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The Danish Biological Station

to

The Board of Agriculture.

By

C. G. Joh. Petersen,
PhD:

Translated from ,,Fiskeri-Beretning for 1907”.

Copenhagen.
Centraltrykkeriet.
1908.

From

The Danish Biological Station.

MV E

1908.

Copenhagen.
Centraltrykkeriet.

1908.

Contents.

On the Ecology and Distribution of the Grass-Wrack (Zostera marina) in Danish Waters. XVT,
C. H. Ostenfeld.

On the Ecology ånd Distribution of
the Grass-Wrack (Zoszerada martncet)
in Danish Waters.

Motto: It is certainly this plant which for a
great part conditions the fish-wealth of
our Coasts.

(Dr. C. G. Joh. Petersen in Beretning fra den

danske Biologiske Station I, p. 168)

(With 9 figures.)

By
Dr. C. H. Ostenfeld.

III.

JAVÆ

WIE

NINE

Contents.

Introduction sn såe Eee TEE EET SEE ENE EET EGER ER
StructureandfeørowebeELESTEEE EE
1. The leaf-bearing shoots
2. The flower-bearing shoots.
The outer conditions for the growth of the Zostera
1. Salinity of the water.
2. Shelter.
3. Light.
4. Nature of the bottom.
Distribution of the Zostera in Danish waters .
West coast of Jutland.
2. Lim Fjord.
3. Kattegat.
4. The waters between Jutland and Samsø including Aarhus Bay.
5. Little Belt.
6. Odense Fjord.
7. Samsø Belt.
8. Great Belt and Langeland Belt.
9. North coast of Zealand.
10. Ise Fjord.
11. The Sound.
12. Smaaland Waters.
13... Guldborgsund.
14. Grønsund, Ulvsund and Bøgestrøm.
15. The Baltic (Danish Shores).
The Zostera Vegetation as a habitat for other plants and for animals....
1. The pure Sand-Zostera Vegetation.
2. The pure Mud-Zostera Vegetation.
3. Red-Alga Zostera Vegetation.
4. The Brackish-Water or Green-Alga Zostera Vegetation.
BEGAVEDE aser od aen To Oos DE TODD nos ode Do .
1. West coast of Jutland.
2. Lim Fjord.
3. Kattegat.
4. Little Belt.
5. Great Belt and Langeland Belt.
The remaining waters.
Other marine Phanerogams........ EET Eg ME TODD dEER re
1. Zostera nana.
2... Ruppia maritima.
3. Zannichellia palustris.
4. Potamogeton pectinatus.
Table of measurements of the length and breadth of the leaf, and of the
length of the flowering shoots....... eros od ÅgKo ERNE ERR
mhesmaterialteollectedfand to bs mve EEN en ele ere eee Er keee

en

17

39

I. Introduction,

Åt the request of Dr. C. G. Joh. Petersen, Director of the Danish Biolo-
gical Station, the author made a three weeks cruise in Danish waters within the
Skaw on board the Biological Station's steamer »Sallingsund« in July and August
1901, in order to investigate the distribution of the eel-grass or grass-wrack
and to study the ecology of this plant. As assistant at the Biological Station I had
already the year before taken much interest in the grass:wrack, the extensive
growth and distribution of which is of much importance to our fisheries. The
following pages show the results of my investigations. Unfortunately, I have been
so much occupied by other work that this report is only now completed six years
later; yet a very brief summary of the most important results has already been
published in the »Botanisk Tidsskrift« (Vol. 27, December 1905, pp. 123-125).

The grass-wrack (Zostera marina L.) being such a common and peculiar
plant, it is only natural that many investigations of various kinds should have
been published regårding it. The object of my investigations has therefore mostly
been to extend our knowledge of the conditions of the growth and occurrence of
this plant in the Danish seas and less to study the structure, life or biology of
the plant itself. In the first and third reports of the Biological Station (1891 and
1893), Dr. C. G. Joh. Petersen has already recorded similar investigations, made
in Holbæk Fjord and the Little Belt; further information on the distribution of
the eel-grass in the Kattegat is to be found in: »Det videnskabelige Udbytte
af Kanonbaaden Hauchs Togter« (København 1893, pp. 437—438). In
all three publications the text is accompanied by several charts showing the distri-
bution. Information on this subject may also be gathered from later reports of
the Biological Station (especially Reports IX and X, 1900 and 1901). With regard
to our Baltic shores, lastly, it may be mentioned that in his paper on the »Algen-
flora der westlichen Ostsee deutschen Antheils« (6. Bericht der Komm. zur
wissensch. Unters. der deutschen Meere in Kiel, 1889) Prof. J. Reinke of Kiel
has discussed the eel-grass vegetation off the Schleswig side of the Little Belt and
in Kiel Bay.

A work of great importance but of a somewhat different kind is the »Dansk
Plantevækst, I, Strandvegetation« lately (1906) published by Prof. Eug.

4

Warming, the 12th chapter of which deals with the »sea grasses« (pp. 133—198);
in this the life-history, structure and distribution of the grass-wrack are discussed
thoroughly.

Of important sources of information from the purely botanical side concer-
ning our plant may be mentioned: C. Raunkiær's work »De danske Blomster-
planters Naturhistorie«, Vol. I, (1895—99), in which the structure of the eel-
grass is described (pp. 120—125) and the paper by Ch. Flahault on Zostera in
O. Kirchner, E. Loew and C. Schroeter: Lebensgeschichte der Bliten-
pflanzen Mitteleuropas, Bd. I, Lief. 6, (1906, pp. 516—529). All these
papers contain a copious literature to which I may refer any one desirous of
further information respecting the natural history of the eel-grass.

Lastly, I would draw attention to a small interesting pamphlet called
- (translated into English): The use of Grass-wrack for stuffing pillows and
mattresses and its proper treatment for such purposes as a substitute
for horse-hair, written by M. C. G. Lehmann (Kjøbenhavn 1812) and to an
enlarged German edition a few years later (1814) entitled: »Der entdeckte
Nutzen des Seegrases zum Fillen der Kissen und Polster«, von Dr.
M. C. G. Lehmann (Kopenhagen bei Schubothe). The author recommends the
use of the dried leaves of the eel-grass for stuffing mattresses and the like. He
concludes the German edition by saying that the eel-grass »gewåhrt ein Lager,
weicher als Heu, gesunder als Federn, dauernder als Stroh, wohlfeiler als sie alle.«
It is also now-a-days a well-known fact that the leaves of the eel-grass are extens-
sively used in this way, and Dr. Lehmann is evidently of opinion that he has had
the honour of discovering this use. In reference to this, I may mention that most
of the roofs of the houses on Læsø are still thatched with dried eel-grass instead
of straw and that elsewhere in our country the same material is also made use of
to make the ridges of the roofs water-tight.

Eel-grass may also be used as manure, mostly perhaps on account of the
substances entangled in it (sea-algæ, dead molluscs, snails etc.) as the leaves them-
selves have an unusual power of resistance against crumbling.

It is however the importance of the grass-wrack to the sea and its fauna
and not to the land that we shall deal with here.

Botanisk Museum, København, March 1907.

Il. Structure and growth of the Zostera.

If one rows along in a boat at low water in almost calm weather and looks
down upon the dark-green vegetation of the grass-wrack, one only catches sight of
the long ribbon-like leaves waving hither and thither with the motion of the water.
In summer-time the flower-bearing shoots, which will be described later, are also
sometimes visible. In order to investigate the plant more closely a few shoots
may be loosened by means of a rake, an oar or a dredge. It is then seen, that
the leaves are placed on a jointed and brittle root-stock, which has been growing
horizontally creeping in the bottom of the sea, a little below the surface of the
ground. The leaves are placed in two rows, alternately to the right and to the
left, and each leaf consists of a lower tubular part, called a sheath, which encloses
the younger part of the shoot, and the long flat, rihbon-like blade. The older leaves of
a shoot are placed on the root-stock with a space of 1—2 cm. between them, and
the places where the leaves arise give the latter a nodose appearance, as each
sheath forms a projecting ring or ridge. At the base of the sheath two tufts of
rather long, branchless, white roots develop, fastening the plant to the bottom.
Towards the end of the shoot the internodes' of the root-stock are quite short
and are only seen if one leaf after another is picked off; it is here that the shoot
is growing. At some places side-shoots are found; there is in reality a small bud
in the corner of each leaf, which is the germ of a side-shoot, yet only very few
of these will develop. From a botanical point of view the position of the buds
is rather peculiar, as they are not placed right down in the axil, i. e. just inside
the base of the sheath, but a little higher, just below the base of the next sheath.
We have no explanation of this peculiarity; it is perhaps because it would be
difficult for the small bud to find room inside the base of the sheath. The side-
shoots develop into shoots of the same kind as the mother-shoot, and as each of
the shoots only consists of some few nodes, the root-stock gradually dying away
from behind or easily broken, the side-shoots soon develop into independent bran-
ching shoots. It is thus easily understood that in this way a multitude of shoots
are formed which weave together the thick carpet of which the Zostera vegeta-
tion consists.

Grass-wrack is green all the year round and luxuriates in the warm and

6

bright summer-time; the summer leaves are longer than the winter leaves. Each
shoot has always 3 to 6, most often 4 or 5, full-grown leaves and behind these
some sheaths which have lost their blades. As shown distinctly by the present photos
(Figs.1 and 2), it is characteristic that the blades are thrown off at their base, whereas
the sheaths remain for a long time and only gradually decay, leaving nothing
but the strings as loose fibres.
The largest quantity of leaves
is thrown off during the autumn
in September—October, when
the autumnal gales set in cau-
sing a rough sea; and as the
summerleaves are besides the
longest, it is evident, that the
autumn gives the greatest mass
of loose leaves. It is also a
well-known phenomenon that in
the autumn loose leaves of eel-
grass as also whole shoots are
found floating about in the sea
in quantities. This large drift
which is further increased by
the seine-fisheries, is partly
washed ashore, making large
mounds (»Eve« or »Erve«) along
the beach, and partly sinks to
the bottom, where extensive
accumulations of »dead-weed«
are formed, especially in deep
water in holes, channels and
calm inlets. The »dead-weed«
will be a little more closely
discussed later.
The reason why the
i nb loose leaves of the eel-grass first
Eee re el se res 3 ost, ån he brat kan alen
the sheath is left; S is a side shoot. (Soft bottom, 2 fathoms, Kors: … wards sink down is, that the
NA SE SDVDS) SER RSD) fresh leaves or those just thrown
off contain so much air, that it makes them float. It is also on account of this
air, that the leaves of the growing eel-grass point upwards in the water; as the
leaves are extremely flexible, they would in the absence of air in the blade lie
flat along the bottom of the sea, which would be quite purposeless in all respects.
If a leaf is held up to the light and investigated more closely, it is seen that inside
it some fine strings run lengthways in the blade; their number varies from 3 to 7,
but the number of strings in one leaf is the samein the whole of its length. The
purpose of these strings, which are connected with one another by some still finer
cross-fibres, is to act as conductors for the nutriment of the leaf. Between the

-]

longitudinal strings some stripes more or less broken and often like a string of
pearls are visible; against the light they are dark, but with the light falling upon
them they are whitish or light green, being covered by the outer green skin of
the leaf; these are rather long and very narrow cavities filled with air. It is
easily ascertained that they contain air by holding a bit of leaf in water and
presssing it between two
fingers; air bubblesrise from it.

In order to learn how
many leaves are produced by
the Zostera in the course of
a year, I have made a great
many measurements. It is
not easy to determine how
much the plant grows and
how many leaves it develops,
as, apart from the length,
the leaves are alike all the
year round and at any rate
apparently have no resting
period like our land plants,
and further, as it is impos-
sible to mark the root-stock
of a certain plant on its na-
tural place at the bottom of
the sea and inspect it in
order to follow its growth.
Nor has the eel-grass like
our trees any fixed rule of
branching which tells us that
normally the shoot is branch-
less the first year and gets
branched the next, so that
the age of a branch may be EL EE
determined.

5 Fig. 2. 4, Leaf-bearing shoot; & shows the place where the blade has
I have tried to clear fallen off. B, Flower-bearing shoot from the same place. (Sand bottom,
up these questions bv inve- Smaaland waters, Omø Bank, ca. 2 fms., 7. August 1901).

stigating a certain number
of shoots collected at a certain place and depth once a month throughout a
whole year.

I am indebted to Dr. C. G. Joh. Petersen for kindly enabling this inves-
tigation to be carried out, as it would have been quite impossible for me perso-
nally to have collected the material month by month. In 1901 the Biological
Station had its head-quarters at Nyborg, and I chose for the investigation a place
in Nyborg Fjord off Holckenhavn where I found a rich growth of grass-wrack
from 3!/, fms. to inshore (//,—!/, fms.). At a depth of 3//,—2 fms. the bottom
was soft, whereas it was hard at 1//,—!/, fms., the grass-wrack being accordingly

9

as will be further mentioned later — long and broad-leaved on the soft bottom,
narrow and short on the hard bottom. When I chose the place, I decided to
colleet the material at a depth of 3//,, 21/,, 11/, and 1/, fms., which was also
carried out by myself as well as by the Biological Station's fisherman, who accom-
panied me on my first expedition in August 1901 and received exact information
as to the place and depth. He then undertook to collect the grass-wrack until
the Biological Station's steamer left Nyborg in the beginning of March 1902.
Then a fisherman at Nyborg was instructed by the Biological Station's fisherman
to collect the eel-grass, which he did until he was able to "complete the collection

Table lå.
The channel off Holckenhavn.
Hard bottom, 1—1% fms.

Date The length of the longest leaf incl. sheath in Aver- Breadth of the leaf
1901—02. cm. (Each number corresponds to one plant.) age. in mm.
9—VIIL. | 30 50 43 5045 28 50 50/45 283033 55 41 25—3,5
18—IX. 33 58 43 75 60 75 77 65 60 58 78 62 2,5—3,5

15—X. 80 70 70 55 63 65 67

14—XT. SEE TD 70) 91 3,0—3,5
15—XIL 58 58 60 53 57 25—2,8
15—I. 58 58 55 bill 3,0—4,0
15—IL 73 85 60 73 3,0—4.0
19—II11. 65 60 68 64 2,5—3,0
17—IV 63 60 58 65 61 3,0—3,5
15—V. 37 31 36 64 66 50 43 49 3,0—45
15—VI. 41 48 38 42 3,0—4,0
15—VII. (6813163 cell 3,0—3,5
15—VIIL. | 75 62 74 70 3,5

in August. The frequent change of collectors has unfortunately caused some un-
certainty and heterogeneity in the material and I have therefore decided to reduce
the 4 divisions to 2 according to the nature of the bottom.

The present tables (Tables I—IV), the result of this investigation, contain
information which will facilitate the solution of the questions stated above.

") As the depth on our charts is nearly always given in fathoms I have for practical
reasons been obliged to use this unity for the investigation; in the following table I give the
equivalents of fathoms in meters:

NE RO GEmeters: 31 fm. = 6,6 meters.
11 SORAKES ES IS KEE 4 — == 78 —
IE == 9 8 = 41 rr 80 —=

2 —— == 43,8 — FSR 9 4 —
REAR == - bg — == 104 =

3 == bb RES RES

9

If we are to make any use of these measurements, it is necessary that
all the Zostera shoots at a certain place should be almost the same in size and
length of the leaves. On looking down upon the wavy field of grass-wrack in the
water, this supposition should seemingly be easy to fulfil; grass-wrack is very
much like a corn field in which the plants are generally almost equal in size,
and though the variations are large the numbers in the tables show that the
hypothesis is to some extent correct. It seems however that in this respect there
is some difference in the Zostera vegetation when growing in low water and on
hard bottom or in deep water and on soft bottom.

Table Il.
Channel off Holckenhavn.
Soft bottom, 21—31 fathoms.

Date The length of the longest leaf incl. sheath in cm. |Aver- | Breadth of the leaf
1901—02. (Each number corresponds to one plant). age. in mm.
9—VIII. | 120 105 140 130 145 100 130 185 230 200 208 225 | 160 5,0—7,5

18—IX. 105 113 125 130 125 170 155 200 180 223 185 163

198 165 150 159 5,0—8,0
15—X. 98 110 165 198 175 163 152
14—XI. 105 105 93 85 153 160 153 122 4,5—6,5
15—X1I 75 105 90 105 130 95 100 6,0—6,5
151. 88 100 85 123 125 148 112 5,0—6,5
15—1I1. 130793"8565' 73 89 4,5 —6,0
19—IIT. 105 100 90 80 100 95 4,5—6,0
17—IV. 113 118 138 113 80 112 45—6,0
15—V. 82 60 64 75 70 435-570
15—VI. 104 86 170 152 130 117 138 128 5,5—7,0
15—VII. 215 125 160 185 195 190 178 6,5—8,0
15—VIL. | 155 215 240 170 190 170 245 230 230 205 6,5—8,0

In Table I the length of the longest leaf of some shoots from low water
and hard bottom is given im.cm. together with the breadth of the leaf in mm.
The number of specimens (shoots) measured is rather variable and generally too
small, but unfortunately for practical reasons no more shoots were at my disposal,
partly because the collecting work had to be fairly easy to undertake, partly be-
cause many of the leaves of the specimens sent were defective (the tips were
broken) rendering it impossible to decide which had been the longest.

The, measurements from August and September are however so numerous,
that they show the extent of the variations, from which one can judge of the
value of tbe average. It appears from these that the variations are so consider-
able, that the average must be used with caution and only as an approximate
number. The Table further shows that neither the numbers of the individual
measurements nor the averages vary in any certain direction, they rise and fall
quite casually and after having studied the Table we can only say that the eel-
grass in low water and on hard bottom seems rather invariable in the
course of the year as regards the length of leaves. The breadth of the
leaves only shows slight variations, such as from 2,5 to 45 mm., and is also unin-
fluenced by the time of year.

10
. ;
Turning to Table II, measurements of the longest leaf of plants which
have been growing on soft bottom in deep water, we come to quite different
results. It is first observed that the leaves are much longer here than on hard
bottom and in low water, 60—245 cm. as compared with 28—110 cm., which is
more than twice as long; the breadth is likewise much greater (4,5—8,0 mm. as
compared with 2,5—4,5 mm.). The variations in the measurements for a single

Table Ill.
Channel off Holckenhavn.
Hard bottom, +—14 fathoms.

The length of all the leaves of some plants (in cm.);
each line corresponds to one plant.

1901—02 Outermost — Innermost leaf.
18—IX. 68168278835558535
15—X. 80 78 65 43 20

65 70 65 50 40 18
70 65 55 43 15

14—XTI. 93 70 63 20
110 85 80 45 5
70 55 55 15
15--XIL 55 58 40 18
58 52 45 23
50 60 48 25
53 48 48 40 25

15—1. 58 58 48 28 13
58 53 45 28 10
55 53 48 33 13

15—10. 6å 73 60 40 18
85 70 40 13
od 60 40 20

19—1I1. 65 50 38 23 8
60 50 — 20 8
68 48 :

(2)
igE= VE 63 40 2
60 40 3
58 45 3
65 48 33 18 5

15=V. 37 32 30 28 22 8
28 26 29 31 20 6
1
6

— 36 28 28 28

66 66 66 60 38
50 47 45 43 39 20
43 39 35 — 24 14

15—VI. 30 29 34 41 38 22

29 37 48 47 25

24 29 38 34 18
15—VI. 36 48 60 67 76 62 25
— — 53 64 73 65 28
40 50 57 63 63 50 20
15—VIIL. 68 75 75 54 15

58 62 61 52 22

57 68 74 67 3

ii

date are also large here, so that the averages are very uncertain, but on Table II
they vary in a definite direction: they are highest in summer, lowest in spring and
winter. From this we may conclude that the leaves are longest in the warm
summer time, July—September, when they are generally upwards of 150 cm. long.
From September they decrease in length, i. e. the longest leaves are thrown off
and the new ones grown are not so long; in winter they are only ca. 100 cm.
long. In spring they are also comparatively short, though the unusually low num-
bers from the 1låth of May are accidental, and the longer leaves develop only in
June; lastly, im mid-summer (July—August) the leaves reach their maximum
length. We may therefore say that the leaves of the Zostera vegetation
in deep water and on soft bottom are much longer in summer than in
winter and spring. The Table further shows that with increasing length of the
leaves in summer follows their greater breadth.

The Tables II and IV come from the same collections; they contain
measurements of the length of all the leaves of some plants, arranged so that each
line corresponds to one specimen; the first number (to the left) gives the length
of the outermost leaf, the next that of the following leaf etc. to lastly, that of the
innermost leaf not yet full grown. Each month 3—7 specimens were measured
and the number which marks the longest leaf of each specimen is accentuated; a
dash instead of number means that the leaf in question was defective on account
of the absence of the tip.

Here both tables agree and show the same, though Table IV most clearly,
namely, that the outermost, i. e. the oldest leaf, is the longest throughout
the autumn and winter, whereas in mid-summer the second, the third,
fourth or even the fifth outermost leaf is the longest; this is in good
accordance with what we have learnt from Table II.

Table IV.
Channel off Holckenhavn.

Soft bottom, 21—34 fathoms.

The length of all the leaves of some plants (in cm.);
each line corresponds to one plant.

1901—02 Outermost — innermost leaf.

ære — 200 143 108 80 23
185 155 108 80 48 5
155 120 80 65 40 10
165 150 95 78 50 15

15—X. — 198 143 135 95 25

163 138 110 115 60 18

— 175 130 133 98 25

165 130 105 108 60 13

105 — 85 75 20

105 93 88 45

93 70 45 33 10

85 58 65 45 25

153 123 100 60 20

160 120 90 9) 68 33

153 113 68 43 25

14-XE

1901—02

Qutermost — innermost leaf.

7 ———

15—X1L

15—11.

19—I1IT.

17—I1V.

f'o-=V

15—VI.

io VÆR

UDE VE

75 75 60 60 50 40 15
105 98 88 73 45 23
90 80 78 68 45

— 105 98 90 58 25
130 115 105 95 68 28
— 95 — 83 53 23

88 88 88 70 55 23

98 98 100 60 28

85 73 — 50 35 15

123 95 98 98 75 40 10
125 113 105 105 83 35 3
148 123 128 — 853 33 3

130 118 100 65 38 15
93 80 50 30 8
85 78 55 38 5

63 65 60 58 48 23
73 65 bd 45 28 10

105 — 50 28 10

100 — 68 35 13

90 78 65 45 25

100 — 70 58 28 13

80 — 73 70 50 23

113 98 65 43 23 8

118 100 — 45 23 8

138 — 93 58 30 12

113 90 — 75 43 23

78 78 80 65 35 18

77 80 82 71 42

— 53 60 60 42 12

49 42 40 52 64 56 37

53 — — 75 75 60 32

76 71 85 93 104 90 52
— 583 64 79 86 77 40

— 97 127 160 170 145 90
113 — 127 140 152 130 85
92 95 — 124 130 106 54
72 84 94 107 117 103 64
70 80 100 — 138 94 44

— 115 132 185 215 190 110
87 106 116 125 — 45

103 126 — 160 135 55

113 — 185 — 175 108

— 160 195 60 72

— — 190 165 68

124 137 155 147 107 32
151 195 215 200 137 35
170 215 240 210 155 43
16601707 230
155 172 — 190 170 80
165 170 170 135 60
205 220 245 230 160 48
Te 230210 1S2S
180 220 — 230 220 107

co

13

The essential points are best seen in Table IV: in September and October the
long summer leaves are the outermost leaves; in November the outermost and
longest leaf is considerably shorter; at this time the summer leaves have been
thrown off. This is the state of the plant till in the month of April; but in May
it begins to be altered, as can be seen nicely and regularly im June especially,
when in all 7 plants measured the fifth leaf is the longest; then the longest leaf
moves further out, yet even in August it is the second or third outermost and
not until September is it the very outermost. dr

The question is now, whether by means of these tables it is possible to
draw a conclusion as to the number of leaves produced by the grass-wrack in the
course of a year, and in this respect the answer is not very favourable. It must
be remembered that only the outer leaves are full-grown, as is most clearly seen
when measured, only these having long sheaths. The fact is that the sheath is
the part of the leaf which is latest in completing is growth. Taking e. g. the
5 specimens whose lengths of leaves have been entered on February 1åth 1902, we
have the following measurements:

Length of leaves with sheaths. Length of corresponding sheaths.
130 118 100 65 38 15 30 28 20 13 0") 0
93 80 50 30 8 2015800
85 78 55 38 5 20 15 10 0 0
63 65 60 58 48 23 18 18 18 13 3 0
73 65 då 45 28 10 19 15. 12 7 00

Similarly also on June 1åth 1902:

Length of leaves with sheaths. Length of corresponding sheaths
76 71 85 93 104 90 52 21222025 25 EST 0
— 53 64 79 86 77 40 —1619221810
— 97 127 160 170 145 90 25 29 33 44 25 2 0

To judge from the length of the sheath in the first example, scarcely more
than 2—3 leaves have finished their growth in length, in the last example 4 or
perhaps 5 have. On this is founded the opinion above stated, that each shoot has
at a certain time only 3—6, most often 4—5, full-grown leaves.

Ås it is thus impossible to make sure that the leaves on the inner side of
the longest leaf are full-grown, one cannot draw any conclusion as to their length
being final. I do not think therefore that by means of the tables it is possible to
decide the exact yearly number of leaves on one shoot. Taking for granted that
the growth during the winter halfyear (November—April) is extremely small, I
venture however to express the supposition that the grass-wrack yearly
produces 4 to 6 new leaves on each shoot. It is seen that the place of the
longest leaf on the table changes according to the time of the year and it seems
to me that this fact lends some countenance to the supposition. The production
of leaves is of course rather variable according to the nature of the place, for
under favourable conditions the growth is more considerable and possibly more
leaves are developed than under bad conditions.

The place near Nyborg gives an example of the Zostera vegetation in fjords,
where we find the most perfect development of this plant. From the following

') The sheath is yet quite undeveloped.

14

Table V it appears that at the end of July and the beginning of August 1901 the
longest leaf was not generally the outermost leaf throughout Danish waters, thus
justifying the generalization of the results we have come to from the measurements
of the Nyborg material concerning the growth of the grass-wrack.

Table V.
Length of Zostera leaves from different Danish waters.

The length of all the leaves is given in cm; each line corresponds to one plant.

Place, depth, nature of bottom and date. Measurements in cm.

Livø Bredning, 3'/,—3 fm. Soft bottom.

271 01.

100 — 110 100 50 3
— — 90 93 75 20

| — 58 73 75 70 25
| 60 78 83 83 68 20
50 65 78 — 48 5
Nissum Bredning, E of Stenodden. 2'!'/, fm. Hard 105 — — 160 165 — 20
bottom e8/ — 100 — 108 110 — 40

SS not 140 — 225 233 210 180 115 33

Nissum Bredning, Hvidbjærg church in E. by N.
27/, fm. Sand bottom.

29
17

Livø Bredning. E. of Livø Teglværk.

Soft bottom. 1. — — 213 203 193 148 65 5
— — 215 215 190 160 100 25
165 200 208 — 188 135 70 8
Kattegat. Treaa Mølle in S. 4"/, fm. Sand bottom. 50 — 78 83 83 60 60
TE — 50 65 78 85 70 30
Kattegat. A little N. of Mark on Østre Flak, South 20 28 35 45 48 35 3
of Læsø. 6—4!/, fm. Hard bottom. ”/,. 28 35 43 5å 65 50 13
33 40 55 63 53 18

Kattegat. Muldbjærge in W.S.W. Jydske Aas in 50 78 93 105 100 65 10
NAWEE SEN SRA TE m E San di bottomseEs |: 65 85 103 93 60 8
43 53 7d 83 65 18
Kattegat. Als church in W.S.W. 9'/, miles. 5!/, fm. bå 63 70 73 75 55 20
Sand bottom. ”. 50 65 78 85 80 60 28
55 65 70 70 65 48 15
60 65 68 65 53 30 3
Kattegat. Middle of Gjerrild Bugt. 4 fm. Sand 35 45 60 70 75 45 8
bottom) 35 45 43 60 60 40 10
40 53 — 85 93 63 18
North coast of Zealand. Off Hornbæk. 4 fm. Hard — 63 80 100 115 65
bottom ”/,. 43 68 — 123 123 55
78 83 100 110 93 43
North coast of Zealand. Nekselø Bay. 3!/, fm. Soft 85 110 — 143 130 60

113 115 120 115 73
— 108 140 150 130 53

23/ FR

bottom.

87 — 120 130 125 75
Samsø Belt. Off Udsager Hage. 5—4"/, fm. Hard 30 43 55 68 75 53 15
bottom. ”/,. 30 35 38 40 35 13
45 58 — 70 60 25
Samsø Belt. North of Ballen. 5!/, fm. Stony 38 65 93 105 113 70 10
bottom. "/; 35 — — 118 135 125 60
43 73 — 118 123 70
Langelands Belt. Off Hou. 4'/,—2 fm. Hard 35 50 78 105 135 133 58
bottom. ”/,. — 73 93 108 125 103 30

75 85 93 50
) 70 78 63 13
95 105 93 25
93 100 73 18

15

Place, depth, nature of bottom and date. Measurements in cm.

Smaaland Waters. Vene Grunden. 4 fm. Hard 60 70 78 83 68 40

bottom "/,. 70 70 75 73 73 50
53 55 63 73 65 30

Smaaland Waters. Off Knudsby. 3 fm. Hard bot- — 55 53 55 60 45
tom se — 58 60 60 68 45

— 68 73, 70 80 70 18

5d 65 68 75 65 15

— 63 60 65 58 15

Bøgestrøm. N. of Nordre Knigge. 1/, fm. Soft — — 95 98 90 48
bottom. "/,. — 105 — 83 55 13

93 — 95 88 43

70 75 73 70 33

The Zostera propagates partly by branching as above mentioned, the branches
breaking loose and forming independent shoots, and partly by seed. We are thus
led into a discussion of the flower-bearing shoots of the plant. The fact is that
the grass-wrack is a real phanerogamous plant related to some of our land plants
and freshwater weeds, and has nothing to do with the numerous different kinds of
sea-weed (Fucus, etc.), which otherwise form the vegetation of Danish waters. Besides
the eel-grass, there is in more brackish parts of Danish waters some few other
marine phanerogamous plants which will be briefly mentioned later in this paper;
but none of them are of any importance to the biology of the sea.

The flower-bearing shoots of the grass-wrack (Figs. 2 and 3) are put forth
in early summer; the first faint indications of them are seen in Aprili—May, but
only later im the summer do they reach their full development. It is the tip of
the creeping root-stock which develops into a flower-bearing shoot: the inter-nodes
suddenly grow longer and grow upwards; no roots develop at the nodes; the almost
terete stem becomes flattened and the leaves become shorter. Then an ample
ramification takes place on two sides, giving the whole flower-bearing shoot a fan-
like appearance. Each branch ends in an inflorescence of a peculiar shape.
It looks as if the whole shoot only consisted of leaves on whose inner
side the middle part is a little swollen. On further investigation a longitudinal
fold is visible on this part, within which lies a flat body 4—6 cm. long, on the
one surface of which the small flowers are placed. This body is the uppermost
part of the shoot and the fissured organ by which it is enclosed is the sheath of the
uppermost developed leaf; its blade apparently forms the tip of the shoot. The
structure of the flowers of which this remarkable inflorescence is composed is
very simple; they consist of two rows: alternately anthers (two oblong-pyriform
bodies) and pistils (a club-shaped body, which is fastened at the side and at the
pointed end split into two long, filiform appendices, the stigmas). The anthers are
the male organs; they contain an enormous quantity of very fine threads (12 mm.
long by 0,006 mm. broad)!) which are freed by the bursting of the anthers and float
about in the water. Should they meet the filiform stigmas of the pistils they

”) 0. Rosenberg: Ueber die Pollenbildung von Zostera, Upsala 1901, S. 16.
3

16

fasten on them, and a fertilisation of the female organ, the ovule which is enclosed
in the pistil, is effected. The fertilisation is thus brought about by means of the
water, a peculiarity only very seldom seen in the phanerogamous plants. In con-
formity with this the pollen of the anthers is shaped like fine threads, whereas
in the planerogamous plants it generally consists of small round grains. The
anthers of one inflorescence of the Zostera cannot fertilize the pistils of the same
inflorescence, as the latter develop first and the time within which they are receptive
of fertilisation is over when the anthers open; it is thus evident that fertilisation must
be effected by pollen from other inflorescences, one stage ahead in development.
Fertilisation having been effected, the pistil gradually swells and inside it one single
seed develops, which when ripe is ca. 3 mm. by 1,5 mm., cylindrical in shape with
rounded ends and of a gray-brown or yellow-brown tinge; the shell of the seed has
faint longitudinal stripes. When the seed is ripe the pericarp opens by a longitudinal
fissure, so that the seed may slip out; the pericarp itself is rather thin, juicy
and soft.

The freed seeds sink to the bottom of the water (or they are perhaps
sometimes swallowed by fishes, through the alimentary tract of which they pass
undigested). The current carries them away to other places where they form new
growths of eel-grass. The germination probably takes place in the following spring;
I have at any rate found seedlings in July—August which were probably not a
year old, as they had not yet put forth any visible creeping shoot. These young
seedlings are however only very seldom to be seen, mostly due to the fact that
they do not generally come loose together with the larger shoots of the eel-grass
when these are torn from the bottom, and a direct investigation of the place
where the Zostera is growing, for the purpose of ascertaining the number of the
seedlings, is rather difficult to effect.

The different vegetations of Zostera show a great difference in regard to the
number of the flower-bearing shoots; at some places one finds them in quantities,
at other places one cannot find a single specimen for long distances. In all
probability the number varies also year by year.

The flowering begins in June and is continued during the summer, the
flower-bearing shoots constantly producing new inflorescences. On investigating
such a shoot in mid-summer inflorescences in all stages of development are there-
fore found. I have found the first ripe fruits in the first week of August or there-
abouts. The inflorescences which develop last seldom or never have ripe fruit,
partly because the fecundation probably fails and partly because the whole flower-
bearing shoot is thrown off or broken later in the autumn, at the time when the
large quantity of leaves is thrown off. It is thus seen that the flower-bearing
shoots only remain in existence for some months (4—5).

I am not able to state what is the cause of the abundance of flowers; I
have come across good fruit-bearing shoots in calm fjords on soft bottom as well
as in the open Kattegat on hard bottom; nor does the depth seem to be of any
consequence.

III. The outer conditions for the growth of the Zostera.

The grass-wrack is a pronounced aquatic plant which can only grow when
surrounded by water and withers if exposed to the air for any length of time; thus,
its growth ceases at the lowest water mark. The presence of water is not sufficient
however, the water must also be saline. We can best notice how the fresh
water hinders the growth of the Zostera at the mouth of larger streams, for example,
the outlet of the river Gudenaa in Randers Fjord, where the eel-grass is only
to be found a short way up beyond Udbyhøj. The ability of the ecl-grass to
grow in salt water is a peculiarity it has in common with only a few other
flowering plants and no other northern flowering plant has it to such a pronounced
extent. The Zostera nana Roth, which occurs frequently on our coasts as low,
small growths in quite shallow water, comes close to the common eel-grass in this
regard. The few other marine flowering plants which grow in our waters live in
more brackish water.

The eel-grass also grows on those of our coasts where the salinity of the
water is highest (about 3.3 per cent.), namely, along the west coast of Jutland and
on the inner side of the north point of Jutland; it is not common nor does
it grow extensively at these places, but this is due to other factors than the salinity.
The latter decreases up through the Kattegat and the Belts, and on the east coast
of Falster and in Faxe Bay it is as low as 1.0 per cent., but we still find the
eel-grass there. Its distribution extends still further up the Baltic, where its most
northern occurrence seems to be in the Åland Sea (according to R. Sernander,
Botaniska Notiser, Lund, 1901, p. 276). Here the salinity is not more than about
0.6 per cent.

We see from this that the grass-wrack certainly requires salt water, but
we find also that it is not very particular about the degree of salinity. Å salinity
of 1 to 3 per cent. may be considered the most advantageous for its growth, and
as it is just between these limits that the salinity in our Danish Seas varies, we
cannot wonder that the eel-grass is at home with us.

A fairly sheltered locality is another condition for the success of the
eel-grass. It cannot grow on an open coast where the waves beat heavily and the
motion is felt a good way down in the water; the bottom at such places is either
too unsteady for the roots to fasten themselves on, or too stony with consequently

18

no opportunity for growth for our plant, which does not possess the ability of the
algæ to fix themselves on stony ground. Along the open west coast of Jutland
the bottom is therefore nearly devoid of Zostera; but wherever there is some shelter
we immediately find the grass wrack again, e. g. between Fanø and the mainland
as well as beyond the political boundaries of Denmark along the island-rich west
coast of Schleswig. We may however seek for places with richer growths in our
own waters within the Skaw, and we find these already in Aalbæk Bay and further
on wherever the conditions are suitable for the plant.

We come now to a third condition for the growth of the grass-wrack, that is,
the light. All green plants (also the blue-green, the brown and the red) require
light to be able to thrive. The light is as a matter of fact a necessary source of
power to them, because by its means and hy means of their own green pigment
they produce new stuffs for their growth from the carbonic acid. of the air or water.
In this way they develop the organic substances from the inorganice and this
wonderful ability is the fundamental basis for all life on earth. The difference
between the distribution of plant life on the land and in the sea arises from the
dependence of the plants on light. While the land is covered with plants, the
low-lying parts as well as the high, except where perpetual snow covers the ground
or the scarcity of water hinders the growth of the plants, all plant life in the sea
(save that of the bacteria) ceases at the depth of about 200 meters. The sea-bed
lying deeper than this is only inhabited by animals and bacteria; the reason for
this is that the light can only penetrate downwards to a certain depth and below
this an impenetrable darkness reigns, only lighted up now and then by the flash
from various marine animals with light-producing organs. The different components
of white light penetrate to different degrees down into the water, the amount of
refraction and absorption being different; the green, blue and ultrapurple compo-
nents go furthest down and in connection with this we find that the red-coloured
plants, which just absorb these components, are to be found deepest down. On
the other hand, the brown and especially the green plants cannot grow so deep
down, from which we may conclude that the eel-grass cannot grow at any great
depth. The more definite question: how far down can it grow, cannot be answered
from this side, it must be answered from direct investigations. The result of my
observations in Danish waters is that the eel-grass goes much deeper down at
some places than at others, and that this is connected with the clearness (trans-
parency) of the water. At the time of year, in summer, when I made my observa-
tions, the water has as a rule its lowest transparency, as it then contains the most
plankton. But this rule does not hold in all cases, and besides, other factors are
present here; thus, the water near the coast is always less transparent during or
after a storm or fall of rain than it is on calm days (comp. the observation from
Fæmø Sound on next page). To obtain however some standard for the transparency
of the water, a standard which, if not absolute, could yet give comparable data, I
employed a disc painted white, 20 by 15 cm. It was let down into the water fixed
to the lead-line. It proved that under fairly quiet conditions the disc could be
seen nearly at the same depth as that to which the Zostera reaches, as the
following observations show:

Lim Fjord, east of Livø brickfield (%/, 1901). Soft ground. No Zostera

19

to be found at a depth of 3 fathoms, but at 2'/,—2 fathoms an abundance of long
broad-leaved Zostera. The white disc could be seen faintly at a depth of
2 fathoms.

Kattegat. Als Church in W.S.W. 91/, miles (/,). Pure sand bottom.
At 51/, fathoms a small quantity of narrow-leaved Zostera. The disc could be
seen to a little møre than 5 fathoms.

Langeland Belt. Off Hou (?/;). Firm (stony) bottom. At 5 fathoms
scattered Zostera, from 4"/, fathoms and inwards plenty of Zostera. The dise could
be seen at ca. 5 fathoms.

Fæmø Sound (?/3). Soft ground. At 4 fathoms no Zostera. At 3—2
fathoms plenty of Zostera. The disc could only be seen at ca. 1 fathom owing to
rough sea.

Guldborgsund. Flinthorn Reef in N.N.E. (;/;.) Soft ground. At 3%,
fathoms no Zostera. From 3 fathoms plenty of Zostera. The white dise could
only be seen scarcely to 3 fathoms although the water seemed to be clean and
transparent.

Baltic. Off Falster. Viggerløse Church in N.W. to W.:/,W. 57/, miles (5/8).
Pure sand bottom at 6 fathoms. The white disc could be seen af 4 fathoms (in the
neighbourhood at Tromnæs the Zostera grows down to a depth of almost 5!/, fathoms).

Baltic. In the centre of Faxe Bay ('/;). Pure sand bottom at 6 fathoms.
The white disc to be seen at 4//, fathoms. (Off Faxe the Zostera grows down to
quite 4 fathoms).

(For the rest, see the observation material (Chap. IX) at the end of the paper.)

We may conclude from these observations that the grass wrack grows as
far down in the water as all the components of the sunlight reach; they are a little
weakened in quantity but unchanged in quality.

As a general rule, the grass-wrack goes deepest down in the open waters,
where the water is most transparent, and to a less depth in the muddy waters of
the fjords. The actual data are stated in the observation material at the end of
the paper (p. 47); but the following may be taken as the general results for our
different waters:

In the Lim Fjord the limit is about .......... 3 fathoms (ca. 5.5 m.),
-… — Kattegat (Aalborg Bay) nearly ......... ORE (cast ore);
- — Great Belt and Langeland Belt about... 5%, — (ca. 10.… -),
sam bitte: Belts about sa SER SES EEN 41, — (ca. 85 -),
Waters between Samsø and Jutland about ..... i) — (CARKROSED)
Smaaland Waters (open part) about........... AT (Ca: 8.505),
The Sound and north coast of Zealand about .. 4//,—5 fathoms (ca. 8.:—9.5 m.),
Bale (HaxerBay) abo ss Rd. SA fade ER 4 fathoms (ca. 7.5 m.),
Baliet (of als ber) ab one eee tere DRE (case

The smaller sounds and bays are very similar to the Lim Fjord, so that
the depth limit is about 3 fathoms (ca. 5.5 m.), e. g. Guldborgsund and Fæmø
Sound; in Bøgestrøm even as low as 2 fathoms.

Thus the depth limit varies between nearly 6 fathoms (ca. 11 m.) in the
most transparent water and 2—3 fathoms (ca. 4—5.5 m.) in the less transparent
though still flowing water of the fjords. The extreme limit, ca. 6 fathoms, is a

20

little lower than that earlier given for our waters. Thus, C. G. Joh. Petersen
gives for the Kattegat 6—7 fathoms") and for the Little Belt 4—5 even 6 fathoms?).
J. Reinke?) states that he found grass-wrack in the western part of the Baltic,
»vereinzelt bis zu 17 Meter Tiefe« on sand bottom, and E. Warming (Dansk
Plantevækst I, Strandvegetation, p. 185) says that »even as much as 10—14 m. is
given for the Kattegat and the Little Belt«. I think however, I may suggest that
these reports rest upon the inaccuracy of the soundings; most of them come from
observations made for zoological or fisheries purposes, and for these one fathom
more or less is quite immaterial. In the Kattegat (the place where all consider
that the grass-wrack goes deepest down in our waters) I have made particularly
careful observations to fix the limits and have come to the conclusion, that the
6 fathom curve is never reached nor surpassed by growing Zostera; see
for the rest the specified data later (observation material, p. 47).

We have statements from other countries that the Zostera vegetation grows
at greater depths. Thus, Karl Techet?) states for 'Trieste Golf that it grows
at a depth of 17—18 meters, and it is very probable that it grows deeper down
in the clear water of the Mediterranean than in our own less transparent waters.

J. Reinke (l. c.) remarks that the grass-wrack goes deeper down on a
sandy than on a muddy bottom and this agrees with my own experience. The
explanation is most likely simply this, that the water over sandy bottom is clearer
(more transparent) than over muddy soil, where fairly large quantities of mud
particles are always being stirred up into the water.

The nature of the bottom soil is an important factor in many regards
for the Zostera's growth. It has already been mentioned that the plant must have
loose (not rocky) soil for the roots to fix themselves on, but the varying consistency
of the loose hottom is also of importance and affects the growth and appearance
of our plant. The extreme kinds of bottom soil in which the grass-wrack grows
are on the one hand the firm sand, sometimes covered with stones and on the
other the soft, muddy bottom of the quiet bays and fjords. It is found on
both sorts of ground, but the plant we find on the firm, sandy bottom is certainly
in many ways different from what I call the Mud-Zostera. We may examine into
this a little more closely.

In the open waters where the motion of the waves is felt a good way
down, the bottom is firm and sandy to a considerable depth; there is no rest to
permit of the formation of the soft kind of soil generally called mud, which is
characterized by its abundance of organic matters (decayed pieces of plants and animals)
as well as by its fine clay particles. If we choose the Kattegat as a typical example
of an open water — and in this connection it must be counted as one, because
the occurrence of the grass-wrack depends on a certain even if but small amount

7) C. G. Joh. Petersen: Det videnskabelige Udbytte af Kanonbaaden Hauchs Togter,
1893, p. 437, and Beretning IX fra den danske Biologiske Station, 1900, p. 32.

?) C. G. Joh. Petersen, Beretning III fra den danske Biologiske Station 1893, p. 28.

3) J. Reinke, Algenflora der westlichen Ostsee deutschen Anteils, 1889, p. 12.

4) Ueber die Marine Vegetation des Triester Golfes. — Abhandl. der k, k. zool.-botan.
Gesellsch. in Wien, III, 3. 1906. p. 17.

21

of protection (see p. 17) — we find!) that the pure firm sand reaches a depth of
about 7 fathoms, after which follows a »mixed« soil, which again passes over into
the pure clay bottom (00oze) at a depth of about 20 fathoms. It is thus only the
pure sand hottom which comes into consideration for the grass-wrack, and it grows
on this in scattered places in the part of the Kattegat which is generally called
Aalborg Bay, namely, the shallow water bounded to the north by Læsø, to
the west and southwest by the east coast of Jutland (Djursland), and to the
south-east by Anholt; and it forms further an almost unbroken border along
the coast from "/,—1 fathoms depth and to a depth of 5—6 fathoms. It is more
rare in quite shallow water, possibly because the waves beat too heavily there, for
we find it immediately there is any protection or shelter. C. G. Joh. Petersen
and I. Chr. L. Levinsen (Beretning fra den danske Biologiske Station IX, 1900,
p. 32) say regarding the northern part of the Kattegat: »The Zostera is able to
take root already at a depth of 1
fathom«; the upper limit is thus
placed here at a depth of 1 fathom.

The grass-wrack found on
firm sand like this has the same
appearance, whether it grows at a
depth of 1 fathom or of nearly
6 fathoms. The leaves are com-
paratively short and narrow, the
creeping root-stock is strong, with
often rather long internodes; the
flowering shoots can be seen now
and then, although not as often as
in the bays.

The accompanying figure
is a reduced representation of the
Kattegat-Zostera and should be
compared with the figures (figs. 1
and 6) of Mud-Zostera. In the Table
of measurements (pp. 41—45) are
given the length of the leaves, the
length of the sheaths, the breadth
of the leaves and the length of the
flowering shoots. It is evident from
these that the length of the leaves
only rarely reaches 100 cm., and
the breadth varies between 3 and
5 mm.; the flowering shoots on the
other hand may reach quite 150 cm. p É i

az Fig. 3. Leaf-bearing (4) and flower-bearing (B) shoots of the

The grass-wrack on the firm KAL ar Zoner

bottom in the open Baltic has quite (Firm, sandy bottom; Østre Flak, S. of Læsø, 5 fm. 26. VIL. 01).

7) Beretning fra den danske Biologiske Station IX, 1900.

22

the same appearance, a conclusion I draw from the observations made off the east
coast of Falster (fig. 4) and in Faxe Bay (see the Table of measurements, p. 46).
The length of the leaves is here not above 83 cm. and the breadth between 3
and 4.5 mm. i

Along our coasts the grass-wrack does not form large, connected growths
neither in the open Kattegat nor in the Baltic; the situation is apparently not very
suitable and this may be due to the want of shelter and the poor soil.

Ås soon as there is a little shelter the grass-wrack appears in large quan-
tities and the single plant grows stronger in all respects. In the Table of measure-
ments (p. 42—46) we find even transitions from the narrow-leaved Kattegat-Zostera
to the broad-leaved Mud-Zostera. The Zostera in Nissum Bredning, in Samsø Belt,
along the north coast of Zealand and partly in the Smaaland Waters furnishes
examples of such intermediate stages, and we nearly always find the bottom given
as firm. It is generally a dark-coloured sand bottom soil the colour of which is
due to no small quantities of organic materials mixed with sand — in other
words, a soil where there is certainly a considerable wave-motion, but yet where
a portion of the organic particles has
been deposited and has fertilized the
sand. The measurements from Smaa-
land waters (see Table p. 45) give a
fairlv clear picture of the Zostera's rela-
tion to the kind of bottom soil; the first
two stations (1—2) were taken in Fæmø
Sound and thereabouts; the soil is here
soft and the leaves of the Zostera reach
a length of 88—138 cm. and a breadth
of 6.5—7 mm.; the other stations were
in more open water and have a more
solid soil; the length of the leaves is
here mostly below 100 cm. and the
breadth between 4.5— 6 mm. (see fig. 2).
The other conditions being very similar,
it appears from this that the different
growth of the grass-wrack is due to the
different bottom soil and the conditions
which arise from these.

We find a typical vegetation of
Mud-Zostera in Nyborg Bay and the
measurements given above (pp. 3—9) of
Zostera plants throughout a whole year
provide an excellent material for the
purpose of elucidating the appearance
of the grass-wrack, when it grows on
: the soil which suits the plant best and
from the Baltic; at = the blade 18 about ie separate from — Where it reaches its highest degree of

the sheath. ] ]
(Firm, stony ground, off Tromnæs, Falster 51/, fmn., 5. VIII 01.) aeve opment.

23

With regard to the sheltered places, it is necessary to distinguish between
plants growing in shallow and deeper water, a difference which does not exist in
open waters, and the reasou for this distinction lies in the nature of the bottom
soil. Close under the land we usually find a belt with firm bottom, mostly dark-
coloured sand, and the grass-wrack growing on this soil is much like that of the
open water; but at 1//, to 2 fathoms and outwards the soil consists of soft mud,
and here we meet the true Mud-Zostera. The grass-wrack of the shallow water is

Fig. 5. Small-leaved Zostera from shallow water at Holcken- Fig. 6... Broad-leaved Zostera (Mud-Zostera) from deeper

havn near Nyborg; at + the shedding places. water at Holckenhavn near Nyborg; at & the shedding
(Firm, sandy bottom, 1U/, fm., 9. VIII. 01.)

places.
(Soft, muddy ground, 3!/, fm., 9. VIII. 01.)

narrow-leaved and short (fig. 5); the length of the leaves varies from 30 to 100 cm.
and the breadth from 2.5 to 45 mm. (see Table I, p. 83). The true Mud-Zostera
(fig. 6) on the other hand reaches a length of ca. 100—240 cm. and a breadth of
ca. 5—8 mm. (see Table II p. 9, where for the sake of comparison we should
consider the measurements for the late summer, as the observations from other
places were made at this time of year).

In the Table of measurements (p. 44) is given a similar series of measure-

4

24

ments, made on plants from various depths in a quiet creek in Nexelø Bay on
the north coast of Zealand (Table No. 2); it is in sharp contrast to the measure-
ments from the other stations on the north coast of Zealand, for these all come
from the open water. Typical Mud-Zostera measurements are further given in the
Table for the Lim Fjord, east of Livø brickfield and off Nykjøbing Mors (Limfjord,
Nos. 7 and 9), for the waters between Samsø and Jutland (No. 1—2) and off Nysted
(Guldborgsund, Nos. 5—6). The leaves of the grass-wrack in Langeland Belt (Great
Belt and Langeland Belt, Nos. 2—4) are a little narrower but of the same length,
although the bottom soil is mostly firm here; it is however not the ordinary sand
bottom but stony with rich algal vegetation, where the fine nutritious material has
been able to settle between the stones. This exception is an excellent confirmation
of the rule that the length and breadth of the Zostera leaves, i.e. the size
of the grass-wrack, is more dependent on the nature of the bottom soil
than on the depth in which it grows, though within certain limits, since the
plant never grows large and broad-leaved in quite shallow water. K. Techet's
statement (1. c., p. 19) as to richer growth of the Zostera in Trieste Golf near the
harbour, where of course the sea bottom and the sea water are richer in organic
matters than at a further distance off, agrees well with my observations. The
Zostera plants are much like land plants in regard to the importance of the nature
of the ground, and not so much like most other marine plants, the algæ. We
usually find it stated that it is the depth, which is the most important, but this
is not quite correct as shown here. it is thus not entirely in accordance with the
facts, when P. Magnus!) states that the leaves of the grass-wrack in the Western
Baltic become larger and broader at greater depths, or when E. Warming?) says in
his »Strandvegetation«: »The size of the Zostera-leaves is dependent on the depth
etc.«; this author adds however a little further on in the same work (p. 192):
»The Zostera belt is divisible into two, a broad-leaved and a narrow-leaved kind,
connected with the depth and perhaps also with the nature of the bottom
soil, as far as this may be firmer in shallower water and less permeable
for the roots and root stocks; neither is it perhaps so rich in nutriment«.3)

1) Ber. d. Komm. zur wissensch. Unters. deutscher Meere in Kiel, 1872—73, p. 66.
?) Dansk Plantevækst. I. Strandvewgetation, 1906, p. 185.
3) I am responsible for the translation from the Danish and for the emphasis.

DØ
Ol

IV. Distribution of the Zostera in Danish waters.

The factors discussed in the foregoing for a successful growth of the
Zostera afford in themselves some basis for judging as to the extent of the
distribution of this plant in our waters. They may be summarized in the following
statements: The Zostera requires an at all events somewhat protected habitat,
and thus thrives best in our small waters; its dependence on light has the
result, that it can only grow in depths which do not exceed 6 fathoms (ca. 11
meters) and consequently one can only expect to find it as a fringe along the
coast, and out on the quite shallow parts of the Kattegat and the Smaaland
Waters. Ås it attains its best growth on pure and sand-mixed muddy bottom, we
find the richest Zostera vegetation in our fjords.

The following more detailed remarks about its distribution im our waters
may further serve to show the correctness of the statements.

Knowledge of the distribution of the Zostera im our waters is almost
entirely due to the Director of the Biological Station Dr. C. G. Joh. Petersen.
Already in the first report of the Biological Station (1891) there is a chart and a
thorough discussion of the distributed of the Zostera in Holbæk Fjord (Zealand)
and its importance to the animal life there. A similar detailed investigation like-
wise accompanied by a chart of the parts investigated is found in the third report
of the Biological Station, dealing with the Little Belt together with Fænø Sound,
Gamborg Fjord and Kolding Fjord. At almost the same time (1893) as this report
appeared »Det videnskabelige Udbytte af Kanonbaaden Hauchb's Togter«, in the
text of which (p. 437) some information is given regarding the vegetation of the
sea bottom, and the atlas contains a chart (III) of the Kattegat with data on the
occurrence of the Zostera. In the Report IX (1900) of the Biological Station some
notes are given on the distribution of the Zostera in the Northern Kattegat, and
finally Report X (1901) is accompanied by a chart of our waters, in which the
occurrence of the Zostera is compared with the position of the eel traps.

The investigation I undertook im 1901 was to supplement these data and
consisted in a rapid cruise through most of our waters.

Starting from the consideration that the vegetation, at places which offered
the Zostera practically the same conditions, would also be very similar, I tried
in the three weeks, in which the expedition lasted, to find an opportunity by

26

personal observation of procuring a survey of the conditions of the vegetation
at the most possible and varied places. A short statement of the route of »Sal-
lingsund« will show this. We began by examining the Sound from Copenhagen
and northward, then followed the north coast of Zealand, further along the
south coast of Samsø to Ashoved, from there to the north along the coast of
Jutland to Aarhus, into Kaløvig and round Sletterhage and Hasenøre, along the
coast of Djursland to Udbyhøj in Randers Fjord, and thence northward into the
Kattegat to Østre-Knold and Østre-Flak. We then went in through the Lim
Fjord to Nykøbing and further through Sallingsund to Nissum Bredning which
was pretty closely examined before we returned the same way to Hals; across the
Kattegat (with various stations) to Stavns Fjord in Samsø; along the east coast of
Samsø, and through the Great Belt on the Funen and Langeland side. After a
visit to Nakskov Fjord we proceeded north of Lolland, through Guldborgsund and
up along the east coast of Falster through Grønsund and the Bøgestrøm to
Masnedsund, through the Smaaland Waters and further south of Omø through the
Great Belt to Nyborg, where the expedition ended.

The points investigated everywhere were: 1) if there was Zostera, 2) how
far out the vegetation reached, 3) on what kind of bottom it was found, and
4) how the Zostera was developed with regard to the length and breadth of the
leaves, flowering shoots etc. A dredge formed by providing a lead with long nails,
was most often used for the investigations: but where the bottom was specially
firm it was found necessary to use a dredge with teeth (oyster dredge). ;

The results of the single dredgings and hauls are given at the end of
this paper, and there the data are also added of the occurrence of the Zostera as
given in the Journals of the Biological Station which Dr. Petersen has placed at
my disposal. I may therefore with regard to the details refer to this material
(observation material p. 47), which is arranged in groups according to the waters.
Å synoptic view of the distribution in the single waters may be given here,
illustrated by charts with respect to the Lim Fjord and the Kattegat. For the rest
I may especially refer to the above-mentioned excellent chart in Report X of the
Biological Station.

1. The west coast of Jutland. Here scarcely any investigations were
made. I am only acquainted with the Zostera vegetation from the waters between
Fanø and the mainland (at Esbjerg) and from Ho Bay. As far as known, the
Zostera is wanting all along the open coast from Horns Reef and to Skagen; it is
at all events certain that if the plant occurs anywhere on this tract, it is only at
single scattered spots.

2. The Lim Fjord (fig. 7). A coastal fringe of Zostera is found in all
the many estuaries (Brednings) and sounds of the Lim Fjord, but the vegetation
does not go deeper out than ca. 3 fathoms; at the most exposed places in Nissum
Bredning (and also elsewhere in the western Lim Fjord), for example, off the
Helligsø brickfield and the Ramstrup hills, the vegetation is poor or is wanting
here and there; Nissum Bredning is on the whole least covered, and the abun-
dance and richness of the vegetation increase towards the east, and also in the

'piofgsuaoT 'pIofjoAtys) Surupalg ØøAvT Jo opis qmos 944 uo ou ou) JO wynos Jiud gx "PIBM4SOM pus S1oq7ev uroaj p10fq tWvT 943 JO 91879

"D9J8S0S9AUT JOU S8A (p1of7 æg

"sun won g
11.497807 pvIq
D197807 liq p249405 899D)T

310N

——

Mm

GS
7,

z

1025607. må
GG

ØD
Vs

28
larger bays; thus it is very rich in Venø Bay and in the part from Løgstør to
Aalborg.

At most of the places in the Lim Fjord the Zostera is long and broad-
leaved, which agrees with the generally rich (mud-mixed) bottom, and which is
further supported by the fact that the Zostera in Nissum Bredning, where the
bottom is sandier and firmer, is shorter and narrower leaved.

3. Kattegat (fig. 8). Along the east coast of Jutland from Skagen to
Mols (Hasenøre) there is a narrower or broader belt of fairly delicate and narrow-
leaved Zostera out to a depth of about 6 fathoms, at some places, however, little
developed and on the other hand sometimes (e. g. at Asaa and at similar pro-
tected places) replaced by a vigorous and broad-leaved one. The belt is broadest
between Hals and Djursland, that is, im Aalborg Bay; here the Zostera in small
patches reaches much further out; there is even a connection by patches from
the vegetation on the coast to the extensive Zostera meadows on the Læsø
south grounds.

In spite of its wide distribution in the Kattegat the grass-wrack is of but
small practical importance there, on account of its scattered mode of occurrence
and its feeble growth; from this however we must again except the Læsø
south grounds.

4. The waters between Jutland and Samsø including Aarhus
Bay. We have now got to more protected waters and at once find a more
abundant Zostera vegetation. In Kalø as well as in Æbeltoft Vig there is a thick
vegetation of Zostera down to a depth of 5 fathoms; but off the points the vege-
tation is as elsewhere, poor. Along the east coast of Jutland, from Aarhus and
southward to Endelave the vegetation of large and broad-leaved Zostera spreads
more and more, so that it fills, to the south, almost the whole water between
Gyllingnæs and Endelave. Here we find the first large area with Mud-Zostera,
namely between Tunø, the Svanegrund and Endelave to the east and the coast of
Jutland to the west.

5. Little Belt. Concerning the Little Belt I may refer to Dr. Petersen's
Chart in Report III of the Biological Station. The east Jutland fjords are all
greatly covered with Zostera; a poorer vegetation is found between Funen and
Æbelø and also along the coast of Baaring Vig. South of the area charted by Dr.
Petersen, the vegetation along the coast of Funen as along the coast of Schles-
wig") is rich and well developed. And in the island-rich waters south of Funen
we have one of the large areas for the occurrence of the Zostera; I have un-
fortunately but little exact information from there. I can only say that my general
impression agrees with Dr. Petersen's chart, which shows a very wide distribution
of the Zostera in these parts.

6. Odense Fjord. Copious and vigorous Zostera vegetation to 3—4
fathoms depth; especially in Midskov Bay. ;

7. Samsø Belt. There is a fairly copious vegetation in Stavns Fjord,

") According to J. Reinke's atlas (see above).

29

Places covered by

Zdstera.

Dead Zostera.

6 fathom line.

NE WW
WWW WW AN; AWU MÅ

Chart over the western part of the Kattegat.

Fig. 8.

30

but for the rest only a narrow fringe along the east coast of Samsø. It reaches
down to 5—5/, fathoms depth. The Zostera is fairly long and vigorous, but
grows scattered (mixed vegetation).

8. Great Belt and Langeland Belt. A similar vegetation as in
Samsø Belt is found along the coasts of Funen and Langeland. The Zostera is
long and vigorous, but grows scattered and mixed with a great many algæ which
are mostly fixed to small stones, found on the bottom there. Where there are
bays and fjords the occurrence of the Zostera vegetation becomes broader, as between
Funen and Romsø, in Kjerteminde Bay, between Funen and Langeland (Lunge
Bay); it is here the large vigorous Zostera with occurs. To the south we again
reach the just-mentioned extensive vegetation between the small islands south
of Funen. ;

The Zostera reaches down to a depth of 5—5!/, fathoms in the open Belt,
and to 4—4!/, fathoms in the bays.

I am hut little acquaimted with the conditions on the Zealand side, but
what I know agrees with those mentioned for the western side. Rich vegetation

is thus found e. g. in Kallundborg Fjord and Musholm Bay and in Albu Fjord.

9. The north coast of Zealand. The open north coast of Zealand
does not offer favourable conditions for Zostera, and it is also but a sparse and
scattered vegetation we find here in the narrow coastal margin to ca. 5 fathoms
depth. The Zostera is fairly delicate and narrow-leaved, and generally occurs
scattered among the algæ; the bottom is firm, sandy or stony. These are the
conditions from Refsnæs to Vrøj, round Sejerø, and from Zealand Odde to the
Sound; the Zostera is even at many places wanting altogether, especially on this
last extensive tract.

In Nexelø Bay however we find a rich and abundant vegetation on soft
bottom from 4—21/, fathoms (see p. 24).

10. Isse Fjord. Concerning Holbæk Fjord reference may be made to
Report I of the Biological Station. The widely distributed, dense vegetation of
abundant Mud-Zostera reaches out to 2—2!/, fathoms depth. Similar conditions
occur in the other bays of the Isse Fjord while the Isse Fjord itself is only covered
on a narrow strip along the coast.

11. The Sound. In the northern half of the Sound from Elsinore to
Drogden, good Zostera vegetation occurs from the coast to about 4!/, fathoms, at
many places, however, with bare spots or greatly mixed with algæ. The best
vegetation is in about 3 fathoms. The Zcstera is long and broad-leaved at most
places, as usually less vigorous close under land and at sandy places, e. g. in
Nivaa Bay and off Rungsted.

More to the south, in Køge Bay, the vegetation is of less importance.

12. The Smaaland Waters. In the waters between the south coast of
Zealand and Lolland-Falster the most widely distributed Zostera vegetation in our
waters is found. It attains its most luxuriant development in the island-rich,
shallow waters north of Lolland (Fæmø Sound, etc.), where the large vigorous

31

Mud-Zostera covers most of the sea bottom, only, however, to a depth of quite
3 fathoms.

In the more open parts of the Smaaland Waters the Zostera reaches much
deeper down, e. g. at Omø to ca. 5 fathoms and at Kirkegrund and Venegrund
to ca. 4!/, fathoms; the deeper parts are on the contrary devoid of »grass«. The
plants are here somewhat narrower in the leaves and on the whole more delicate
than amongst the small islands.

13. Guldborgsund. Through Guldborgsund runs a partly artifcially
maintained fairway, the bottom of which (the depth is 3 fathoms or more) is bare
muddy bottom; but apart from this passage, the bottom of the sound is every-
where covered by Mud-Zostera; thick and vigorous vegetations on soft bottom
from 3 å 2!/, fathoms and less; and on the dark (mud-mixed) sand of the shallow
waters more scattered, short and narrow-leaved plants, amongst which Ruppra,
Zammichellia and Potamogeton pectinatus occur as a frequent intermixture. Amongst
the plants, like moss in meadows, grow Chara and Tolypella and other algæ
(Cladophora rupestris, Furcellaria etc.).

Ås the sound is widest to the south, the tract covered becomes
greatest there.

Almost the same conditions occur in the closed water south of Nysted,
bounded towards the open Baltic by the Rødsand bhbarrier; the shallow water (to
quite 1 fathom) is however here sparsely covered, generally bare sandy bottom
with scattered Zostera patches; on the other hand from 1'!/, to 2%/, fathoms there
is soft ground with vigorous Mud-Zostera with »moss« at the bottom.

14. Grønsund, Ulvsund and the Bøgestrøm. In the whole part
between Zealand on the ove side, Møen, Falster and the small islands on the
other, and among the islands themselves, the kind of vegetation is almost as in
Guldborgsund; there is however some difference on the southern open part of
Grønsund and the Storstrøm at Masnedø as one division, and the other tract as
another, as the two mentioned sounds are less protected than the others and
consequently with less abundant Zostera vegetation. The Zostera does not
generally reach deeper than 2 fathoms, and if the bottom, on account of the
action of the waves, is firm and sandy at this depth, the Zostera vegetation will
also be small, consisting of fairly short and narrow-leaved plants in patches. At
more protected places, especially in the whole of the Bøgestrøm, the bottom is on
the other hand still soft at a depth of from 2 to almost 1 fathom and here we
find widely distributed Zostera vegetation with large and broad-leaved plants,
mixed with the other marine flowering plants and Chara. In shallower water the
bottom becomes mixed with sand in the same way as in Guldborgsund.

15. The Baltic. From the open Baltic I have only observations from
south of Rødsand (Lolland), from the south and east coast of Falster and from
Faxe Bay (Zealand); but they all agree and may certainly be regarded as applying
also to the other tract along the south coast of Lolland and Møen.

The open unprotected situation appears in the fact that the bottom is
firm to a fairly great depth, at any rate deeper than the Zostera can live. It is

)

32

either pure sand bottom or stony sand-bottom, and in the last case (commonly in
somewhat deeper water) we often find a vegetation of delicate algæ (Eectocarpus,
Polysiphonia, Rhodomela etc.) and sometimes some Characeæ (Tolypella, Chara bal-
tica). We only find the Zostera in scattered, small patches and short and narrow-
leaved; the conditions most nearly correspond with those of the Kattegat and the
north coast of Zealand, in spite of the great difference in the salinity of
the water.

The Zostera reaches down to a depth of 5"/, fathoms off the east coast of
Falster, and to ca. 4 fathoms in Faxe Bay; but the vegetation is so sparse that
it is of no practical importance. There is no difference in the Zostera plants from
the deepest places and those from shallow water.

On the open coasts of Bornholm the Zostera is not of any importance
to the fisheries; there are only here and there some small scattered patches of
short and narrow-leaved plants.

V. The Zostera vegetation as a habit for other plants and
for animals.

At certain places the grass-wrack is found quite pure, that is, not mixed
with other plants; at other places a great many other plants grow among its
shoots, as has already been mentioned previously. According to these differences
one may speak of a »pure« and a »mixed« Zostera vegetation.

Again, the pure Zostera vegetation appears under two totally different
forms. On the bare, firm and light sand in the Kattegat and elsewhere, where
the waves beat vigorously, there is a pure Zostera vegetation with rather small,
narrow-leaved shoots; it is a poor and sparse growth of no practical importance.
The leaves of the shoots are generally clean and without any covering of smaller
plants or animals.

Å second kind of Zostera vegetation with no other plants growing amongst
it appears on rich, soft muddy bottom and in protected places. Here the Zostera
attains its greatest luxuriance, and whereas in the foregoing case it was the un-
sheltered and unfavourable conditions which caused the absence of other plants,
here the vigorous and dense growth of the Zostera itself excludes intermixture.
The shoots grow as thickly as grass in a meadow, and the leaves attain a length
of 1—2 meters. The excellent conditions of life are shown also in that the leaves
are covered with a multitude of small plants and animals. In springtime the
leaves become hairy and brown, with an abundant growth of Dratoms, and later
many Ålgæ are added (Ceramium, Ectocarpus etc.). Of animals we always find the
honey-combed colonies of Bryozoa (Membranipora), single and compound Ascid-
ians (Ciona, Botryllus etc.), hydroid polyps (Gonothyrea etc.), tubiculous
worms (Spirorbis), Lamellibranchs (especially the common mussel (Mytilus),
see fig. 9) and snails (Hydrobia, Rissoa etc.). AÅ more detailed list of the animals
living on the leaves of the Zostera will be found in Report I from the Biological
Station, p. 171—176, to which reference may be made.

The »mixed« Zostera vegetation may also be of different kinds,
varying chiefly with the bottom. The bottom in our sounds with their constantly
renewed, streaming water is generally somewhat stony, but consists besides of
sand-mixed mud, that is, sand mixed to a greater or smaller degree with fine

34

particles of inorganic as well as of organic materials. A bottom like this is a
nutritive and good place for the plants and here also we find a luxurious vegeta-
tion. On the larger stones we find Fucus vesiculosus and Chorda filum in shallow
water, Fucus serratus, Lamimaria saccharina and digitata and Halidrys siliquosa in
somewhat deeper water. The
smaller algæ, chiefly the red
and brown algæ, often appear
as a thick carpet consisting
mainly of Furcellaria fastigiata,
species of Polysiphonia, Cysto-
clonium, species of Phyllophora
and Rhodomela of the red algæ,
and of the brown algæ: spe-
cies of ÆEctocarpus, Pylarella
and Desmarestia viridis. In
the thick undergrowth of all
these smaller plants we find
more or less scattered growths
of the eel-grass. Such mixed
vegetation is common in the
Little Belt, the Great Belt and
the Sound as well as in the
western parts of the Lim Fjord.
It requires for its growth oft-
renewed, somewhat salt water,
a necessity for most of the red
algæ. To distinguish it from
the other kinds of »mixed«
vegetation it may suitably be
called Red-Alga Zostera "GR
Vegetation. 8 åd
Concerning the animal A "
life which is connected with
this kind of vegetation, I have Fig. 9. HLowering shoot of cry long and broadlen ved Mud:Zestera
At b and several other places we see clumps of small mussels; at m

unfortunately but little infor- colonies of Membranipora.
mation ; it consists partly of (Soft bottom; off the east side of Livø, Lim Fjord, 2 fm.)
the above-mentioned animals,
partly of others which are more closely connected with the algæ than with the
Zostera and which follow the algæ out to slightly greater depths. In Report III
of the Biological Station, p. 29, a general summary is given of the animals which
occur in Fænø Sound on »alga-ground«, and it is almost the same as in the case
of the Red-Alga Zostera Vegetation. The animal life is here upon the whole rich
and varied.

The other kind of mixed Zostera vegetation may be called the Green-
Alga Zostera Vegetation or with a more comprehensive term the Brackish-
Water Zostera Vegetation; it appears namely 1n the least saline of our waters,

35

e. g. in Guldborgsund, Ulvstrøm and Bøgestrøm, as well as in the innermost parts
of the bays and in half-closed inlets and firths. The bottom is of soft mud or
dark, mud-mixed sand. The bottom layer is here partly formed of green algæ
(Cladophora rupestris, Chætomorpha linum, Enteromorpha, Ulva lactuca etc.), partly
of Characeæ (Chara, Tolypella and Lamprothamnus).. Amongst these, besides the
Zostera, also grow the other marine flowering plants which. will be more particularly
mentioned below: Ruppia, Zannichellia and Potamogeton pectinatus. The animal
life is rich, though not so varied as in the two above-mentioned kinds of Zostera;
the reason is amongst others that the brackish water fauna is poorer and more
uniform than that of the salt water.")

Of the various small animal forms which are fixed to or crawl over the
leaves of the Zostera, only very few live on the substance of the leaves, the chief
mass live on the microscopic plants and animals which float in the water amongst
the leaves; they are thus in reality connected with the Zostera only because it
offers them favourable conditions to procure nourishment. This is. of course also
the case with the larger animals which live amongst the Zostera; Echinoderms
(starfish (Asterias rubens) etc.), worms, Lamellibranchs and snails, also Cru-
stacea: prawns (Palæmon etc.), crabs (Carcinus moenas), Mysidæ, Isopods
(Idothea etc.) and Amphipods (Gammarus, Proto). Most of those prowl about for
their prey in the rich hunting grounds of the Zostera.

The only form of practical importance among these animals is the prawn
(Palæmon Fabricii), which is always fished for in the Zostera vegetation.

The fish fauna which lives in these places may also be briefly mentioned.
The most important food fish is the eel (Anguilla vulgaris), which is specially
connected with the Zostera vegetation during the whole of its growth (from the
time when it enters our waters as elver until it leaves us), in so far as it does
not go up into fresh water. Most of the catch of yellow eels takes place in the
Zostera vegetation by means of eel-seines or otherwise.

OF but little practical importance are such fishes as the gobies (Gobius
niger, minutus and Ruthensparri), the fifteen-spined stickleback (Spinaclua
vulgaris), the three-spined stickleback (Gasterosteus aculeatus, the viviparous
blenny (Zoarces viviparus), needle fish (Siphonostoma typhle), and the sea-
scorpions (Cottus scorpius and bubalis), all of which are stationary fish, in any case
for a great part of their life, in the Zostera vegetation. Other species of fish
come in here at certain times, e. g. the garfish (Belone acus), herring (Clupea
harengus) and lumpsucker (Cyclopterus lumpus) and others again live here when
young, e. g. the cod.

In the various Reports from the Biological Station lists are given of the
fishes which live in the different kinds of Zostera vegetation. These can be sum-
marized as follows:

1) The fishes of the pure Sand-Zostera vegetation are mentioned
in Report IX, pp. 37—40 (Northern Kattegat),

7) At the end of this paper, in the observation material, notes are here and there given
of the plants growing amongst the Zostera,

36

2) the fishes of the pure Mud-Zostera vegetation in Report I (Hol-
bæk Fjord) and IX (the harbour at Frederikshavn), i

3) the fishes of the red-alga Zostera vegetation in Report III (Fænø
Sound), and

4) the fishes of the brackish-water or green-alga Zostera veget-
ation in Report V, p. 38 (Stege) and p. 42 (Frederikssund).

Among the animals mentioned there are only two in reality which form
the object of any extensive fishery, namely, the eel and the prawn, and it might
from that be concluded that the Zostera was not of special benefit to our fisherieg,
and even, since it at times stops up the fixed nets and prevents the setting of
gill-nets and the like"), that it was an evil; but this is certainly an error; I can
fully agree with Dr. C. G. Joh. Petersen's sentence quoted as motto for this
paper. The rich Zostera vegetation in our waters is one of the prin-
cipal supports of our fisheries, as it must he considered a most im-
portant breeding ground for the nourishment of our food-fishes.

7) Fiskeriberetningen for 1899—1900, p. 178 and 1900—1901, p. 149.

37

VI. Dead Weed.

It has already been mentioned (p. 6) that the cast-off leaves of the Zostera
and the shoots loosened in various ways float about in the water in larger or
smaller clusters, until they are either thrown up on the beach or sink to the
bottom. The deposition occurs quite by degrees and the sinking masses are often
carried a long distance by the currents before they settle. A necessary condition
for the settling of the masses of dead weed is, that they should be carried out
into depths and places where there are no currents. The dead weed may then
be collected into enormous quantities so that it covers the sea-bottom for con-
siderable distances with a thick layer of entangled masses. It is owing to the
Zostera's power of resistance to putrefaction that the accumulations can become so
enormous; it is quite different with the sea-weeds (algæ) which very quickly
crumble and decay. The dead weed is of no inconsiderable importance to our
waters, as it impedes fishing with seines at several places and as the bottom,
where the dead weed forms a thick cover, is not a good place for the animals
living in the upper layers and on the surface of the sea-bottom, many of which
are of importance as food for our food-fishes, especially flat-fish.

If one consults a chart showing the depths in our marine waters, one
might almost calculate where there are accumulations of dead weed. It must be
sought for in the deeper bays and at the bottom of the channels
through our waters, especially in the deep parts of the channels. The
dead weed in contrast to the living Zostera may occur in fairly great and very
varying depths.

In the observation material at the end of this paper, the data of the
occurrence of the dead weed which I have been able to procure are stated; but
they only give an indication of its distribution in our waters. I think, however,
that they indicate where there is much dead weed. Referring for details to the
observations themselves, I may here, as in stating the distribution of the living
Zostera, give a short survey of the most important places where it occurs.

1. West coast of Jutland. So far as I know, there are nowhere large
accumulations of dead weed off the west coast of Jutland, and the conditions for
these — plentiful growth of the Zostera and little motion on the sea-bottom — are
also lacking, unless perhaps at Esbjerg. i

38

2. The Lim Fjord. The conditions are quite different here and greatly
favour the formation of dead weed. The movement of the waves carries the loose
Zostera from the coastal margins to deeper parts, and on account of the very
small current, the dead weed may be deposited almost everywhere. The investi-
gations also show in reality, that the dead weed is widely distributed in Nissum
Bredning, Venø Bugt, Kaas Bredning and Thisted Bredning (see the Chart fig. 7).
At many places the dead weed is mixed with the Furcellaria vegetation, frequently
for example in the Nissum Bredning.

3. Kattegat. Large masses of dead weed are found in the Læsø Chan-
nel as well as in the deep channel east of Læsø, as is shown on the Chart fig. 8.
On the other hand, there is not much dead material im the large shallow plateau
of Aalborg Bay, as suitable deep places are wanting.

More to the south where the depths in the Kattegat become more varied,
there are distinct channels and deep, calm fjords and the accumulations of dead
weed reappear here and there, e. g. in Baaring Vig and the bay west of Hindsholm.

5. Little Belt. Large masses of dead weed are found north of Brandsø,
also all along the west and south coasts of the island of Funen, in depths of
8 fathoms and more.

6. Great Belt and Langeland Belt. The conditions here are similar
to those in the Little Belt. In the channels between Romsø and Sprogø, as well
as over a large tract south-east of Sprogø, large masses of dead weed are to be
found in 10—20 fathoms of water, likewise on both sides of Vresen and down
through the waters between Funen and Langeland. The current has also carried
considerable quantities of dead weed down into the deep channel between Aggersø
and Zealand.

As regards the other waters, I have too little information to be able to
make any statements with confidence. It may however be mentioned, that south
of Glænø in the Smaaland Waters dead weed is found in 6—7 fathoms and most
probably the same is the case at many other places in the Smaaland Waters.
Finally, some dead weed has been found in the Baltic south of Rødsand in 12—14
fathoms of water, and according to J. Reinke (l. ec.) it seems to be fairly common
in the whole of the Western Baltic.

VIL. -The other marine flowering plants.

In Professor Warming's work several times referred to on the »strand
vegetation« of Denmark, the few other marine flowering plants are described in
detail so that I need only mention them shortly, the more so as they only rarely
occur in such quantities as to play any important part in the practical fishery.

1. The small, above mentioned (p. 17) Dwarf Zostera or Dwarf
Grass-wrack (Zostera nana Roth) resembles in its structure the common Zostera,
but is on the whole smaller and more delicate. It most often grows on sand
bottom in quite shallow water, from the low water mark to about "/, fathom, often
only to 1—2 feet in depth. The slender, brownish yellow, horizontal root-stock
is hidden in the sand, and from that projects the 10—20 cm. long, quite narrow
(1,;—2,; mm.) ribbon-like leaves; the flowering shoots are generally single or a few
together and never form long, much branching, fan-shaped shoots as the common
Zostera does. The fruit is much smaller, often of a reddish purple colour, and
the seeds are not longitudinally striped.

The dwarf Zostera is found here and there along all our coasts where
there is little motion; as it grows so near land, it cannot thrive where the waves
beat strongly. It generally forms small, pure, fairly open and poor vegetations;
thus it occurs in the ditches on the »Vader« on the east coast of Fanø, at Ny-
mindegab in Ringkøbing Fjord, off Holtemme on the north side of Læsø and at
many other places; not rarely we find patches of dwarf Zostera alternating with
patches of narrow-leaved and low, common Zostera.

The dwarf Zostera can, like this, thrive in real salt water, as the above-
mentioned places show; it is however more frequently found in our inner waters;
I may thus mention as examples Stavns Fjord on Samsø, Randers Fjord at Udby-
høj, Korshavn on Fynshoved and Nakskov Fjord.

It is of no importance as nourishment or as shelter to the marine animals,
as it is too delicate and its oceurrence is hesides too scattered and it never covers
large tracts. —

The remainder of our marine flowering plants are all brackish water
plants; they do not stand the real salt water and are thus absent along the west
coast of Jutland, in the Lim Fjord (excepting, however, the least saline nooks,
e. g. Hjarbæk Fjord), and in the northern and central Kattegat. The degree of

6

40

saltness which they can stand scarcely exceeds ca. 2 p. c. They require" for their
growth, further, a still more protected place than the common Zostera, and none
of them go out to any great depths; J. Reinke (l. c.) states that Zannichellia and
Potamogeton pectinatus occur to 5 meters depth, and I have found the same plants
to ca. 4 meters depth.

The plants spoken of here are: Ruppia, Zannichellia and Potamogeton pec-
tinatus L. Besides these, one may in very sligthly saline water, e. g. in firths and
ereeks into which streams open, meet with others that cannot really be called
marine plants, thus Najas marina L., Myriophyllu mspicatum L., Ranunculus Bau-
dotii Godr. and Scirpus pavulus R. & S.; these will not be discussed here.

2. Ruppia maritima L. resembles in its growth dwarf Zostera. There is
a creeping rootstock, which is generally pale (whitish), and from this issue thread-
fine 8—25 cm. long leaves with a lower, somewhat dilated sheath-part. Branches
issue from very many of the axils of the root-stock so that the Ruppia forms
a net-work in the sandy or soft bottom on which it grows. The branches may
end in an inflorescence which consists of the flowers only, placed at the end
of a shorter or longer stalk; this stalk in the Ruppia growing in fairly deep water
is often very long and reaches the surface, so that the flowers can open in the
air. The pollen is so constructed that it can float on the water (the pollen grains
are curved and short, sausage-shaped) and be carried by the wind to the stigma;
at the end of June I have seen it in such quantities at certain places in Guld-
borgsund that the water looked as if it were covered with a pale-yellow, fine
powder. When the fertilisation is completed, the stalk curves itself up spirally, so
that the fruit will ripen in the water. In other forms of the Ruppia the stalk is
always short, and it must be supposed that fertilisation in these cases takes place
down in the water.

The Ruppia grows in shallow water from the low water mark and to ca.
1 meters depth (perhaps 2 meters); it forms fairly extensive vegetations in a fringe
beyond the beach on almost all the coasts of our inner waters, if the place is
fairly protected. The most northern places, where I have seen it, are in Hobro
and Randers Fjord, at Læsø, and also in Stavns Fjord on Samsø; but it is especially
in the waters south of Zealand and Funen, round about the small islands, that it
occurs in large quantities. The short and fairly dense vegetation is of a dark
brownish-green colour, and resembles a grass-lawn under the water, as the leaves
of the Ruppia are extremely fine (ca. 1 m. broad) and thread-like.

3. Zannichellia palustris L. occurs more rarely in large pure vegetations
than the Ruppia, but it may on the other hand go deeper down in the water, to
4—5 meters, and seems to prefer softer bottom. Some shoots creep along or are
but little submerged in the ground, others rise more or less perpendicularly in
the water. It has thread-fine, 2—8 cm. long leaves placed in whorls of 2—4,
most often 3, at each joint of the stem. In the axils of the leaves, which have
no sheath, we find the small flowers, which consequently open and are fertilized
down in the water. The fruits (generally 4 together) are crescent-shaped and thorny
on the outside of the curve.

Zannichelia is a trifle more sensitive as regards saline water; it lives in
the real brackish water, and is e. g. common in Kalvebodstrand, in the Bøgestrøm

41

and in Guldborgsund. I have also met it in the open Baltic off Falster (in Hes-
næs Bay) in 2—2!/, fathoms. It is of no great importance.

4. More important is Potamogeton pectinatus L., which in ability to stand
the salt water comes between Ruppia and Zannichellia. It is a larger and more
vigorous plant than the latter. Its pencil-thick, white rootstock creeps horizontally
in the bottom at a certain depth and ends in a pointed bud with which it bores
its way forward. From the root-stock issue erect, often meter-long shoots, which
are richly branched in one plane, so that they become fan-shaped. The branches
are supported by leaves and themselves bear leaves; these are thread-like (about
1—1,5 mm. bread), fairly stiff and with somewhat dilated sheaths. At the end of
the shoot there is a many-flowered inflorescence on a thin and flabby stalk. During
the flowering time the inflorescence generally lies on the surface of the water, so
that the flowers open to the air, but after fertilization it is lowered down into the
water, where the brownish fruits ripen.

Potamogeton grows in mud-mixed sand or in pure mud, and forms more
or less dense growths, often of -considerable extent. It always grows in protected
places, as for example in Ringkøbing Fjord, Albu Fjord, Roskilde Fjord, Guld-
borgsund and Grønsund etc. It oecurs from a little beyond the low-water mark
(ca. 1 foot) to 2—3 fathoms depth.

The fishermen do not like it, as the strong and tough shoots check the
progress of the seine-nets along the bottom.

Together with these brackish-water flowering-plants Characeæ often occur
in great quantities: Chara and allied genera (Tolypella and: Lamprothamnus);
these will not be discussed in this paper as they do not belong to the plants
related to the Zostera; but they deserve a closer investigation, as, owing to their
extensive occurrence, they are of practical importance to the fisheries at some
places, e. g. all along the south coast of Zealand from Faxe Bay to Skelskør.

42

VIIL Table of measurements of the length and breadth of
the leaf and of the length of the flowering shoot.

2. Lim Fjord.
EEK 01.
1. Livø Bredning. 5'/,—3 fm.
Soft (sticky) ground. Østløs
church in N.N.W./,W. and |
Aggersborg church E. by N.

2. Nissum Bredning, Hvid- "7

bjerg church in E. by N. 2,
fm. Sand ground.

3. NissumBredning,between ||

Helligsø brickfield and Røj-
ensø Odde. 2—3 fm. Stones
and gravel.

4. Nissum Bredning, E. of
Rønland mare
ground. |

5. Nissum Bredning, EF. of

Stenodden. 2!/, fm. Hard |
ground.
6. Nissum Bredning, N.E.

side of Rønnen. 2!/,—2"|,

fm. Hard(?) ground.

7. LivøBredning, E. of Livø
brickfield. 2!/,—2 fm. Soft
ground.

8. Off Nykjøbing,
fm. Soft ground.

Mors. 2

3. Kattegat.
431; 01.
1. Treaa Mølle in S. 2 miles.
4'/, fm. Sand ground.

The length of
the leaves
in cm.

90795110 123:

85.

110. 70.
120: 110.

95. 80.

115. 145.

D. 175.
155. 140.

110.

165. 110.

. 130.

: 213.

. 168. 190.

70. 83. 85.

The length of
the leaf-sheaths
in cm.

15. 18. 23. 23.

20. 10. 20. 23.
18.

40.

. 60.

ræs
(es)
oa
(SM

50.

mELGNELSE

The breadth of
the leaves
in mm.

35. 4: 5. (6.

&
oo
OR
(ej

The length of
the flowering
shoots in cm.

195.

115.

LS EST Øer La kd:

160.

150.
160.
165.

125:
. 155.
. 160.

245.
220.
195.

. 210.
. 200.

230.

. 180.

43

TT FE ————

2. Muldbjærge in W. !, S.

4 miles. 3 fm. Hard ground.

3. A little N. of the broom
at Østre Flak, S. of Læsø.
Hardly 6-4fm. Hard ground.

4. Muldbjærge in W.S.W.,
Jutland Aas in N.W./.N.
4'/, fm. Hard ground.

W.S.W.
Pure

5. Als church in
9!/, miles. 5!/, fm.
sand ground.

6. In the middle of Gjerrild
Bay. 4 fm.

4. The Waters between
Jutland and Samsø.
Ek 01.

1. Off the north side of As-

hoved.
a. 5—3'/, fm. Soft ground.
b. 2 fm. Soft ground.

2. Off Skødshoved. 5 fm.
Soft ground.

3. West side of Sletterhage.
5"/, fm. Hard ground.

7. Samsø Belt.
Kl 01.
1. Off Ljus harbour at Samsø.
5'!/,—3 fm. Hard ground.

2. Off Udsager Hage. 5—4'/,
fm. Hard, stony ground.

3. North of Ballen. 5'/, fm.
Stony ground.

4. Off Horseklint. 5!/, fm.
Stony ground.

5. S, of Bøgebjærg. 4'/,—4
fm. Hard ground.

8. Great Belt and
Langeland Belt.
SIS OTE

1. East side of Vresen Puller.

a. ca. 4, fm. Hard ground.
b. ca. 3 fm. Hard ground.

2. Off Hou on Langeland.
a. 4'/,—4 fm. Hard ground.
b. ca. 3 fm.

e. ca. 2 —:

Sand ground. |

The length of
the leaves
in cm.

90.

48. 65. 63.

75. 85. 70. 68.
60.

75. 60. 93.

120. 190.
90. 110.

128.

ca. 100.

55. 70.
75. 53. 40. 70.
113. 135. 123.

153. 143.
118. 128. 120.

160. 145.

130. 105. 120.

78. 105. 95.
100. 95.

105. 103. 83. 60.|:

190. 78. 203. 195.

100. 118. 95. 95.

135. 125. 93. 125.

The length of
the leaf-sheaths
im cm.

sl8y

20185513:

SLS AE

The breadth of
the leaves
in mm.

3. — 4,5. (28 mea-
surements).

SNARE3I5:

oa
EM
(on

The length of
the flowering
shoots in cm.

85.

80. 120. 130. 55.

145. 140. 150.
130. 130.

110. 105. 90.

44

3. Off Nedergaard on Lange-
land.
Oy tm:

4. Off Spodsbjærg.
4"/, fm.

9.North coast of Zealand.
el 01.

1. Off Hornbæk, due west of

the boat harbour.

a. nearly 5 fm.

b. 4 fm. Hard sand ground.

2. Creek off Havnsø Mølle,
Nekselø Bay.

a. 4 fm. Soft ground.

b. 3'/, fm. Soft ground.
c. 11, fm. Hard ground.

3. Off the N.W. corner of
Nekselø 3!/,—3 fm.

Hard sand ground.
4. Off Lille Vrøj.
Sand ground with stones.

5. Off Hestehavegaard on
the north side of Refsnæs.
3 fm. Hard ground.

11. The Sound. |
20/ 01.
1. Within »Trekost« at Prø-

vesten.
3—31/, fm.

2. Between »Tokost« and
»Trekost« on Middelgrund.
2 fm.

3. »Etkost« at Sundbyhage.
4—4"/, fm.

4. Within
Svalerumpe.
3 fm.

the broom at

5. Within the buoy at Ka-
strup Knæ.
3"/,—2"/, fm.

6. Side of Saltholm, off the
boat bridge.

ass

b. 2 ifm.

7. Within the broom at Salt-
holm Flak.

a. 3 fm.

b. 2 fm.

21/, fm. |:

The length of
the leaves
in cm.

143.
170.
122.

40!
3. 123.
. 140.
200. 223. 170.
190. 165

160.
140.
135.

123.

113.

125.

175. 115.
143. 120.150.130.
38. 45. 38.

48. 38. 35.

25. 23.

20.

5. 113.

105. 120. 110.

160. 1

123.
100.

120. 4107:

95.
53. 55. 40.

115. 108.
50. 65. 58.

The length of
the leaf-sheaths
in cm.

The breadth of
the leaves
in mm.

The length of
the flowering
shoots in cm.

. 30. 28. 33.

(Sy)
(Sl
(SL)
E
(g5)
os

. 40.

. 40. 27. 30.

30.

25.

. 85.
3.28:

5. 6. 5,5. 5,5.
5,5. 5. 5. 5. 5.

5,5. 6. 5. 6. 5,5.

5.
AED RRA NS MANS RAN

250. 220.

98. 113.

160. 168. 175.

70.

45

| The length of

The length of

The breadth of

The length of

the leaves the leaf-sheaths the leaves the flowering

| in cm. in cm. in mm. shøots in cm.

8. E. and S.E. of the bell-||58. 63. 87. 15:15:23: 45. 5. 45. 80.

buoy on Saltholms Flak. |

4—2"/, fm, ||

9. Between Taarbæk Reef (103. 113. 103. 28:33. 30. 38... 15,8. 6,5. 6,5. 5,5. 160.90: 118. 128.

and the coast. 123.

3 fm.

10. Off Skodsborg landing | 163. 160. 43. 38. TESTE 160. 225.

stage, Lower side.

4—3"/, fm.

11. Off Rungsted landing 88. 110. 85. 30. 30. 25. 5. 45. 5 80.

stage.

3 fm.

12. Nivaa Bay. 63. 50. 65. 20. 15. 18. 45. 4,5. 5.

2 fm.

12. Smaaland Sea.
ETA OF

1. O£ Kragenæs harbour. |/118. 120. 113. | — — — — — (0606: H 93:

2—3 fm. Soft ground. 88. 98.

2; Vigsø churchin W. Guld-||120. 138: 120. (t ——-—— 6; God 180155:

borg L. in S. by E.//,E. 100. 108. 6,5.

Nearly 3 fm. Soft ground.

3. Off Knudshby. 683 60380375 | RE 4, 4, 5.4.4, | — — — — —

3 fm. Sandy ground. 65.

4. Venegrund. Søk IS ETS EEK (SR et 2 BER IEEE HERE SES SR BRET

4 fm.

5. Kirkegrund. 103:95.100; — | — — 5 6. 55. 55. … | /— — — — —

4 fm.

6:"Basnæs IN: by :3 miles 1955125:123: — |. == 6.55.6. …… | — — — — —

4 fm.

7. Helleholms Lighthouse in

N.W. 7/, N. 2 miles.

ao gsm, 88. 100. 103. 80.| — — — — — 4. 5. 5. 45. 5. | — — — — —
83. 73. 4,5.

b. 4!/,—5 fm. BON 140 | TR 6. 6.6.55. | — — — — —
110.

8. The buoy at Omø Tofte.

a. Nearly 5 fm. TAO OS RR 5,5:5.- … JR — — — —

b. 2 fm. Sand ground. 60. 40. 80. 58. | — — — — — 4: 5:57 5. 545. (60:55. 63: 50.
53453370 63: 535)

13. Guldborgsund.
51, 01.
1. Between Hasselø
Kalvø.
Cal | m:

and
Hard ground.

2. Hasselø Bredning.
ca. 1'/, fm. Hard ground.

130. 170. 158.
125. 135.

70. 65. 70. 65.
73. 58.

46

|
3. Flinthorne Reef in N.byE. |
f, E.

/
[2
3 fm. Soft ground.

4. Nysted church in N.E.!
byNS/ÆEN:
2 fm. Soft ground.

5. WithinRødsand, at Fugle-
holm. Soft ground.
a. ca. 2 fm.

bilcamBstm!
6. Skælby church in N. by E.
"/,E. Gedser harbour light-

house in S.E. 2%/, fm. Soft
ground.

14. Bøge Stream.

ROTE
1. North of west end of
Tærø.
2 fm. Soft ground.

2. North of N. Knigge.
1'/, fm. Soft ground.

15. The Baltic.
LO
1. Tromnæs i N.W. by W.
5"/,—2"/, fm. Stony ground.

2. Hesnæs Bay.
27/,—2 fm. Sand ground.

3. Outside the Bøgestrøm
buoy.
2"Tm:
stones.

Sand ground with

4. Off Faxe.
4 fm. Sand ground.

The length of
the leaves
imens

110. 95. 103. 100.
73. 105.

105. 115. 128.
11115. 105. 135.
115. 115. 108.
135. 108. 130.
100. 120.

140. 125.
120:110.128:
165. 155. 150.
155.

98. 105. 90. 103.
95: 75:

68. 60. 48. 75.
50. 33. 35. 25.
43. 55. 48. 50.
40. 45.

33. 43. 33. 45.
38. 35. 45. 3
63. 83. 65. 58
bd. 65.

The length of
the leaf-sheaths
in cm.

The breadth of
the leaves
in mm.

TOD ED RE

The length of
the flowering
| shoots in cm.

95.

80.

105. 135. 93. 120.
100. 105. 95. 88.

47

IX. The Material collected and observed.

The data below are partly from my own investigations, partly from
observations made by the Danish Biological Station; the latter observations are
copied from the Station's Journals which Dr. C. G. Joh. Petersen kindly entrusted
to me. My observations extend over the period between July 20th and August
9th 1901. The rest of the observations are nearly all from the Biological Station.
The statements about occurrence of dead weed are only separated from the other
observations for the Lim Fjord, Kattegat, Little Belt and Great Belt, as they are
more numerous for these places.

The grass-wrack is everywhere denoted here by »Zost.«, viz. »Zostera«.
The few other abbrevations need no special explanation.

2. Lim Fjord.

29/, 01. Nissum Bredning. Between Helligsø brickfield and Røjensø Odde.
3—2 fm. Stones and gravel. At places, medium long and medium broad-
leaved Zost.

290, 01. Nissum Bredning. Hvidbjærg church in E. by N.

3 fm. Sand ground. No Zost.

29/, 01. Nissum Bredning. E. of Rønland.

23/,—21/, fm. Quantities of Furcellaria. No Zost.

29/, 01. Nissum Bredning. Same place, a little nearer land.
21/, Fv. Long, medium-broad Zost.

29/1, 01. Nissum Bredning. E. of Stenodden.

21/, fm. Long, medium broad Zost.

10/. 00. Nissum Bredning. Gjellerodde on Lemvig Fjord.
17/, fm. Mud ground. Long and broad-leaved Zost.

291, 01. Nissum Bredning. N.E. side of Rønnen.

211,—21/, fm. Zost. and Furcellaria.
29/, 01. Nissum Bredning. Kamstrup Bakke in S.
3—2 Fy. Sand ground. No Zost.
Ob. The white disc. to be seen at 23/, fm.
290, 01. W. of Oddesund N. Højbjærghøj over Oddesund N.

>

3—2 fm. Sand ground. No Zost.

-

le (040)

99
S)S)-
00.
JOR
00.

01.

00.

; 00.
99:
01.
01.

00.

0

(Hals
99.
00.

; 00.

00.
00.

Sl 1040),

48

At Oddesund N.

31/,—21/, fm. Thick growth of long Zost.

E. side of Venø.

3—2 fm. Zost. vegetation.

Creek north of the Ferry harbour on Thyholm.

Long Zost.

Næs Sound.

31/,—2 Fv. Dense growth of long Zost.

Salling Sound at Gammeløre.

3/s fm. (75 cm.) Sand ground at places medium long, rather broad-leaved Zost.
At Nykøbing outlet.

Long and broad-leaved Zost. Rich growth.

In shallow water, S. of the Harbour, 1—!/, fm., shorter but still rather
broad-leaved Zost.

Thisted Bredning. Fegge Sound in E., Østerild church in N.

21/1, fm. Sandy and hard ground, partly with Furcellaria, plenty of long
and broad-leaved Zost.

Fur Sound.

Zost. [»Grass-ground«.]

S. of Fur church.

1—/, fm. Zost.

E. side of Livø Tap.

Scarcely 3 fm. Soft ground with scattered stones. No Zost.

E. of Livø brickfield.

21/,—2 fm. Soft ground. Very long and broadleaved Zost.

Off Løgstør Grounds. Bulbjerg i N., Løgstør church in E.S.E.

3—21/, fm. Sandy ground. Long, but rather narrow-leaved Zost. in sparse
growths.

Løgstør Bredning. Off Løgstør Ground.

The observations commenced at scarcely 3 fm., and were continued to scarcely
3!/, fm., Østløs church then being in N.N.W.//,W., and Aggersborg church
in E. by N.

Everywhere long, medium broad-leaved Zost.

Østløs church in N.N.W. Aggersborg in E. by N.

At 3!/, fm. the ground was bare (without Zost.).

E. of Løgstør Canal.

Scarce Zost. growth.

Atruplaa.

2 fm. Soft ground. Long and broad-leaved Zost.

The Bay north of Troldholmene.

In the channel at 2!/,—/, fm. Broad-leaved, rather long Zost. in rich growth.
At the edge of the channel towards the shallow water the Zost. shorter and
more narrow leaved.

The shallow water at //,—"/, fm. and inwards has clean, bare sand bottom.
On the grounds S. of Øland the Zost. forms extensive growths like green
meadows, to be seen at ebbtide.

The channel S. of Gjøl.

Ca. 2 fm. Long, broad-leaved Zost.

Langerak, at the margin.

2—1/, fm. Very large Zost.

Dead Weed.

N.E. of 1 broom on Thyborøn Fjordgrund.
Some Dead Weed.

00.

00!
00.
(010)
00.
00:
00.
00.
005
00.
500.
00:

00.

00.

49

Lodbjærg Lighthouse in N., Røjensø brickfield i N.E. by E.
Dead Weed and green Algæ.
S. of Thyborøn Fjordgrund.

Dead Weed.

»Enkosten« at Lemvig Røn in $.W. .1!/, miles.
Some Dead Weed.

N. Nissum church in S.W.//,W. 3 miles.
Furcellaria and some Dead Weed.

3/. and &/,00. N. Nissum church in S.W.//,85. 47/, miles.

Some Dead Weed.

N. Nissum church in S.//,W. 21/, miles.
31/, fm. Lots of Dead Weed and Furcellaria.
N. Nissum church in W. by N. 32?/, miles.
Dead Weed and Furcellaria.

Venø Bugt.
3 fm, Dead

Venø Bugt. Struer church in 8.8.W.//,W., Humlum church in N.W. by W.!/,W.

Dead Weed.

Humlum church in W.N.W.
Weed.

Venø Bay. Struer church in N.W. by W./,W.
3 fm. Lots of Dead Weed and Furcellaria.
Kaas Bredning. Gammellund in N., Bøløre Odde in W.N.W.

3 fm. Dead

Weed.

In the middle of Kaas Bredning.

3 fm. Dead
Vilsund.

Weed.

Ca. 8 fm. Great quantity of Dead Weed.
Thisted church in N., Silstrup Hoved in W.
Dead Weed and red Algæ.

Thisted churc

h in N. by W. 22/, miles.

A quantity of Dead Weed.
N. of Hanklit. 1 mile.

Dead Weed.
Langerak, in

the course.

5 fm. A little Dead Weed.

Aalbæk Bugt.
Sand ground.

3. Kattegat.

Lost.

Within Hirtsholmene.
5—6 fm. Zost.
At Hirtsholmene.

Long Zost.

N. of Frederikshavn Harbour.

2[.—"/; fm.

Zost.

S. of Frederikshavn Harbour.

Zost.
Sæby church
5 fm. Zost.

At Asaa, the
41/,—3 fm.

in S.W. by W.//,W., Bangsbo Bakke in N.N.W.3/,W.

outer side of Rimmen,
Large Zost,

== (OLE

00.

00.

01.

OT

01.

LO (E

11010);

Asaa in N.N.W.

4 fm. Quantity of large Zost.

Læsø. Rønne Reef, N. of Holtemme.

Sand ground. Shallow water.

Near land: Zost. nana; further out: short, narrow-leaved Zost.

A little 8. of »Trekosten« on Flyndergrund, Læsø.

6—5 fm. Short, growing Zost.

Læsø Channel light-ship in N.W. by N.N. 6 miles.

6—5 fm. A little living Zost., a quantity of Dead Weed and. Furcellaria.
Further towards the shore in the direction of Flakket, scattered patches of
Zost. in ca. 3!/, fm. on sand ground.

A little N. of the broom on Easter-Flak, S. of Læsø.

Quite 6 fm. Hard ground. No Zost.

6—5"/, Fv. A little living Zost., and some dead.

5—4 fm. Hard ground. Patches of Zost.

Eastern Knold. S. of Læsø.

4—3 fm. Fast ground. Small patches with Weed.

Between Eastern and Western Knold.

5!/, fm. Hard ground. Very little Zost.

Muldbjerge in W.S.W. Jutland Aas in N.W.//,W.

7—6 fm. Hard ground with stones. No Zost.

Muldbjerge in W.S.W., Jutland Aas in N.W.7/,N.

41/, fm. Hard ground. Rather a quantity, short and narrow-leaved Zost.
Muldbjerge in W.S.W., Jutland Aas N.N.W.

41/, Fv.. Hard ground (pure sand). Sparse, short and small-leaved Zost.
Vejdyb, at Hals.

Long Zost.

Between Muldbjerge and Hals.

A little Zost. and a quantity of Dead Weed.

S.E. of Muldbjerge broom.

21/, fm. Some Zost. but rather small.

Muldbjerge in N.N.W. Jutland Aas in N.//,W.

31/, fm. Light sand ground with patches of Zost.

Muldbjerge in W.//,8S. 4 miles.

3 fm. Hard ground. Short, narrow-leaved Zost.

E. by N. of Hurup.

3 fm. Living Zost. and a little Dead Weed.
2 fm. Living Zost. and Dead Weed.

Muldbjerge in N.W. by N. 6 miles.

3 fm. Hard ground. Short, narrow-leaved Zost., many dead leaves.
Als church in S.W.W. by W./,W. Jutland Aas in N.//,W.

5 fm. Stony sand ground. Zost.

Als church in W.S.W. Muldbjerge in N.N.W.//,W.

3%/, fm. Sand ground. Plenty of Zost.

Als church in W.S.W. 9//, miles.

5!/, fm. Pure sand ground. A little short and narrow-leaved Zost.
Als church in W.7/,8S. 67/, miles.

4 fm. Patches of short and narrow-leaved Zost. on sand ground.
Als church in W. by N.3/,N.

51/, fm. Sand ground. No Zost.

5 Im. Zost.

16 miles E. of Mariagerfjord.

7 (?) fm. Zost.

Sødringholm Wood in W.//,5., Stavnshoved i S.//,E.

61/, fm. Clay mixed with sand. No Zost.

N.B. The white disc to be seen to a little more than 5!/, fm.

01.

99.

01.

01.

01.

OM

Randers Fjord at Udbyhøj.

a) in the stream, no Zost.

b) at the edge from ca. "/,—!/, fm., dense growth of long, narrow-leaved Zost.
c) "/,—0 fm. Scattered growths of Zost. nana and Ruppia.

N. by W. of Treaa Mølle. 41/, miles.

3—2 fm. Zost.

Treaa Mølle in S. 2 miles.

41/, fm. Sand ground. Scattered, rather short, medium broad Zost., a little
Furcellaria.

In the middle of Gjerrild Bugt.

4//, fm. Stones with Halidrys, Desmarestia viridis, Ectocarpus etc. No Zost.
From a little more than 4 to 3 fm. Sand ground with very small and scattered
patches of short and narrow-leaved Zost.

Off Havknude (South side).

5—3!/, fm. Stony ground. Fucus, Furcellaria and other algæ (e. g. Co-
rallina), mixed with very little Zost.

Off Draaby.

6—57/, fm. Stones with Fucus etc. No Zost.

5—31/, fm. Sand ground with stones. No Zost.

Dead Weed.

7. E. of Marens Reef.

10 fm. A little brown Zost.

N.W. of the Northern Rønner. 5 miles.
23—20 fm. Much Dead Weed.

N.W. of Northern Rønner. 4 miles.

18—16 fm. Dead Weed.

Northern Rønner in $. by E.//,E. Ca. 5 miles.
17//, fm. Dead Weed (Root-stocks and Roots) in quantities.
E. of Sæby (Sæby church in W.S.W.).
24—13 fm. A good quantity of Dead Weed.
Sæby in W. 6—7 miles.

11 fm. Lots of Dead Weed.

Between Trindelen lightship and »Trekosten«.
Ca. 20 fm. A quantity of Dead Weed.

Off »Trekosten« N.E. of Læsø.

20 fm. Dead Weed.

4 miles N. of Kobbergrunden lightship.
40—25 fm. Dead Weed.

1 mile N. of Kobbergrunden lightship.
17—10 fm. Lots of Dead Weed.

Anholt lighthouse in S.W.7/,S. 7 miles.

23 fm. A quantity of Dead Weed.

E. by N. of Udbyhøj Baake. 2!/, miles.

4 fm. Lots of Dead Weed.

52

4. The waters between Jutland and Samsø, and
Aarhus Bay.

27/, 01. W. of Moselgrunden at Hjelm.
6 fm. Living Zost.
27/, 01. N.W. of the white broom at the light buoy on Moselgrund.
5 fm. Dead Weed.
24/, 01. Alhagen at Ebeltoft.
5—4"/, fm. Broad-leaved, long Zost.
%/, 01. Off Bagnsholm.
57/, fm. The ground rather hard. Medium long and broad Zost.
24/, 01. E. of Lushage.
3 fm. Patches of sand on Zost. ground.
24/, 01. W.side of Sletterhage.
6 fm. Hard ground. No Zost.
261, 99. Helgenæs.
4—3 fm. Plenty of Zost.
26/, 99. Begtrup Vig.
41/, fm. Zost.
34/1, 01. Molshoved.
Ca. 3 fm. Spotted sand ground, chiefly Zost. (medium long and broad), a
little Fucus vesic.
2/, 01. Ground S. of Skødshoved, Kjeldshoved to the E.
3—21/, fm. Like the preceding.
4/, 01. Off Skødshoved.
71/,—5"/, fm. No Zost.
5 fm. Very long and broad-leaved Zost.
2%4/, 01. Vosnæs Point.
From 5 fm. inwards: long, broad-leaved Zost.
At 2!/, fm. bare patches occur in the up to now dense growth; Zost. shorter
and narrower.
The ground soft outwards, firmer nearer land.
al 01. Off Egaa Point.
6 fm. No Zost.
5—4 fm. Plenty of Zost., meter-long, broad-leaved.
3 fm. Å little, rather short, but broad-leaved Zost. between Furcellaria and
Fucus vesic.
23/, 01. Off the S. end of Marselisborg wood.
41/,—2!/, fm. Meter-long, broad-leaved Zost., nearer shore with large, bare spots.
230, 01. Off Kysing Hage (Norsminde Flak). ;
SGT em NOS ost
5—4 fm. Large, broad-leaved Zost., but a little shorter than the preceding.
23/, 01. Off Dyngby Hage.
6—51/, fm. No Zost.
5—2 fm. Densely growing, long, broad-leaved Zost.
At 2 fm. Bare patches and harder ground. Zost. a little shorter.
REDDER WERE Dan:
4—3 fm. Zost.
26, 99. N. of Hou Harbour.
4 fm. Long Zost.
23/, 01. E. of Søby Reef, S. of the channel at Hou.
3 fm. Long, broad-leåaved Zost.
231, 01. A little S. of the broom on Søgrund, towards Svanegrund.
4 fm. Large, broad-leaved Zost. 2 m. long.

01.

01.

01.

01.

5l, 99.

. and

53

The whole area from W. of Endelave to Horsens Bay is evidently covered
with broad-leaved Zost.

Between the brooms on Skomagergrund and Møllevinge.

3 fm. Large, broad-leaved Zost.

Asvig, off Sønderby Wood.

At 6 fm. No Zost. Soft ground.

Large broad-leaved Zost. at 5—2"/, fm.

Off Ashoved, N.side.

At 5—2 fm. Densely growing large broad-leaved Zost., though further in with
bare spots.

At 5—3 fm. it is very broad and nearly 2 m. long. At scarcely 2 fm. meter-
long and a little narrower.

The ground certainly soft up to 2 fm.

Large patches with densely growing, rather short, narrow-leaved Zost. and a
little Fucus vesic. along the whole S. coast of Endelave at 3//,—21/, fm.
The patches thickest at 4 fm. and scarcer towards land.

This sort of ground continues S.W. of Endelave in shallow water, but at
5!/, fm., between Endelave and the broom at Lillegrund, bare ground
(no Zost.).

5. Little Belt.

At Vaarsø in Horsens Fjord. (Enclosed water.)

1!/,—1 foot Mud ground. Even growth of narrow-leaved Zost.
The channel (6—9 foot) partly overgrown.

Enclosed water at »Skoven«. Horsens Fjord.

Car TMS Zost:

Skærbæk on Kolding Fjord.

4—21/, fm. Long and broad-leaved. Zost.

"4 91. Kolding Fjord.

Up to 3'/,—3 fm. Thick growth of Zost.

and %/, 91. Fenø Sound.

91:

00.

s 00.

91.

00.

; 00.

Se 00:

Rich growth of long and broad-leaved Zost.

Under the land shorter and narrow-leaved Zost.
Gamborg Fjord.

Zost.

Flækøjet.

4—21/, fm. Very long, broad-leaved Zost. in large quantity.
Off Stenderup Hage.

Ca. 21/, fm. Medium-long Zost.

Gudsøvig.

Short and narrow-leaved Zost.

N. of Brandsø.

5 fm. A little Zost.

N. of Avernakø.

8(?) fm. A little Zost.

The bay west of Faaborg.

1 fm. Fucus and Zost. with patches of bare sand.
Ca. ”/, fm. Richer growths.

Nearer land scattered, narrow-leaved Zost. and Ruppia.
The same on the N.E.coast of Bjørnø.

SO OR

301

OVS
Boe
moNg
el,
[5

12/6

Bla

00.

99.
I. 00.
00!
00.

; 00.

00.

00.

00.

SS).

54

Dead Weed.

N. of Brandsø.

9—5 fm. Lots of Dead Weed.
Brandsø and Ivernæs.

10 fm. Some Dead Weed.
The whole Bredning N. of Brandsø seems to be full of Dead Weed.
W. of Horne Land.

13 fm. Some Dead Weed.
Lyø Krog.

13 fm. Much Dead Weed.
Avernakø church in W.S.W.

8 fm. Lots of Dead Weed.

N. of Avernakø.

Dead Weed.

N.E. of Søby.

11 fm. Some Dead Weed.

6. Odense Fjord.

On the outer side of Hals Odde.
7—5/, fm. No Zost.

4—2 fm. Long and broad-leaved Zost.
Just outside »Gabet« in Midskovbugt.
4—2 fm. Long and broad-leaved Zost.
Just inside »Gabet« in Midskovbugt.
3—2 Fv. Long and broad-leaved Zost.
Midskovbugt.

3 fm. Long and broad-leaved Zost.

At Dørholm.

1—”/, fm. Scattered growing Zost.

N. of Vigelsø.

T'/.—5/, fm. Scattered growing Zost.
N. of the landing stage at Vigelsø.
em ost

At the end of the channel below Lumby.
1—?/,. fm. .Narrow-leaved Zost.

7. Samsø Belt.

N. of Vejrø.

7 fm. Dead Weed.

Udsager Hage on Samsø.

5—41/, fm. Patches of Furcellaria etc. A little Fucus vesic., some short
and narrow-leaved Zost.

The same conditions observed at ca. 3 fm.

55

1/, 01. A little N. of Ballen.
| 51/, Fy. Stony ground. Mostly Furcellaria, Rhodomela and Laminaria saccha-
rina, some Delesseria, Cystoclonium etc., a little medium-long and -broad Zost.
231, 01. Off Ljushavn on Samsø.
31/,—3 fm. Hard ground with patches of narrow-leaved, rather short Zost.

8. Great Belt and Langeland Belt.

1/8 01. Off Horseklint.
6—57/, fm Furcellaria etc., no Zost.
57/, Fv. Long and narrow-leaved Zost in great quantity.
From this depth and inwards; Zost.
1/3 01. S. of Bøgebjerg.
5 fm. Furcellaria etc. Some Dead Weed, no living Zost.
4"/, fm. Plenty of Zost., which continues to 2!/, fm., then scattered patches
with sand and Fucus vesic.

1/8 01. From a little south of broom on Romsø Røn to Stavreshoved.
Barely 5 fm. Hard ground. Zost. long, but rather small-leaved; dense growth
over the whole place, but a few patches of sand and Fucus vesic.

1/8 01. Møllegrund.

According to statement: Zost. everywhere between 5 and 3 fm.

19/. 99. N. of Kjerteminde Harbour, in the corner.

5 Fv. AÅ little living, but much dead Zost.

2%/, 98. Off the Marine Hotel at Christianslund.
41/, fm. Living Zost.

23/. 00 and ?6/, 98. N. of Knudshoved.

4—3 fm. Hard ground. A little Zost.

30/. 99. S.E. of Knudshoved.

4 fm. Zost. -

??!, 00. Off Slipshavn.

Zost. and patches with sand ground.

19/, 98. At the upper end of Nyborg Fjord.
6—5 fm. No Zost.

4—3 fm. Long, broad-leaved Zost.

10/, 98. In Holckenhavn Nor.

?[.—"/, fm. Zost.
17/[, 98. N.W. of Palegrund.
6—5 fm. Living, long Zost.

1119. 98. Sprogø lighthouse in N.N.E.7/,E., Nyborg Church in N.W.//,W.
41/, fm. AÅ quantity of Zost.

2?/. 00. Off the S. end of Kajbjerg Wood.

5—3 fm. Long and broad-leaved Zost.
5/9 98. Vresen Puller at the buoy.
5!/,—-4 fm. Zost.

??/ 00. The same place.

317/,—3 fm. Some scattered Zost. among Fucus etc.

29. 00. Due W. of the broom at Vresen Puller.

Zost.
?8/, 98. W. side of Vresen.
7 (?)—4 fm. Zost.

56

[=]

fg 01. E.side of Vresen Puller. j
41/,—4 fm. A little Zost. among Furcellaria, Fucus etc.
3 fm. Plenty of Zost.
21/, fm. A little Zost., mostly Fucus ete.
BOD SENOEEKOngsbøj
Zost.
3/, 00... Withim Stokkebæk Flak.
5—4 fm. Much large Zost.
3/1, 00. N. of Lundeborg Harbour.
4—3 fm. Much long Zost.
3—21/, fm. A little shorter Zost.
lg 00. Off Skaarupøre.
4—3 fm. Long Zost.
3/, 00. Inner side of Turø Reef, near the broom.
3!/,—3 fm. Some long Zost.
31, 00. Lungebugten, Stenodde in W. by 8.
41/,—4 fm. Long Zost. and some Dead Weed.
21/, fm. Not particularly large Zost.
"(10 98. »Trekosten« at Hou Sand.
3 fm. Zost.
ks (OM, (ir JB
5 fm. Large Laminaria digitata, Furcellaria etc., few shoots of Zost.
41/, fm. Scattered Zost. among Laminaria, Furcellaria etc.
3 fm. Plenty of Zost.
2 fm. Patches of Zost. and Fucus.
Nb NbeRwhiteldiset seenktolcanvd ktm
?/, 01. Off Nedergaard.
5!/, fm. Fair amount of long Zost., which continues to at any rate ca.
ca. 21/, fm., then a quantity of Fucus.
?/, 01... Off Spodsbjærg.
57/,—5!/, fm. Some long and medium-broad Zost.
41/, fm. Plenty of Zost., like the preceding.
?/, 01. Off Kjelds Nor towards Dovnse Klint.
4!/,—3"/, fm. Stony ground. A little small Zost., some Fucus.

Dead Weed.

18/1 99, The channel between Sprogø and Romsø.
16—15 fm. A quantity of Deaf Weed.
27/, 98. Sprogø lighthouse in S.E. and Nyborg Church above the W. end of Christians-
lund Wood.
A little Dead Weed.
29/. 00. Off Nordenhuse.
10-—9 fm. —A little Dead Weed.
21/ 00. S. of Sprogø.
11rv. Dead Weed:
290. 00. S.E. of Sprogø.
20—11 fm. Much Dead Weed.
es es ROOS progøl in NEN WE
12—11 fm. Much Dead Weed.
5/1; 00. The Channel W. of Vresen.
Much Dead Weed.
171, 99. EH. of" Vresen.
7—6 fm. Dead Weed.

00.
98.

00.

01.

01.

01.

01.

01.

01.
01.

01.

01.
(ulig

og
01.

Og

Off Vresen Puller.

13 fm. Æ little Dead Weed.

Knudshoved in N. by W.3/1W. and Vresen broom in N.E./,E.
81/, fm. Dead Weed.

Turø Reef's Inner side, near the broom.

6—5 fm. Soft ground. Dead Weed.

9. The north coast of Zealand.

Off Hestehavegaard on the N.side of Refsnæs.

3 fm. Hard ground. Fucus vesic. and short, narrow-leaved Zost. in patches.
Off Little Vrøj.

4—3 Fv. Sand ground with small stones. Fucus vesic., Furcellaria, Phyllo-
phora, Delesseria etc. in patches. No Zost.

21/, fm. Fucus vesic. and short, narrow-leaved Zost. in patches.

Off N.W. corner of Nexelø.

3!/,—3 fm. Sand ground. Spots of Fucus vesic., Chorda and short, narrow-
leaved Zost.

In Nexelø Bay off Havnsø.

4—2!/, fm. Soft ground. Thick growth of long and broad-leaved Zost.
1//,—"/, fm. Hard ground. Rather thick growth of short and narrow-leaved
Zost., furthest in only patches of Zost., Chara and Ruppia.

N.E. of Kongstrup at Sejerø.

4—3 fm. Sand ground. Single patch of narrow-leaved Zost., stones with
Fucus, Furcellaria etc.

Through Snækkeløb at Zealand Odde and southwards: scarcely any Zost.
because the ground, where visible was pure sand and with small patches of Fucus.
Odden Church in S.

6—4 fm. No Zost., but Fucus, Furcellaria, Halidrys etc.

In Nyrup Bay, E. of Klintebjerg.

31, —21/, fm. No growing Zost., but a few loose, old leaves; patches of
Fucus, Furcellaria and Halidrys.

Grønne Revle.

Bare sand ground. Like the preceding. No Zost.

Off Spodsbjerg.

4 fm. Gravelly and stony ground. Single patches short, narrow-leaved Zost.
For the rest Fucugs, Furcellaria etc.

Off Tidsvilde Leje.

5—4 fm. No Zost., but Fucus, Furcellaria ete.

Off Gilbjerghoved.

41/,—4 fm. Like the preceding.

Off Hornbæk. Due W. of the boat harbour.

Hardly 5 fm. Sand ground. Large, rather broad-leaved Zost. in small
quantity.

41/,—31/, fm. Patches of strong, but rather short and narrow-leaved Zost.
Here and there Fucus, Furcellaria etc.

2
mf,

(Oil:

01.

(Ol

(Oak

01.

(OL

01.

01.

(Oil;

01.

01.

01.

58

11. The Sound.

Off Snekkersten.

45/,—31/, fm. Plenty of long and broad-leaved Zost.

Off Humlebæk.

4—31/, fm. The ground rather soft. Rich growth of broad-leaved Zost. with
scattered Rhodomela.

Nivaa Bay.

5—41/, fm. No Zost.

4—2 fm. Sand ground with hare spots varied by growths of Rhodomela
and scattered Zost.

Off Rungsted landing stage.

4—21/, fm. Sand ground with large patches of Rhodomela, mixed with
scattered, rather small Zost.

Off Skodsborg landing stage, N. side.

4—31/, fm. RQRhodomela-ground mixed with scattered long and broad-
leaved Zost.

Between Taarbæk Reef and land.

3 fm. Rhodomela-ground at many places, with scattered long and broad-
leaved Zost.

E. and S.E. of Klokketønden on Saltholm Flak.

4—21/, fm. Almost nothing but Fucus serratus, Furcellaria etc., a very little
short Zost.

Within the broom at Ryggen, Saltholms Flak.

3 fm. Scattered, medium-long Zost.

In the channel, inner side, no Zost.

On Flakket (2 fm.) very little short Zost., mostly Ectocarpus, Chorda and
Fucus serratus.

Alongside Saltholm, off the landing stage.

Gravelly and stony ground.

3 fm. A little rather broad-leaved Zost., but mostly Ectocarpus etc.

2 fm. A little, narrow-leaved, low Zost., mostly Ectocarpus, Fucus etc.
Within the barrel on Kastrup Knæ.

3!/,—21/, fm. Plenty of broad-leaved Zost.

Within the broom on Svalerumpe.

4—3 fm. in the Channel; no Zost., but Rhodomela, Ectocarpus etc.

Zost. commences singly at 3!/, fm.

3 fm. Plenty of broad-leaved Zost.

»Enkosten« at Sundbyhage.

4!/,—4 fm. Scattered, broad-leaved Zost., mostly Ectocarpus, Chorda, Lami-
naria sacch., Delesseria sanguinea.

3 fm. Plenty of broad-leaved Zost.

Between »To-« and »Trekosten« on Middelgrund.

2 fm. Long, broad-leaved Zost., covering the ground.

Within »Trekosten«, at Prøvesten.

& fm. No Zost.

31/,—3 fm. Broad-leaved Zost.

50100:

VROE

31, 01.

Sr OS

99.

OT

OTTE

COTE

00.
0

KOTE

ol

01.

(its

01.

12. Smaaland Waters.

Aggersø Sound.

22—6 fm. Dead Weed.

5—2 fm. Dark sand ground. Zost.

Dybe Rende, S.E. of Aggersund.

16—10 fm. Dead Weed.

Helleholm lighthouse in N.W.//,N. 2 miles.

Fully 5 fm. No Zost., but Rhodomela, Ectocarpus, Furcellaria etc.

5—4!/, fm. Rather long and broad-leaved Zost. among Algæ.

3 fm. Plenty of Zost., a little narrower, but nearly the same length.

N.B. The white dise seen at exactly 5 fm. in the ca. 13 fm. deep channel.
At the barrel on Omø Tofte.

Ca. 5 fm. Long, medium broad-leaved Zost.

21/,—2 mf. Sand ground. Patches of rather short, but strong Zost., covered
by lots of Mytilus.

E.side of Omøs Staalgrunde.

Ca. 4!/, fm. Plenty of Zost., with the same appearence as at the just
mentioned stations.

Basnæs i N. by E. 3 miles.

Zost. grows out to 43/, fm.

4 fm. Plenty of long and broad-leaved Zost.

S. of Glænø.

7—6 fm. Much Dead Weed.

4—2 fm. Zost. and Fucus among large, bare spots.

Kirkegrund.

5—4"/, fm. No Zost.

Hardly 4"/, fm. Rather long and broad-leaved Zost.

Venegrund.

Like the preceding.

All plants taken at the stations between Venegrund and Omø had a rich
growth of Membranipora and Ectocarpus on the older leaves.

Off Knudsby.

5—3%/, fm. No Zost.

3"/,—3 fm. Ground mixed with sand. Rich growth of medium long and
broad Zost.

S. side of Knudshoved Pynt.

Ground mixed with sand. Zost. goes out to 3!/, fm.

Ofl Kragenes Harbour.

517/,—3!/, fm. Bare mud ground. No Zost.

3 fm. Long and broad-leaved Zost.

NB. The white disc only seen at 1!/, fm., owing to rough water.

Fæmø Sound, between Skopen and Middelgrund.

4 fm. Bare mud ground. No Zost.

3—2 fm. Plenty of long and broad-leaved Zost.

At Leda Grund.

4 fm. No Zost.

3 fm. Long and broad-leaved Zost.

Vigsø Church in W., Guldborg L. in S. by E.//,E.

3 fm. Scattered long and broad-leaved Zost. in an undergrowth of loose
Cladophora rupestris.

At ca. 3 fm. Plenty of large Zost.

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13. Guldborgsund.

Off Majbølle-isle, S. of Grummers Nakke.

5—3 fm. No Zost.

The sand bed rises suddenly to a depth of 1 fm.; plenty of large Zost.
Bredningen off Klodskov.

4—3"/, fm. No Zost.

21/, fm. Medium long and broad Zost. on mud ground.

Between Hasselø and Kalvø, in Hasselø Bredning.

Ca. 1!/, Fv. Hard ground. Rather short and narrow-leaved Zost.
Flinthorne Reef in N. by E.7/,E.

3 fm. Soft ground. Long and broad-leaved Zost., and Furcellaria.
Flinthorne Reef in N.N.E.

3!/, mf. Soft ground. No Zost.

N.B. The white disc seen at nearly 3 fm. Quiet water, apparently clean
and transparent.

Nysted Church in N.. by N.//.N.

2 fm. Soft ground. Long and broad-leaved Zost.

Inner side of Rødsand at Fugleholm.

3 to a little less than 3 fm. Soft ground. »moss« (Cladophora rupestris,
Furcellaria, Rhodomela etc.). No Zost.

23/,—1!/, fm. Soft ground. Rich growth of long and broad-leaved Zost.
From ca. 1!/, fm. Bare sand ground with a very little Zost. spots outwards.
Skjelby Church in N. by E.//,E., Gedser Harbour lighthouse in S.E.

3 fm. »moss«. No Zost.

23/, fm. Soft ground. Plenty of long and broad-leaved Zost.

N.B. The white disc was tried several times, but could never be seen
at more than 2!/,—23/, fm.

14. Grønsund, Ulvsund and Bøgestrøm.

Skansepynt in Grønsund, Falster side.

2 fm. Hard ground. Short and narrow-leaved Zost.

N. of Skansepynt at the landing stage.

Hard ground. At the edge from ca. 2 fm. and inwards: large, rather narrow-
leaved Zost.; besides Potamogeton pectinatus, Ruppia, Chara baltica and
Tolypella.

Off Farø Jord

Ca. 1//, fm. Rich growth of medium long and broad-leaved Zost.

N. of Tærø W.end.

4—3 fm. No Zost.

2 fm. - Soft ground. Rich growth of medium long, hroad-leaved Zost.

N. of Borren.

4—3 fm. No Zost.

2 fm. Like the preceding.

N. of N. "Knigge.

1!/, fm. Soft ground, Like the preceding.

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61

W. of Lange Grund

2!/, fm. and inwards. The same rich growth. Scattered with Zannichellia
and Chara baltica.

At the S.end of the channel off Stavreby.

1//,—1"/, fm. Like the preceding. A quantity of Chara baltica.

15. The western Baltic.

Olenburg Huk in W. by N. 10 miles.

15 fm. Dead Weed.

Eastern Mærker in N.?/,E.

12 fm. A little brown .Zost.

Nearly N. of Eastern Mærker.

21/, fm. : A little Zost.

S. of Gjedser lighthouse.

3—2!/, fm. Hard ground. No Zost.

Gjedser lighthouse in W.?/,S.

Ca. 4 fm. Hard ground with stones. No Zost.; some red Algæ (»moss«).

Vigersløse Church in N.W.//,W. 4 miles.

41/, fm. Stone ground. No Zost.; the same fine »Moss« (Ectocarpus, Poly-
siphonia, Rhodomela etc.), a little Fucus.

Vigersløse Church in N.W.//,W. 5?/, miles.

6 fm. Bare sand ground with few stones. No Zost.

NB. The white disc seen at 4 fm.

Tromnæs i N.W.//,W.

5!/, fm. Stone ground with delicate Algæ. Some single shoots of Zost.

5 fm. The same. The same.

A little less than 4 fm. A few short and narrow-leaved Zost. A quantity
of Tolypella.

3!/,—3 fm. The red Algæ less numerous, scattered Zost. and Fucus vesic.
21/, fm. Scattered Zost. and plenty of Fucus vesic.

Zost. is of the same kind at all the depths examined.

Off Pomlenakke.

21/, fm. Large, bare places. Fucus vesic. and a little short and narrow-
leaved Zost.

Hesnæs Bay.

21/,—2 fm. Large, bare sandy patches. Like the preceding, but with a
little more Zost. and Zannichellia.

Off the barrel in Bøgestrøm in Faxe Bay.

2 fm. Sand ground with stones. Patches of short, narrow-leaved Zost., Toly-
pella, Chara baltica and Fucus vesic.

In the Middle of Faxe Bay.

6 fm. Sand ground. No Zost.

NB. The white disc seen at 4!//, fm.

Feldskov E. point in N.E. by E. 2 miles.

5 fm. Sand ground with fine red Algæ. No Zost..

3!/2 fm. Stones with Fucus vesic. A few short, narrow-leaved Zost.

62

SMOOTH ae:

Ca. 4 fm. Sand ground. Rich quantities of fine red Algæ and a

narrow-leaved Zost.
5/01. "Faxe in N. by W.3/4W. 3 miles:
At a little less than 4 fm. Fucus and stones.

16. Around Bornholm.

25/. 01. The Bay N. of Salthammer Reef.
Close to land. Sand ground. No Zost.
10/, 01. Zost. grows in small patches at ”/, fm. off Øleaa.

little

11/, 01. At Rønne: Zost. grows im low water in small patches with Potamogeton

pectinatus, Myriophyllum, Ruppia, Zannichellia and Characeæ.

Inside the reef on sand ground, ca. 4 fm., a small quantity of Zost.

(Zost. is not mentioned in all the other reports from Dr. Mortensen's expedition

round Bornholm 1901.)

N. H. Bergstedt (Bornholms Flora, Botan. Tidsskr. vol. 13, 1883, p. 152) mentions

Zost. as »common at the coasts, but not in quantities«.

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