly bottom.
Fucus plants are also found scattered on wood-work, for instance,
on wooden piles. On the whole the species of Fucus require a
stable substratum. The dominant species are the following: —

Fucus vesiculosus. Fucus inflatus.
Ascophyllum nodosum. Fucus serratus.

The first three species are common and grow very luxuriantly
along the coast; Fucus serratus, on the other hand, was found only
in a few places in S. and SW. Iceland; in Hafnarfjéréur it grew
very socially, while in the Vestmannaeyjar it had a more scattered
growth.

The individuals of these species form pure associations which
usually occur in regular succession: Fucus vesiculosus growing upper-
most, Ascophyllum in the middle and Fucus inflatus (and Fucus
serratus) lowest of all. This succession is distinctly observable in
places where the bottom is flat and gently sloping. But where the
bottom is uneven — a talus of debris — the divisions between the
belts are less regular, but can, as a rule, be discerned. It does not,
however, follow that the associations always occur quite regularly;

MARINE ALGAL VEGETATION 111

the species being rather frequently found intermingled; the Asco-
phyllum-association, in particular, does not appear to be as spot-

ysiphonia fastigiata as epiphyte, hanging down on the rocks. Reykjavik, Aug. 13. 1909.

Ascophyllum nodosum. with Pol

bound as the others. It generally occurs somewhat below the middle
of the area occupied by the community, but may occur also higher
up, even at the very top. It is, however, a fairly constant fact that

.

(From phot. by Hesselbo.)

oe isl H. JONSSON

Fucus vesiculosus grows highest and F. inflatus lowest. How the
species behave when left dry is mentioned in connection with each
association. 3

The Fucus vesiculosus-association, as already mentioned,
is uppermost and often borders closely on that of Fucus spiralis.
It varies extremely in extent, according to the character of the coast.
The breadth may vary from about one foot on vertical rocks to
several fathoms on a gently sloping coast.

Fucus vesiculosus extends right into the innermost part of the
fjords, which is generally considered a protected coast; if there is
a favourable substratum there, its growth may be fairly luxuriant.
It also grows very luxuriantly on slightly exposed coasts, i. e. where
a landward wind is sometimes both frequent and tempestuous, but
where breakers are extremely rare. If the exposure is increased, it
seems that F. vesiculosus not only decreases in number of individuals
but also seeks for shelter between the rocks. Then, gradually, it re-
treats lower into the littoral zone, and Ascophyllum, which is evidently
better able to withstand the heavy seas, advances. This is seen
very distinctly at Reykjavik, where the coast must be considered
somewhat exposed, because the south-west, west, and north winds
are frequently stormy and occasion heavy seas. If we take a bay
which is bounded by a rocky promontory, we see at the head of
it a luxuriant Fucus vesiculosus-association; this extends out upon
the promontory, growing gradually narrower as it extends outwards;
in the vicinity of the point itself, the alga has commenced to seek
for shelter, and at the extreme end of the point it has disappeared
and Ascophyllum has occupied its place, and then Fucus vesiculosus
is either found not at all or only a few individuals of it occur
high up in the Ascophyllum-belt. What is here seen on a small
scale is repeated on a larger scale on proceeding from the head of
the fjord outwards to the extreme point of the peninsulas. Thus,
Fucus vesiculosus was not observed on exposed points at Ondverd-
arnes (the extreme point of Snefellsnes), while Ascophyllum and,
naturally, Fucus inflatus also, were found in abundance. On the
most exposed points of the Vestmannaeyjar Fucus vesiculosus was
also absent, while both of the others occurred plentifully.1. Thus,
Fucus vesiculosus behaves in Iceland precisely as it does in the
Ferédes (BOrgesen, 12, 11).

1 Strémfelt (70) records Ascophyllum as growing above Fucus vesiculosus
at Hdélmanes in E. Iceland.

MARINE ALGAL VEGETATION 113

Generally this species forms a pure association, but yet, some-
times, it and Ascophyllum can grow intermixed.? It is always sub-
merged at high-water, but seems well able to withstand desiccation
at low-water, when however the upper side of the frond dries up
considerably, especially on rocks which face the sun, and may then
— and this is true of Fucus inflatus also — be bent upwards, or
even slightly distorted, at the apex, though never to the same extent as
is the case with Fucus spiralis. When such a branch is lifted up,
it can be seen that the under side is moist, even on a warm sum-
mers day. During low-tide the Fucus plants lie prostrate on the rock,
one plant overlying the other, or one branch of the frond covering
the other, and in this way some water is retained amongst the plants.

Naturally, this applies also to the members of the other asso-
ciations in the Fucus-belt. Those individuals which hang freely from
the rocks are exposed more than others to desiccation.

The Ascophyllum-association differs from the other asso-
ciations in its light-brown colour, and, in addition, by the occur-
rence of Polysiphonia fastigiata, which grows very luxuriantly on
it in S. and SW. Iceland; it is often somewhat singular to see the
light-yellow Ascophyllum-belt with the numerous dark reddish-brown
patches of Polysiphonia. |

So far as the behaviour of the species during exposure to, the
beat of the waves is concerned I must refer to the above-mentioned
remarks, and can only add that at times it may also occur in the
most exposed places, but no longer in the uppermost belt. Here
it gives place to the surf-forms of Fucus inflatus (f. exposita, f. den-
droides), which form a narrow belt at the upper boundary of the
Fucus-belt. Ascophyllum occurs, then, between this and the real Fucus
inflatus-belt, which retains its usual position. In a few places, how-
ever, on the most exposed points, Fucus inflatus only is found.

The Fucus inflatus-association. When exposed, this spe-
cies behaves conversely to Fucus vesiculosus and grows most luxu-
riantly on exposed coasts. Thus, it behaves in Iceland as it does
in Greenland (Rosenvinge, 63) and in the Ferées (Bérgesen,
12). In Iceland, as in other places, the species varies extremely
and must be considered very capable of adapting itself to varying
circumstances, especially as regards exposure. The association can
— in accordance with the exposure — be divided into three belts: —
- The Surf-belt, the Wave-belt, and the Calm-belt.

1 The epiphyte-vegetation is mentioned subsequently.
The Botany of Iceland. I. 8

114 H. JONSSON

The Surf-belt, as previously stated, occurs at the upper
boundary of the Fucus-association on rocky coasts which are very
much exposed. I have seen such a belt at O@ndverdarnes in SW.
Iceland, in the Vestmannaeyjar in S. Iceland and at Vattarnes in
E. Iceland. Strémfelt (70) has noticed a similar belt on Seley in
E. Iceland. It will probably be found, on further investigation, that
the surf-belt is far more widely distributed along the coasts than
is recorded above. As a rule, the individuals in this belt are of low
growth; the frond is leathery, and very thick in proportion below,
and rounded, but tapering evenly upwards and becoming thinner;
above, it is often excessively branched. The height of the individuals
varies to some extent, f. dendroides is the highest, while f. exposita
attains only an insignificant height (5—9 cm.). A similar surf-belt
occurs in the Ferdes (Bérgesen, 12), although the vegetation is
possibly more luxuriant there than in Iceland.

The W ave- belt (Fig. 6) comprises the ordinary Fucus inflatus-belt.
As a rule, it is exposed to the movement of the waves, a movement
which is often very violent indeed; more rarely it is exposed di-
rectly to the breakers. Here the species occurs in its typical form
which shows a considerable variation in the breadth and consistency
of the thallus. In very exposed places the branches of the frond are
comparatively long and narrow and leathery, but where the move-
ment of the waves is less felt, the frond is usually broader. The
vegetation of this belt is generally very luxuriant, and covers the sub-
stratum entirely. Often, however, the vegetation occurs in patches,
owing to the surface-features of the shore. Such a mode of occur-
rence is met with, for instance, where the shore is a wild talus of
debris consisting of large scattered blocks of stone, or where the
solid rock has a similarly uneven surface owing to erosion by the
sea. There a belt is formed around each block of stone, while the
hollows between them are occupied by semi-littoral or sublittoral
vegetation, or by stragglers from these zones.

The Calm Belt is lowest of all, often at the boundary between
the constantly submerged and the lower littoral vegetation, and some-
times forms small offshoots of vegetation’ below that boundary.

Here the movement of the waves is least felt, and the frond of the

1 The species varies from the principal form to two kinds of dwarf-forms —
a small “surf-form” of tough texture, and a small “pool-form” of delicate texture.
The pool-form-association (F. inflatus' f. linearis) may be regarded as the fourth
belt, which should then be termed the Delicate Belt (see under The Vegetation
of Tide-Pools, p. 125). —

MARINE ALGAL VEGETATION 115

plants is also usually broader. In this belt the broad forms are to
be found; they may occur both with and without air-bladders. This
belt is as a rule poorly developed, and is often non-continuous.
Within Hvammsfjéréur, in bays protected from the surf, but where
current-movements are felt to a certain extent, I have observed,
below low-water mark, semi-littoral stragglers from the Fucus-
community (i. e. from the Fucus inflatus-association). In a similar
locality I saw Ascophyllum occurring semi-littorally.

Fig. 6. Fucus inflatus (sterile plants) lying prostrate upon the rocks. Above, hanging
Ascophyllum. Reykjavik, Aug. 13, 1909. (From phot. by Hesselbo.)

The Fucus serratus-association was especially luxuriant
in Hafnarfj6rdur on both sides of the fjord, some distance from
the head of it, and occurred lowest of all in the Fucacee-community.
In the Vestmannaeyjar the species grew scattered here and there,
but was not found in the most exposed places. Sometimes on ex-
posed coasts it was found growing in pools in the middle of the
littoral zone.

The Epiphytes and Intermixed Species of the Fucus-
belt. As is well known, an abundance of epiphytic vegetation
exists in the Fucus-belt, at any rate at times. Many of the species
grow socially and often occur in such quantities, that they set their
stamp upon the vegetation. These species may be divided into those

8*

116 H. JONSSON

which grow exclusively, or by preference, on the Fucacee, and those
which occur as frequently on other substrata and must consequently
be considered chance visitors.

Only one single species, Polysiphonia fastigiata, is exclusively
confined to the Fucus-belt (Fig. 7). It is well known that this species
grows only on Ascophyllum nodosum, into the frond of which it puts
its rhizoids,' although its distribution does not coincide entirely with
that of the latter. While Ascophyllum is common everywhere along
the coast of Iceland, Polysiphonia fastigiata is common only in S.
and SW. Iceland; it has been found, also, in a single place in NW.
Iceland. Thus it keeps to the warmer parts of the sea off the coasts
of Iceland, but even within this area it may be absent from coasts
where the sea-water mixes abundantly with the fresh water. It did
not occur for instance at Borgarnes, nor on the nearest islands,
although Ascophyllum occurred in great quantities together with
Fucus vesiculosus and Fucus inflatus. There the sea-water is freely
mixed with water from the large glacier-torrent of Hvita in Borgar-
fj6rdur. Polysiphonia fastigiata does not seem able to endure such
water, but further out, along the fjord, where the water becomes
more saline, it grows in the ordinary manner.

Of those species which grow by preference on Fucacee, Ela-
chista fucicola and Ulvella fucicola may be mentioned. The first of
these is the most important and often occurs in wonderful abun-
dance, Ulvella forms a much less important part of the vegetation,
more especially on account of its minute size. —

Besides these two, other species frequently occur which just as
often, or even more often, grow on other substrata. Of these Py-
laiella littoralis plays a very important part in the vegetation, espe-
cially in the spring; then it sometimes occurs in such quantities |
that it almost covers large stretches of the coast. Ulothrix flacca
also frequently occurs in great abundance, as may also be the case
with Isthmoplea spherophora. In spring and early summer Ecto-
carpus tomentosus and Ectocarpus fasciculatus are found growing to-
gether socially on Fucus inflatus (both of them in S. and SW. Ice-
land). Ectocarpus confervoides is also a rather frequent epiphyte. In
addition, Monostroma and Enteromorpha intestinalis may be mentioned,
on which, again, epiphytes can grow (as for instance Chantransia-
species); also Ulothrix pseudoflacca, Acrosiphonia, Ceramium rubrum,
Ralfsia verrucosa, Conchocelis rosea, Porphyra umbilicalis and others.

1 Gertrud Tobler-Wolff, in Beihefte z. Botan. Centralbl., Bd. 24, 2. Abt., 1909.

MARINE ALGAL VEGETATION rb

It is usually the case that it is the older parts of the fronds
which are most covered by epiphytes; this agrees well with the
fact that the older fronds have a rougher surface than have the
younger ones, and therefore retain the spores better. The epiphytes

Fig. 7. Polysiphonia fastigiata on Ascophylum which is hanging on the face of the rock.
Reykjavik, Aug. 13, 1909. (From phot. by Hesselbo.)

on the Fucaceew do not appear to arrange themselves in strata as
do the Laminaria-epiphytes.

The intermingled species do not play any special réle in
the Fucus-belt, as regards the vegetation; they consist partly of
species which grow on the Fucacee and partly of species which
ordinarily grow outside the Fucus-belt. Of these species the fol-
lowing may be mentioned: —

118 H. JONSSON

Monostroma Grevillei. Cladophora rupestris.
Ulothrix flacca. Acrosiphonia.

Monostroma groenlandicum. Enteromorpha intestinalis.
Pylaiella littoralis. Porphyra umbilicalis.
Chordaria flagelliformis. Cheetomorpha tortuosa.

The Under-vegetation. This is found commonly distributed,
and varies considerably, both as regards luxuriance and the species
composing it. The luxuriance seems to increase with the degree of
exposure (except perhaps in the most exposed places), and then the
composition of the species is also changed, as species which pri-
marily belong to a lower belt extend higher up, probably on ac-
count of the frequent movements of the sea which cause the de-
siccation-period to last but a short time. The undergrowth must
be regarded as a kind of shade-vegetation; during low-tide it is
completely covered by the Fucacee, and at high-water the intensity
of the light is also subdued by them, as they float on, or rise with,
the water, and are moved backwards and forwards by its ripples.
The greater part of the species of the undergrowth do not occur
at the height of the Fucus-belt in places open to the light, but
occur frequently and abundantly in shaded localities, although these
may be found at the upper boundary of the Fucus-belt as, for in-
stance, in depressions in the talus of debris, upon the under side
of overhanging blocks of stone. This vegetation may therefore be
justly termed the shade-vegetation of the littoral zone. The species
are normally developed and cannot be compared with the shade-
forms of light-plants belonging to the land-vegetation. On the other
hand, the shade-vegetation of the littoral zone actually corresponds
with the shade-vegetation of the land, such as the fern-vegetation
and the liverwort-vegetation in the lava-fissures.

The under-vegetation belongs in part to the shade-vegetation
(see p. 123) and is divided into several associations; here it is dealt
with under the Fucus-belt as its strictly littoral distribution almost
coincides with that of the latter, and it is just as dependent on
the upper-vegetation, or even more so, as is the undergrowth in a
coppice. As regards the relation between the upper-vegetation and
the undergrowth in the Fucus-belt the main advantage is, I think
with the undergrowth; although during low-tide, the upper-vegeta-
tion may gain some advantage from the fact that the layer of
living plants under it retains more water than does the bare sur-
face of the rock.

MARINE ALGAL VEGETATION 119

The following species of the under-vegetation occur in such
quantities that they form associations of considerable extent which
are usually pure, but may sometimes be mixed: —

Hildenbrandia rosea.! Gigartina mamillosa.
Rhodochorton Rothii. Ceramium rubrum.
Sphacelaria britannica. Callithamnion Arbuscula.

Polysiphonia urceolata.

The Hildenbrandia-association is most extensively distributed,
and is found everywhere along the coasts. It usually occurs as a
pure association, though, in many places, Verrucaria mucosa is inter-
mingled with it. Hildenbrandia may also occur at the same height
outside the Fucus-covering, but is then — if the light is not sub-
dued by other plants or projecting rocks — usually of a darker
colour.

The Rhodochorton-association often covers extensive areas,
like a dense, red carpet of felt. Most often it is pure, and appears,
as far as its littoral distribution is concerned, to be confined mainly
to the shady parts of the littoral zone. A few of the other shade-
species may be found intermingled with it in small numbers, which
fact is of minor importance, whereas the occurrence of the epiphyte
Pleurocapsa amethystea is of great importance, as this species is
found only on Rhodochorton Rothit.

R. Rothii does not occur below the Fucus-belt of the littoral
zone until it occurs again at a considerable depth on Laminaria
stems; thus it is found in two distant belts: the shade-belt of the
littoral zone and the Laminaria-belt.

A Sphacelarietum (S. britannica) occurs almost quite pure
in many places over rather large surfaces; it forms a dense covering
on the rock as does R. Rothii. Sphacelaria radicans, Polysiphonia
urceolata and Rhodochorton Rothii occur intermingled.

Polysiphonietum. P. urceolata occurs in a similar manner,
covering rather large surfaces of rock. In places where the species
forms extensive mats, it is usually very low in growth, yet always
considerably higher than Rhodochorton Rothii. A thin layer of fine
clay may often be seen to have accumulated between its basal parts.

A Gigartinetum occurs as under-vegetation, especially in more

exposed places, and is then generally found in the lowest part of
the Fucus-belt or in the Fucus inflatus-association; it is a direct
continuation upwards of the Gigartina-association below.

1 Arranged in accordance with the frequency, the most frequent coming first.

120 H. JONSSON

In addition Ceramieta formed by Ceramium rubrum, and Cal-
lithamnioneta formed by Callithamnion Arbuscula, occur distri-
buted in patches, especially in the Vestmannaeyjar.

The following species, growing in a more scattered manner,
occur also in the under-vegetation of the Fucus-belt: —

Delesseria alata. Plumaria elegans.
Lithothamnia. ;

The species of the under-vegetation thus belong principally to
the red algze; only two species being brown, one blue-green and -
one being a lichen. The majority of the species belong to the shade-
vegetation of the littoral zone.

4. The Enteromorpha-association.

Of the Enteromorpha-species. E. intestinalis is the most common
and the most variable. The variability, no doubt, principally de-
pends upon local conditions, possibly also, on the age of the species.
The typical form is extremely common in the upper littoral zone,
but occurs most luxuriantly in the water-filled depressions. As a
rule, the plants have a social growth, although they rarely cover
large areas. E. prolifera and E.clathrata, on the other hand, occur
in such abundance that it might be justifiable to speak of an asso-
ciation formed of branching Enteromorphas. These species are found
in greatest abundance in the middle littoral zone, often in empty
depressions in the lower part of the Fucus-belt proper, and may
sometimes extend beyond the boundary of the lower littoral zone,
where they then encounter semi-littoral associations, for example,
Dictyosiphonetum, Chordarietum and others. While the typical form
of E. intestinalis seems to flourish during the spring, the branching
forms E. prolifera and E. clathrata are noticeable in the summer.
I have known these two species to occur predominantly in June,
July and August on the same substratum upon which Urospora
Wormskioldii was growing in great quantities in the month of May.

Enteromorpha Linza is also a summer species, and, although
it forms in several places pure Enteromorpheta of lesser extent, plays
only an inferior réle in the Enteromorpha-association. |

In E. Iceland, on the point between Seydisfjéréur and Loémundar-
fj6rdur, at the height of the lower part of the Fucus-belt and a
little lower, I found a Chlorophycee-vegetation which must be con-
sidered to belong most nearly to this association. A Monostro-

MARINE ALGAL VEGETATION 121

metum of Monostroma groenlandicum was here found in abundance,
often entirely covering the boulders and occurring on them, like
U. flacca, closely pressed to the stone-surface with a radiating ar-
_ rangement. In addition, an abundance of E. intestinalis f. compressa
and a few Ulothrix flacca were found. A little lower down, a Uro-
sporetum (U. Wormskioldii) occurred, which can scarcely be separated
from this association; it seemed to form a connecting link with
the semi-littoral communities.

Cladophora gracilis occurred intermingled in the E. clathrata-
association, yet without playing any important role in the vegetation.

A similar association, especially an Enteromorphetum of E. in-
festinalis, is, beyond doubt, very common in other countries. It
seems to be more poorly developed in Greenland (Rosenvinge,
63, p. 205) than in Iceland; in the Ferées (BOrgesen, 12, pp. 714;
715), on the other hand, the Enteromorpha intestinalis-vegetation seems
to be more luxuriant than in Iceland.

5. The Acrosiphonia-association.

This association consists of decidedly filiform, much branched
alge, which grow very socially. During the period of desiccation
they retain the water as a sponge retains it. This circumstance is
mentioned with regard to some of these species by Rosenvinge
(63, p. 202), who says of Cladophora arcta (= Acrosiphonia incurva,
cf. Jonsson, 32, p. 43) that in Greenland it behaves during low-
tide like a sponge saturated with water.!

The principal species in this association are Acrosiphonia albe-
scens and A. incurva. They form individually, pure Acrosiphonieta
in the upper and lower littoral zones, where they cover flat stones
with a densely matted vegetation. On flat rocks the association may
be somewhat widely distributed, in other places it has more the
character of scattered Acrosiphoniela. The density of the vegetation
is due to the structure of these species. As the basal part of the
principal axis is too weak to carry the plant when its branch-
system has developed, lateral rhizoids, which slope downwards, are
developed at an early stage from the principal axis itself and from
the lower branches. These rhizoids often form creeping filaments
from which arise erect shoots, which can be detached from the
parent-plant and thus become independent individuals. The principal

1 Possibly this is the case in an even higher degree with Callithamnion Ar-
buscula (cf. Borgesen, 12, p. 726).

122 H. JONSSON

axis dies away from below and in this way branches, or systems
of branches, with well developed rhizoids are detached from the
parent-plant and become independent individuals (cf. Jonsson, 32).
The rhizoids of one individual become entangled with those of
others, and in this way the basal parts of the entire vegetation be-
come matted together. In addition to this, the lower branches are
hook-shaped, or bent downwards and outwards; thus it easily hap-
pens that they are entangled between the branches of other indi-
viduals, which further increases the matted condition. The upper
branches are directed obliquely upwards, without being entangled
with the branches of other individuals.

An A. albescens-association occurs everywhere along the coasts,
but on very exposed coasts the species generally grows dispersed.
Here it occurs in separate tufts which are, no doubt, composed of
several individuals, densely matted together below, but branching
upwards in various clusters, which are themselves densely matted
together by their hook-shaped branches; the branch-systems above
are, as usual, free. These characteristically matted branch-clusters
are probably an effect of the heavy beat of the waves; the matted
Acrosiphonia “tufts” will not be able to resist the force of the waves
and, even at an early stage, will become divided into very densely
matted branch-clusters.

Acrosiphonia albescens occurs both in the upper and the lower
littoral zone, while A. incurva belongs to the lower littoral zone,
but yet also extends upwards into the pools of the upper littoral
zone, and below low-water mark.

Spongomorphetum. Spongomorpha vernalis grows very so-
cially, but never forms such a dense vegetation as does Acrosiphonia,
although it is sufficiently dense to characterize the spot. The species
has been found in only a few places; it occurs in abundance at
Grotta, where it grows both on a stony substratum and also as
epiphytic vegetation in the Corallina-Gigartina-belt and in the Poly-
siphonia urceolata-association of the lower littoral zone.

A Cladophoretum formed of Cladophora sericea f. (see under
Tide-Pools) also belongs to this association. It forms a densely
matted belt in pools high up in the upper littoral zone. As a rule
it follows the edge of the water round the entire pool.

Cladophora rupestris ought also to be considered to belong to
the Acrosiphonia-association.

An association similar to the Acrosiphonia-association is, no

MARINE ALGAL VEGETATION 123

doubt, very common in adjacent lands. During low-tide the upper-
most free branches appear to be more exposed to desiccation and
possible death in Greenland than in Iceland; in the latter place it
occurs rather frequently. Both in Greenland (Rosenvinge, 63) and
in the Ferdes (Bérgesen, 11, 12) the Acrosiphonia-association is
well represented.

bb. The Shade-vegetation.

To this vegetation are referred certain littoral associations which
occur exclusively in shady places. The shade is produced by the
light being subdued both by a covering of living plants and by
projecting blocks of stones. Thus the greater part of the under-
vegetation-associations of the Fucus-belt mentioned above belong
to the shade-vegetation. In addition, the shade-vegetation grows,
as already mentioned, on the under side of overhanging rocks —
on their in-sloping sides. The vegetation is divided into several
associations which have already been mentioned in connection
with the under-vegetation of the Fucus-belt (cf. p. 118).

The frond differs in form and structure in the various species
of this vegetation. It is a feature common to the whole of the
shade-vegetation to be low and dense in growth. The frond of
Hildenbrandia is a crust which covers the rocks; the others are
finely branching; some, as Sphacelaria and Polysiphonia are
bush-like and are richly and finely branched; Rhodochorton has
a similar mode of branching, but to a considerably less degree.
These three. species often propagate vegetatively by means of run-
ners, which increases the density of the vegetation. Plumaria is
closely and distichously branched; it is tightly adpressed to the
surface of the stones during the time of low-tide and retains much
water between its branches, considered from a biological point of
view it might almost be regarded as leaf-like during the period of
desiccation.

6. The Hildenbrandia-association belongs almost exclu-
sively to the under-vegetation of the Fucus-belt, and of the shady
localities in the littoral zone (see above, p. 118).

7. In shady places the Rhodochorton-association, the
Sphacelarietum britannici, and the Polysiphonietum ur-
ceolatzw behave in a similar manner outside the Fucus-belt as
they do within it (see above). They may occur either as pure as-

124 ‘H. JONSSON

sociations, and are then dominant here and there in patches, or
the species may be found intermingled with each other. Besides
these associations a Plumarietum, consisting exclusively of Plu-
maria elegans, is found in many places. This association is darker
in colour than the other red-algze associations of shady places; it
occurs frequently in S. and SW. Iceland. Intermixed in it occur
Callithamnion scopulorum and Chantransia virgatula.

Rhodochorton Rothii is sometimes found high up in the littoral
zone on flat rock-surfaces exposed to the light and to the beat of
the waves, but then it grows in small globular cushions (f. globosa).
Consequently, this globetum of Rhodochorton Rothii does not be-
long exclusively to the shade-vegetation.

On flat surfaces in the shade the usual arrangement is that
the decided shade-associations occur at the bottom, where the light
is feeblest, e. g. the Sphacelarietum, Rhochortonetum, Polysiphonietum,
Plumarietum; at the top, where the illumination is stronger, light-
loving species occur, e.g. Pylaiella, Ulothrix, or others. Near Rey-
kjavik a vertical section of such a surface showed uppermost, at
the edge, Pylaiella littoralis, next Rhodochorton Rothii f. globosa, and
lowest of all Plumaria elegans.

In a grotto in the Vestmannaeyjar, where the illumination was
very feeble, Enteromorpha intestinalis f. micrococca occurred on the
roof, Ceramium acanthonotum grew rather high up on the walls,
and Plumaria elegans, together with Delesseria alata, formed a belt
lower down the walls.

A vegetation corresponding to the shade-vegetation appears to
occur in Greenland where Hildenbrandia rosea, Ralfsia clavata and
Verrucaria mucosa form the undergrowth in the Fucus-belt and
in other places (Rosenvinge, 63, pp. 198 and 203). Rhodochorton
Rothti and Sphacelaria britannica also appear to grow in a similar
manner in Greenland (Rosenvinge, 63, p. 205).

A comparison with the Ferées shows some difference. The
vegetation in the groltoes in the Ferées (Bérgesen, 12, p. 739),
however, resembles in its main features the Iceland shade-vegetation,
and, in addition, a similar vegetation is beyond doubt to be found
in fissures and clefts of the rocks in the Ferées, but the mode of
occurrence of the species is not the same. Thus, in the Ferées (B6r-
gesen, 12, p. 711), the Hildenbrandia-association appears to have a
much wider distribution upwards and to occur in fully illuminated
localities. Rhodochorton Rothii seems to occur in a similar manner

MARINE ALGAL VEGETATION 125

in the Ferdes (Bérgesen |. c., p. 718) as it does in Iceland, with
this difference, however, that the species extends higher upwards
in the Feerées and, also, frequently grows in fresh-water in the
latter place.* Sphacelaria britannica grows similarly in the Ferées
(Borgesen, 13, p. 482).

According to Foslie (18) a similar shade-vegetation appears to
occur in northern Norway.

This vegetation is a natural upward continuation of the semi-
littoral Polysiphonia urceolata-association mentioned below.

cc. The Vegetation of Tide-Pools.

Where there is a rocky coast, depressions of varying sizes occur
everywhere in the littoral zone. These depressions may be divided
into two groups: The tide-pools of the upper littoral zone, and the
tide-pools of the lower littoral zone. The plant-growth in these tide-
_pools does not form a vegetation-unit, and is chiefly composed of
species either scattered or of social growth which belong to the
littoral or semi-littoral communities; they are, however, here treated
separately in order to further characterize the illustration of the
littoral zone given in the above description.

Tide-Pools of the Upper Littoral Zone. Of these the
uppermost, which are almost on the level of Fucus spiralis, are of
the greatest interest, as they often contain species, or forms of
species, which do not occur elsewhere in the littoral zone. These
species are Cladophora sericea f. and Fucus inflatus f. linearis.

The water in the uppermost pools is not replenished with the
recurrence of each high-tide, and this is especially the case in calm
weather during neap-tide; if, simultaneously, dry weather occurs,
the water evaporates, and this the vegetation cannot endure for any
length of time. In rainy weather, on the other hand, the pools are
filled with fresh water, and should this happen during neap-tide
the salinity would be insufficient for any of the species to exist.
At spring-tide the water in the pools becomes mixed with a fresh
supply of sea-water, and the vegetation then lives, for a time, under
good conditions. Thus, there are times during which the conditions
in the pools are not favourable to algal life.

Cladophora sericea grows very socially in many places and, in

1 When I visited the Fzerées in October, 1897, I was at first surprised to

find R. Rothii growing in streams at and above the upper limit of flood-tide; such
a situation for it in Iceland was unknown to me.

126 H. JONSSON

small pools, often forms a continuous fringe, the upper branches
either reaching to or lying on the surface of the water. In such
pools Chetomorpha tortuosa sometimes occurs in fair abundance
loose upon the surface of the water; its filaments are usually densely
matted together.

Fucus inflatus f. linearis grows even more socially. At times it
is almost the dominant species in the smaller pools, although, rather
frequently, several other species are found intermingled with it.
This form is a biological variety of Fucus inflatus which, in the
pools, exists evidently under less favourable circumstances; this is
one cause of its small size and feeble structure, although another
is that it is not exposed, to any extent worthy of mention, to the
beat of the waves. Rosenvinge has especially shown this to be
the case as regards Greenland. Rosenvinge explains the frequent
occurrence of this form in the pools by the fact that the eggs of
F. inflatus are carried into the water-filled depressions by the move-
ment of the water and accumulate there. This explanation is un-
doubtedly correct, and, as Rosenvinge points out, all intermediate
stages between the feeble pool-form and the typical form can be
demonstrated. To any one who has seen this endless variation in
nature, it seems so certain that it is due to the influence of outside
factors, that experimental proof is almost superfluous.

The uppermost pools are generally extremely poor in species;
and, besides those already mentioned, only Enteromorpha intestinalis
occurs in any great abundance. Where the coast is exposed, the
uppermost pools may, however, have a resemblance to the lower
ones of the upper littoral zone — a natural consequence of the
exposure. On more exposed parts of the coast a fringe of small
Monostroma Grevillet is often found, almost on the surface of the
water itself. At one place in E. Iceland I took the temperature of
such a submerged plant-covering, and the thermometer showed
20° C. (June 13). The vegetation was also somewhat injured, and
evidently did not prosper under these conditions.

High up on a rocky coast to the south of Vattarnes in E. Ice-
land, I came across a pool-vegetation. I did not measure the alti-
tude of the spot, but I do not think that I was greatly mistaken
in estimating it at 70—100 feet above sea-level. As regards the place,
I noted in my dairy — “High rocky coast, land-plants grew round
the alga-pools. The water in the pools must be replenished with
rain and heavy surf, which sometimes fail for long periods during

MARINE ALGAL VEGETATION sya

the summer. Many pools filled with decaying and dying alge.”
The occurrence of alge so high up can be imagined only on a
very exposed coast facing the open sea, and even there it would
be exceptional.

The dominant species of the vegetation in these high-lying pools
consisted of Fucus inflatus f. linearis. Intermixed occurred Cheeto-
morpha Melagonium — which I never before had seen so high above
sea-level — Acrosiphonia sp., Dictyosiphon foeniculaceus, Pylaiella
littoralis and Enteromorpha intestinalis f. typica. The undergrowth
consisted of Hildenbrandia rosea.

In another somewhat elevated and exposed place in the vicinity
of Vattarnes, a number of small pools were found just below the
Verrucaria maura-belt. Hildenbrandia and Verrucaria mucosa grew
on stones at the bottom of these pools; in addition, Fucus inflatus
f. linearis occurred fairly abundantly, although dying in the pools,
which were deficient in water.

The lower pools in the upper littoral zone have a much more
luxuriant vegetation. Here various littoral and semi-littoral species
can grow in fair abundance. The water in these pools is replenished
at each high-water, so here, the plants exist under fairly favourable
conditions. The following species may occur dominantly or abun-
dantly: — Fucus inflatus f. linearis, Halosaccion ramentaceum, Mono-
stroma fuscum, Enteromorpha intestinalis, Monostroma ee Dic-
tyosiphon foeniculaceus and Castagnea virescens.

Many species are found growing scattered, of which the fol-
lowing are most frequently met with: —

Polysiphonia urceolata. Phyllitis fascia.

Porphyra miniata. Pylaiella litoralis.
Rhodomela lycopodioides. Scytosiphon Lomentaria.
Rhodymenia palmata. Chetomorpha Melagonium.
Chorda Filum. C. tortuosa.

Chordaria flagelliformis. Cladophora gracilis.
Coilodesme bulligera.! Monostroma undulatum.
Ectocarpus confervoides. Ulothrix flacca.

Elachista fucicola. Urospora Wormskioldii.

The under- vegetation often consists of Ralfsia deusta, Litho-
‘thamnion circumscriptum and Hildenbrandia rosea.

Taken on the whole, the majority of the littoral species un-
_doubtedly may be met with in the pools, and it should be especially

1 It may be observed, as regards Coilodesme, that it is the more inflated
the lower the water is in the pools.

128 - H. JONSSON -

noted that, when the semi-littoral species occur in the upper littoral
zone, they are usually confined to the pools, a fact which proves
that they do not essentially belong to the upper littoral zone.

b. The Semi-littoral Zone.

The upper boundary of this vegetation is just at the lower
boundary of the Fucus-belt. The vegetation covers the lower littoral
zone, and extends, usually in the form of stragglers, below the limit
of low-tide, down between the uppermost extensions of the vegeta-
tion of the Laminaria-belt, which in many places reach right up
to the limit of low-tide. The semi-littoral communities consequently
srow side by side with the Laminaria-associations below the limit
of low-tide, to a depth of about 10 metres; they also occur as epi-
phytic vegetation on the Laminarie at the depth mentioned.

Thus, the semi-littoral zone is that between the lower edge of
the Fucus-belt and the Laminaria-belt. The breadth of the zone
depends on the slope of the coast. If the coast is steep the zone
is narrow, but if the coast slopes gently, it is broad. In this zone
no single dominant community of extremely social and large species
occurs, like, for example, the Fucacee-community in the littoral
zone, and the Laminariaceew-community in the sublittoral zone. The
zone appears to lie too low for Fucacee and too high for La-
minariacee.

Green and brown alge occur in abundance in the semi-littoral
zone, but the Rhodophycee are most richly represented. The semi-
littoral associations occur both laid bare during low-tide and also
continuously submerged to the depth mentioned.

It is easy to follow the upper boundary of the zone, even in
places where the Fucacee are absent. The lower boundary can also
be ascertained with comparative ease, if the large Laminarie only
are followed, and if the observer is not led astray by the small La-
minarie, which may occur in the depressions and pools of the
lower littoral zone. |

The semi-littoral zone comprises several associalions which. play
a rather considerable part in the vegetation.

By authors who describe the algal vegetation on coasts where
there is a change of tide these associations are generally considered
to belong partly to the littoral and partly to the sublittoral vegeta-
tion. On coasts where there is no tide, the littoral vegetation has,

MARINE ALGAL VEGETATION 129

however, been subdivided. Reinke (58, p. 10) divides the littoral
region near Kiel into an upper zone which is always laid bare at
low-water, and a lower zone at a depth of 2—4 metres. So far as
I can judge from the species enumerated, Reinke’s upper zone
corresponds approximately with the previously mentioned upper
littoral zone, while the lower zone corresponds only in part with
the semi-littoral zone here described. Gran (24, p. 11) records under
the term “sublittoral vegetation” transitional formations which evi-
dently, for the most part belong to the semi-littoral communities.

On the west coast of Sweden (Kylin, 45) the border-line be-
tween the littoral and sublittoral algal vegetations is, on the coast
of Bohuslan, at a depth of 3—4 metres, and at Halland at a depth
of about 5 metres. The upper part of the littoral zone seems to
correspond to some extent with the above-mentioned upper littoral
zone, while the lower part has something in common with the
semi-littoral zone.

Where there is no tide, the boundary between an upper and
a lower littoral zone is not, I think, so sharply defined.

8. The Monostroma-association.

This vegetation is composed of relatively large, membranaceous,
green algze. Monostroma fuscum and M. Grevillei form associations
in a rather considerable number of places in protected localities in
the fjords, below the limit of low-tide, and to a depth of at least
4—6 metres. There, the association is most sharply defined, although
it is fairly frequently found intermingled with other semi-littoral
associations. In the lower littoral zone also, an abundant Mono-
stroma-vegetation frequently occurs, both on a rocky substratum,
and also very often as epiphytic vegetation in other associations,
as, for example, the Halosaccion-association, the Corallina-association,
the Polysiphonia urceolata-association and others.- In water-filled
depressions in both the upper and lower littoral zone the Mono-
stroma species often occur abundantly.

Monostroma Grevillei var. arctica seems to belong more imme-
diately to the littoral zone. In many places it is found entirely laid
bare, sometimes on a clayey substratum, when it often attaches
itself to small individuals of Mytilus edulis, and sometimes where
the substratum of the littoral zone is pebbly. During April and May
this vegetation is rather characteristic, because then, the species
occurs for the greater part in the inflated stage. The bladders vary

The Botany of Iceland. I. 9

130 H. JONSSON

greatly in size and form and may be at times considerably elon-
gated, bearing then a striking resemblance to an Enteromorpha.
Under calm conditions the inflated stage continues until the spores
at the apex of the frond are ripe.

In several places in the fjords Monostroma Grevillei var. typica
forms a luxuriant, characterizing vegetation at a depth of about
3—d metres.

Monostroma fuscum very frequently forms associations of con-
siderable extent in the fjords at a depth of about 4 metres. The
specimens of this species which occur there are generally very large
(f. grandis). These large specimens are rather frequently found at
low-water mark, detached or floating at the water’s edge, and then
it may generally be taken for granted that a Monostrometum exists
further out at a depth of about 4 metres.’ Both in the fjords of
E. Iceland and in Eyjafjéréur in N. Iceland this Monostrometum oc-
curred in the same characteristic manner, viz. alternating with a
Chordarietum, a Dictyosiphonetum (D. foeniculaceus), a Halosaccione-
tum, and a Rhodymenietum. Generally the order was that Rhodymenia
grew deepest (as deep as 12 metres), and M. fuscum most frequently
uppermost (at about 4 metres). Alaria and Laminaria saccharina, in
addition, may be found growing scattered in such places, which
makes the character of the vegetation still more heterogeneous.

Monostroma undulatum does not occur so abundantly as do the
other Monostroma species. It is found growing rather luxuriantly,
however, in pools in the lower littoral zone, and on the stems of
Laminaria in comparatively low water.

Ulva Lactuca, also, is most nearly related to this association.

This association is very common in the Ferées (cf. Borgesen,
12, pp. 731 and 764), and occurs also in Greenland (Rosenvinge, 68).

9. The Chorda-association.

This association is composed of rather large, brown alge. The
fronds are either non-branching, thick filaments (Chorda, Scytesiphon),
or else branched, as in almost all the others; one, Coilodesme, how-
ever, is almost leaf-like.

This association has an insignificant distribution, and is found
usually in patches, where the substratum is clayey or somewhat
muddy. It occurs both in the lower littoral zone above low-water
mark, and to a depth of at least 4—6 metres. The members of the

+ Strémfelt (70, p.11) mentions this Monostrometum at Eskifjéréur.

MARINE ALGAL VEGETATION 131

association are as follows: — Chorda Filum, C. tomentosa, Chordaria
flagelliformis and Dictyosiphon foeniculaceus. Scytosiphon Lomentaria,
Castagnea virescens and Coilodesme bulligera are also most nearly
related to this association. Some of the species occur in such abun-
dance that they may be said to form an association; this applies
more particularly to Chorda Filum. A pronounced Chorda Filum-
association occurs in many places at a depth of almost 3—4 metres
(measured during low-water of spring-tide). The individuals are ex-
tremely long, about 6 metres and, to a great extent, float on the
surface at low-tide. The substratum is, as a rule, clayish with
pebbles here and there. This association is often almost pure, but
scattered individuals of Laminaria saccharina are not rare, although
they play no essential réle in the vegetation. Chorda Filum also
grows above low-water mark in the lower littoral zone, but there
it does not really form associations, although it may grow luxuri-
antly in many places.

Chorda tomentosa is also social and grows more luxuriantly
below low-water mark than above it. It often occurs in abundance
as a component of the sublittoral vegetation.

Chordaria and Dictyosiphon foeniculaceus are species which grow
socially, and rather frequently a Chordarietum or a Dictyosiphonetum
is found, usually with a limited distribution both below low-water
mark and above it, especially in water-filled depressions in the
littoral zone. The remaining species which have been mentioned
are also of rather social growth in many places, both below and
above low-water mark, especially in pools. Coilodesme, for example,
was rather frequent in tide-pools in E. Iceland, and sometimes at
a very high level, but then the individuals were frequently inflated ;
in SW. Iceland the species grew at and below low-water mark in
company with Chorda Filum and Saccorrhiza.

With the exception of the above-mentioned Chorda Filum-asso-
ciation, this vegetation occurs usually in patches, distributed be-
tween other associations. Thus it is closely connected with the
Enteromorpha clathrata-association at the boundary between the
upper and lower littoral zones, and with the Rhodymenia-association
and the Monostroma fuscum-association at a depth of about 4 metres,
as has been previously mentioned.

In the Ferées a similar vegetation occurs as a part of the
Stictyosiphon-association (Bérgesen, 12, pp. 762—763).

g*

132 H. JONSSON

10. The Community of Rhodymenia.

The species are Rhodymenia palmata and Halosaccion ramen-
faceum, both of which occur along the coasts in great abundance
as pure associations. These two associations most frequently ac-
company each other, and seem to demand somewhat similar con-
ditions of life. Halosaccion, however, extends the higher up in the
littoral zone, but is then almost always submerged in water-filled
depressions in that zone, while Rhodymenia extends the further
down below the limit of low-tide. In Rhodymenia the form of the
thallus is leaf-like and branching; in Halosaccion it is round and
excessively or slightly branching.

The Rhodymenia-association. On regarding a steep rocky
coast, where the succession of the associations is always most easily
observed, it is seen that a luxuriant Rhodymenia-vegetation com-
mences even at the lower boundary of the Fucus-belt. In many
places the species occurs so ‘socially that it predominates as a
characterizing plant over relatively large stretches, both in the lower
littoral zone and far below the limit of low-tide, to a depth of
about 12 metres. On a gently sloping rocky coast, the upper boun-
dary of the association is not so sharply defined, but if proper
allowance is made for the depressions and elevations in such a
littoral zone the boundary is fairly easily ascertained although it
may then he in very many curves. On a gently sloping pebbly
coast, the same regular boundary is found as.on a steep rocky
coast and at about the same height, although the Fucacee-community
is not present there. :

Various alge may occur on stones under the fronds of the
Rhodymenia, as, for instance, Hildenbrandia rosea, Ralfsia clavata,
Sphacelaria radicans and others; also a number of epiphytes, espe-
cially Myrionemacee and Ectocarpacee, often grow on old individuals
of Rhodymenia palmata.

Rhodymenia occurs also epiphytically on the stems of Laminaria
in the upper part of the Laminaria-belt. ©

The Rhodymenia-vegetation does not seem to be so luxuriant
in Greenland (Rosenvinge, 63) as in Iceland. Possibly this is true
also of the north of Norway (Foslie, 18). In the Ferées the
Rhodymenia-vegetation is luxuriant, but seems to differ somewhat
from that of Iceland, as it consists of a form with lower and more
dense growth and narrower branches; this form also extends further
up (Borgesen, 12,>p) 727)

MARINE ALGAL VEGETATION 133

The Halosaccion-association also commences below the
lower boundary of the Fucus-belt, and extends from there to a
depth of about 5 metres below low-water mark. The species grows
very socially, entirely covering the rocky substratum upon which
it grows; it is very variable, and, while f. densa seems to extend
rather high up, in pools in the littoral zone, it is f. robusta which,
as a rule, reaches to the greatest depth. F. subsimplex is very com-
mon just below the Fucus-belt, where it grows so densely that it
covers the substratum completely. It is very often interwoven with
byssal-threads of Mytilus edulis. In this form, as in the laid-bare /f.
robusta, inflated shoots occur fairly frequently. As is the case with
Rhodymenia palmata, this species is very frequently decoloured in
the lower littoral zone; yet in both species the lower part of the
frond is, as a rule, reddish in colour.

Of the epiphytes, Elachista fucicola is especially frequent, and
various other species may also occur closely applied to Halosaccion,
such as Porphyra miniata, Monostroma fuscum, M. Grevillei and others.
At times the Monostroma species may be so abundant that they
may be said to play a distinct rdle as epiphytic vegetation. Among
the Halosaccion individuals, Dumontia filiformis, Chetomorpha Mela-
gonium and others often occur growing scattered at the very limit
of low-tide.

A similar Halosaccion-vegetation occurs in northern Nor-
way (Foslie, 18), and probably on the arctic coasts as well (Kjell-
man, 36; Rosenvinge, 63). In the Ferdes the association is
poorly represented (Bérgesen, 12, 13).

11. The Polysiphonia urceolata-association.

At and about low-water mark in the lower littoral zone, an
association is found consisting principally of excessively branching,
red alge which I will name after the species Polysiphonia urceolata,
which is dominant in the association. This vegetation frequently
occurs on a flat or convex substratum of rock (lava-substratum)
and often forms, especially in SW. Iceland, for example at Grotta
near Reykjavik, a broad belt around Corallina-pools, near low-
water mark.

The species which occur in greatest abundance in this asso-
ciation are Polysiphonia urceolaia, Cystoclonium purpurascens and
Rhodomela lycopodioides.

The Polysiphonia urceolata-association is very luxuriant

134 H. JONSSON

in many places at about low-water mark, and often covers rather
large stretches of rock with a dense but, at times, low vegetation.
As previously mentioned, it grows luxuriantly on flat rocks, without
any protection whatever during the period of exposure, which is cer-
tainly short, and indeed exceedingly short during a heavy sea. Here,
as in the upper littoral zone, the association occurs also on the face
of the rocks, and the species seems as a rule to be larger than
when on flat rocks. The association appears to have an extended
vertical distribution since, as previously mentioned, it occurs as
shade-vegetation or undergrowth in the upper littoral zone; further-
more it must be assumed that it has a larger sublittoral distribu-
tion than is shown by the dredgings, as it has been found outside
the 10-metre contour (see below). From what I have seen, the
stretch of shore just above and somewhat below low-water mark
is essentially the home of this association. It usually grows on a
rocky substratum and on Laminaria stems at no great depth.

Cystoclonium purpurascens grows socially in many places
both on a rocky substratum and on Gigartina. Sometimes it occurs
in such abundance as an epiphytic vegetation in the Gigartina-
Corallina-belt, that it is the alga which characterizes the vegetation, —
and not until the plants are moved aside is it seen that they are
attached to a living substratum. On Cystoclonium various epiphytes
occur, for example, Chantransia, Monostroma Grevillet and others.

Rhodomela lycopodioides very frequently grows scattered,
and then plays only an insignificant rdle in the vegetation; but
Rhodomeleta of limited extent also occur, often in contact with the
Polysiphonia urceolata-associations.

Ceramium rubrum, C. acanthonotum and Callitham-
nion Arbuscula really belong to this association. In many places
these species grow fairly socially and Ceramieta of C. rabrum and
C. acanthonotum and Callithamnioneta of limited extent occur both
on rocky substrata and on one of Gigartina; however, I think that
these species occur too sparsely to be termed association-formers.

Sphacelaria radicans also belongs to this association. Often,
even at low-water mark, it covers flat stones with a dense vegeta-_
tion, but though these small Sphacelarieta are considerably distri-
buted, yet they cannot be called associations.

In the Feerdes a similar Polysiphonia urceolata-vegetation occurs
(Borgesen, 12, p. 731).

:
MARINE ALGAL VEGETATION 135

12. The Community of Corallina.

The members of this community are Corallina officinalis, Gigar-
tina mamillosa, Chondrus crispus and Ahnfeltia plicata. These species
occur as a rule in luxuriant and more or less sharply defined as-
sociations, which very frequently occur together, and may therefore
be regarded as nearly related to each other.

The fronds are branched, and their consistency is on the whole
firm because, as is known, Corallina is encrusted with calcium car-
bonate, Ahnfeltia is horny and Gigartina and Chondrus are car-
tilaginous.

Gigartina and Corallina generally occur in a belt at the limit
of extreme low-water; in my diary I have always called this belt
the Gigartina-Corallina-belt. Gigartina, however, extends higher up;
on exposed coasts right up to the Fucus-belt, and even into that
_as under-vegetation; but, where Gigartina and Corallina meet, there
is most frequently a mixed belt. These associations belong to S.
and SW. Iceland.

The Corallina-association occurs most luxuriantly about low-
water mark. The species grows extremely socially, and entirely
covers depressions in the littoral zone which are more or less filled -
with water. The association occurs on somewhat exposed and also
on very exposed coasts, but almost always in depressions surrounded
by rocks upon which the waves break; yet I have seen it, where
the exposure is but slight, covering the face of rocks below low-
water mark. Only rarely have I obtained Corallina by dredging in
greater depths, as, for example, on the north coast, at a depth of
about 14 metres, where it seems to be present in abundance. It
may be assumed with certainty, however, that this association has
a much wider distribution below the limit of low-tide than is
shown by the dredgings, and with exceptional low-tides it can be
seen that in many places the Corallina-vegetation covers the rocks
as far as the eye can reach.

On a very exposed coast I have met with Corallina growing
socially in water-filled depressions at a considerable higher level,
sometimes on a level with the upper part of the Fucus-belt. Here,
however, with the exception of the lowest part of the frond, it is
quite white in colour, and has evidently strayed outside its real
domain. The spores have been carried to this height above the true
Corallina-belt by the beat of the waves, and have been retained in
the depressions. It can also thrive fairly well at this height during

®

136 H. JONSSON

the autumn and winter, both because the light is feeble, and be-
cause the increased high seas following stormy weather to some
extent compensate for the difference in height. But it is in the
spring and summer that it is most evident that Corallina has
really extended too high up. According to Bérgesen’s description
(12) it appears to extend still higher up in the Ferées.

In the Corallina-association an abundant epiphytic vegetation
may occur, both of small algz like Chantransia and of larger alge
such as Monostroma Grevillet, Spongomorpha vernalis, Acrosiphonia
albescens and also the Leathesia-associations. Furthermore, Ceramium
rubrum, Cystoclonium, Delesseria sinuosa and D. sanguinea occur, and
other red alge, often in great quantities. When to this is added
the fact that Gigartina is often abundantly intermingled with those
already mentioned, it is easily seen that this mixed vegetation as-
sumes quite a different character, according as to whether the
brown-red Gigartina and Ceramium or the light-green Monostroma
and Spongomorpha predominate. This characteristic appearance dif-
fers entirely from the usually monotonous appearance of the Coral-
lina-belt. This epiphytic vegetation must be considered to form as-
sociations which do not really belong to the Corallina-vegetation in
any other respect than that of having it for a substratum.

The Gigartina-association is widely distributed on very
exposed coasts; it often is of very great breadth and, as already
frequently mentioned, extends in under the Fucacee as undergrowth.
Where the exposure is less, it does not reach so high; but yet, in
the lower littoral zone there is, as a rule, a distinct Gigartina-belt,
which most frequently occurs above the limit of low-tide. The
Gigartina-vegetation extends also below the limit of low-tide, but it
seems to belong most closely to the lower littoral zone. The belt
is quite characteristic, and can often be seen from a distance, as
the colour is in strong contrast to that of the Fucacece-community.
The species is of very social growth and is usually dominant where
it occurs; not rarely, however, a few species occur intermingled
with it, especially in the Vestmannaeyjar and at Ondverdarnes, two
very exposed localities. In the Gigartina-belt Corallina may occur
lowest, Callithamnion Arbuscula is sometimes plentifully intermixed
with the Corallina and occurs also in abundance as an epiphyte,
and Ceramium acanthonoium occurs rather frequently and often
abundantly. In the Vestmannaeyjar Callithamnion scopulorum occurs
rather frequently as undergrowth. In addition, Ceramium rubrum,

MARINE ALGAL VEGETATION £37

Delesseria alata, Acrosiphonia, Polysiphonia urceolata, Plumaria elegans
and Rhodymenia palmata occur. Porphyra umbilicalis occurs as an
epiphyte in the Vestmannaeyjar, and also Cystoclonium, Polysiphonia
urceolata and others.

The Gigartina-belt is very luxuriant in the Vestmannaeyjar and
at Ondverdarnes; it may be said to be, on the whole, luxuriant in
S. and SW. Iceland. As regards the relations between Gigartina and
Corallina, the following observation from the Vestmannaeyjar may
be recorded. At Brimsuré, on the south-east side of the inhabited
island, where the littoral zone consisted of large, although not par-
ticularly high boulders, these were entirely covered above by a
dense Gigartina-vegetation, while Corallina formed just as dense a
belt around them below.

Chondrus crispus also grows socially in S. and SW. Iceland.
It is true that Chondreta of lesser extent occur usually at or near
low-water mark, but nowhere does the species occur nearly as
luxuriantly as does Gigartina. The Chondrus-vegetation is most
luxuriant in the Vestmannaeyjar and at Eyrarbakki. Between the
skerries off the latter place, the broad-fronded form grew in abun-
dance, both above and a little below the limit of low-tide. In both
the places mentioned, which belong to S. Iceland, it grows in such
abundance that the vegetation might almost be termed an associa-
tion; in SW. Iceland on the other hand, it seems to occur more
sparsely, and the small Chondrefa may then be considered to be-
long to the Gigartina-association.

Ahnfeltietum. Ahnfeltia plicata grows socially in S. and SW.
Iceland and usually forms a narrow belt at and below the limit of
low-tide. The individuals are very frequently matted together by
the byssal threads of various small molluscs, and worms and quan-
tities of snails are found between the plants. In reality this vege-
tation is more nearly related to the Corallina-association than to
the Gigartina-association. This species grows also scattered among
Corallina and Gigartina.

The intermingled species are only few in number, for example,
Ralfsia deusta which may occur abundantly in small depressions,
and Leathesia difformis which sometimes occurs in abundance as
an epiphyte. Ahnfeltia is most frequently decoloured above low-
water mark.

Chetomorpha Melagonium occurs rather frequently, grow-

138 H. JONSSON

ing scattered in the Corallina-Gigartina-belt, without playing any
further part in the vegetation.

The Leathesia-association is here mentioned in connection
with the Corallina-Gigartina-belt. The brown, spherical, cartilaginous
Leathesia difformis is found in abundance in this belt only, and I
prefer to mention it here rather than to place it in the Chorda-
association. The species occurs only as an epiphyte, not only on
Ahnfeltia but also on Corallina, Gigartina and Chondrus, and is often
wonderfully numerous. The size varies greatly, often the globules
may be rather large and, by their yellowish colour greatly alter
the appearance of the vegetation. It often almost entirely covers
rather extensive Corallineta. The species is a summer-form, which
does not occur in any quantity worthy of mention until the month
of June, flourishes during July and August, and disappears in Sep-
tember, at any rate in SW. Iceland. |

Small specimens of Leathesia occur also on Rhodymenia palmata.

13. The Crustaceous alga-association.

At low-water mark and in the lower littoral zone, there occurs
a crustaceous algal vegetation which may be considered a direct
continuation of the sublittoral crustaceous algal vegetation (see be-
low, p. 148). Here, the species are, for the most part, the same, e. g.
Lithoderma fatiscens and Lithothamnion compactum. Both these
species often have a somewhat considerable distribution in the lower
littoral zone. The Hildenbrandia-association mentioned as existing
in the upper littoral zone also occurs here. Lithothamnion leve and
Phymatolithon polymorphum also occur in the lower littoral zone.
In addition, we have Ralfsia deusta which, in many places, forms
patches upon the bottom of pools in the lower littoral zone, and
plays rather an important role in the vegetation.

Tide-Pools of the Lower Littoral Zone are most fre-
quently depressions which are either directly connected with the
part which is constantly submerged or separated from it by a ridge;
which may happen to be the case is unimportant as the period of
exposure in this part of the littoral zone is extremely short, as is
also seen from the fact that the vegetation in these depressions
consists of sublittoral associations, or more correctly, of stragglers
from them. Thus, Laminaria and Alaria species frequently occur in

MARINE ALGAL VEGETATION 139

these depressions which fact will be mentioned again later on.
Some of the depressions are occupied by semi-littoral associations,
thus, Corallineta, Gigartineta, Chondreta, Monostrometa, Ceramieta, etc.
frequently occur, and, in addition, several of the species which be-
long to these associations are found growing in a scattered manner.

As mentioned above (p. 125), the vegetation in the pools is
highly heterogeneous, and, in the large pools it can frequently be
seen that the associations or their representatives arrange them-
selves in belts, here on a smail scale in the same manner as they
do on a larger scale outside the pools.

c. The Sublittoral Zone.

The sublittoral vegetation covers the sea-bed from the limit of
low-tide down to a depth of 40—60 metres, and perhaps to an even
greater depth. Under normal circumstances it is not exposed during
low-tide; yet it may happen that the uppermost Laminarie, espe-
cially when small, become exposed during extreme low-water, but
this must be considered exceptional. What especially characterizes
this zone is the circumstance that the associations are always sub-
merged. The associations are certainly few in number, but most of
them have a remarkably wide horizontal distribution, and the vege-
tation, taken as a whole, is homogeneous. With the exception of
illumination the conditions of life must be supposed to be stable;
in any case, compared with the conditions of life in the littoral
zone, they are unstable to a very slight degree. In the littoral zone
the change of season is noticeable, but in the deep, under normal
circumstances, these changes are very slight. The character of the
vegetation is therefore nearly the same all the year round.

The Laminariacece vegetation, as previously mentioned, is do-
minant in this zone and stretches in a broad belt along the coasts.
Beyond the Laminaria-belt another narrower belt occurs composed
almost exclusively of Rhodophycee.

14. The Community of Laminariacee.

This community occurs especially on a rocky substratum, and
extends over large areas of the sea-bed from about the limit of low-
tide to a depth of about 30 metres. It forms a belt round the
coasts, and varies in breadth according to the conditions of depth
and the nature of the substratum. This belt is for the most part

140 . H. JONSSON

continuous, although only as far as the substratum is favourable
for its development. By reason of the nature of the substratum,
both the upper and the lower boundaries often have an irregular
course, and stragglers from the main body of the vegetation often
occur. Those Laminariacee which occur in the low-lying tide-pools
must be regarded as stragglers from the Laminariacee -community
which exists below. In the same way there are stragglers which
extend outwards into deep water, as some members of the com-
munity have been found at a depth of 40 metres. The community
occurs both on exposed coasts and on those which are partly ex-
posed, as well as on sheltered coasts. It is composed of perennial
species with, as a rule, strongly developed organs of attachment, a
stem-like stipe and, as a continuation of this, a lamina or leaf-like
portion which is originally undivided, but in some of the species,
is later divided by longitudinal slits into many lobes. The species
are the largest of all the algal species in the northern seas: they
srow both in pure associations and highly intermingled with one
another. The community may be said to resemble a “forest” on
the sea-bed; sometimes the “forest” is pure, sometimes mixed, and
it has its undergrowth, its “stem” epiphytes and its “leaf” epiphytes.

The species which occur are Saccorrhiza dermatodea, Laminaria-
species and Alaria-species. Like the Fucacee-community in the lit-
toral zone, the Laminariacee-community is composed of a few species
of very social growth, and, just as the Fucacecee-community forms the
greater part of the bulk of the vegetation in the littoral zone, so
does the Laminariacee-community below the limit of low-tide. If the
range of the associations differs in depth this will be mentioned
when they are described. |

The Associations of the Laminariacee Community
occur in many places in fairly regular succession from the coast
out towards the deep sea. Thus, often quite close to the coast,
Laminaria saccharina or Alaria esculenta is found occurring in very
great abundance in pure or mixed associations; beyond is found a
belt of Laminaria digitata; and deepest of all Laminaria hyperborea.
But the order is not always so regular, and at lesser depths it is
frequently seen that the species occur socially on small areas of
the substratum, sometimes one species being dominant and some-
times another. The species may also occur scattered amongst one
another, especially at lower depths. There is a difference in the

MARINE ALGAL VEGETATION 141

character of the community in sheltered and in exposed places,
which is evident from the description of the association given be-
low. In sheltered places the calm-water character predomi-
nates; to this belong the Saccorrhiza dermatodea-association, the
Alaria Pylaii-association, the Laminaria fcréensis-association and
the calm-water associations of L. saccharina and L. digitata. Of the
very much exposed associations, the only essential one to be re-
corded is the Sfenophylla-association (see under L. digitata). In ad-
dition, a difference is evident according to the depth, and the as-
sociations then occur either with a shallow-water character
or with a deep-water character (see below).

In its main features, this community occurs in a similar man-
ner on the coasts of adjacent countries. The communities of S. and
SW. Iceland greatly resemble those of the Ferées, as has been fre-
quently mentioned, and also those of western Norway (Boye, 10;
Hansteen, 25) and of Finmark (Foslie, 18).

The Saccorrhiza dermatodea-association. I have most
frequently found this species just below the limit of low-tide, where
it is of medium size, and grows scattered. In water-filled depres-
sions in the lowest part of the littoral zone which, although they
lie above the limit of low-tide, belong from a biological point of
view to the lower-lying area, the species is often very social and
forms pure associations. I have found it growing very socially at
a greater depth (22—28 metres) within Reydarfjérdur in E. Iceland
off Hélmanes or thereabouts; the specimens which occurred there
were of large size. When the various Ectocarpacee which may occur
on old individuals are excepted, the plants are usually free from
epiphytes. The association develops best in somewhat sheltered places.

The Alaria Pylaii-association. Alaria Pylaii, as mentioned
below, often grows interspersed amongst Alaria esculenta f. pinnata,
Laminaria saccharina and others, in somewhat exposed places; but
its real habitat is in the interior of the fjords, where the water is
calm. Here occur the typical, large, broad-fronded individuals: they
are often social in growth and then form pure or almost pure as-
‘sociations; but they are most frequently distributed in patches, and
then alternate with Saccorrhizeta or social growths of Laminaria
nigripes v. atrofulva. In such places occur also the broad-fronded
calm-water forms of Laminaria saccharina and L. digitata. Alaria

142 H. JONSSON

Pylati occurs thus as a calm-water form corresponding with the
deep-water form of Alaria esculenta and with the form found on
exposed coasts. I have found the Alaria Pylaii-association well de-
veloped in E. Iceland at a depth of 20 metres. The species also
extends higher up and may, like all the other Laminariacee, occur
at about the limit of low-tide or in the water-filled depressions in
the lower littoral zone, but is then, like those Laminariacee, of
small growth.

The Laminaria ferédensis-association. The species in
question grows socially at a depth of 20—30 metres in Fossarvik
at the head of Berufjéréur in E. Iceland. In its external appearance
this association exactly resembles the deep-water association of La-
minaria saccharina. The structure of the stipe differs however, be-
cause L. feerdensis has a hollow stipe like L. longicruris; as Rosen-
vinge (63, p. 211) and Bérgesen (12, p. 766) point out, the air-
filled hollow space probably serves to lift the large lamina from
the sea-bottom. |

In deeper water, L. ferdéensis occurs in the same manner in the
Ferédes as it does in E. Iceland (Bérgesen, loc. cit., p. 766), but
differs somewhat in shallow water. In Greenland and Iceland, as
in the Ferées, the hollow-stemmed Laminarie prefer protected
localities.

The Alaria esculenta-association. This is distributed
very commonly along all the coasts of Iceland. It prefers a rocky
substratum, but may occur also on pebbles as Laminaria saccharina
occurs, and frequently in company with it. As a rule, the associa-
tion is best developed at a depth of 6—16 metres; but the species
occurs, in addition, growing socially at a depth of 3—4 metres and
again, sometimes as deep as 30 metres. The association is pure or
only slightly mixed, and then usually with L. saccharina, L. digitata
or Al. Pylaii; it often stretches for miles in the fjords. The species
(Alaria esculenta) varies in a manner somewhat similar to the varia-
tions of Laminaria saccharina and L. digitata. In very exposed places,
there is found in shallow water a narrower-fronded form with nar-
row, leathery sporophylls. This form cannot be termed a surf-form
like L. digitata f. stenophylla but it may, however, merit the title of
an exposure-form. Another form, which is much larger, both as
regards the length and breadth of its fronds, occurs in deeper water

MARINE ALGAL VEGETATION 143

(f. pinnata). This alga is one of the largest found on the. coasts of
Iceland, and may at times attain a length of 6—8 metres. The form
of the frond resembles to some extent the shallow-water form of
Laminaria saccharina, the thick mid-rib of Alaria corresponding with
the thickened median area of Laminaria. The fronds of both species
are thus well adapted to withstand the motion of the waves; in
fact both species are rather frequently found intermingled in a broad
belt along the coasts. On many of the sunken skerries which are
such a danger in navigation, Alaria esculenta is the principal species,
indeed frequently growing alone. In Hvammsfjéréur in SW. Iceland,
in places where a strong current exists (Réstin) there was found a
dense vegetation of broad-fronded Alaria esculenta f. pinnata with
very long lamine.

It is general knowledge that the Jamina is torn in pieces by
the waves, and cases are frequent also in which the thin part of
the lamina is divided into many pieces by transverse slits, often
nothing remaining save the mid-rib itself, especially in the upper
part of the lamina. A luxuriant Alarietum was found below the
limit of low-tide at the extreme point between Seydisfjérdéur and
Lodmundarfjéréur; it consisted mainly of Alaria esculenta f. pinnata
with Alaria Pylaii and Lam. saccharina intermingled. It was at once
noticeable that the uppermost Alarie were entirely frondless; the
stipes were completely overgrown with Ectocarpacee. It must be
admitted that the situation was exposed, and therefore it may well
be that the laminz were destroyed by the beat of the waves; but
there is just as much reason to believe that this was occasioned
by the drift-ice, which had made its appearance on the coasts some
time before my arrival. In this locality the Fucus-belt had also
been scraped off the rocks in several places which, in my opinion,
was caused by the drift-ice.

The Laminaria saccharina-association. This associa-
tion is very luxuriant, and occurs almost pure over stretches ex-
tending for miles along the coasts. It does not always grow on a
firm, rocky substratum: rather frequently it occurs on a pebbly
substratum, in which case the plants are attached either to a
single pebble or to several, as if lying at anchor. With dredgings,
therefore, it rather frequently happens also that the plants
with their “anchors” are dragged up from the sea-bottom. This
association is met with from a depth of about 2 metres, or from

144 H. JONSSON

about the limit of low-tide, down to a depth of about 30 metres.
Small individuals may be found in the lowermost water-filled de-
pressions of the littoral zone. Compared with the other commonly
distributed Laminaria-species, L. digitata and L. hyperborea, then L.
saccharina generally keeps nearest to the coast, especially the more
leathery, shallow-water form. In shallow depths the succession can
be perceived distinctly, but with regard to greater depths conclu-
sions must be drawn from what is brought up by the dredge. The
succession usually is, that while L. saccharina keeps nearest to the
land L. hyperborea extends deepest.

As is well known the species varies very much, according to
the depth and the degree of exposure. A form with leathery, thick
fronds with a rough surface occurs near land on somewhat ex-
posed coasts in those depths where the effect of the beat of the
waves is distinctly observable. At greater depths another form oc-
curs, the deep-water form, with long, broad and comparatively thin
fronds; and in protected localities inside the fjords of E. and W.
Iceland a third form occurs at a depth of 4—20 metres. This form
(f. latifolia) is long-stemmed, with comparatively very broad lamina
and an entirely smooth surface. As each of these forms grows very
socially the character of the association varies in accordance with
the depth and the exposure.

The Laminaria digitata-association. This association is
very common everywhere along the coasts where there is a rocky
substratum, from a depth of about 4 to about 25 metres. On rocky
coasts, however, small specimens occur just at the limit of low-tide,
and there represent a kind of boundary. Small individuals may
occur also in water-filled depressions in the lowest part of the
littoral zone. |

The tendency of Laminaria digitata is to vary in the same
manner as L. saccharina, and thus the character of the association
differs according to the depth and the degree of exposure, as the
forms, individually, grow socially. The typical appearance of the
association is determined by the deep-water form, or the typical
form, which seems to grow most luxuriantly at a depth of about
10—20 metres. Here the species attains its greatest length and, as
a rule, the stipe is so strong that it is able to raise the much-
divided lamina from the bottom.

Just as the forms are connected with one another. by inter-

MARINE ALGAL VEGETATION 145

mediate forms, so are the various associations connected. If the
deep-water character of the association is taken as a starting point,
we notice that it changes gradually with decreasing depths on ex-
posed coasts, and that somewhere near the limit of low-tide it
assumes an entirely different characler, which is displayed in the
leathery, long-stemmed form with a narrow and slightly-divided
frond (f. stenophylla). On an exposed coast this variety might be
termed the shallow-water type or perhaps, rather, the surf-type, in
conformity with the surf-form of Fucus inflatus. The surf-character
was very beautifully and typically developed in the Vestmannaeyjar;
here f. stenophylla grew very socially, forming a continuous belt,
the upper boundary of which occurred almost at the limit of low-
tide. When during low-tide the waves receded it was very inter-
esting to see how easily the leathery, narrow, slightly-divided laminz
moved with the waves, and everywhere, as far as the waves receded,
the rocky substratum between the Sfenophylla-individuals was quite
reddish in colour from the encrusting Phymatolithon polymorphum.
The Laminaria plants were very firmly attached to the rock a
fact evidently well known to the fishermen, as they fastened the
boat to a Laminaria while we went ashore. The stipe is leathery
and pliable, and the plants cling closely to the substratum when
the waves recede.

I have found f. stenophyila in other places, although not in
such abundance, and not quite so typical. Here the same rule
applies as with regard to Fucus inflatus and Laminaria saccharina,
that the tendency to vary seems to depend on the greater or lesser
movement of the water; on coasts which are somewhat exposed, a
Laminaria digitata-association is rather frequently found at about
the limit of low-tide, with a character midway between the surf-
character and the deep-water character.

If we again take the deep-water character of the association as
a starting point, and move inwards towards the protected coasts,
we see that the character changes again, but in another direction.
The stipe becomes shorter and the frond much broader and slit
into fewer and broader lobes. Within the fjords, in W. and E. Ice-
land especially, the character is entirely different from the deep-
water character. Here occur forms with very broad fronds which
are either undivided or divided into two, or a few, very broad
lobes (f. cucullata). Generally the depth is about 4—20 metres, even
deeper occasionally. I have found associations with this character

The Botany of Iceland. I. 10

146 H. JONSSON

well developed in E. Iceland. At an insignificant depth, where I was
able to see the sea-bottom, the individuals were not really closely
placed, but lay on the bottom, some quite flat, and others slightly
obliquely with the hollow surface turned upwards to the light. In
this way the sea-bottom was almost entirely covered by the broad
fronds.

This character might be termed the calm-water character, and
an association-character exactly corresponding with it is found in
Laminaria saccharina and Fucus inflatus.

Laminaria digitata f. cucullata occurs also scattered among La-
minaria nigripes v. atrofulva and Alaria Pylait.

The Laminaria hyperborea-association. It is developed
luxuriantly in S. and SW. Iceland, and occurs also in E. Iceland
and N. Iceland, in those places which I have visited. I can pro-
nounce no opinion upon its general distribution in N. Iceland, as
dredgings have been undertaken there in a few places only; yet I
think that it occurs everywhere there. In E. Iceland, on the other
hand, where I have done a great deal of dredging, I have only
found it at the mouth of Berufjérdur. It is very luxuriant in the
Vestmannaeyjar, forming a continuous belt round the inhabited
island.

The association grows on a rocky substratum, from a depth
of about 4 metres to about 30 (or 40) metres, and occurs both on
-exposed and on slightly exposed coasts; close to the limit of low-
tide and in water-filled depressions in the lowermost part of the
littoral zone small specimens may occur. In shallow water, with
exceptional low-tides, the upper part of the stipe is frequently seen
rising above the surface, raising the lower part of the frond obliquely
above the water. Bérgesen (12, p. 755, Fig. 160) has reported and
illustrated this from the FeerGes.

In Iceland L. hyperborea does not vary in the same manner
as do L. saccharina and L. digitata, the fact being that it does not
occur in protected places, and on exposed coasts does not extend
so far up as the two species mentioned. Those specimens which
occur close to the limit of low-tide, or in pools in the littoral zone,
are quite as typical as the large, deep-water individuals. The asso-
ciation seems to thrive best at a depth of about 20 to 30 metres,
but on somewhat exposed coasts it also thrives fairly well at lesser
depths, and is then very frequently mixed with the other members
of the community; while at greater depths it is generally pure. As

MARINE ALGAL VEGETATION 147

is generally known, the species has very strong haptera, often ar-
ranged in rows, which issue from the lower part of the stipe, so
that the haptera appear one above the other in vertical succession.
They then look like a vertical row of obliquely placed props, one
above the other; such rows issue in all directions from the stipe.
By this it must be understood that, as the plant grows, new hap-
_ tera appear, usually in the regular succession mentioned, until such
time as the plant attains its normal size. The development of the
haptera must necessarily keep pace with the rest of the growth,
because the larger the plant becomes so much the more is it moved
by the waves, and so much the stronger must the props become
if, the plant is not to be torn up. The youngest props are the
longest, and are situated at the extreme (upper) end of the row.
That the growth of the organs of attachment is contemporaneous
with the increase in size of the individual applies also, of course,
to the other Laminariacee, but scarcely anywhere is it seen so
distinctly as in this species. |

In its main features L. hyperborea behaves in Iceland — at any
rate in S. and SW. Iceland — in the same manner as it is recorded
by Borgesen (12, p. 755) to behave in the Ferées.

The Under-vegetation. No doubt an abundant under-vege-
tation occurs everywhere, chiefly formed of crustaceous alge as a
lower layer, and of branching or membranaceous Rhodophycee and a
few Phceeophycee in addition as an upper layer. Here, as in the Fucus-
belt, it must be assumed that the under-vegetation is of no real
value to the upper; while, on the other hand, the latter affords
protection to the under-vegetation — in the Fucus-belt against de-
siccation and too strong light, and in the Laminariacee-community
against strong movements of the water. The subdued light caused
by the Laminaria fronds is, no doubt, also of importance in the
upper portion of the Laminaria-belt, in so far, at any rate, that
the species with a more downward range may endeavour to attain
greater heights. In the lower portion of the Laminaria-belt the sub-
dued light does not seem to affect the under-vegetation very much
which seems to thrive there just as’ well as in open places where
Laminariacee are absent; to have the waves moderated may be
beneficial to the under-vegetation, especially in shallow water. During
excessive ebb-tides opportunities may occur in many places of seeing
how the Laminaria fronds moderate the motion of the waves, that
is when this is not too violent, as, for example, when it approxi-

10*

148 . H. JONSSON

mates to surf. In deep water the Laminaria fronds will always
moderate the motion.

In shallow water, especially where the bottom can be seen, it
is easy to observe the under-vegetation, but in deep water one has |
to rely upon the specimens brought up by the dredge.

The under-vegetation is not divided according to the various
associations of the upper vegetation, but seems to possess the same
character wherever it is observed. In S. Iceland (the Vestmannaeyjar
and Eyrarbakki) Phymatolithon polymorphum occurs in great abun-
dance, covering the bottom entirely for large distances near the
coast as an undergrowth. It is mainly composed of crustaceous,
membranaceous, and more or less branching Floridee. .

A. Crustaceous Algez. In several places in N. and E. Iceland
I found a luxuriant under-vegetation formed of Lithothamnion leve,
L. circumscriptum and L. glaciale. Among these species the first men-
tioned especially seemed to be widely distributed both on the bottom
ofan Alaria and a Laminaria association. In E. Iceland Lithothamnion
flavescens and L. foecundum in addition, like Clathromorphum compac-
tum, were very frequent on a Laminaria-association-bottom. Together
with these species occurred Peyssonellia Rosenvingii, Cruoria arctica,
Lithoderma and others, as in the crustaceous algal vegetation (see p. 155).

B. Membranaceous and Branching filamentous spe-
cies. The upper layer, with which are also associated inter-
mingled species, varies considerably according to the depth. In
addition to a number of the species which extend further down-
wards, various semi-littoral species may thus occur in the upper
part of the Laminaria-belt. A number of the species which grow
on the Laminaria stems may also occur on the bottom between
the Laminarie.

Here it is really a question of several associations; the lowest
layer, as mentioned, is the crustaceous alga-association; the second
layer is composed in its upper part of semi-littoral associations,
which meet the associations which extend deeper and are mainly
associations of Rhodophycee; and the uppermost layer is the Lami |
naria-association. The species are named where these associations
are mentioned, and are therefore omitted here.

The Epiphyte-vegetation. Epiphytes very frequently occur
on the stipes and laminz of the Laminariacee, and it is a parti-
cularly common occurrence for old stems of Laminaria hyperborea
to be entirely overgrown, for the epiphytic vegetation is much more

MARINE ALGAL VEGETATION 149

luxuriant on this species than on the remaining Laminariacee. It
happens rather frequently, however, that a rich epiphytic vegetation
occurs on L. digitata, L.saccharina, Alaria esculenta and Saccorrhiza
dermatodea. The epiphytes generally occur most abundantly on the
older individuals. The vegetation on the stems is usually composed
of species which may be found growing among the Laminarie,
and then belong to the second layer of the under-vegetation, which
can thus be raised upon the Laminaria stems; consequently, it is
very natural that the composition of the species of the epiphytic
vegetation should vary according to the depth. The following
distinction is evident: that the semi-littoral species which grow
epiphytically in shallow water vanish as the depth increases; while,
on the other hand, some of the deep-water species may occur at a
relatively lesser depth.

The following species have been found to occur on stems of
Laminariacee, and may almost all be found on Laminaria hyper-
borea: —

Ahnfeltia plicata. | Rhododermis parasitica.
Antithamnion floccosum. Rhodophyllis dichotoma.
A. Plumula v. boreale. Rhodymenia palmata.
Ceramium rubrum. Desmarestia aculeata.
Delesseria alata. D viridis.

D. sanguinea. Ectocarpus confervoides.
D. sinuosa. E. fasciculatus.
Dermatolithon macrocarpum. E. Hinksie.

Euthora cristata. E. penicilliformis.
Gigartina mamillosa. E. siliculosus.
Lithophyllum Crouani. E. tomentosoides.
Lithothamnion circumscriptum. Isthmoplea spherophora.
Lomentaria clavellosa. Laminaria digitata.

L. rosea. L. hyperborea.
Odonthalia dentata. Leptonema fasciculatum.
Petrocelis Hennedyi. Litosiphon filiformis.
Peyssonellia Rosenvingii. Sphacelaria olivacea.
Plocamium coccineum. S. radicans.
Polysiphonia arctica. Monostroma fuscum.

P. parasitica. M. Grevillei.

P. urceolata. M. undulatum.

Porphyra miniata. Ulothrix flacca.

Ptilota pectinata. Ulva Lactuca.

P. plumosa. Ulvella fucicola.
Rhodochorton repens. Urospora Wormskioldii.
R. Rothii. 51 species in all.

In addition, the fungus Dothidella Laminarie must be men-
tioned; it is a very common endophyte in the stipe of various

150 H. JONSSON

Laminariacee. It occurs most commonly at depths of from 6—20
metres, but has also been found as deep as 30 metres.

Many of these species grow very socially and often cover the
stipes completely, or nearly so. At Reykjavik, it is very usual in
the spring to find Laminaria hyperborea in shallow water (4—10
metres) with the stipes entirely overgrown by Rhodochorton Rothii,
Antithamnion floccosum and Polysiphonia urceolata, each on its own
particular stipe, or else intermingled. Petrocelis and Rhododermis
occur also in great abundance, almost covering entire stipes. In the
Vestmannaeyjar and at Eyrarbakki it was also a fairly common
occurrence to find stipes of Laminaria hyperborea completely over-
grown by Dermatolithon macrocarpum. In the northern part of the
country Lithophyllum Crouani also sometimes covers the stipe of
L. hyperborea over its entire length. Many of the remaining species
may also occur abundantly, but most frequently the vegetation upon
the stipes is mixed, and crustaceous species grow side by side with
branching and membranaceous species.

The epiphytic vegetation seems to be most luxuriant and richest
in species at lesser depths, where the semi-littoral associations
meet the associations which extend deeper down, and where, in
addition to the Rhodophyceew which always predominate, both brown
and green species occur. At a greater depth the species are few,
and are almost exclusively Rhodophycee. Generally, the rule seems
to hold good that while the species with a more downward range
occur on the haptera or on the lower part of the stipe, the more
light-loving species occur on the upper part of the stipe; the green
algee, however, are by no means always uppermost. Thus in the
upper portion of the Laminaria-belt Euthora, Rhodophyllis, Odon-
thalia and others frequently occur among the haptera, but in the
lower portion of the belt they may be found on the stipe almost
everywhere, especially Euthora. This agrees with Berthold’s ob-
servation of the succession of epiphytes on Cystosira in the Medi-
terranean, and with Bo6rgesen’s observation of the order of the
epiphytes on Laminaria hyperborea in the Feerdoes.

The vegetation on the stipe of L. hyperborea is extremely
luxuriant in S. and SW. Iceland and is considerable both in NW.
and N. Iceland, but is poor in E. Iceland. :

Epiphytes frequently occur also on the fronds of the Lamzi-
nariacee, especially in the upper portion of the Laminaria-belt.
Here the brown algz predominate, while only a few red and green

MARINE ALGAL VEGETATION 151

alge occur. The following species are common or, at least, occur
very socially: —

Chantransia Alarie. Myrionema Corunne.

Rhodochorton membranaceum. Pheeostroma pustulosum.
R. penicilliformis. Pylaiella litoralis.
Ascocyclus islandicus. Streblonema Stilophore.
Ectocarpus tomentosoides. Acrosiphonia incurya.
Litosiphon filiformis. Ulothrix flacca.

All the remaining Eciocarpus-species which are found on the
stipes occur in addition. Of the species mentioned there are three
in particular which grow very socially: Chantransia Alariw covers
the entire frond of Alaria esculenta from tip to base; Ectocarpus
tomentosoides also grows very socially on the fronds of Laminaria
hyperborea and L. digitata which it frequently, entirely or nearly,
covers during spring-time, at which time, also, Litosiphon filiformis
often covers large portions of the lamina of L. saccharina.

Myrionema Laminarie and Streblonema eecidioides, in addition,
grow as endophytes in the Laminaria fronds.

Thus, at least 62 species of marine alge, or about 59 °/o of the
algal species (113) which grow below the limit of low-tide, occur
on or in Laminariacee.

On other coasts, those of the Ferdes, for example (Bérgesen,
11 and 12), and those of Norway (Boye, 10) a similar epiphytic
vegetation occurs in the Laminaria-association. On the coasts of
Greenland (Rosenvinge, 63) the epiphytic vegetation is much
scarcer in the Laminaria-belt, which is possibly due, in part, to
the absence of Laminaria hyperborea from that country.

15. The Desmarestia-association.

Desmarestia aculeata is very common and grows both scattered
and socially; vertically it is widely distributed, as it has been found
at depths of trom 4—60 metres (in E. Iceland). It seems to grow
most luxuriantly at a depth of about 6—30 metres, and then is
frequently found in associations of lesser extent. Only rarely is
this association found dominant on the bottom, and even then only
in small patches. Most frequently it occurs intermingled with other
associations; thus, when dredging on a Laminaria bottom, it
very frequently happens that Desmarestia aculeata is brought up,
and as frequently as not it is intermingled with the associations
which extend deeper down. It often grows among the Laminarie,

152 H. JONSSON

where there are openings in the Laminaria-vegetation, and beyond
the Laminaria-belt it is very frequently found on a sandy or pebbly
substratum, at any rate at inconsiderable depths. In the Laminaria-
belt proper it plays the role of a kind of ‘underwood,’ but beyond
the belt, at greater depths, it protrudes far above the associations
of red alge.

Desmarestia viridis occurs in a similar manner, very often with —
the other species, both inside and outside the Laminaria-belt. It is
of less importance, however, as it is much less common. At depths
of between 20-—-30 metres it may also occur dominantly in patches.

In E. Iceland, at a depth of 20—30 metres, Chorda tomentosa
occurs growing very socially with the Desmarestia species.

Of the epiphytes on Desmarestia aculeata the small Porphyropsis
coccinea is of most importance (in S. and SW. Iceland).

In several respects this association recalls the semi-littoral
Chorda-association.

Similar Desmarestia- vegetation occurs in the Ferées (Boérge-
sen, 14), in Greenland (Rosenvinge, 63) and in northern Norway
(Foslie, 18, p. 100). |

16. The Deep-water Community of Floridez.

A mixed society, which consists mainly of a few species of red
algee, generally occurs at a depth of about 15—40 metres (over 50
metres in E. Iceland). To judge from the dredgings, the plants some-
times seem to grow socially — at any rate over small areas — and
sometimes to grow scattered, then, as a rule, much intermingled
with one another.

The species which seem to have an abundant local distribution
in fairly many places are the following: Delesseria sinuosa at depths
of from 14 to nearly 40 metres and somewhat deeper in E. Iceland;
Ptilota plumosa from 16 metres to about 40 metres; Odonthalia
dentata from 15—30 metres, and Polysiphonia arctica from 16—40
metres (10 to about 60 metres in E. Iceland). Thus each of these
species forms associations, but these are often of inferior extent,
with the exception, however, of that formed by the last mentioned
species.

The Polysiphonia arctica-association. Polysiphonia arc-
tica is of extremely social growth in E. Iceland, in Seydisfj6réur
and in Reydarfjérdur. It grows most luxuriantly at depths of from
16—40 metres and forms an enormous, continuous belt along large

MARINE ALGAL VEGETATION 153

stretches of the coast. It is the only species of this community
which forms a large, continuous and almost pure association, at
any rate over considerable areas. The upper part of the association
is, however, generally mixed with Delesseria sinuosa, Ptilota, Odon-
thalia, Rhodophyllis and others, and then these species often occur
in such abundance that the community acquires its usual mixed
character; that is, several species occur dominantly side by side,
though no single species can be said to predominate.

Among the remaining species of the community Rhodophyllis
dichotoma is often rather social. It is very common for Euthora
cristata to occur intermingled, but to judge from the dredgings it
seems to have a scattered growth. Ptilota pectinata may be of fairly
social growth in E. Iceland. Delesseria sanguinea and Polysiphonia
urceolata occur also in this community, the first mentioned ap-
pearing to be most frequent while, in a few places, the latter has
been found in abundance. :

Of the species with a scattered growth which belong to this
community may be mentioned: Lomentaria clavellosa (20—40 metres),
L. rosea (20—40) and Plocamium coccineum (20 metres), all in the
Vestmannaeyjar; and also Turnerella Pennyit and Omphalophyllum
ulvaceum in E. Iceland.

In many places the under-vegetation of the community is formed
of crustaceous species of Lithothamnion.

Of the intermixed species, Desmarestia aculeata and D. viridis
are very frequent. In E. Iceland Chorda tomentosa has been found
intermingled in this community. In addition, Laminariacee of scat-
tered growth such as Laminaria hyperborea, L. digitata, L. saccharina,
Alaria esculenta, f. pinnata and Alaria Pylati occur very frequently ;
they are the outposts of the Laminariacee-community.

It has been previously mentioned that many of the members
of this community grow on Laminaria stems, and that in several
places the community forms, together with species of Desmarestia,
the second layer of the under-vegetation of the community of
Laminariacee.

The community grows both on somewhat exposed and also on
exposed coasts, and occurs both on a rocky and on a pebbly sub-
stratum, and even on sand.

The semi-littoral Polysiphonia urceolata-association has much in
common with this community.

Rosenvinge (63) and, following him, Bérgesen (12) call this

154 H. JONSSON

community or quite similar communities: the sublittoral Floridee-
formation.

17. The Lithothamnion-association.

In this association I include only the highly branched species,
Lithothamnion Ungeri and L. tophiforme, as these differ from the —
other calcareous algal vegetations by their characteristic and very
social growth. Within the fjords, at a depth of about 12—25 metres,
these algze occur in such abundance that there might be good
reasons for calling it a submarine reef of calcareous alge. Within
Arnarfjérdur in the vicinity of Bildudalur there was, for instance,
such a luxuriant vegetation of L. Ungeri that the dredging-bag was
filled time after time, nothing being found in it save this species.
Mr. B. Semundsson has also found a similar Lithothamnion
vegetation in several of the small fjords at Isafjaréardjup; and as,
moreover, there are specimens to hand from several other fjords
in NW. Iceland, this association seems to be luxuriantly and com-
monly distributed in this part of the country. A similar vegetation,
mainly composed of L. tophiforme, occurred also in abundance in
Eyjafjérdur in N. Iceland. I have also noticed a. similar vegetation
— though not so luxuriant — in several of the fjords of E. Iceland.
Horring collected L. tophiforme in Hvalfjéréur in SW. Iceland, and
Szemundsson also found it there, apparently growing very socially.

In this association very few epiphytes occur, though Turnerella
Pennyi ought to be mentioned in N. and E. Iceland; on the other
hand animals generally occur in abundance, especially Ophiurida
and snails and other smaller molluscs which project everywhere
from between the Lithothamnion-branches.

When dredging on such a bottom rather large pieces are hauled
up, which cohere, usually, by reason of the numerous branches
being matted together. Rather large globular masses, which are
sometimes hollow, but which are often filled with comparatively
thick interwoven branches, are also frequently obtained. The hollow ~
masses must be supposed to have grown on the outer side of some
substratum which has disappeared. This Agagropila-form is gene-
rally known. Rosenvinge mentions it from Greenland, and assumes
that it lies loose upon the bottom; the masses must then be illu-
minated all round by being rolled about as, for instance, by the
action of the undercurrent. From what I have seen, it seems to
me that a point of attachment can be perceived on entirely fresh

MARINE ALGAL VEGETATION PDS

forms of 4gagropila, and in my opinion they are outgrowths upon
old “blocks” of calcareous alge. The action of the current probably
loosens them, and they then roll about on the bottom. Undoubtedly
they can live fairly long in that condition, but if they roll about
much, they will surely by degrees go to pieces.
: This association recalls the semi-littoral Corallina-community,
particularly the Corallina-association.

The Lithothamnion-association occurs in Greenland (Rosen-
_vinge, 63) but not at the Ferées (Bérgesen, 12).

18. The Community of Crustaceous Alge.

The characteristic life-form of the crustaceous alge which is
so essentially different from that of the rest of the marine algz
seems to justify the idea that they all belong to one community.
With all of them the thallus is flat and, like the crustaceous lichens
on the rocks, adheres by the whole of its lower surface to the sub-
stratum. As the form and the manner of development of the thallus
in the different species are identical in their main features, I think
that the community may appropriately be named after the crusta-
ceous growth.

The substratum of the community consists of rocks, pebbles,
mussel-shells and the like; also of other alge, especially species of
Laminaria.

The community has a very large distribution both in a hori-
zontal and in a vertical direction, and possibly it is more particu-
larly members of this community which we may expect to find in
the vicinity of the absolute depth-limit of growth of algal vegeta-
tion. The community has already been mentioned as the under-
vegetation in the Laminariacee-community; it occurs also as an
undergrowth in communities which extend to a greater depth and
thus, partly as a dominant growth on the bottom and partly as
undergrowth, it reaches from the great depths right up to the limit
of low-tide. The semi-littoral and the littoral crustaceous alga-asso-
ciations should also be regarded as part of this community although,
for practical reasons, they have been dealt with earlier in this paper.
The community is pure, that is to say it is composed of only cru-
staceous alge; there occur, it is true, various intermingled species, of
which the majority are Floridee, though some are Pheophycee, but these
I consider unessential and almost irrelevant to the crustaceous alga-
community proper. They have their homes in other communities,

156 H. JONSSON

and sometimes, perhaps, are in the act of forming an upper vege-
tation; sometimes they may be individuals which have “strayed”
beyond the real limits of their community.

The community is divided into various associations, according
as to whether the one or the other of the species is dominant over
considerable areas. A widely distributed and typical Phymato-
lithon-polymorphum-association occurs, thus, in S. Iceland, and
Lithothamnion Lenormandi has a fairly social growth at Reykjavik.
L. leve and Clathromorphum compactum also form associations in
several places. Judging from the dredgings, Lithothamnion flavescens
and L. foecundum have a more scattered growth while, on the other
hand, L. glaciale often occurs abundantly. Otherwise, it is very
common for the Lithothamnion species to grow intermingled with,
and at times upon, one another. The crustaceous, calcareous algz
form the greater part of this community in Iceland. The remaining
crustaceous species, such as Peyssonellia, Cruoria arctica and Litho-
derma fatiscens, are found more scattered, although the last-named
species forms associations in shallow water right up to the limit
of low-tide. These species must, however, be much more common
on the sea-bottom than is shown by the dredgings. It may be taken
for granted, also, that Petrocelis Hennedyi and Rhododermis parasitica
occur on a stony substratum in deeper water, seeing that they are
so common on the stems of Laminaria hyperborea at considerable
depths. Both Hildenbrandia and Petrocelis occur on a stony sub-
stratum at shallower depths, and also Ralfsia ovata.

The species which has, with absolute certainty, been found
growing deepest is Lithothamnion leve (see Part V), and it occurs
in masses at a depth of 88 metres, that is, it forms a Lithotham-
nionetum at this depth. Thus, of all the marine algal communities
in Iceland, this community extends deepest.

A similar vegetation occurs in Greenland (Rosenvinge, 63,
p. 223), and in other places in the Arctic Sea (Kjellman, 36), but
in both these places it differs in the wider distribution and greater
luxuriancy of the Lithoderma fatiscens-association. In the Feer6ées
(Borgesen, 12) the conditions seem to be somewhat similar, simi-
lar in any case to the conditions in S. and SW. Iceland, although
Lithoderma fatiscens seems to occur there more sparsely than in
Iceland.

Or
~l

MARINE ALGAL VEGETATION 1

B. The Sea-grass Vegetation.
The Zostera-association.

This association differs so much from the other marine com-
munities in Iceland — the marine algal communities — that it
must be regarded as not being in any way connected with them.
The present community occurs especially on a substratum of muddy
clay, which the algze avoid. The “roots” of the algee — the haptera —
are organs of attachment only, their sole function being, in most
cases, to attach the plant to the substratum — the stony substra-
tum —, while Zostera has true roots which obtain nourishment from
the substratum. For this reason Zosfera requires a good nutrient
substratum which is generally soft. It is rare, indeed it must be
reckoned exceptional, for Zostera to be found growing on a hard
clay-substratum. I understand such cases to indicate that formerly
the substratum had been softer and then became more compact
owing to the deposition of clay and sand, and that the Zostera is
consequently about to disappear from such a spot. In places where
there is no danger of either sand or clav being deposited from
brooks or rivers the substratum will, nevertheless, scarcely remain
unchanged, as the mud and ooze which are thrown down every-
where in the ocean, when once they have been brought to a place,
readily accumulate and remain, in the shelter of the dense vegetation.

The Zostera-vegetation occurs widely distributed, especially in
SW. Iceland where, in many places, both inside the smaller arms
of the fjords and in the large fjords such as Breidifjérdur, a sub-
stratum of muddy clay occurs between the coast and the skerries
which lie nearest. At Breidifjérdur, during low-tide, the pale-green
Zostera-belt may be observed stretching for miles along the coast.
At Faxaflé6i also the Zostera-vegetation has an extensive distributicn.
Zostera is found, most certainly, on other parts of the coast of Ice-
land, but nowhere have I seen such extensive “meadows” of it as
in SW. Iceland.

The vegetation is generally pure and there is hardly an asso-
- ciation of species in the sea off these coasts which is less mixed
than the Zostera-association. In other places Zostera is a fa-
vourite substratum for epiphytes, but however much I searched I
did not find anything worth mentioning on the Zostera plants here;
in this respect the Zostera-meadow of Iceland agrees with that of
the Feerées. At times, species belonging to the semi-littoral commu-

158 H. JONSSON

nities occur intermingled in the Zosfera-belt; these then grow in
small depressions, where the subsoil, usually a solid, clayey and
pebbly substratum, appears. Such species are: Chorda Filum, Chor-
daria flagelliformis, Castagnea virescens, Dictyosiphon foeniculaceus,
Pylaiella littoralis, Ceramium rubrum, Cystoclonium purpurascens and
others. They should not be classed in the Zostera-association, and
are mentioned only to explain the appearance of the Zostera-meadow.

The Zostera-association is sublittoral, but hardly extends as far
down as do the semi-littoral communities. It cannot endure pro-
tracted exposure, and thus a substratum which would adapt itself
well to Zostera may be found completely devoid of plants in places
which are exposed for a long time during low-tide. From time to
time, during extreme ebb-tides, the upper part of the Zostera-meadow
may, however, be seen quite dry. But here two points have to be
taken into consideration: the first being that the period of exposure
is extremely short, and the second being that the extreme ebb-tides
occur so seldom that they ought not to be taken into calculation.
As a rule, the Zostera substratum is always submerged during low-
tide. The water is so low, however, that the leaves float on the
surface of the water, giving it a greenish tinge. When wading in
a Zostera-meadow during low-tide the water reaches to about the
knees.

In SW. Iceland the time of fruiting is during August—October.

On Zostera-soil there is in most places a very rich animal-life,
but whether this has any influence upon the vegetation or on the
nutrient substratum needs further investigation.

In connection with the Zostera-association [ will just mention
the Brackish-water-vegetation. It is so little known that there
is nothing to be said about it, except that I have found Ruppia
maritima in one solitary spot, where it grew so luxuriantly that,
although scattered, it characterized the bottom.

Vil. DIFFERENCES IN THE VEGETATION IN EAST
AND SOUTH ICELAND.

| hem Iceland and South Iceland — at the south-eastern corner of the
island, at about the stretch of coast from Vestrahorn to Eystra-
horn — are divided by a rather sharp boundary both as regards the
hydrography and the composition of the vegetation, as has been
mentioned above. On the other hand, E. Iceland is connected with
S. Iceland by a large transitional area (see p. 67) which stretches
further along the north and north-west coasts and a part of SW.
Iceland. The difference as regards the vegetation is therefore greatest
between E. Iceland and S. Iceland; so it is these coastal districts
which will exclusively or almost exclusively be treated of in this
part of the present paper.

Where a great floristic difference exists between the different
parts of the coast as, for instance, between E. Iceland and S. Ice-
land! (see Part III) it is to be expected that there will be differences
in the vegetation, more especially as some of the species which are
not common to all the coastal districts grow socially and form
associations. The majority of the communities and the associations
are however common to all the districts and are somewhat similar
in appearance, as is also seen from the above description (Part VI),
where the differences are always mentioned.

As regards the communities and associations common to both
districts it is enough to refer to the above description. Here, only
those communities and associations will be mentioned which are
found in the one district but are absent from the other.

1 The greater part of the coast of S. Iceland is a sandy coast or a barren
“desert;” in this part of the present paper, by S. Iceland is meant only that part
of the coast where vegetation occurs — the Vestmannaeyjar and the stretch of
coast from Reykjanes in the direction of Thjorsa or somewhat more to the east
than Stokkseyri.

160 H. JONSSON

Occurring in E. Iceland | Occurring in S. Iceland
and absent from S. Iceland. and absent from E. Iceland.
Arctic Associations. Boreal Communities and Asso-
The Monostroma groenlandicum- ciations. |
association. The Pelvetia-Fucus-spiralis-belt.
The Polysiphonia arctica-associa- | The Community of Corallina.
tion. The Fucus serratus-association.
Subarctic Association. The Phymatolithon-polymorphum-
The Laminaria feerdéensis-associa- association.
tion.

Further it should be pointed out that the epiphytic vegetation
on Laminaria hyperborea is quite infinitesimal in E. Iceland, but
very luxuriant in S. Iceland.

Of E. Iceland species which are important to the vegetation,
Laminaria nigripes, Turnerella Pennyi and others are absent from
S. Iceland. Of S. Iceland species which play a prominent part in
the vegetation a great many are wanting in E. Iceland (see Part III).

The Zostera-association requires to be described separately.
It belongs properly to SW. Iceland. Zostera is also known to occur
in E. Iceland and it is possible that it forms associations there, but
they are probably far more limited in extent than those in SW.
Iceland. Zostera has not been found in S. Iceland itself, which is
probably due to the fact that a favourable substratum for it is
wanting there.

If we now leave the Zostera-association out of consideration, as
the latter does not occur in S. Iceland, and confine our attention
to the above-mentioned communities and associations which are
found in the one district but are absent from the other, then it is
seen that at any rate some of them characterize the vegetation to a
considerable extent.

The Monostroma groenlandicum-association, as already
mentioned, is peculiar to E. Iceland and has a considerable exten-
sion in several places there. It is not found in S. Iceland. Mono-
stroma groenlandicum occurs sparingly both in N. Iceland and NW.
Iceland, therefore it is possible that this association is not exclu-
sively confined to E. Iceland. As the community of filiform alge is
commonly distributed both in E. and S. Iceland and green filiform
algee occur very luxuriantly in S. Iceland, the absence of M. groen-
landicum from the latter place is of no essential importance to the
vegetation as regards appearance.

MARINE ALGAL VEGETATION 161

The Polysiphonia arctica-association is of importance
as regards the appearance of the sublittoral vegetation in E. Iceland.
This association does not occur in S. Iceland, but a corresponding
one occurs, which is however far less luxuriant, composed of Poly-
siphonia urceolata.

The Laminaria feréensis-association is known to occur
only in E. Iceland. This association is probably more widely dis-
tributed along Iceland than is at present known; the species occurs
at any rate in N. Iceland. But I think that this species will hardly
be found along the coast of S. Iceland owing to the fact that shel-
tered localities are wanting there.

The Pelvetia-Fucus-spiralis-belt is most commonly dis-
tributed in S. and SW. Iceland, and composes there the upper part
of the Fucacee-community. As this belt is absent from E. Iceland
there is a considerable difference in the appearance of the upper-
most part of the Fucacee-community in the coastal districts in
question. Fucus spiralis is, however, found in E. Iceland.

The Community of Corallina is also peculiar to S. and
SW. Iceland and absent from E. Iceland. This community, or the
Corallina-Gigartina belt, is very luxuriant and often of considerable
extent in S. Iceland (and SW. Iceland), owing to which the semi-
littoral vegetation in E. Iceland and in S. Iceland differs highly in
character.

The Fucus serratus-association is poorly represented in
S. Iceland, but it is luxuriant in a single locality in SW. Iceland.
As Fucus serratus is rare, and somewhat resembles in appearance
the large, broad-leaved forms of Fucus inflatus which are common
everywhere, it plays only an inconsiderable part as regards the
appearance of the Fucacee-community.

The Phymatolithon polymorphum-association is pe-
culiar to S. Iceland, but as other crustaceous, calcareous alge occur
in E. Iceland in a similar manner though less luxuriantly, the ab-
sence of Phymatolithon polymorphum is of no essential importance
as regards the appearance of the crustaceous-alga- vegetation.

From what has been stated above it is evident that the occur-
rence of the Pelvetia-Fucus-spiralis-belt and the Corallina-Gigartina-
belt in S. Iceland (and SW. Iceland) gives to the littoral and semi-
littoral vegetation of the southern district a character different from
that of E. Iceland.

The Botany of Iceland. I. 11

162 H. JONSSON

If we now turn to the individual species which (besides those
already ‘mentioned) are found in the one coastal district but are
absent from the other, and which are important as regards the
appearance of the vegetation, we see, as already mentioned, that
such species are few in E. Iceland and numerous in S. Iceland.
Some of these species have a fairly social growth without, however,
forming independent associations. In the following, only those
species are given which occur most abundantly.

East Iceland. | South Iceland.
Lithothamnion flavescens. Lomentaria clavellosa.
L. foecundum. Plocamium coccineum.
Laminaria nigripes. Chantransia Alarie.
Turnerella Pennyi. | Callithamnion Arbuscula.
Ptilota pectinata. | Plumaria elegans.
Peyssonellia Rosenvingil. | Ceramium acanthonotum.
Coilodesme bulligera. C. rubrum.
Ulothrix consociata var. islandica. Polysiphonia fastigiata.

Rhododermis parasitica.
Cystoclonium purpurascens.
Ptilota plumosa.

Petrocelis Hennedyi.
Ectocarpus fasciculatus.

| E. tomentosus.

Cladophora rupestris.
Enteromorpha Linza.

It should moreover be noted that all the Ceramium-species are
absent from E. Iceland. In S. Iceland, besides those mentioned
above, Ceramium atlanticum occurs, and it will no doubt be possible
to find several more Ceramium-species in S. Iceland.

The Epiphytic Vegetation on Laminaria hyperborea, as
mentioned several times, is very luxuriant in S. and SW. Iceland:
in NW. and N. Iceland it must also be said to be fairly luxuriant,
but in E. Iceland it is quite infinitesimal in amount, which is pro-
bably connected with the fact that Laminaria hyperborea is rare in
E. Iceland.

The epiphytic vegetation on the stipes of Laminaria hyperborea
is very luxuriant and finely developed in S. Iceland. The following
from the Vestmannaeyjar are given as an example: — dominantly
on the stipe of L. hyperborea occurred Rhodymenia palmata, Delesseria
alata and Plocamium coccineum; less abundantly than the three
above-mentioned species occurred Delesseria sanguinea, Lomentaria
clavellosa, Lomentaria rosea, Euthora cristata, Gigartina mamillosa,
Ahnfeltia plicata, Petrocelis Hennedyi, Dermatolithon macrocarpum and

MARINE ALGAL VEGETATION 163

Pterosiphonia parasitica. To show how rich in species the epiphytic
vegetation occurring on a single individual of L. hyperborea may
be, the following species, also from the Vestmannaeyjar, may serve:
Desmarestia viridis, Ptilota plumosa, Delesseria sinuosa, Delesseria alata,
Lomentaria clavellosa, Polysiphonia urceolata, Plocamium coccineum,
Delesseria sanguinea and EFuthora cristata.

So luxuriant and finely developed an epiphytic vegetation gives
to the Laminariacee-community of S. Iceland a character different
from that which it has in E. Iceland.

On the stipes of Alaria and Laminaria digitata, on the other
hand, a similar epiphytic vegetation occurs in both the coastal
districts.

The zonal division of the marine algal vegetation is in its
main features similar in E. Iceland and S. Iceland, as is shown by
the following examples which have been taken straight from the
diaries.

East Iceland.

Vattarnes, steep clifts, | VIII. HalosaccionetumH.ramentacei.
highly exposed. 1/7. Urospora Wormskioldii.
I. Ulothricetum U. flaccae. Polysiphonia urceolata.
IJ. Bangietum B. fuscopurpurae. Rhodomela lycopodioides.
III. Porphyretum P.umbilicalis. | Chorda tomentosa.
IV. Fucetum F. inflati, in the most | IX. Alarietum.
exposed localities, consisting
only of f. exposita. | Holmanes, somewhat exposed,
V. Rhodymenietum. sloping rocky coast. 1°/7.
Halosaccionetum. | I. Ulothricetum U. flaccae.
Acrosiphonietum. II. Enteromorphetum E. intesti-
VI. Sublit. Alarietum. nalis.
III. Fucetum, uppermost, narrow
Borgarnes, sloping rocky coast, | margin of F. vesiculosus, be-
considerably exposed. }°/c. low that, broad belt of F. in-
I. Prasioletum P. stipitatae. | flatus, intermixed here and
II. Ulothricetum U. flaccae, in great there sparsely with Ascophyl-
abundance. lum nodosum.
Rhizoclonium in crevices. | Under-veg. Hildenbrandietum.
Ill. Bangietum B. fuscopurpureae, —_—- IV. Halosaccionetum, intermingled
in wonderful abundance. | with Monostroma fuscum, Por-
IV. Porphyretum P. umbilicalis, of phyra miniata, Rhodymenia
great extent. palmata and a few Fucus in-
V. Monostroma groenlandicum. flatus.
VI. Fucus vesiculosus, sparse and V. Alarietum, composed of Alaria
miserable. esculenta and A. Pylaii.
VII. Fucetum F. inflati, abundantly. VI. Laminarietum L. saccharinae.
The specimens very variable. VII. Laminarietum L. digitatae.

fi tag

164

H. JONSSON

South Iceland.

Vestmannaeyjar, much exposed,
steep, rocky coast. ?°/s.
I. Ulothricetum U. flaccae.

II. Porphyretum P. umbilicalis.

III. Ascophylletum A. nodosi.

IV. Gigartinetum G. mamillosae,
broad belt, in it Corallina offici-
nalis, Ceramium acanthonotum,
Callithamnion, Delesseria alata.

V. Corallinetum C. officinalis, dis- |

persed in it Laminariae.

Vestmannaeyjar, Vikin, considerably
exposed, sloping rocky coast. 7/5.
I. Ulothricetum U. flaccae.
Enteromorphetum E.*micrococ-
cae.
Acrosiphonietum.
The Fucus-belt.
Ascophyllum nodosum.
F. vesiculosus.
F. inflatus.
. Gigartinetum
G. mamillosae floating
. Corallinetum together.
C. officinalis

IT.

V. Laminarietum L.* stenophyllae. |

. Alarietum A. esculente.
. Laminarietum L. hyperboreae.

Vestmannaeyjar, the skerry,
considerably exposed, sloping rocky

_ coast almost destitute of phanero-

gams. 18/s.

_ Uppermost, Cochlearia officinalis and

rosettes of Plantago maritima.
At the same level, in crevices:
I. Enteromorphetum E.* micrococ-
cae, + Cladophora sericea.

II. Ulothricetum
1 dideewe | on flat rocks
Prasioletum | between
P. stipitatae bee Sat

III. Pelvetia canaliculata.

IV. Fucus spiralis.

V. Ascophylletum A. nodosi.
F. vesiculosus.
F. inflatus.
Under-veg. Callithamnionetum.
Antithamnion.
Gigartina.
. Gigartinetum
G. mamillosae.
Laminarietum
L. * stenophyllae.
Under-veg. Phymatolithon po-
lymorphum.

South Iceland, south side of Reykjanes,
according to C. H. Ostenfeld’s diary.

Stadur, wide foreshore,
considerably exposed. 17/..
1. Pelvetia canaliculata.
+ stunted F. vesiculosus.
2. Fucus spiralis, with stunted
Ascophyllum and
Cladophora rupestris.

3.a Ascophyllum + Polysiphonia fa-

Stigiata, broad belt.
3.b Fucus vesiculosus formation,
in it F. inflatus, widely distributed,
3.c in it Gigartina.

4. Here and there in depressions |

the formations:
Monostroma Grevillei and
M. fuscum.

|
|

+ Halosaccion.
Cystoclonium.

Ahnfeltia.

Dictyosiphon foeniculaceum.
Rhodymenia.

5. Laminaria + Alaria.

The foreshore between Stadur and
Reykjanes. 1°/¢.

1. Uppermost, Porphyra umbili-

calis.

F. spiralis.

F. vesiculosus f. sphzrocarpa.

Enteromorpha compressa.

F. inflatus-formation, widely dis-

tributed and in it Gigartina. -

wo

MARINE ALGAL VEGETATION 165

3. Gigartina, widely distributed. 4. Corallina widely distributed, in
Rhodymenia. | a single pool Halosaccion.
Plumaria elegans. do. Laminaria + Alaria.

Delesseria alata.

Acrosiphonia. In another part:
Monostroma Grevillei. Ascophyllum in quantities between
Chetomorpha Melagonium. 1 and 2.

Delesseria sanguinea and others. |

It would carry us too far to give several more examples from
the diaries, but on regarding the material taken as a whole it is
distinctly seen that there is no other difference of importance be-
tween the two districts with regard to the zonal division of the
algal vegetation beyond the fact that some of the communities and
associations occur in one place and are absent from the other. The
division of the belts varies somewhat in both places which is
chiefly due to the greater or smaller degree of exposure of the
locality (see Part VI).

The most conspicuous difference in the division of the belts
in E. Iceland and S. Iceland is due to the enormous size of the
Corallina-belt in the latter place. This community (Gigartina, Coral-
lina and others; see Part VI) occurs just below the Fucus-belt where,
for instance, in the Vestmannaeyjar it is the dominant one; this
also applies to Eyrarbakki and the south side of Reykjanes, but
perhaps to a somewhat less degree. This leaves less room for the
Rhodymenia-community (Rhodymenia, Halosaccion ; see Part VI), which
also forms a belt below the Fucus-belt; consequently it is not so
large there as in E. Iceland where it is extremely common and in
several places widely extended. In many places in SW. Iceland
the Rhodymenia-community is as large as in E. Iceland.

The sea off the coast of S. Iceland is in movement everywhere,
and calm water is almost unknown. The calm-water-vegetation
proper, which is so common within the fjords of E. Iceland, is.
therefore absent from S. Iceland, but is again found richly repre-
sented in SW., NW. and N. Iceland.

The luxuriancy of the vegetation is somewhat similar in
both places; it appears, however, to be greater in the Vestmanna-
eyjar and the western part of the south coast.

Depth-limit. It appears that there is reason to believe (see
Part V) that the algal vegetation extends to greater depths in the
fjords of E. Iceland than on the south coast, but as this cannot be
regarded as sufficiently proved I shall not enter into it more fully.

VIII. SOME NOTES ON THE BIOLOGY OF THE
ALG ALONG THE COAST OF ICELAND. —

~~ present very little is known with regard to the biology of
the marine alge along the coast of Iceland. What is known,
on the whole, regarding this point is for the most part mentioned
in the “Marine Algze of Iceland” (31) under each species. Some ob-
servations which have been made subsequently will be mentioned
in the following pages. Of these, I regard those which have been
made during winter as the most important, although they are very
incomplete owing to the fact that during winter I have only rarely
been able to make investigations, and then have had access to the
littoral zone only; thus, with the exception of a few species, the
winter-habit of the sublittoral species is not known. Consequently
I can, by no means, treat of the biological conditions exhaustively,
but must content myself with giving a few incomplete contributions.

On the whole, the behaviour of the species is. best known in
spring and summer, less well in autumn, and least well during
winter. From most of the coastal districts there are observations
to hand either only those of a single season of the year, or at most
of two or three seasons. From Reykjavik we have observations of
all four seasons, but those of the winter are sparse, and only a few
species have been observed throughout the year.

The observations to hand are so few and insufficient that a
comparison of the biological conditions in the five coastal districts
in question cannot be made; here, therefore, Iceland is treated for
the most part as an entirety.

1. Duration of Life.

The life-period of the algal species is of very varying length;
in this connection the alge may be divided into two groups: annual
algee and perennial alge.

H. JONSSON: MARINE ALGAL VEGETATION 167

A. Annual alge. The annual species are especially the Green
Algze which grow in the upper littoral zone and are exposed during
each low-tide. The upper littoral zone is that part of the algal region
where the change of seasons is most felt and where winter prevents
many species from continuing life. Such species then produce spores
which live through the winter as such, or in the early stages of
germination. Of annual species the following may be mentioned: —

Codiolum gregarium. Ulothrix-species.

C. pusillum. Ulvella.

Percursaria. Pringsheimia.
Enteromorpha-species. Urospora-species.
Monostroma-species. Cheetomorpha tortuosa.
Prasiola-species. Spongomorpha vernalis.

Cladophora-species.

In addition, some of the endophytic species must be regarded
as belonging to the annuals, although some of them can be met
with at all seasons of the year. As examples of such species may
be mentioned: — Chlorochytrium-species and Codiolum Petrocelidis.

The life-periods of the species mentioned above are probably
of different lengths and it is possible that some of them can pro-
duce several generations during one summer (cf. B6rgesen, 11
and 12). The majority of these species grow luxuriantly during
spring (March—May) and summer (June—August), produce spores
at the end of summer and then die. Some of them, however, con-
tinue life into the autumn (September—November), or at any rate
until September. A few may also be met with during winter (De-
cember—-February), e. g. Enteromorpha intestinalis f. prolifera, Mono-
stroma fuscum (sterile and fruiting), Cladophora rupestris (abundantly)
and Cladophora sericea (sparingly).

Of the above-mentioned endophytic species I shall refer to
Chlorochytrium inclusum and Codiolum Petrocelidis only. Both these
species occur at all seasons of the year. They are found most fre-
quently in the host-plants in the sublittoral zone, where the conditions
of life must be considered to be more stable than in the littoral
zone. I regard such species as short-lived. They are found all the
year round, as probably several generations are produced during

the year.
Among the annual Brown Alge the following must be in-
cluded: — Myrionema-species, Ascocycius and the majority of the

Ectocarpacee, Leptonema, Litosiphon, Isthmoplea, Pheostroma, Ca-

168 H. JONSSON

stagnea and Leathesia (living from June to September). In addition
there are species which may be supposed to be annual, as for
example, Punctaria, Stictyosiphon, Scytosiphon (?), Phyllitis, the ma-
jority of the Dictyosiphonaceew, Chorda-species, etc.

Of Red Alge the following must be presumed to be annual: —
Bangia, Porphyra-species, Porphyropsis, Conchocelis, Chantransia-
species, Ceramium-species and possibly several more. As regards
Porphyra umbilicalis it should, however, be stated that it has been
found at all seasons of the year and at Reykjavik it occurs as
luxuriantly in December—January as during the spring.

B. Perennial Alge. With regard to some of the species it
is difficult to decide whether they are perennial or annual, as our
knowledge of them is incomplete; consequently it is sometimes a
matter of opinion whether they are to be included in the one or
in the other group. Only a few of the Green Alge are perennial,
as for instance, the majority of the Acrosiphonia-species. The latter,
besides being reproduced by spores, have also abundant vegetative
reproduction by means of offshoots; and some of them, as for in-
stance, A. albescens and others, live all the year round in the semi-
littoral zone.

Of the Brown Alge the Fucacee and the Laminariacee are
perennial. It is, however, doubtful whether we are justified in in-
cluding Saccorrhiza dermatodea among the perennials. At Reykjavik
I have seen only old fruiting specimens in the winter, and judging
from their appearance it is very probable that they die during the
winter; nothing can, however, be stated with certainty regarding
this point. 7

In the fjords of E. Iceland large individuals of this species were
growing in the sublittoral zone; I believe they were more than one
year old, but I could not prove this. In Greenland (Rosenvinge,
61, p. 852) perennial or upwards of a year old individuals of this
Species occur.

With regard to several other species of Brown Algez it is not
easy to say at present whether they are annual or perennial. [|
think, however, that the following may be classed as perennial: —
Lithoderma, Ralfsia-species, Sphacelaria-species, Chetopteris, Desma-
restia aculeata, D. ligulata, Chordaria flagelliformis (?).

I think that the majority of the Red Alge are perennial or
can, at any rate, live through more than one growth-period. I shall,

MARINE ALGAL VEGETATION 169

in the following, name some species which I am fairly certain may
be included among the perennials: —

Gigartina mamillosa. Halosaccion ramentaceum.
Ahnfeltia plicata. Poiysiphonia urceolata.
Euthora cristata. Rhodomela lycopodioides.
Rhodophyllis dichotoma. Odonthalia dentata.
Rhodymenia palmata (?). Ptilota plumosa.

Rhodochorton Rothii.

The crustaceous algeze such as Hildenbrandia, Petrocelis, Cruoria,
Peyssonellia and Rhododermis, and by far the greater number of the
caleareous algee must also be classed as perennial.

2. Periodical Changes.

The Period of Activity. The Period of Rest. The period
of activity of the annual species is identical with their period of
life and it extends, probably as regards the majority of the species,
over the spring and summer months. The perennial species and
the species which can live more than one year, have a very long
period of activity which extends over the greater part of the year
with the exception of the darkest part; consequently these species
havea very short period of rest. Although from the observations
to hand it is not possible to fix the length of the period of rest,
yet they indicate that it must be short. The Fucacee may be men-
tioned as an example. Their vegetative growth appears to be very
slight during December—January, and in the case of the older
individuals there is probably none at all at that time; but although
the majority of the individuals of the Fucacee are sterile during
winter yet, even in December, reproductive organs are developing
here and there. Young plants of the summer or autumn appear to
have vegetative growth also during the winter. In the Fucacee-belt,
taken as a whole, the period of rest is consequently extremely short.
In the sublittoral zone I think that entire rest must be of extremely
short duration.

Renewal of the lamina. The young shoots. As is well
known, a renewal of the lamina takes place yearly in the Laminaria-
species. At what time this takes place in Iceland cannot be slated
with absolute certainty, but the observations seem to indicate that
the new lamina begins to grow even in the winter time, as the light
increases. I believe that in SW. Iceland a general renewal of the

170 H. JONSSON

lamina takes place in February—March. In April individuals with
large, new lamine, with the old laminz or portions of them still
attached, are frequently found at Reykjavik, but the majority of the
Laminaria individuals have renewed their laminz by that time. A
few individuals are however met with until June in SW. Iceland in
the act of lamina-renewal. With regard to some of the most common
species the following may be noted: —

Laminaria saccharina in SW. Iceland (1897) was frequently found
in the lamina-renewal stage in April, while some individuals were
_renewing their lamin in May. Laminaria digitata: some individuals
were renewing their lamine in April and until June in SW. Iceland
(1897). Laminaria hyperborea in SW. Iceland (1897), some were re-
newing their laminze in May—June.

L. hyperborea was found renewing its lamine in July on the
north coast of Iceland. This was observed only once, therefore it
cannot be concluded from this that the lamina-renewal stage com-
mences later or lasts longer on the north coast than in SW. Iceland.

In the Ferées (B6rgesen, 11 and 12) the lamina-renewal stage
occurs at the same time as in SW. Iceland.

On the west coast of Sweden the renewal of the lamina takes
place during winter (Kylin, 45) and in Laminaria saccharina and
L. digitata the young leaf, in December, is a quarter the size of the
old one; in April it is only exceptionally that individuals are found
with a portion of the old lamina attached. The renewal of the lamina
in L. hyperborea takes place later, and in April the new lamina is a
quarter the size of the old one, and in the beginning of July a
portion of the old lamina is still present.

In connection with the lamina-casting species the following may
be mentioned: — |

Desmarestia aculeata has been collected bearing the brown, as-
similatory hairs in March—May in SW. Iceland, in May in NW.
Iceland, in June in E. Iceland, and in July in N. Iceland. This
appears to indicate that the hair-bearing stage occurs later on the
north and east coasts, or that it lasts longer. The species behaves
in the same manner in Greenland (Rosenvinge, 61, p. 857) where
the hairs are cast off, at the latest, in June in South Greenland,
while hair-bearing individuals are found in July and August in
North Greenland. In the Feerées it has been observed with hairs
upon it in May—June (Borgesen, 13, p. 445), but hair-bearing
individuals were, however, rare in June. On the west coast of

MARINE ALGAL VEGETATION Lyi

Sweden (Kylin, 45) the hairs are cast in June, but (young) hair-
bearing individuals may, however, be met with in July.

Polysiphonia urceolata has hair-leaves in the spring, summer
and beginning of autumn, but individuals without hairs are found
side by side with hair-bearing ones from May to August. In De-
cember only hairless individuals have been observed at Reykjavik,
and in January—February only hairless plants have been collected
in N. Iceland.

Rhodomela lycopodioides has been collected with hair-leaves in
March—July, and hairless in June—August in SW. Iceland; with
hair-leaves in April—December, and hairless in July—August in N.
Iceland; with hair-leaves in June--July and hairless in May—July
in E. Iceland. In the autumn this species had cast off its leaves
and branches in SW. Iceland.

In addition to this, the following instances of the occurrence
of young shoots may be mentioned: —

Odonthalia dentata. The young shoots in this species are readily
recognized by their paler red colour. Material from January—
February bears young shoots. The latter are easily recognizable in
January, and have probably begun to grow out in December. The
young shoots then increase in size, and the colour becomes gradu-
ally darker month by month. In material collected in June—July
the length of the year’s shoot may even then be determined in
some of the individuals, but I believe, however, that it is in July
that the shoot is almost full-grown.

Polysiphonia fastigiata has young shoots in December at Reykjavik.

Odonthalia shows distinctly the period of development of the
vegetative shoots in the sublittoral zone, and I presume it may be
taken for granted that the other sublittoral species do not differ
very much from it as regards this point.

In Greenland the formation of the new shoots begins in Feb-
ruary—March (Rosenvinge, 63, p. 239), and the growth is con-
tinued until August or during the whole summer.

In the FerGdes the new shoots begin to appear in the latter part
of autumn (Bérgesen, 12, p. 828).

From Spitzbergen (Kjellman, 36) some sublittoral species are
known which form new shoots during the winter, as for instance,
Delesseria sinuosa in January, and Rhodymenia palmata from No-
vember to May.

72 H. JONSSON

The Fruiting Period. In the table given below is indicated
the time at which the species ‘have been found in fruit. A + sig- »
nifies that the greater part of the individuals in the samples gathered
were fruiting; a + signifies that fruiting and sterile individuals
occurred in almost equal abundance, or sometimes that only a few
fruiting individuals occurred; a — signifies that only sterile indi-
viduals of the species were found.

In the majority of the annual species the fruiting period
coincides with the vegetative stage, and thus growing vegetative
shoots and sporangia are frequently found on the same individual.
These species fruit comparatively quickly and the young, or purely
vegetative, stage is of short duration. The fruiting period extends
over spring and summer probably in the case of the majority of
the species. They do not, however, behave similarly in this respect
in the different coastal districts. Urospora Wormskioldii, Monostroma
Grevillei, M. undulatum, Ectocarpus tomentosoides and Litosiphon filt-
formis are all decidedly spring plants at Reykjavik, but in E. Ice-
land they have been found bearing fruit far into the summer.
Leathesia difformis is a decidedly summer species at Reykjavik, it
has been observed fruiting in June, July, August and even into
September, but it was dying away in the middle of September. At
Reykjavik its life-period coincides with its fruiting-period, but in N.
Iceland it has been gathered in a sterile condition in September.
This species appears to behave in the same manner on the west
coast of Sweden (Kylin, 45) as at Reykjavik. Moreover the fact
may be emphasized that at the latter place Enteromorpha Linza is
usually a summer and autumn species.

With regard to the perennial species, it happens both that the
vegetative growth and the fruit-formation is simultaneous, and also
that the two stages occur at different times. A purely vegetative,
young stage, more prolonged than in the annuals, is found in
several of the perennials; thus, I think that I have seen indications
of Alaria and Laminaria species being in a purely vegetative stage
throughout the first year and perhaps longer.

Kylin (45, p. 274) divides the perennial species into three groups
according to their life-activity: —

Group 1 includes species which carry on vegetative and repro-
ductive work all the year round.

Group 2. Species which carry on vegetative work the whole
year, but reproductive work only for a part of the year.

MARINE ALGAL VEGETATION 173

Group 3. Species which carry on vegetative and reproductive
work only during a part of the year.

In referring the Icelandic species to these groups the difficulty
at once arises, that we lack knowledge regarding the behaviour of
a number of the species during winter. Such species cannot there-
fore be grouped with any certainty at the present time. True, we
may judge with some probability how they behave here during
winter by a comparison of their winter-activities in other places,
provided these are known; but as it has been shown that one and
the same species often behaves differently in two distantly situated
places, a satisfactory result could not be arrived at through such
a comparison which has, for that reason, been omitted. I therefore
mention a few species only, which I think I can group with some
certainty.

Group 1. The following species belong to this group: — Hilden-
brandia rosea which fruits all the year round. Rhodymenia palmata ;
it might appear doubtful whether this species should be classed as
a perennial. Kjellman (36, p. 150) regards it as an annual plant
which forms tetraspores twice, once as a young plant and the
second time just before it dies. It appears to me that the new
shoots which arise early in spring from evidently old fronds, show
that it lives through at any rate more than one period of growth.
Pelvetia canaliculata bears fruit and carries on vegetative work the
whole year at Reykjavik. In December—January the fruiting indi-
viduals were comparatively few, but there was a quantity of young
plants almost all of which were in the “rosette” stage. It is per-
haps doubtful if this species belongs to this group at all.

Group 2. The Fucacee belong to this group (with the exception
of Pelvetia (?)). Fucus spiralis produces fruit in spring, summer and
autumn. In December (1911) it was sterile, and young plants were
found in quantities.

Ascophyllum nodosum, Fucus vesiculosus and Fucus inflatus, all
these behave almost similarly. In December and January I saw,
here and there, individuals with very young receptacles, but by far
the greater part were sterile. In spring and early summer these
species are found everywhere with full-grown receptacles. In the
latter half of August they are sterile everywhere and at that time
only a few individuals, which must be regarded as stragglers, are
found bearing receptacles. Of F. inflatus | saw no stragglers in Au-
gust. In September also they are sterile. In the first half of October

174 H. JONSSON

both Ascophyllum and F. inflatus are sterile, but at that time a few
individuals of F. vesiculosus bear young receptacles. From the middle
of October until December there are no observations to hand from
Reykjavik. The usual course, with regard to these species, appears
to be as follows: In the latter part of the autumn the development
of the sexual organs begins, and is continued throughout the winter;
in March the species are found everywhere with ripe sexual organs
and the spores continue their development until the latter part of
the summer.

Kjellman (36, p. 195) records with regard to Ascophyllum no-
dosum in Finmark, that it had numerous receptacles in July and
the first half of August, was sterile in the latter part of August,
and that new receptacles had begun to appear in October. Foslie
(18, p. 64) records with regard to the same species in East Finmark
that it has abundant receptacles in July and is sterile in August.

In the FerGées (BOrgesen, 12, p. 830) Ascophyllum nodosum has
young receptacles in December and fruits during the whole summer.

On the west coast of Sweden the sexual organs begin to de- ©
velop late in August or early in winter (Kylin, 45, p. 106), and by
the beginning of June the receptacles have fallen off.

Fucus inflatus probably behaves in East Finmark in a similar
manner as at Reykjavik. Foslie (18, p. 67) mentions receptacle-
bearing individuals in June—July and the first part of August. At —
Spitzbergen it bears fruit during winter and Kjellman (36, p. 204)
found germinating spores in December, January, February and
March.

To Group 2 belong, in addition, probably all the Laminariacee,
Rhodochorton Rothii, Polysiphonia urceolata, Halosaccion, Gigartina
mamillosa, Odonthalia and probably many more. Petrocelis Hennedyi
belongs also most nearly to this group; it has been found producing
fruit the: whole year, but in spring, summer and autumn only a
few fruiting crusts are found, while the winter appears to be the
ordinary fruiting period. Chetopteris plumosa I include, although
with doubt, in this group.

‘Group 3. To this belong Desmarestia aculeata, which has been
found fruiting in October, Rhodomela lycopodioides, Delesseria san-
guinea and others.

MARINE ALGAL VEGETATION

The Fruiting-period of the Species.

175

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O, TEISIG fos Dele eee: oe er aaa
PoEpiyropsis: COCcinea ..........55...

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MBaneransia, Microscopica..:............
2 Ade? <6 6+ lie ioe. ci er

2, VUES Cp 2) aang nace ee arene ee |

Midis erispus;.... 00... 0. 0c 2b ew Dee
Sasarcina mamillosa.. 0... 2... e ee ees
Puente liCatA (s)) 2 ks 8 ak eae ae
Phyllophora Brodizi * interrupta ........
PeiMeMNDEANIIONIA . ... 6. soe sete ee

Beepecwiix TArtZI. .). 2th. ye ae es
Cystoclonium purpurascens.............
MeHCRE MACE CUNY! 622 6% 5 See 'e es ee ws wl
SU UTe a Ue er
Rhodophyllis dichotoma ......,......-..
uomymenia palmata..-.....2.....-.066%
Moamenrania’ Clavellosa..*...........06.-65«

MOE MOR PEN EVO oer 2 0, =e othe 3 (alle = 34 aa tele 8
Exerosipnonia parasitica’. .......50...50.%
Relysiphnonia urceolata ...5 0... 26. se es
PPRRISPMMIRE ARE. ot. =< ee ee ak eos
LP. DIRGUIGEL edie an ae ee
PMR CUES 7 Ute. «= oy. oso: Sis asset oe es ales
Rhoedomela lyeopodioides ...............

Gilemimaiia dentata 2.0. ee as |

Callithamnion® Arbuscula................
(O., SO0; Cn Cig er nar
Eiiimiatiae Cleans... 2s bee es wee

Ua Pe UIMIOSA «21.5 5 ec ee Bee |

GC COMAUA Pets se whee gs eel ao Rare ee
Antithamnion Plumula * boreale.........
PARISONS EUNEN Me © Sony ie! a) cM a) oes os tod aS ave alas
Ceramrum acanthonotum ..........

CeMestonschAaMipul 2)... 2 tee ee es
MeIritICMIOSUMM.. F).. oi ee het chem e

Spring Summer Autumn Winter
~ -
al a gil
al: ale
+
+ pie oh
oa al
- -
mae + ah eee
+
— — alk
Ae slew
elie a
eile ae ile sd.
= sell
al! -+- =
at en — Elis
aie ane —
ae sip a
ens =e nu +
a
an aE -L =a
a's ib — ae
pes pilbs ity
= -
~ - 1 ~
Wiad Ae ape +
Bu +
ale =i
ale ag + —
4. -- ae +
adie a alte
—_ ais
as a

ede

176 H. JONSSON

The Fruiting-period of the Species (continued).

Spring Summer Autumn Winter

Ceramium circinnatum +. 2... 2. eee ee:
CGharborescensis: 23) i eee ae
Cratlonmtieurn ste os eee: cae Soe te ten

b++++

Ri penicrllitorime, se) Hcvs So tah Cee ees cle
Rumenibranaceum . 2... uc he one onc eee ok ee

ee)
+++ 4441

Dalsea Vedas i gc wa eee ake ee eee
Petrocelis Hennedyi......... ee N ay nee aie
Cruoria :arciieag. 3, uct ees «eters Pe =
Gaspelttar sets Mee ee apd ash aed. eine nce soe ge:
Peyssonellia Rosenvingii................
Rhododermis' parasitica :. 200. .e. 02s. S
Lithothamnion glaciale ¢2 05.0. 228 ee. o). =
Ee Une ri ae ee ain | oa Whey as area eae: =
Li tOPIIORMLE 242 save ists ce omy Bx bees onnonaee , =
DL AMAVESCEMS cc's raves & 6. eo noe cee arcades =

eee eee

[eee]
|

Phymatolithon polymorphum........... — —
Clathromorphum compactum............ — — + — —
Lithophyllum Crouani.................. —
Dermatolithon macrocarpum............ +
Corallima officimalisy 2 os..¢.004 . ctw se siuahaciees —-

|| +

C
=
>
fo)
or
@
Ly)
5
tt)
s°
as
=
ie)
i)
5S
4
|

-
|

-

PS Clavatae ny Sete shih oh ee ais tea ee a
Ri Verrucosa yi Ge ee bee

ze)
=
e
[)
s
a
eyek
b | +

wa
Q
o
c
a
9
|
|
|

CD

Myriowema vulgare’). 205 cc ies coe eerie hele
My Gorin ine cites oo. Lee cc cdeueencee er neon ie atane
MO SlObOSUMIT Sm .j5 Poos eee ae es oh ete oe
Mi feerGense cy. ie/iid aes CR nee eyweaite phe miata
M. La nibinaiehce 0% 3.-os-naxshtok i ayers aeoietechab ate hes
Ascocyclusislandicus: .<. 2.21. has geen ves
Microsyphar Polysiphonie ..............
Streblonema <ecidioides 2. ..6..5,5... +0 |

+++ |

+h + +41

MARINE ALGAL VEGETATION

The Fruiting-period of the Species (continued).

ahs

Streblonema Stilophorez v. czspitosa.....
PavetlaMITOTANS 2.) cde eee we eke
Ectocarpus tomentosoides...............
So, CSU GUL S0S 1 SS a

(DSRS re |

SRE RLETINCIES 250.02 sie 5 na eee yee so eee we
iS. UE SECU 2S a rs ee oa ee
&, SSS Gt es ee ial
Leptonema fasciculatum v. subcylindrica. .
IMIS UT PUCICOLA< 2(.)5). dete sleleye ele e od oe oe
Sphacelaria britannica ........ 2.0.6. 00 0s
cy DEY LLCS S aah ee eer
PMOL MMR ARE ER sti Sn 0g. snt mlhate ats lg oha “whp val oy Bvt aaa
Ciretopterts plumosa .. .--.6..055 5 e0ee ee
Omphalophyllum ulvaceum.............
Eumetaria plantaginea.. 7... 6s. e see ea ee
PALOSIPNGM. MNTOTMIS. 2... ke ee oe ee ae
isthmoplea sphzrophora...............:

Seremvesipiai COrtilis . 2... 26. ee ee eee |

Phezostroma pustulosum.......... hss) ayete
Neveosipuon iomentaria :.....5...+.008+
PMVMUTISS ZOSLETITONAS | si cee een ee te ee
ve DESC (2 eg SS eee ee
Comodesme bulligera....o.-...... 9.205
Dirctyost phon Ekmanit ii. .s i... 6. ee bee ek
SOMO AGN nen ay an'e < sle aid eho\os 2) Pemsteln wis
, CIMCIE Cee no cen
DOEOMVADOSUS 2.7.6 he ew tne te 8 tee
De hippuroides ......... cs Maree use
DAIOEMICUIAGCEUS 4 lini c a6. lee cele ee hee ae oe
DP ESMMUARCSUMACVIPIGIS 22... calecicle c/o e 4's vs we ei
WPETOUNGCALAL Se 2s a ais ws aie ete'e| sa a. # bee wh
PRE PSUIN CA ate veye se 2 sic0: Na 6, we Ba) Beds, sa es
Gastastien VIrescelsS.... 6... 0g. ele eee
Peariesia CivfOrMis .ia< 0d... ne aah en.»
Ghocdania flagelliformis ..... .. 0.5 ..ses 6s
Givomda TOMENTOSA... 0. xfer aie es ek ew ale
PO EMNEEIND Re te oad oe xs, weve wines 6 mis 8 a bie sae
Saccorrhiza dermatodea..........0...05+
Laminaria saccharina..........s2s0esee
AE PRCCROCIISIS arenes caf) aia. n sop (os) Ce komma sw as
PPPS TUES oid webs os 6 ee a Sere wie sj oy wejeapus ene
TO GAPILACA y's ye sade ce pe telah Sinn e ees

hyper bored. 6... eee wel ewe nn

The Botany of Iceland. I.

Spring

Summer

Autumn

Winter

bE t+++++++++

|

E+E

+t+++ |

L

+H

H+ +++4++4+4+4++4

ek ETS See ey

|

PIPER E+E+H4 I

b+ +F+ +) + + EI+4

| ++

178 H. JONSSON

The Fruiting-period of the Species (continued).

Spring Summer Autumn Winter

ee

Alania wPylan gies Cee boa we oe le
As CSCUMe Mita, Acer oo baa cceng ox, cee
EP ELIS ES PINAliSHy oh EES eu wie ee
Be rinflat usp: Sk clan ks hese ho tate” other ale

b+++
P+ etl ttt
|

7

;

|
+4+++4++4 |
+44

Chlorophycee.

Chilorochytrium’!-Cohmite. 062.0. Ay oo +
Caimiclinstinn’ Saeed ic. ./ ocr a cag ee +

C. gregarium ys, acer ws sae bees ate gin nag |
C. qpstlinmaig ster | waeges 5 we hohe oe eel! +
Percursarlaaperemrsdie = <.sins 2s eee he
Enteromonphaaureola®. toss {on Sats ok
By MANA Fleas Socios oe er oS osc peaks Ree oe

SS
bie
=)
oF
(qr)
¢2]
a5
i=}
es
=r)
i¢2]
nae.

i++

Monostroma groenlandicum.............
IM Gre vallen (ster. de. entries eetpieks nish We oa

++tt+b414+

=
A
:
F

| +4+4+4 |

Prasiolaspolyrmhivas o. o.c 82.6 ent oe ee
DP. fumiunace ae. aaa ceeiae 6 soos ested cas oe ee
Pe Stipibabat. «cee a oe piers. cielo erage | ==
Ulothrix consociata var.islandica.. ..... —
Ussubtisevida¢iausina. chet te et ee
LD soSeCndOlacea ein. Geert. So. an eee

+
WD, laced. cee oo oem cree ect ao +
+

b+++4 1 |
|

A. EDEN S cy tee cy sph S io. 2 BEE ea eae ee
Bolbocoleon piliterum 22.254 esas te ek
Ulvellaviucicolat=2 by 2.6 eb Sas oe
Pringsheimiarseutata) .:.5. 4k ee Pea a8
Ochlochtesterox. i304. 6 ee oe ee
Urospora amirabilistigi3 sv ase a oe
U. Hartzilj nec cee sea. oe oa

ee

++

|
+++ 4144

+++

MARINE ALGAL VEGETATION 179

The Fruiting-period of the Species (continued).

|

Spring | Summer Autumn Winter

Cheetomorpha ‘tortuosa. 0... ees ee =
Meer tclasommuinie! ike. 2 eRe Deby SL A +
ninizoclonium riparium ...............5. —
svonsomonrnplia vernalis.........003 06.0%
PeGosipmOmia, albeScens 52... 5.0802... et

+-
| ICWIE (gees Cae et eee +-
+-

+++ |

6. [IVS UID Ce) Saeed cae geen ene aera
BRERA UE UMOTMALS vi. ad x sccisy eusreayeyne een Sige sina
PMEMLCTMUCHMUILOLINIS sc. oe bec cee ne ete ene
Wladeplora TUpestris .....5. 0. .k tte eee ae
a LUPE. 6G URS a a ae =
CIEE Ta ctd. ts Gr netiten +. vebd ea ctha 2850 « 4
Pe AMUICCSCONS 66. Soo 0d ss Baye, ou Alea cje wis os
Cas SUREACUIITS wages eee ae er Leeda
Gomontia polyrrhiza.: 2. ce

Ostreobium Queketti .,......6.0.0.0 0.000% — —

b+ +4444 4 |

ae

LE
|
ete

Cyanophycee. |
mleurocapsa amethystea............5.025 a = = —
Piectonem=a NOFVESICUM. 2... ee | aa
Paormidium: autummale. . 6.0... 6.608 cas ase
Spe IMAL SUIDSALS AL. ccs cares jai as ces oles ole 04» = | ae
Saleglacix: SCOPULOTUM........ 22+ ss08 0d. == ==
Pa UN MIRE ARIAL [edie ey a) anc g = “sus, &. a:t0! Gace fm saree ee 6 =

By looking through the above table it is seen that in the case
of a number of species the fructification-period is of long extent.
Some nine species have been found fruiting all the year round,
but I presume that by future investigations it will be proved that
many more species bear fruit during the whole year. Kjellman
(36) mentions 11 species which bear fruit all the year round in the
Arctic Sea, and Rosenvinge (63) mentions 6 species which fruit
all the year round along the coast of Greenland, and he adds that
probably there are many more.

If we consult the table as to which season of the year is richest
in fruit-bearing species it is easily seen that summer stands highest,
with 64°/o of the total number of species; then comes spring with
42 °/o, and after that autumn with 33 °/o. As the conditions during
winter are so very little known no percentages can be given for
that season.

It is well-known (Kjellman, Rosenvinge, Boérgesen) that
i

180 H. JONSSON

in the case of many species both the vegetative period and the
period of fructification is longer in the Arctic Sea and the northern
part of the Atlantic Ocean than in the remaining more southern >
part of the boreal area of the same Ocean. It holds good also
for Iceland, that both these periods are prolonged. Iceland, the
Ferées and Greenland agree also in the fact that the summer is
richest in fruit-bearing speCies.

3. Littoral Winter-vegetation at Reykjavik.

The littoral vegetation changes its appearance according to the
season, and this is especially owing to the annual species. The
vegetation is most luxuriant, and richest in species during spring
and early summer; in the latter part of the summer the annual
species decrease in number and a quantity of them disappear, and
in the autumn only a small number of them is left. During winter
only a few short-lived species are found, and some of them play
either no part, or only an unimportant one in the vegetation which
by that time is usually composed of perennial species. Thus, the
number of the species of the winter-vegetation is much less than
of the summer-vegetation because the Chlorophycee, which is the
group in the littoral zone that is richest in species during summer,
are few in number during winter; also the number of species of
the Phewophycee is greatly reduced in the littoral zone during winter.
It is the Fucacee which form by far the greater part of the mass
of plants in the littoral zone, during the winter as in the one
seasons of the year.

In December and January, in the winter 1911—1912, the vege-
tation of the upper and lower littoral zones was composed as
follows: —

Highest of all a Prasioletum stipitatz occurred in patches.
Prasiola stipitata grew luxuriantly and had a normal appearance.
It was not injured by the winter climate.

Below that came a well-developed Porphyretum umibile
calis, occurring also in patches on account of the surface-form
of the coast. The Porphyra was both sterile and in fruit and had
an entirely normal appearance.

Below that again came the Fucacee- “coamtiee by which, as is
usually the case there, consisted at the top of a Pelvetia-Fucus
spiralis-belt and at the bottom of the usual Fucus-belt (Fucus vest-

MARINE ALGAL VEGETATION 181

culosus, Ascophyllum nodosum and Fucus inflatus). The vegetation
was as luxuriant during winter as in the other seasons of the year
when, however, the epiphyte-vegetation of the Fucus-belt is excepted.
For further information concerning the Fucacee see p. 173. Epi-
phytes, for instance such as Pylaiella littoralis and Elachista fucicola,
which at the other seasons of the year are common everywhere in
the Fucus-belt, were not observed. On the other hand, Polysiphonia
fastigiata occurred in abundance on Ascophyllum. Of intermixed
species in the Fucus-belt Cladophora rupestris may specially be
mentioned ; it occurred abundantly as well-developed specimens with
the uppermost apex of the shoots destroyed.

A Hildenbrandietum occurred ‘everywhere in the littoral
zone, of similar appearance and extent as at the other seasons of
the year. ,

In rock-crevices at the level of the Fucus-belt a well-developed
Rhodochortonetum Rothii was found. The Rhodochorton was
sterile and Pleurocapsa amethystea was growing upon it. In such
crevices were noted in addition: — Pylaiella littoralis, sterile and
in very small quantity; Acrosiphonia sp., a few filaments; Clado-
phora rupestris, abundant; Polysiphonia urceolata, sterile and with-
out hairs and sparse, and Callithamnion sp.

The vegetation of the Pools was on the whole very poorly
developed. The upper pools, at the level of Pelvetia and Fucus
spiralis, contained a few small individuals of Cladophora sericea f.,
a few filaments of Pylaiella littoralis, a few small individuals of
Monostroma fuscum, and Diatoms in abundance. In such pools
Cladophora sericea forms a dense and luxuriant vegetation in spring
and summer. Fucus inflatus f. linearis grows also in these pools in
spring and summer, but was not found there in winter. It appears
as if this form is annual, at any rate in the upper pools. The
lower pools, almost at the level of the lower part of the Fucus-
belt, contained only a poor vegetation. Monostroma fuscum, how-
ever, occurred fairly abundantly, but Halosaccion ramentaceum was
found more sparsely; on Halosaccion was growing Elachista fucicola
y. lubrica with unilocular sporangia and somewhat sparse assimila-
tory filaments, and also Ceramium sp.

Below the Fucus-belt, in the lower littoral zone (upper part
of the semilittoral belt) were found at Efferseyjargrandi, Rhody-
menieta distributed in patches here and there, many of them of
rather considerable size, The majority of the individuals were old,

182 H. JONSSON

with abundance of new shoots. The Rhodymenia-vegetation is never
really luxuriant in this place; it attains, however, to a greater
luxuriancy in spring and summer than during winter. Halosac-
cioneta occurred also here and there, but sparsely and not nearly
as abundantly as in spring and summer, but the same applies to
it, as to Rhodymenia, that it never grows really luxuriantly in this
place. There were noted in addition: — Monostroma fuscum, Py-
laiella littoralis (extremely sparsely) and Enteromorpha intestinalis f.
prolifera, also extremely sparsely. Lithodermeta occurred abun-
dantly and were well-developed, but the species was sterile. A
Sphacelarietum composed of Sphacelaria radicans was found here
and there. The plants were low in growth, sterile and without hairs.
A Gigartinetum occurred here and there of about the usual extent.

Just below the limit of low-tide I gathered the uppermost
stragglers from the sublittoral zone. There Laminaria saccharina,
L. digitata, L. hyperborea and Alaria esculenta f., were growing. All
the Laminarias were sterile and the new laming had not begun to
grow. The frond of the Alaria was usually torn in pieces; in the
middle of the stipe there were old sporophylls. The uppermost
part of the stipe, just below the leaf-base, was young and evidently
growing. Lowermost in the part that was growing, small projections
could be seen on the two sides, which were evidently the begin-
nings of new sporophylls.

The following species were found thrown ashore: — Lamt-
naria saccharina, L. digitata, L. hyperborea, Alaria esculenta f., Sac-
corrhiza dermatodea, Desmarestia aculeata, Odonthalia dentata, Petro-
celis Hennedyi richly fruiting (on L. hyperborea), Rhodochorton Rothii
(on L. hyperborea), Delesseria sanguinea with the small tetraspore-
bearing fronds, and Ptilota plumosa with tetraspores.

For the further understanding of the winter-life of the algz it
may be mentioned that the winter of 1911—1912 was unusually
mild at Reykjavik.

BIBLIOGRAPHY.

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nova, Lunde, 1846.

— Species algarum rite cognite, I-II, Gryphisvaldiz, 1821—1828.

Agardh, J.G., Bidrag till kannedomen af Spetsbergens alger, med Tillag.
Kgl. Sv. Vetensk. Akad. Handlingar, Bd. 7, Ne 8, Stockholm, 1868.

— De Laminarieis symbolas offert. Lunds Universitets Arsskrift. Tom. IV, 1867.
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Ahlner, K., Bidrag till kannedomen om de svenska formerna af algslagtet
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Areschoug, J. E., Observationes Phycologice. Particula prima, de conferva-
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— Phycez scandinavice marinz sive Fucearum nec non Ulvacearum, quz in
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Berthold, G., Ueber die Vertheilung der Algen im Golf von Neapel. Mitth.
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Boye, P., Bidrag til Kundskaben om Algevegetationen ved Norges Vestkyst.
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Borgesen, F., Om Algevegetationen ved Feréernes Kyster. Kjébenhavn og
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— The Alge-Vegetation of the Faréese Coasts. Botany of the Ferées. Part III,
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— The Marine Algeze of the Ferées, Botany of the Ferées, Part II, Copen-
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— and Helgi Jonsson, The Distribution of the Marine Algz of the Arctic
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De la Pylaie, Flore de lile de Terre-Neuve et des iles St. Pierre et Miclon.
Paris, 1829. °

Farlow, W.G., Marine Algze of New England and adjacent coast. Washington
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Falkenberg, P., Die Meeresalgen des Golfes von Neapel. Mitth. aus der zool.
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Foslie, M., Contribution to the Knowledge of the Marine Algze of Norway.
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— The Norwegian forms of Lithothamnion. Det Kgl. norske Vidensk. Selsk.
Skrifter, 1894. Trondhjem, 1895.

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184

BIBLIOGRAPHY

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Huber, J., Contributions A la connaissance des Chetophorées épiphytes et
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Icones Flore Danicz, Vols. 1-16, Hauniz, 1766—1877.

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uate - ERRATA.

P. 3, line 6, for of read off.
P. 29, line 15, for Kylin (43) read Kylin (45).

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