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‘PROCEEDINGS

OF THE.

RovaL TRISH. ACADEMY
| —Vowme XXXI

CLARE ISLAND ) SURVEY

Pare 15

DUBLIN: HODGES, FIGGIS, -& CO. Lap
| LONDON: WILLIAMS & NORGATE. | 1D

an “gre:
Price Five Shillings

_ [For scheme of publication of this series see inside of wrapper] :

and the adjoining mainland in the West of Ireland was carried out bye
one hundred specialists during the years 1909, 1910, ‘and OTE }
undertaken in order to furnish a study of a Born area of the west! ‘coast

baie problems in Europe; and also as a See towards the 2 stud e

island faunas and floras—a subject of wide and absorbing interest.

The report when finished will provide the most complete survey of the.
Fauna and Flora of a definite area which has ever been made. In sada
systematic zoology and botany, special attention has been given to questions
of geographical distribution, dispersal, and ecology, and to the influence’ ‘of
human operations upon the Fauna and Flora. The complete report is
estimated to run to about 1600 pages with 100 plates, and will cost 60/
or more, The whole series may be subscribed for at the reduced price of
50/- paid in advance, on receipt of which the reports issued up to the present i

will be forwarded, and future parts sent as soon as puree ‘Bach Lek ih
will also be sold separately.

the British Isles, and at least 1,000 species new to Tetends.

The list printed on pages 3 and 4 of this wrapper shows the scope 0
work, the present state of publication, and the prices of the ne published

so far. an

publishers or to
Tue SECRETARY

-Rovan

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= UL
aT 7e2r7/e Clare Island Survey.
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MARINE ALGAE.
By A. D. COTTON.
Prates I.-XI.
Read June 24 and Novrwmer 11. Published Novewner 27, 1912.
CONTENTS.
PAGE PAGE
PREFACR, 1} ie The Salt-marsh Formation, . 7
INTRODUCTION, 5 2 y. The Vegetation of River-
1. Definition of the nccak 2 mouths, . $3
2. Previous work in the Area, 2 | . The Vegetation of Brackish
3. Field-work and Assistance, : 4 Bays, : : : - 88
I. Tue Externat ConpiTIONs oF THE )III. Tur Ateat Frora, . ° o 7 AD
AREA, 5 ‘ : 6 1. The Systematic List, ; . 90
1. Climatic Gondificns A 6 2. Notes on the List, . : , 102
2. Physical Nature of the Coast 3. Economic Species, . . 161
and Conditions of Exposure, . 9 4, The Flora of The Bills, . . 165
II. Tue Atcar VEGETATION, . : - 12) Ty. Tue Cuaracter and Composition
1. Historical Résumé, . : =. Le or THE Fiona, : 156
2, Areas and Units of Vegetation,. 14 he Notes on Novelties and Additions, 156
3. The Vegetation, . 17 2. The Character of the Flora, . 160
i. The Rocky-shore Formation, 17 | 3. Comparison with other Areas, . 166
(A) Exposed Coasts, . 19 4. Origin of the Flora,. . . 168
(B) Sheltered Coasts, . 450) yy, Bysniograrny, Bee a ice hoe Wil
ii. The Sand and ae mud
Formation, 3 61
PREFACE

THE natural history Survey of Clare Island and. the adjoining mainland
provided an opportunity of investigating one of the most interesting
algological regions in the British Isles. Since the first decade of the last
century, when Miss Hutchins collected in Bantry Bay, and more especially
since the days when Harvey published his famous “ Phycologia l’ritannica,”
the west of Ireland has always possessed a great attraction for the marine
botanist. But although various collections and many gatherings of new and
rare species have been dealt with, no systematic investigation of that area
has been undertaken, nor has any list or general account of the algal flora been
published. The selection of Clare Island as a centre fora detailed survey was
therefore particularly satisfactory from an algological standpoint. Results

for the systematist and student of plant-distribution were certain, and the
B,1.A, PROC., VOL. XXXI, A 15

NG

152 Proceedings of the Royal Irish Academy.

variety of ground in the neighbourhood provided ample scope for the modern
study of plant-communities. The position of the island—off the coast of
Co. Mayo, and in the Gulf Stream drift—ensured the presence of that
southern element which gives the Irish flora its peculiar interest.

The following report shows that the hopes raised have been amply
fulfilled. ‘I'he flora proved quite as rich as was expected ; and practically all
the species for which the west of Ireland is noted occur within the survey-
area. Valuable systematic results have been obtained; and the variety of
algal associations present rendered the study of the marine vegetation one
of the most comprehensive that has yet been carried out. Important
phytogeographic data also, necessitating the modifying of previous views,
were secured.

INTRODUCTION.
1.—DEFINITION OF THE AREA.

Owing to the comprehensive nature of a natural history survey, the
limits of the area investigated varied in different cases, since in some it was
advisable to include a much larger area than in others. . With regard to the
marine algae, it was thought best to limit the investigation to Clare Island
and the neighbourhood of Clew Bay. By concentrating attention on a small
district a more accurate knowledge of the true nature of the vegetation can
be obtained, and the variety of ground presented in the area mentioned
proved quite as much as was possible to work with a moderate degree of
thoroughness.

The Survey-area for the algae, therefore, consisted of Clare Island, the
shores and waters of Clew Bay, and an extension to the north to include
Bellacragher Bay and Achill Sound. S

At the same time it appeared advisable not to overlook the interesting
records from Roundstone, a locality only twenty-five miles south of Clew Bay.
This district was carefully worked some seventy years ago by W. McCalla,
and he collected several species which were not found in the Clare Island
district. A brief visit was paid to Roundstone; and all records from that
locality are included in the report.

2.—PREVIOUS WorK IN THE ARFA.

According to the scheme of geographical areas devised by: Adams (see
Adams, ’11, in Bibliography) the province of Connaught is divided into three
sub-divisions. Co. Mayo (which includes the survey-area proper) forms sub-
division C 2, and, according to an annotated copy of Adams’ Synopsis (Adams,

Clare Island Survey—Marine Algae. 15 3

‘08), kindly sent me by the author, possesses thirty records of algae. Co.
Galway, on the other hand, which forms sub-division C1, has a much longer
list, owing to the collections made at Roundstone Bay. For the third sub-
division, C3 (ie., counties Sligo and Leitrim), there are practically no records.

With regard to sub-division C 2, Wm. Thompson, the zoologist, collected
a few plants in Clew Bay about 1840; and Harvey quotes one record—
Asperococcus bullosus—in “ Phycologia Britannica.” In a report of a natural
history excursion to Achill at Easter, 1898, H. Hanna deals with the marine
algae (Hanna, 98). He records twenty species; and this constitutes the only
account of the sea-weeds of the area. Adams, in his list, adds nine names to
the flora of the sub-division, culled from various sources. A single species
has been recorded from Clare Island, namely Codium tomentosum (vide
H. H. Dixon, Ann. Bot., xi, p. 590).

The Roundstone records date from 1808. Fucus Mackaw was described
from that locality by Dawson Turner (“ Historia Fucorum,” Pl. 52); and it
still remains one of the few stations for the plant in Ireland. In addition to
the discovery of this species, Mackay noted the presence of &hodochorton
floridulum, which Harvey mentions in the chapter on algae in Mackay’s
“Flora Hibernica.” McCalla’s records follow. He thoroughly explored the
shore, and supplied Harvey, as the pages of “ Phycologia Britannica” testify,
with much valuable material both from Roundstone Bay and Birturbuy Bay.
McCalla was also one of the pioneers of dredging amongst algologists, and by
this method he obtained many interesting species. He commenced to issue
a set of “ Algae Hibernicae,” but, owing to his untimely death in 1849, only
two volumes were published. Harvey visited Roundstone at least once, and
in later times, Johnson (93) and H. Hanna. Fosle also, the well-known
specialist on calcareous algae, came over from Norway on purpose to
investigate the Lithothamnia which had been described from Roundstone by
McCalla and Harvey. An account of his trip was published in the “Irish
Naturalist ” (99, p. 175). Foslie was keenly interested in the Lithothamnia
of the British Isles, and it was proposed to send him for identification all the
Clew Bay material. His premature death in 1910 came as a great shock.
Three days were spent by me at Roundstone in September, 1911, and, with
the exception of Codium amphibium, all the species for which that locality is
famous were seen in their natural habitat. The total number of species listed
by J. Adams for the sub-division C 1 is 162.

Outside the province of Connaught, Valencia Harbour (in the extreme
south-west) has been specially investigated by biologists, and Weiss, who dealt
with the algae [’00], gives a list of eighty-six species collected by him during
August and September, 1896, with notes on the same.

A 2

Qe

15 4 Proceedings of the Royal Irish Academy.

3. FIELD-WoRK AND ASSISTANCE.

My visits to the Survey-area extended over three years. In each year two
visits, varying from a fortnight to three weeks, were paid to the island and
mainland, whilst during the last year, an additional winter visit was
accomplished. Owing to the uncertainty of communication, no attempt was
made during this last trip to cross to the island, but since the conditions of the
exposed mainland are similar to those of Clare Island, a fair idea of the winter
aspect of the vegetation of the whole area was obtained. In_ addition,
Mr. J. Adains, of the Royal College of Science, Dublin, visited the district in
August, 1909, investigating the island and dredging in Clew Pay.

The dates of the visits were as follows :—

1909. April 8-20; July 12-27. [August 20-27, J. Adams. ]
1910. June 16-July 1; September 50-October 15.
1911. February 15-21; April 28-May 15; August 17-September 4.

About one-half the time of each trip was spent on the island, and the
remainder either on the mainland or in dredging. Spring-tides were usually
selected for the former locality, when exposed or semi-exposed shores were
examined at low-water. As is well known, spring-tides are more useful in
sheltered regions than in exposed, and a greater number of rare and sub-littoral
species are doubtless uncovered during springs in Clew Bay than on Clare
Island. But since these can readily be obtained by dredging, there was no
object in reserving low-tides for mainland work.

Dredging was carried out in February, May, July, and August. Tor the
more open waters I had the advantage of the ss. “ Helga,” of the Fisheries
Branch of the Department of Agriculture and Technical Instruction for
Ireland. The outer part of Clew Bay was explored, and a number of hauls
were taken further out, ie., to the south and west of Clare Island, and near
The Bills, in depths ranging from 10 to 20 fathoms. A large amount of
material was collected, and considerable light obtained as to the nature of
the benthos, but for detailed study much longer time than was at my disposal
was necessary. J. Adams also dredged from the “ Helga” in 1909, and two
interesting algae were found only on that occasion.

For the inner part of Clew Bay a small sailing-boat was used: and good
work was accomplished by means of a hand-dredge in 1-6 fathoms. The
“coral-banks” were investigated, and in quiet weather very much may be
learned as to the nature of the flora. The February dredgings were useful in
obtaining fruiting specimens of encrusting algae. In May the mass of
vegetation is so great that it is impossible to do more than sample various
localities. As the hauls ot July, 1909, had provided several rare and interesting

Clare Island Survey—Marine Algae. 15 5

plants, a few days were set apart in August, 1911, to search for note-
worthy absentees. Rough weather, however, set in, and dredging from a
small boat was out of the question.

With regard to the nature of the field-work, the visits of the first year
were mainly devoted to the listing of species from all parts of the area, and
to working out critical forms. The same study was continued in 1910, and
the analysis of algal communities was also taken in hand. The third year
was principally devoted to the search for species which were to be expected
but had not been found, and to the completion of the work on algal
communities. On each visit, moreover, a large amount of materia! was
collected for the Royal Botanic Gardens, Kew, as some extra leave had been
granted for that purpose.

The time devoted to ecology necessarily robbed the systematic list of a
certain number of names. Searching for rare or microscopic species
invariably yields results in the way of new or little-known plants, but the
records of minute species, such as Cyanophyceae, are not yet of much value
for comparative purposes. Moreover, the amount of time and labour spent
in working out microscopic forms is often very great, and out of proportion
to the results obtained. Unfortunately there was no specialist for the
Cyanophyceae (which are abundant in brackish parts of Clew Bay) who could
be appealed to for aid.

The list, therefore, can hardly be considered as exhaustive. With regard
to the littoral flora, the island-list must be fairly complete; and on the main-
land the additions during the last trip were chietly microscopic forms. — But
in the sub-littoral region there are probably many species yet to be discovered,
as the vegetation is very local and less easy of exploration. The fact that
such conspicuous weeds as Dictyopteris, Acrothrix, Dasya corymbosa, and
several others were only seen once, confirms this view.

Assistance.—Dr. P. Kuckuck joined the collecting party during June,
1910, and advantage was taken of his critical knowledge of the Phoeophyceae
to work out Ectocarpi, Chordarieae, &c., and to make comparisons between
the flora of the North Sea and Baltic, and that of Clare Island.

In April, 1911, Dr. F. Borgesen paid a visit to the Survey-area. Naturally
the vegetation of Clare Island had been continually compared with the
detailed account given by him for that of the Faerées, and several striking
contrasts had been noted. It was, therefore, of the greatest value to be able
to examine the algal associations with Dr. Borgesen, and to discuss the
problems that had arisen. His help also with regard to the Iceland flora was
particularly useful.

In order to make the floristic section of the work as accurate as possible,

15 6 Proceedings of the Royal Trish Academy.

which for comparative purposes is of the very greatest importance, I
have availed myself freely of the help of specialists. Dr. Kuckuck kindly
worked out the Ralfsiae, and checked a number of other members of the
Phoeophyceae. The weight of his authority in doubtful cases was most
valuable. I am also much indebted to Dr. M. Lemoine. Since the death of
Foslie, the identification of encrusting Lithothamnia was uncertain work,
owing to the confusion in the literature, and the scarcity of reliable material
in British herbaria. Madame Lemoine willingly undertook to examine the
Trish material, and, by her method of anatomical investigation, to work out
and compare critical species with authentic specimens. Though no important
additions to the list have resulted, it is highly satisfactory to have trust-
worthy identifications. An interesting point with regard to geographical
distribution has, moreover, been cleared up by her. Dr. K. Rosenvinge kindly
determined the Chantransiae, whilst Prof. N. Wille, Prof. C. Sauvageau, and
Dr. H. H. Peterson examined the species of Ulothrix, Spacelaria, and
Ceramium respectively. Prof. G. 8. West’s opinion on the brackish and
freshwater species, and Mr. J. Adams’ aid in connexion with the distribution
of Irish plants were most helpful. Mr. E. M. Holmes has taken the keenest
interest in the Clare Island flora, and throughout the work of identification
has always most liberally bestowed the benefit of his valuable and unique
experience. ‘I’o all these botanists I offer my sincerest thanks. Special
acknowledgments are due to Mr. R. Lloyd Praeger, the organizer and
secretary of the Survey, to whom I am deeply indebted for advice on matters
botanical and geological, as well as for encouragement and assistance in a
number of ways.

I.—THE EXTERNAL CONDITIONS*‘OF THE AREA.
1.—CLIMATIC CONDITIONS.

1, Atmospheric Temperature und Moisture.—The insular climate of Ireland,
and the influence of the Gulf Stream drift, combine to render the Clare
Island district particularly mild and damp. In winter rough stormy weather
prevails, together with a large amount of rain, but frost is rare. In summer
the weather is changeable, rain and gales from the south-west are frequent,
and the average temperature relatively low. Though occasional warm days
occur, spells of het dry weather are most unusual; and this renders the
intertidal region more favourable for vegetation than that of the south coast
of England. A glance at the isotherms of Europe shows that the mean
January temperature of 45° F. (=6:11° C.) corresponds with that of the south
of France and the north of the Adriatic; whilst the July isotherm of 58° F.

Clare Island Survey—Marine Alyac. 15 7

(= 1444°C.) runs up the coast of Norway, across the north of Sweden to
northern Russia and Siberia. Clare Island is situated on the same latitude
as Heligoland and Kiel, but, as will be seen later, the flora is of a very much
more southern type.

The atmospheric moisture is of importance in connexion with the littoral
vegetation. But the problem of desiccation during low water is a very
complicated one, the latitude, together with the amount of wind and sunshine,
having to be taken into consideration. The following figures (“Irish Coast
Pilot,” ed. 6, 1911) give the mean humidity for the Blacksod Point
Observatory for the last thirty-five years. It will be noted that the highest
figures are those of the winter months, whereas in the Faerées the reverse is
the case, for which the absence in Ireland of summer fogs is probably
responsible :—

| Jan. Febr. | Mar. | Apr. | May. | June. | July. | Aug. | Sept. | Oct, | Nov. Dee. |
PESSmricSi le SG: o|seSban|i SI
oul

Nore.—Observations made at 8 a.m. 100 = Saturation point.

| | |
sl | 84 S5)))| 784 SL | ee | oe

2. Temperature and Salinity of the Sea.—Important as are atmospheric
conditions, the temperature of the water is even more intimately connected
with the algal vegetation. The direct influence of the former is confined to the
intertidal region, and is thus intermittent; but the effect of the latter is much
more general, being felt both by the littoral and sub-littoral flora. A complete
series of observations on sea-temperatures at different depths is not available
for Clare Island ; but the Meteorological Office has favoured me with details of
the mean monthly surface-temperatures for Blacksod Bay and Cleggan during
the year 1911; and Mr. G. P. Farran has kindly supplied me with two sets of.
temperatures and salinities for various depths in Clew Bay and off Clare
Island. From these it is evident that the surface temperature does not differ
much from that of 10-20 fathoms, so that the monthly table given below
affords a good general guide. The Blacksod and Cleggan observatories are
about twenty miles north and south respectively of Clare Island. It will be
noted that many of the Blacksod figures are slightly higher than those of
Cleggan, for which local topography doubtless accounts :—

MEAN SURFACE TEMPERATURE, BLACKSOD AND CLEGGAN, 1911. (C°).

Teer hates eae ean

| | Sar: | Febr. Mar. | Apr. | May. | June. | July. | Aug. | Sept. | Oct. | Nov. | Dee.
| ——_—_-—_} |————__—— — — A
|

| Blacksod,| 7-2 | 6-7 | 6-7 | | 17 | 13-3 | 161 | 161) 13:3
6 |
|

8
| }
Cleggan, 72 | 67 67 | 83

10°6 | 7:2 67
10°6 | 7-2 5-6

11-1 | 12:2] 13-3 15:0 | 13:9 |

15 8

Proceedings of the Royal Irish Academy.

CLARE ISLAND, May, 1909.

i Surface. | 1-10 fathoms. 11-20 fathoms. |, 21-30 fathoms.
4 — |
Station Number. Date. | | | |
I Temp; | Sal. °/, | Temp.°C. | Sal. °/, || Temp.°C. | Sal. °/, || Temp. °C. | Sal. °/,
———- + -- —_—-- | sl Fide 4 —— =
Clare Island W. 67, 21.5.709 | 11°15 34-61 SS — | (10-69 34-6401]
| (20 fath |
W. 69, | 22.5. 09 |) 11°35 | 34-60 = — |.. ==) °) = ipa Sie
| | ( 24 fath
. W. 70, . | 11°30 | 34-61 = de pane 34:67 || =
| | | (18 fath. |
\ } |
5 W. 72, ” 113 | 84°69 | (11-28 | 84-72 | — = he =
| ( 9 fath. i
| I
; W. 75, | 24.5. 709 || 11-0 | 34:74 = = ee | 34°72 | (10°55 | 84-72
| 12 fath. | {35 fath.
; W. 81, | 25.5. '’09|| 11-05 | 34-70 | eee | 1h 10:87
| | | ( 26 fath
en MaeAWWE.82; - Ici aarogle e || ee eae a =
| | |
CLARE ISLAND, AuGustT, 1911.
er oe Laare ester eet Rn eo nie, | i
Clare Island W. 197, 18.8. ’11 || 17-40 | Bei fp = | = ae 340720 =
| \| | | 18 fath,
| \
“4 = - | 16:96 | 34:54 | ¢ 16-12 32-560]! hl ee we
{3 fath. |
P — | 20.8.°11 | 17:77 | 34:42 |} ! Ee.
» .- 3) 17°94 | 34:42 | — = = ash Ss. =
‘ = $ 18:05 | 34:31 = = =
Fr a i | 18-25 | 8429 || — = ie: ee ee.
| |
+ sowieen |(feel7-92 aly eBaz29 pal. See = ¥ “ ue ia
xm 21. 8.711 || 16°92 | 34-51 || — ae ae a 2
De nwa 205, “ | 16-68 | 34°67 = a8 fed — |ijises | =
| | | 22 fath
|
br W. 206, * | 16-67 | 34-79 — ||(14-00, | @4588
Resi. |
The Bills W.207,/ ,, 16-88 — = = = — (1848 | —
i | | | 95 futh.
” W. 208,/; | 16°91 | 34-78 = — = = Fie 34:97
| 126 fath.
Clare Island W.210,/ ,, | 16-98 | 3463 | = — SS iqaaete | = a
3 | | 120 fath, | |
| | ' | |
Clew Bay W.216,) ,, (| 17-74 | 34-42 || — =: = = } =
| | | |
Clare Island W. 222, | 22. $. 711 | 16-34 34°78 | — — 14:94 34°79 || ( 13-96 34°88
| | | | | {17 ath. er fath. |
| | | {| | |
Clew Bay W. 228, / 23.8. 11 | 17-25 | 34°67 || = — | a = xt
2 W. 230, H) 16:96 | 34°47 ~ {| = | = = bast a

Clare Islund Survey—Marine Algae. 15 9

(8) Tides and Currents——The presence of a good ebb and flow on Clare
Island gives a wide intertidal region for shore-collecting. At Westport
Quay the rise and fall during spring-tides is about 15 feet, and in April
and September 16 feet 6 inches, whilst with neap-tides there is a rise of
12-13 feet. On Clare Island the range is, if anything, greater. Low water
at spring-tides is in the middle of the day. In certain spots (i.e. between
the islands in Clew Bay and at Darby’s Point, Achill Sound) there is a strong
current, and the vegetation is of a different character from that found in other
parts. Ballacragher Bay, owing to its narrow opening, has but a small
‘tide—not more than 5-6 feet—except during springs.

2, PHysicAL NATURE OF THE COAST AND CONDITIONS OF EXposuRE,

Our district presents great diversities in the physical nature of the shore ;
and in describing the same it will be both convenient and natural to divide
it into two areas, viz. (1) Clare Island, and (2) the mainland. Speaking
generalky, the island presents an exposed. rocky coast, whilst the mainland
consists of sheltered ground. In view of the possibility of future work in
the neighbourhood, a detailed account of the coast-line is given.

(1) Clare Island.— With the exception of the bay near the harbour and
a few sandy patches elsewhere, the whole shore is rocky and cliff-bound.
Taking the different parts of the island in order, we find that on the south
side the rocks are composed of Silurian slate, which forms flat slopes where
the beds lie more or less horizontally, but which is very sharp and rugged
where the strata are upturned. Rock-pools, narrow gulleys, and deep
channels are frequent, and these were found to be useful, as this part of
the shore is as a whole somewhat rough and exposed for general collecting,

The eastern end of the south shore, and from the corner of the bay
to Kinnacorra, is composed of Carboniferous sandstone, a formation found to
afford excellent collecting-ground. Various degrees of slope and exposure
are presented; and towards Kinnacorra there is a fine series of flat rocks
and a number of shallow pools. The Carboniferous sandstone is continued
to Portlea, a semi-sheltered bay on the north-east side of the island. A
boulder-beach surmounts the upper part of this bay; and the rocks below
are flat, with a vegetation somewhat different from that found elsewhere.
Further north, towards the lighthouse, the slate is again in evidence; and
here caves and vertical surfaces, receiving little direct sunlight, are found,
and several shade-loving species appear in the open. Though bounded by
cliffs, the shore at this point is easily accessible. The fine stretch of cliff
on the north-west side of the island is for the most part precipitous, and
the narrow strip of shore below is very exposed and difficult of exploration.

B,L,A, PROC,, VOL, XXXI, B 16

15 10 Proceedings of the Royal Trish Academy.

In certain spots it is possible to descend to sea-level, which is found to be
strewn with large, irregular blocks and boulders. Little seaweed vegetation,
however, occurs. On the cliff, colonies of sea-birds provide the conditions
which favour a vigorous growth of Prasiola stipitata.

With regard to exposure, Beetle Head (or Kinatevdilla) and the shore below
the north-west cliff are open to the ocean, and feel the full force of the
Atlantic rollers. The south side is open to the sea from the south-west,
and is also very exposed; but it is not subjected to quite such boisterous
conditions as is the north-west side. Owing to the prevalence of south-
westerly gales, the exposure on this shore must, however, be very severe.
A bend at the eastern end towards the castle affords some protection, as
evidenced by the change in the character of the Fucus growth. The sandy
bay near the harbour, which faces east, provides the only sheltered shore on
the island, and a few sand-loving species are found at the northern corner.
Beyond the bay, the stretch of rocks leading to Kinnacorra is subjected to
moderate wave-action, and on the whole the conditions are semi.exposed.
At Alnahaskilla (beyond Kinnacorra) greater exposure is met with, owing
to the sea coming in from the north; and for the same reason all points
along the north-east side are subjected to rough water, though a certain
amount of shelter is found in the intervening bays and inlets. In a general
way the north-east shore is decidedly more protected than the south, but less
so than Kinnacorra.

(2) The Mainland.—When investigating the mainland, it was the usual
practice to begin at Roonah Point, at the south-west corner of the Ciew
Bay, work round to Mulranny on the northern side, and then proceed to
Achill Sound and Bellacragher Bay. In describing the ground it will be
convenient to follow the same order. :

Roonah Quay faces west, and the rocky shore of Silurian slates at
the point is subjected to the same exposed conditions as Clare Island.
To the south there is a long stretch of boulder-beach, but the presence
of rocks in shallow water provides shelter, and there is a certain amount
of fairly good collecting-ground. At the point itself, small bays and
caves with partial shelter occur. Turning the corner into Clew Bay the
exposure rapidly decreases, and between this point and Bartraw there is
a series of beaches composed of rocks, boulders, or sand. The surf-loving
Nemalion is found as far in as Old Head, where steep rocks and rough
water occur for the last time; shallow water then sets in, and there is
much sand. When the islands of the bay are reached, the tide recedes
for a long distance, and a certain amount of mud begins to appear, but in
several spots a luxuriant littoral vegetation exists.

Clare Island Survey—Marine Algae. 15 11

Many of the islands provide flat beaches of sand and stone with good
collecting-ground at low water. At Annagh Island there is a salt-marsh.
The Bunowen river at Louisburgh, the stream at Belclare, and the rivers
at Westport and Newport give brackish and fresh-water conditions. In
the innermost part of the bay there are wide stretches of mud, and_ the
ground is very poor; with the exception of hasty imspections near Westport
and one day at Newport, it was but little explored. The northern side
consists largely of sand. At Mulranny there are strips of salt-marsh,
also fresh-water and brackish streams. The peninsula of COurraun
Achill follows, with a rocky shore of Old Red Sandstone and exposed
conditions.

The floor of Clew Bay is everywhere soft, consisting of sand with stones.
In spring and early summer there is a rich and luxuriant sub-littoral vegeta-
tion, which in shallower parts may be easily studied from a boat, or hauled up
by a hand-dredge. Banks of Lithothamnium occur, and there are numerous
Zostera beds. Between the outer islands, channels with a swift current, where
the bottom is usually stony, are frequent.

Achill Sound, easily reached by train trom Mulranny, provides perfect
shelter, and yet fully saline conditions. At low water, the Sound becomes
dry, exposing a large stretch of sand. The water enters from both the north
and south, and at the end of the ebb-tide the parting of the streams will be
observed to take place at a point about a quarter of a mile south of Achill
Bridge. The vegetation is for the most part poor, especially in the summer ;
but channels provide good ground, and the stones set out by the peasants
yield a fine crop of Fucus. Further south (towards Achillbeg) there are
swift currents and deeper water, and here a marked increase in the
luxuriance of the vegetation is noticeable. On the north side of the bridge
there is much mud; but the peat banks flooded by the tide offer some in-
teresting types of plant-associations. Bellacragher Bay, a lough-like inlet
surrounded by high hills, ditfers from Achill Sound in possessing deep water,
and being less tidal. It is connected with the sea (Blacksod Bay) by a
narrow opening at the north-west corner. Several streams descend from the
hills; and owing to the water only partly escaping on the ebb, the whole
bay must be often more or less brackish. Some samples taken at the end
of the dry summer of 1911 showed, however, almost normal salinity. - The
littoral region is narrow, and composed of stones or rock. The bottom
appears to be rocky, since a vigorous belt of Laminaria is disclosed at low
water.

B2

15 12 Proceedings of the Royal Irish Academy.

Il. THE ALGAL VEGETATION.
(1) Historica, Resumé or Previous Work.

As the present paper forms the first detailed account of the algal associa-
tions in any area in the British Isles, a general introductory sketch of the
subject may be useful.

Kjellmann’s papers on the algal regions and formations of the Murman
Sea (77) and the Skager Rack (78), form the starting point of the modern
method of studying algal communities. Kjellmann divided the vegetation
into three “regions,” and these he further divided into a number of “ forma-
tions,” which were characterized by a distinctive vegetative facies, due to the
predominance of one or more algae.

The main outlines of Kjellmann’s classification have been accepted by
subsequent writers, though of late years changes in terminology and great
elaboration have been noticeable. One of the earliest attempts to apply
Kjellmann’s methods of study to other countries is contained in a paper by
Rattray (’85). The paper, which is a biological and ecological account of the
algae of the Firth of Forth, is seldom referred to, though it was apparently
the first and, until quite recently, the only one of the kind dealing with an
area in the British Isles.

In other countries, however, this branch of ecology has received more
attention. The Norwegian algal vegetation has been studied by Hansteen
(92), Gran (93), Boye (94-95), and Kylin (10), and an account of the
Faerdese algae was published by Simmons (99). The Greenland marine algae
have been thoroughly studied by Rosenvinge, who, after giving two systematic
accounts, furnished a paper dealing with the algological communities (99).
The marine algae of the Baltic have been investigated by Svedelius (01),
who, in his “ Osterjons Hafsalgfiora,” devotes a chapter to the algal regions
and formations found under the peculiar conditions presented in that area.
The question of defining the algal regions in the non-tidal Baltic had also
been dealt with by Reinke (89). he algae of the Faerdes have been
described a second time in the, “ Botany of the Faerdes”; and Borgesen’s
treatise “The Algae Vegetation ” (’05), which followed his systematic account,
is the most important contribution to this branch of algological literature.
Kylin, in his algal flora of the west coast of Sweden (’07), deals with associa-
tions and other ecological problems at some length. Joubin (’09) described
the marine communities at Roscoff, and published an elaborately coloured
vegetation-map. The map will be most useful to students working in the
locality ; but floristic and ecological data are at present somewhat scanty for

Clare Island Survey—Murine Algue. 15 13

comparative purposes. For the Adriatic, we have Tecket’s general account of
the algal vegetation of Trieste (’06). The Iceland marine algae are the latest
to receive attention from the ecological standpoint, Jénsson’s work (10)
forming a useful addition to his systematic papers which appeared previously.
Outside Europe, Syedelius’ paper on the periodicity of algae in Ceylon coral-
reefs (706), Skottsberg’s work in the Antarctic (06), and Borgesen’s accounts
of the algal vegetation of the Danish West Indies (00, ’01, ’11) are
apparently the only papers of the kind which have appeared ; but reference
should be made to Weber van Bosse (04), and Schiller (?09), which border on
the subject. :

Turning to the British Isles, with the exception of Rattray’s paper referred
to above, no account of the algal communities found on our coasts has
appeared, though, as will be seen later, a certain amount of autecology has
been done. The numerous and important additions to the British algal flora
recorded by Mr. E. M. Holmes and by the late Mr. E. A. L. Batters, have kept
our knowledge of the flora well up to date as far as its purely systematic aspect
is concerned. Ecological factors, too, were not disregarded, the “ habitat ”’ of
a species having been always given a prominent place by British writers; so
much so, that in a few cases the specific distinction of similar plants has been
strongly advocated on the ground of a difference in habitat. Casual reference
to the “Fucus-belt,’ “Coral-banks,” and “ Laminaria-zone,” shows that the
more obyious associations were not overlooked.

Rattray (85) treats at some length of the size of individuals when gathered
from different localities and from different levels; he also deals with various
problems connected with the distribution and development of the spores.
With regard to algal communities, he recognizes the “regions” of
Kjellmann, and describes a number of “areas” (“ formations” of Kjellmann)
characterized by the presence of certain dominant species. His “areas,”
whether littoral or sub-littoral, are classified almost entirely with reference
to vertical distribution, and there is no attempt to connect them with other
conditions such as exposure and desiccation. This results at times in a
curious association of names in a given zone, and renders the account some-
what obscure to anyone not familiar with the exact topography of the
locality. The paper is, however, full of facts, and will be of great interest
and value to the next investigator of the algal vegetation of the Firth of
Forth.

In a memoir on Chondrus crispus by Darbishire (’02), the general ecology
of the plant is dealt with, and incidentally reference is made to the principal
zones of vegetation that occur on the shores of the Isle of Man, Two

15 14 Proceedings of the Royal Trish Academy.

interesting ecological papers by Miss S. M. Baker have lately appeared (09, 10),
in which experiments, with a view to determine the causes which bring about
zonation, are described ; but the general question of algal associations is not
touched upon. The ecology of Ulva Laetuca has been discussed by me at ~
some length in a report to the Royal Commission on Sewage Disposal (’11 4).
The subject of plant-communities was not in view, but the presence of a
distinct mud-formation and an Ulva-association, though not stated in words,
was Clearly demonstrated. N. H. Johnson has furnished two notes dealing
respectively with the mapping and nomenclature of marine vegetation
(lil, 71%).

An account of the algal associations of a definite area in the British Isles
was thus urgently needed, and in the Clare Island investigations this study
was given a prominent place. It will be noted that in several of the works
referred to, the systematic account was published first, and the ecological
treatise appeared later. This order of investigation is essential. The flora

must be thoroughly mastered, before the groupings of the species can be
accurately studied.

(2) THE AREAS AND THE UNITS OF VEGETATION.
A. The Regions.

Kjellmann’s term “region” has been generally adopted by algologists ;
but the limits of the three vertical divisions included under this term are
variously accepted. In the present account they are taken as under :—
The littoral region extends from the level of the highest marine vegeta-
tion to that of low-water mark at neap-tide. The swb-littoral begins from
the lower limit of the last-named, and extends down to the limit of sea-
weed vegetation (ie, about 25 fathoms). The clittoral region follows,
and being devoid of algal vegetation, is of no importance in the present
paper.

The reasons for so defining these regions are as follows :—With regard to
the upper limit of the littoral region, this, according to Kjellmann, com-
menced at the highest tide-level; but, as several writers have pointed out,
the algae on exposed coasts often extend far above the-spring-tide limit. A
separate region—the supra-littoral—has been suggested by Lorenz. Borgesen,
however (’05), showed that no hard-and-fast line can be drawn between the
vegetation of the supra-littoral and littoral, and for this reason he did not
recognize the area as a definite region. In Clare Island the supra-littoral
vegetation, though often found, is of less general occurrence than, for
instance, in the Faerdes. It is largely due to the presence of spray (a factor

Clare Island Survey— Marine Algae. 15 15

which is regulated by the exposure and he of the rocks), but shade and
terrestrial moisture are also important. The associations, moreover, found
in this area are the same as those in the upper part of the littoral region, and
often merely extensions of them. I therefore agree with Borgesen in not
regarding it as a separate region.

With regard to the lower limit of the littoral area, on exposed coasts the
low-water mark at neap-tide is certainly the natural line of demarkation.
At the same time, on a calm day during spring-tides, the Laminaria and
Alaria growth may be exposed, and become dry for a short time; but this
is obviously exceptional. On sheltered shores the boundary-line is not
so clearly marked; and it is difficult to define the beginning of the sub-
littoral vegetation. In Clew Bay it is particularly perplexing; and the
flatter the shore, the less marked is the boundary. As time did not allow
of special work on this point, the lower limit of the littoral region has
been made uniform with that on exposed coasts—namely, the ebb-mark at
neap-tide.

B.—The Formations and Associations.

A good deal of confusion exists with regard to the terms ‘ Formation’
and ‘ Association.’ Kjellman first introduced the word ‘ Formation’ into
algological literature in his paper on the algological communities of the
Skager Rack (78). He describes an algal formation as a small portion of
the whole algal vegetation which is distinguished by a characteristic
“ Vegetations-Gepriige,” adding that in a general way these portions of the
vegetation obtain their characteristic stamp through one or more algae that
predominate. Most other writers have followed Kjellmann’s nomenclature.
Tt is, however, more in accordance with the terminology now generally
employed to use the term ‘association’ for these communities, and to
reserve the term ‘formation’ for communities which occur together in a
definite type of habitat. The substitution of the former term for the latter
was first put forward by Boérgesen (’05), and the name ‘formation’ was
at the same time employed by him for “associations when united together
under the same or nearly the same ecological conditions.” Examples
of Borgesen’s formations are the Chlorophyceae, the Fucaceae, and the
Laminaria communities of exposed coasts. Kylin (07) does not follow this
nomenclature, but adheres to the term ‘formation’ with the meaning
attached to it by Kjellmann. Jonsson (10), on the other hand, follows
Borgesen.

Borgesen’s use of the term ‘association’ is certainly more correct; but the

15 16 Proceedings of the Royal Irish Academy.

larger communities for which he employs the name ‘formation’ appear to
represent groups of associations rather than formations. The term ‘forma-
tion’ if used to correspond with ‘salt-marsh formation,’ or ‘sand-dune
formation’ of phanerogamie botanists, would be more properly applied to the
vegetation covering such areas as exposed rocky coasts, or sheltered muddy
shores. These might indeed be called ‘subformations’ by some botanists,
in which case the whole marine flora would form one formation—the
‘salt-water formation.’ This, however, is hardly justifiable, and there
appears to be no reason why the term ‘formation’ should not be applied
to the principal types of the marine vegetation, as well as to the sand-
dunes or peat-moors that occur above them.

In the present state of our knowledge it is difficult to define these
marine formations; but notwithstanding this I have ventured to use the
term for the vegetation covering the principal types of ground that occur
on our shores. The formations proposed are three in number :—

1. The rocky-shore formation.
2. The sand and sandy-mud formation.
3. The salt-marsh formation.

All three are represented in the Clare Island area, and in addition two
other types are distinguishable, which are dealt with under the heading
of—

4, The vegetation of river-mouths.
5. The vegetation of brackish bays.

Each of these five types of vegetation consists of a number of associations,
and the latter may frequently show natural groupings. But the associations
found vary considerably in different localities, being influenced perhaps
most largely by the factor of wave-exposure.

It should be clearly understood that the classification suggested above
makes no pretension to be final. It is possible that the rocky-shore
formation will have to be divided into other formations; but, judging from
general field-work in many parts of the British Isles, this does not appear
very probable. The flora certainly varies with the nature of the rock,
but the changes consist in the modification or re-arrangement of the associa-
tions, rather than in any profound alteration in the plant-formation. The
general plant-covering of all rocky shores (including chalk) appears to
be of the same type; and for this reason it is here regarded as a simple
formation, though further work will doubtless show many differences in
detail,

Clave Island Survey— Marine Algae. iba) a

The distinction between associations and societies is more puzzling
Many of the small communities that have been described by various writers
appear to represent societies (as understood by Tansley and Moss) rather
than associations; caution, however, is needed, as definite zonation is
discernible in one locality, whilst in others the growth is patchy and discon-
tinuous. For this reason I have adopted a conservative attitude in the
present report, and have used the term ‘association’ instead of replacing it
by that of ‘society.’ In the case of communities described for the first
time, when the status was doubtful, a non-committal expression has been
‘used. The whole question of transient societies requires careful working
out. Many algae appear periodically, and of these some are short-lived,
being conspicuous only for a few weeks, whilst others require six or eight
months to complete their life-cycle. It is clear, therefore, that before the
status of these communities can be settled, a more complete knowledge of
the seasonable range of many species is needed, as well as a more detailed
analysis of the vegetation.

3.—THE VEGETATION OF THE AREA.
i—The Rocky-shore Formation.

The rocky-shore formation embraces every form of hard ground, from the
exposed rugged slates of Clare Island, to the flat low-lying sandstones of
Clew Bay. Great variety in slope and exposure is met with, and also in the
surface and hardness of the rock. Speaking generally, the formation is
characteristic of open shores. In exposed localities it is the only one to be
found. On sheltered shores it is not infrequently poorly developed, or
replaced by the sand-and-rock or sandy-mud series. A characteristic feature
is the strong basal disk by which the plants are attached, this being true
both of exposed and sheltered coasts. Some of the smaller species have,
however, other methods of attachment, as explained later. The vegetation of
boulder-beaches is included in the formation, and also that of more or less
buried rocks and stones, though, in the latter case, the vegetation clearly
approaches that of sand-and-rock (pp. 65-67). The pebble-attached association
of quiet bays, being characteristic of a soft bottom and not of rock, is placed
pro tem. under the sand-formation.

The associations differ markedly according to the amount of exposure, and
two series are to be recognized—namely, exposed and sheltered. The littoral
and sub-littoral vegetation must also be distinguished ; but, except for these,
no further sub-division has been attempted. ‘The hardness of the rock, and

k,1.A. PRGC., VOL. XXXI- C 15

15 18 Proceedings of the Royal Irish Academy.

the degree of slope intluence the vegetation, as does also the nature of the
rock-surface ; but, as stated on p.16, this produces merely a change in the
associations, rather than a fundamental difference in the plant-covering.
Boulders may be singled out for notice, since their vegetation is peculiar and
well marked. The associations on a boulder-beach are much broken up, and
secondary series on the vertical faces of the rock are of general occurrence
(see Plate II). The tops of the boulders are usually bare, owing probably
to immediate escape of the water, and to extreme desiccation, which
prohibit respectively the retention and development of spores. Points such
as these continually present themselves when studying the communities,
and several are noted in the report; but it is too early to offer generaliza-
tions.

A word may be said as to methods of attachment. In addition to the
stout disk typical of the formation, three are distinguishable. In the case of
simple filamentous species such as Bangia, Urospora, and Ulothrix, each
thread is fixed to the rock by the basal cell, with or without the assistance
of corticating filaments. Hence the association, which consists of many
thousands of minute plants, does not require a rough surface, but occurs also
on smooth rocks where other species obtain no footing. It is in reality
attached along its whole base. The second type is that of Ceramium
acanthonotum, which possesses rhizoids. Such plants cannot grow on smooth
rocks, but occur on mussels and barnacles, amongst which they thrust a dense
system of rhizoidal filaments. Where Mytilus and Balanus form extensive
sheets, these algae are often plentiful. The third type—a soft, spongy disk—
is supplied by Callithamnion arbuscula, This is intermediate between the
two former and the stout cellular disk. The spongy disk is composed of
filaments more or less free at the margins, but forming a dense tissue in the
centre. Algae possessing this type require a rough surface, and are commonly

found on barnacles.
Many transitions exist between the various forms of holdfasts, and the

subject, which is of great importance in connexion with the rock-surface,
requires detailed study. Epiphytes are adfixed in a number of ways; see
Tobler (06), Menz (’10), and Delf (12). In spite of the above exceptions, the
‘majority of the algae forming associations on a rocky shore are attached by a
stout. disk (Fucus, Porphyra, Rhodymenia).

Clare Island Survey— Marine Algae. 15 19

The following table presents the associations and other communities
composing the rocky-shore formation in the Clare Island area :—

A. Exposed coast series.

(a) Littoral Region.

Hildenbrandtia-Verrucaria.

Prasiola.

Enteromorpha intestinalis.

Fucaceae.

Lichina.

Porphyra.
Bangia-Urospora- Ulothrix.
Rhodymenia.
Laurencia-Gigartina.
Callithamnion arbuscula.
Nemalion.

Himanthalia.
Corallina-Lithothamnium.
Pool vegetation.

Cave vegetation.

(b) Sub-littoral region.
Laminaria.
fncrusting algae.

1B}. Sheltered coast serves.
(a) Littoral Region.

Hildenbrandtia- Verrucaria.
Fucaceae.

Lichina.

Porphyyra.
Laurencia-Gigartina.
Corallina-Lithothamnium.
Corallina-Cladostephus.
Rhbodochorton floridulum.
Sand-pool vegetation.
Cave vegetation.

(b) Sub-littoral region.
Laminaria.
Encrusting algae.
Fruticulose Lithothamnium.

A, Eeposed Coast Series.

(a) Lnttoral Region.

Hildenbrandtia- Verrucaria Association.

The description of this algal and lichen community is somewhat brief,
owing to the difficulty of distinguishing the species im situ, and the labour
involved both in collecting and naming material. Hildenbrandtia prototypus
and the marine species of Verrucaria are usually taken together as forming
one association, and some writers include other plants such as Rivularia atra
and Calothriz scopulorum. It is, however,a question whether it would not be
advisable to include in the association all the littoral encrusting species that
are soft and not calcareous (see note on sheltered form of association, p. 51).

Hildenbrandtia and Verrucaria resemble each other precisely in growth-

form ; and they are often found growing together covering an area of several

15 20 Proceedings of the Royal Irish Academy.

square yards. Both possess exceedingly thin encrusting thalli, which are so
closely adpressed to the rock, that the latter appear as if coated with paint.
In addition to those mentioned above, probably several other species of lichens
are present. Of the three plants referred to, V. maura forms a band a short
distance above the Pelvetia zone, whilst the other two appear below Pelvetia,
and descend nearly to the level of low-water. Hildenbrandtia is more
susceptible to drying up than V. mucosa, and in the Pelvetia and #. spiralis
zones it occurs under the shade of algae, in damp chinks, or in pools. On
ordinary open shores its growth does not occur above this level; but on very
exposed coasts when there is spray, it ascends far above high-water line,
being found in dark fissures in the rock, or in small pools that occur on the
rugged cliffs, the water of which is often brackish. On the lower part
of the shore Hildenbrandtia is not confined to pools and chinks, but is found
on bare rocks, and remains quite dry for several hours. In the lowest
levels, it is usually replaced by a broad band of Ralfsia clavata, in which
patches of Petrocelis cruenta are ftvequent, especially if the rocks are
smooth.

Verrucaria mucosa grows mostly on halt-tide rocks that are fully exposed
to light and air; in shady positions or where a covering of algae prevents
excessive desiccation, the growth extends to the F. spiralis zone; but it
rarely, if ever, takes advantage of pools to ascend to a higher level. In this
respect it differs from Hildenbrandtia. The plant prefers smooth rocks or
boulders, and is seen at its best on the beach north of Portlea, where it
covers the upper sides of the boulders from about half-tide level to below
the low-water limit of neap-tides. Its growth here is almost pure, and
the individual patches are very large, some noted measuring a yard
across. The vertical range on the shore varied somewhat in the different
localities; but this may possibly have been due to the presence of more than
one species. On only one or two occasions was a Verrucaria-growth noted
in a rock-pool. Probably few lichens are so difficult to determine or so
little understood as the marine Verrucariae; and it is a source of great
satisfaction to learn that Miss M. C. Knowles is working at the problem,
and doing so from an ecological as well as from a systematic standpoint. The
encrusting algae also are in need of critical study.

The present community is well developed in all parts of the survey-area.
It is abundant on smooth slabs and boulders, and is also found on the rough
slate and sandstone. It extends to sheltered localities, where, if rocks and
boulders are absent, it often occurs on stones and pebbles. A very similar
vegetation exists in Sweden, Iceland, and the Faerdes, according to the
accounts of Kylin, Jonsson, and Borgesen,

Clare Islund Survey—Murine Algae. 15 21

Prasiola stipitata Association.

This association as it occurs in the Survey area is characteristic of bird-
cliffs ; but during the winter months it is found to a small extent outside these
areas. It is well developed on Caher Island, The Bills, and below the bird
colonies near the Signal Tower on Clare Island. The growth is most
abundant on the shady side of the cliffs, where it ascends to a considerable
height above high-water level, and forms the uppermost association of the
marine algae. With P. stipitata occurs, in the upper part, a certain amount
of P. crispa var. marina. The localities referred to are very exposed,
and; in rough weather, the cliffs are constantly soaked with spray, though
during calm periods the vegetation must remain dry for some days. The
fact that, in June, the small part of the south side of The Bills that was
examined showed no trace of Prasiola, suggests that in summer the growth
is confined to the more shady situations—a view which is supported by
points noted in the following paragraph.

During the winter and spring months, Prasiola is found apart from birds.
Wide patches were noted at Roonah and Old Head during the February visit,
and in April, 1911, in many spots on Clare Island.. The growth is
practically pure, but is sometimes mixed with a certain amount of Calothrix
and Lyngbya; it occurs on both smooth and rough rocks. In these localities,
as on the bird cliffs, Prasiola forms the uppermost algal vegetation, frequently
reaching the Lichina confinis band, but more often forming patches between
that zone and Pelvetia. In several spots on the south shore of Clare Island
it was present only on rocks sloping landwards, where it was consequently
somewhat shaded; but in others it was found on sun-dried rocks and well
above the uppermost Pelvetia. These rocks were fully exposed to the surf;
and the plants, except during the calmest weather, would be splashed with
spray. By July all this vegetation had disappeared; and it was not noted
during June of the previous year.

The question of the connexion of Prasiola stipitata with bird-colonies is an
interesting one. ‘The preference shown by the fresh-water species, P. crispa,
for localities soaked with ammoniacal liquid is well known; and its marine
relative evidently shares the same avidity for nitrogenous compounds. During
a trip to Belfast in connexion with the growth of Ulva in sewage-polluted
water, P. stipitata was, on the shores of Belfast Lough during April, noted
‘only around small drainage outfalls. In Larne Lough also a vigorous crop
was always to be found in similar situations. At Ballycastle, Co. Antrim,
however, as in Clare Island and Clew Bay, numerous patches of Prasiola
oceurred (chiefly in shady spots) where there was no special supply of
nitrogenous food.

15 22 Proceedings of the Royal Irish Academy.

The vegetation described above, taken together with the Enteromorpha
growth, corresponds to Bérgesen’s “Chlorophyceae Formation.” In Clare
Island, the Enteromorpha vegetation is entirely distinct from Prasiola, and it
occurs only where certain definite conditions are present. In the Faerdes, on ~
the other hand, species of these two algal genera are of general occurrence,
and form together a well-marked green belt around the islands, The same is
the case in Iceland.

Enteromorpha intestinalis Association.

As remarked above, the Enteromorpha association of exposed coasts
is included by Borgesen in his Chlorophyceae formation. In Clare Islands
however, the Enteromorpha growth differs so markedly from Bérgesen’s com-
munity that it is necessary to regard it as a distinct association. In the
Faerdes the formation is described as stretching like a green belt along the
coast, and composed of four associations which occur in the following
sequence :—Prusiola erispa, Rhizoclonium riparium, EH. intestinalis, and P.
stipitata. In Clare Island the Enteromorpha association is quite distinct
from that of Prasiola, and is found, not as a continuous band, but only
where fresh water exudes from the cliffs. This type of green vegetatiun,
though not previously described, is frequently met with in the British Isles.
It is not largely developed in the Clare Island district, but is found in its
typical form, and is therefore included in the present account.

On crossing from Achill Sound to the island, the association in question
strikes the eye as a bright green band near high-water mark, between
Kinnacorra and the harbour, and wherever a band of this nature is seen it is
a sure sign of the presence of fresh water. Where only a small amount
exudes, or the shore falls rapidly, the band is narrow, and a fucaceous or other
community follows it at once; but with more water and a gradual slope the
association takes the form of wide-spreading bands which run transversely over
the rocks with a copious development below of Cyanophyceae and Diatoms.
A small amount of Rhizoclonium ripartwm is, on flat rocks, sometimes
intermixed with Enteromorpha; but more often the growth is practically
pure, var. cornucopiae being usually plentiful. On vertical rocks and below
small waterfalls Rhizoclonium is more abundant and may be dominant. The
forms of Enteromorpha present are mostly short forms of &. intestinalis var.
genuina and var. cornucopiae, with the addition occasionally of var. micrococea.

With regard to the bathymetric range of the association, its upper limit
varies directly with the position and manner in which the fresh water oozes
from the rocks. In some places the growth is completely submerged at high
tide, but in other spots the upper part is not even reached by the spray of an

Clare Island Survey— Marine Algae. 15 23

ordinary spring-tide (e.g., below the lace school on Clare Island), With an
alga such as Enteromorpha intestinalis, which is not dependent on salt water,
this is only to be expected. By the end of summer much of the growth may
be killed through drought, and the lower part of the association then appears
as a pure white band of dead tissue.

In rock-pools above high-water mark an Enteromorpha vegetation is
found on exposed coasts which may be regarded as merely a pool extension
of the community just described. The pools in question usually have
a large admixture of rain-water, and during the less sunny parts of the
year, they contain a vigorous growth of Enteromorpha, and occasionally
Hildenbrandtia and Cladophora sericea.

Fucaceae Association. (Exposed Coasts.)

The conspicuous growth of the Fucaceae that is found on all rocky shores
of the British Isles is well represented in the Survey area. The large size of
the plants concerned, and the readiness with which the species can be recog-
nized, render the Fucaceae association one of the most useful and instructive
for ecological study. With few other genera can the effect of wave-action on
an exposed coast be studied with so much ease, and with few other associations
can the differences in composition and in plant-form he so readily traced. On
sheltered coasts the study is more difficult. Though familiar in a general way
to all British algologists, no definite account of the Fucaceae associations of our
islands has been published, and the study of the vegetation as it exists in
Co. Mayo was not without value in bringing to light several interesting
features.

The composition of the association as it occurs in the British Isles is as
follows, the species occurring in the order given from above downwards :—.

®

Pelvetia canaliculata.

Fucus spiralis.

Ascophyllum nodosum (moderate shelter necessary).
Fucus vesiculosus.

F. serratus.

F. ceranoides (admixture of fresh water necessary).

An additional species, F. inflatus, was recorded by Borgesen for the
Shetland Isles, and Mr. E. M. Holmes has lately received a specimen of this
boreal species from Lewis, so possibly it is a regular constituent of the
association in the north of Scotland. Besides the ordinary forms and
varieties, some very remarkable modifications occasionally occur. (See p. 80.)

Fully exposed Coasts,—Turning to the Fucaceae association of Clare Island,

15 24 Proceedings of the Royal Irish Academy.

we find that in fully exposed localities it is composed of three species only,
namely—Pelvetia, #. spiralis, and F. vesiculosus, var. evesiculosus, a precise
combination which has not previously been described, unless it be that referred
to by Boye (94-5). Pelvetia forms a narrow zone about 14-2 feet deep.
F. spiralis follows with a band only slightly deeper, and composed of fronds
seldom more than 6 or 8 inches in length; whilst the lowermost zone of
F, vesiculosus, var. evesiculosus, has a greater bathymetric range, and therefore
covers a wider horizontal surface. The fronds are very narrow and the
growth short, though, except in the most boisterous spots, it is longer than
F. spiralis, This type of vegetation is found more or less along the whole
south shore of Clare Island, where there is full exposure; and it forms a band
covering the entire upper part of the littoral region. The shore is for the
most part steep; hence the bands are narrow. With a flatter shore and less
exposure, the association spreads out horizontally, and other differences are —
noticeable as mentioned later.

Of the three species, Pelvetia is perhaps the most susceptible to severe
exposure, and F. spiralis the least so. In a general way Pelvetia forms a band
just above the ordinary high-water level, but it is splashed daily,except in spells
of exceptionally calm weather. In very open spots, or where waves break
and there is much spray, it ascends much higher. Everywhere it forms a band
that is very conspicuous in summer and autumn by its orange-yellow
receptacles. Owing to their bathymetric position, the two species of Fuci,
unlike Pelvetia, feel the full force of the waves, but it is only in places with
the severest exposure that the association is wanting. The attachment to the
rock is exceedingly secure, and, though often torn by the waves, none but ola
and worn-out specimens become detached. Several spots were noted where
F. spiralis only occurred, and it appeared that the exposure was too great
for E. vesiculosus. When fruit is absent it is difficult to distinguish the two
species ; but in fertile specimens the short, rounded, hermaphrodite fruits of
F, spiralis, and the narrow, pointed, unisexual receptacles of F. vesiculosus
separate them at once. On exposed coasts the former plant fruits from spring
to late autumn, the latter in winter, spring, and early summer.

Moderately exposed Coasts—On passing to less exposed rocks or to bays
where there is a measure of shelter, a difference in form and in composition is
at once apparent. Pelvetia remains the same, but takes a somewhat lower
level. F. spiralis becomes longer and the fronds wider, but still retains its
typical spiralis form. F. vesiculosus is also larger, and often possesses a few
bladders, the size of the frond and the number of bladders increasing with
the amount of shelter. A fourth species, /’. serratus, now enters the association.
This begins in the lower part of the F. vesiculosus zone (slightly above

Clare Island Survey— Marie Algae. 15 25

Himanthalia), and forms a broad band extending down to the Laminaria
level. It appears to enjoy moderate wave-action, but requires flat rocks,
and disappears at once where the rocks are steep or the exposure too
great. This form of fucaceous growth occurs typically on the slopes near
Kinnacorra, near the Castle, and at several spots on the south shore,

With greater shelter further differences are evident, Pelvetia and
F. serratus remain as before, but F. spiralis broadens out into var. platycarpus
and F, vesiculosus develops more vesicles, the length of both species increasing
and assuming the heavy bulky growth characteristic of sheltered coasts. The
horizontal distribution also of all the species tends to increase, owing to the
shore being usually flatter. Such growth occurs in several bays on the island,
and is common in more open parts of Clew Bay. Ascophyllum nodosum requires
considerable shelter ; and in Clare Island it is present in one spot only, namely
Ooghbeg on the south shore. The shore here is rather flat, and the force of
the waves is broken by the presence of blocks and boulders. At Portlea (parts
of which might appear to be equally sheltered) Ascophyllum is absent, but the
presence of a vigorous Himanthalia vegetation indicates greater exposure
than might be supposed. For further notes on this species see p. 55.

Epiphytes—The typical epiphytes of the exposed Fucus association are as
follows, and in the most exposed spots these are practically all that occur :—

Ulothrix pseudoflacca (in spring). Elachista fucicola.
Enteromorpha compressa. Porphyra umbilicalis.
Ectocarpus luteolus.

Where the conditions are less boisterous (e.g. at Kinnacorra) a number of
other species occur in addition, for example—

Ectocarpus tomentosus. Polysiphonia fastigiata (on F. spiralis).
E. fasciculatus. Ceramium rubrum.
Porphyra leucosticta (in spring). C. Boergesenii.

Rhodymenia palmata.

Subvegetation.— This, though always better developed in the lower than in
the upper levels, is largely dependent on the denseness of the Fucus growth,
ie. on the amount of room and light available. When conditions are favour-
able, the first four of the following communities are usually represented, and
the last three are occasionally present in addition :—

Hildenbrandtia-Verrucaria Association. Lichina pygmaea Association.
Porphyra umbilicalis Rhodymenia palmata ,,
Laurencia pinnatifida $5 Lithothamnium Lenormandi Society.

Corallina spp. Society
RB, I. A. PROC., VOL. XXXI. D 15

15 26 Proceedings of the Royal Trish Academy.

In the low littoral region, if the / serratus vegetation is not dense, a very
large number of species occur, the shelter and shade being highly suitable
for :—

Dictyota dichotoma. Polysiphonia fruticulosa,
Chylocladia ovalis. P. thuyoides.

C. articulata. Plumaria elegans.

Delesseria alata. Lithothamnion polymorphum.
Nitophyllum laceratum. Sporelings, many spp.

Comparison with other Countries.—In a general way the Fucaceae association
described above represents that of the whole of the British Isles, It agrees
well with that observed on the south and east of England, and though the
Fucaceae of the British Isles have never been specially investigated from the
present point of view, it is not likely that any startling departures from the
Clare Island type will be met with. The greatest variation may be expected
on the north of Scotland. The vegetation described for the Norwegian coast
is similar, agreeing floristically, but differmg in minor points. With more
thorough investigation some of the latter will probably disappear. In west
Sweden, Pelvetia is absent, and Kylin makes no reference to F. spiralis on
exposed coasts. He notes the presence of the form #’, Aveschougu on mederately
open shores, and it would be remarkable if the short exposed form, so addicted
to boisterous localities elsewhere, were absent. A belt of an evesiculate
variety of FI vesiculosus is well developed, but from specimens sent by
Dr. Kylin, it is clear that his form (compressus racemosus, Kjellman) is
different from that which occurs on Clare Island. The Faerdese Fucus
vegetation differs in several respects from the Irish. In the first place,
I’, serratus is absent, Ff. inflatus taking its place; F. spiralis is not found with
extreme shelter, and /. vesiculosus disappears entirely with exposure; lastly,
Pelvetia is absent from exposed coasts. The last two points were specially
investigated by Dr. Bérgesen during his visit to Clare Island; and he agreed
that both species flourish in Ireland with very much more exposure than in
the Faerées. The Fucus vegetation of Iceland is similar to that of the last-
named, in that it possesses a vigorous growth of Ff. inflatus, though F. serratus
is present in addition. From the brief account given by Joubin ('09), the
Fucaceae vegetation at Roscoff appears to agree in the main with that of
the British Isles.

The Lichina communities.

Though a lichen and not an alga, Lichina pygmaea is always found between
the tide-marks, and forms so essential a part of the marine vegetation that it

Clare Island Survey—Marine Algae. 15 27

deserves mention in the present report. The second species, Z. confinis, is
scarcely littoral, being confined to rocks just. above high-water line, but its
growth may be suitably described together with that of Z. pygmaea. The
zones formed by these two species at times approach one another, but they
never overlap. Both occur on sheltered as well as on exposed coasts, though
for LZ. pygmaea rocks or boulders are essential. With the exception of Joubin
(09), algologists have not dealt with this vegetation, though Nylander, as long
ago as 1861, drew attention to the belts of Lichina on the sea-shore.

(a). Z. pygmaea, the larger and more conspicuous species, forms circular
patches which vary from a few inches to a foot in diameter. It usually
commences immediately below Pelvetia, and extends downwards through the
F. spiralis belt to F. vesiculosus, or to within a few feet of low-water. In
certain localities it extends well up into the Pelvetia band; but it never occurs
above it. The maximum development usually takes place in the upper part
of the zone, where the plant often forms a very conspicuous black band on
the vertical faces of rocks or boulders capped with F. spiralis, It undoubtedly
favours sloping or vertical surfaces; but it also occurs on those that are
horizontal. Though frequent on smooth boulders, it prefers rough or eroded
rocks, and is abundant on barnacles. Unlike ZL. conjinis, the present species
can only stand a certain amount of drying. In the lower part of the associa-
tion it occurs fully open to the sun; but in the uppermost levels it is usually
found in chinks and pockets which retain moisture, or on rocks with a shady
aspect. In calm weather, during neap-tides, the Pelvetia zone may be left
entirely dry for several consecutive days; and any growth of L. pygmaea that
reaches this level is occasionally subjected to like conditions.

On the exposed and semi-exposed shores of Clare Island and the mainland
L. pygmaea is abundant, but where the exposure is excessive it does not
appear to flourish. On the large blocks and boulders to the north of Portlea
it is one of the few macroscopic plants which form a definite association; and
in such localities, where Fuci are absent, the lichens form a useful means of
determining tidal levels. A very luxuriant vegetation of Verrucaria spp.
covers the boulders of this beach almost from top to bottom (p. 20),

During the summer (July-Sept.), a fine growth of Rivularia bullata is
frequently found epiphytically on Z. pyymaea. In 1911 it was unusually
abundant, being noted in August in all the exposed parts of the mainland
and Clare Island. £&. bullata is not confined to the Lichina patches, but
also occurs on bare rock, It sets in about half-tide level, and continues to
low-water mark.

(b). The second spécies, Z. confinis, has fronds barely 3 mm. long, and the
individual patches are 2-4 cm. in diameter ; being black in colour it is very

D2

15 28 Proceedings of the Royal Irish Academy.

inconspicuous on the dark slaty rocks of Clare Island. It usually occurs a
short distance above Pelvetia, and extends up the cliffs on the south shore to
a height of 12-15 feet. In this position it is frequently drenched with spray,
though in summer it may be dry, except for rain, for weeks together. With
less exposure its vertical range is restricted. On the gentle slopes at
Kinnacorra it is only 3-4 feet above Pelvetia; whilst on the flat shores of
Clew Bay and Achill Sound it hardly exceeds the neap-tide level, and is
regularly covered during the highest tides. This occasional flooding by spring-
tides in sheltered localities obviously takes the place of the soaking by spray
on open coasts. In Clew Bay and other places where rocks and boulders are
absent, the plant often occurs on flat stones, and may even be traced as an
irregular band running along the shore. In Roundstone Bay the three plants,
L. confinis, P. canaliculata, and L. pygmaea were noted on large slabs, forming
luxuriant and well-marked zones, each species following the other as a band,
1-2 feet deep.

The Lichina vegetation at Roscoff described by Joubin (’09) is evidently
very similar to that found in Ireland. Both species are present, and the
plants show a preference for exposed situations.

Porphyra umbilicalis Association.

Porphyra is one of those algae which occur as a definite association
on both exposed and sheltered shores. The form assumed by the plant is
very distinct in the two situations; and it is curious that it has not been seen
as an association in localities offering intermediate conditions, although its
occurrence in small quantity is common enough. Another feature which
gives interest to the exposed Porphyra community is the diversity of its
bathymetric range in different countries, and even in different spots in the
same locality. For instance, in Clare Island the upper limit of the Porphyra
belt is almost always below the Pelvetia zone, whereas in the Faerées the
greater part is normally above that belt, and on exposed shores it may occur
as much as 40-50 feet above high-water line. Doubtless surf and spray are
largely responsible for its presence in such positions, just as they are seen to
be directly responsible for minor variations on Clare Island. But this alone
does not account for all the differences that have been noted, and further
study is needed,

On most parts of Clare Island a certain amount of Porphyra vegetation
is present; in some it is extensive and forms broad or narrow bands; in
others it is limited, and occurs only as small patches between other com-
munities. It prefers rocks of a moderate or rather steep slope, but is also

Clare Island Survey—Marine Algae. 15 29

found on flat rocks, and rarely on the perpendicular faces. The rock-surface
may be rugged or smooth, and a very favourite substratum is that of mussels.
In all cases the rocks are exposed; and often the most vigorous patches are
those where the waves strike with great force. The normal position of
Porphyra is in the upper part of the littoral region, where it occurs as a band
a short distance below Pelvetia. In some cases the band is quite narrow, as
is shown in Plate I, where it occurs between Pelvetia and F. vesiculosus, taking
the place of Fucus spiralis; in others it is mixed with / spiralis, and runs
down through the wider belt of F. vestewlosus that follows. Porphyra also
occurs where the Fucaceae are absent, and is here commonly mingled with
Bangia or Ceramivm acanthonotum. At Kinnacorra it is found on smooth
sloping rocks devoid of vegetation, and forms a fairly wide band from a short
distance below high-water mark down to about half-tide, at which level
Bangia takes its place. In this position, being quite unprotected from the
sun, if becomes very dry and disappears during summer.

A very distinct aspect is acquired by the association during winter, owing
to the presence of an abundant growth of var. linearis. This plant, though
often regarded as a distinct species, represents sporelings of P. wmbilicalis,
which at that season are elongated and tapering. The growth appears first in
October, and develops rapidly during the winter, frequently covering boulders
and smooth rocks over extensive areas. It is usually quite distinct from the
normal Porphyra association, and forms a band above it. In March the
effect of drying winds and increased sunlight is felt, and much of the growth
dies. By April var. linearis has disappeared, except in lower and shaded
places.

With regard to the supra-littoral growth, the contrast between Clare
Island and the Faerdes is most marked. In a few spots Porphyra was noted as
extending into the Pelvetia band on Clare Island; and at Alnahaskilla it was
found at the highest tide-level on the north side of steep bare rocks, a sample
of the kind of growth that takes place on a much larger scale on the Faeroes,
Below the big cliff on the north side of the island, where the shore is steep
and the rocks fully open to the Atlantic, Porphyra was one of the few algae
that were noted in the littoral zone. But even here, with shade and continual
spray, there was no supra-littoral growth comparable to that described by
Borgesen. Its growth probably exceeded the limit of high-water level (which,
owing to the constant swell, is not easy to determine), but not to any remark-
able extent. In the FaerGes, on the other hand, even in sheltered localities,
the lowest iimit is at high-water mark, and in exposed situations it is not
found till far above that level.

Kjellmann and other Scandinavian alyologists have regarded the Porphyva

15 30 Proceedings of the Royal Irish Academy.

community as a winter vegetation; and Borgesen states that, though in the
Faerées it is developed all the year round, it is in more southern ‘countries
characteristic of winter. On Clare Island this is hardly the case. The
Porphyra association is in fine condition in July and August, and abundant even
on the south shore (vide Plate I). It is, however, more widely spread in winter,
owing partly to the presence of a band of var. /inewris ; but the association in the
Clare Island neighbourhood certainly occurs throughout the year. Borgesen
also remarks that he did not observe the Porphyra vegetation at North
Berwick (Scotland) in July, 1909, but Dr. A. A. Lawson informs me that at
St. Andrews (about seventeen miles further north) it was plentiful in July
and August, 1910; though in the hot dry summer of 1911 it was much less
conspicuous. In the south of England it is a winter and spring vegetation,
though in July, 1911, the Porphyra belt was still discernible on exposed
rocks at Portland Bill. ‘The exposed Porphyra association is also recorded
from Iceland (where it closely resembles that of the Faerées), west Sweden
(Kjellmann, ’78, Kylin, ’07), and Norway (Kylin, ’10).

To sum up, the Porphyra vegetation of the exposed coasts of Clare Island
forms a belt in the littoral zone, at a very much lower level than it does on
the Faerdes, and does not, even in shady and very exposed localities, grow
far above the high-water line. In contrast to the south of England, Sweden,
and Denmark, but in agreement with that described for Norway and the
Faerdes, it exists through the entire year. The form of the plant on
exposed coasts is entirely different from that found in sheltered localities,

Bangia-Urospora-Ulothrix Association.

The most striking feature of this community is its sporadic appearance.
During the first two years of the Survey scarcely a thread of Bangia or
Urospora was found; but during the spring of 1911 a remarkably fine and
widespread development of the typical Bangia-Urospora-Ulothrix association
occurred on Clare Island and on the exposed parts of the mainland. This
vegetation was probably at its best during the time of the April visit; by
August it had entirely vanished. In the Faerées it appears to be more or
less permanent; but, as shown below, its sporadic appearance is known in
other countries, and it may even be absent for several years in succession over
a wide stretch of coast-line (vide Borgesen, 05, p. 720). For this reason the
appearance of well-marked belts of Bangia and Urospora during the last year
of the Survey was particularly gratifying.

The community in question occurs on exposed and moderately exposed
rocks, especially where the surface is smooth and where other algae do not
ootain a footing. In bathymetric range the association as a whole corresponds

Clare Island Survey— Marine Algae. 15 31

to that of Porphyra, extending from below the Pelvetia zone to within a
few feet of low water. Its composition is as follows :—

Bangia fuscopurpurea,
_ Ulothrix pseudoflacca, ) co-dominant.
Urospora mirabilis,
Ulothrix consociata,
Enteromorpha minima.

As a rule all the species, except #. minima, which is local, occur together,
though each forms a separate patch or narrow strip within the association.
Occasionally, however, the species occur separately; and a pure growth of
Bangia or Urospora may cover a wide area. In a few cases the growth may
be thoroughly mixed. -

An effort was made, when the full series was present, to determine
the vertical sequence of the species; but this was unsuccessful in so far as
obtaining a constancy in succession was concerned, The necessity of
microscopic examination made the determination in the field difficult, and
the work required more time than was available. As a general rule, however,
where the association is typically developed, Bangia appears to have a wider
yertical distribution than the other species, as it is often both the first to
appear and last to leave on passing from top to bottom of the area. But
occasionally a Ulothrix growth is found at a very high level in sheltered
localities where Bangia is absent.

The occurrence of the Bangia-Urospora association on smooth rocks and
boulders where other vegetation is absent is explained by the exceedingly
fine unbranched filaments of the plants, reducing to a minimum the strain
on the basal attachment. At the same time each filament is separately
fixed to the rock, so that the association may be said to be attached along its
whole base.

The most usual extraneous species is Porphyra wmbilicalis, small specimens
of which frequently occur in the upper levels; and it is into the Porphyra
association that the present community most frequently merges. Bangia,
which is less restricted than Ulothrix or Urospora, also occurs on barnacles,
where it enters into competition with Ceramium acanthonotum.

The total absence of Bangia in some years has been referred to by
Boérgesen for Norway (’05, p. 720), and Rosenvinge for Denmark (09). The
latter, who has studied the Bangiales of Denmark in detail, writes as follows
concerning B. fuscopurpurea :—

“The most dangerous condition for the Bangia vegetation is a fairly long
period of easterly winds so light that this vegetation is not reached by the

15 32 Proceedings of the Royal Trish Academy.

waves, especially when the weather at the time is bright and dry. Its
occurrence is therefore very different, not onlyat various seasons, but in different
years. In winter it is very abundant: but the critical period of the spring
will every year kill a greater part of it; and on the duration and intensity —
of this period depends to what degree that will take place. In summer,
for example, it occurs at Frederikshavn in some years only in small
quantity, while in others it forms extensive growths—as in the beginning
of August, 1902” (Le., p. 58).

With regard to Clare Island, drying winds during a critical period of the
life-history no doubt largely influence the growth of the plants. The
association may occur annually as winter vegetation, and it may possibly
have been present in the early spring of 1910; but if this was the case, it
had completely disappeared by June, and was certainly absent in April, 1909.

Comparison with other Countries.—An association corresponding to that
described has been noted in many countries. It is present in Norway,
Sweden, Greenland, Iceland, and the Faerdes, having been dealt with by
Kylin, Rosenvinge, Jonsson, and Borgesen respectively; and, as already
shown, it occurs in Denmark. ‘The belt in these countries, as would be
expected, is found at a higher level than in Clare Island. It reaches, or
extends above, the high-water line in each case; and in the exposed part of
the Faerées it occurs as much as 30 feet above this level. In Greenland the
association differs floristically, and is termed by Rosenvinge the Monostroma
grocnlandicum association, after the dominant species. In the Baltic
(Gotland) Svedelius has described a similar vegetation, consisting entirely of
Urospora penieilliformis. 3

Rhodymenia Association.

An association of Rhodymenia similar to that described by Borgesen, and
noted by him as being widely spread on the Faerdes, occurs in our district,
though only to a limited extent. Borgesen stated that he had found no
reference to such an association, but that he expected it to be common in the
North Atlantic. In the Clare Island area it is but feebly developed ; but at
Dog’s Bay, near Roundstone, a very extensive growth was observed, showing
that the association exists on some parts of the west of Ireland, as indeed was
already known. On the island, patches of Rhodymenia occur in several
spots between Portlea and the lighthouse, and on the mainland at Roonah and
at Old Head.

Judging by the localities in which the plant was found, Rhodymenia
prefers a northern aspect, which would account for the complete absence of
its growth, as an association, on the south shore of Clare Island, At Old

Clare Islund Survey— Marine Algae. 15 33

Head it is found on flat, sloping, or vertical, semi-exposed xocks, which face
north or north-east. At Portlea it affects similar situations, but shows-a
decided preference for vertical rocks (these being at the sametime the more
shaded). The plants are attached by a strong basal disk, and are usually found
on mussels, but they occur also on limpets-and bare rock. The vertical area
covered by the alga is rather extensive, reaching at times from the bottom of
the F. spiralis zone down to about low-water mark, but more often forming
a band below the upper Porphyra. It is frequently interrupted by patches of
other vegetation. At Old Head, Fucus vesiculosus, var. evesiculosus is the chief
intruder; but portions of the Porphyra and Callithamnion arbuscula associa-
tions above, and the Nemalion vegetation below, are also interspersed amongst
it. A modified form of the association occurs on boulder-beaches, the plant
hanging in profusion from the lower part of boulders surmounted by
Himanthalia (Plate IT). :

The form of the alga when growing as an association on exposed coasts is
very distinct. Short and tufted, not more than 5 to 4 inches long, it consists
of narrow or rounded fronds, with a number of small lateral proliferations.
Though narrow, it is very distinct from var. sarniense, which is thinner and
paler in colour, and resembles Gracilaria multipartita in form, With increased
shelter the plant becomes larger, till at length the pool-form, with fronds a
foot or more in length, is reached. ‘The islanders distinguish the larger and
small forms as Dillisk and Crannogh respectively, and always associate the
latter with the presence of “small shells” —iLe., mussels (see Economic Section),

Borgesen remarks that the Rhodymenia association prefers places where
fresh water oozes from the rocks. This is not the case on Clare Island, Asa
pool or streamlet plant, Rhodymenia enjoysan admixture of fresh water; but
when growing as above described, it was always found in a purely marine
habitat.

Laurencia-Gigartina Association,

Near the low-water line on exposed coasts there often exists a dense
earpet composed of the two red algae,—Laurencia pinnatifida and Gigartina
mamillosa. Gigartina occupies the lower part and goes down into the sub-
littoral region, whilst Laurencia extends more or less in an upward direction.
The band formed by the latter is often conspicuous, so much so that it was
at first regarded as a distinct association. Further examination at spring:
tides showed that it was frequently connected with a zone of Gigartina, and
that in the more exposed places the latter species was dominant. It
gradually became evident that their relative abundance was largely a matter

of exposure and slope, and that these two species of similar habit could ‘be
| B,I,4. PROC,, VOL. XXXI, a0) 15

15 34 Proceedings of the Royal Trish Academy.

naturally regarded as forming a single belt. In a general way Laurencia
prefers a certain amount of shelter, and thrives on sloping or flat rocks, whereas
Gigartina enjoys the roughest water and steep surfaces. On comparing this
plant-community with those of other countries, it was found that the joint
belts formed by the two species in Clare Island corresponded to Boérgesen’s
Gigartina association in the Faerées—a conclusion which was confirmed by
him during his visit. It was thought best, therefore, to connect the Irish type
of vegetation with the Faeréese, and the name Laurencia-Gigartina association
has been given. In the Faerdes Laurencia is very rare, being found only in
pools.

The Gigartina band may be dealt with first. On exposed coasts it is
barely uncovered during neap-tides, but with spring-tides a distinct belt
reaching down to the Alaria and Z. digitata zone is revealed. It is frequently
accompanied by a certain amount of the narrow form of Chondrus crispus.
Well seen on vertical rocks, where it forms a band 2 feet deep, it also occurs
on flat and sloping surfaces, here usually as an undergrowth to Himanthalia.
On the open coasts it is often accompanied by the following algae, all of .
which are known to enjoy the turbulent conditions of low-water mark :—

Scytosiphon lomentarius. Plocamium coccineum.
Rhizoclonium implexum. Polysiphonia thuyoides.
Chylocladia ovalis. P. Brodiaei.
Lomentaria clavellosa. Corallina squamata.

The Gigartina belt occurs also on the more sheltered ground at Portlea.
Tt first appears well up in the Laurencia band; but as the lower levels
of the littoral region are reached, it increases greatly in quantity, till finally
it occurs as a pure growth covering comparatively large areas. At Kinnacorra,
on the other hand, where there are varying degrees of exposure, the Gigartina
vegetation is practically absent.

Passing now to Laurencia, we find this is more conspicuous on account of
its truly littoral habit. It begins shortly below the half-tide level, and runs
down into the Himanthalia association. It is common on moderately exposed
shores, and appears to prefer clean, gently sloping rocks where sand is absent.
Under these conditions Laurencia may exist as a pure growth 2 or 3 yards
wide, but where the shore is flat it extends over a much wider area, being
then mixed with other species. When sand is present it gradually gives place
to Rhodochorton floridulum.

In its lower levels the Laurencia belt forms an undergrowth to Himan-
thalia, and on sheltered shores occurs in a similar manner beneath F. serratus.
It is found at times under F, vesiculosus, and thus runs upwards considerably

Clare Island Survey—Marine Algae. 15 35

higher than on bare rocks. If the shade be not too dense, its growth is quite
as luxuriant as when fully exposed to light and air.

Another species, Z. hybrida, is a characteristic element in the upper part
of the association. This plant is more restricted in its range, and appears to
be more sensitive to desiccation. Ona flat shore it reaches its maximum
development somewhere about the middle of the Z. pinnatifida band, where
it is at times co-dominant. In the lowest parts it is practically absent; and
in the upper it is found only in the damper positions. On very exposed shores
L. hybrida is scarce (see p. 136).

L. pinnatifida reaches its maximum development about April or May ;
and at this season sloping rocks are carpeted with a growth 4 to 6 inches high.
Aiter May many of the larger fronds disappear, and the association as a
whole becomes inconspicuous. There remain, however, numerous small
shoots, which are continually augmented during the summer, the plant being
apparently perennial. JZ. hybrida, on the other hand, is an annual. Young
sporelings 1 to 2mm. long are discernible in September ; they develop during
winter, fruit in spring, and disappear in May.

Very marked colour-changes due to illumination are shown by Z. pinna-
tifida, and to a less extent by Gigartina. The normal colour of the former
is a deep purplish red; but during summer the growth in sunny situations
is pale yellow green. This gradually gives place to purplish green in
autumn, which becomes redder as the days shorten. The production of
antheridia by Laurencia in March and April gives the plants a golden hue,
owing mainly to the yellow substance found in the antheridial cavities. As
a large number of male plants are often found together, sheets of bright yellow
fronds are frequent.

Callithamnion arbuscula Association.

The plant-community formed either by Callithamnion arbuscula, ot
Ceramium acanthonotum, or a mixture of both, has been described by several
writers under various names. Callithamnion is the more conspicuous plant,
and most writers have dealt largely with this species; Ceramtwm acanthonotum
is, however, an equally important element. Clare Island is peculiar in
possessing in addition a small quantity of the southern Callithamnion
granulatum.

The association is well developed on many parts of the island and exposed
mainland. The relative amount of the two species varied during the
different seasons—a fact which probably explains discrepancies in accounts of
the same area by different writers. In July, 1910, Ceramiwm acanthonotwm
was the dominant species on Clare Island, whereas in August, 1911,

K2

15 36 Proceedings of the Royal Irish Academy.

Callithamnion arbuscula was more abundant. Apart from these seasonal
variations, Ceramium is found chiefly on bare slopes with much or moderate
exposure; sometimes it occurs pure, forming a dense carpet several yards
square, but more often it is mixed and interrupted. Callithamnion prefers
the more boisterous positions, and is especially luxuriant on steep or vertical
rocks.

The belt formed by the association is at the same level as the lower part
of the Bangia and Porphyra associations, or slightly higher than the Nemalion
and Corallina communities. It usually begins just below F. spiradis, and extends
to within a few feet of low-water mark. Callithamnion often appears a
short distance above Ceramium, but for the most part the two species occupy
the same level. Where fresh-water streams exist, Ceramium not infrequently
ascends the shore, and may reach as high as Pelvetia. C. arbuscula, on the
other hand, does not thrive in fresh water.

Unlike the Bangia-Urospora association, the present plant-community is
most frequent on rough surfaces offering a good foothold. Ceramium, which
forms a spreading growth, usually occurs on mussels and Corallina, amongst
which it pushes a mass of rhizoids; but it also grows epiphytically on the
Callithamnion. The latter, on the contrary, has a scattered habit, each
plant possessing a single stem, which is thick and spongy. It is most
frequently attached to limpets, mussels, or the rock between them; only
varely is it found on other algae. Although both species occupy a fairly
high level, owing to the retention of water by their spongy thalli neither
becomes dry when the tide is out.

The associations into which the Callithamnion arbuscula vegetation most
frequently merges are those of Bangia, Nemalion, Corallina; and in addition
to algae derived from these sources the following species frequently occur
scattered in it :—

Rhizoclonium tortuosum. Polysiphonia macrocarpa.
Enteromorpha compressa. P. Brodiaei.
Scytosiphon lomentarius. P. thuyoides.

Petrospongium Berkeleyi.

Comparison with other Localities—In the British Isles Borgesen has
noted the community in Shetland, and I have observed it at. Whitby
(Yorks). On the south coast of England, where C. arbuscula is absent, the
association is represented by a belt composed entirely of C. granulatum.
(= C. spongiosum, Harv.). This has been noted at Swanage and Portland, and is
doubtless common. Ceramium acanthonotuwm, though known on the south coast,
does not enter into the Callithamnion association in either of these localities.

Clare Island Survey— Marine Algae. 15 37

It is interesting to note that, though C. arbuscula was the essential species
in Clare Island, specimens of the southern C. granulatum were scattered here
and there amongst it. The latter agreed in form with the Dorset specimens,
being short, very densely branched, and of a peculiar pale colour—a feature
which gives the clue to its presence (see p. 142).

Hansteen, Boye, and Kylin have each dealt with a vegetation on tite
west coast of Norway that is probably very similar to that here described,
though it is Callithamnion that has mostly attracted attention. Kleen also
records both algae from Nordland. In the Faerdes, Simons refers to a
“©. acanthonotum formation,’ not observing the presence of C. arbuscula,
whilst Bérgesen, exploring the coast more thoroughly, found the latter
abundantly in exposed places, and adopted the older term. — Both species
are found in Iceland, though Jonsson does not allude to them as forming an
association. :

Some remarks by Harvey with reference to this vegetation may be quoted
here. He observes with regard to C. arbuscula that “it delights in the most
exposed rocks and the roughest water, and very commonly grows on the
shells of Mytilus rugosus” (Phye. Brit., pl. 274); and concerning C. spongiosum,
he writes, “It is curious that it appears to occupy the place of C. arbuscula on
shores where the latter is not found, these plants never growing together,
though both affect similar situations on different shores” (1. ¢., pl. 125). As
shown above, Harvey’s statement as to position and habitat of the species
holds good for many countries, though the Clare Island work proves that
the two species may occasionally occur together.

_ Nemalion Association.

The present vegetation, described by Kjellmann in 1875, was one of the
first algal associations to be recognized. It differs from many others in being
a purely summer growth, and might therefore be more suitably regarded
as a plant-society. The Nemalion belt occurs in the lower half of the
littoral region—that part of the shore which is crowded with a succession
of algae, and in which many transient societies are recognisable. Nemalion
prefers bare rocks, and usually develops in spots devoid of other vegeta-
tion. It would prone yi find a place as a subdivision of Borgesen’s
“Corallina formation”; but in the present state of our knowledge ‘it
appears advisable to follow Biewous writers rather than introduce doubtful
alterations.

The Nemalion growth is first noticeable early in June, reaches its maximum
in August or September, and disappears in October. The association in Clare

15 38 Proceedings of the Royal Trish Academy.

Island (as in 8. England) is composed of two species—JV. multifidwm, and the
stouter unbranched JV. elminthoides Batters (= NV. lubricum J. Ag.).’ The zone
formed is 5 to 6 feet deep, and extends from about half-tide level to the ordinary
low-water mark. Its luxuriance varies considerably in different localities.
In some, a vigorous growth is present in the upper part of the zone, whilst
in others the algae are better developed near low-water mark. JV. elminthoides
is usually confined to the upper portion, and lasts later in the season than
N. multifida. The plants are attached to bare rock, or limpets, and
occasionally to mussels. They prefer sloping surfaces, fully exposed to
waves and surf.

The Nemalion association is found in the band of Lithophyllwm imerustans ;
but it prefers bare rock devoid of other vegetation. Where mussels occur, it
is usually replaced by the association of Ceramiuwm acanthonotwm, or
Rhodymenia. Amongst it are scattered individuals of Scytosiphon lomentarius,
Enteromorpha compressa, Rhizoclonium implecum, and Polysiphoia Brodiaer,
the last-named being confined to the lowest levels. On Clare Island the
association is of frequent occurrence; and in Clew Bay it occurs on exposed
points, such as Old Head. A similar type of growth has been described by
Kjellmann (’78), and Kylin (’07), for west Sweden ; by Gran (’93) for Norway ;
it would appear also to be widespread in Denmark (vide Rosenvinge, ’09).
In the south of England the community is frequently met with, having been
noted by me on the coasts of Dorset, Devon, and Cornwall.

Himanthalia Association.

This familiar association, which is well developed on Clare Island, is
characteristic of moderately exposed shores. It forms a belt in the lowest
part of the littoral region; but the extent of its horizontal range varies with
the amount of slope and the nature of the coast. On steep and vertical
rocks it is absent, or exists as a narrow band, 1 foot deep. On a shore of
moderate slope the band is wider, and extends from the Laminaria zone to
2 or 3 feet above low-water mark; whilst on flat shores, especially where
there is a dense sub-vegetation, it covers a wide area. With partial shelter,
Himanthalia descends some distance into the sub-littoral region, and occurs
mixed with Cystoseira ericoides and species of Laminaria; but apart from the
extension both in an upward and downward direction, its normal position

1 This plant, clearly figured by Velley, is usually regarded as a distinct species ; but as seen in
Clare Island and in the South of England, it is difficult to separate from WV. multifidum.

Clare Island Survey—Marine Algae 15 39

on a sloping shore is between the Lawrenciw pinnatyida belt and the Laminaria
association.

In the form of a narrow band, the Himanthalia vegetation is seen on the
south shore of Clare Island in spots where the rocks are steep, and there is
full exposure to the waves; as a wider zone, it shows well on rocks which form
large sloping slabs, as at Kinnacorra. At Portlea a more extensive growth is
met with. The shore here is flat, but there is a moderate amount of rough
water and surf. A dense undergrowth of Lawrencia pinnatifida and other
algae covers the lower part of the littoral region, and on this the Himanthalia
lies as a thin covering. The belt, however, is not so deep as it appears; for,
although during spring-tides it is left dry for three or four hours, during
neap-tides the time of exposure and the amount uncovered are small. The
undergrowth conserves moisture, and enables the alga to ascend to a higher
level than otherwise. Portlea also affords an example of another type of
growth, viz., that on blocks and boulders. In this case Himanthalia is
attached to the upper parts of the boulders; but the strap-like fructifications
hang down over the sides (see Pl. II). Here again the alga may ascend
above its normal limit owing to the shade between the boulders.

Boérgesen remarks that, according to Boye, Himanthalia avoids localities
directly exposed to the surf, which is in contrast to its habit in the Faeroes.
In the British Isles it is certainly a surf-loving species; and in Clare Island
it occurs along the south shore, and also on such exposed points as Alnahaskilla.
At Ooghbeg, the one spot on Clare Island where Ascophyllum exists,
Himanthalia is found where the waves break at low-water; but as a rule, if
there is sufficient shelter for Ascophyllum, Himanthalia is absent. As noted
by Bérgesen, the present alga cannot stand desiccation ; and though odd
plants are seen some half-way up the shore, they do not thrive unless
protected from the sun. As a pool-plant it is one of the commonest species,
and is then usually infested by Hetocarpus fasciculatus, Ceramium Boergesenti,
and Herponema velutina. In the open, Hlachista seutulata is the usual
epiphyte.

Corallina and Lithothamnium Associations.

A belt of Corallina spp. is found just above low-water mark in many parts
of Clare Island. It is characteristic of very exposed rocks, where it appears
to take the place of the Lawrencia pinnatifida band of less open spots. An
extensive growth of encrusting algae is usually met with as an under-
growth, and the two types of vegetation appear to be intimately connected,
and may for the present he treated together,

15 40 Proceedings of the Royal Irish Academy,

-. ‘The species concerned are as follows :—
Corallina squamata, dom.
C. officinalis, co- or sub-dom.

Lithothamnium Lenormandi. inal
Undergrowth,

Lithyphyllum incrustans. :
J | in zones,

Lithothamnium polymorphum.,

(a) The Corallina growth is very much worn down by the waves, so that it
occurs in the form of dense cushions, the specific identity of which is difficult
to ascertain. In shallow depressions or with slight shelter, the production
of larger and more perfect fronds allows their true nature to be determined,
and in each case examined it was evident that the bulk of the growth was
composed of C. sguamata, though C. officinalis was at times also present.

The first signs of the Corallina belt are found at about half-tide level,
usually just below the top of the Nemalion zone. The plants are found here
in chinks and fissures, where there is little risk of drying, and on passing
downwards they gradually spread out over the surface of the rocks. They
are, especially in the upper parts, frequently attached to mussels; and the
growth of these two organisms together form the compact cushions referred
to. At the lower part of the zone the fronds are large. This is due
partly to their being protected by the Laminaria foliage, and partly to their
being below the level at which the waves break. A great improvement in
colour is at the same time noticeable. C. squamata as well as C. officinalis
occurs at the top of the Laminaria belt; and the latter certainly, if not indeed
both, descends some distance into the sub-littoral region.

With increased shelter, though the plants are larger and less broken by
the waves, the band as a whole is not so conspicuous, owing to its being
replaced by other algae (usually Laurencia). Shallow pools are an exception.
Here a fine growth of C. officinalis is often present, and less frequently
C. squamata, ‘The latter is seen at its best on narrow ledges, or hanging from
the sides of shady rocks.

The Corallina association above dealt with differs floristically from all
others hitherto described, in being composed largely of the southern species
C. squamata. his is probably the case in all the warmer parts of the British
Isles. ‘There is no question as to the abundance of C. sguamata in Clare
Island ; and it is doubtless equally common along the whole of the south and
west of Ireland. It also occurs in plenty in the south of England, and has
been noted as forming the principal constituent of the Corallina association
at the end of Portland Bill.

(b) The Lithothamnium vegetation is described here together with that of
Corallina, because it is exceptionally well developed when found in company

Clare Island Survey Marine Algue. 15 41
with a widespread growth of that alga. A thorough study of its occurrence
in varying conditions was not made; consequently the following notes must be
regarded as but a contribution to the study.

The growth in question occurs in three zones, Lithothamnium Lenormandt,
the uppermost, Lithophyllum inerustans, the second, and the .third,
LTithothamnium polymorphum, appears only when low-water mark is
reached. All three plants resent desiccation, and cannot bear being dried
up. L. polymorphum, and, to a lesser degree, L. Lenormundi, prefer shade ;
but LZ. cerustans thrives in the bright sunshine of shallow rock-pools. The
zone of LZ, Lenormandi occurs on damp rocks slightly above half-tide level,
at which height moisture is local, being found in fissures, on shady vertical
surfaces, or under the foliage of the larger algae. The zone is more extensive
than at first sight appears, and is probably widespread in the British Isles.
L. incrustans follows. This is abundant in all the rock-pools, and is by far
the commonest species in the district. Apart from its growth in pools,
L. wnerustans first appears in chinks and hollows in the lower half of the
littoral region. As one descends the shore the crusts become larger and
more widely spread; and on reaching the Himanthalia level they form large
sheets, filling up interstices between limpets, barnacles, and Ral/sia clavata.
At low-water mark the plant is joined by ZL. polymorphum, the red warty
thallus of which is at once distinguishable from the paler L. inerustans,
though the latter at this level assumes its true matve-pink colour, in contrast
to its almost white appearance higher up. JZ. polymorphwm extends into
the sub-littoral region; Z. incrustans probably does the same, but its growth
here on exposed shores was not investigated.

The Lithothamnium vegetation described above is specially characteristic
of exposed, somewhat bare rocks, where algae such as Laurencia and
Himanthalia are poorly developed, but where there is a large growth of
the short form of Corallina. In localities where there is less exposure, or
where shrubby ‘and foliaceous algae occur in plenty, the Lithothamnium
vegetation is poor: some traces of the LZ. Lenormandi and L. polymorphum
zones may be found, but L. incrustans usually disappears altogether.

Vegetation of Rock-pools.

Several different types of pools may be distinguished according to their
elevation, and to the geological nature of the shore. A number of other factors
must also be taken into consideration—namely, the size, depth, and configu-
ration of the pools, and conditions of temperature, illumination, and drainage.
Whilst much of the pool-vegetation is perennial and more or less constant,

a large part is transient and varies considerably, not only from month to
RB. I. A. PROC., VOL. XXXI. FB 15

15 42 Proceedings of the Royal Irish Academy.

month, but from one year to another. A detailed study and analysis of the
vegetation was impossible; but a series of observations was made, and a
general account is given below.

In the upper pools an encrusting vegetation is always conspicuous. At the
highest levels Hildenbrandtia prototypus is tound, especially on rugged rocks
and on exposed cliffs. Slightly below, and generally in flatter areas, Ra/fsia
verrucosa appears, covering the bottom of shallow pools with a thick crust,
and often completely ousting Hildenbrandtia. At a lower level (probably
that of ordinary high-tide), Zithophyllum incrustans begins to develop, first as
avery thin crust which does not fruit; then rapidly increasing in vigour on
the lower rocks, it passes into the Lithothamnium association (p. 41). Ralfsia
and Lithophyllum are, in the upper shallow pools, in competition. The
former cakes off with age, allowing Lithophyllum for a time to get the upper
hand. Ralfsia, however, tolerates more fresh water, and probably grows more
rapidly. Both can withstand intense insolation, and often form large sheets
without any protecting vegetation whatever. The water of these pools
becomes in summer very warm.

With regard to the upright vegetation, Hnteromorpha intestinalis is often
alone in the highest pools, but is joined by Cladophora sericea, Chaetomorpha
aerea, and Seytosiphon lomentarius, where the salt-water is constantly renewed
by spray and splashing. Below these a series of fairly characteristic pools,
situated about high-water level, is reached, which are well supplied with
seaweeds during winter and spring. But in summer the larger algae are
scarce, or represented by a few hardy species, usually infested with Diatoms
and Cyanophyceae. The dominant species are :—

Cladophora rupestris. Gigartina mamillosa.

C. sericea. Laurencia hybrida (except summer).
Scytosiphon lomentarius. Polysiphonia fruticulosa.

Leathesia difformis. Dumontia filiformis (except summer).
Gelidium sp. Corallina officinalis.

The additional winter and spring flora need not be listed. The pools are
not always replenished in calm weather, and are distinctly brackish ; they are
about 6 inches deep, and commonly run parallel with the shore.

‘At alower level the typical purely marine rock-pools commence, in varied
form, and with abundant vegetation. They are much more difficult to classify,
and have a constantly changing flora. With a sufficient depth, large algae,
such as Halidrys, Cystoseira fibrosa, &c., are plentiful, and provide shade; hence
almost any of the shade-loving Florideae (except those which require daily
exposure to the air) may be met with. If shallow, the flora is more limited,

Clare Island Survey— Marine Algae. 15 43

though sporelings and young plants of a very large number of species occur,
In Vancouver, Henkel (06) has worked on the structure of rock-pools; and
Skinner’s paper (03) is one of the only attempts to analyse the flora and the
conditions obtaining. His conclusions, equally applicable to the British coasts,
are as follows:—In general, the higher the elevation of the pool, and the
less exposed to wave-action, the fewer the species found, though the number
of individuals may be great. The more gradual the slope, and the rougher
and more irregular the sides, the more abundant the plant-life. A perpendicular
or receding wall is unfavourable for the location of plants.

An attempt is made below to indicate the characteristic species of ordinary
rock-pools not more than 18 inches deep. A complete list is out of the
question. In a general way they are at their best in early spring. During
the dark days of winter many of the Florideae, which at other seasons thrive
in more shady spots, are found in shallow pools (e.g. Phyllophora rubens,
Plocamium coccineum, Laurencia obtusa, Rhodomela subfusca, Halurus
equisetifolius). Hence in winter and spring the Florideae are markedly
dominant. In March and April many transient species develop ; and in May
and June brown algae are abundant, and also species of Cladophora. The
Florideae in shallow pools are in summer of poor colour; and a great decrease
in the number of species is noticeable. Ulva and Enteromorpha spp.
may be dominant in August and September. Excluding large species, such
as Fucus, Laminaria, &c., and small epiphytes like Myrionema, Elachista,
and Chantransia, the most typical species are as indicated in the list on
pp. 44, 45.

Cave- Vegetation.

As would be expected from the conditions obtaining in caves, shade-loving
littoral plants abound; whilst in addition species from the sub-littoral region
also occur. Provided wave-action is not too severe, the cave-flora is often
full of interest biologically, long tunnel-like caves, with pools and boulders,
being particularly instructive.

Though the Clare Island caves are neither numerous nor extensive, their
flora is characteristic and worthy of record. ‘They may be roughly divided
into two sets, namely, exposed and: sheltered. The flora of caves fully
exposed to the sea is usually poor, incrusting species on the walls being at
times the only vegetation present; but sheltered caves, especially if stocked
with boulders, are rich in species, and possess the shaggy growth of which
Plumaria is typical, as well as the mossy and incrusting coverings supplied
respectively by Rhodochorton Rothvi and Lithothamnium polymorphum,

Characteristic Vegetation of Rock-pools.

Feb., 1911. | April, 1911. July, 1909.
| Roonah Pt. |Clare Island. Clare Island.

Uct., 1910.
Clare Island.

Monostroma Grevillei,
Enteromorpha clathrata, .
E. compressa,

Ulva Lactuca,
Rhizoclonium implexum, .
Cladophora pellucida,

C. rupestris,

C. sericea,

C. glaucescens, .

C. albida, a

C. lanosa, .

Codium adhaerens,

C. tomentosum,

C, mucronatum,
Dictyosiphon foeniculaceus,
Litosiphon pusillum,
Phloeospora brachiatum,
Scytosiphon lomentarius,
Ectocarpus confervoides,
E. fasciculatus,

E. granulosus,

Pylaiella litoralis,
Ismophloea sphaerophora, .
Myriotrichia claviformis,
Sphacelaria cirrhosa,
Cladostephus verticillatus, .
Chordaria flagelliformis,
Mesogloia vermiculata,
Castagnea virescens, .
Leathesia tuberiformis,

Dictyota dichotoma, .

Porphyra leucosticta,
P. umbilicalis, .
Pterocladia capillacea,
Gelidium pulchellum,
G. latifolium,
Chondrus crispus,
Gigartina mamillosus,

Phyllopkora rubens,

ie, 8

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Clure Island Survey—Marine Algae.

15 45

Phyllophora membranifolia,
Cystoclonium purpurascens,
Calliblepharis jubata,
Rhodymenia palmata,
Lomentaria articulata,

L. clayellosa,

Chylocladia kaliformis,

C. oyalis,

Plocamium coccineum,
Nitophyllum punctatum,

N. laceratum,

Delesseria sanguinea,

D. ruscifolia,

D. hypoglossum,
Rhodomela subfusca,
Laurencia obtusa,

L. hybrida,

L. pinnatifida, . fs
Polysiphonia urceolata,

P. nigrescens,

P. Brodiaei,

P. fruticulosa, .
Pterosiphonia thuyoides,
Dasya arbuscula,
Spermothamnion ‘Turneni, .
Griffithsia setacea,

Halurus equisetifolius,
Monospora pedicellata,
Plumaria elegans,
Ceramium rubrum,

C. Boergesenii, .

C. ciliatum,

Dumontia filiformis, .
Dilsea edulis,

Furcellaria fastigiata,
Lithophyllum lichenoides, .
Corallina officinalis,

C. squamata,

C. rnbens, 5

| Feb., 191. |
Roonah Pt. (Clare Tsland.

|
April, 1911, | July, 1909.

Clare Island.

Oct., 1910.
Clare Island.

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mS OS OS oo OM

x

x

x xX X X xX

15 46 Proceedings of the Royal Trish Academy.

1. Lrposed Caves.—Several of these occur between Portlea and the light-
house, and are accessible at low tide. The walls, almost up to the roof, are
covered with encrusting organisms representing algae, lichens, and sponges ;
and except for local patches, shrubby species are absent. In the following
list, the first four are dominant, occurring roughly as bands from above
downward in the order mentioned, whilst the three last are scattered
irrecularly a short distance above high-water mark :—

Hildenbrandtia prototypus. Lithothamnium laevigatum.
Verrucaria sp. Ralfsia clavata.
Lithothamnium Lenormandi. Cruoria pellita.

L. polymorphum.

Large sheets of sponges also occur, and amongst these Halichondria
ponicea, frequently with Rhizoclonium Kerneri f. endozoica, is abundant.

Small patches of a very short growth of the following fruticulose species
are occasionally found, their presence probably indicating local shelter :—

Phyllophora rubens. Plumaria elegans.
Chylocladia ovalis. Corallina officinalis.

Where fresh water exudes from the roof or walls, streaks of Cladophora
rupestris, if the exposure be not too great, mark its presence, and at times
Rhodochorton floridulum in addition. Pools are generally lacking; if present,
their flora resembles that given below for sheltered caves.

2. Sheltered Caves.—Several types of these may be distinguished according
to the nature of the shore and the manner in which they receive protection.
In our area the two following only need be mentioned:—(a) Open caves
on exposed coasts, protected by rocks at the entrance (Roonah Point) ;
and (0) high-level caves with the entrance at, or just above, high-water
mark. In the former there is often a variety of ground and vegetation,
especially if boulders and pools occur; in the latter the conditions are more
uniform.

(a) The encrusting vegetation at Roonah Point is the same as that on
exposed coasts, but less extensive; the mossy growth of Rhodochorton Rothii
is abundant on the drier boulders and on the upper parts of the walls;
Sphacelaria britannica and various Cyanophyceae occur with this species, and
Phyllophora Traillii is found in patches. An abundant growth of shade-
loving Florideae follows at a lower level, covering rocks, boulders, and
shallow pools, Chylocladia articulata, Delesseria alata, Nitophyllum laceratum,
Polysiphonia wreeolata, and encrusting species such as Lithothanniun

Clare Island Survey— Marine Algae. 15 47

Lenormandi and L. polymorphum beng the most usual. The pool-flora
consists chiefly of the following species :—

Phyllophora rubens. Polysiphonia urceolata.

P. membranifolia. Chylocladia articulata.
Rhodymenia palmata. Griffithsia setacea.
Nitophyllum laceratum. Pterosiphonia parasitica.
Delesseria sanguinea. Lithophyllum incrustans.
Plocamium coccineum. Lithothamnium polymorphum.

(6) A small tunnel-like cave on the south side of Portlea was carefully
investigated each season. Though short, it was the only really dark cave
examined, and its flora proved of considerable interest, three of the rarest
algae of the island occurring in it. Near the mouth of the cave the shaggy
growth lining the walls consisted of Cladophora rupestris (dominant) and
Plumaria (sub-dominant), with the following species scattered freely amongst

them :—

Ectocarpus Holmesii. Polysiphonia macrocarpa.
Gelidium pusillum. Rhodochorton floridulum.
Rhodymenia palmata. Callithamnion scopulorum.
Polysiphonia urceolata. Spermothamnion Turneri.

A little further in, Plumaria becomes dominant, and, with the exception of
Cladophora rupestris, which assumes a thin feebly branched habit, the other
algae gradually disappear. On the bottom and at the margins of pools,
Derbesia marina is found, and on the sloping sides Codiwm amphibiwm under
the drip of fresh water. At the further end, the walls are mostly clothed with
a pure growth of Plumaria, though patches of Lithothamnium Lenormandi var.
squamulosa exist, and Derbesia occupies the water-edges. The pool-flora is
remarkable ; Plumaria, Ceramium acanthonotum and Polysiphoni” macrocarpa
are common, whilst further in there is a felt of the minute Ptilothamnion

lucifugum (sp. Nov.).

(b), Sub-littoral Region.

The sub-littoral vegetation of exposed coasts is difficult of exploration. In
calm weather much may be learnt from a boat at dead low water, but in a
general way a small boat and a hand-dredge are of little use. Two associations
only are described below, these being the only ones which were definitely
investigated. Colonies of the beautiful Cystoseira ericoides are plentiful off
the shore, in company with such plants as Saccorhiza and Himanthalia, but
unfavourable weather baftled attempts at their study.

15 48 Proceedings of the Royal Irish Academy.

Laminaria Association.

Clare Island is girdled at low-water mark with a fine belt of Laminaria, —
which descends on all sides deep down into the sub-littoral region. With the
exception of the somewhat doubtful Z. hieroglyphica, all the English species ©
occur, so that the west of Iveland presents the exposed Laminaria vegetation
of the British Isles in its most varied form. Though a submerged association,
each species reaches to the top of the sub-littoral region, and is thus visible
during the lowest spring-tides. Alaria and Z. digitata are uppermost, and
are often uncovered; Saccorhiza and ZL. saccharina follow, and usually show
in calm weather, whilst the erect stipes of Z. Cloustoni protrude in favoured
localities only. Alaria, Z. digitata, and L. Cloustoni form well-marked belts
which are always to be found on the type of shore that they respectively
require, whereas the growth of Saccorhiza, and ZL. saccharina, though at
times plentiful, is scattered and local.

A steep coast with almost perpendicular rocksis the A laria shore par excellence,
though L. digitata is also usually present. On sloping rocks the same
vegetation obtains, the amount of Z. digitata increasing as the shore becomes
less steep, till at length Alaria disappears altogether. JZ. digitata often
descends into many fathoms (at least 8); but Alaria appears to form a shallow
belt in the uppermost part of the littoral region. Z. Cloustoni enjoys the
Atlantic swell, but prefers a flat bottom, and is absent on steep rocks.
Within the shelter of a reef, or in other similarly protected spots, the plants
are found nearer the surface of the water, and at the lowest tides the tops of
their stipes protrude. In such positions the association may be conveniently
examined from a boat (e.g., at Roonah Quay).

A flat or gently sloping bottom with a certain amount of shelter is most
suitable for Saccorhiza and L. saccharvina. In certain spots on the south shore,
and especially in channels between the rocks, the former grows in plot-like
areas, which may be easily examined from the rocks in quiet weather. It is
also plentful in the shallow water off Kinnacorra. Streak-like patches of
L. succharina have also been noted in these localities, but the plant is more
characteristic of quiet regions.

As stated on p. 15, the Laminaria association, though it may be partially
uncovered during spring-tides, marks in reality the upper limit of the sub-
littoral region. The amount uncovered varies with the exposure. In the
most boisterous spots Alaria ascends high, and consequently, if a spell of
quiet weather synchronizes with spring-tides, a considerable amount, 5—5 feet,
is left bare. Borgesen mentions a case in the Faerdes, where Alaria flourished
at a level above that of high-water line. Nothing like this has been seen in

Clare Island Survey— Marine Algae. 15 49

Ireland, and it probably only occurs where great exposure is coupled with
a wet, foggy climate.

The usual epiphytes characteristic of the species occur. Litosiphon
Alariae, Ectocarpus fasciculatus, and Myrionemaceae are frequent on Alaria—
Chantransia Alariae rare. The laminae of JZ. digitata commonly bear
a copious growth of Ectocarpi, Ceramia, Callithamnion tetragonum, and
other small plants, while the stipes are usually clean. The rugged stems of
L. Cloustoni, on the other hand, are densely clothed with Florideae, which
show a tendency to definite sequence from above downwards as pointed
out by Berthold (82) and Bérgesen (05). As a rule this sequence is as
follows :—

Rhodymenia palmata.
Polysiphonia urceolata.
Delesseria sinuosa.
Delesseria alata.
Heterosiphonia coccinea.

But in addition to the differences due to seasonal variations many irregulari-
ties were noted. Other characteristic epiphytes are :—

Codium tomentosum. Ptilothamnion pluma.
Callophyllis laciniata. Ptilota plumosa.
Rhodymenia palmetta. Plumaria elegans.
Lomentaria articulata. Rhodochorton parasitica.
Plocamium coccineum. Cruoriella Dubyi, r.
Nitophyllum laceratum. Cruoria pellita 7.

N. uncinatum (autumn). Petrocelis Hennedyi 7,

N. Bonnemaisoni, +. Dermatolithon pustulatum,

Saccorhiza is usually fairly clean, as is also ZL. saccharina in exposed
localities.

Comparison with other Countries.—As far as Alaria, LZ. digitata, and
L. Cloustoni are concerned, the above vegetation agrees well with that
described by Borgesen for the Faerdes, though in that region it ascends
somewhat higher on the shore. Saccorhiza is entirely absent; but this is
compensated for by the presence of two additional species, A. Pylait and
L. faeroensis, the latter being confined to sheltered coasts. Bérgesen, in an
interesting paragraph on the effect of wave-action on Laminariae, points out
that the pliable stipes and fronds of Alaria and JL. diyitutu are able to resist
the violent conditions of a steep shore, and where the breaking of the waves
is felt; whilst the stout and comparatively rigid stems of LZ. Cloustoni are
suited to the strong pull of the rollers in deeper water.

R.I,A, PROC., VOL, XXXI. G 15

15 50 Proceedings of the Royal Irish Academy.

_ The Swedish vegetation described by Kylin is very different. Alaria is
absent, and the verticai rocks are clothed with Z. digitata and L. saccharina
var. bullata. In the most open spots LZ. digitata var. cuneata is dominant.
The Z. Cloustoni vegetation is entirely separate from Z. digitata, being found
only in the deeper part of the sub-littoral region, appearing first in about
15 m. of water. Boye’s account of the Norwegian flora (according to
Boérgesen’s summary) agrees with that of the Faer6es; and Kylin’s notes on
the vegetation near Bergen (10) indicate the preponderance of Alaria and
L. Cloustont. The Iceland vegetation resembles that of the Faerées, but is
enriched by the presence of L. nigripes and Saccorhiza dermatodea. Tn the
south of England Alaria is rare except in Cornwall, but apart from its
absence the Clare Island vegetation agrees well with that noted in Dorset.
The exposed rocky coasts of Ireland are, however, more favourable for an
extensive Laminaria vegetation, and are highly suitable for a growth of
Alaria,

Encrusting Alga Vegetation (sub-littoral).

The Lithothamnium vegetation of the littoral region extends downwards
into the deepest parts of the sub-littoral, but, owing to the difficulty of dredging
amongst a dense growth of Laminaria digitata and L. Cloustoni, it is difficult
to ascertain the amount of growth and the relative abundance of the species.
An extensive coating of calcareous algae is, however, present, and on exposed
coasts probably occupies a large part of the available rock-surface, though soft
encrusting species, such as Cruoria pellita, Cruoriella, and Peyssonnelia, occur
with it. Lithophyllum incrustans enters the sub-littoral ; but, as far as could be
seen, the Lithothamnium ‘band at the lowest tide-level consists mainly of
L. polymorphum, and this extends downwards for several fathoms. Other
species dredged were LZ. laevigutum and L. compactum. The fruticulose
calcareous algae, such as L. calcareum and L, fasciculatwm, are characteristic

of sheltered shores (p. 69).

B.—Sheltered Coast Series.
(a) Littoral region.

Several of the associations found on sheltered coasts have been already
dealt with. In some cases the principal differences noticeable in passing from
the open shores to quieter conditions have been pointed out, so that re-descrip-
tion is unnecessary. In other cases, though’ theassociations have been described,
their growth in sheltered localities requires special notice; yet other
communities are peculiar to such regions,

Clare Island Surveyj—Marine Algae. 15 51

Hildenbrandtia—Verrucaria Association.

Brief notes may be added to previous remarks with regard to this
association (p. 19). On the sheltered shores of Clew Bay the same species
are present, especially on boulders and smooth rocks. Where these are absent
a discontinuous growth on stones and pebbles occurs, and in such spots
Hildenbrandtia is joined near low-water mark by Porphyrodiscus simulans and
Fihododermis elegans (plants hardly distinguishable in the field), and also by
Ralfsia clavata. H. prototypus itself, moreover, appears to extend to the
sub-littoral region (cf. p. 20). The difficulties of obtaining satisfactory
material and of distinguishing the species when collecting, make it no easy
matter to gain a true idea of the different societies. It is certain, however,
that in these localities the Ralfsia clavata vegetation is one with the
Hildenbrandtia association, and that it forms a part of it. It is further
evident that a vegetation composed of soft encrusting algae and lichens
extends uninterruptedly from high-water mark down to the Lithoderma
association of 5-8 fathoms. The details require working out, but roughly
the principal species form zones as follows :—

Hildenbrandtia prototypus (upper littoral).
Verrucaria mucosa (middle littoral).

Ralfsia clavata (lower littoral).

Cruoriopsis Dubyi (shallow sub-littoral).
Lithoderma fatiscens ? (shallow sub-littoral).

Fucaceae Association (sheltered).

The growth of Fucaceae on flat sheltered shores is exceedingly luxuriant,
and often forms a conspicuous feature of the landscape. The indispensable
factor is good anchorage. On flat shores, where wave-action is slight stones
are sufficient to supply this necessity, but where rocks and stones are wanting
Fuci are conspicuous by their absence. The association was studied especially
in Achill Sound, the north part towards Inishbiggle and Bellacragher Bay
having been examined, as well as the southern portion towards Achillbeg.
As far as was seen the Fucus growth in Clew Bay is of a precisely similar
nature.

The association is composed of the usual five species in their normal
sequence (see p, 23), and where fresh-water streams occur, the sixth species,
F. ceranoides, invariably appears. In some places the zones are fairly sharply
defined ; in others they are much less distinct, and each zone overlaps the
next. A certain amount of irregularity exists too as to the order in-which
Ascophyllum and 2. vesiculosus occur, The former usually commences above

G2

16 52 Proceedings of the Royal Irish Academy.

the latter; but not infrequently /. vesiewlosus forms a very wide zone reaching
from F. spiralis down to F. serratus, with Ascophyllum scattered amongst it,
or forming more or less of a band in the upper part. The reason for this is
explained later. At times one or more of the species may be absent, and this
may almost always be traced to lack of suitable means of attachment at the
appropriate level. In Achill Sound, for instance, the association often stops
abruptly with Ascophyllum or F”. vesiculosus, owing to the absence of stones at
the level at which F! serratus should occur. In other places Pelvetia and
I’ spiralis are only feebly developed owing to the lack, in the upper part of the
shore, of stones of sufficient size.

Some idea of the width of Fucus association in Achill Sound will be gained
from the following readings :—

A. Sloping shore near Achill Bridge with a narrow band of Fucaceae :—

Width of zone.

Pelvetia, . ; ; ; F ‘ ; . 2-8 feet.
F. spiralis, ‘ : 5 : : : ae ND=6 Be
F. vesiculosus, . ‘ : ; . é . 10 a
F. vesiculosus and Ascophyllum mixed, ‘ a al) 3
F. vesiculosus, . j j 7 ‘ : ere al) FA
F. serratus, ‘ j ; ; ; ; « 210 Pr

B. Flat shore with a very wide Fucus association ; about 1 mile south of
Achill Bridge :—
Width of zone.

Pelvetia, i : : 6 j n : 5 yards.
EF. spiralis, : ; ; ; ‘ ; > LOM IRS
Ascophyllum, . ; : ; : : « 64 OCS
Ascophyllum and F’. vesiculosus, ; : at (OOR ES
F. vesiculosus, : 6 c : ; s, Ole
F. vesiculosus, F. serratus, . F : . oO) ep

The above figures represent fair average readings for sloping and flat
shores respectively, and serve to show that the horizontal range varies directly
with the amount of slope. On very flat shores even wider bands exist. At
Mulranny, for example, on a flat stretch of rocks and stones at high-water
level, a growth of Pelvetia 80 yards wide was noted: this was followed by a
sudden increase in the fall, and the succeeding band of & spiralis was only 3-4
yards in width.

With regard to exposure, all the species composing the association can
tolerate the extreme shelter of the inner part of Clew Bay. On passing from
this region to the more open, beyond a slight change in form, there is no

Clare Island Survey—Marine Algue. 15 53

inarked difference in the vegetation as long as Ascophyllum remains. A
slight exposure, however, is sufficient to affect this species, and with its
disappearance the association is robbed of one of its most conspicuous elements.
Ascophyllum begins to disappear on the outer sides of the islands, but
persists in all cases on the inner sides. West of the islands it is only found
in certain places, though this perhaps is largely due to the lack of good
mooring. But, in spite of this, there is no question whatever that in the
Survey-area Ascophyllum is far more susceptible to exposure than F. vesiculosus.
This is in agreement with observations in other parts of the British Isles, and
also with accounts that have been given of the Norway Fucus-vegetation
(Boye, 94, and Kylin, ’10). The conditions described for the Faerces,
where Ascophyllum is the less susceptible of the two, are very remarkable,
and, as far as known, unique. The result of exposure in producing a change
in form in the various constituents of the association is very marked. It is
best seen in F. spiralis. F. vesiculosus also produces a wealth of form, but
the variations are more difficult to connect with external conditions.
Remarks on these points occur in the notes on each species given later.

Fucus Farms.—The botanical features of the plots, planted with stones in
order to obtain a growth of Fucus for use as manure, may be dealt with here.
The farms are formed on flat stretches of sand exposed at low water. They
may either extend from the shore, or be laid out as isolated patches in the
middle of the strand. The rapid colonization, and the luxuriance of the
subsequent vegetation, prove beyond question the effect of anchorage.

The stones are covered mostly by £. vesiculosus, though a small amount of
Ascophyllum sometimes occurs. At the lowest levels there are occasionally
encircling belts of F. serratus, but the stones are not as a rule placed
sufficiently low for this species. Ff. vesiculosusis very luxuriant, forming large
tufts, bright yellow in summer and deep green in winter, with numerous
bladders and abundant fruit. 2 serratus, when present, grows equally
vigorously, with fine broad fronds often a yard in length. The plants are
cut in February after two full years’ growth, and the stones turned over for
a new crop of sporelings to develop.

It is somewhat remarkable that this artificially produced vegetation con-
sists of a practically pure association of F. vesicwlosus, forming thus a striking
contrast to vegetation obtaining on mud-flats (eg., Belfast Lough, South-.
ampton Water). The latter are colonized by mussels, and these support a
pure growth of Ulva Lactuca. Ulva, and many other adaptable algae, are
present in Clew Bay, but Fucus has complete sway on the stone plots. It
would be interesting to know whether Fucus would develop if stones of
sufficiently large size could be maintained on the mud-flats of Belfast Lough.

15 54 Proceedings of the Royal Irish Academy.

A few notes are appended on the species composing the association.

(a) Pelvetia canaliculata.—This is less variable than any other species. In
the sheltered parts of Clew Bay and in Achill Sound, it usually occurs on the
irregularly scattered stones, and consequently the zone is interrupted. The
growth is entirely flooded at spring-tides, but at neap-tides the upper part
of the belt is unmoistened, the plants remaining quite dry, and brittle for
several days in succession. Though Pelvetia may form a zone several yards
wide, its vertical distribution is not more than 14-2 feet. It fruits freely
during summer and autumn; but the growth being more interrupted
and not so Inxuriant as on open shores, the orange-yellow band is not so
conspicuous.

(b) F. spiralis—Not only is F. spiralis found in all the sheltered parts of
Clew Bay, but it is capable of growing on peat and loam, and ranges from
such situations to the roughest and most exposed parts of the open coast
(cf. Borgesen, ’05, p. 746). Leaving aside its growth on peat (see p. 124), we
find that on flat shores the plants are usually stone-attached, and do not form
so dense a vegetation as when growing on rock. For this reason they become
drier during the long exposure to the air, and are shorter and less branched.
When the shore is composed of rocks and large stones, the growth is more
vigorous; and under these conditions the plants attain their maximum size,
the fronds being wide, much branched, and bearing large fleshy conceptacles.
This form remains as long as the conditions are sheltered, but when exposure
is experienced, or where a current strikes the shore, the plants become shorter,
though they usually retain their bushy habit.

The belt formed is much wider than on steep open coasts, and its width is
proportional to the degree of slope. In Achill Sound it varies from a few
feet to 10 yards, and usually forms a pure growth, though /. vesiculosus and
Ascophyllum occasionally intrude into the lower part. The fruiting season
on quiet shores appears to extend over a slightly longer period than on those
which are more open. In Clew Bay it commences in May, and does not cease
till autumn. On sheltered shores also, a difference in colour is noticeable
during the autumn, the plants turning a bright rusty brown. The same
peculiarity has been observed on the south coast of England; and it serves to
distinguish at a glance F. spiralis from F. vesiculosus, the latter being usually
yellow or only slightly brown. In some places two sharp zones of colour are
produced. Another feature, which on flat shores is very characteristic of
F. spiralis, is the presence of long blister-like swellings on the fronds. ‘These
are invariably present in the inner part of Clew Bay, and are entirely absent
from the short forms found on Clare Island. Sauvageau has lately examined
I, spiralis (= F. platycarpus, Vhur.) with great thoroughness (’08).

Clare Island Survey—Marine Algae. 15 55

(ec) Aseophyllum and F. vesiculosus—The irregularities in the vertical
range of Ascophyllum and F. vesiculosus have been noted by several writers.
Borgesen calls attention to the difference in the observations of Strémfelt in
Iceland, and Rosenvinge in Norway; and records irregularities noted by
himself in a single locality in the Faerdes. He comes to the conclusion that
the difficulty may be explained by the factor of exposure and small differences
in local topography. No doubt this solution is correct with regard to many
localities; but in Achill Sound it was found inadequate, and a further
explanation had to be sought for. It has always been assumed that in
England the Ascophyllum zone begins slightly above that of F. vesiculosus,
and Miss Baker (’09) gives figures which support that view. This sequence
is found on the stone embankments of Achill Bridge and in other places; but
on the shores in Clew Bay, as often as not, the reverse order obtains. The
explanation, so far as the sheltered waters of the Survey area are concerned,
was found to be largely one of anchorage. Ascophyllum requires a stronger
mooring than Fucus; and on the sandy shores of Clew Bay where the stones
in the upper part of the beach are small they are insufficient for Ascophyllum,
though well able to provide a mooring for a short growth of Fucus. The
absence therefore of the Ascophyllum-zone, or the presence of scattered plants
only, is explained by the absence of rock and large stones at the right level,
or the presence of isolated rocks only. In many parts of the Sound the
anchorage is sufficiently good to allow Ascophyllum to flourish at all levels,
and then the normal sequence is almost invariably maintained. Very small
stones suffice for both F. spiralis and F. vesiculosus; but it is unusual to find
even young plants of Ascophyllum on stones. The last-named shows a decided
preference for boulders, from which it hangs in festoons. The stone-attached
Fucus-vegetation is essentially one of very sheltered water, and could not
exist were there much wave-action. Where the stones are light the growth
is small, and if, by reason of a long spell of quiet weather, an extra amount
of foliage should be produced, a number of plants will be displaced with the
first ruffling of the water.

Ascophyllum fruits in late winter and spring. In summer and autumn a
large amount of vegetative growth takes place; and young receptacles are laid
down in autumn. The latter begin to ripen in March, the main crop of spores
being liberated in April and May. The effect of exposure has been dealt
with above. ;

The Fucus vesiculosus belt is the widest. On flat shores it ranges from
20 to 80 yards, in the upper part usually accompanied by Ascophyllum, but
near low water often pure. No attempt was made to determine all the forms ;
but the most abundant is the ordinary type. Var. vadorwm is also common,

15 56 Proceedings of the Royal Irish Academy.

and var. Jaterifructus not infrequent. In many localities var. a@illaris is
found, which under certain conditions passes into F. volubilis, Huds. The
latter in its typical form was not noted in the area; but the salt-marsh
plant var. baltica is abundant. This, together with a peculiar variety named
muscoides, is dealt with later (p. 80).

(d) Fucus serratus. Whilst Ascophyllum enjoys hanging from boulders,
F, serratus prefers to lie flat. Occasionally it is found growing on sand-covered
rocks, and then rests on the bare sand. It is found on all sheltered coasts
where there is appropriate anchorage; but in many parts of Clew Bay this is
wanting; and the pebble-attached association sets in below F. vesiculosus,
F, serratus forms a band which unites the littoral and sub-littoral regions.
The fronds are wider on sheltered than on exposed coasts ; and on the whole
it is the least variable Fucus.

Sub-vegetation— When growing on sloping rocks a luxuriant undergrowth
of various algae is found; but when attached to stones, or where much sand
occurs, extraneous species are scarce, Amongst those almost constantly
present are :—

In upper part. In lower part.
Hildenbrandtia. Cladostephus spongiosus.
Catenella. Ulva.

Gelidium pusillum. Ceramium rubrum.
Cladophora rupestris. Chondrus.
Gigartina.

C. rupestris,

On the more open shores where clean rocks are prevalent, the Laurencia-
Gigartina vegetation often forms the main undergrowth, though upward
extensions of the Corallina-Lithothamnium association are also frequent.
Amongst these,such sub-littoral or shade-loving plants as Chylocladia articulata,
Delesseria alata, and Plumaria occur, with many odd plants of various
communities. In sandy places a Rhodochorton floridulum vegetation is often
developed, and this ousts many of the other species.

Epiphytes—These are likewise fewer in very sheltered than in moderately
open localities. In the quiet reaches of Clew Bay, Pylaiella is always present,
and forms in spring and summer large floating masses. Other frequent
epiphytes are :—

Dictyosiphon foeniculaceus. Ectocarpus siliculosus.
Ceramium rubrum. EK. tomentosus.
C. Boergesenii. E. fasciculatus.

In late summer blue-green algae are much in evidence, Calothrix
confervicola and Ltivularia atra occurring everywhere, often accompanied by

Clare Island Survey—Marine Algae. 15 57

large masses of Lyngbya majuscula. The more open parts of the bay show,
with the exception of Dictyosiphon and Cyanophyceae, which are rare or
absent, the same epiphytes (see also p. 25).
For the comparison of the present association with that of other countries,
see p. 26.
The Lichina Association (sheltered).

Locally distributed on sheltered and semi-sheltered localities (Clew Bay,
Achill Sound, Bellacragher Bay). See notes on p. 26.

Porphyra Association (sheltered coasts).

The growth of Porphyra found in many sheltered places, though not noted
by previous writers, is very characteristic and worthy of record. It is found
on two types of shore, viz. (1) gently sloping beaches of low rocks and stones,
and (2) sandy bays where half-buried rocks are present. The growth
occurs more or less throughout the year, though it appears to be more abundant
in spring and autumn than in summer. On both shores it is usually
accompanied by various forms of Hnteromorpha intestinalis and LE. linza.

On beaches composed of stones and flat rocks the association usually fills
up the gaps between Fucus. The latter is confined to the larger rocks, whilst
Porphyra, which extends from below /. spiralis down to low-water mark,
occupies the smaller stones and rocks, though it also occurs epiphytically on
Fucus. The amount of growth noted varied considerably on different occasions,
as did also the size and form of the plants. In summer it is mostly confined
to the lower levels, where it may form a distinct belt. This type of growth is
well seen at Louisburgh (immediately east of the Bunowen River), also on the
inner side of Bartraw and on Annagh Island, where wave-action is entirely
absent. Other parts of Clew Bay, which appeared equally suitable, were entirely
devoid of Porphyra. [n the localities named a strong current runs along the
shore, so that the conditions though quiet are not by any means stagnant, and
this fact may in part explain the vigorous growth, and its absence elsewhere.

The second type of growth referred to, namely that on rocks in sandy bays,
is somewhat remarkable, because the expanded membranaceous thalli have to
endure the constant friction of the sand. In spite of this, however, a very
vigorous and characteristic vegetation is found. The growth is most notice-
able at the sides of low bare rocks or those crowned with a mass of Fucus.
It may be seen thus in many spots in our area, and has been noticed in other
parts of the British Isles. But in addition to this, Porphyra occurs on rocks
more or less hidden by sand, so that at first sight the growth might be taken
for loose fronds that have become embedded. The plants are in reality

RIA. PROC., VOL. XXXI, H 15

15 58 Proceedings of the Royal Irish Academy.

attached to low-lying rocks, and are thus not only exposed to constant sand-
movement, but are liable to be completely buried. On the other hand, with
certain winds, nearly all the sand is removed by the tide; and the thalli lie on
the bare rock. They are also liable to be covered by blown sand. Under
average conditions it would appear that only a few inches at the base of the
fronds are buried, and that the upper part remains free, lying flat on the damp
ground: though one must assume that germination took place on rock.
Associated with Porphyra are Enteromorpha spp., especially the large flat
forms approaching £#. linza. This plant oceurs in the damper positions, being
most abundant in the lower part of the association, and reaching down to the
sublittoral region. In August the Enteromorpha growth was in all cases
much less than in May.

The zone formed by Porphyra on sheltered coasts is more extensive than
in the open. In the sandy bays described above the plant escapes a certain
amount of desiccation, and the result of this is seen in the fact that whilst on
bare rocks it does not exceed the /. spiralis level (at all events during summer),
on sand-covered rocks it frequently reaches Pelvetia. ‘lhe lower limit also
is further than that of the exposed association, for the plant is frequent at
low-water mark, and occasionally extends well into the sub-littoral region.

The form assumed in sheltered localities is that.of the divided and lanceo-
late type, var. daciniata J. Ag. his is specially well developed on damp
rocks and on margins of pools. On drier rocks and with increased exposure
there is a tendency for the fronds to become short and umbilicate. The sand-
rock form of the association is well seen at Mulranny, also between Old Head
and Leckanvy, whilst a small patch exists in the bay on Clare Island.
Though not noted, forma linearis probably exists in winter in the upper
levels, as in exposed localities.

A similar vegetation of Porphyra would, judging by the localities described
by Rosenvinge, appear to be widespread in Denmark (’09, p. 65).

Laurencia-Gigartina Association.

Fairly well developed in many parts of Clew Bay outside the islands. See

p. 39.
Corallina-Lithothamnium Association.

At times feebly developed in the more open parts of Clew Bay. See

Be),
_ Corallina-Cladostephus Community.

In company with the Laurencia community of sheltered coasts there often

occurs a similar vegetation of short dense growth, but composed largely of

Clare Island Survey—Marine Algae. 15 59

Corallina, Gelidium, and Cladostephus, and having a tendency to approach
the Rhodochorton floridulum association. The presence of Cladostephus
spongiosus together with Corallina officinalis is very characteristic of this
vegetation, and hence the name selected.

The community in question is essentially one of flat, sheltered rocks,
avoiding the clean rocks and turbulent conditions enjoyed by Laurencia, but
thriving with more slope and slightly more exposure than R. floridulum. It
occupies the same bathymetric range as Lawrencia pinnatifida, and though
capable of growing in the shallow sub-littoral region, it more often gives place
to Gigartina or Laminaria. At Portlea it is intimately associated with
Rhodochorton, but the two communities are usually sharply defined, and
distinguishable at once to the eye, as well as to the tread.

Though both Corallina and Cladostephus are rock-attached, a thin layer
of sand is often found on the surface of the substratum. Corallina, under
the conditions obtaining, is short and more or less erect, its stiff branches
easily retaining sand and fine debris, so much so that the presence of
blackened sand and particles of decayed matter is almost characteristic of the
community. At the same time it is not truly psammophilous. A vegetation
of the same nature (though differing slightly floristically) has already been
described by me in connexion with the growth of Ulva, and the origin of the
blackened sand is explained (11, pp. 124 and 128).

The Corallina-Cladostephus sward is seldom so extensive as that of
Rhodochorton floridulum, being patchy, and only occasionally forming broad
belts. Gelidium aculeatum is sometimes present in quantity, and C. sqwamata
is common, especially in the more open regions. A very heavy epiphytic
vegetation exists, ef which Hnteromorpha elathrata, Ulva, Leathesia,
Coramium flabelligerum, and C. rubrum are the most abundant. Callithamnion
Hookervi also is found in summer on Cladostephus. In addition to the above,
a large number of sporelings occur. These succeed better on this vegetation
than on Rhodochorton (where sporelings are exceedingly numerous); and
though the plants do not attain their maximum size, they usually fruit, and
are sufficiently large to give distinct patches of colour. Much Cladophora
sericea and C. albida is present in spring ; Ceramium rubrum in various forms
is abundant in summer; whilst in October (1910) a form of Hnteromorpha
clathrate was very conspicuous. In summer Ulva also is present in great
quantity, as has already been pointed out (Cotton *11, p. 128), being saxicolous
or epiphytic.

On Clare Island the association occurs on a small scale at Portlea and
Kinnacorra; and on the mainland at many spots in the outer part of Clew
Bay (Roonah, Louisburgh, Mulranny). A similar vegetation occurs on the

H2

15 60 Proceedings of the Royal Irish Academy.

south coast of England; and though not recorded from other countries, it
probably exists, at all events, on the north of France.

Rhodochorton floridulum Association.

Small patches of this are occasionally found on rocky shores; but it is
characteristic of the sand and low-rock series described later (p. 65).

Sand-Pool Vegetation.
Occasionally met with, but typically developed on sandy shores
(see p. 67).
Cave Vegetation.

The caves of sheltered coasts are dealt with on p. 46.

(b) Sub-littoral Region.
Laminaria Association (sheltered).

The Laminaria vegetation of sheltered shores is fairly well developed. It
is found in many parts of Clew Bay, in Bellacragher Bay, and in parts of
Achill Sound. The characteristic species are L. saccharina and L. digitata,
the latter being, as a rule, confined to localities where current is present. In
the deeper and more open parts, Z. Cloustont exists; but with the appearance
of this species Z. saccharina drops out, and the association passes gradually
into the exposed type.

Whilst on exposed coasts the Laminaria vegetation is typically in belts,
on sheltered coasts it is commonly discontinuous, and occurs rather in plots.
This is mainly owing to the scattered nature of the anchorage. It is found
wherever rocks or large stones occur; and the amount is determined by the
extent of the stony area. In Clew Bay, the hard bottom is found in three
kinds of ground, each of which supports a different type of Laminaria
vegetation. As the latter are determined by definite ecological conditions,
and as, in Clew Bay, they scarcely overlap, it is reasonable to regard them as
three sub-associations.

The sub-association of Laminaria saccharina (most often var. latissima)
oceurs in the inner part of the bay, where the conditions are quiet and the
current weak. The fronds are long and very broad—in extreme cases up to
a yard across. Occasionally the association is pure (except for small species
forming the undergrowth); but as a rule other algae intrude, such as
Cystoseira granulata and Halidrys siliquosa. Rarely the association merges
into the Zostera beds. The second sub-association is characteristic of ground

Clare Island Survey—Marine Algae 15 61

where there is a strong current, and is found typically in the channels of
3 to 5 fathoms between the outer islands. It consists entirely of L. digituta.
The bottom is scoured by the tide; but the larger stones and blocks of rock
support a vigorous growth. The plants are remarkably strong, and in the
deeper parts the fronds often attain a great length. Epiphytic species are
few ; but in such localities the peculiar plant known as Rhodymenia palmata
var. sarniensis is occasionally met with. The third type of Laminaria
vegetation, characterized by the presence of ZL. Cloustoni in addition to
L. digitata, is found only outside the islands. It extends over large areas
in about 7 fathoms, and passes gradually into the exposed vegetation that
occurs further out.

Representatives of these same sub-associations are found elsewhere.
L. digitata is abundant near the south entrance of Achill Sound ; andin the
quiet waters of Bellacragher Bay a distinct ZL. saccharina vegetation exists,
which in several places extends to the shore. In other counties, the sheltered
type of Laminaria vegetation has not received much attention. In the
Faerdes it is well developed, and shows similar variations to those in Clew
Bay. though with floristic differences. Z. jfacroensis takes the place of
L. saccharvina in quiet bays, and L. Cloustoni forms the vegetation of channels.
The Laminaria zone described by Joubin (09) includes patches of LZ. saccharina
attached to stones ou a soft bottom, which obviously correspond to the
sub-association of that species dealt with above.

Encrusting Alga Vegetation.

Occasionally found, but more often on exposed coasts (see p. 50).

Il.—Sand and Sandy-mud Formation.

The present formation is characterized by a large quantity of movable
sand or sandy-mud, in which the vegetation is liable to be partially or
completely embedded. In its extreme form, the shore consists entirely of
this matrix, the algae being immersed in sand, forming, in fact, a sand-binding
community. But the sand formation passes by transitions into the
rock-formation on the one side, and to mud-flats on the other.

As an example of a-sand-binder we may take Microcoleus, whilst
Vaucheria Thuretti supplies an instance of a plant that fixes sandy-mud.
Both form extensive associations. Rhizoclonium riparium also may under
certain conditions form a surface-covering on a shore of pure sand. In the
majority of sand-beaches, however, all vegetation is absent and only begins to
show when solid ground is reached. Where low half-buried rocks occur a

15 62 Proceedings of the Royal Trish Academy.

psammophilous vegetation is found, of which Rhodochorton is a good example.
With extreme shelter, this can form a mossy carpet on pure sand; but as a
rule it is only found on sand-covered rocks, or on small intervening sand-
spaces. The alga is probably in the first instance attached to rock, but as the
plants grow they form adventitious rhizoids and accumulate sand. Being
saxicolous, Rhodochorton extends to rocky shores, where sand is scarce
or even absent. As an association, however, it is only found where this
material is plentiful. Several other psammophilous species accompany
Rhodochorton.

The Corallina-Cladostephus community represents the last stage m the
transition from sand to rock. Though frequent on sandy shores, a bed of
rock is essential for its growth, hence it has been dealt with under the rocky-
shore formation. The sand-pool vegetation is, on the other hand, described
in the present section, as the characteristic species, though attached to rock,
are markedly psammophilous. The sub-littoral associations call for no special
comment, except that the last three are not strictly psammophilous, though
in our district they are confined to sandy areas. They are placed under this
heading for convenience, and therefore provisionally.

The associations and communities recognized in the sand and sandy-mud
formation are as follows :—

(a) Littoral Region.

Rhizoclonium ripariun.
Microcoleus chthonoplastes.
Vaucheria Thureti.
Vegetation of vertical banks.

Rhodochorton floridulum,
Corallina-Cladostephus.

Porphyra umbilicalis.

Sand and sandy-mud series : |
Sand and low-rock series : !

Sand-pool vegetation.

(b) Sub-littoral Region.

Rhodochorton floridulum.
Zostera marina.

Fruticulose Lithothamnium.
Pebble-attached association.
Encrusting algae.
Channel-vegetation.

Clare Island Survey— Marine Algae. 15 63

(a) Littoral Region.
Rhizoclonium riparium community.

The only community found on pure sand in our area is that of Rhizoclonium,
though for this also a small amount of binding material is advantageous.
The vegetation is found immediately below high-water line, and is
occasionally very conspicuons, specially in spring and summer. At Mulranny,
where the shore is unusually flat, Rhizoclonium covers extensive areas, patches
an acre in extent having been noted.!

The underlying sand (or sandy-mud) is for the most part firm, often
bound together by Microcoleus, but in other spots it is loose and apt to
become dry. In either case Rhizoclonium lies as a loose covering, thus
feeling the effect of wind and tide, often being more or less buried. In some
localities the upper part of the association is during neap-tides not wetted at
all, and in this way differs from the somewhat similar filamentous vegetation
which les on wet mud, e.g. on the Vaucheria Thureti association in Achill
Sound (p. 64). Rhizoclonium ripariwm is usually a pure dominant, but
amongst it (especially in the damper parts?) occur Hnteromorpha prolifera;
E. clathrata var., and Cladophora fracta. The blue-green species, so common
in the corresponding association on the salt-marsh, are absent.

A very similar type of growth to that described above has been noted in
Poole Harbour, and on a small scale near the mouth of the River Bann. (See
also salt-marsh formation, p. 79.)

Microcoleus chthonoplastes association.

Of the sand- and mud-binding algae one of the most important is M/iero-
coleus chthonoplastes, a microscopic species of world-wide distribution. The
plants are often completely hidden in the substratum; but their presence
can be detected by the way in which the soil holds together, and peels off in
crusts, when lifted up. Though Microcoleus has not been previously recorded
as forming an association as such, the plant-community has as a fact been
long known, and for a description one cannot do better than quote Gomont’s
note in his revision of the Oscillarieae (09, p. 92) :—

“Le Microcoleus chthonoplastes se rencontre quelquefois a V’état de filaments
isolés mélangés 4 d’autres Algues, ... mais il occupe aussi a lui seul de
vastes étendues sur les cétes marécageuses ou sablonneuses. II] joue un role
des plus utiles dans l’exploitation des marais salants en recouvrant le fond
des bassins ou ocillets V@un tapis compact qui permet d’enlever les cristaux

1 The flatness of the shore at this spot may be judged from the fact that the Pelvetia zone, which
is only about 1 foot deep, is in places oyer 80 yards wide.

15 64 Proceedings of the Royal Irish Academy.

de sel sans mélange de vase. En cet état il forme des assises diversement
colorées, accumulées sur une épaisseur parfois considérable et dont les
supérieures, qui sont les seules vivantes, peuvent étre détachées par larges
plaques et roulées comme des morceaux de drap. Ce végétal meérite
‘done complttement le nom de chthonoplastes (constructeur du sol) qui
lui a été donné par les premiers observateurs.”

In Clew Bay the Microcoleus association was usually found where there
was a certain amount of mud. It occurs in large patches at Mulranny and
also in the Belclare neighbourhood. In the small bay to the north-west of
Achill Bridge it forms a broad band just below high-water line, binding the
upper layer of mud into a firm sheet. It was also noted in several localities
in fairly pure sand, but only as covering small areas.

Various other blue-green algae enter into the composition of the

association, notably :—

In upper parts : In lower parts :
Lynebya aestuarii. Vaucheria Thuretii.
L. lutea. Rhizoclonium riparium.
Microcoleus tenuis. Enteromorpha torta.

Vaucheria Thuretii Association.

This vegetation takes us further still from the pure sand, being found only
where there is a considerable proportion of mud. Future work will probably
show that it should be regarded as an association in the mud-formation.
V. Thuretii forms a dense mossy growth embedded in the matrix, and appears
to cover very extensive areas. Several samples were taken both from Clew
Bay and from the muddy inlets north of the bridge at Achill Sound; and in
each case the mossy tuft consisted of this species, often in beautiful fruiting
condition, and practically pure. The growth is always immersed, the tips of
the filaments alone showing, thus differing markedly from V. coronata, which
forms a clean velvety growth. Felts composed of Rhizoclonium, Chaetomorpha
and Cladophora fracta often lie on top of the Vaucheria, and these, in many
cases, appear to be attached, and not merely drifted fragments; so that it is
possible that careful study would reveal definite societies of other species
amongst the general vegetation of Vaucheria. :

The vertical range of V. Thuwretii is determined by the extent of the sandy
mud. It flourishes in the lower part of the littoral region, and probably
descends to low-water mark. Its upper limit is usually immediately below
F. spiralis, but whether this was due to the lack of sufficient mud or to other
causes in addition (such as long exposure to the air) was not ascertained, On

4

Clare Island Survey—Marine Algae. 15 65

the banks of rivers and where the water is brackish a zone of V. coronata
is the characteristic vegetation near high-water line, but in Achill Sound that
species is absent, and Microcoleus chthonoplastes is the dominant alga.

Vegetation of Vertical Banks.

Vertical peat-banks, abutting on the shores of Clew Bay and Achill,
exhibit a similar vegetation to that described later for the salt-marsh formation
(see p. 82).

Rhodochorton floridulum Association.

This association, though not hitherto described, is very distinct and of
common occurrence in many parts of the British Isles, including the Clare
Island district. tis characteristic of sandy shores where rocks are present,
and is found on moderately open as well as sheltered coasts. Lhodochorton
joridulum is the most important of a group of finely branched, upright-growing
algae, which retain quantities of sand, if they do not actually bind it together,
Other members of the group are :—

Cladophora arcta, Ceramium strictum,
Polysiphonia fibrata, C. cilatum.

In suitable localities the association extends from the Fucus spiralis belt
down to low-water line, but it also descends into the sub-littoral region, being
found abundantly between the islands in Clew Bay. It prefers flat or slightly
sloping shores; on steep shores the sand is washed away, and the plant is
practically absent. Being of small size, Rhodochorton cannot fix sand on the
same scale as phanerogamic plants, nor does it occur on sand apart from rocks!
except in very sheltered areas, or where it issubmerged and beyond the effect
of rough water. It is, however, capable of covering flat or sloping rocks with
a dense mossy growth; and of carpeting the intervening sand-spaces so that
they completely resist normal wave-action. In its young state the plant
is probably attached to rock, but as growth proceeds, sand collects, and the
abundant production of rhizoidal filaments helps to retain it. The growth
forms either pads which may measure a foot or so across, or vast sheets more
or less interrupted, but extending at times over a very wide area. When well-
grown, the Khodochorton sward is about 3cm. high; but in favoured spots
pads up to 6cm. have been met with. Though sometimes exposed to the full
light, especially on the lower part of the shore, Rhodochorton grows best with
partial shade. But even when exposed to light it is the ends of the branches
only that feel the full effect of sun and air, as the base of the plant is
covered with sand.

B,I.A, PROC., VOL. XXXI. I 15

15 66 Proceedings of the Royal Irish Academy.

Of the other species entering into the association Polysiphonia jibrata,
Ceramium strictum, C. ciliatwm form conspicuous patches in spring and summer,
their tufts of rhizoids growing down into the sward, and attaching themselves
to the sand-grains. @. ciliatuwm is found more or less all the year round, and
is of a shorter and denser habit than when growing in pools. In spring the ©
association often assumes a bright green colour due to the presence of
Cladophora arcta, This species retains the sand well by means of hooked
branches and rhizoids which grow downwards from the main shoots. It occurs
not only within the Rhodochorton vegetation, but outside it, often forming on
its flanks large unmixed patches. A dwarf form of Sphacelaria cirrhosa is also
frequent, but, because of its small size, is apt to be overlooked. Though
a filamentous species, it is distinct from the others, being attached by a basal
disk, and not by rhizoids. In late summer, especially in the more sheltered
localities, Rhodochorton is much discoloured by the presence of cyanophyceous
epiphytes. Of these Calothrix confervicola is the most common, being at times
so abundant as to ereate large black patches. Aphanotheca pallida is also
frequent. On the margins, where the association joins the Corallina-
Cladostephus vegetation, many other algae appear, and it is probable that the
borders of the two communities are in a continual state of change.

Young plants of Ulva Lactuca are at times present in great quantity,
especially in spring, but this species is in no way a sand-binder, possessing
only a foliose thallus and a basal disk. In the same way we may dismiss
many other intruders, the Rhodochorton sward being, in fact, a general nursery
ground, the sporelings succeeding each other in regular sequence as the
seasons come round.

With regard to distribution, the present community is probably very
widely spread in the British Isles. hodochorton floridulum is one of the few
species that form extensive associations on the flat sandy shores of Sussex;
and it has been found growing in the same way in Dorset and Devon. Harvey
states that at Kilkee (Co, Clare) “it often carpets large spaces on the rocks” ;
and Ralfs writes in a similar strain as to the plant at Land’s End (in /itt.). It
is also abundant on the shores of Belfast Lough. With regard to the Survey
area, the association is found at Portlea on Clare Island (rocks giving the
necessary shelter), and on a small scale in several other bays, where protection
is afforded by a heavy growth of Fucus. On the mainland, where for the most
part no special protection is required, it is very widely spread, probably coming
next to that of the Fucaceae in the amount of area covered. According to
Harvey the plant is washed ashore in quantity durmg autumn; and the
hemispherical cushions are collected (under the name of “ figs”) for use as
manure (Phye. Brit.).

Clare Island Survey—Marine Algae. 15 67

Corallina-Cladostephus Community.

This vegetation is frequently very well developed on sandy shores where
low rocks are present (¢g., Old Head). It retains a certain amount of sand,
but is usually found on raised or sloping rocks where the quantities deposited
are small. The community clearly forms a connecting link between the sand-
and rock-formations; but as both the species composing it are distinctly
saxicolous, and do not form rhizoids, it is regarded as belonging to the latter,
and is dealt with on p. 58.

The Porphyra umbilicalis Community.

Though attached only by a basal disk, and clearly belonging to the rocky-
shore formation, P. umbilicalis var. laciniata is frequently found, fringing
the sides of half-buried rocks, on sandy beaches. Its growth in this habitat
is described on p. 57.

Vegetation of Sand-Pools.

A very interesting psammophilous flora occurs in pools amongst low rocks
on sandy shores. The plants are not small and filamentous, such as Rho-
dochorton or Vaucheria (pp. 65 and 64), but large and bushy; hence, though
partially embedded in sand, they are invariably fixed to underlying rock.
Polyides and Gracilaria may be taken as typical examples; but some six or
eight other species occur, all being sand-loving plants, and found as a rule in
the sub-littoral region. When, as is often the case, ordinary rock-pools are
absent, the constancy of this sand-pool vegetation is very manifest.

Algae which thrive under such conditions have, as would be expected,
much branched thalli of erect habit. The fronds are more or less terete, and
in many cases tough. But other forms occur, especially where the amount of
sand is not excessive. Sand-pools are found at Old Head, and between that
spot and Leckanvy; also to a certain extent near Mulranny. The typical
flora is as follows :—

Polyides rotundus, c. Gymnogongrus Griffithsiana, 7.
Ahnfeltia plicata, c. Gelidium crinale, r.

Gracilaria confervoides, c. Cladostephus spongiosus.
Polysiphonia elongata, c. Corallina officinalis.

P, atro-rubescens, c. Rhodochorton floridulum.

Furcellaria fastigiata.

The last three are not characteristic of this vegetation only ; but they are
exceedingly common if the sand-layer is not thick, and, as shown above,
they form part of the littoral flora of the shore in question. The species of

12

15 68 Proceedings of the Royal Irish Academy.

Gymnogongrus and Gelidium were, however, not found outside sand-pools.
Where the sides are steep, ordinary saxicolous species naturally occur;
but as a rule the sides are shelving and the pools shallow. When fresh
water exudes between the rocks, the Rhodophyceae are replaced by
Chlorophyceae—i.e., Chactomorpha aerea, Enteromorpha intestinalis, —
Cladophora sericea, C. rupestris, and Ulva Lactuca; Gracilaria, however,
usually remains, being able to withstand a considerable quantity of fresh
water.

Where the sand-layer is very thin a number of other species are found,
and being characteristic of sandy shores, the most usual amongst them are
listed below :—

Ulva Lactuca (very thick form). Porphyra umb. laciniata.
Enteromorpha Linza. Helminthora divaricata(on Polyides).
Monostroma Grevillei (epiphytic). xelidium spp.

Seytosiphon lomentarius. Chondrus crispus (broad form).
Punctaria latifolia. Gymnogongrus norvegicus (7).
Chordaria flagelliformis. Chylocladia kaliformis.

Eudesme virescens. Laurencia pinnatifida.

Leathesia difformis. L. hybrida.

Chorda filum, Polysiphonia nigrescens.

Cystoseira granulata. Spermothamnion Turneri (epiphytic).
Halidrys siliquosa. Dumontia filiformis.

Dictyota dichot. var. intricata. Lithophyllum incrustans.

'

(b) Sub-littoral Region.
Rhodochorton floridulum Association.

As before mentioned, this psammophilous species descends into the
sub-littoral region, covering large areas where the bottom is flat and very
sheltered, as in the inner part of Clew Bay. The association apparently
exists in certain spots as an unmixed growth ; but as arule it is more or less
interspersed amongst Lithothamnium or other algae (see p. 65).

Zostera Association.

The soft bottom of the inner part of Clew Bay is admirably suited to the
growth of Zostera, and in the muddy parts especially, extensive beds are
found. The characteristic algal epiphytes are also well-developed, being most
marked in spring and early summer.

Ostenfeld in his report on Zostera (08) points out that, as a general rule,

Clare Island Survey— Marine Algae. 15 69

the size of the plant is more dependent on the nature of the bottom than on
the depth in which it grows. He shows that the form with short, narrow
leaves is found on firm sand, and that the long, broad-leafed form is
characteristic of soft mud, rich in food substances. A slight difference
between the algal vegetation of the sand and mud Zostera was
observed in Clew Bay, but not with sufficient care to warrant comment,
except to note that the latter proved the most productive in the way of
algae.

In spring, masses of Ectocarpi occur, together with innumerable tufts of
Cladophora lanosa; whilst im summer and autumn species of Bangia and
Chantransia are more abundant. Ascocyclus orbicularis is almost always
present, being noted in quantity in spring, summer, and autumn. At
the margins of the Zostera-meadows, and in spots where largest ones exist
other plants, such as Halidrys, Laminaria saccharina, and Cystoseira
granulata, are met with; and the association then tends to approach that
which Ostenfeld has termed the “mixed Zostera vegetation ” (l.c., p. 33). Of
the larger epiphytes the following are usually frequent in their respective
seasons :—

Cladophora lanosa. Myriotricha densa.

Castagnea Zosterae. Scytosiphon lom. var. zostericola.
Punctaria tenuissima. Laurencia obtusa var. crucifera.
Desmotrichum undulatum. Polysiphonia violacea.
Ectocarpus confervoides. Ceramium strictum.

E. siliculosus. Giraudia sphacelarioides, 7.

E. sp. Leptonema fasciculatum, *.
Litosiphon pusillus. Mesogloia lanosa, 7.

Whilst among microscopic species may be mentioned :-—

Calothrix confervicola. Melobesia farinosa.
Chantransia virgatula. Rivularia atra.

C. Thuretii. Isactis plana, r.

Ascocyclus orbicularis. Erythrotrichia Bertholdi, 7.

Rhodophysema Georgii.

The Fruticulose Lithothamnium Association.

Probably no group of seaweeds is more generally recognized as forming
extensive colonies or associations than the Lithothamnia. Submerged beds,
often known as “coral-banks,” occur in the arctic, temperate and tropical
regions. In the latter. they are frequently exposed at low water, and play

15 70 Proceedings of the Royal Irish Academy.

an important part in the formation of coral reefs. But notwithstanding
the many references, both systematic and biological, to this type of
vegetation, it is not by any means easy to compare the Lithothamnium flora
of one country with that of another. This is owing to the deceptive nature
of morphological characters, and to the many erroneous determinations in
the past. Foslie has left reliable records for recent years, and the anatomical
classification elaborated by Dr. Lemoine promises more success for the
future.

Between the outer islands of Clew Bay areas of Lithothamniwm caleareum
“coral-banks”) are common. They are found on a soft but firm bottom,
consisting usually of stones and shells on sand, though occasionally Litho-
thamnium may be dredged where there is a thin layer of mud. The usual
depth in which the banks occur is 1-5 fathoms, and here and there the plants
may be gathered by hand during the lowest tides. The association is com-
posed of the following species :—

Lithothamnium calcareum, dom.
Lithophyllum fasciculatum, Jocally sub-dom.
L. incrustans.

L. incrustans var, subdichotomum, rare.
Lithothamnium norvegicum, rare.

In many places Z. calcarewm forms a pure growth extending over a con-
siderable area, but in others it is mixed with Z. fascicwlatum, and sometimes
all four species occur mixed together. A characteristic growth of epiphytes
accompanies the vegetation, of which Polysiphonia subulifera, Pterosiphonia
parasitica, Aglaozonia reptans, Spacelaria cirrhosa, Rhodochorton floridulum, and
Gelidium sp. are the most constant. Dictyota, Chylocladia kaliformas, and
Lauwrencia obtusa are also abundant in summer.

With trivial variations this is the type of fruticulose Lithothamnium
vegetation found throughout Clew Bay. It presents one remarkable floristic
feature, namely, the presence of Z. fasciculatum, a species which is only
known from the west of Ireland. Another interesting plant is Z. inerustans,
var. subdichotomum, an alga which was formerly regarded as L. dentatum, but
shown by Dr. Lemoine in the present report to be a detached and rolling
form of the common species, Z, inerustans.

Other Lithothamnium banks in Ireland and Great Britain.—It was of
interest to find that the Clew Bay association agreed exactly in its
composition with that which had been described for Roundstone. The latter
district is the original station for Z. fasciculatwm ; and Foslie, when working
out the European Lithothamnia, paid a special visit to the locality and

Clare Island Survey—Marine Algae. 15 71

published an account of his trip (99). He found Z. fasciculatum still
plentiful, as it was also in September, 1911. The dominance of ZL. calearewm
in both Roundstone and Clew Bay is normal for the British Isles.

The remarkable “coral beaches” at Mannin Bay and Ballyconneely Bay
(Co. Galway) are due to the presence of extensive Lithothamnium associations
in the neighbourhood. When driving from Clifden to Roundstone in
September, 1911, the former spot was examined; but time did not permit of
exploration by dredging. It was evident, however, that the material washed
up is Z. caleareum, and that the beach, a fairly wide one, is composed almost
entirely of broken particles of this species. The photographs on Plate IV,
kindly taken by Dr. G. H. Pethybridge, show two views of the beaches in
Mannin Bay. A few low rocks occur in part of the bay as shown in the
lower illustration, but elsewhere there are stretches of pure “coral sand.”
The greater part of the sand is composed of small particles (see Plate V,
fig. 1); but at high-water line and in certain other places coarser
pieces and knolls accumulate, with a certain quantity of broken shells.
Dr. Pethybridge informs me that at low-water mark the particles are
exceedingly fine and resemble ordinary sand ; but it is probable that they have
the same origin. he Lithothamnium fronds are completely bleached, and
the beach is thus dazzlingly white in the sun. ‘Though the coral sand is
carted for use as manure, fresh supplies are constantly washed up, so that it
is evident that the bank outside is extensive. A similar beach is said to exist
in Bantry Bay.!

In the British Isles LZ. calearewm is certainly the dominant fruticulose
species, beds being known from several localities (Studland and Falmouth in
the south of England, and Bute in Scotland), and under certain conditions it
is gvashed ashore in quantities. A fine bed in 14 fathoms was once dredged
by me off Fowey (Cornwall). Another species, Z. racemus, appears to exist as
an association at Falmouth, since it is washed ashore in plenty; but this is
the only station for the plant in England, and records of Lithothamnium banks
in England or France formed by species other than ZL. calcarewm require
verification,

Comparison with other countries.—L. caleareum is also frequent in France.
It is abundant in Normandy, and in Brittany as far south as Croisic. Lemoine
(11) states that it is known from Denmark, Portugal, Naples, Morocco, and
Algeria. In all these localities it probably occurs in associations similar to

1 Several other remarkable beaches occur in the west of Ireland. A shore consisting exclusively
of broken shells is found at Knockboy (Co. Galway), which, like the coral-sand beaches, is
exploited for manure (Johnson and Hensman, ’99); whilst Dog’s Bay, near Roundstone, is famous
for its beautiful sands, composed almost entirely (up to 90 per cent.) of Foraminifera,

15 72 Proceedings of the Royal Irish Academy.

these found in the British Isles. At Morlaix and Concarneau there is “coral
sand” or “Maerl,” and, as in Ireland, this is used for manure. Lemoine
(710) has also published a detailed account of the biology of the plant. She
notes that at Concarneau the bottom of the bay is practically covered with
L.. caleareum, and fragments of living fronds are continually cast up by the —
waves. Several “coral beaches” occur on the islands of the Glenan
Archipelago, but there, as at Mannin Bay, the fragments washed ashore are
mostly dead.

In the Arctic seas, Kjellmann writes of large areas, in 10 to 20 fathoms,
covered with Lithothamnia, of which LZ. glaciale and L. soriferwm are abundant.
At Mussel Bay in Spitzbergen, Z. glaciale is said to cover the bottom to an
extent of 4 to 5 square miles; whilst off the north of Norway and on the
coast of Iceland, Z. Ungeri is abundant. In the former country banks of
L. norvegicum also occur, The association is represented in Greenland by
L. Ungeri. In the south of Norway the floristic features are more in agree-
ment with those of Britain, and Z. calcarewm becomes prominent. An
association composed largely of this species has been described by Gran for
Kristianiafiord (793).

Reference must be made (though it is outside our usual circle of com-
parison) to Madame Weber van Bosse’s account of the Lithothamnia of the
“Siboga” Expedition (04). A very luxuriant vegetation exists in the shallows
and reefs of the Malay Archipelago, and several communities on different
types of ground are referred to. A description is given of a locality where
the Lithothamnium knolls are rolled backwards and forwards between the
islands by the tidal current, whilst in other parts of the same channel they are
heaped up in banks. Two photographs are reproduced of an extensive bank
of LZ. erubescens var. Haingsisiana, which Madame Weber describes as being
“covered as far as the eye can reach by the pretty, beautifully pink-coloured
knolls, which are heaped so close together, that while walking one crushes
them continually, making a peculiar noise as of broken china” (/.c., p. 5).

Geological Importance—In localities where masses of Lithothamnium
accumulate on the sea-bottom, these algae play an important part in rock-
formation, and masses of limestone containing well-preserved Lithothamnia
occur in various geological strata. Structureless limestone also may be
derived from the same source, for Walther, working at Naples, showed that
the structure of recent Lithothamnium nodules is gradually obliterated by the
action of percolating water. The literature on the subject is scattered; but
Seward’s paper (94) gives a general summary with a full bibliography ;
and a brief but up-to-date account has just been published by Lemoine
(ale)

Clare Islund Survey—Marine Algae. 15 73

The Pebble-attached Association of Qumet Bays.

This association represents a definite type of sub-littoral vegetation, which
is found on a soft bottom strewn with stones and pebbles. A very large
number of species go to form it, and they are for the most part characterized
by finely divided bushy fronds, though heavier and less bushy plants are found
on the larger stones and on the occasional pieces of rock. In some localities
almost every stone down to the smallest pebble bears a tuft of one or more
algae. The latter consist of members of the Green, Brown, and Red groups;
and, though they vary considerably in different localities, the mixture of
colour is a marked feature and suggests comparison with Kjellmann’s “ Bunte
Formation.” But both the constituents of that association, and the depth at
which it oceurs, are different from those here described. The present vegeta-
tion corresponds rather to Borgesen’s Stictyosiphon association and to Boye’s
Dictyosiphon-Spermatochnus-Corallina formation, though Dictyosiphon is
not always present. The species are annual or short-lived, which in part
accounts for the varied aspect presented during the season.

The association extends from just above low-water mark down into 3 or
4 fathoms. Its shallower regions may be studied in detail by wading at spring
tides, when the bushy fronds of Polysiphonia, Cladophora, Spermatochnus,
Dictyosiphon, ete., may be examined im situ. Dredging in deeper water
shows a very similar type of growth, though some species disappear and others
become more abundant. The colour of the red species improves with increased
depth. The association, which reaches its maximum development in May, is
well seen in many of the inner parts of Clew Bay, and has been studied specially
on the west side of Annagh Island, and, in a slightly modified form, in
Bellacragher Bay. In brackish localities an increase of Chlorophyceae is
apparent.

«\s it oceurs in Clew Bay the principal species are as follows :—

(2) In spring —

Enteromorpha clathrata. Lomentaria clavellosa.
Cladophora Rudolphiana. Nitophyllum punctatum,
Striaria attenuata. Polysiphonia urceolata.
Stictyosiphon subarticulatus. P. elongata.
Dictyotosiphon foeniculacea. P. nigrescens.
Ectocarpus siliculosus. P. atro-rubescens.
Pylaiella littoralis. Ceramium rubrum.
Cystoclonium purpurascens. Griffithsia corallina.

Delesseria hypoglossum.

R.I.A. PROC., VOL. XXXL, K 15

15 74 Proceedings of the Royal Irish Academy.

(6) In summer Striaria, Dictyosiphun, Delesseria, and Griffithsia largely
disappear, but the other species remain; and in addition we find :—

Cladophora rectangularis. Polysiphonia subulifera.
fo)
Spermatochnus paradoxus. P. violacea.
Castagnea virescens (shallow P. fibrillosa.
water). Bronegniartella byssoides.
fo)
Dictyota dichotoma. Ceramium spp.

As autumn advances one species after another becomes detached and
disappears, though Dictyosiphon, Ectocarpus, and Polysiphonia nigrescens
remain. <A day’s dredging in February showed that most of the spring species
had started growth; but the vegetation on the whole was very scanty com-
pared with that of spring and summer. It should be noted that a few of the
species above listed may be largely epiphytic on the others, and that in summer
the upper part of the association is very poor.

Very many other algae, both littoral and sub-littoral, enter into this
vegetation. Several of these are characteristic of other associations,
e.g. Gracilaria, Polyides, and Rhodochorton floridulum. Callithamnia likewise
are very plentiful, and the encrusting alga association is often found as an
undergrowth.

Encrusting Alga Association (sheltered),

In spite of unwillingness to change names, a new term is introduced here.
The Lithoderma formation described by Kjellmann has been recorded by
other observers; but the difficulty of determining encrusting species makes it
often impossible to be certain if Lithoderma is really dominant, or whether
other algae of similar appearance are not equally common. With regard
to Clew Bay, it is not certain that Lithoderma is even present; though,
judging from sterile specimens, it is probably abundant. A wider and more
general term has therefore been selected.

The association is found on a soft bottom overlaid with shells and flat
stones, which, instead of supporting a bushy vegetation like the last-named,
are practically covered with encrusting algae. Of these, the first four in the
following list are conspicuous and easy to recognize; the remainder are
probably common, though not so readily detected :—

Ralfsia verrucosa. Petroderma maculiforme, 7.
Aglaozonia reptans. Lithothamnium hapalidioides, /.
Cruoriella Duby. L. Lenormandi, var. sublaeyis, /.
Lithophyllum inerustans. Melobesia zonalis, 7.

Ralfsia clavata, 7. Peyssonuelia sp., 7’.

Lithoderma fastiscens ?, /-

Clare Island Survey—Marine Algque. ita) 77s)

The above vegetation characterizes much of the inner part of Clew Bay.
At times it forms an undergrowth to the pebble-attached association; but as
a rule it appears to exist as a separate community, except for a certain
admixture of Rhodochorton floridulum and Sphacelaria cirrhosa, - In winter
Cordylecladia erecta is also plentiful. The February visit was most useful in
obtaining fruiting material, but even then many of the Brown encrusting
plants proved sterile. A January visit would perhaps have been more
productive. Outside the islands the species mentioned mostly disappear, the
rocks and stones being clothed with plants which belong rather to the exposed
Lithothamnium association (e.g., LZ. laevigatum and L. compactum).

It is diffieult to compare the Clew Bay growth with that of other localities,
especially with regard to the relative abundance of the different algae, but it
appears to be richer in species than any of the Lithoderma associations
hitherto described (Kjellmann, ‘78, Borgesen, ’05, Kylin, ’07). In England
much dredging has been done by various workers, and Plymouth Sound,
which is as sheltered as Clew Bay, has been well explored. The records,
however, are poor, and there is no means of satisfactorily comparing the
vegetation. It is interesting to note that Harvey dredged Peyssonnelia
abundantly in Birturbuy Bay, whereas in Clew Bay Cruoriella Dubyi is by
far the most frequent species.

Channel Vegetation.

On each visit a record was kept of the species collected in the shallow
channels at Achill Sound. Though far from exhaustive, the lists serve to
indicate the most conspicuous algae during the different seasons of the year,
and since no record of the seasonal development of this type of vegetation
exists, they appear to be worthy of publication. IMKuckuck (97) briefly
describes the seasonal variation in Heligoland; but his paper deals with an
open shore. It will be noted that the flora of the channels resembles that
of the pebble-attached association of quiet bays—a fact which is not surprising,
since the general surroundings are similar, and in both caxes the plants are
attached to stones on sand. In the channels, however, there is rapid current,
whereas in the bays the water is slack. ‘lhe accompanying table comprises
lists of the four seasons of the year :—

K 2

Rinnjes)
/ ssndstaa snapuory
“TVLULILT ae “quan Badydto,T

“dds wisunryurtt,)

“RYBLNURAS wltasoj}s..g
ssnisorsuods snydaysope |

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“STAT Vjlarep Aq

njnoruaoF TOYdIsoAqor(y

“wnqpisnd uoydisoz y

warnydropnyy waoydope[g

“Wt SURUYSOLUT BYCIOWLOADPUST
ynosntem vAqsurry
“dds Xiuyyopey
“dds wodansouna(y »

sepyed woayjounydy

*SOPLOALOFUOD BIIU|TOUL
pura StAX qdopouy
RSOT[LUINUL BURST,

ssndsti) snapuoyy

“RUMOZOLOIP BIOAION(T
“RIRTNUBAT VELA80}SAL,
*SIUMIOJ LIAN} VISOqwarTy
*SUOODSAITA BOUBVLISR()
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“syeroyy eppopsg
‘snso[noTIs sudavo03 957
“susoy[Ng sn920a0.1ads \r
“snmimjuaMo, uoydisoyArg

sunytsnd uoydrsoyrry

-nuvtudjopuyy “91
“ayeyyep vydromo.ra ug

upnosnteu viqsucry

a a “y

“Hi SUBOSOITA BAUSTISLG,
‘fe ‘snxoprand snuooywinsedg
‘snsorsuods suydaisoprrp
*SUSO[NULS “OL

*smsO|NOITIS sndavd04 997
“suso[njsy AV

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‘RUT[[B.L0d VISYJUFLIY)

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‘quoMlasuBIe o1yVUIo4SAs UT 4ST] TeIOUES oYy ‘4say paov[d osvo Ye UT orv soloeds quvpunqe pur snonoidsuos 4sout aug,

‘STUNNVEQ TIHHOW

*SHPUTIYO.L SOPLA [Og]
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TUTTE WIN TUR.)

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suntmodsApod +9

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uwfooon viol dis<pOT

MPLIQAU TT,
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umssosod.aty *q
NOUS ULS NLLOSSETO(T
“UNOUTOIOD CAN TUINDO [cL
YBN “Ty

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*SOPLOALOFILOD VEER LOW)

osidind watwopooys.D,

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LSE) SUIPUOY OD

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t | ‘

MULOJOYOIP WOAIOLCT

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ates

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WOONOLA “TL

15 78 Proceedings of the Royal Trish Academy.

Il1.— The Salt-Marsh Formation.

The conditions obtaining on the salt-marsh resemble those of the sand-,
rather than the rock-formation ; but they differ im several important
particulars. In the first place, the salt-marsh formation is situated above
the level of high-water at ordinary neap-tides; and in the second, the
substratum contains more or less humus consisting of mud or alluvial
deposits, and in the Clare Island area peat is frequent. By reason of its
bathymetric position, the marsh is only flooded at spring-tides, and hence the
algal vegetation instead of being moistened daily by the tide is hable to
desiccation on the one hand, and to prolonged soakings of fresh-water in the
form of rain on the other. Further, there is continual competition with
flowering-plants. As a result of the edaphic conditions, we find that the
algae are not attached by a basal disk as in saxicolous plants, nor are they
completely buried as is the case with many psammophilous species ; but they
either lie loosely on the substratum or are apparently rooted in the ground,
after the manner of flowering-plants. The lack of fully saline conditions
shows itself in the predominance of brackish species, green and blue-green
algae being abundant. The salt-marsh often passes by easy transitions to
sandy shores, mud-flats, or to the banks of rivers.

From the floristic standpoint, the algae of the salt-marsh are generally
uninteresting; but among the Fucaceae remarkable forms occur, several of
which have long taxed the energies of systematists; but with mereased
attention to ecological considerations their elucidation appears more hopeful.
The Florideae are represented (amongst macroscopic forms at all events) by
two species only, viz., Catenella Opuntia and Bostrychia scorpioides.
Cyanophyceae are abundant ; and as far as filamentous genera are concerned,
they fall into fairly well-marked species; the chroococcaceous series have not
been specially examined. Phoeophyceae are often conspicucus, and figure
largely as regards bulk, being represented almost entirely by members of the
Fucaceae. The latter vary widely in different localities, and are often of
considerable interest. The Chlorophyceae are well represented ; and, as is usual
under brackish conditions, they are often difficult to determine. Rhizoclonium,
Chaetomorpha, and the smaller species of Enteromorpha are abundant, and
show much variation in form. These green algae are doubtless largely
modified by the peculiar conditions of the salt-marsh—a result which is not
surprising, when one considers the profound modifications amongst the less
plastic group of the Fucaceae. The variation displayed by Hnteromonpha
intestinalis on flat shores when fresh-water is present is most extraordinary.
With regard to edaphic conditions, a certain amount of variety will be found

Clare Island Survey— Marine Algae. 15 79

on the same marsh. In the Clew Bay district the substratum consists of
peat, or of a loamy soil derived from the boulder-clay ; patches of mud also
occur. With the exception of the dwarf Fucus, most of the algae associations
described below occur on each of these types of ground. The mud-flora is
the most distinct, and where soft it differs markedly ; but otherwise the
nature of the substratum does not appear to exert a great influence in this
particular district. With a detailed study certain differences would doubtless
be detected. The vegetation of the mud-patches of the salt-marsh approaches
on the one hand that of the mud-banks of the tidal streams, and on the other
that of the mud-flats below high-water mark. Several of the salt-marsh
species lie on the ground, or on other vegetation ; but Bostrychia is epiphytic
on Statice, Atriplex, and similar plants; consequently the presence of these
algae is in part dependent on the character of the phanerogamic vegetation.
But the converse is also true. Hull (09, p. 102) and Baker (12) have
shown the importance of the Rhizoclonium covering in connexion with the
germination of Salicornia seeds; and the same matted growths doubtless
protect seedlings and young plants from excessive insolation.

The Clew Bay salt-marshes agree well as to their flora with the general
description given above. The four types of vegetation distinguished were :—

1. Rhizoclonium association.

2. Fucus vesiculosus va7. muscoides association.
5. Bostrychia-Catenella vegetation.

4. Vegetation of vertical banks.

The areas specially explored were those on or near Annagh Island, and
below the hotel at Mulranny. Small patchesof ground supplying similar
vegetation were also examined in Bellacragher Bay and at Leenane. )

Rhizoclonium Association.

Rhizoclonium viparium is the dominant species in the felt-like sheets of
green algae which are often so conspicuous on the salt-marsh. These sheets
are found typically on bare soil (sand, loam, or peat), and at Mulranny are
continuous with the Rhizoclonium association, which occurs on the sand from
half-tide level and above. On the marsh, Rhizoclonium is also abundant in
shallow pools, and it invades (especially in warm, damp weather of spring)
areas colonized by phanerogams. When Rhizoclonium alone is present, the
growth is light-green; but when, as is often the case, Enteromorpha occurs in
addition, the colour is deeper, and does not turn pale to the same extent on
drying. Brown and black streaks in the felt indicate the presence of

15 80 Proceedings of the Royal Trish Academy.

Cyanophyceae; in Clew Bay usually Lyngbya confervoides and L. majuscula
respectively.

The Rhizoclonium association is more general in some localities than in
others, and varies considerably according to the time of the year. Where
bare soil is scarce the growth is scanty; where plentiful the felt is, except’
in spots where strong tidal action obtains, usually abundant. In spring and
early summer Rhizoclonium, Percursaria, and Euteromorpha spp. are very
luxuriant; later in the season Cyanophyceae develop, and the felt-like
growth, as a whole, is not so extensive. The following species compose the

co}

association in its wide sense :—

Rhizoclonium riparium, dom. Lyngbya majuscula, /.ad.
Enteromorpha torta, 7. L. confervoides, /.ab.

E. Ralfsii, / Cladophora fracta \

Percursaria percursa, a. Chaetomorpha linum | 17 shallow
ie ; : ‘ depressions.
Pylaiella litoralis, f. Capsosiphon aureolus

Lyngbya aestuarii /.ad.

With certain weather-conditions the Rhizoclonium-felt is partially
destroyed. After a high tide, for instance, with a strong 8.W. wind, muchi
of the growth at Mulranny is rolled up into rope-like masses; whilst sheets
2 or 3 yards square have been observed deposited on the Glyceria maritima
sward, having been lifted bodily out of the shallow depression in which they
orew.

Fucus vesiculosus va7. muscoides Association.

The carpet formed by this remarkable dwarf Fucus occurs above the
uppermost Pelvetia (ie. slightly above the mean high-tide level), and is thus
only tlooded during spring-tides, It is characteristic of peaty shores. Where
the shore slopes, the Fucus vegetation forms a distinct narrow band; but
where it is flat and salt-marsh conditions obtain, it is much more extensive,
and may pervade a large area of the marsh. As a band, it is widely
distributed in our area, being frequent in Achill Sound and Bellacragher Bay.
On the salt-marsh it is usually found on the best-drained areas.

The association forms a dense mossy turf in which Glyceria maritima 1s
usually abundant, and scattered plants of Statice maritima, Glaux maritima,
and Salicornia maritima also occur. Occasionally, however, small patches of
pure Fucus inay be noted. The “turf” is composed of fastigiately branched
plants which are densely crowded together, with more than half their total
length (2-3 inches) buried in the peat. The growth is very erect; but the
upright shoots are often found to arise from a more or less creeping stem,

Clare Island Survey—Marine Algae. 15 81

On firm, well-drained areas, the branches are cylindrical or nearly so, and
the whole very short and compact. On wetter areas the shoots are flatter
and the growth lax, but it is frequently checked by competition with
Rhizoclonium and Enteromorpha. In other cases, the phanerogamic vegeta-
tion in damp soil becomes rank and tall, and then Fucus, when present, tends
to assume the form of var. baltzcus (e.g., at Leenane). Fruiting specimens are
always rare.

The plants apparently live for many years, and increase entirely by
vegetative methods, proliferations being often abundantly produced from all
parts of the shoots. During the spring-tides a certain amount of sand and ©
silt is doubtless deposited, and new shoots continue to arise, whilst the basal
portions gradually die away. It is difficult to trace the basal end of the
shoot for more than 1 or 14 inches below the surface of the soil. The fact
that the plants are largely embedded enables them to avoid desiccation
even in the hottest weather during the nine or ten days which elapse
between each spring-tide. The same fact also meets the difficulty with regard
to the presence at so high a level of the mid-littoral species /. vesiculosus.
In the case of var. volubilis, no one can doubt that the large, vesicled
forms (vide Baker, 12) are derived from /. vesiculosus; yet under the
peculiar conditions of the salt-marsh they occur well above the limit
recognized as normal for that species. Thus the high level at which
var. muscoides is found is no objection to its being a variety of the same
species. ;

In certain localities, the presence of scattered plants of Statice maritima
is a charaeteristic feature. The mossy carpet of Fucus appears to modify
the growth of Statice, so that it forms small rosette-like plants instead
of the familiar clumps. The leaf-scars may be traced for some distance
below the ground-level, and the plants are evidently of considerable age.
In May and June the pink blossoms of Statice against the background
of Fucus produce a striking effect. The photograph on Plate VI
was kindly taken by Mr. G. Massee from a tuft brought home in May,
GL -

As far as has been ascertained, no vegetation of this nature has been
previously described; certainly not from an ecological standpoint. It is
plentiful at Roundstone, and is doubtless widespread in the west of Ireland.
The plant is characteristic of firm peaty soil, and is probably to be found in
our islands wherever peat runs down on a flat shore! On the muddy ground
near the mouth of the Bunowen, where there is a covering of Boulder-clay,
the var. muscoides vegetation is completely absent.

1 Since writing the above I have seen similar associations in the west of Scotland (Loch Linnhe).
R.1,A, PROC., VOL, XXXI. L 15

15 82 Proceedings of the Royal Irish Academy.

Bostrychia-Catenella Vegetation.

The usual growth of Bostrychia scorpioides and Catenella Opuntia as
epiphytes on flowering plants occurs in our area, though not in such profusion
as in some localities.

The former is very plentiful, and is especially found as a dense growth
under the leaf-rosettes of Statice maritima. At Mulranny the older plants
seldom lack this Bostrychia-pad. On woody plants, such as Atriplex and
Limonium (specially when growing at the sides of streams and channels), it
hangs loosely from the lower branches. Catenella is, on the whole, scarce on
the marsh, but locally it is abundant.

It is worth noting that both these plants occur near high-water mark on
the banks of the Newport River, and in parts of the upper reaches of Clew
Bay. They grow here on bare rocks and boulders, showing that brackish-
water and long exposure to the air are important factors. A certain amount
of shade is usually provided by Pelvetia.

Vegetation of Vertical Banks (peat or loam).

The vertical peat-banks which occur on the Annagh Island and Mulranny
salt-narshes possess a characteristic flora showing well-marked zonation. The
same vegetation is even better developed on the peat-banks bordering on the
shores of Achill Sound. On the salt-marsh, the banks are seldom more than
3 feet in height, and are much broken up; but at Achill they are higher, and
often extend for some distance along the shore. The same type of vegetation,
showing the same sequence, is also found on the loam-banks of the Bunowen,
but with certain characteristic differences, due to the presence of fresh water
(see p. 85). The fresh-water channels of the salt-marsh are also distinet, their
banks being muddy and possessing a different flora.

Ina general way the vegetation of the peat-banks is disposed in four
bands, which invariably occur in this sequence from above downwards :—

1. Phoeococecus adnatus.

2. Rivularia nitida.

3. Vaucheria coronata and Calothrix fasciculata.

4, Rhizoclonium riparium (with scattered plants of F. spiralis, var. nana).

The three lowest bands are usually each about 1 foot deep; but the
Phoeococcus band is narrow, and is not infrequently absent. Practically all
the tidal banks are clothed with this vegetation; but at times (especially
where moisture is retained ?) a growth of F. vesiculosus var. muscoides intrudes
from the grass above. The essential conditions appear to be regular flooding
with salt-water, coupled with complete shelter.

Clare Island Survey—Marine Algae. 15 83

Vaucheria and Calothrix, which form a velvet-like growth of light and
dark green respectively, occur often in equal proportions; but at times
Vaucheria is dominant. Rhizoclonium forms a dense felt, through which
emerge numerous plants of F. spiralis var. nana. At Achill Sound (as on
the banks of the Bunowen)a band of Rivularia Biasolettiana sometimes occurs
above Phoeococeus. An average reading would be as follows :—

Feet. Inches,

Rivularia Biasolettiana, . k 3 : F 0 il
Phoeococcus adnatus, 0 2-6
Rivularia nitida, ; : ‘ 5 : 5 iL 0
Vaucheria and Calothrix, . 1-2 0
Rhizoclonium and F. spiralis var. nana, 1-8 -

When a vegetation-zone exists below the Rhizoclonium band, it consists of
Enteromorpha intestinalis and F. spiralis, the latter being larger and stronger
than when it occurs at a higher level.

A large number of readings were taken at Mulranny, Annagh Island, and
Achill, and, though the amount and luxuriance of the different species differed:
considerably, the general zonation was invariably the same. Neither was
any difference noticeable on the banks composed of loam, except for the fact
that 7. spiralis was practically absent, the soil being apparently too soft for it
to obtain a foot-hold.

The period of submersion can only be ascertained by observations on the
spot. At Achill Sound, the neap-tides reach the level of /. spiralis, though
the salt water soaks up through the peat to Vaucheria and Rivularia. With
spring-tides the whole vegetation is flooded, and one may see the top zone of
Phoeococcus covered with two feet of water. Slight variations due to local
topography are of course frequent.

Comparing the above vegetation with that found on the banks of the
Bunowen, one notes that / spiralis replaces F. ceranoides, and that Hntero-
morpha minima is absent. The upper zones are the same in both—a fact which
is easily understood when the source of moisture is considered. A similar
series of plant associations doubtless occurs in other districts where sheltered
banks exist. At Mersea Island (Essex) bands of Cyanophyceae in regular
sequence have been noted, but on a much smaller scale than at Achill.
The firm peat of the west of Ireland is doubtless more suitable for permanent
growth than the soft banks of the Essex coast.

iv. River-Mouths and Fresh-water Streams.

The method which has been adopted for describing the flora of previous
sections cannot easily be followed in dealing with the vegetation occurring at
L 2

15 84 Proceedings of the Royal Irish Academy.

mouths of rivers. Though certain species are found to be constant, it is
difficult to obtain generalizations as to the position and sequence of the plant-
societies ; and a detailed account is more apt to be merely descriptive of a
particular locality. Opportunities for comparison are fewer, not only owing
to the small number of streams available, but on account of the different
physical conditions afforded by each. In Clew Bay, for instance, there are
but three rivers, the floras of which are very different. The Newport river has
banks strewn with rocks and stones on which Fucus develops; whilst the
banks of the Bunowen are loamy and possess a vegetation of Chlorophyceae
and Cyanophyceae. The Westport river is again different. There is also a
stream at Belclare which issues as a waterfall amongst rocks in the midst of a
luxuriant growth of Fucus ceranoides, and then disperses itself on a muddy
shore. In contrast to the above the hill-side streams that descend into
Bellacragher Bay and Achill Sound are fairly constant. in their flora.
For the above reasons it is more satisfactory to treat the vegetation of each
stream as such, and not to attempt a general account.

The Newport River.

This river is tidal for about 3 miles, and has fairly wide banks which
support two well-marked plant-communities, namely, an Enteromorpha
association and a Fucaceae association of brackish type. The conditions with
regard to salinity in such a river are unusually complicated. During heavy
rains, the banks may be flooded with fresh water brought down by the stream
to a much higher level than usual, and the algae composing the vegetation
must be able to endure, not only regular change due to tide, but also
prolonged submersion in fresh water.

(1) Enteromorpha Association.—This consists chiefly of JH. intestinalis,
E. prolifera, and #. clathrata, together with the numerous intermediate forms
characteristic of brackish waters. The growth is most irregular and perplex-
ing, and, as the Ulva investigations had shown, any attempt to name all the
forms occuring is at present hopeless. Time, therefore, was not wasted on
the genus.

(2) Fucaceae Association—Fucus was more interesting, the most extensive
erowth of /. ceranoides seen in the district occurring here. Starting from the
mouth of the river, there is a vegetation composed of Pelvetia, F. spiralis,
Ascophyllum, and F. vesiculosus. On walking towards Newport F. ceranoides
soon appears. This takes the place of F& spiralis, and lower part of the
Pelvetia belt. The latter, however, remains a little longer, especially on
boulders. #. ceranoides meanwhile increases, and gradually usurps the

Clare Island Survey— Marine Algae. 15 85

position held by Ascophyllum and F. vesiculosus, till, at + mile below
Newport, the association consists entirely of this species. Ascophyllum is
the last to disappear, persisting on boulders, especially in the lower part.
At Newport Bridge, 7. ceranoides forms a very fine growth, of which some
50 or 60 yards are exposed at low-water; as far as could be seen, it extends
right across the river. The association continues above the railway bridge
(the exact distance was not noted), where it is covered with perfectly fresh
water for many hours at a time. The upper part of the F. ceranoides belt
(at the Pelvetia level) consists of very short plants, in some cases barely an
inch high. Amongst it exists a certain amount of Catenella aud Bostrychia,
especially on slabs of rock. At a lower level the growth is large and
vigorous, and shows as usual great blistering of the thallus.

Bunowen.

Rising in the mountains near Croaghpatrick, and flowing through the
town of Louisburgh, the Bunowen cuts a sinuous course through the boulder-
clay on the plain, and immerges on the sandy shore west of Old Head. The
banks for the last mile are loamy and steep, until about } mile from the shore,
where they tend to become flatter as the river widens out. In wet weather
the volume of water is largely increased; the deep brown stream being
perfectly fresh when the tide is on the ebb. Many algae therefore, which
are normally left dry and first moistened by the returning tide, are not
infrequently immersed for hours in fresh water.

Vertical Bunks.—Beginning about } mile from the shore, we find at low-
water banks 3-5 feet high. Where current is felt, there is constant erosion,
and algae are practically absent: but in bays and bends a short vege-
tation exists, showing definite zonation. The sequence of the bands is
usually as follows, beginning at, or slightly above, the average high-water
level :—

Phoeococcus adnatus, : : : : . 6 2-3 ins. high.
Rivularia nitida, : : 5 ; é F : 1-14 foot ,,
Rhizoclonium riparium and Enteromorpha intestinalis var. 1 is: ie
Do. with Pylaiella litoralis (F. ceranoides scattered), 1 a fi

This vegetation extends more or less interruptedly for some distance till

a bend and widening of the stream is reached. Several creeks and back-
waters then appear, as well as flat, muddy slopes; and the extra shelter is
favourable for Vaucheria, which now becomes prominent. The average

15 86 Proceedings of the Royal Irish Academy.

sequence and depth of the bands on loamy or peaty banks about 4 feet high
is as under :—

Rivularia Biasolettiana (varely present), . F 1 inch.
Phoeococcus adnatus (not always present), : 2 inches.
Rivularia nitida, : : ] é : ; 9 ins.—1 foot.
Rhizoclonium and Enteromorpha, . , 2 2 feet.
Vaucheria coronata and E. intestinalis var., 3 1 foot.

In narrow creaks (which possess little light), Vawcheria coronata clothes
the entire surface of the banks, growing very luxuriantly up to extreme high-
water level. It forms here a loose furry growth (due to copious branching)
instead of the short velvet pile found in open places. Where the banks are
flat the growth spreads out horizontally, and the clear zonation is lost.
Phoeococcus and fivularia nitida usually disappear (cf. Bellacragher Bay,
p. 89), Rhizoclonium, Percursaria, and Enteromorpha taking their place, and
running in amongst Statice maritima, Glaux maritima, and Glyceria maritima,
so that the whole forms a miniature salt-marsh.

With regard to seasonal development and other details, R. itida,
Rhizoclonium, Enteromorpha, Vaucheria coronata are found at all seasons.
R. Biasolettiana is perhaps mostly a winter and spring species, it being noted in
quantity in May only. Phoeococcus forms, on the loamy banks of the
3unowen, a narrow band (cf. Achill, p. 83), and is in places entirely absent.
It reaches its maximum development in late summer and autumn, and occurs
above the average high-water mark. 2. nitida is likewise most conspicuous
in autumn; in favoured spots the greenish-black band, a foot deep, stretches
for many yards; in others it is intermittent, due possibly to the crumbling
away of the soil. The Rhizoclonium-Enteromorpha association is practically
uninterrupted, andis more luxuriant in spring, forming a bright apple-green
belt ; in summer it becomes bleached, and the Knteromorpha constituents are
dominant. Monostroma sp. (= JZ. crepidinum? see p. 107), noted in spring,
summer, and autumn, is scattered irregularly throughout this growth; but it
is never copious, and is apt to be overlooked. The lower part of the
association, which consists of narrow varieties of Hnteromorpha intestinalis,
merges into the Vaucheria coronata zone. The last-named often stretches a
long distance as a pure growth, forming a dark-green, very short, velvet pile.
It fruits abundantly, no difficulty being found during any visit in obtaining
the characteristic oogonia. If stones exist, /’ ceranoides may occur near low-
water level; but its growth is poor.

Flat Sloping Banks.—Close to the mouth, the vertical banks give place
first to firm mud and then to stony banks, with more or less sand, The

Clare Island Survey—Marine Algae. 15 87

former, as already indicated, is clothed with V. corenata, Rhizoclonium, and
Enteromorpha ; but many other algae occur, all the species mentioned for the
salt-marsh Rhizoclonium association (p. 79) being noted. Beautiful dark
patches of Capsosiphon were found in May on stones at half-tide level.
V. coronata disappears as one nears the sea; but another species with
filaments 2-3 inches long, only found sterile, becomes frequent in pools.
A fine Microcoleus association (see p. 63) is also present in the sand and
sandy mud found between the loamy ground and the stone-covered banks.

With the appearance of stones and boulders the Fucaceae vegetation
sets in. At first it consists of pure J ceranoides, but F. vesiculosus soon
follows, appearing first on the uppermost boulders (where it would obviously
receive the least amount of fresh water), and gradually increasing till at the
embouchure the two species occur in equal proportions. A second plant-
association is represented on the stones, namely—Lnteromorpha intestinalis.
This exists as a pure, luxuriant growth in the bed of the stream. In a
modified form, it ascends the banks under the Fucus-covering, and in spots
forms a green band above it.

F. ceranoides accompanies the river on to the flat sandy beach, and is found
on the rocks to the east of the main stream, where it is doubtless under the
influence of the fresh water. The association of Porphyra, which occurs below
(p. 58), must also receive a certain amount of brackish water.

Bellacragher Bay Streams.

The streams which descend from the high hills and peat bogs of Curraun
Achill seldom if ever dry up, though the amount of water brought down
varies greatly. A well-marked vegetation is present at the outlets, which is quite
distinct from that of ordinary streams, and which is probably characteristic
of small mountain torrents. It consists of I’. ceranoides, and a species of
Monostroma (No. 91, see p. 107), and does not appear to have been previously
deseribed. As a rule there is a large deltoid mass of F. ceranoides, with a
smaller patch of Monostroma in the upper part; but the physical nature of
the shore modifies the horizontal distribution of the algae, so the deltoid
form is often more or less lost. :

F. ceranoides shows first on the stones in the stream near the ordinary
high-water line; and on descending the shore it spreads out laterally over
the flanks, and continues to low-water mark. Though a large portion remains
immersed all day in fresh-water, it is completely covered by each tide. The
plants fruit abundantly, but do not attain to so large a size as those found on
river-banks (¢.g. Bunowen and Newport).

15 88 Proceedings of the Royal Irish Academy.

The Monostroma vegetation is at its best in spring (Apriland May). It
then occurs in deltoid patches, reaching from above F. ceranoides to about
half-tide level. It covers the rocks and stones in the stream with a dense
covering ; and also spreads out on either side, growing chiefly on the Fucus.
The plants in the streams remain submerged; but those outside are exposed
at low-water, and in fine weather dry up rapidly, appearing as a brittle skin,
which crackles in the hand. As summer advances, the flank-growth
disappears; but in the streams themselves Monostroma was found in plenty

during each visit.

v. Vegetation of Brackish Bays.

The vegetation of inlets surrounded by mountains from which streams
descend possesses several distinctive features, and must be recognized as afford-
ing a definite vegetation-type. Certain species of diatoms are abundant, also
Cyanophyceae ; whilst the complete absence of several of the larger algae, and
the prevalence of others, are also noticeable.

Other factors, besides the addition of fresh water, have, however, to be
considered. Being more or less land-locked, the tide is slight, and the condi-
tions exceedingly tranquil : consequently the aeration of the water is probably
very poor. Mineral salts moreover are brought down by the streams, and in
our area peaty acids and other compounds from the peat-bogs are doubtless
plentiful, the streams being deep brown in times of much rain.

Bellacragher Bay was selected as a spot for systematic investigation. It
is land-locked, and, except for a few months in summer, receives a large
amount of fresh water. Samples of water taken in August showed almost
normal salinity, but this was after the dry summer of 1911. This inlet is,
therefore, not an extreme case; but the features shown may be useful for this
very reason. Bays of much féebler salinity doubtless occur in Ireland, as
they do abundantly in the west of Scotland.

The following associations are represented in Bellacragher Bay :—

Hildenbrandtia-Verrucaria.—Very well marked on stones and pebbles
from half-tide downwards, ascending higher in damp places.

Fucaceae.—All five species present. Fronds of Ff serratus narrow. F. cera-
noides forming delta-like patches at the bottoms of streams, but not
general in any part of the bay.

Lichina.—Very feebly developed. LZ. conjinis most frequent.

Laurencia-Gigartina.—Poor. Isolated patches in sub-littoral region
common.

Laminaria.—Sub-association of L. saccharina on big stones and blocks of
rock frequent. Plants usually long, but not wide, 10 to 12 ft. by 1 ft.

Clare Island Survey— Marine Algae. 15 89

Encrusting Algae—Lithothamnium polymorphum belt well developed,
usually with Corallina officinalis.

Pebble-attached association.—Extensive and well developed, but poor in
species. Examined by wading at extreme low-water,

Zostera.— Local.

Special features—Two societies not referred to elsewhere are very
prominent in the littoral region. (1) Rivularia nitida, the species of vertical
peat-banks (p, 82), oceurs as a broad horizontal band. It is noticeable
throughout summer, but in October forms a black band along the whole shore,
(2) Cladophora rupestris, as narrow strips or effused patches, is also very
abundant, indicating the presence of fresh water. It is remarkable that
Enteromorpha, which usually serves this purpose, is, except as a short
growth near high-water line, almost absent. Associations of Porphyra
and Rhodochorton, which might have been expected, were completely
absent.

A general coating of the diatom Cocconeis Seutellum is especially
characteristic of the vegetation of this bay. Species of Cladophora, Ectocarpus,
Polysiphonia, etc., are in spring so completely covered as to be utterly
unrecognizable. The plants appear quite black owing to a ring of brown
substance round the valves of the diatom. The ring is apparently secreted
from the peaty water by Cocconeis. Mr. W. West, who kindly idehtified
the diatom, tells me such a copious deposit is unfamiliar to him.

Fresh-water streanis.—See p. 87.

With regard to the flora, the lists kept show that a very large number of
species occur in the bay, but in small quantity only. Many species were only
found once, but, on account of the poorness of the tide, the low-littoral flora
is compressed into a very small space. The dominant associations—Fucaceae,
Laminaria, Zostera, and pebble-attached—practically cover the ground, and
there are no pools. This type of vegetation is probably not peculiar to Bella-
cragher Bay, as from cursory observations elsewhere (Killary, Roundstone,
also in Scotland) it appears to be frequent in brackish bays of like nature.
In summer Cyanophyceae are abundant, especially Lyngbya majuscula, Calo-
thriz aeruginea, C. confervicuola, and Anabaena torulosa. Stictyosiphon subarti-
culata, Dictyosiphon foeniculaceus, Striaria attenuata, and Chylocladia
kaliformis are dominant on pebbles in spring; whilst in summer Cladophora
Rudolphiana, Enteromorph clathrata var., and Spermatochnus occur in extra-
ordinary profusion. Of species apparently absent, the following may be
noted :—WMesogloia vermiculata, Nitophyllum punctatum, Grifithsia corallina,
G. setacea, and Monospora pedicellata.

B.I.A. PROC., VOL. XXXI. M 15

15 90 Proceedings of the Royal Irish Acauemy.

III]. —THE ALGAL FLORA.
1.—SysTEMATIC LIST OF THE FLORA.’

The subjoined list includes all species, and the most noteworthy varieties
found during the Survey, with the addition, in brackets, of those recorded
previously by other observers. Notes on habitat are given when of interest,
and local distribution is indicated, except where the species is of general
occurrence, Critical notes on the list are given later (pp. 102 et seq.).

The classification adopted is that of Batters’ “ Catalogue of British Marine
Algae” (1902), except for the group Melobesieae, for which Lemoine’s scheme
(10) has been used. The nomenclature also of that catalogue has been
followed, except in the case of certain old names revived by Batters. When these
names appeared invalid or doubtful, the usual and more familiar nomenclature
has been employed. Critical work naturally has necessitated a few additional
name-changes.

The following signs and abbreviations are used :—

*—=new to Ireland. 7 = rare.

+=new to British Isles. J = frequent.

CI = Clare Island. ¢=common.

CB = Clew Bay. ab = abundant.

AS = Achill Sound. 1 =loeal.

BB = Bellacragher Bay. y = young.
CYANOPHYCEAE.

COCCOGONEAE.
Chroococcus turgidus Naeg.—ClI, CB, f. Isolated specimens on various algae.
*A phanocapsa pallida Rabenh.—Cl, CB, f.
*Dermocarpa violacea Crm.—CI, CB,/. On various filamentous algae.
Pleurocapsa fuliginosa Hawck.—Cl7. On bare rocks near high-water line.
a amethystina Rosenv.cCl, CB, 7. On Rhodochorton floridulum and Corallina.
Hyella caespitosa Born. et Flah.—CB f.
HORMOGONEAE.
Spirulina subsalsa Oersted.—Cl, CB, f.
var. oceania Gom.—CIr. On Halichondria panicea.
“QOscillaria margaritifera Kiitz—Cl7.
"3 nigro-viridis Thw.—CIr.

'The additions to the Irish list are calculated from a revised and annotated copy of
Mr. J. Adams’ ‘‘Synopsis.’’ With regard to the Cyanophyceae, several species, which do not
figure in the marine section of the Synopsis, have been previously recorded from Ireland, but
from fresh-water or brackish localities. These were listed by Mr. Adams in the fresh-water
section,

Clare Island Survey—Marine Algae. 15

*Oscillaria Corallinae Gom.—C1f. On Lithothophyllum incrustans.
laetevirens Crm.—CI 7. On Gelidium repens. See note.
brevis Avitz —CI r.
= sancta Aiitz—ClI7r. See note.
limosa 4g.—CI, CB,f. See note.
*Phormidium fragile Gom.—Cl?7. With Ectocarpus on Patella.
tenue Gom.—CI r.
H persicinum Gom.—CI7. See note.
i subuliforme Gom.—ClI7. See note.
*Lyngbya Meneghiniana Gom.—CI?7. On Codiwm tomentoswm in pools.
aestuarii Lzebm.—CBe, AS f.
majuscula Harv.—CB, AS, f.
t confervoides C.4g.—CB/. See note.
= semiplena J. dg.——ClI, CB, AS, 7.
lutea Gom.—CI f. Onrocks near high-water line.
eee hydnoides Aiitz—Cl7r. On Corallina in shallow pools.
+ dubia Gom.—ClI7. On brackish rocks.
=Plectonema Nostocorum Born.—Cl, CB, AS,/. In Rwularia nitida.
tenebrans Born. et Flah.—Cl, The Bills,7. In shells of Balanus.
Battersii Gom.—Roonah Pointr, With Calothria scopulorwm.
norvegicum Gom.—ClIr.
*Microcoleus chthonoplastes Thwr.—AS8, CB, ab. See note.
= tenerrimus Gom.—AS 7.
Calothrix confervicola Ag.—ab.
consociata Born. et Flah—CBr. On Fucus vesiculosus var. muscoides.
scopulorum dg.—Clab, CBr.
pulvinata dg.—CB, AS, f.
cs parasitica Thwr.—Old Heady. In Nemalion multifidwm.
es aeruginea Thu1.—C1 7, Old Head7. See note.
fusca Born. et Flah.—Mnulvanny?. See note.
erustacea Thur.—Cl7. On limpets in high-water pools.
fasciculata Ag.—AS f. On peat-banks.
+ endophytica sp.nov.—Annagh Island. See note.

*

91

Isactis plana Thwr.—CB f, BB/. On stones, and on stems of Lanunaria digitata.

Rivularia Biasolettiana Menegh. (= R. coaduncta Fosl).—Bunowen River /f.

atra Foth.—ab.
nitida Ag.—CB, AS, BB, ab, Cl r.
bullata Berk.—CI f, Mulranny f. On exposed rocks at half-tide level.
*Brachytrichia Balani B. and #.—CI r. In cave at Portlea.
[Mastigocoleus testarum Lagerh.| —Roundstone (coll. Johnson, 1893).
*Microchaete grisea Thwr.—CBr. On shells in 5 fathoms.
Anabaena torulosa Lagerh.—CB, BB, f. On various algae.
M 2

15 92 Proceedings of the Royal Trish Academy.

CHLOROPHYCEAE.
PROTOCOCCINAE.
Chlorochytrium inclusum Ajelim.—c. In Dilsea edulis.
{Halosphaera viridis Schm.|.—f. See note.
*Codiolum gregarium Ad. Br.—ClI f, Old Head rv. On rocks near high-water line.
*Petrocelidis Kuck.—Cl, Old Head f. In Petrocelis crwenta and Cruor OE

CONFERVOIDEAE.
Prasiola stipitata Swhr.—Cl, CB, The Bills, /. On bird cliffs ab, on bare rocks 1.
crispa var. marina Borg. (= Gayella).—CI /, Caher I., The Bills.

“Protoderma marinum Rke.—CB, AS, BB, f. On pebbles, near low-water mark.

*Ulvella fucicola Rosenv.—Old Head. On F’. vesiculosus, probably frequent.

*Monostroma orbiculatum 7’hur.—CB f. See note.

sp. No. 95 (M. crepidinum Farlow ?).—Old Head, LIS 5 . See note.
sp. No. 91.—AS, BB, f. See note.
Grevillei Wittr.—Cl1, AS, c. Epiphytic near low-water mark.

var. Cornucopiae Batt.—Cl1, AS, 7. On Corallina.

*Capsosiphon aureolus Gobi.—-Old Head, Mulranny, J.

Percursaria percursa Rosenv.—c.
Enteromorpha clathrata J. Ag.—c.
paradoxa Aitz.—CB 7, Roundstone (coll. MeCalla). See note.
. torta Reinb.—CB f.
prolifera J. Ag.—CB 7. Attached to stones on flat sandy shores.
compressa Grev.—ab. ;
Linza J. Ag.—c.
intestinalis, Link.—ab.
micrococea Kiitz—CI yr. On rocks near high-water line.
minima Nag.—Cl c. On rocks near high-water line.
Ulva Lactuca L.—ab. See note.
Ulothrix flacea Thwr.—CB f. See note.
* consociata Wille—Roonah f. See note.
t pseudoflacca Wille.—CI, Old Head, Roonah, f. See note.
+ subflaccida Wille—CB, AS, 7. See note.
*Phoeophila dendroides Batt.—BB 7. In old Chylocladia kaliformis.
Bulbocoleon piliferum Pringsh.—ClIr. In old Chordaria flagelliformis.
Blastophysa rhizopus Rke.—ASr. In old Ralfsia sp.on Achill Bridge.
Endoderma viride Lagerh.—CI, CB, f. In Nitophyllum and Delesseria spp.
Wittrockii Wille.—f. In Pylaiella litoralis.
Flustrae Batt.—r. In Flustra sp.

Tellamia contorta Batt.—CI, Roonah, f. In Littorina.
intricata Batt—Roonah 7. In Littorina.

Urospora mirabilis Avesch.—CI/. See note.

Clare Island Survey— Marine Algae. 15 93

Chaetomorpha litorea Cook.—Mulranny. See note.
[tortuosa Kitz.) —C17., Roundstone.
linum AKiitz—CB, AS,c. See note.
aerea Avitz-—-Cle. In high-level rock-pools.
melagonium Avitz.—CI7, Achill Bridge r.
| erassa Avtz.|—Achill (coll. Hanna, 1899).

(Rhizoclonium Kochianum Aiitz.] —Roundstone (teste Batters).
implexsum Batt. non Kiitz. (= R. tortuosum Kiitz.)—Cle.
riparium Harv.—ab.

+ Kerneri f. endozoica Wille.—CI., Achill Bridge,7. See note.

Cladophora prolifera Kiitz. See note. :
pellucida Kiitz.— Clr. In deep or shady rock-pools.
Hutchinsiae Harv.—CB f.

[ Macallana Harv.] —Roundstone (coll. McCalla).
rectangularis Harv.—-CB7. Dredged in 8 fathoms.
Neesiorum Kiitz—ClI7. Rock-pools.
rupestris Avitz.—ab.
(var. distorta Harv. |—Roundstone (coll. McCalla).
sericea Kiitz.—ab.
glaucescens Harv.—ClI r. In rock-pools.
flexuosa Harv.—see note.
albida Kiitz CI f. On rocks and in pools.
var. vetracta Thur.—Clf. On rocks and in pools.
Rudolphiana Harv.—CB, AS, BB,/. See note.
fracta Kiitz.—CB, ASc.
[cornea Kiitz.| —Roundstone (coll. Painter, 1883).
corynarthra var. spimescens Batt—BB/. See note.
arcta Kiitz.—Clc. See note.
uncialis Kiitz—C1If. On exposed rocks.
lanosa Kiitz.CBce. Epiphytic.
Gomontia polyrhiza Born. et Flah.—CB, AS, f. In various shells.
SIPHONEAE.
*Ostreobium Quekettii Born. et lah.—Roonah 7. In shells. Probably frequent.

Bryopsis plumosa Abip Ol AS, f.
| hypnoides Lamowr. |\—Boundstone (coll. Harvey).

Derbesia marina, Kjellm.—Cl vr. See note.

Vaucheria Thuretii Woron.—CB, AS, c. See note.
coronata Nordst._-CB, AS, Bunowen River, c. See note.
littorea Bang. et Ag—CBc. See note.

Codium adhaerens 4g.—CI f. In rock-pools, and on steep, damp rocks.
amphibium Moore.—CI v r, Roundstone. See note.
tomentosum Stackh.—CI c, CB,7. See note sub C. mucronatum.

t mucronatum var. atlanticum var. nov.—Cl1 c; CB, BB, 7. See note.

15 94 Proceedings of the Royal Trish Academy.

FUCOIDEAE.
PHOEOSPOREAE.
Phoeococeus adnatus West, comb. nov.—CB, AS, c. See note.
Desmarestia viridis Lam.—ClI, CB, f.
aculeata Lam.—c.
ligulata Lam.—Cl +.
{Dresnayi Lan.| —Roundstone (teste Johnson, 1899).
Dictyosiphon foeniculaceus Grev.—CB, AS, BB, c.
hippuroides Kiitz.—ClI, CB, c.
Phoeostroma pustulatum Kwek.—ClI r. See note.
Litosiphon pusillum Harv.—Cl 7; CB, AS,c. See note.
Laminariae Harv.—ClI f. On Alaria.
Phloeospora brachiata Born.—Cl f. On Rhodymenia palmata.
Stictyosiphon tortilis Rke.—CB, BB, c.
subarticulatus Hauck.—CB c.
} adriaticus Kiitz.—Bartraw r. See note.
Striaria attenuata Grev.—CB c, AS 7. In shallow sub-littoral region,
Punctaria plantaginea Grev.—-CB +.
latifolia Grev.—Cl, CB, f.
tenuissima Grev.—CB f. On Zostera.
undulata J. dg—CB7, BB r. On Zostera.
*Phyllitis zosterifolia Rke.—ClI 7.
Fascia Kiitz.— CI, CB, AS, J.
Scytosiphon lomentarius J, dg.—c.
Asperococcus fistulosus Hook.—c.
bullosus Lamour.—CB, Cl, c.

*Streblonema sphaericum Derb ¢ Sol.—CI r. In Nemalion multifidum.

*Hetocarpus clandestinus Saw.—C1/. On Fucus serratus, October, 1910.
luteolus Sawv.—ClIf.

s microspongium Batt.—Cl7. On Ralfsia verrucosa.
tomentosoides Far!l.—C1 7. On Himanthalia and Laminaria.
velutinus Aiitz.—CI f. On Himanthalia.

is Battersii Born.—CB ry. On Taonia atomaria.
simplex Crn.—Cl ce. On Codium tomentosum.

se Holmesii Batt.—Cl1, AS, 7. In caves and on dark ledges.
globifer Azitz.— CI 7. On exposed ledges.

Mitchellae Harv. (= EH. virescens Thur.)—CI 7.
confervoides Le Jol.—c.

var. arctus Kjellm.—CB f.
siliculosus Kiitz.—c.
fasciculatus Harv.—Cl «. On Laminaria and Himanthalia.
tomentosus Lyngb.—c.
Hineksii Harv.—Cl ry. On Laminaria digatata.

Clare Island Survey—Marine Alque. 15 95

Eetocarpus [Landsburgii Harv.].—Roundstone (coll. Harvey).
granulosus Ag.—f.

[Sorocarpus uvaeformis Pringsh. |—f. Roundstone (teste Johnson, 1899).

Pylaiella litoralis Ajellm.—ab.

Isthmoplea sphaerophora Ajellm.—ClI f. On Pluwmaria elegans.

Myriotrichia clayaeformis Harv.—c.
filiformis Harv.—c.

S densa Batt.—CB r. On Zostera.
repens Hauck.—Old Head 7. On Eudesme.
+Dichosporangium Chordariae Wol/ny.—Cl7. See note.

Myriactis pulvinata Kiitz.—ClI c. On Cystoseira ericoides and (. granulata.
Areschougii Batt—CI 7. On Himanthalia.
stellata Batt—CIf. On Dictyota in pools.

? Haydeni Batt—C1r. On Scytosiphon in pools.

Elachista fucicola fries.—ab. :
flaccida Aresch—CI, Old Head, c. On Cystoseira granulata and Halidrys.
scutulata Duby.—Cl c. On Himanthalia.

*Leptonema fasciculatum Rke.—CB yr. On Zostera.

Giraudia sphacelarioides Der). dé: Sol—CB 7. On Zostera.

Sphacelaria cirrhosa dg.—c. See note.
britannica Sawv.—r. See note.

ze plumula Zan.—CB, Roundstone.

Cladostephus spongiosus Ag.—c.
verticillatus Loja

Halopteris filicina Avitz.CBr.

Stypocaulon scoparium Aiitz.—7.

Myrionema strangulans Grev.—c.

i Corunnae Sawv.—ClI 7.

papillosum Saw:.—f.

aecidioides Sawv.—CI 7.

saxicola Kuck.—Cl7. See note.

reptans Kosl.—Old Head7. See note.
Ulonema rhizophorum Fosl.—Clc. See note.
Hecatonema maculans Sawv.—Cl f.

reptans Kylin.—Cl, CB,f. See note.

speciosum comb. nov.—CI f. See note.
*Microspongium globosum Reinke.—CIf. See note.
«Chilionema Nathaliae Saw’.—Cl r.
= ocellatum Saw:.—CI r.

Ascocyclus orbicularis Magn.—CBc. On Zostera.

* foecundus comb. nov.—Cl, Old Head, f. See note.
+ Saccharinae sp. nov.—CIr. See note,

15 96 Proceedings of the Royal Irish Academy.

Ralfsia clavata Farl.—ClI, CB, f.
verrucosa Avesch.—c.
*?L. fatiscens Aresch— CBr. See note.
}Petroderma maculans Kuck.—CB 7. See note.
Spermatochnus paradoxus Kiitz.—CB, AS, BB, c.
_ Stilophora rhizodes J. Ag.—AS 7.
Chordaria flagelliformis 4g.—f.
Mesogloia vermiculata Le Jol.—CI/.
lanosa Crn.—CB7. Dredged in3 fathoms.
Griffithsiana Grev.—CB, AS,7. Washed ashore.
+Acrothrix gracilis Kylin.—CB, AS,7. See note.
Castagnea virescens Thur.—Clc; Old Head f.
Zosterae Thur.—CB, BB, f. On Zostera.
Microcoryne ocellata Strémf.—BBr. On Dasya arbuscula.
Petrospongium Berkeleyi Ndg.—CI f. On rocks, and on Ralfsia verrucosa.
Leathesia tuberiformis Aresch.—ab.
crispa Harv.—Cl vr. See note.
Sporochnus pedunculatus A4g.—CI, AS, 7. Washed ashore.
Chorda filum Stackh.—CB, AS, c.
tomentosa Lyngb.—CI 7. In narrow channels.
Laminaria saccharina Lamour.—c.
var. latissima (Twin.) Batt.—CB c.
var. Phyllitis Le Jol.i—C1 ¢.
digitata Lamour.—c.
var. stenophila Harv.—Cl c.
var. vallida Fosl.—CB f.
Cloustoni Edm.—ClI c.
Saccorhiza polyschides Batt. (= 8. bulbosa De la Pyl.)—CI f.
Alaria esculenta Grev.—Cl c.
Cutleria multifida Grev.—CB f. Dredged 3-5 fathoms.
(forma Aglaozonia reptans Crn.—CBab. Dredged 3-5 fathoms.)
FUCINEAE.
Fucus ceranoides 1.—CB, AS, BB, c. See note.
spiralis L.—ab. See note.
var. platycarpus Batt.—CB, AS, ab.
var. nanus Stackh.—CB ¢. See note.
vesiculosus L.—ab. See note.
var. evesiculosus Awct.—CI ab.
var. laterifructus Grev.—AS c.
var. vadorum Aresch.—CB c.
var. balticus J. Ag.—CB, AS, c.
4 var. muscoides var. nov.—CB, AS, c.

Clare Island Survey— Marine Algae. 15 97

Fucus serratus L.— ab.
var. angustifrons Stackh.—CI f.
Ascophyllum nodosum Le Jol.--Cl7; CB, AS, ab.
var. Mackaii (Turner) comb. nov.—Roundstone Bay f. See note.
Pelvetia canaliculata Decne et Thur.—ab.
Bifurearia tuberculata Stackh.—Dog’s Bay, Roundstone. Rock-pools.
Himanthalia lorea Lyngb.—Cl ad.
Halidrys siliquosa Lyngb.—CB, BB, c.
Cystoseira ericoides 4g.—Cl c.
eranulata dg.—CBe. In pools, and in shallow water.
[discors 4g.}] —Roundstone (teste Johnson, 1899).
fibrosa 4g.—CI 7. In rock-pools.
TILOPTERIDEAE.
(Tilopteris Mertensii Aiitz.] —Roundstone (coll. McCalla).
DICTYOTACEAE.
Dicytota dichotoma Lamx.—ab.
var. mmplexa J. Ag.—CI ¢.
Taonia atomaria J. 4g.—CBr. See note.
Dietyopteris membranacea Batt—CBr. See note.

FLORIDEAE.
PORPHYREAE.
Conchocelis rosea Batt.—CB ff. In shells.
Goniotrichum elegans Le Jo/.—Off Annagh Island 7. On Champia parvula.
Erythrotrichia carnea Le Jol.—f.
Bertholdii Batt.—Achill f. See note.
= investiens Born.—See note.
Boryana Berth—Clr. On Lawrencia pinnatifida.
ie Welwitschi Gatt—Clr. See note.
Bangia fuscopurpurea Lyngb.—c.
*Porphyra coccinea J. Ag.—Cl7. See note.
leucosticta Thur.—Cl f. On Fucus spp.
umbilicalis Kiitz.—ab. See note.
var. laciniata J. Ag.—c.
var. linearis Thui.—e.
NEMALIONINAE.
*Colaconema Bonnemaisoniae Batt.—AS 7. In Bonnemaisonia asparagoides.
Chantransia virgatula Thur.—See notes.
* var. laxurians Rosenv.—Cl c, CB r.
% var. tetrica Rosenv.—Cl, CB, r.
var. secundata Rosenv.—ab.
+ Thuretii Kylin.—CB, AS, ¢. See note.

R.I.A. PROC., VOL. XXXI. N 15

15 98 Proceedings of the Royal Trish Academy.

Chantransia endozoica Darb.—CB 7. See note.
Alariae Jons.—CI 7. See note.
[Daviesii Thaw. |—Roundstone.
Nemalion elminthoides Batt.—CI f. See note.
multifidum J. Ag.—ClI ec.
Helminthora divaricata J. Ag.—Old Head c, CI r.
Scinaia furcellata Bivona.—CB 7. See note.
Choreocolax Polysiphoniae Reimsch.—Old Head. On Polysiphonia fastigiata.
*Harveyella mirabilis Schm. et Rke.—CI, CB, f. On Rhodomela subfusca.
Pterocladia capillacea Born.—ClI 1.
Gelidium erinale J. Ag.—Old Head 7. In sand-pools.
pusillum Le Jol.—CI, CB, f.
pulchellum Kiitz.—Cl f.
latifolium Born.—CI r.
* aculeatum Batt.—f. See note.
corneum Lamour.—f.

GIGARTINAE.

Chondrus crispus Stackh.—c.

Gigartina mamillosa J. Ag.—c.

Phyllophora rubens Grev.—CI/; Roonah, Old Head, c.

Brodiaei J. Ag._-Mulrannyr. See note.
Traillii Holmes and Batt.—Roonah 7. In caves.
membranifolia J. 4g.—CI, Roonah, f.

Gymnogongrus Griffithsiae Martiws.--Old Heady. In sand-pools.
norvegicus J. dg.—Old Head r.

Abnfeltia plicata Fr.—-f.

Actinococcus subeutaneus Rosenv.-Mulrannyr. On Phyllophora Brodiaet.
ageregatus Schm.—Old Heady. On Gymmnogongrus Griffithsiae.
peltaeformis Schm.—Old Heady, On G. norvegicus.

Colacolepis incrustans Schm.—Old Heady. On Phyllophora rubens.

Sterrocolax decipiens Schm.—17. On Ahmnfeltia plicata.

Callophyllis laciniata Hiitz.f. Washed ashore.

Callocolax neglectus Schm.—f. On Callophyllus laciniata.

Callymenia reniformis J. dg.—CI7. Washed ashore.

* Larterae Holmes.—C17. Washed ashore. See note.

Cystoclonium purpurascens Kiitz.—c.

Catenella Opuntia Good. and Wood.—CI 7, CB, AS, ¢.

Rhodophyllis bifida Kiitz.—CIf. Washed ashore.

RHODYMENINAE.

Sphaerococeus coronopifolius Grev.—C1f. Washed ashore.

Gracilaria confervoides Grev.—CB, AS,c. See note.

* var. procerrima Batt.—See note,

Clare Island Survey— Marine Algae. 15 99

Calliblepharis ciliata Kiitz—CIf. Washed ashore.
jubata Kiitz.—CI f. Rock-pools.
Rhodymenia Palmetta Grev.—CBf. Onstems of Laminaria Cloustoni.
palmata Grev.—c.
“S var. sarniensis Grev.—CBr. On stems of Laminaria digitata.
Cordylecladia erecta J. dg.—CB /.
Lomentaria articulata J.dy.—c.
clavellosa Gaill.—f.
Champia parvula Harv.—CB 7.
Chylocladia kaliformis Hook.—ab.
ovalis Hook.—c.
Plocamium coccineum Lyngb.—ab.
Nitophyllum punctatum Grev.—CB, AS, c.
Bonnemaisoni Grev.—CB, AS, r. Washed ashore.
ce var. crassinerva Batt.—CI r. On Laminaria Cloustone.
uncinatum J. dg.—CB /. See note.
laceratum Grev.—e.
var. uncinatum Batt.—f. See note on N. wncinatum.
Gonimophyllum Buffhami Batt.—f.
Delesseria sinuosa Lamour.—c. On stems of Laminaria Cloustoni.
sanguinea Lamour.—f.
alata Lamouwr.—c.
(augustissima G7if?.] —Galway (coll. Reilly, teste Harvey in Phye. Brit.).
ruscifolia Lamowr.—ClI 7, CB, AS, c.
hypoglossum Lamour.—c.
Bonnemaisonia asparagoides 4g.—CI, CB, r. Washed ashore.
ae hamifera 4g.—CI, AS, Roonah Pt.,7. Washed ashore. See note.
Bostrychia scorpioides Mont.—CB, CI, 1.
Rhodomela subfusea Ag.—f.
Laurencia obtusa Lamour.—CB, AS, c. See note on L. hybrida.
hybrida Lenorm.—c. See note.
pinuatifida Lamour.—ab. See note on L. hybrida.
Chondria tenuissima Ag.—CB r.
dasyphylla 4g.—CB, AS, f.
Polysiphonia macrocarpa Harv.—ClI f. See note.
fibrata Harv.—Cl1 c. Especially on flat, semi-exposed rocks.
urceolata Grev.—c.
elongata Grev.—ClI r; CB, AS, ab.
elongella Harv.—a8S r.
violacea Grev.—CB, AS, f.
fibrillosa Grev.—CB f.
furcellata, Harv.—Cl1, Roundstone, r.
N2

15 100 Proceedings of the Royal Lrish Academy.

Polysiphonia fastigiata Grev.—CI f; CB, AS, ab. See note.
atro-rubescens Grev.—Cl 7, CB ab.
nigrescens Grev.—CB, AS, c.
Brodiaei Grev.—c.
subulifera Harv.—CB, AS, /. See note.
fruticulosa Spreng.—c.
Pterosiphonia parasitica Schm.—f. In deep pools and in sub-littoral region.
thuyoides Schnutz.—Cl f, Roonah ab.
Brongniartella byssoides bory.—CB ab.
*“Dasya corymbifera Cru.—CB rv. Dredged in 5 fathoms, and washed ashore.
arbuscula Ag.—ClI f, Bellacragher Bay 7. See note.
Heterosiphonia coccinea Falk.—f.
Spondylothamnion multifidum Ndg.—Cl 7, CB f.
Spermothamnion Turneri, Avesch.—ClI f, Old Head ab.
i var. subyerticillatum, comb. nov.—CB f. See note.
Ptilothamnion pluma Thwr.—Cl, CB, f. On stipes of Laminaria Cloustont.
f lucifugum sp. nov.—Cl r. See note.
Griffithsia corallina 4g.—CB, AS, ab. See note.
setacea Ag.—-CI r, CB /.
Halurus equisetifolius Avitz.—f.
*Bornetia secundiflora Thur.—Cl very rare. See note.
Monospora pedicellata Sol.—Cl1 7, CB /. In rock-pools and in sub-littoral region.
Rhodochorton membranaceum Magn.—CB r.
Rothii_Ndg.—ClI f, Roonah f. In shady situations only.
parasiticum Batt.—f. On stipes of Laminaria Clouston.
floridulum Nag.—ab.
Callithamnion byssoides d47m.—CB, AS,7. See note.
polyspermum dAg.—f.
scopulorum Ag.—CI f. See note.
roseum Harv.—AS8, BB, f.
[tripinnatum Agardh.| —Roundstone f (coll. McCalla).
Hookeri dg.—Gl ¢. On Cladostephus spongiosus.
arbuscula Lyngb.—CI c. On steep exposed rocks. See note.
tetragonum dy.—CI7. On blades of Laminaria digitata.
corymbosum Lyngb.—CB, AS, c. See note.
granulatum Ag.—Cl17. See note.
Seirospora Griffithsiana Harv.—aS r.
a hormocapa Bait.—AS very rare.
[Compsothamnion thuyoides Schm.]—Roundstone (coll. McCalla).
Plumaria elegans Schm.—c.
Ptilota plumosa Ag.—c. On stipes of Laminaria Cloustoni. See note.
Antithamnion cruciatum Nag.—Cl very rare. On vertical rocks near low-water.

Clare Island Survey—Marine Algae. 15 101

Antithamnion crispum J. Ag.—f. See note.
Ceramium tenuissimum J. 4g.—CB /.
strictum Harv.—f.
var. zostericolum Le Jol.—CB, BB, f.
diaphanum Hoth.—f.
Deslongchampsii Chawv.—Cl r.
Boergesenii Petersen.—c. See note.
rubrum Ag.—ab. See note.
var. pedicellatum J. dy.—c.
var. secundatum Petersen.—Cl f.
t atlanticum Petersen.—CI, The Bills, 7. See note.
flabelligerum J. 4g.—Cl f.
echionotum J. dg.—CIr.
ciliatum Ducluz.—e.
acanthcnotum Curm.—Cl c.
CRYPTONEMINAE.
Gloiosiphonia capillaris Carm.—Cl 7. See note.
Dumontia filiformis Grev.—e.
Dudresnaya verticillata Le Jol.—Cly, CB f. Washed ashore.
Dilsea edulis Stackh.—ClI, Roonah, c.
Schizymenia Dubyi J. dg.—CI7. See note.
Halarachnion ligulatum Aiitz.—f. Washed ashore.
Furcellaria fastigiata Lamowr.—c.
Polyides rotundus Grev.—CBc.
Petrocelis cruenta J. dy.—CIc. On smooth rocks near low-water.

+ Hennedyi Batt.—CBr. On stipes of Laminaria Cloustone.
Cruoria pellita Lyngb.—Cl, CB, 7. In caves, and dredged in 5-7 fathoms.

adhaerens J. d4g.—Dredged in 4 fathoms. See note.
Cruoriella Dubyi Schm.—CB ab. See note. i
Peyssonnelia sp.—CB yr; Roundstonec. See note.
Hildenbrandtia prototypus Nardo.—ab.

*Porphyrodiscus simulans Batt.—CB7. See note.

*Rhododermis polystromatica Batt.—CB 7. See note.
Rhodophysema Georgii Batt.—CB, AS, c. On Zostera.
Schmitziella endophloea Born. and Batt.—Cl r. In Cladophora pellucida.
Choreonema Thuretii Schmitz.—CI r. See note.
Melobesia farinosa Lam.—CB, AS, c. See note.

zonalis Fosl.—CB f. See note.
Lithophyllum (Dermatophyllum) pustulatum /osl.—Cl c. See note.
vor. Corallinae Fosl.—Cl c. See note.
vor. Laxninariae Fos]—CB f. See note.
hapalidioides Fos/.—Cl, Roonah, f. See note.

15 102 Proceedings of the Royal Trish Academy.

Lithophyllum hapalidoides var. confinis Fosl.—CB 7. See note.
incrustans Phil.—ab. See note.
t var. subdichotomum Heyd:.—CB, Roundstone, 7. See note.
lichenoides Hilis.—CI, CB, c. See note.
[var. agariciformis] os/.—Roundstone 7. See note.
fasciculatum Fosl.—CB 1. See note.
Lithothamnium calcareum Aresch.—CB c. See note.
x norvegicum /jellm.—CB f. See note.
laevigatum Fosl.—Cl, CB, 7. See note.
polymorphum Avesch.—c. See note.
compactum Kjellm.—CB 7. See note.
Lenormandi Aresch.—c. See note.
ze var. sublaevis Fosl.—f. See note.
var. squamulosa Fosi.—f. See note.
Sonderi Hauck.—CB f?. See note.
Epilithon membranaceum Hedyr.—Cl, CB, f. See note.
Corallina officinalis L.—ab.
squamata Hllis.—c. See note.
rubens Ellis et Soland.—c.

The above list contains the names of 437 species and 36 varieties. Of these
3 species and 2 varieties are new to science; 18 species are additions to the
flora of the British Isles,and in all 92 species and 11 varieties are new to
lreland. For further details consult Part iv. of the present report.’

2.—NOTES ON THE LIsT.
Oscillaria laete-virens Cru.
The cells of the Clare Island specimens are slightly longer than usual in
proportion to their width, the filaments being 4 » wide, and the cells 6-84
long.

Portlea, May, 1911; with Gelidiwm repens on the under-side of boulders.

'Mantxe Funet.—Four species of marine fungi were observed, and may be noted here. (See
Report No. 13 of the present series.)

Ostracoblabe implexa Born et Flah.—A shell-boring species. CB rare.

Epicymatia Balani Winter.—Common on barnacles. CB and CI.

Mycosphaerella Ascophylli Cotton.—Constantly present on receptacles of Ascophyllum.

Leptosphaeria Chondri Rosenvinge.—Very rare, and second record for British Isles. On
Chondrus, washed ashore on Clare Island. (For notes on the above fungi see Cotton, ’09.)

Miss J. Stephens drew my attention to an endophytic organism growing in the sponge Zerpios
fugax, and giving it a deep blue colour. The organism is apparently a Schizomycete (see Topsent,
Arch. Zool. exp. et gén. (3) viii 1900). Tenpios fugav is rare on Clare Island, but not uncommon at
extreme low-W“! mark on the islands of Clew Bay.

Clare Island Survey—Marine Algae. 15 1038

Oscillaria sancta Kiitz..

A fresh-water species, common in Britain; but with the exception of
specimens sent out by Holmes (“Algae Rariores,’ No. 268) it has not been
recorded for our islands from a marine habitat.

Portlea, October, 1910; May, 1911; on various algae at mouth of cave.

0. limosa Ag.

As in the case of many Cyanophyceae, 0. limosa, though usually a fresh-
water species, should certainly be included ina list of marine algae. It was
found intermixed with other brackish species on piles at the side of a stream
at Mulranny (Aug, 1911).

In addition to the above record, a cyanophyceous growth on the sand, both
in Achill Sound and at Mulranny, appears to be referable to this species. At
Achill the growth occurred between the Fucus plants in the “farms”
in the middle of the Sound; and at Mulranny it was found amongst
Rhizoclonium and Vaucheria on the upper part of the tidal region. The
filaments are straight, non-attenuated, non-capitate, bright blue-green in
colour, and measure 10-16 » in diameter. In some cases a distinct, somewhat
mucilaginous sheath is present, a peculiarity which has been noted previously
in O. limosa, and which led to a distinct species, Lyngbya obscura var. aestivalis,
being described by Hilse. The only point in which the specimens differed
from the normal fresh-water 0. limosa was in the filaments being at times
slightly torulose.

Phormidium -persicinum Gom.

This very distinct species, which is new to the British flora, was described
by Reinke in 1889, and has since been recorded from various localities in
Europe and America. The rose colour, coupled with the exceedingly fine
filaments (1°5-2 ») and long cells (2-7), mark it sharply off from other
marine species. The previous record of this plant as British (Journ.
Bot., xxxiv, p. 7) was an error, the plant found being Phormadiuwm Ketocarpi
Gom. (Batters, 00, p. 569).

Clare Island, October, 1910, forming a dense rose-coloured coating on

Codium tomentosum in a rock-pool.

P, subuliforme Gom.

The plant referred to this species was found with Calothrix scopuloruim on
rocks near high-water line. First described by Grunow from St. Paul
(Pacific), it has since been recorded from Nebraska and Iceland (Journ.
Bot., xl, p. 245). Though not previously noted as marine, it agrees so well

15 104 Proceedings of the Royal Trish Academy.

with Gomont’s description that it is here recorded under his name, though it
is possible that further work may show that it is a distinct species. In
St. Paul and Iceland it occurred in warm springs; but it is well known that
many algae which usually grow in ordinary temperatures are also found in
such positions.

Clare Island, Kinnacorra rocks, near high water, October, 1911.

Lyngbya confervoides C. Ag.

Well known on the north coast of France, but apparently not hitherto
recorded as British. It closely resembles Z. aestuarii, and might almost be
regarded as a form of that species; Gomont, however, keeps them distinct.
The Clew Bay specimens are rather slender, usually measuring 10-14, diam.
The sheaths, even in old and empty filaments, remain quite hyaline.

Louisburgh and Mulranny, September, 1911, in brackish pools; probably
common,

Microcoleus chthonoplastes ‘Thur.

It is surprising that this well-known and cosmopolitan species should not
have been previously recorded for Ireland, where it forms,as elsewhere, a definite
though inconspicuous plant-association (see p. 63). Adams listed it in his
‘Synopsis ” (08), but excluded it in 1910 (p. 211), as no published record of
the plant could be found. It is abundant in Clew Bay, and is doubtless
common in other parts of Ireland. I took several samples from the banks of
the river Bann in May, 1910.

Calothrix aeruginea Thur.

Apparently new to Ireland. Recorded by Adams in his “ Synopsis,” but
removed in his second paper (710, p. 211). Epiphytic on various algae, especially
at Old Head.

C. fusca Born. et Fah.
A species usually regarded as being confined to fresh-water; but found
in plenty on Rhizoclonium riparium in brackish pools at Mulranny. It was
listed by Adams as an Irish fresh-water species.

C. endophytica sp. nov.’ (Plate 10, figs. 1-3).

Plants endophytic in the thallus-cavity of Enteromorpha sp., nearly black
in the mass. Filaments simple or rarely slightly branched, very short,

1 C. filis intra thallos Enteromorphae entophyticis, brevissimis 70-130 altis, 7-10 crassis,
aeruginosis; vagina tenui, achroa, vel lutescente, sursum gelatinosa, diffluente; trichomatibus
7-8 crassis, attenuatis; articulis diametro brevioribus vel subaequilongis; heterocystis 1-2,
basilaribus, rare intercalaribus.

Clare Island Survey—Marine Algae. 15 105

70-130 x 7-10 w; blue-green to olive-green ; base not thickened. Sheaths
thin, colourless, or becoming slightly yellow with age; diffluent above or
absent. Trichomes 7-8 « thick, attenuated, but not ending in a hair (dried
specimens only examined); cells usually shorter than wide. Heterocysts 1-2,
basal or rarely intercalary.

In Zateromorpha torta Reinke (?). Salt-marsh, Annagh Island, Oct., 1910.

This species gives to the Enteromorpha filaments in which it grows a
deep, almost black, colour, which caused them to stand out conspicuously
against a background of Rhizoclonium. ‘The plant-mass was distinguishable
in the field from Oscillaria and Lyngbya, and was collected as a very dark
species of Enteromorpha. On examination, however, the tubes were found
to contain blue-green filaments, which for the most part were tightly packed
along the whole length of the Enteromorpha fronds. A good supply of
material was collected, all of which showed the same phenomenon, so that
there can be no question of accidental growth.

Tts remarkable habitat renders the plant very distinct; and except for
C. parasitica, no species of similar habit has been described. In the latter,
the filaments are embedded in the thallus of Nemalion; but they occur in
fascicles, and project at right angles from the host-plant. The cells of the
present species vary considerably in length; and the lateral walls may be
straight or markedly torulose. In October, 1910, the plant was plentiful on
the sait-marsh ; but in May, 1911, it was searched for in vain.

Haplosphaera viridis Schn.

Mr. G. P. Farran tells me that this species has been noted in the
plankton of the Clare Island district during the cooler months of the
year.

The following table, drawn up from Gough’s list (04), is of interest in
showing the marked seasonal development of the plant -—

Skullmartin (Co. Down), March, Apyil.

South Arklow (Co, Cork), February—April ; September, October.
Coningbeg (Co. Wexford), January-May ; September—December.
Fastnet (Co. Kerry), February, March; (July) September—December.

Codiolum gregarium braun.

Much diversity of opimion exists as to the limits of the species of
Codiolum. All the Clare Island forms occurring commonly on the rocks
in company with Calothriz scopulorum, I have referred to C. gregariwm.
The plants vary much in size and length of stalk; the head in the larger
specimens being about 250 long by 50-70, broad, and passing either

R.1.A, PROC., VOL. XXXI, : O 15

15 106 Proceedings of the Royal Irish Academy.

gradually .or abruptly into the stalk; but in any one gathering many
intermediate forms are found. It agrees well in form with Braun’s specimens
(Rabenhorst, “ Alg. Eur.,” No. 1841), but is somewhat smaller. It also
appears to agree with the Berwick gatherings (Holmes, “ Algae Rariores,”
No. 33), which Batters (89, p. 44) referred to C. gregariwm, but which, in
1902, he placed under (. pusillum Foslie. Judging by Bérgesen’s figure
of the original material (02, fig. 107), it would appear that Batters’ earlier
view was the more correct. The specimens of C. pusillwm distributed
by Wittrock and Nordstedt, and by Hauck and Richter (Exsicc., Nos. 457
and 472 respectively), agree with Borgesen’s figure in possessing an extremely
long head, and such specimens are easily distinguished from the normal form
of C. gregarvum.

With regard to the other species, the Clare Island observations tend
to show that names have been proposed far too freely; and it is clear that
nothing but a special study with careful and systematic collecting throughout
the year will bring about a true understanding of the genus.

MONOSTROMA.

In common with many algae of brackish regions the Monostromas
present endless trouble to the systematist; but it would seem that few
of these genera would so readily repay careful study in the field. The
characters upon which the species are founded—the size, shape, and thickness
of the frond, and the size and form of the cells—are known to vary much
with external conditions. If the ecology of the plants could be studied, and
their growth traced through from the earliest attached stages to the loose
floating forms, it is certain that many puzzling intermediates could be placed,
and that several of the so-called species would have to disappear.

Of the numerous forms noted in Clew Bay, JZ. orbiculatum was recognizable ;
and two others that were sufficiently distinct and frequent to be worthy of
record, could not be satisfactorily determined, and are hence referred to by
collecting-numbers only.

M. orbiculatum Thur.

A plant common during April and May in the brackish pools of the salt-
marsh near Belclare. It is at first attached to stones, sticks, or leaves
and shoots of flowering plants, but finally becomes free. It often grows
in dense tufts, and may reach as much as 1 foot to 18 inches across. The
fronds are densely plicate, usually orbicular, but sometimes partly sub-
lanceolate; on detachment they become very irregular, but, owing to
spring-tides flooding the pools, it is difficult to be certain as to the origin
of free-swimming plants,

Clare Islund Survey—Marine Algae. 15 107

No. 91.

This well-marked plant occurs abundantly at the bottom of the hill-side
streams which flow into Achill Sound and Bellacragher Bay. It grows
attached to stones or other algae such as F. ceranoides, and though flooded
by every tide, it is for the greater part of the day immersed in fresh water.
A certain amount of growth occurs above the average high-water line; and
this is bathed in salt water at spring tides; but the plants are small, and the
growth very poor, compared with that of half-tide level. he lower limit is
at or slightly above low-water mark. Monostroma gives the stony beds of
the Bellacragher torrents a deep green colour in spring; but in other streams
(eg. to the north of Achill Bridge) the beds are muddy, and the alga
occurs only on the stone fords or where there is good means of attachment.
The growth is found in spring, summer, and autumn; in February,
also, a certain amount was visible. The maximum is reached in April and
May, at which season it extends to the stones and Fuci on the flanks of the
streams (see also p. 87).

The plants themselves are of a deep green colour, growing in rosettes
or dense tufts, regularly orbicular at first, but becoming more or less lobed
or even lanceolate later. They are usually 5-8 cm. across; but lobed
specimens reach a length of 15-18 cm. The thallus is thin, that of the
adult plant seldom measuring more than 20-25 thick, and the cells
small, about 10-14 x 6m in section; but in young plants they are often
larger. It adheres very well to paper, even in the dry air of the herbarium.
The plant has only been found attached, as detached specimens are swept
down by the stream and carried away; in a free state, it would probably
reach a larger size.

With vegard to affinities, the plant agrees in structure with
Thuret’s I. Jaceratwm; but he describes this as floating in ditches
with Obione. From WM. orbiculare, so common near Belelare, it differs
in its smaller size and thinner frond; but it is possible that this is
due to its peculiar habitat. On the other hand, the plant may be regarded
as a small attached form of MW. latissimum, or as a distinct species peculiar
to the situation referred to.

No. 95 (= I. crepidinum Farlow ?). ‘

The second species left unnamed occurs on the banks of the streams

on the sandy shore at Mulranny, and at the mouth of the Bunowen at

Louisburgh. It is attached to the stems of Ascophyllum and J. vesiculosus

(especially on the under branches), but is also found on the stones and rocks

covered by these algae, and occasionally in the open. The plants are always
O 2

15 108 Proceedings of the Royal Irish Academy.

uncovered during low-tide, and have not been noted in pools; thus, though
swept with a considerable amount of brackish water on the ebb-tide, its
habitat differs considerably from that of the last species. It is not abundant,
but has been found, with the exception of the February visit, each time the
localities have been searched.

When young, the plants are more or less orbicular, but soon become
deeply divided and very irregular. They occur in small clusters and are of
medium size, an average specimen being 10-12cm. in length; a few larger
fronds were found floating in pools; but it was not quite certain if they
were detached from this species or from M. orbieularis. The thallus is usually
about 30 u thick; and, unless growing in deep shade, is of a very pale colour
(cf. No. 91).

The agreement with MZ. crepidinwm is, in deeply-cut angular specimens,
fairly close; but, in others, it is less marked, the fronds being large and
irregular. The American specimens in the Kew Herbarium adhere very
tightly to paper, which is not the case with any of the Clew Bay material.
The lobed fronds appear to separate it from being a marine form of
M. orbicularis.

Enteromorpha paradoxa var. tenuissima (Kiitz.), Batt.

A few specimens of this beautiful species were found washed ashore at
Old Head (August, 1911). Though in poor condition, they are without doubt
referable to the plant named #. Hophirkii by McCalla. The small chromato-
phores, and the monosiphonous ultimate ramulae, separate it from the majority
of the richly-branched species; and its extreme delicacy distinguishes 1t from
E. erecta Hook. The plant has suffered much at the hands of systematists,
and its position will probably continue uncertain till the genus is thoroughly
revised. I have followed Batters (without investigating the point) who has
united it with Kiitzing’s #. tenwissima, which he regards as a variety of that
author’s 2. paradoxa.

Ulva Lactuca L.

For recent work on the biology and ecology of Ulva, and especially its
growth in polluted waters, see Reports to the Sewage Commission (Letts and
Richards ’11; Cotton ’°110). An account of the structure of the basal disk
has also been published recently by Miss Delf (12).

In the pure waters of Clare Island the plant is one of the most abundant
species in the more sheltered rock-pools during summer and autumn. It
is frequent on rocks also at Portlea and at Old Head; but in none of these
' localities does it attain a great size. Large specimens may be dredged in

Clare Island Survey—Marine Alyae. 15 109

Clew Bay, where the water is quiet and muddy ; but here it is local, and not
generally distributed. On the bridge near Murrisk it was noted attached to
mussels, as at Belfast and Southampton.

ULOTHRIX.

The species of Ulothrix were kindly determined by Dr. N. Wille. Two
new species are added to the British flora, but one of these may represent the
plant named by Batters U. amplexa.

U. flacea Thur.

Common on the flat sheltered shore of the mainland, but not found on
Clare Island, the plant of exposed coasts being now regarded as a distinct
species—viz., U. pseudoflacca Wille.

On my February visit especially, U. flaeca was tound in thin, felt-like
masses, just below high-water line, on the muddy shores of Clew Bay and
Achill Island. The filaments usually measured 40-50 u diam. ; and the cells
contained a large ring-like chromatophore with 4-6 pyrenoids. U. flacca is
not listed in the “ Synopsis,’ but Mr. Adams tells me that the plant was
included as a synonym of Uvospore isogona (see Urospora mirabilis).

U. consociata Wille.

Apparently common in the district during winter and spring. It was
found on boulders near high-water line at Portlea, and was abundant at
Roonah in similar positions during February. Collins (09, p. 186) designates
this species U. /wetevirens (Kiitz.) Collins.

U. pseudoflacca Wille.

Not previously recorded for the British Isles, though doubtless passed
over as U. flacea. On Clare Island it is the dominant species of the Bangia-
Ulothrix-Urospora association, and is also frequent as an epiphyte on various
algae, especially the stems of Fucus vesiculosus. On Alnahaskilla it formed a
dense and tangled coating on Lichina pygmaea.

U. subflaccida Wille.

To this species a very slender plant, found on muddy stones near high-tide
level, is referred by Wille. The filaments are only 7-10 u diam., and possess
band-like chromatophores, with one pyrenoid. From the description given
by Batters (89, p. 35) it appears probable that it is the plant referred by him
to U. impleza Kiitz.; but Professor Wille informs me that it is quite impossible,
from the meagre description, to determine the identity of Ktitzing’s species,

Bunoweu Liver and Achill Sound, February, 1911

15 110 Proceedings of the Royal Irish Academy.

Urospora mirabilis Aresch. (= U. isogona, Batt., 02, p. 14.)

This is the common species on Clare Island, only a few filaments doubtfully
referable to U. Wormskioldii being found in addition. The combination
proposed by Batters is questionable. No type of Conferva isogona Eng. Bot.,
can be found; and even if it could, it is improbable that its specific identity
could be recognized. The present plant was confused, in the older Irish
records, with Ulothria flacca.

Chaetomorpha litorea Harv.

Some small pieces of a Chaetomorpha collected at Mulranny appear to
belong to this species. The cells are 90-110 u diam., and 1-14 times as
long, and rather thick-walled. Carmichael’s Appin gathering is not to be found
at Kew, and consequently Wyatt Exsicc., No. 220, must be regarded as the
type (see “ Phyc. Brit.,’ Pl. 535). It is doubtful if the species is not merely
a slender form of C. linwm.

C. linum Kiitz.

Adams records (. /inwm in (?08), but excludes it in (10). In the second
paper it was regarded as a synonym of C. crassa; but as it is most unlikely
that all the Irish records of this common plant could be referable to that
species, | have not considered the Clew Bay gatherings as an addition to the
Irish flora.

Rhizoclonium Kerneri Stockm. f. endozoica Wille.

This addition to the flora of the British Isles appears to be not uncommon
in the west of Ireland, being found on several occasions during the Survey.
It is probably general on our shores, but its curious habitat—within the
tissues of the sponge Halichondria panicea—doubtless accounts for its being
overlooked.

The first specimens were collected under the bridge at Achill Sound,
where patches of sponge of a deep green colour were noted. The latter were
found to contain algal filaments which agreed with Wille’s description of
R. Kerner f. endozoica that had just been published (10, p. 291). Specimens
were forwarded to Dr. Wille, who confirmed the point, and added, “Es ist
doch sehr zweifelhatt ob die Alge zu &. Kerneri gehort, aber ich habe keine
sichere Vermehrungsorgane gefunden, und mochte deshalb vorlaufig nicht
eine neue Gattung autfstellen.” The alga was found later in sheets of
Halichondria in the caves near the lighthouse on Clare Island, and was noted
on both subsequent visits to Achill Sound, but in each case the specimens
were sterile, so that no fresh light on the affinities of the alga could be
gained. A curious bacterlum-lke plant living in the sponge Zerpios fugaz is
recorded on p. 102 (foot-note).

Clare Island Survey—Marine Algae. 15 111

Cladophora prolifera Kiitz.

One of the interesting additions to the Ivish flora, and found on The
Bills rocks only. It is not uncommon on various coasts of southern Europe,
and a single record exists for the British Isles, the plant having been washed
ashore in profusion at Weymouth in November, 1884 and 1885 (see Holmes,
« Alo. Brit. Rar.,” No. 32). The Irish specimens were found in rock-pools on
the shady side of the islets (July, 1910).

C. flexuosa Harv.

The plant referred to this species was collected in pools under the shade
of boulders in Clare Island in July, 1910. It agrees very closely with the
specimens in “ Algae Danmonienses” (No. 227), on which the species was
founded, though it is open to question whether the plant is not a form of some
other species.

C. Rudolphiana Harv.

This species, though rare in England and Scotland, is,as noted by Harvey,
abundant on the west of Ireland. Itis Conferva Kaneana of McCalla (“‘ Algae
Hibernicae”’). The Clew Bay specimens agree well with Harvey’s figure and
description, and are undoubtedly the same as his plants; but whether they are
identical with C. Rudolphiana, as understood on the Continent and in America,
is not certain. (See “ Phye. Brit.,” Pl. [xxxvi.)

C. corynarthra Kiitz., var. spinescens Batt. ('00, p. 370).

A curious plant, which appears to agree with variety spinescens of this
little-known species, was found amongst stones and damp soil near high-
water mark at the Mulranny end of Bellacragher Bay. Batters’ specimens
were collected at Roundstone, and occurred amongst the roots of Zostera.
The Mulranny habitat is a remarkable one, the more so as the plant appeared
to be confined to the stone-area referred to.

C. arcta Kiitz.

The name (. arcta is used here in its wide sense, and includes several
other so-called species. Kjellmann’s work, though useful, left things in a
most confused state. A point which has been largely overlooked is that the
original (. avcta in its best-known and typical forms has hooked branches,
though these are not so numerous as in some of the recently proposed species.
Many of Miss Hutchins’ Bantry Bay specimens (on which the species was
founded by Dillwyn) exist at Kew; and the plant is common in England and
Ireland. Hooked branches are always present. In certain forms (especially
those in the north of Britain) the growth is less dense and the recurved

“5, 112 Proceedings of the Royal Trish Academy.

branches are more numerous, These are inseparable from <Acrosiphonia
albescens Kjellm., and A. incurva Kjellm., which Borgesen found so abundantly
in the Faerées. C. Trailliz Batters is also hardly distinct from C. arcta. All
these forms appear to exist on Clare Island; but they pass imperceptibly
into one another. The species vary greatly with age, and with habitat, so
that for a satisfactory revision it is essential that much time be spent in
field work.

Derbesia marina [Kjellm.

T'wo patches of this plant were found—(1) in a cave near Portlea, and
(2) on the dark under-side of a slab, at Kinnacorra, attached to Halichondria
panicea. In the latter case the alga formed tufts about 1 em. high of a pale
green colour. At the base there is a mass of creeping filaments, and from
these spring upright shoots with numerous lateral branches coming off at an
acute angle. The latter are much more slender than in the Finmark and
FaerGese plants, being only 20-304 diam., but they agree in possessing the
short cells at the base.

The cave-specimens (which grew in or at the margins of shallow pools)
were. much less regular in growth, the branches springing from the main
filaments at various angles, but they agreed in size and in presence of the
short cells. The matted growth at the base is more copious and the upright
filaments are shorter than in the plants from the open. Sporangia were
found on the cave-specimens only. These were few in number and hardly
mature ; the largest measured 120—65y, which is smaller than those recorded
previously.

Kjellmann described D. marina (Lyngb.)in full; and Borgesen in dealing
with its distribution records the plant from Lerwick (02, p. 520, ’03, p. 303).
Up to the present this has been the only certain record for the British Isles.
It appears probable from the Portlea specimens that Crouan’s D. repens may
be a form of the present species.

Vaucheria Thuretii Woron.

This species occurs halt-buried in the mud on the lowest part of the shore ;
and it covers wide areas of the mud-flats in Clew Bay and Achill Sound (north
end). It is distinguished by numerous small sessile antheridia found in the
neighbourhood of each oogonium and on the same filament. At times the
growth is so covered with mud as to be hardly visible, but even in this
state it provides, on washing, excellent fruitmmg material. Found in fruit,
May, July, September, at Annagh Island, Mulranny, and Achill Sound. (See
p. 64.)

Clare Island Survey—Marine Algae. 15 113

Vaucheria coronata Nordst.

Easily recognized when in fruit by the fecundation-tubes which crown
the oogonia. It occurs on the upper parts of muddy shores in which it forms
beautiful velvet-like sheets of a deep green colour. It is common at Louis-
burgh (Bunowen River), Annagh Island, and Mulranny, and was found in
spring, summer, and autumn.

V. litorea Agardh,

Common on the muddy shores of the inner part of Clew Bay. It is
monoecious, and fruits freely, Belclare material showing abundance of ripe
oogonia in May,1911. The latter are subglobose, and borne on the extremity
of straight or recurved branches which in many cases appear to represent the
main shoot, indicating that the branching is of a sympodial nature.

Codium amphibium Moore.

This rare species was found on a ledge at the mouth of a cave on Clare
Island (1909 and 1911). In 1909 its identity was doubted, as it appeared
possible that the specimens represented a crop of young plants of C. tomentosum.
But in August, 1911,a much more characteristic growth was found in the
same cave, the sheet measuring some 15 x 9 inches. A passing shower proved
fortunate in showing that the patch occurred in a spot where rain dripped
from the roof, which confirmed its claim to be amphibious.

A special search for the plant was made at Roundstone (from whence
if was described in 1845) during September, 1911, but without success. The
amount of suitable ground in the neighbourhood is large, and though not
discovered in a one-hour search, it is quite possible that it still exists.

In the Clare Island specimens, the fronds are 5-8 mm. high, and 1:5-2 mm.
thick ; the full-grown utricles are clavate and thin at the apex ; they measure,
on the average, 500x150. The creeping filaments forming the effused
stratum at the base are freely branched, somewhat irregular, and contain much
chlorophyll; they vary from 30-50 yu in thickness. Though a large number of
fronds were examined, no fertile utricles were found. Outside Ireland,
C. amphibium has been recorded from Cornwall and the Isle of Man.

C. tomentosum Stackh.

As great difficulties exist in many countries with regard to the limitations
of C. tomentosum, a full description is here inserted. The species varies
considerably, and has been recorded from all parts of the world; but as it was
originally described from an English specimen, the British plants may be
regarded as typical.

B.I.A. PROC., VOL, XXXI. 12) 15

15 114 Proceedings of the Royal Irish Academy.

Description—Plants rather slender, much branched, 9-15 inches high as
a pool plant, 2-23 feet when growing in deep water. Colour dark green.
Fronds slender, 3-4 mm. thick, cyclindrical, often slightly flattened at the
axils, dichotomous; surface often very tomentose, becoming smooth with
age. Utricles cylindrical, small, 500-650 long, by 120-170 (rarely to 220)
wide, apex usually distinctly thickened, blunt; smaller utricles sometimes
pointed, but never mucronate. Gametangia (?) small, 200-250 x 40-70;
gametes 20-22 x 10-12.

Habitat.—On rocks near low-watermark usually semi-exposed, or in deep
or shady rock-pools ; saxicolous or epiphytic: also in the sub-littoral region,
often on stipes of Laminaria Cloustont.

Season.—All the year round; many plants reaching maximum size in winter.

In comparison with many localities on the south and east of England,
C’.tomentosum is common in the west of Ireland. Very large plants were noted
in February, both in pools and from deep water. One specimen on Laminaria
Cloustoni measured a yard in length. In most cases the fronds are cylindrical,
but in some there is a marked flattening, especially in specimens washed
ashore from the sub-littoral region.

The chief points of distinction between the present species and
C. mucronatum are (1) the slender branches (3-4 mm. thick), and (2) the
small utricles (500-650 long) (cf. figures 1-2 and 3-5, Plate 8). Further,
C. tomentosum does not assume a light green colour when growing in sunlight,
and it apparently reaches its maximum size during winter, at which season
C. mucronatum appears to be almost absent. The utricles moreover are often
thickened, but never mucronate. Both species are more or less tomentose,
but C. tomentoswum more often so than C. mucronatum.

C. mucronatum var. atlanticum var. nov. (Plates VII and VIII, figs. 3-5).

Plants robust, slightly branched, usually 6-9 inches high, rarely forming
large tufts 12-18 inches high, and much branched from below. Colour deep
green, bright green when growing in sunlight (due to the presence of bubbles
between utricles). Fronds robust, 5-7 mm. thick, entirely cylindrical (not
flattened below axils), dichotomous or dichotomously fastigiate, surface smooth
or slightly tomentose when young. Utricles very large, cylindrical or slightly
clavate, 800-1000u long by 250-300 wide, apex thin-walled, surmounted in
the younger parts of the frond by a small, sharp or blunt mucro, in the older
parts mucronate utricles often absent. Gametangia (@ ) large, 300-400 x
80-120n.

1 Var. atlanticum. Utriculi parte frondis adultiore laeves vel mucrono breyvissime acuto aut obtuso
instructi, parte juniore mucronati.

Clare Island Survey—Marine Algae. 15 115

Habitat—Sunny rock-pools, common; rocks near low-water or shallow

sub-littoral region, rare.

Season.—Spring to autumn. (Absent in winter ?)

Distribution —IkELAND, Co. Antrim (Giant’s Causeway), Co. Donegal
(Bundoran), Co. Mayo (Achill, Clare Island, Roonah Point, Old Head,
Bellacragher Bay), Co. Galway (Dog’s Bay), Co. Clare (Kilkee), Co.
Cork (Bantry Bay, one spec. in Herb. Univ. Cambridge).

SCOTLAND, Ayrshire (Ballantrae, Herb. Ball, Dublin), Bute (Cumbrae,
Herb. Batters), Orkney (Herb. Harvey, Holmes), Iona (Herb. Greville).
Iste or MAN (Port Erin, frequent in pools).
Ezsice.—C. elongatum, Ag., Holmes, “ Algae Rariores,” no. 282.
Distinguished from C. tomentosum by its more robust fronds, and the very
much larger utricles which are often mucronate. The degree of mucronation
is variable in different specimens, and also in different parts of the same
specimen. In some individuals it is marked throughout the entire plant, in
others in the younger parts only, whilst in a few cases it is absent except in
the tips of the branches and in proliferations. In the latter mucronation is
often very marked indeed.

The correct determination of this plant gives an additional species of
Codium to the continent of Europe. Entirely absent from England, and also,
as far as can be ascertained, from France and the Mediterranean, yet abundant
on parts of the west of Ireland and known to occur in the Isle of Man and
Scotland, it is to be regarded as one of the most interesting of the Clare Island
discoveries. Its distinet field-characters,and the fact that it is no recent
jntroduction, makes its previous non-recognition the more remarkable.

Before discussing the question of the Ivish plant, it may be well to refer
to C. mueronatum as generally understood. J. Agardh founded the species in
1886. He distinguished three varieties (with no definite typical form) as
follows :—

var. tasmanicum, Tasmania and Australia,
var. Novae Zelandiae, New Zealand.
var. californicum, California.

The characteristic feature of the species was the mucronate utricle ; and the
varieties were based on the degree and form of mucronation. In addition to
the countries mentioned, the plant has since been recorded from South Africa,
Japan, and Cape Horn, but not from the North Atlantic.’ There is a plentiful
supply in herbaria of both Australian and Californian material. An examination

1 The Japanese and South African specimens require verification.

P2

15 116 Proceedings of the Royal Irish Academy.

of the Kew specimens tends to support Agardh’s conclusion that all three
varieties belong to one species, and shows that in a general way mucronation
is correlated with robust habit and very large utricles (points not noted in
the original diagnosis). The Ivish plant does not agree exactly with any of
Agardh’s varieties. It resembles closely var. Novae Zelandiae, but differs in
the usually blunter mucro, and also in the occasional partial absence of this
structure.

Notes on the mucronation of the four varieties are given below, Agardh’s
description of the first three being amplified or slightly emended.

var. tasmanicum.—Utricles in youngest parts tapering to a long sharp
point; in older parts broad, cylindrical, sharply mucronate. Distribution—
E. and 8.E. Australia and Tasmania.

var. Novae Zelandiae.—Utricles surmounted with a small, sharp mucro, in
both young and old parts of the fronds, but usually slightly more marked in
the younger. Distribution—New Zealand and E. Australia.

var. californicum.—Utricles surmounted with a long or short mucro, which,
though sharp at first, is usually blunt later, and sometimes apparently
articulate. Mucro very variable in length, sometimes partially absent.
Distribution—Pacific Coast of N. America, (Japan ?)

var, atlanticum.-—Utricles in younger parts surmounted with a very short,
sharp or blunt mucro; in older parts utricles sometimes non-mucronate.
Distribution—N. and W. of Ireland, Isle of Man, 8.W. Scotland, Orkneys.

The above four varieties form an irregular series with regard to their
mucronation. Var. californicwm, although in some respects intermediate
between fasmanicum and Novae Zelandiae, is apart from both in the bluntness,
articulation, and occasional great length of the mucro.

Identification of the Irish Plant.—It is certainly remarkable that so
conspicuous a species should have so long escaped attention. Known from
Kilkee, and plentiful in the pools at Dog’s Bay, Roundstone, it is almost
incredible that such acute observers as Harvey and McCalla should not have
detected it. A single specimen collected in Bantry Bay by Miss Hutchins
(Cambridge University Herbarium), and two collected in 18359 from the
Ayrshire coast (Dublin National Museum), show that it is no recent
introduction,

The plant attracted attention on the first day spent on Clare Island,
and on one or two occasions only was there the slightest difficulty in
distinguishing it at a glance from C. tomentosum. Its light-green colour in
summer, and preference for shallow sunny pools, cannot fail to strike the
collector, whilst its sturdy habit is also noteworthy. With the exception of
the last, these characters are not of course visible in the dried specimen, and

Clare Island Survey—Marine Algae. 15 117

hence herbarium botanists have been off their guard, and have not detected
the microscopic characters which are even more striking and important.

Batters was the first to recognize the species as distinct. In 1897 he
received a specimen from Kilkee collected by E. George, and this he identified
with the Mediterranean C. elongatum. He did not apparently record the
discovery ; but in his “Catalogue” (1902) he lists ©. clongatum, and gives
Kilkee as the only locality. On my return to London after the first Survey
visit, [examined Batters’ specimen. In external form it agreed fairly well
with small specimens of C. elongatum, and possessed large utricles, as does
that species. The Clare Island gatherings differed somewhat; but it was
established beyond question that the two plants were specifically identical.
As there was no other European Codium to which the species could be
referred, the name C. clongatwm was accepted, though each subsequent visit
rendered the identification more questionable. Occasional mucronation was
noted; but this was regarded as an irregularity.

During the second season the matter was thoroughly investigated, and
herbarium material of all known species of Codium was examined. As a
result, the Irish plant was found to be constantly more or less mucronate,
and to resemble very closely the Australian plant C. mucronatum J. Ag. As
the position of this species in Europe would-be extremely isolated, and since
the Irish plant was decidedly less mucronate than the Australian, it was at
first thought advisable to describe it asa new species. But on further investi-
gation it was found that, as far as could be ascertaimed from dried material,
it differed in no important particular from Agardh’s species, the Australian
gatherings varying largely amongst themselves as to degree of mucronation.
Further, the Ivish plant differed much less trom var. Vovae Zelandiae than does
that plant from var. tasmanicum, whilst the Californian variety is far and
away more distinct. On the other hand, it was undesirable, in the present state
of our knowledge, to definitely link the European plant with var. Novae
Zelandiae. I have therefore described it as a new variety, which may be
distinguished from the last-named by the small size of the mucro, and by its
partial absence in some cases,

The drawing on Plate VII shows its robust habit,! and on Plate VIII the
form and size of the utricles are depicted. ‘Though mucronation may at times
be absent, the greater length of the utricles, and the absence of apical
thickening, render these structures perfectly distinct from those of
C. tomentosum (cf, figs. 1-2 and 3-5).

‘Unless the specimen be carefully dried, the stout character of the branches may be lost, as ia the
case in many herbarium specimens. On the other hand, it is possible by excessive pressure to
give specimens of C. tomentosum the appearance of C. mucronatum.

15 118 Proceedings of the Royal Irish Academy.

Biology and Ecology—The bright green colour referred to is an optical
effect due to the presence of air-bubbles between the utricles. Two explanations
suggest themselves: (1) A physiological disturbance in the tissues due to the
heating of the pools, and (2) the retention of oxygen given off during
photosynthesis in bright sunlight. Plants growing in the shade are dark in
colour, as were those collected in February. But in April, when there is
sufficient sunlight to cause heating and rapid photosynthesis, the bright green
appearance is, on the south shore of Clare Island, everywhere in evidence. At
the Giant's Causeway, however, where the coast faces north, a few plants
collected on May 1 were still dark. It is noteworthy that when ©. tomentoswm
grows in sunny pools, which is very rarely the case, no gas is found between
the utricles, and the normal colour is retained.

The habitat of our plant is well marked. It is distinctly an alga of sunny
rock-pools, being found at any level, but more commonly at a quarter to three-
quarter tide. It also occurs occasionally in the shallow sub-littoral region, or
on bare rocks near low-water mark, where, though liable to be exposed to the
air during the lowest tides, it may attain a large size. In this position it is dark
in colour. In a general way the plant is frequent on the south shore of Clare
Island; also at Roonah and Dog’s Bay. It prefers moderately open rocky
ground, but extends into Clew Bay as far as Old Head. Several plants were
noted in the quiet, brackish waters of Bellacragher Bay; but they were
decidedly unhealthy, the fronds being not only irregular in form, but
exhibiting abnormalities in microscopic structure. The utricles were for the
most part strongly mucronate, and showed a tendency to become irregularly
thickened at the apex.

C. mucronatum var. atlanticum appears to be an annual. On the February
visit young plants only were observed, and large plants are prevalent in
summer, though a few sporelings may be found all the year round.
C’. tomentosum, on the other hand, attains its maximum size in winter.

Distribution.—The remarkable feature with regard to distribution is not so
much its link with the Australian forms (our other species, C. tomentosum and
C. adhagrens, apparently occur in the Southern Hemisphere), but its isolated
position in Europe. It is not known from the Mediterranean or from North
Africa, and is apparently entirely absent from the remainder of the North
Atlantic. Dr. Marshal Howe, who has collected largely on the American
coasts and in the West Indies, writes in reply to an inquiry, that as far as
he is aware “no mucronate Codium has ever been found on the Atlantic
coast of North or South America, or on any of the outlying islands.”

The distribution in the British Isles is given on p. 115. No English or
French specimens have been found in any of the herbaria examined ; neither

Clare Island Survey— Marine Algae. 15 119

have friends in England or Wales, to whom I have written, been able to detect
it on the shore. Professor Harvey Gibson kindly sent a plentiful supply from
the Isle of Man; and stated that the plant is frequent in the pools at Port
Erin (Bradda Head), but was not noted elsewhere. Judging from certain
statements in his memoir (00), it was probably established there in 1900.
The herbaria examined were as follows:—Kew, British Museum (including
Herb. Batters), Trinity College, Dublin (including Herb. Harvey), National
Museum, Dublin; Birmingham University (Herb. Holmes), and Cambridge
University ; Edinburgh University (including Herb. Greville).

Phoeococcus adnatus West, comb. nov.

(Gloeocystis adnata Nag., Batters Cat., p. 9).

Owing to the difficulty in ascertaining the correct group to which it
belonged, this alga caused considerable trouble, and was ultimately
determined by Professor G. S. West. The plant was imperfectly described
by Cooke and Rabenhorst under the name of Gloeocystis adnata Nag., and was
listed thus by Batters (l.c.). It is recorded from four localities in England ; and
was added to the Irish flora during the Lambay Survey. In Clew Bay it is
common, forming a definite zone of dull-yellow colour on the vertical peat-
banks (p. 82). Professor West informs me that the species certainly belongs to
the Phoeophyceae, and should be removed from Gloeocystis to Phoeococeus ;
also that he hopes to publish shortly an account of the genus, and will
include observations on the minute structure of the present species.

Phoeostroma pustulatum Kuck.

The alga here referred to is the plant not uncommon on the tips of
Laminaria saccharina var. Phyllitis, and which was identified as P. pustulatwm
by Batters (Journ. Bot., xxxiii, p. 275). It appears to differ slightly from
Kuckuck’s plant; and further investigation may show that it should be
separated as a distinct species.

Litosiphon pusillus Harv.

Abundant on Chorda, Zostera, and not uncommon on other algae.
Occasionally it is found on rock amongst such species as Rhodochorton
floridulum.

Stictyosiphon adriaticus Kiitz.

A few specimens of this species, which is new to British flora, were
dredged in Clew Bay (in 3 fathoms) during May,1911. They were noted as
unfamiliar on dredging, and were ultimately referred to Ajel/mania sorifera
Reinke. Dr, Kuckuck, to whom a fragment was sent, confirmed the

15 120 Proceedings of the Royal Irish Academy.

identification ; but tells me that Reinke’s plant is synonymous with Stictyosiphon
adriaticus. The branches in the latter alga, though usually regarded as
opposite, are frequently alternate. The distribution of S. adriaticus is
therefore much wider than was formerly thought, the plant being known not
only from the Mediterranean, but from Kiel (Reinke), Cherbourg (Kuckuck,
1904, in litt.), and Clew Bay (1911).

Dichosporangium Chordariae Wollny.
(Hedwigia, xxv, 1886, pp. 127-1380, tab. I, figs. 1-5, tab. 11, fig. 3.)

Though not previously detected in the British Isles, this minute endophyte
is probably frequent in the old fronds of Chordaria flagelliformis, as it is in
Heligoland. The Clare Island specimens were found in October, 1910, in
fronds that were also infested with Bulbocoleon. The plant is not related to
the original species of Dichosporangium (i.e. D. repens = Myriotrichia repens
Kuck.) ; and there appears to be no reason why it should not be placed in
Streblonema.

Sphacelaria britannica Sauv.

Professor Sauvageau, who kindly looked over the material of Sphacelaria,
confirms the determination of this species, which is not uncommon on
boulders in caves and in similar shady spots. ‘The plant was added to the list
of Trish algae by Batters, who found it at Lambay.

8. cirrhosa Ag.

Exceedingly common in our area, extending from the shallow-littora]
region, through the littoral, and up to the highest rock-pools. It is usually
epiphytic; but on semi-sheltered shores it forms an element in the sand-
association of the Rhodochorton floridulum. In this condition it has often

been mistaken in the past for S. radicans.

S. plumula Zan.

New to Ireland. A few specimens of this were dredged in 4 to 5 fathoms
in Clew Bay and at Roundstone.

MYRIONEMACEAE.

The Myrionemaceae, as presented in our algological works, are in great
confusion, but it is hoped that the monograph, shortly to be published, will
bring about a measure of order. In the present report some of the results
are forestalled, alterations in nomenclature being made when necessary, and
an explanation given. ;

Clare Island Survey—Marine Algae. 15 121

Myrionema saxicolum Kuck.

Some very beautiful specimens of this rare plant were found on limpet-
shells on Clare Island in October, 1910. The sporangia and filaments were
slightly larger than in the Heligoland material, but Dr. Kuckuck tells me it
is undoubtedly the same species.

M. reptans Fosl.

(= Ectocarpus reptans Crouan; Ascocyclus reptans Reinke ; Phycocelis reptans
Kjellm.; Chilionema reptans Sauv.; Hecatonema reptuns Sauv.; Hecatonema
fucicola, Kylin).

Though no one has thrown more light on the Myrionemaceae than
Professor Sauvageau, a few alterations with regard to his “ Mémoire” have
been found necessary. The present plant proves to be a Myrionema, and not
a Chilionema ; hence Foslie’s name is restored. It is frequent in the south
of England on Fucus spp., but is apparently rare in Co. Mayo, having been
searched for on many occasions, but found once only.

Ulonema rhizophorum Fosl.

It is most probable that Ulonema is merely a form of Jf. strangulans
oceurring on Dumontia, but some curious stages occasionally found make one
hesitate to reduce it till the point has been more thoroughly investigated.

Hecatonema reptans Kylin (= Eetocarpus reptans Kjellm., non Crouan) ;
Streblonema veptans De Toni).

The full synonymy of this species and JZ, reptans will be given in the
Monograph. Suffice it to say here that I have examined Kjellman’s type, and
there is no doubt that it should be placed in Hecatonema. It is not
uncommon in our district on Cladophora sericea and C. rupestris.

H. speciosum Cotton, comb. nov. (= Myrionema speciosum Borg.; Heeatonema
diffusum WKylin).

The type-specimens of both these plants have been examined ; and it is
quite clear that H. diffuswm Kylin is an early stage of Borgesen’s MW. speciosum.
Hecatonema is, however, the most suitable genus. The plant is common in
the British Isles, especially in spring, and was noted frequently in Clare
Island on a variety of plants during both the April trips.

Microspongium globosum Reinke (= Myrionema globoswm Fosl.; Hecatonema
globosum Batters).

A difficult species to place; but when well grown it is evident that it is
most suitably located in the genus Microspongium.

B.J.A. PROC., VOL. XXXI. Q 15

15 122 Proceedings of the Royal Irish Academy.

Ascocychus foecundus Cotton, comb. nov. (= Phycocelis foecwnda Strom. ;
A. sphaerophorus Sauy.; A. islandicus Jons.).

Phycocelis foecunda has long baffled algologists. The type-specimen shows
that it is an Ascocyclus, and identical with the plant so well described by
Sauvageau as A. sphaerophorus, The number of ascocysts varies greatly in
different specimens; but, as Stromfelt’s name suggests, the sporangia are
yery numerous. Common on Rhodymenia palmata.

A. Saccharinae sp. nov.’ (Plate X, figs. 4-9). A. afinis Cotton, 07, non Sved.

Plants forming dark brown circular spots 1-2 mm. diam., rarely 3-4mm.
Discoid thallus monostromatic or partly diplostromatic, 8-14 4 thick, not
parenchymatous in centre; margin rather irregular; radiating filaments
regular, 7-8 » wide, by 1-2 times as long; chromatophores 4-6. Hairs
numerous, basal; sheath well developed; adult cells 60-80 x 7-8y.
Assimilating filaments few or absent, simple, cylindrical, 70-120 » long, thin-
walled ; cells, 7-9 « wide by 1-2 times as long. Ascocysts usually abundant,
appearing very early on conspicuous wide margin of basal thallus, sessile,
rarely stalked, thick-walled towards the base, typically clavate, 30-40 x 9-10
(on young plant sometimes globose, 15 x 20 x 10-14). Unilocular sporangia
unknown. Plurilocular sporangia very abundant, sessile, subsessile, or stalked,
lanceolate or elliptic-oblong, rather small, 30-40 x 10 » (on old plants
30-55 x 10-12 x), 1-2 seriate; locali 4-6 » high.

Habitat.—On Laminaria saccharina.

Fruiting Season.—Early spring till late autumn.

Distribution.—England (Swanage, Weymouth, Plymouth), Ireland (Clare
Island).

This species, hitherto undescribed, is not uncommon on the south coast of
England, and was found more than once on Clare Island. It occurs on young
plants of Z. saccharina, usually on the decaying tips of the fronds, where it
forms dark-brown spots often intermixed with Myrionema Corunnae. It may,
however, also occur on older fronds, in which case it is usually larger and
often presents irregularities in microscopic structure.

The species most closely resembles A. foecundus, but it differs in the
typically clavate ascocysts, although in young plants there is a tendency for
these bodies to be subglobose. The spots formed are not so large, and the

! Maculae minutae, fuscae 1-2 (raro —4) mm. diam. Discus unistratosus vel partim duostratosus,
cellulis cirea 12-16 x 6-8 u, organa verticalia emittens (1) pilos numerosos, ce!lulis 60 x 80 x 7-8 u,
(2) fila assimilantia rara, breva, 7-9 » lata, chromatophoris 4—6, minutis (3) sporangia plurilocularia
numerosissima, sessilia vel breyiter aut interdum longius pedicellata, elliptico-oblongata, 1—2 seriata,
plerumque 30-40 x 104.

Clare Island Survey—Marine Algae. 15 123

plant is usually smaller in all its parts, especially in the basal thallus. It
is, moreover, apparently to be found throughout the entire year, whereas
A. foeeundus has a much shorter season.

Ralfsia verrucosa Aresch.

Very common in many parts of our district. In shallow rock-pools on
the upper part of the shore it forms large spreading sheets, which may com-
pletely cover the bottom. At a lower level it usually occurs on bare rock.
Occasionally it was dredged from the shallow sub-littoral region.

Lithoderma faticens Aresch. ,

It is disappointing not to be able to record this plant (a species supposed
to be widely distributed) with certainty for Ireland. Many Lithoderma-
like plants were dredged in Clew Bay during summer, but these, as was
expected, proved sterile. The special February trip provided a large number
of specimens, some of which Dr. Kuckuck informs me can be doubtfully
referred to Lithoderma. A few of the specimens obtained proved to be Petro-
derma maculiforme, which shows the risk of naming these plants from
imperfect material.

Petroderma maculiforme Kuck.

A few specimens of this species (which is an addition to the British flora)
were detected by Dr. Kuckuck amongst material dredged in Clew Bay
during February. The plant resembles Lithoderma very closely in external
appearance, but differs in the character of sporangia and other minor points.

Spermatochnus paradoxus Kitz.

Extremely abundant during July and August in the low-littoral of Achill
Sound, Bellacragher Bay, and in the inner part of Clew Bay. It is epiphytic
on many of the larger algae, and forms large tangled masses a yard or more
square: in some of the channels of Achill Sound it is for a time com-
pletely dominant. In contrast to the present species Stilophora rhizodes is
comparatively rare.

Mesogloia lanosa Crn.

Several plants of this rare alga were dredged near the lighthouse in Clew
Bay during July, 1909. Its season is probably short, as it was not met with
in any subsequent dredgings,

M. Griffithsiana Grev.

It was very satisfactory to find during the last days of the field-work the
true IL, Grifithsiania, since the specimens collected as this species in 1910

Q2

15 124 Proceedings of the Royal Irish Academy.

proved to be Acrothrix mirabilis, The plants are indistinguishable in the
field, but with microscope the greater length of the peripheral filaments of
the present plant are at once noticeable. Found floating near Achill Bridge
and at Old Head, September, 1911.

Acrothrix mirabilis Kylin (07, p. 93).

The specimens on microscopic examination were at first determined as
Mesogloia neglecta Batters, with which they agree closely; butDr. Kuckuck
informs me that they are identical with A. mirabilis Kylin, authentic
material of which he has seen. Kylin’s genus is based on a good character,
and should be maintained; but if the two plants are synonymous, Batters’
specific name should be employed, as he first detected and published the
species (Journ. Bot., 1906, p. 2). A difficulty, however, presents itself, since
the type of M. neglecta cannot be found in the Batters collection, and hence it
is impossible to re-examine the points in which the Clew Bay material differs
from the description. The discrepancies are trivial, but until we are certain
that all the Mesogloiae of our shores are known, it seems wiser to let AZ, neglecta
stand as a separate species, and not to link it with A. mirabilis.

The present plant bears a striking resemblance to MZ. Grifithsiana, and
Was assumed to be such on collecting. It is remarkable also that it was found
in practically the same localities. Four plants in all were taken, two at Old
Head and two at Achill Sound, July, 1910.

Leathesia crispa Harv.
A few specimens of LZ. crispa were collected during the first trip to Clare
Island, but on no subsequent visit. In Journ. Bot., xlvi, p. 329, I have
dealt with the synonymy and distribution of this species.

Fucus ceranoides L.

Invariably present where fresh-water streams occur on sheltered shores.
(See pp. 83-88.)
F. spiralis L.

For remarks on the various forms assumed by this species see Fucaceae
associations (pp. 25 and 51). One variety, however, requires special notice.

Var. nanus Stackh.—In many spots in Achill Sound, the sheltered form
of var. nanusis found growing on vertical peat-banks at high-water mark.
An unbroken series may at times be traced from the normal form. The
plants measure 1-4 inches in length, are slightly (1-3 times) branched, and
fruit freely at the proper season. In many of the receptacles examined
the oogonia were unripe (May); but they appeared to be perfectly healthy

Clare Island Survey—Marine Algae. 15 125

and not abortive. Occasionally specimens only 1 inch high were observed
in fruit. In channels on the salt-marsh, the same plant occurs; but it is
not so easily traceable to the normal /. spiralis, and is liable to be confused
with F. vesiculosus var. balticus. It may be distinguished from that plant by
its sightly wider, regularly bifureating fronds, over which the cryptostomata
are evenly distributed, and by its scattered habit. The fronds, moreover,
are always fertile in summer: and their hermaphrodite conceptacles, with
projecting paraphyses, are very marked.

F. lutarivs Kiitz., which has lately been described with great care by
Sauvageau (08), agrees with /. spiralis im possessing projecting paraphyses
—a character which strongly suggests that it may be a reduced salt-marsh
form of that species. In F/. /utarius the conceptacles do not reach maturity,
and the eryptostomata are marginal. A difference in form, together with an
abundance of proliferating branches, is also noticeable; but this may be
eaused by its peculiar habitat (mud-banks). Proliferating specimens of
F. spiralis var. nonus were frequently noted at Mulranny.

F. vesiculosus L.

See notes on Fucaceae association (pp. 25 and 51).

Var. evesiculosus, auct—To var. evesiculosus auct. I refer the short non-
vesicled form of F. vesiculosus which is abundant on Clare Island. The name
is not altogether satisfactory ; but till the British Fuci have been studied and
described in greater detail, it appears the most suitable. The plant is
abundant on, and characteristic of, exposed coasts in west Ireland, and also
in south England. It is found likewise in the north of France, and is
probably similar to that recorded by Sauvageau, under the above name,
from north Spain (97). A non-vesicled form of F&. vesiculosus is described
by Kylin for the exposed shores of west Sweden; but this variety, which he
identifies as compressus racemosus Kjellm., is, judging from specimens kindly
sent by him, a decidedly longer plant, of a much less sturdy habit.

Var. balticus J. Ag.—To this plant I have referred a dwarf Fucus
tolerably abundant in Clew Bay, which is intermediate in size between
F, vesiculosus var. volubilis (Huds.) and the very dwarf form described
below as var. muscoides.

Great confusion exists with regard to the identity and nomenclature
of these forms. The paper just published by Miss Baker (712) clears
up the uncertainty as to Ff volubilis Huds. The many different forms
assumed by this plant on the salt-marshes of Essex and Norfolk are described
and illustrated; and I am indebted to Miss Baker for notes on the differences

15 126 Proceedings of the Royal Irish Academy.

between the Clew Bay and the East Anglian forms.! The specimens collected
by Ray at Chichester and referred to by Hudson in his original description
of F. volubilis (Fl. Angl., ii., 1778) are unknown; but there can be no doubt
that Miss Baker is correct in referring the twisted plant described by her
from Mersea Island and Blakeney to the Fucus volubilis of Goodenough
and Woodward (1797), and of Turner (“Synopsis,” 1802), who cite it from
Frambridge Ferry and Wells, respectively—localities in the immediate
neighbourhood of those she has investigated. Several Frambridge Ferry
specimens exist, moreover, in the British Museum.

The smaller forms of this same plant, M volubilis Hudson, have, on
the other hand, often been referred to F. vesiculosus var. balticus. At Mersea
Island, the dwarf forms are clearly linked by intermediates with the large
twisted forms; but in Clew Bay it is otherwise, large plants being entirely
absent. This being the case, I have thought it best to use the name balticus,
which has already been employed for the Irish plant (Harvey, Johnson,
Batters). At the same time the whole question of F. balticus requires
investigation, as it is highly probable that more than one plant is included
under that name. Svedelius (01) shows that several dwarf Fuci occur in
the Swedish Baltic, all of which he regards as varieties of F. vesiculosus,
Before, therefore, the identity of our British plants can be settled, a careful
examination of Agardh’s plants and fresh gatherings if possible from the
original locality are required. When the dwarf forms are not connected by
intermediates with normal plants, there is great difficulty in ascertaining
from which species they are derived. The distribution. of the cryptostomata
and the nature of the receptacles (if present) give the most hopeful clues,
whilst a careful study of the ecology of the plants should aid the elucidation.

In Clew Bay var. balticus is usually found on the sides of narrow channels
and creeks on flat peaty areas. The flat surface of these areas is commonly
carpeted with var. muscoides, which grows densely crowded together, and is
of a short bushy habit. At the margins where there is more space, the plants
are longer and hang down. These marginal forms I refer to var. balticus.
The fronds are narrow, 3-4 inches long, slightly or not at all twisted, and
with cryptostomata for the most part marginal. They usually lie in the
channels, and are thus in contrast to the upright-growing muscoides. The
receptacles are small, seldom measuring more than 8 x 5mm. and often
less; they are dioecious, not markedly mucilaginous, with non-projecting
paraphyses. Male receptacles are more frequent than female, but both are

i F. volubdilis is, without question, a curious salt-marsh variety of 7. vesiculosus ; and when the
systematic aspect of the British Fucaceae is next dealt with, it will have to be placed under that
species.

Clare Island Survey—Marine Algae. 15 127

rare; the oogonia appear to develop normally. The largest specimens of
yar. balticus noted were found on a little piece of wet marsh at Leenane
(growing here on the flat as well as the vertical banks)—a fact which gives
support to the view that soft ground and a large amount of moisture favour
its development.

From the above it will be seen that the var. balticus of Clew Bay
approaches very closely to the smallest forms of var. volubilis as described by
Baker. At Mersea Island, however, receptacles are only found on the large
plants ; and the fronds are always much twisted. At Blakeney small plants
fruit; but the receptacles are much larger than in the Irish specimens. In
both these localities there is much mud ; and the plants are free, or more or
less imbedded. In Clew Bay the substratum consists of firm peat, and mud
is absent.

Var. muscoides, var. noy.,! Plate VI, figs. 1 and 2.—Plants very short,
fastigiately branched, densely crowded together, 5-6 cm. long. Branches
cylindrical or compressed, 1-3mm. wide, not twisted, with marginal
eryptostomata. Receptacles very scarce, minute, 2-4 mm. diam., dioecious,
paraphyses not projecting. e

Habitat.—On firm peat, near extreme high-water mark.

With some reluctance I describe this Fucus as a new variety of
F. vesiculosus. It approaches in form some of the Baltic filiform varieties of
this species; but it differs in its peculiar habitat,and appears to be worthy of
a special name. At the same time, though the evidence points to its being a
variety of F. vesiculosus, the fact is not proved. By giving it pro tem. specific
rank, complications in the future are less liable to occur; but this would
necessitate the record of an additional new species in the list of novelties;
whereas the plant is almost certainly merely a remarkable variety of an
already known plant.

As previously stated, var. muscoides is connected with the Clew Bay form
of var. balticus, of which it may be regarded as a very dwarf upright-growing
form with filiform branches. The plants are packed very closely together,
and form a dense mossy carpet, a feature which serves to distinguish the
present variety from the filiform plants found in the Baltic. In a general
way, the more closely packed the plants are, the smaller and more terete the
fronds. The cryptostomata are conspicuous, and are, of necessity, marginal,
The fastigiate branching is characteristic; but the branches are often very
irregularly produced, and a crop of lateral proliferations is not infrequent.

1 Frondes perpusillae, dense caespitosae, filiformae vel compressae, 5-6 cm. longae, 1-3 mm. latae,
eryptostomatibus conspicuis, receptaculis rarissimis, minutis, ovyoideis 2-4 mm. latis. Ad terram
turfosam.

15 128 Proceedings of the Royal Irish Academy.

Receptacles are only known in the wider forms of the plant; they are
unisexual, and apparently normal even in the smallest examples. ripe
antheridia being noted in a receptacle only 2x2 mm.

The chief reasons for regarding var. muscoides as a form of F' vesiculosus,
are the unisexual conceptacles and the fact that it is clearly linked with var,
balticus. It is true the specific identity of the latter is not quite certain ;
but the nature of its conceptacles precludes the possibility of its being a form
of F. spiralis, The only other species with which var, balticus or var. muscoides
could be connected is F. ceranoides, but as seen growing there is nothing
suggestive of any link with the dwarf forms of that plant. A hybrid origin is
possible, but scarcely probable, since var. muscoides occurs in profusion where
F. ceranoides is completely absent. The principal objection to its being a
variety of F. vesiculosus is its elevation on the shore (above F. spiralis and
Pelvetia) ; but this, as pointed out in the ecological section, can be explained
by the high water-content of the substratum.

Ascophyllum nodosum var. Mackaii, comb. nov.

From the historical standpoint this is one of the most interesting of the -
Irish seaweeds. It was first described from the Roundstone neighbourhood
by Dawson Turner in 1808 (“ Hist. Fue.,” Pl. 52), and is the earliest algal
record from that well-known locality. It still occurs in profusion at Round-
stone, being found in September, 1911, between the bridge and Ballinahinch.
The plant cannot be certified from any other station in Ireland, and, with the
exception of a few localities in W. Scotland, it is unknown elsewhere in the
British Isles. Turner’s remarks will, therefore, be of interest. He states: —

‘For the present very interesting addition to the Catalogue of British Fuci
we are indebted to Mr. James Townsend Mackay, to whom I am also obliged for
the specimen here figured, and by whose name I have ventured to call it, as I find
no description of it in any preceding author, in memory of the services that he has
rendered to the botany of these islands, particularly by his discoveries in Ireland, the
south-west districts of which, a part hitherto least known to naturalists, he has more
than once, under the auspices of Dr. Scott, explored with extraordinary zeal and
success. It was in one of these excursions, in the summer of 1805, that he met
with the plant here figured, in a small creek at the upper end of Birtebui Bay,
near the hill of Cahil, Cunnamara, but nowhere else. He informs me that he
could not find a single specimen attached to the rocks, but it was all lying in loose
balls upon the shore, and in such quantity as to entirely cover that part of the
strand upon which it was thrown. With it was F. nodosus, which, though
produced in great abundance upon rocks in the neighbourhood, seemed to exist at
that place only in a similar manner, without being fixed to anything ; both of

Clare Island Survey— Marine Algae. 15 129

them being rolled up as if by the action of the waves, and in that state apparently
continued to grow, and throwing out from the root, which was in the centre, a
prodigious number of shoots in all directions, so as to give the thick and bushy
appearance above described.”

There can be no doubt that the present plant is merely a variety of
A, nodosum, and is comparable to the peculiar detached forms of Fucus and
Pelvetia which occur in other localities. (See Baker, 12, p. 283, and Oliver in
Tansley, 11, p. 364.) Whether it originates in the manner described below
for var. sconpioides I was unable to decide, but it appears highly probable. No
intermediates between the detached form and the normal 4. nodosum were
found, but there was an evident link with var. scorpioides, and certain specimens
were difficult to place. It is possible that the variety Mackati arises only at
certain seasons of the year, in which case a prolonged stay in the locality
might be necessary in order to discover its origin.

The plants lie as loose densely branched tufts (up toa square vend in area)
on the flat sandy mud between patches of rock, and when the tide returns
they do not float, but become perfectly submerged. They appear to be seldom
disturbed by wave-action. Air-bladders are numerous, but very small. A
few tufts of Polysiphonia fastigiata were noted on some specimens, and also
on var. scorpioides; but on the whole this epiphyte was absent. Many quiet
land-locked areas exist in Achill Sound and Bellacragher Bay; but no
examples of var. Mackaii were found, so that the Roundstone locality still
remains the only positive station in Ireland for the plant.'

Although C. Agardh, as early as 1824, reduced Fucus Mackaw to a variety
of F. nodosus, no one appears to have used the combination employed in the
present report. Of late years there has been a tendency to follow Harvey,
who regarded it as a distinct species. Holmes and Batters (90) removed the
plant to Ascophyllum; and their name, A. Mackawi, has since come into
general use. ;

Var. scorpioides Hauck.—A few plants of this curious variety occurred in
some muddy areas in the inner part of Roundstone Bay intermixed with var,
Mackaii. They were more or less imbedded in the mud, and formed much
smaller tufts than the latter. Reinke’s explanation as to the origin of this
form in the brackish waters of the Baltic Sea is as follows :—Isolated floating
pieces of A. nodosum are washed in by currents from the more open Skagerack,
and come to rest in the quiet creeks, where they put forth numerous small
adventitious branches from the marginal cryptostomata of the thallus.

1 Miss Knowles kindly informs me that specimens labelled A. Mackaii, collected in Larne and
Belfast Loughs by D. Moore and J. Doran respectively, exist in the Dublin: Museum. There is,
however, some uncertainty as to both specimens, and though the districts have been fairly carefully
worked, other observers have not noted the plant.

BIA. PROC,, VOL, ¥XXI, R 18

15 130 Proceedings of the Royal Irish Academy.

Through the growing out of such branches and the decay of the old fronds,
- colonies of young plants arise, which lack a discoid base, the latter being only
produced by sporeling plants. The cylindrical form of the branches, the
absence of air-bladders, and the complete sterility are induced, according to
Reinke, by the low salt-content of the water; and he suggests that in less
brackish localities such floating shoots of A. nodosum might give rise to
A, Mackati. (See Reinke, ’89 and '92.)

Bifurcaria tuberculata Stackh.

It appears probable that the Roundstone neighbourhood is the northern
limit in the British Isles for this species. It occurs on the coast of southern
England, and is known in Ireland from the counties of Cork, Clare, and
Galway, being abundant in the last-named at Dog’s Bay. The pools of Clare
Island, and the more open parts of Clew Bay, which are eminently suited
for it, were carefully worked, yet not a single plant was observed.

Taonia atomaria J. Ag.

Dredged in Clew Bay, and washed ashore between Old Head and
Leckanvy(1909, ’10,’11). Frequent on the west coast and known as far north as
Bundoran (Johnson); on the east coast it has been collected at Wicklow
(Harvey).

Dictyopteris membranacea Batt. (= Haliseris polypodioides Ag.).

In contrast to Bifurcaria, an extension of distribution can be recorded for
this southern species, Roundstone Bay having hitherto been its northern
limit. Several specimens were dredged in Clew Bay by Mr. J. Adams, in
August, 1909; but the plant was not seen again during the Survey. The
specimens were large and strong; and the species is evidently quite at home
as far north as Co. Mayo.

Erythrotrichia Bertholdii Batters.
Useful notes on the genus Erythrotrichia will be found in the paper by
Batters, in which this species is described (00, p. 374). The cylindrical
filaments resemble those of Z. ciliaris (Carm.) Batt. (non Thur.) ; but the plant

is distinguished from that species by the absence of a basal disk.
Achill Sound, October, 1910, on old Zostera leaves.

E. investiens Born.

With slight hesitation T have referred a few odd filaments found at Old
Head to this little-known species. The plants fit no other species of: the

Clare Island Survey —Mar ine Algae. 15 131

genus, and agree well with the description given by Zanardini. The filaments
are bright rose in colour, rather thick (25-35 when sterile), and unbranched.
There is no true basal disk; but a few horizontal cells are developed at
the base, and the filaments occur in tufts, as shown in Zanardini’s figure ;
lateral mamillose protuberances as described by him are also present. The
specimens were found on Fucus (possibly attached to it), and agree well with
Haucke and Richter’s Exsice., No. 655 (also on Fucus), which Batters suggests
should be referred to #. investiens rather than £, ciliaris (00, p. 374).

E. Welwitschii Batters.

This little-known and apparently very distinct species was found on limpet-
shells encrusted with Ral/sia verrucosa near low-water mark, in October, 1910.
The plant was originally described by Ruprecht as Cruoria (?) Welwitschi, and
the same specimens were later referred to by J. Agardh as Callithamnion
lepadicola. Batters ('02) removed the plant to its right genus, and made the
new combination Hrythrotrichia Welwitschit. A portion of the Lisbon
gathering, collected by Welwitsch, exists at Kew, with which the Clare Island
specimens agree well.

The species appears to be confined to the thalli of Ralfsiae, and is worthy
of further study. Hitherto it has been recorded in the British Isles from
Swanage only; but it is probably widely distributed. When wet it is
inconspicuous ; but when the limpet-shells are becoming nearly dry, it shows
as a pale-pink felt.

Porphyra coccinea J. Ag.

Somewhat rare, and not previously recorded for Ireland. I noted it,
however, in Co. Antrim in May, 1910; and a specimen collected by Miss
Hutchins, from Bantry Bay, was found unnamed in the Kew collections.

P. umbilicalis Kiitz.

Var. umbilicalis J. Ag—The exposed Porphyra association, described on
p- 28, consists entirely of this form.

Var. laciniata Thur.—Abundant throughout the area, being saxicolous or
epiphytic, and occurring in the littoral and upper sub-littoral regions, and
also in pools. It is the variety which forms the Porphyra association of
sheltered localities.

Var. linearis Harv. (=P. linearis Grey. in Batters 02, p. 56; see
Kosenvinge, 09, p. 61).—Unless the growth of the plants be watched from
month to month, P. linearis Grev. would never be taken to be the same
species as P, wmbilicalis Kiitz., especially as sporelings of the latter often

R 2

15 132 Proceedings of the Royal Trish Academy.

develop directly into broad frondose thalli. I fully agree, however, with
Thuret and with Rosenvinge, who regard P. /inearis as a young and winter
form of P. wmbilicalis. Observations made at Swanage, though not so
extensive as those of Rosenvinge, led to that conclusion. On exposed coasts
a very large proportion of the growth does not survive the spring. On the
more sheltered shores of Clew Bay the plant doubtless develops, as it does at
Swanage, into var. /aciniata, A typical band of P. linearis was, however, only
observed on the exposed parts of the Clare Island district.

CHANTRANSIA.

The species of this genus have been very erroneously named in the past;
and it is highly satisfactory to have had the Survey material named by
Dr. Rosenvinge. The following account is derived from his report :—

The epiphytic covering of Chantransia, which is conspicuous on many
algae on Clare Island, appears to consist almost entirely of various varieties
of C. virgatula. In sheltered localities (e.g. Clew Bay and Achill Sound)
the same species is abundant; and C. Thuretii also is exceedingly common.
It will be noted that in his work on the Danish species (’09) Rosenvinge
places C. secundata and C. lucurians (which are given specific rank by Batters
(‘02)) as varieties of C. virgatula.

C. virgatula Thur.

Var. luxurians (J. Ag.) Rosenv.—Common and very conspicuous on
Ceramium spp. in rock-pools at Kinnacorra and Portlea (Clare Island), On
the mainland it was found on Gracilaria and Zostera dredged in shallow
water. New to Ireland.

Var. tetrica Rosenvy.—This variety, which is also new to Ireland, occurred
on Codium tomentosum on Clare Island, and on Gracilaria at Old Head. It is
distinguished by the presence of tetraspores on short opposite branches.

Var. secundata (Lyngb.) Rosenv.—Exceedingly abundant in all parts of
the Survey area. On Clare Island it is the form which gives the pink colour
to the growth of Porphyra on exposed rocks; and it is also found on the
Rhodymenia and the Laurencia pinnatifida communities. The plant moreover
covers Codium and Ceramium spp. in pools, and can endure a certain amount
of fresh water, being found in the spray of the waterfall at Portlea. On the
sheltered mainland it is common on many algae, both in the littoral and
sub-littoral regions. i

C. Thuretii (Born.) Kylin.

Though a new record for the British Isles, this species is common in

Britain, and has doubtless been passed over as (. Daviesii. It is distinguished

Clare Island Survey—Marine Algae. 15 133

from that plant by its more slender filaments, which are composed of very
long cells, and by the occasional occurrence of: sexual reproduction; but
Rosenvinge remarks that he is not yet certain if the two are sufficiently
distinct to be kept apart. C. Thuretii appears to be a species of quiet waters,
being abundant in Clew Bay and Achill Sound, but only collected once on
Clare Island and then in pools at Portlea. It is especially plentiful on Zostera,
and is most conspicuous in late summer.

C. endozoica Darb.

A species of Aleyonidium washed ashore at Old Head was infected with a
Chantransia apparently referable to this species. Dr. Rosenvinge writes that
the parts are smaller, and that the fertile branches are less branched than in
Darbishire’s plant.

C. Alariae Jons.

Noted on several occasions on old fronds of Alaria which had been washed

ashore, It extends at times over a very considerable area of the lamina.

Nemalion elminthoides (Velley) Batters.

Velley’s figure (in Withering, “ Bot, Arrang.,” ed. 2, vol. iii, p. 255, si XVil,
1792) is unmistakable, and it is confirmed by his specimen in Herb. Kew ;
his name, therefore, is rightly adopted by Batters in favour of the more familiar
JV. lubricum, 1830. Velley’s plants were collected at Portland Bill in (or
previous to) 1792, and it was interesting to observe in July, 1911, that the
plant still grows there in profusion.

A more difficult matter is the separation of this species from the well-
known NV. multifidum, described by Weber and Mohr in 1804. Ecological
observations on Clare Island (p. 37) and elsewhere increase the suspicion that
the two may be forms of one species; but the point requires detailed study.
Interesting notes on the protonemoid stage of Nemalion and its biology are
given by Chester (Bot. Gaz., xxi, p. 340) and by Rosenvinge (709, p. 144).

Scinaia furcellata Bivona.

Found during the first year of the Survey only by J. Adams whilst
dredging off Mulranny in about 7 fathoms (August, 1909). Distribution in
Clew Bay probably local.

Gelidium aculeatum Batt. (= G. cornewm var. aculeatum Grev.).

Having no personal knowledge of the value of characters in Gelidium, I
follow Batters, who raises this plant to specific rank. It thus figures as an

15 134 Proceedings of the Royal Irish Academy.

addition to the Irish flora; but it is not unlikely that it has often been
collected as a variety of G. corneum, though no record of the fact has been
found.

Phyllophora Brodiaei J. Ag.

A boreal species. Not previously collected on the west coast, but known
from the north of Ireland, Scotland, and northern England.

All the specimens labelled P. Brodiaer from the south of England in the
Kew and British Museum herbaria are misnamed, being forms either of
P. palmettoides or P. rubens, and there is little doubt that the same applies to
other south coast records (ef. Batters, ’02, p. 65).

Callymenia Larterae Holmes, Journ. Bot., ’07, p. 86.

Several plants washed ashore on Clare Island in October, 1910, have
been determined by Mr. Holmes as belonging to this species. The plant is
characterized by the tapering base of the frond and its repeated proliferous
branching. It has doubtless been overlooked in the past as a variety of
C. reniformis.

Gracilaria confervoides var. procerrima (Turn.) Batt. ©

Amongst the many forms assumed by this species, this variety is one of
the most distinct. It is doubtless the same as Harvey’s variety longisstma, of
which he remarks: “Var. [3 is often 6 feet long, and quite simple, or with a
few short lateral ramulae. Its peculiarities appear to result from its place of
growth (Charlestown Harbour, Rhode Island), and intermediate forms connect
it with the ordinary much-branched varieties.” The Irish species confirm
Harvey’s opinion. They were dredged in Clew Bay, though some fine
specimens 5 feet long were gathered by hand in the channels in Achill Sound.
The amount of branching varies considerably; but the short subulate
raiulae are almost constant. Probably common in Ireland, but no record
found.

Nitophyllum uncinatum J. Ag.

This species is usually regarded as synonymous with WV. daceratum var.
uncinatum—an error which is due to the citation of a false synonym’ in the
original description. The plant was described by J. Agardh in 1852. He
states that it is not uncommon in the Mediterranean, and was characterized
by the possession of acuminate fronds and of occasional uncinate branches ;
the sori were produced immediately behind the apex of special short branches.
Unfortunately, Agardh quoted WV. laceratum var. uncinatum, which is a

Clare Island Survey—Marine Algae. 15 135

perfectly distinct plant, as a synonym. I have already pointed out this
confusion (Kew Bull., 1909, p. 242); but the following notes, based on
observations at Plymouth and in Clew Bay, deal with the subject in greater
detail.

Taking first NV. daceratum, we find that the variety wneinatwum is directly
connected with the ordinary forms of this common plant. WV. lacerutum is
(with very rare exceptions) the only species found in rock-pools on open shores,
and, though it exhibits great variety of form, there is usually no difficulty in the
specific identity of the plant, the iridescent fronds of a pale brick-red or dull
purplish-red colour being very characteristic. The uncinate form is not
uncommon in pools, being found from early summer till autumn; it appears
to be connected with a more or less vertical habit and contact with other algae,
being usually found clinging to Corallina. The hooks may be few or numerous,
and terminal or apparently lateral. ‘he form of the frond is very variable,
often lobed or bluntly pinnate, but never possessing the definitely acuminate
branches of IV. uncinatum (Plate X, fig. 11).

When JW. laceratum occurs in the sub-littoral (1-7 fathoms), the form of
the thallus differs somewhat, being longer and more or less regularly
dichotomous ; but the iridescence and characteristic dull colour are maintained.
Uncinate specimens occasionally occur; but, except for increased length and
greater regularity, they differ little from the rock-pool form. They are clearly
connected with the normal plant. ‘Tetrasporic sori are frequent ; these are
found, as is characteristic of the species, either in special proliferations or along
the margins of the fronds.

NV. uncinatum J. Ag. is, on the other hand, a plant confined to the sub-
littoral region, and, though abundant in Clew Bay, is less generally distributed
and apparently very local. It is found in late summer and autumn, being
washed ashore in profusion in August, September, and October, in 1909, 1911,
and 1910 respectively. It is distinguishable at once by its deep crimson or
erimson-lake colour, and lack of iridescence. Most often it is attached to the
stems of Laminaria Cloustoni; but it is found on various stiff algae such as
Cystoseira, Gracilaria, etc., and by means of its hooked branches is entangled
with loose weeds of all kinds. The acuminate character of the branches is
always noticeable, but is most marked in young plants. The hooks are formed
at the termination of the shoots, but not infrequently new branches grow out
below the apex and take on the function of the main shoot so that the growth
is sympodial (Plate X, fig. 10). The same course of development probably
oceurs in VV. laceratwm var. uneinatum ; but if this be the case, the sympodial
growth is more perfect, as the uncinate branches appear merely as small lateral
hooks (Plate X, fig. 11). Cystocarps are unknown in N, wneinatum, but

15 136 Proceedings of the Royal Trish Academy.

tetrasporic sori are not infrequent, being produced in special short branches.
The plant is very closely allied to NV. reptans Crn.; and it is doubtful whether
they are really distinct. I have not had the opportunity of examining a good
series of the latter plant. For an account of the anatomy and physiology of
algae with uncinate branches see Nordhausen (’99).

To sum up, the deep colour, lack of iridescence, and acuminate branches
clearly mark this species, whilst its sub-littoral habit and obviously terminal
hooks also aid in separating it from the uncinate form of NV. /aceratum. It is,
however, allied to that species; and they have this feature in common, that
they are both liable to be infected with the parasite Gonimophyllum.

Bonnemaisonia hamifera Hariot.

The discovery of Bonnemaisonia hamifera on the west of Ireland raises
doubts as to whether this alga is not after all indigenous to Europe. Originally
described from Japan, it has been usually regarded as a plant introduced to
the south coast of England. It was collected by T. H. Buffham at
Falmouth in 1895, and was subsequently found at Torquay and Shanklin
(Isle of Wight). The Rev. H. Boyden tells me he has gathered it within the
last few years at several widely separated localities in Cornwall (West
Looe, Falmouth, and Penzance); and I have noted it for some five or six
seasons in rock-pools at Weymouth. Chalon lists it from Cherbourg on the
other side of the Channel, but it is not known elsewhere in Europe. It is
locally frequent, but never abundant.

With regard to Clare Island it was with some astonishment that several
fronds of the plant were emptied out of a tube of mixed algae collected at
Kinnacorra in June, 1910. In October of the same year, and in April of the
next, the locality was specially searched, but no further specimens were found.
During August, 1911, however, one or more loose fronds were noted in Achill
Sound, Roonah Point, and Clare Island, so that there is no doubt whatever
that the species occurs in the district (see p. 165).

Laurencia hybrida Lenorm.

Although our three British species of Laurencia are perfectly distinct,
considerable confusion exists with regard to the present species, which is
usually found in herbaria, not only under the names of L. hybrida and
L. caespitosa, but also on the same sheets as L. pinnatyida and L. obtusa. The
plant is poorly described in most of our floras, and the confusion is increased
by a difficulty as to names.

Nomenclature.—The name to be used is clearly L. hybrida (DC.) Lenorm.
Fucus hybridus was described by De Candolle in 1805 (“Flore Frangaise,” 1i,

Clare Island Survey—Marine Algae. 15 137

p. 30). It was transferred to Laurencia by Lenormand in 1830 (Duby,
Bot. Gall., p. 951); and his name has been used by Kiitzing, J. Agardh,
Le Jolis, and De Toni. Dawson Turner in 1808 named the plant L. pinna-
tifida var. angusta, giving a figure (Synopsis, Pl. 20, fig. 7), and quoting
L. hybrida as a doubtful synonym. Turner’s name was adopted by Greville
(who gives an excellent figure), Hooker (Brit. Flora), and Harvey (Manual
Ed. I, p. 69, and Phye. Brit., Pl. 55). The ideas of these writers as to the
plant were not very exact, and they confused it with narrow forms of Z. pinna-
tifida. A third name (and one which has been largely used in this country)
is Z. caespitosa Lamx., which dates from 1813. This, however, was a xomen
nudum, and was moreover reduced to a synonym of L, dasyphylla by C. Agardh
in 1822. But in 1840 it was taken up by Montagne (for a plant which he
afterwards decided was a new species, LZ. canariensis, Pl. Crypt. Can., p. 154,
and Kiitz., Spec. Alg., p. 854), and was used by Harvey in the second edition
of the Manual and also in Phye. Brit. (Pl. 286). Our plant, therefore,
figures in the latter work under two names; and Harvey himself admits doubts
as to the species. J. Agardh, at a later date, examined some of Lamouroux’s
specimens, and redescribed what he considered the true JZ. caespitosa Lamx. ;
the identity of this plant is, however, doubtful. Though most of the older
writers confused the species with narrow forms of L. pinnatifida, the plant
they had in mind is perfectly clear, both from their descriptions and from
specimens in herbaria. Some have used one name, some another. The name
hybrida (1805) has priority over caespitosa (1813), which, as we have seen, was
merely a nomen nodum till 1840. There is no question that the plant is
distinet from L. pinnatifida.

Description and Habitat.—L. hybrida is abundant on the British shores and
forms part of the Gigartina-Laurencia association of exposed coasts, but it is
also frequent in rock-pools. It may always be distinguished from LZ. pinnatifida
by the constantly cylindrical fronds and its pyramidal outline. The small size,
greenish colour, and caespitose habit are also noteworthy, whilst its marked
winter growth and absence in summer are quite characteristic. Small sporelings
2-3 mm. high are discernible in September ; these develop during autumn and
winter, and fruit in early spring. By May the plant begins to disappear, and
is not seen again till September or October. When growing on bare rocks
which are left dry by the tide, the plant is very compact, and seldom more
than 1-2 inches high ; but in shallow pools fully exposed to the light, it is more
lax, and may attain a height of 4-5 inches. In autumn and winter Z. hybrida
is a dark greenish purple; but with the advance of spring the purple hue

‘Tn some copies of this work the date is erroneously stated to be 1815.
R-I,4, PROC., VOL, XXXI. ) 45

15 138 Proceedings of the Royal Irish Academy.

disappears, and the plant assumes a green colour, pale when growing in sunny
pools, but darker when on bare rocks or under the shade of other plants. It
should be noted that LZ. pinnatifida also reaches its maximum development in
spring ; but it is present more or less throughout the summer, and appears to
possess a persistent base (see p. 35).

L. hybrida has been also confused with Z. obtusa with which it agrees in
possessing cylindrical fronds. The colour and habit of the two are, however,
very distinct. Z. obtusa is a sub-littoral plant of dark red colour which becomes
yellow with sunlight. It is also found in pools and shallow water, especially
in winter and spring, and is almost always epiphytic. There is further an
important morphological distinction to be noted in the structure of the
antheridial conceptacles. The conceptacles of Z. hybrida will be found to
resemble those of LZ. pinnatifida, and to be quite distinct from Z. obtusa
(see Falkenberg, ’01, pp. 242 and 249).

The distribution of the present species is more restricted than that of
the other two. It is common in England, Scotland, and Ireland, and is
found on the north and west coasts of France; but I have not seen undoubted
specimens from other countries, The records from the Mediterranean, Ceylon,
Japan, and the West Indies require verification. The antheridial character
referred to above will possibly aid in the identification of this species, since
in Laurencia exact similarity of form cannot be insisted upon when climatic
conditions are different.

Polysiphonia macrocarpa Harv.

First described by Harvey in Mackay’s “ Flora Hibernica,” part ii, p. 206.
It was wrongly united in “ Phyc. Brit.” with P. pulvinata, but is rightly
presented in Batters (02). Amongst British species it is very distinct;
but Bornet suggested that it might be a form of the Mediterranean
P. sertularioides, though in his “ Algues Schousboe” he preferred to keep them
apart. P. macrocarpa usually grows in shallow crevices near low-water on
exposed rocks, being not uncommon on Clare Island, and the only species
of the genus noticed on The Bills.

P. fastigiata Grev.

Though usually confined to Ascophyllwm nodosum, it is interesting to note
that in exposed localities (where that plant is absent) P. fastigiata is frequently
found on Fucus spiralis. In a general way F. spiralis on exposed rocks on
Clare Island is free from the epiphyte; but at Alnahaskilla scores of infested
plants may be counted. P. fastigiata was noted on the same host at other
spots on the island, and in one case it occurred on F, vesiculosus,

Clare Island Survey—Marine Algae. 15 1389

P. subulifera Harv.

This rather rare species is apparently frequent in the west of Ireland,
being found abundantly in Clew Bay, Achill Sound, and also in Roundstone
Bay. Harvey notes its frequency on the Lithothamnium banks at Round-
stone; and in September, 1911, it was the dominant species. It was also
dredged on similar ground in Clew Bay, and appears to be one of the
Florideae which can withstand considerable insolation in shallow water.

Dasya arbuscula Ag.

The frequency with which this plant is met with in Ireland at once strikes
the collector as a great contrast to the south of England, where, though found
from Land’s End to the Isle of Wight, it is always rare. Harvey (Phye. Brit.)
notes its abundance at Bantry Bay, and on Clare Island it may be regarded
as one of the most frequent and constant of the miscellaneous collection of
Redweeds that occur near low-water mark on moderately exposed rocky
shores (e.g. Kinnacorra). At certain seasons also it is washed ashore in
plenty (July, August ?).

Ptilothamnion lucifugum sp. nov.' (Plate IX).

Plants gregarious, minute, 1-1‘5cem. high. Fronds decumbent at the
base, then erect, producing branches and pinnae irregularly. Branches
3-6 mm. long, irregularly beset with pinnae ; cells, 35-50 uw wide, by 3-4 times
as long. Pinnae short, 2-3mm, long, opposite, but more often irregular,
usually naked below, but bearing above regularly opposite forked pinnulae ;
cells 25-30 wide by 14-2 times as long. Pinnulae bifid through the
production of a lateral branch on the under side of the lowermost cell, rarely
simple, very rarely trifid; cells 15-20 » wide by 13-2 times as long. Decumbent
portion of the frond irregularly attached to the substratum by rhizoidal
puunae, which occasionally terminate in a discoid expansion. Tetraspores
and cystocarps unknown. Antheridia borne on the terminal cells of the
pinnulae.

Hoabitat.—Attached to rocks in shallow ‘pools in a dark cave, Portlea,
Clare Island, August, 1911.

Closely allied to P. micropterum (Mont.) Bornet, but distinguished by its
irregular branching, larger size, and peculiar habitat.

The present species was found as a dense mossy covering on the bottom

' Frondes caespitosae, 1-1°5 cm. altae, ramis primariis repentibus secundariis erectis. Pinnae
2-3 mm. longae, pinnulis omnibus furcatis aut rare simplicibus. Articuli ramorum 3-4plo
pinnarum 1-2plo diametro longiores. Sporangia et cystocarpia ignota. Antheridia in articu!o
terminali pinnularum eyoluta. Hab. In spelunca.

Species P. microptero proxima sed frondibus majoribus irregularibus differt.

52

15 140 Proceedings of the Royal Irish Academy.

of a dark cave-pool during the last day spent on the island; owing to-its
minute size, it was difficult to secure, the plants on detachment being easily
lost in the water. No tetrasporic or cystocarpic plants were obtained, but
sufficient material was collected to show general characters. The plant
is closely allied to P. micropterum, which was described by Montagne from
the Canary Islands. Sauvageau also collected it on Cystoseira at Guethary,
and in recording the same, adopted a suggestion by Bornet, and yemoved
the plant from Callithamnion to Ptilothamnion (Sauv.,’07, p. 206). Monsieur
Hariot kindly allowed me to examine the Canary Islands type from the
Paris Museum; and it was found to consist of a smaller and much more
compact plant, probably of epiphytic habit. The Guethary specimens appear
to have been mislaid. Reinsch’s C. pinastroides (suggested as a synonym in
De Toni, Syll. Alg., iv) is certainly distinct; but Hauck’s C. pluma from
Trieste (Beitrage, vii, 1878, p. 151) proves, on examination of the specimens
kindly lent me by Madame Weber, to be P. micropteron. No other record
exists. As P. micropteron is so very little known, it is within the bounds
of possibility that the Irish plant is an extreme form of that alga; but
taking all things into consideration, it appears wiser to regard it as a
distinct species.

Spermothamnion Turneri var. subverticillatum cumd. nov.

Callithamnion Turneri var. subverticillatum, Lenorm. MS., in Herb.
C. subverticillatum, Zanard. in Kitz. Tab. Phye., xi, tab. 81 ?

The specimens referred to this variety agree precisely with plants so
named by Lenormand in the Kew Herbarium. C. subverticillatwm Zanard.
is most probably the same plant, but apparently Zanardini’s specimens
were not kept, as the plant is not listed in De Toni’s catalogue of his
herbarium. The variety differs from the ordinary form in the elongated
slender shoots, and in the sub-verticillate branching. In Clew Bay it
was found on several occasions, but always in a floating condition. As
seen thus it is very distinct, and would appear to be a good species, as
Zanardini believed; but whether the characteristic habit is due merely to
growth subsequent to, and resulting from, detachment was not ascertained.
Until this can be determined, and the question of Zanardini’s plant inquired
into, it appears best to regard the alga as a variety.

Griffithsia corallina Ag.

Occurs in the greatest profusion during spring in Clew Bay and Achill
Sound. It is largely epiphytic and is found in channels and in shallow water.

Clare Island Survey—Marine Algae. 15 141

Beautiful specimens, perfectly spherical in form and sometimes as much as
20cm. in diameter, may be seen floating in with the tide during May. No
plants were noted in the rock-pools on Clare Island.

Bornetia secundiflora Thur.

Bornetia is one of the most interesting additions to the Irish flora. It is
abundant in the Mediterranean (south France), and common in the Biarritz
neighbourhood. It extends up the Atlantic coast as far north as Normandy
and Brittany, and is found as a very rare plant on the shores of Devon and
Cornwall. Two fine plants were collected in a deep pool on Clare Island,
in July, 1909, and though neither bore mature fruit, there can be no doubt
as to their identity. The pool was searched on each subsequent visit; but,
with the exception of a small frond found in August, 1911, no further
specimens were observed.

Callithamnion byssoides Arn.

The specimens referred to this species agree well with those from
Devonshire collected by Mrs. Griffiths, and with the plant as generally
understood in this country. In general habit it bears a very close resem-
blance to C. corymbosa, and even with a lens it is not easy to separate the
two. The distinctive feature is the irregular pinnate branching, which
connects it in the other direction with C. rosewm. From the latter it is
marked off by the very much more slender growth, and by the tetraspores
being usually single on the pinnae. The form of the cystocarp is also
different.

C. byssoides is common in Clew Bay and Achill Sound (as a spring
and early summer plant), occurring as an epiphyte on various algae in
the low-littoral and sub-littoral region. It is very closely allied to, if
not identical with, C. Furcellariae of the Swedish botanists.

C. scopulorum Ag.

I follow Borgesen in regarding this plant as a distinct species, which
differs from C. polyspermum in its dwarf size, absence of cortication, and
saxicolous habit. It is abundant on Clare Island, on moderately exposed
rocks, but, owing to its minute size, is not conspicuous.

C. arbuscula Lyngb.
An alga belonging to the boreal group, but abundant on Clare Island.
It apparently occurs on all the Ivish coasts, but is quite absent on the south
of England (see pp. 164 and 169),

15 142 Proceedings of the Royal Irish Academy.

Callithamnion corymbosum Lyngb.

Very abundant in spring and early summer, and found probably throughout
the whole year. It was plentiful in October, 1910, at Achill Sound; and
numerous young plants were dredged in Clew Bay the following February.

C. granulatum Ag.

When Harvey dealt with C. spongiosum in“ Phye. Brit.,” he suggested
the possibility of its being united with C. granulatum Ag. In1851,J.Agardh
carried out this prediction, and his view has been generally accepted. There
are, however, two very distinct forms. One, which occurs in the C. arbuscula
association, is compact, densely branched, and turns a pale greenish-yellow in
summer; and the other, which hangs from vertical rocks in company with
Plumaria elegans, is larger, less compact, and does not occur in sunny places.
The former agrees in habit with the Mediterranean C. granulatum; and the
latter is undoubtedly Harvey’s C. spongiosum. The matter requires careful
investigation, as it appears possible that Harvey’s plant may after all be
a good and distinct species. Both forms occur in Clare Island, and no
intermediates were seen.

Ptilota plumosa Ag.

This species, which is said to occur all round the Irish coasts, is perhaps
the most noteworthy of the boreal algae that are found on the west of Ireland
(see pp. 165 and 169).

Antithamnion crispum Thur. in Le Jolis’ “ Liste,” p. 112.
(A. Plumula var. crispum J. Ag., Batters, Cat., p. 89.)

This plant is distinguished from A. Plumula by its short recurved pinnae
and thorn-like pinnulae. It is widely distributed, and often occurs where
A, Plumula is absent (i.e. in the Adriatic; see Krasser in Zahlbruckner,
Krypt. Exsicc., No. 648). Batters follows Agardh, who regards it as a variety;
but the views of Thuret, Krasser, and others appear warranted. The true
A, Plumula was not found in Clew Bay, and the Bantry Bay species in Herb.
Kew are also referable to A. crispum.

Ceramium Boergesenii Petersen.

Dr. H. Petersen, who is at present investigating this genus, kindly
undertook to examine my material. To him is due the discovery of this, and
the following addition to the flora of our islands. C. Boergesenii has doubtless
been passed over as a form of C. decurvens, to which it is very closely allied.

Clare Island Survey— Marine Algae. 15 143

It is chiefly distinguished by the corticating cells which grow upwards as
well as downwards from the nodes. Frequent in our district, being found
especially on the receptacles of Himanthalia on Clare Island.

Distribution.— Iceland, Faerées.

C. atlanticum Petersen.
A pretty little species, described by Petersen, from Iceland and the Faerées.

On Clare Island a few specimens only were found. It apparently enjoys open
conditions, being collected on exposed rocks and on The Bills

C. rubrum Ag.

Dr. Petersen distinguishes the following forms in my material of this
perplexing species :—
(a) prolifera-secundata, forms typica, secundata, and irregularis,
(b) pedicellata-virgata, f. irregularis.
(c) subtypica-modificata, forms vera and irregularis.

Abundant in great variety of form in all parts of our area.

Gloiosiphonia capillaris Carm.

Found in several spots on the island during the first year of the Survey
only (July, 1909). Not present in the same spots in June, 1910, nor
August, 1911.

Schizymenia Dubyi J. Ag.

This is a distinctly southern plant, being known in England from Devon

and Cornwall only. In Ireland it has been recorded from Belfast Lough, but

not from the west or south. Several specimens were noted on Clare Island in
May, 1911.
Cruoria adhaerens J. Ag.

The distinctive features of C. adhacrens are not well known; but relying
on the slides in the Batters collection in the British Museum, I have regarded
it as being characterized by the possession of short filaments which adhere
closely together. The individual cells also are short, but the tetraspores very
large.

Cruoriella Dubyi Schm.

C. Dubyi is the dominant species of incrusting algae in the shallow waters
of Clew Bay. It occurs abundantly on sheils and stones atall seasons ; and, in
the inner parts of the bay, is found occasionally on the stipes of Laminaria

15 144 Proceedings of the Royal Irish Academy.

Cloustoni; tetrasporic fruits were collected in February. The flabellate
arrangement of the cells on the wnder-surface of the thallus (a feature which
Schmitz makes characteristic of the genus) distinguishes it at once, in our
area, from allied plants. ;

Harvey records C. Dubyi (sub Peyssonnelia Duby?) as occurring in great
profusion in Birturbuy Bay, Roundstone (“ Phye. Brit.”); but, as pointed out
below, this was an error, since the specimens preserved are those of
Peyssonnelia. It is remarkable that in Clew Bay Cruoriella should be
dominant, and at Roundstone Peyssonnelia.

Peyssonnelia s7).

The species of Peyssonnelia occurring in west Ireland must for the
present remain undetermined. It was recorded by Harvey as P. Dubyi (now
Cruoriella Dubyi); and he states that it is abundant in Birturbuy Bay.
Batters (96, p. 11) showed that Harvey’s material consisted of a genuine
Peyssonnelia (the T.C.D., Kew, and Linn. Soc. material was examined), and
he referred the plant to P. rubra Grev., a species originally described from the
Ionian islands, and, as generally understood, common in the Mediterranean,
Though the genus is correct, the specific identity appeared questionable.
From Greville’s description, his species is a plant with free-growing lobes,
ie. with the habit of P. sgwamaria; whereas the Clew Bay plant has an
attached encrusting thallus, such as is found in P. Harveyana. In order to
settle the point it was necessary to examine the type in Greville’s herbarium
at Edinburgh ; and through the kindness of Professor Bayley Balfour, it was
sent to Kew on loan. The specimens fully confirmed Greville’s description and
figure, and there is no doubt that the Ivish species must be kept distinct.
Madame Weber van Bosse, who is engaged in unravelling the tropical species
of the genus, informs me that the form of the rhizoids, to which much value
has been attached, is an unreliable character. The species of this, and allied
genera, have in the past been so poorly described, that it is impossible to be
certain if any of them are identical with the present plant. On this account
it appears advisable to wait till a monographic work is available. The
alga is rare in Clew Bay, and fruits in winter.

Porphyrodiscus simulans Batters.

On account of its characteristic nemathecia, the genus Porphyrodiscus was
founded by Batters for the reception of this plant (Journ. Bot., 1897, p. 439).
He detected it at Berwick in 1889, and apparently it has not been found
elsewhere. The Clew Bay specimens were obtained at Annagh Island, on
stones in muddy ground near low-water mark,

Care Island Survey—Marine Algae. 15 145

Rhododermis polystromatica Batters, in obs., Journ. Bot., 1896, p. 389
(R. elegans vax. polystromatica Batters).

The variety polystromatica is so distinct from Crouan’s P. elegans that it
certainly ought to be regarded as a distinct species. Batters himself proposed
the combination in 1896 (1.c.); but in 1902 he (probably inadvertently) used
the older designation.

Choreonema Thureti Schmitz.

A minute species, which requires to be carefully. searched for. It has
been stated to be common in Ireland, and to occur on all three species of
Corallina; but this is probably an errer. On Clare Island it was found only
on C. squamata (its usual host), although a large amount of C. officinalis was
carefully examined with a lens. The plant is also known to occur on
C. rubens.

MELOBESIEAE.

The material of this group, as noted above, was examined by Dr. M.
Lemoine, who kindly furnished critical observations on the specimens, and
also prepared a complete list of the species obtained, together with notes
on their distribution. In view of the confusion existing, the general
distribution of each species as supplied by her is published in the present
report. It will be noted that the nomenclature differs slightly from that
employed by Batters.

Attention should also be drawn to the account given by Johnson and
Hensman (99), where analyses of the Knockboy and Bantry Bay sand,
together with other details of local interest, are given. Since that date much
critical work has been done, and hence seven of the plants listed there as
distinct species are in the present report regarded as synonyms or varieties.

Melobesia farinosa Lamx.

Abundant on Zostera in Clew Bay, and found at all seasons. .
Distribution.— General.

M. zonalis Fos].

This minute species was dredged in Clew Bay (3-5 fathoms) in February,
May, and August, 1911, and is evidently frequent. It occurs on glass,
porcelain, and shells. Jf. zonalis belongs to the subgenus Pliostroma, the
species of which are characteristic by being polystromatic.

Distribution.—England, Scotland, Ireland, N. France ( Brest), Mediterranean
(Banyuls). .

B.1.4, PROC., VOL. XXXI. T 15

15 146 Proceedings of the Royal Irish Academy.

Lithophyllum (Dermatolithon) pustulatum Fosl.

Common on Clare Island, especially on Gigartina and Phyllophora rubens
in rock-pools, and near low-water mark. It was also found on Cladophora
rupestris.

Var. Corallinae Foslie (Melobesia Corallinae Crouan, Batt. Cat., p. 96).—
Common on Corallina officinalis in rock-pools on exposed shores.

Var. Laminariae Foslie (Jf. Laminariae Crouan, Batt. Cat., p. 97).—Not
uncommon on stipes of Laminaria Cloustoni.

Distribution.— British Isles (common), Faerdes, Iceland, Norway, Sweden,
W. Baltic, Denmark, N. and W. France, Mediterranean, Adriatic, Morocco,
Canaries, Greenland, Atlantic coast of N. America. (Mass., Florida, Bermuda,

W. Indies), Pacific (California).
L. (Dermatolithon) hapalidioides Fosl.

Dredged in Clew Bay on several occasions, and probably not uncommon,
though often overlooked. The sub-littoral form is smooth, and very different
in appearance from the variety confinis.

Var. confinis Fosle.—On Patella shells near low-water mark, not
uncommon.

“La structure est la méme dans le type et la variété, et c’est pourquoi
Foslie (1909, p. 128) a réuni les deux espéces L. (D.) hapalidioides et
D. confinis. Comme il le fait remarquer, le Z. confinis correspondrait 4 la
forme sguamulosa du L. Lenormandi; on peut supposer que la var. type vit a
une certaine profondeur sur les coquilles et au contraire que la var. confinis vit
dans la limite des marées. La différence d’aspect résulterait d’une différence
dans les conditions de vie.’ (M. Lemoine.)

Distribution.—British Isles, Faerdes, 8. Norway, N. and W. France,
N. Spain, Algeria, S. France (last three localities var. confinis only).

L. incrustans Philippi.

L. incrustans is the common incrusting alga of pools and rocks on exposed
shores ; and, with the exception of Jathothamniwm Lenormandi, which forms a
belt above it, it is the only species normally occuring in the littoral region
(seep. 41). In the shallow waters of Clew Bay, a very smooth form in
addition to the ordinary is frequently found.

Var, subdichotomum Heydr.—To this curious variety must the L. dentatum
of the west of Ireland be referred. ‘The record is due to Foslie, who dredged
specimens in Roundstone Bay in 1899. He first regarded them as forms of
L. fasciculatum, but later referred them to ZL. dentatum. The latter is a
native of the Adriatic; but though recorded from Naples and Tangier, its

Clare Island Survey—Marine Algae. 15 147

position in Ireland was very isolated, as it is entirely absent from the French
coasts.

Specimens dredged by me in Clew Bay agreed well with Foslie’s material
in the Dublin Museum, and Dr. Lemoine, to whom a fragment was sent, at
first passed it as that species. She, however, subsequently wrote that it bore
a striking resemblance to certain curious forms of Z. inerustans, which had
been described from Guéthary (Basses Pyrénées) by Heydrich, and further
examination showed that the structure agreed with Z. incrustans rather than
with ZL. dentatum. As it was advisable to have the point finally settled,
further material was sent, including a specimen gathered by Foslie at
Roundstone. Madame Lemoine kindly examined the samples anatomically,
and reported as follows :—

“ Je crois que tous ces échantillons représentent des formes de ZL. incrustans,
mais ce sont des formes anormales et curieuses. Ce sont des échantillons
ages qui se sont séparés de leur substratum, et qui ont pris ce développement
bizarre. Je me suis rendu compte aussi que l’algue était agée, parce que,
dans certains échantillons, en particulier dans celui de Clew Bay, le tissu se
désagrege aprés décalcification, et il est impossible d’obtenir des coupes dans la
partie centrale.

“Je ne suis pas arrivée a observer l’hypothalle, il aurait fallu abtmer les
échantillons; les lamelles libres ne sont constituées que par le périthalle.
J’ai étudié les deux échantillons de Roundstone dans lesquels les dimensions
des cellules sont comparables 4 celles des cellules de L. incrustans.

“Les échantillons de Roundstone appartiennent 4 une forme décrite par
Heydrich f. subdichotoma ['99, p. 225]. Ils seraient plus jeunes que celui de
Clew Bay, qui, usé et roulé par les vagues, est tout a fait caractéristique de
la f. subdichotoma.”’

A comparison of Heydrich’s figures in the paper referred to (Berichte d. d.
bot. Ges. xvii, p. 221) shows that the Irish specimens agree in form with the
Mediterranean. The plant israre, but one or more inolls were collected on
each occasion that the Clew Bay or Roundstone “coral-banks ” were dredged.

Distribution—L. incrustans :—British Isles (abundant), Faerdes, N. and W.
France, N. Spain, 8. France, Italy, Dalmatia, Algeria, Morocco (Tangier and
Atlantic Coast), Canaries, S. Africa, Sandwich Islands.

Var. subdichotomum.—Ireland (Clew Bay, Roundstone Bay), France
(Guéthary, Banyuls).

L. lichenoides Philippi.

Lemoine (11, p, 128) states that the anatomical structure of this species
is clearly that of Lithophyllum, and she therefore restores it to that genus.
T2

15 148 Proceedings of the Royal Irish Academy.

In England it is only known from the south coast ; but it has been found in
all the provinces of Ireland except Ulster, and is very common in the Clare
Island district. It isusually attached to Corallinu officinalis, and occurs in
pools and in the low-littoral region.

Var. agariciformis Foslie.—Batters, following Foslie, regards If. agariei-
Jormis Harv. as a variety of this species ; and Madame Lemoine, to whom I
sent for anatomical examination a fragment of a Roundstone specimen
(probably collected by McCalla), writes that there is no doubt whatever that
Foslie was correct. The variety is evidently exceedingly rare, as no trace of
such a form was found by me on any of the Lithothamnium banks of Clew
Bay or Roundstone.

Distribution.—A southern species. 5. and W. Ireland, §. England, N. and W.
France, N. Spain, Mediterranean, Morocco.

Var. agariciformis. Roundstone Bay.

L. fasciculatum Fos].

This species is known only from the west of Ireland, and is thus one of
the most interesting algae of the Irish flora. It is known locally as “ Wild
Coral,” and is plentiful in Clew Bay, occurring in patches mixed with
Lithothamnium calearewm. It is also common at Roundstone (see p. 70).

Foslie distinguished several forms of the present species (09), The
plant was accidentally omitted (or rather unintentionally united with another
species) in Batters’ Catalogue, as explained by me last year (Journ. Bot.,
p. 115).

Distribution—Clew Bay ! Roundstone! Fahy Bay! Schull and Ballina-

courty (teste Johnson).

Lithothamnium caleareum Aresch.

The dominant species of the fruticulose Lithothamnium association of
Clew Bay and Roundstone (see p. 69). It occurs in great diversity of
form, but it seems clear that varieties compressa McCalla, squamulosa Fosl.,
erasst Lem., subvalida Yosl., and subsimplex Batters, as described and figured
by Lemoine (710), are the most common in the district. Reference should be
made to that paper for details as to biology and ecology. Mannin Bay,
where Z. caleareum occurs abundantly, is worthy of further investigation,
and should be compared with Roscoff and Concarneau, which have been
investigated by French botanists.

Distribution.—British Isles, N. and W. France, Norway, Denmark,
Portugal, Morocco, Algeria, Mediterranean (Naples, Adriatic).

Clare Island Survey— Marine Algae. 15 149

Lithothamnium norvegicum Kjellm.

L. nervegicum is an addition to the published list of our flora. It has been,
however, sent out recently by Holmes in his “ Algae Britannicae Rariores ”
(No. 264); he obtained specimens from Arran (Scotland). The species
resembles in forma small, much-branched specimen of Z. caleareum ; but the
branches are more slender and the whole plant more compact. The structure
also is distinct (see Lemoine, ’11, p. 108). It has doubtless been mistaken
for LZ. caleareum in the past, and is probably not uncommon on our shores.
In Clew Bay it occurred sparsely scattered amongst other species.

Distribution.—Clew Bay, Roundstone, W. Scotland (Arran); Norway,
Denmark, America (N. Atlantic coast).

L, laevigatum Fosl.
(Phymatolithon laevigatum Fosl., Batt. Cat., p. 98).

A sub-littoral species, but found occasionally in caves. It was dredged off
The Bills in about 15 fathoms, and was found on limpets in a cave on Clare
Island.

Distribution—England (Berwick), Ireland (Gola Island, Larne), Faeroes,
S. Norway, Denmark, Atlantic coast of N. America (Rhode Island, Maine,
Newfoundland).

L. polymorphum Avesch.
(Phymatolithon polymorphum Fosl., Batt. Cat., p. 98).

Common on exposed coasts in our area, and forming a band below
L. incrustans, as explained on p.41. For taxonomy see Lemoine (11), p. 63.

Distribution.—British Isles (common), Norway, Sweden, Denmark, Faeroes,
Iceland, Heligoland, N., W. and S. France, Tangier, Mediterranean, Adriatic.

L. compactum Kjellm.

(L. cireumscriptum Stromfelt ; Clathromorphwm circumseriptum Fosl., Batt.Cat.,
oe Oy
Foslie at first regarded LZ. compactum and L. circumseriptum as distinct, but
subsequently referred them to the same species. Kjellman’s name antedates
Stromfelt’s by three years,and must be adopted (see Lemoine, ’11, p. 98). The
plant was dredged twice, in 5 fathoms between the outer islands of Clew Bay,
and in 7 fathoms off Mulranny. It is listed by Johnson and Hensman ('99),
but no locality is given, and it has not been found in England or Scotland.
Distribution.—Ireland (Mayo), Faerdes, Iceland, Norway, Spitzbergen,
Nova Zembla, Greenland, Atlantic coast of N. America (Maine, Newfoundland,
Nova Scotia), and Pacific Coast (Alaska).

15 150 Proceedings of the Royal Irish Academy.

L. Lenormandi Fos.

Common in our area, forming an irregular band on damp and shady
rocks above Z. incrustans (see p. 41). It is also very common on stones in
pools.

Var. sublaevis Foslie—A sub-littoral form. Not uncommon in Clew Bay
in 3-8 fathoms, on shells, especially Pecten.

Var. squamulosa Foslie.—Frequent on the sides of dark caves.

Distribution.—British Isles (common), Iceland, Faerdes, Norway, Sweden,
Baltic Sea, Denmark, Heligoland, N., W., 5. France, Mediterranean, Adriatic,
Morocco, Canary Islands, N. America (Atlantic Coast).

L. Sonderi Hauck.

Beautiful specimens belonging to form sublaevigata Foslie were dredged
from the “Helga” in Killary Bay. They formed a complete crust on the
shells of mussels which occurred abundantly in muddy places. Superficially
I. Sonderi strongly resembles LZ. Lenormandi; but the structure is quite
distinct, the filaments in the former separating easily from each other, whilst
in the latter the tissue is very compact (Foslie, 05, p. 24, Lemoine, 711,
pp. 84 and 97). Z. Sonderi has not been recorded from England, but specimens
have been dredged by me at Plymouth in 1905 (¢este Foslie).

Distribution.—British Isles, Norway, Sweden, Denmark, Heligoland,
France.

Epilithon membranaceum Heydr.

(L. membranaceum Fosl., and L. corticiforme Fosl., Batt. in Cat., p. 97).

It is satisfactory to find that authorities agree in regarding the two species
above cited as synonymous—a view held by several British algologists, though
Batters in 1902 kept them distinct. Dr. Lemoine did not deal with the plant
in her treatise on the Melobesieae (’11), but, in response to a special inquiry,
she wrote the following note :—“J’ai étudié avec soin dans les Herbiers les
E. corticiforme and E. membranaceum, je crois, comme d ailleurs ¢’était l’opinion
de Foslie (1909, p. 75), qwils doivent étre réunis. I] est probable quon a
désigné sous le nom de corticiforme les thalles portant des conceptacles a
sporanges, et sous le nom de membranacewm ceux portant les conceptacles a
crystocarpes. L’aspect des deux sortes de conceptacles est trés different ;
les conceptacles 4 sporanges mirs forment des sortes de petits crateres qui
laissent voir en leur centre le substratum; ces cratéres, trés nets sur
léchantillon de Clew Bay fixé sur Rhodymenia, sont souvent confluents et
leur contour est ovale. Au contraire les conceptacles 4 cystocarpes sont
dabord hemisphériques ; plus tard le toit tombe et il peut rester un petit trou

Clare Island Survey— Marine Algae. 15 151

asa place, mais le trou est circulaire. Si on conservait l’indépendance des
deux espéces, 1] faudrait admettre que dans chacune on ne connait qu'une
seule sorte de conceptacles.. Dans l’Herbier Bornet ces deux espéces sont
séparées; j’ai cherché en vain des conceptacles a cystocarpes pour le
E. corticiforme. ailleurs d’apres les descriptions de Rosanoff et de de Toni
il est 1mpossible de les distinguer. Hauck les a réunis.”

Tt is clear that the present species cannot be retained in Lithothamnium ;
and Dr. Lemoine believes that Heydrich, who first clearly pointed out its
peculiarities, was justified in forming a special genus for its reception, and that
it is advisable to adopt his name. The nomenclature is, however, somewhat
complicated by the question of the validity of Kiitzing’s genus Hapalidium.
£. membranaceum is common in the Survey area, being found most often on
Rhodymenia palmata and Furcellaria fastigiata. In autumn it is not infrequent
on Cladophora rupestris in shallow pools near high-water line, to which it
gives a very curious appearance. It is also found occasionally on other algae
and on shells (Trochus).

Distribution.— British Isles (frequent), Norway, Sweden, N. and W. France,
N. Spain, Mediterranean, Crimea, Morocco (Atlantic coast), Ceylon, California.

Corallina squamata Ellis.

This species is probably much more common in the warmer parts of the
British Isles than is generally supposed. On the exposed coasts of Clare
Island it is, as explained on p. 40, probably more abundant than C. officinalis.
In the south of England also, I have noted it very frequently in similar
localities.

3. ECONOMIC SPECIES.
celp.

Kelp-burning forms an important feature in the yearly routine of the
islanders, as it does also on the exposed coasts of the mainland. During the
last weeks of June and in the beginning of July dense clouds of heavy oily
smoke may be seen along the coast-line, and the preparation for this general
burning provides employment for many months. In a leaflet issued by
the Congested Districts Board' practical advice is given, including notes
as to the relative value of the different seaweeds, and instructions as to the
best methods of burning. ach species is figured, and also certain weeds
which should he avoided,

1 «The Kelp Industry. Hints for Kelp-burners with regard to Seaweed.’’ Congested Districts
Board Leaflet. 1898, i

15 162 Proceedings of the Royal Irish Academy.

The “rods” (stipes) of the various Laminariae employed are collected as
they are cast ashore in autumn, winter, and spring, and placed on the
stone walls till burning time. In February and March the weed is also
cut by hand during the lowest tides. From April Ist until June the “ tops ”
or “leaves” (laminae) are collected in addition to the rods; and these are
mixed with the latter when burning. It is during April and May that
L. Cloustoni sheds its fronds, hence the term “ May Weed.” ‘The name “ Red
Wrack ” is given on account of its red-brown colour after exposure to weather.

Of the weeds employed, the bulk of the rods consist of Z. Cloustoni,
together with a slightly smaller amount of Z. digitata. L. saccharina and
Sacchorhiza bulbosa are also used and are equally valuable; but they are not
washed ashore in anything like the same quantity. A storm or ground
swell provides the islanders with several days’ work, the “rods” being
picked out for kelp, and the tops used (except in April and May, when part
is set aside for burning) on the fields as manure. The foliage of L. saccharina
bleaches at once with rain, and is then of no value for kelp; JZ. digitata
bleaches less readily ; and Z. Cloustoni, as noted above, turns reddish-brown,
Alaria esculenta and Halidrys siliquosa are recommended in the Leaflet, and
are used in small quantities with the “tops.” Ascophyllum and Fucus spp.
yield but a very small amount of iodine, and are usually rejected. One of
the most important papers on the commercial value of algae is that by
Stanford (84), which, though somewhat out of date, has not been superseded.

Manure.

Seaweed is extensively employed as manure all round the coast. In many
spots the drift-weed washed ashore is sufficient for requirements; but in
others the weed is cut by hand from the rocks, whilst in a few localities it is
actually cultivated.

A good dressing of seaweed is always applied to potato beds previous to
planting ; in some cases so soon before that the sets are practically placed
over a layer of fresh weed. It is usually put on stubble after cutting oats,
and applied again to the land in spring. A dressing is also spread on meadow
land ; and in May the reddish fronds of the “ May Weed ” (= LZ. Cloustont), and
the streaks of white due to patches of bleached Z. digitata and L. saccharina,
give striking colour-effects on the green fields.

The species employed vary according to the nature of the shore. On
exposed rocky coasts Laminaria is washed up ; and where obtainable in plenty
as in Clare Island, other weeds are despised. Laminaria is industriously
collected during winter and spring, and carted or carried by panniered ponies

Clare Island Survey— Marine Algae. 15. 153

to the fields; on the mainland it is at times carted seven or eight miles inland.
In other localities, such as Old Head and Bartraw, the farmers are content
with drift-weed of a miscellaneous description. The drift is more valuable at
some seasons than others. At times it is composed almost entirely of semi-
decayed red weeds cast up from the shallow water, and at others there is.a
certain amount of Laminaria, and occasionally Fucus.

Black Wrack (Fucus vesiculosus and Ascophyllum nodosum) is systemati-
cally collected during February and March, where Laminaria is scarce. In
the rocky parts of Clew Bay, and in many localities on the open coast, it
grows freely on the rocks, though for a really large amount a flat. shore is
essential. This is supplied in abundance in the inner part of the bay, and in
Achill Sound. Where rocks are present Fucus grows naturally, but where,
as is usually the case, the shore is composed of sand, the farmers set to work
to obtain a growth of Wrack by artificial means. Stones about a foot square
are disposed in rows a yard apart, with paths left between for carting.
Sporelings speedily appear on the stones, and during the course of a year
develop into good-sized plants. The following season the Wrack is cut. This
operation, which takes place in February and March, was observed by the
Survey party of Easter, 1910. The weed on cutting is built up in stacks
about six feet high, and after being tightened up with ropes is towed ashore
on the flood-tide, and bleached at high-water level. Here it is unpacked and
carted to the fields. : .

The botanical features of the Fucus-farms are dealt with on p. 53. Owing
to the symmetrical arrangement of the stones, the artificial plots are at once
distinguishable from natural vegetation ; but when the weed is in its second
season and the plants inclined to overlap, the distinction might not strike the
eye of a casual observer. Plate V, fig. 2, gives a view of the plots at
Darby's Point; similar farms oceur in other parts of Achill Sound, and in
Clew Bay they were noted at Murrisk.

The “ coral-sand” described on p. 71 should be referred to here, as it is
used for manuring in Connemara. Johnson and Hensman (799) give the
analysis of a Bantry Bay sample, which shows that the sand consists of
about 80 per cent. of carbonate of lime. ‘'o this fact its efficacy as a

fertilizer is attributed, and it is doubtless specially useful on the peaty
shores of W. Ireland.

Recent Interature.

The Composition of Seaweed and its use as Manure. Journ. Bd. Agr.
London, xvii, pp. 458-467 (September, 1910), p. 832 (January, 1911). Also
abridged as Leaflet No. 254.

R.I,A. PROC,, VOL, XXXI, U 15

15 154 Proceedings of the Royal Irish Academy.

Seaweed as Manure. Journ. Dept. Agr. and Tech. Inst. for Ireland, xt,
pp. 84-87. (October, 1911.) Also as Leaflet No. 99.

Sewage Commission Reports. The manurial value of Ulva and the
significance of its nitrogen-content are dealt with in the reports referred to
on p. 108.

Food-stuffs.

Three algae are collected for edible purposes in the Survey-area; but they
are taken as relishes rather than as articles of food. During times of
scarcity, however, Dillisk and Sloke form a useful addition to the daily menw.
In Clare [sland the only alga which is regularly sold as a commercial article
is Carrageen Moss.

Dillisk and Crannogh.—The Irish Dillisk or Scotch Dulse is the common
Rhodymenia palmata, the fronds of which are chewed in a fresh state or after
having been dried. Crannogh is the small form of the same species found as a
dense short growth on rocks in exposed places (p. 32). The flavour is peculiar
somewhat pungent, but not unpleasant. On Clare Island, Dillisk and Crannogh
are esteemed more highly than Sloke, probably owing to their being less
abundant. On Achill Island, on the other hand, Crannogh is said to be the
most plentiful. :

Sloke (Slouk, Sloukaen, or Sloukaum).—Sloke, the Laver of the English, is
the short crumpled form of Porphyra wmbilicalis, which grows abundantly on
exposed rocks (p. 28). The large flat form is not usually employed, except at
Mulranny, where it is said to be collected and sold to tourists. Sloke is
gathered in spring, and either stewed at once, or boiled into a jelly, and set
aside for future use. When required, this jelly or “laver bread ” is re-cooked,
and then fried with butter. Used on Clare Island and on many parts of the
mainland.

Carrageen or Iceland Moss.—The true Carrageen is Chondrus erispus, but
certain forms of the allied plant Gigartina mamillosa are often included with
it. Both are common on rocky shores ; but they do not occur in such masses
as either Dillisk or Sloke. It is still exported from several districts in Ireland,
and is sold in at least two localities in our area. On Clare Island it is
collected and sold to Dublin, and from thence to Liverpool, where it is
said to be chiefly used for fattening calves. On the small island of Inish-
biggle, four miles north of Achill Bridge, Mr. J. Tydd Frere has successfully
encouraged the collecting of the weed by the peasants. The “Moss” is
mainly bought by a Dublin agent, but smaller quantities are also sold to
private persons in England and the colonies. As observed at Inishbiggle
the weed is left to bleach on the grass, after which it is dried and stowed
away in sacks. For culinary purposes it is boiled down to a jelly, and then

Clare Island Survey—Marine Algae. 15 155

added to milk, or used as a substitute for isinglass. Carrageen is still employed
in some quarters as an antidote for lung-troubles.

The following notes, though referring to a county outside our area, are of
interest. They were supplied by Mr. Thomas Crehan, of Miltown Malbay,
Co. Clare (sometime the home of W. H. Harvey), who, as agent for a firm of
English ship-merchants, has dealt for many years in the sale of seaweeds :—

Crannogh.—Collected at Miltown Malbay all the year round, and sold to
Blackburn at 1s. per stone.

Carrageen.—Sold to London, Scotland, Germany, Russia, and America,
fetching £8 10s. a ton, or 1$ a lb. in America. The narrow form is
used for edible purposes, and the wide form chiefly for dressing
linen, manilla ropes, and other articles.

Sloukaen.—Sold to England for making “laver bread” at 2s. a stone.

4, THE FLorA OF THE BILLs.

Though not so interesting as the terrestrial flora, the marine vegetation of
these rocky islets is worthy of a special note. Nine miles from the main-
land, and surrounded on all sides by deep water, they are subjected to the
severest exposure.

Two algal communities were conspicuous:—the Prasiola association,
covering the bird-cliffs and ascending on the shady side to 50 feet or more
above sea-level, and the Laminaria band, which encircles the islets at low-
water mark. The littoral region is for the most part compressed into its
minimum horizontal range, being in many places nearly vertical. Several
of the more accessible spots were examined. Alaria is more abundant than
L. digitata; and Gigartina forms on almost vertical surfaces a band above.
On the eastern side patches of the Porphyra and of the Callithammon
arbuscula communities were noted on the less precipitous rocks ; but except
for these, other associations appeared to be absent. ‘The full list of species
noted is appended :—

Plectonema tenebrans (in Balanus). Alaria esculenta.

Prasiola stipitata. Laminaria digitata.

P. crispa var. marina. Porphyra umbilicalis.
Enteromorpha compressa. Gigartina mamillosa.

E. micrococca. Chylocladia clavellosa.
Chaetomorpha aerea. Polysiphonia macrocarpa.
Bhizoclonium riparium. Callithamnion arbuscula.
Cladophora prolifera. Ceramium acanthonotum.
C. rupestris. C. atlanticum.
Scytosiphon lomentarius. Lithophyllum incrustans.

U2

15 156 Proceedings of the Royal Irish Academy.

IV.—THE CHARACTER OF THE FLORA.
1. NOTES ON THE NOVELTIES AND ADDITIONS.

As already mentioned, the systematic list contains the names of 437
species and 36 varieties. The revised census, as recorded by Mr. Adams’
private annotated copy, gives the total number of species for Ireland as 464 ;
so that making allowances for 12-15 species which are now regarded as
synonyms or varieties, the Survey list is within fifteen species of that for the
whole of Ireland! As a local list, it must therefore be regarded as very
complete, though amongst microscopic and sub-littoral species additions
doubtless could be made by careful and continuous searching.

The list of additions to Ireland, which consists of ninety-two species and
eleven varieties, is given below. It will be noted that it includes eighteen
species and four varieties (marked +) new to the British Isles, of which the
following five are new to science :—Calothrix endophytica, Codium mucronatum
var. atlanticum, var. nov., Ascocyclus Saccharinae, Fucus vesiculosus vay.

muscoides var. nov., Ptilothamnion lucifugum.

Aphanocapsa pallida. P. Battersil.
Dermocarpa violacea. P. norvegicun.
Pleurocapsa amethystina. Microcoleus chthonoplastes.
Spirulina subsalsa var.* oceania. M. tenerrimus.
Oscillaria margaritifera. Calothrix consociata.
O, Corallinae. tC. endophytica sp. nov.
O. laete-virens. C. parasitica.
O. sancta. C. aeruginea.
Phormidium fragile. Brachytrichia Balani.
TP. persicinum. Microchaete grisea.
+P. subuliferum. Codiolum gregarium.
Lyngbya Meneghiniana. C. Petrocelidis.
+L. confervoides. Protoderma marinum.
L. semiplena. Ulvella fucicola.
L. lutea. Monostroma orbiculatum.
tSymploca dubia. Capsosiphon aureolus.
Plectonema Nostocorum. Enteromorpha prolifera.

1 Some further species would have had to be added if Batters’ Catalogue had been exactly
followed ; butin the systematic section several reductions have been made.
* In this list signifies that the variety only is new to Ireland.

Clare Island Survey— Marine Algae.

E. minima.
Ulothrix consociata.
TU. pseudoflacca.
TU. subflaccida.
Phoeophila dendvoides.
+Rhizoclonium Kerneri/. endozoica.
Cladophora Neesiorum.
Ostreobium Queketti.
Vaucheria coronata.
+Codium mucronatum var. atlanti-
cum var. nor.
tStictyosiphon adriaticus.
Phyllitis zosterifolia.
Streblonema sphaericum.
Ectocarpus clandestinus.
E. microspongium.
E. Battersil.
E. Holmesii.
E. Mitchellae.
Myriotrichia densa.
M. repens.
+Dichosporangium Chordariae.
Mpyriactis stellata.
M. Haydeni.
Leptonéma fasciculatum.
Sphacelaria plumula.
Myrionema Corunnae.
M. papillosum.
M. aecidioides.
M. saxicola.
M. reptans.
Hecatonema reptans.
H. speciosum.
Microspongium globosum.
Chilionema, ocellatum.
Ascocyclus foecundus.
TA. Saccharinae sp. nov.
Lithoderma fatiscens ?

15 157

+Petroderma maculans.

Mesogloia lanosa.

+ Acrothrix gracilis.

Fucus vesic. var. tmuscoides
var. nov.

Erythrotrichia investiens.

E. Welwitschi.

Porphyra coccinea.

Colaconema Bonnemaisonii.

Chantr. virgat. car. *luxurians.
var. ttetrica.

+C. Thuretii.

Harveyella mirabilis.

Gelidium aculeatum.

Callymenia Larterae.

Gracilaria conferv. var. *procer-
rima.

Nitophyllum Bonnemaisoni var.
*crassinervum.

Rhodymenia palm. var. *sarniensis.

Bonnemaisonia hamifera.

Dasya corymbifera.

Spermothamnion Turneri var. tsub-
verticillatum.

tPtilothamnion lucifugum sp. nov.

Bornetia secundiflora.
Seirospora hormocarpa.

7+Ceramium Boergesenii.
+C. atlanticum.

Petrocelis Hennedyi.
Porphyrodiscus simulans.
Rhododermis polystromatica.

Lithophyllum ecrustans var. tsub-

~ dichotomum.
Lithothamnium norvegicum.
L. Lenormandi var. *sublaevis.

L. ‘3 var. *squamulosa.

*In this list signifies that the variety only is new to Ireland.

15 158 Proceedings of the Royal Irish Academy.

(u) Additions to the British Isles.—With regard to these, the following
nine are inconspicuous species which are probably to be found in England
and Scotland if carefully searched for :—

Phormidium persicinum, Ulothrix pseudoflacca.
P. subuliferum. Dichosporangium Chordariae.
Lyngbya confervoides. Petroderma maculans.
Symploca dubia. Chantransia Thuretii.

Ulothrix subflaccida.

Of the remainder :—

Calothriz endophytica sp. noy., is conspicuous on salt-marshes, and should
be searched for in Britain.

Rhizoclonium Kerneri forma endozoica forms green masses in the sponge
Halichondria, and probably occurs in England.

Codium mucronatum var. atlanticum.—This species is new to Europe. It
does not occur in the south of England, but is recorded in the present report
from south-west Scotland, Isle of Man, and the Orkney Islands, in addition to
the north, west, and south-west of Ireland.

Stictyosiphon adriaticus.—Rare, and only obtained by dredging. It should
be found in quiet bays on the south coast of England. °

Acrothrix gracilis. — Probably very rare. Perhaps overlooked as
Mesogloia Criffithsiana.

Fucus vesiculosus var. muscoides, var. nov.—This variety has never been
noted in England. It is probably confined to peaty shores.

Spermothamnion T'urneri var. subverticillatum.—1 have not observed var.
subverticillatum in England ; but it doubtless occurs in quiet bays on the south
coast, since it is known from France. In Clew Bay it is frequent throughout
spring and summer.

Ptilothamnion lucyfuywm.—Caves are frequently explored by algologists ;
but this beautiful microscopic species has hitherto escaped detection. It
is allied to Ptilothamnion micropterum, which is only known from the
Canary Islands and Guéthary (Basses Pyrénées). Probably a southern
species.

Ceramium Boergesentt.—Doubtless common in England, but passed over
as C. decurrens.

C. atlanticum.—This pretty and fairly well-marked species probably
occurs in England and Scotland. A few specimens only were found on
Clare Island.

Lithophyllum inerustans, var. subdichotomum.—Identified correctly for the
first time by Dr. Lemoine, in the present report. Only known in the

Clare Island Survey— Marine Algae. 15 159

British Isles from Clew Bay and Roundstone. It is doubtless dependent
upon a very special type of ground.

(6) Additions to Ireland.—On examining the additions to the Irish flora
we find that a large proportion are minute or critical species which require
careful search and microscopic examination. In earlier days the west coast
list was well up to date, but in recent years, when algology in our islands
has been at a low ebb, the Irish seaweeds have been neglected, and the
numerous microscopic species discovered in other countries have not been
searched for in Ireland. Johnson added many to the Phoeophyceae some
twelve to fifteen years ago; and Adams more recently has recorded additions
to various groups. Batters’ Lambay list ('07) furnished twenty species new
to the Irish. flora.

In the present account the Myrionemaceae are specially well represented,
owing dotbtless to a knowledge of their appearance in the field, gained
during four to five years monographic work on the group. With the
exception of the exceedingly rare Ascocyclus hispanicus, all the British species
were found during the Survey. Several require particularly close observation,
and have only been recorded once or twice previously for our islands.

Amongst the more interesting plants new to Ireland, we may mention,
in addition to those already alluded to :—

Cladophora prolifera —A very distinct species collected on The Bills.
In the British Isles, known previously from Weymouth only.

Monostromea orbiculatum.—A salt-marsh species found in beautiful condition
on Annagh Island.

Capsosiphon aureolus.—Found at the mouths of fresh-water streams.
Hitherto known only from Scotland, but probably overlooked.

Vaucheria coronata.—Forming zones and broad associations, of a deep
green velvet appearance. HExceedingly abundant in Clew Bay.

Ectocarpus clandestinus.—Probably rather rare. Fine material gathered
on Clare Island in October, 1910.

E. Holmesti.—Under the bridge at Achill Sound and in caves, Found on
several occasions with both kinds of fruit and in beautiful condition.

EL. microspongium.—Very inconspicuous, forming minute cushions on
crusts of Ralfsia.

Mesogloia lonosa.—Dredged in Clew Bay in 1909. A most distinct species,
but rare and little known. ,

Porphyra coceinea.—Probably short-lived. Known from four localities
only in the British Isles. ;

Gelidium aculeatum.—Formerly regarded as a form of G'. cornewm.

15 160 Proceedings of the Royal Trish Academy.

Bonnemaisonia hamifera.— Usually considered to be an alieh species from
Japan (see p. 136). rt sel
Dasya corymbifera.—A sub-littoral species. Known in England from
Dorset and the Channel Islands only.
Bornetia secundiflora.—One of the most interesting additions. Head-
quarters in the Mediterranean (See p. 141). ;
Seirospora hormocarpa.—Rare, but easily mistaken for other species ;
hence perhaps overlooked. 48
Lithothamnium norvegicum.—Probably not uncommon in Ireland, but

regarded in the past as a variety of ZL. caleareum.

2, THE CHARACTER OF THE FLORA.

The flora of Clare Island and Clew Bay resembles that of the south-
west of England, and is thus of a distinctly southern type. A number
of species occur which have not been found in Scotland, the east and south-
east of England, or Wales, though it must be remembered that much of the
shore of our east coast is unsuitable for a littoral flora, and that Wales has
been very little explored. Many species in the list are known only from the
south and west coasts of Ireland, but here again further exploration would
probably show a wider range.

Notes as to Absentees.

Before attempting to analyse the flora, a few remarks may be made on the
larger algae which were to be expected, but which were not met with during
the Survey. Of species known to occur in several parts of Ireland, the follow-
ing may have been overlooked, since they are rare or only occur sparsely :—

Asperococcus compressus. Helminthocladia purpurea,
Arthrocladia villosa, Gigartina acicularis.
Achinetospora pusilla. Daysa ocellata.

Porphyra miniata. Pleonosporium Borreri.

Bryopsis hypnoiles is a more noticeable absentee, as when present it
is usually plentiful. The same may be said of Nitophyllum Gmelini and
NV. Hilliae, both of which are known from counties Cork, Kerry, and Clare,
and also from Belfast Lough. Clew Bay would appear very suitable for their
growth, and as their season is a fairly long one, we. must conclude that if
present they are very rare. In Plymouth Sound they are found in
abundance. Naccaria Wiggiit also was not seen in any of the dredgings.

Clare Islund Survey—Muarine Algae. 15 161

At the same time it should be remembered that several large and conspicuous
species were found only once.

Of southern algae, Callithamnion tetricum may be safely stated to
be absent. This coarse, shaggy species is known from Munster and
Leinster, and from the southern counties of England.’ Its habitat—steep
sides of rocks—was carefully searched on each visit, but without success.
There appears to be no record north of Bantry. Halopithys pinastroides
is certainly absent,* and probably Pterosiphonia complanata. With regard to
northern species, Odonthalia dentata and Rhodomela lycopodioides® are wanting.
They are found in Ulster, but do not extend far down the west coast.
Monostroma fuscum was searched for in vain, probably for the same reason ;
it is abundant in Belfast Lough, and many parts of Clew Bay offer similar
ground.

Of very rare species, Stenogramme interrupta, a singular plant found in
many parts of the world, and which occurs in the south of England, and at
Cork and Portaferry (Co. Down), was not found in any of the Clew Bay
dredgings. By some it is regarded as an alien on our shores. A special search
was made amongst the Fuci, but nothing approaching the curious Fucus
anceps Harv. and Ward, of Kilkee was seen. Spyridia filamentosa should also
be mentioned. This is locally abundant on the south coast of England, and
in Wales reaches as far north as Holyhead; yet in Ireland it is unknown:
A single specimen was found amongst dried material brought home from Achill
in July, 1909; but as the plant was never observed during the Survey, there
can be little doubt that it was an English specimen which was taken over to
Achill with the drying paper.

Analysis of the Flora.

An attempt was made, but without much success, to classify the Clare
Island flora after the method adopted by Bérgesen and Jénsson (05). These
authors recognize five groups, arctic, sub-arctic, boreal-arctic, cold-boreal,
warm-boreal, and have with much care classified the arctic and northernmost
Atlantic floras according to this scheme. But the Clare Island investigations
will probably tend to modify the views held in some cases; and in assigning
plants to groups such as these, the personal factor cannot be eliminated. A
great many Irish species do not fall into any of the five divisions, owing to the
fact that the flora contains elements which belong to more southern regions.
These species it is by no means easy to classify, chiefly on account of the

1! The Cromer record in Batters (’02), is probably incorrect.

The Irish records of this plant require confirmation.

* Adams gives a Munster record for R. lycopodioides ; but the case should be re-investigated.
B,1.A. PROC,, VOL. XXXI, x 15

15 162 Proceedings of the Royal Irish Academy.

scarcity of records. The fact that the Survey has added about 250 species to
Connaught, and over 100 species and varieties to Ireland, shows how little we
really know of the distribution of algae. The south-east of Ireland needs
special attention ; also south-west Wales, north Cornwall, and the Scilly Isles.
Borgesen has pointed out how badly the Shetland algae are in need of
re-investigation (’05, p. 787 ; see also 03); and the same applies with equal
force to north-west Scotland. For Donegal and the coast-line generally
between Achill and Portrush there is hardly a record; and yet it is along this
coast that the southern species disappear and the northern forms, such as
Odonthalia dentata, Porphyra miniata, and Monostroma fuscum, begin to show.
With regard to France and Spain, although we have good French handbooks,
additions to the flora may still be made ; and were it not for Sauvageau’s two
valuable lists (97), which are admittedly preliminary, we should have
practically no reliable data for the north of Spain.

For the above reasons I have not attempted to classify the whole flora
into definite phytogeographic groups. We may, however, recognize certain
well-marked elements, and by means of these attempt to analyse it.

(a) Southern Hlement.—Of the species which have a markedly southern
distribution, the following are among the most noticeable :—

Cladophora prolifera. Bostrychia scorpioides.
Codium adhaerens. Chondria tenuissima.
Mesogloia lanosa. Polysiphonia subulifera.

M. Griffithsiana. P. furcellata.
Petrospongium Berkeleyi. Dasya corymbosa.

Cutleria multifida. Spondylothamnion multifidum.
Bifurcaria tuberculata. Halurus equisetifolius.
Cystoseira ericoides. Monospora pedicellata.

C. granulata. Bornetia secundiflora.
Taonia atomaria. Callithamnion granulatum.
Dictyopteris nembranacea. C. tripinnatum.

Nemalion elminthoides. Compsothamnion thuyoides.
Callymenia reniformis. Schizymenia Dubyi.
Bonnemaisonia hamifera. Corallina squamata.

We may mention also eight species which were not found during the
Survey, but are known to occur in 8.W. Ireland :—

Asperococcus compressus. Nitophyllum Gmelini.
Helminthocladia purpurea. Pterosiphonia complanata.
Gigartina acicularis. Dasya ocellata.

Nitophyllum Hilliae. Callithamnion tetricum.

Clare Island Survey—Marine Algae. 15 163

Nearly all the above species are confined in England to the southern
counties. Several have been found only in south Devon and south Cornwall ;
others reach as far as the Isle of Wight; whilst a small number extend
through the Straits of Dover as far north as Norfolk. All are known to occur
in Normandy or Brittany, and with few exceptions they have been recorded
by Sauvageau from the Bay of Biscay and north Spain. Though their head-
quarters are in a southerly direction, a few extend up the Irish Channel to
Anglesea and the Isle of Man; and several have been noted in the Clyde area
and in the Orkney Islands. The Clyde has been thoroughly worked (see
Batters, 91); hence numerous outliers have been detected. The Orkney
records are distinctly interesting, and tend to show that some of the southern
forms in the west Irish flora extend northwards by way of the Hebrides. For
this the Gulf Stream drift is doubtless responsible.

The plants listed above grow luxuriantly in Ireland, and are evidently at
home in their surroundings. The much-indented coast supplies great variety of
conditions ; and the lack of intense insolation in summer permits the presence
of a better littoral and shallow sub-littoral vegetation than in the south of
England. Several of the species are only found sparingly, as in other parts of
our islands ; but others occur in great profusion—e.g., Petruspongium Berkeleyt,
Dasya arbuscula, Polysiphonia subulifera (local), and Corallina squamata ;
whilst Codiuwm adhaerens, Cutleria multifida, Bifurcaria (at Roundstone),
Cystoseira fibrosa, Halurus, Monospora pedicellata are very frequent. The
abundance of Dasya arbuscula at low-water mark on Clare Island is very
remarkable (see Phye. Brit., tab. 274).

(b) Northern element.—With regard to northern forms we find that there
occur in our area a large number of the species which Borgesen and Jénsson
place in their sub-arctic and boreal-arctic groups. Many of these have, how-
ever, a very wide distribution, being abundant in all parts of the British Isles
and extending to France and even Spain. Of the most noticeable boreal
species (selecting from. well-known plants only) we may pick out seven for
notice. The first four are annuals,’ and occur chiefly in spring ; the last two
are found all the year round, and are important constituents of the flora.

Stictyosiphon tortilis—Very common in Clew Bay during spring, also in
Scotland. It occurs in Northumberland, Cheshire, and Carnarvon. Batters
gives a Cornwall record; but if it occurs on the south English coast, it must
be extremely rare.

Desmotrichum undulatum.—Common in Clew Bay. Not known from
England, but recorded from several localities in Scotland. It is rather small,

1 The distribution of many of the smaller and inconspicuous species is so imperfectly known that
they are best omitted.

X 2

15 164 Proceedings of the Royal Irish Academy.

so may have been overlooked; but most of the southern records of this plant
prove to be errors for Punctaria tenwissima. It is also known from the
Faeroes, Kiel, and W. Sweden.

Phyllophora Brodiaei. —See note on p. 154. The plant is known from Nova
Zemblya, Spitzbergen, E. Greenland, Iceland, Norway, Sweden, Baltic,
Scotland, N. England, and N. Iveland, and may therefore claim to be a dis-
tinetly boreal species. In Clew Bay it is scarce, but several colonies were
noted at Mulranny.

Lithothamnium norvegicum.—sScattered amongst L. calcareum in Clew Bay
and at Roundstone. Known from Scotland, Norway, Denmark, and the N.
Atlantic coast of N. America. It has not been observed in the Lithothamnium
banks of the English or French coasts.

Inthothamniun compactum.—Madame Lemoine remarks that this is a
distinctly boreal species. It is known from Nova Zemblya, Spitzbergen,
Iceland, Norway, Greenland, and the N. Pacific coast of N. America.

Callithamiion arbuscula.—The presence of this boreal species on the
Irish west coast gives the appearance of a distinct overlapping in the flora.
In the colder waters of the North Sea it is not known south of Yorkshire ;! and
on the west coast of Great Britain it descends to Ayrshire and the Isle of
Man. On Clare Island it is abundant, and forms a conspicuous belt, just as
it does in Scotland, Norway, and the Faerdes. It is recorded by Adams for
Munster and Leinster, and probably extends right round the Irish coast.

Ptilota plumosa.— Another anomaly on the west coast. Listed by Borgesen
as a sub-arctic species and general in Iceland, Nova Zemblya, and Spitz-
bergen, P. plumosa descends as far as Yorkshire on our east coast, and North
Wales and the Isle of Man on the west. In Clare Island it is plentiful on
the stipes of Laminaria Cloustoni, and is washed ashore in company with
such southern plants as Taonia and Caullymenia reniformis. Adams lists it
from Munster and the south of Ireland; but as the older writers often con-
fused the plant with Plumaria elegans, it would be advisable to confirm its
presence in the southern provinces. In the London herbaria, there are no
specimens south of Renvyle (Co. Galway).

(c) Other interesting species—The most noteworthy alga in the list
is undoubtedly Codiwm mucronatum vay. atlanticum. This had either to be
regarded as a new and endemic species, or to be linked with the Australasian
C. mucronatum. The agreement in microscopic structure with the latter was
found to be so close, that it was impossible to do otherwise than regard it as a
form of that species. Its position on the west coasts of the British Isles is, how-
ever, remarkably isolated, as it is not known elsewhere in Europe, nor indeed

‘ Batters gives an Isle of Wight record ; but this is almost certainly an error for C. granulation, a
compact form of which is not uncommon in that locality. _

Clare Island Survey— Marine Algue. 15 165

in the North Atlantic. Itis almost impossible to believe that O. maucronatum
can haye been introduced, as at least one herbarium specimen shows that it
has existed in S.W. Ireland for 100 years. At the same time, the pre-
ference of the plant for well-lighted pools, and the fact that it apparently
disappears in autumn, might be taken as an indication that it is a native of
a warmer region. That it was introduced from the British Isles to Australia
and New Zealand is out of the question. For the present the plant must
remain a remarkable case amongst algae of discontinuous distribution. Its
precise range in the British Isles should be ascertained. When this is known
we will be in a better position to pronounce as to the status of the plant, and
to discover if it is spreading on our shores. From 8. Devon and 8. Cornwall
it is (or was, a few years since) certainly absent, but the same cannot
be said of Wales, as that coast has not been carefully worked. It is abundant
in the Isle of Man; but no records are known from the east and south of
Treland.

The best-known case of an alien alga in the British Isles is that of
Colpomenia sinwosa, which has been kept under observation in France and
England (Sauvageau, ’07, Cotton, ’08, 11). It isa conspicuous plant, and was
first observed both in France and England (Scilly Isles) in 1905. By 1909 it
had spread as far as Hampshire, and it occurs now in great profusion in
many parts of Cornwall, Devon, and Dorset. Colpomenia is specially adapted
for floating; hence rapid colonization is comparatively easy. It affords an
example of a Mediterranean species adapting itself to the conditions of a colder
sea, and becoming naturalized at once. Codiwm mucronatum, on the other
hand, does not readily float, and is probably much less hardy.

Bonnemaisonia hamifera provides another problem. It is known in Europe
from several places in the English Channel, and has always been regarded as
of Japanese origin. By means of its hooked branches it clings tenaciously to
floating weed, and is thus no doubt capable of being transported for a
considerable distance. Its occurrence on Clare Island was most unexpected,
and raises a doubt as to whether the plant after all is not indigenous to our
islands (see p. 136). On the other hand, there is the noteworthy fact that
it was not noted by McCalla nor by any other west-coast collector, and that
until 1895 it was unknown in Europe. If an introduction, it can hardly
have come direct to the west of Ireland; but as nothing is known as to its
presence or absence in the southern provinces, it is useless speculating as to
the method of transport or port of entry.

Questions such as those raised above make us feel our lack of knowledge,
and emphasize the need of further study of our own flora. The vitality and
floating power of detached seaweed are likewise in need of investigation. A

15 166 Proceedings of the Royal Irish Academy.

mere list of species found floating, either of their own accord, or entangled
with débris, would be of interest, and could be easily compiled by those who
spend much time in dredging, tow-netting, etc. The algal growths on the
bottoms of both large and small vessels present, moreover, an almost unworked
field.

3. COMPARISON WITH OTHER AREAS.

East Ireland.—A comparison of the floristic features of the east and west
of Ireland does not reveal so great a contrast as was expected. No special
account of the east-coast flora has been published, nor have I personally examined
any part of the shore, except the extreme north. Adams (’08, annotated copy)
lists most of the Clare Island austral species for Leinster, and a considerable
number for Ulster also. There are, however, ten well-known and conspicuous
algae which have not yet been recorded for the east coast, but most of these
would probably be found in Leinster if carefully searched for. S.E. Leinster is
similar, as to its flora, to Munster; and Ulster has a surprising number of
southern species, Belfast and Larne Loughs being at one time famous for
Nitophylla and other seaweeds which occur chiefly in the southern counties.
At the same time, it would be advisable to confirm such records as Bifuearia,
Callithamnion tetricum, and Schizymenia Dubyi. The real difference between
the east and west coast lies doubtless in the proportion of southern vegetation
present; plants which are common or frequent in Mayo and Galway being
probably rare or very rare in Co. Dublin. The luxuriant growth displayed by
such species as Lomentaria clavellosa and Dasya arbuscula is also a characteristic
feature of the west-coast vegetation.

England and Scotland—With regard to England, as already shown, the
Clare Island flora resembles that of Devon and Cornwall, but in England the
boreal element (represented by Callithamnion arbuscula, and Ptilota plumosa)
is wanting, as are also several other northern species. Codiwm mucronatum is
likewise entirely absent. Such plants as Acrothrix and Stictyosiphon adriaticus,
known at present in the British Isles only from Iveland, will probably be found
in England when our south-coast bays have been more thoroughly explored
by dredging. On the other hand, a few well-known and conspicuous species,
more or less frequent in Devon and Cornwall, have not been found in Ireland.
The most noteworthy amongst these are Punctaria erispata, Gracilaria
compressa, Grateloupia filicina, G. dichotoma, and Spyridia filamentosa, the last-
named being locally abundant in Great Britain, and extending from Sussex to
Anglesea. There are also other species, but these are of very rare occurrence.
The east coast of England is comparatively poor; more than two-thirds of the
species listed on p. 162 are entirely absent ; the remainder have been reported

Clare Island Survey—Marine Algae. 15 167

to occur more or less frequently as far north as Norfolk. When Yorkshire is
reached, the four boreal species, Odonthalia, Rhodomela lycopodioides, Ptilotu
plumosa, and Callithamnion arbuscula, become noticeable and are abundant from
this county northwards. The east of Scotland possesses a similar type of
flora, and additional northern forms appear (e.g. Stictyosiphon, Euthora). The
Orkney Islands, on the other hand, show a southern element, which is
doubtless present also in the Hebrides. Details as to the flora of the Hebrides
and the connexion with S.E. Scotland, N.W. and N.E. Ireland would be of
great interest.

Faeroes.—The British and Faerdese floras have already been elaborately
compared by Bérgesen ('05, pp. 784-788) ; and the Clare Island investigations
do not materially modify his statements. Borgesen naturally was most
concerned with the flora of Scotland and the Shetlands; and in conclusion he
states that “the Faerdese algal flora must be regarded as a rather poor
selection of the algae of Scotland and the adjacent islands, as almost all the
Faerdese algae are found on the coasts of Scotland; whereas Scotland, on the
other hand, has a very great number of species which are wanting at the
Faerées. The greatest resemblance is between the Faerdese flora and that of
the Shetland Islands; the Faerdes have a few, perhaps no more than six,
specially northern species, which will probably not be found in the Shetland
Islands.” The six species referred to are Alaria Pylati, Rhodophyllis
dichotoma, Halosaccion vamentacewm, Ptilota pectinata, KRhodochorton
penicilliforme, and Lithothamniwm Ilaeve. Of these the Rhodochorton has
since been recorded as British (Batters, Journ. Bot., 06, p. 3); and a
somewhat doubtful record of Z. Jaeve exists for Ireland. The first four,
however, could not easily be overlooked; and it is very unlikely that they
extend as far south as the British Isles. With regard to Ireland, other
species might be added to Borgesen’s list, as several which he assumes may be
found in the north of Scotland will hardly descend to Ulster; and Mucus
inflatus, Huthora cristata, and Antithamnion floccosum, known on the east of
Scotland or Shetland, have never been found in Ireland. The curious over-
lapping of north and south in the algal flora of the west of Ireland consists,
as one would expect, in a continuous southern extension in the range of
certain boreal species rather than in the presence of isolated patches.

France and Spain.—The flora of France and the Bay of Biscay is of special
interest, and may be outlined here. The species found in Normandy and
Brittany are practically the same as those of Devon and Cornwall, though
doubtless in Brittany the southern element is present in greater quantity.
South of the Loire the flora undergoes a change; and in the Biarritz and
Guéthary neighbourhood it possesses a decidedly southern facies, Fucus and

15 168 Proceedings of the Royal Irish Academy.

Ascophyllum are practically absent from Biarritz, and such plants as
Spathoglossum Solierti and Liagora viscida ave of frequent occurrence.
On the north coast of Spain these southern species cease to flourish ;
and a vegetation of the Brittany type re-appears. At Cape Ortegal
the flora changes again; and, by the advent of such algae as Phyllavia
purpurascens and Laminaria pallida, it receives a stamp which is
characteristic of Cadiz and Morocco (see Sauvageau, 97). There appears
to be no element in the Irish flora which is specially characteristic of
the Spanish peninsula. Many species are common to both countries; but
these for the most part extend right up the coast of France, and are also
to be met with on both sides of the English Channel. The Biarritz neigh-
bourhood is peculiar in possessing a flora of particularly austral type.

Neither is there any evidence of a S.W. France or Mediterranean
element, such as is represented amongst flowering-plants by Dabeocia and
Erica mediterranea. The two Mediterranean algae for which the west of
Treland was specially noted were both wrongly named; and a third less
familiar species, with the same geographical distribution, has had to be struck
off the list. The record of Codiwm elongatum (a native of the South of France
and North Africa) was anerror for C. mucronatum; Lithophyllum dentatum (a
species not known outside the Mediterranean) must be replaced by
LL, incrustans var. subdichotomum (teste Lemoine, p. 146); and Peyssonnelia rubra,
though still a puzzle, was certainly an erroneous determination. The last-
named has been recorded from many warm-temperate and tropical regions,
often incorrectly. It was originally described from the Ionian Islands, and
in the British Isles was supposed to occur at Roundstone and Plymouth.
The species of the genus are singularly difficult to differentiate ; but whatever
the Irish plant may be, it is clear from an examination of the type specimens
that it is not P. rubra. On the other hand, Bornetia secundiflora, which is
abundant in the Mediterranean, and found sparingly in Brittany, Devon, and
Cornwall, and more frequently in west France, may be added as a rare
plant to the west-coast list. ‘The majority of the southern species listed for
Clare Island appear to have their headquarters in S.W. England, W. France,
and N. Spain, rather than in southern Europe.

4. ORIGIN OF THE FLORA.

The origin of the algal flora at present found in the Survey area isa
subject as to which we have very little to guide us. The source of the Clare
Island flora as distinct from the mainland presents, of course, no difficulty,
whatever view be taken as to the date and manner of the formation of the
island. But any theory as to the origin of the marine flora of the west of

Clare Island Survey —Marine Algae. 15 169

Ireland must be highly speculative, since our knowledge of the rapidity with
which algae extend their range is very meagre, and fossil evidence (with
regard to our area) is absolutely wanting. For this reason the most important
data are those furnished by the study of the general distribution of the species,
and by a recognition, if possible, of the presence of any definite phyto-
geographic groups. Borgesen ('05, p. 805) has summarized the views
propounded by Kjellmann and Reinke as to the origin of the North Atlantic
algal flora, which, in a word, is said to consist of a mixture of old atlantic and
arctic elements. The question of the survival of plant-life in Ireland during

‘the Ice Age, as to which there is so much difference of opinion, I leave to
others, and will confine my remarks to phytogeographic observations, and to
features in the Clare Island flora which appear to be of interest. Such may
be of service to those engaged in the study of the antecedents of the present
Trish fauna and flora.

Although the flora contains a decidedly larger proportion of southern
forms than corresponding areas in England and Wales, there appears to be no
element, such as is found amongst Phanerogams, which is strikingly austral.
The southern species extend, probably without exception, along the south
Irish coast, and are found in Devon, Cornwall, and Brittany ; many also
occur in the Bay of Biscay and on the north coast of Spain. Their range
being continuous is, therefore, not remarkable. No notably Spanish or
Mediterranean species are found. A boreal element of a special character is,
on the other hand, recognizable, the abundance of Callithamnion arbuscula and
Ptilota plumosa being very striking in an area where the general facies is of
a much more southern type. Neither of these species occurs in the south of
England, nor have they been recorded south of Yorkshire and Anglesea.
Their position on the Irish west coast is, however, not isolated, but is merely
a continuous southern extension of their range. But, as a result, there is in
the marine flora, as in the terrestrial, a distinct mingling of north and south.
Other boreal algae might be mentioned; but these are not so abundant, nor
has their distribution been so carefully ascertained.

The presence on the west coast of Iveland of a boreal element which is
absent from the south of England, is a familiar problem to the Irish botanist.
In the case of the algae cited above, the question of a land-connexion between
England and Ireland need not be discussed, since the plants already occur in
the northern part of Great Britain. It would appear, therefore, that the
climatic or other conditions of the southern counties are unfavourable for the
growth of these species. With regard to climatic factors, it is well known
that extremes are more important than the mean; and from this we might

conclude that, in the equable climate of Ireland, the maximum temperature
B.I.A, PROC, VOL. XXXI. ny 15

15 170 Proceedings of the Royal Irish Academy.

which the plants can endure is not reached during summer, but that in the
south of England this point is exceeded. The meteorological office reports
show, however, that though the atmospheric temperature in 8.W. England
exceeds in summer that of S.W. Ireland, the sea-temperature is practically
the same. The temperature factor then may explain the absence of the
littoral C. arbuscula, but hardly that of the sub-littoral Ptilota. The physical
nature of the coast has also to be considered. Both the algae mentioned
require rocky ground. Ptilota grows on the stipes of Laminaria Cloustont (a
stout species demanding a very firm bottom) ; and C. arbuscula is found only
on exposed rocks in the littoral region: from shores of sand, shingle, or soft —
rock they would therefore be absent. On the east of England, stretches of
hard rock in the four counties immediately south of Yorkshire are very scarce;
and it is most probable that both plants would extend much further south
were such rocks available. For Wales and §.W. England, however, this
difficulty does not exist.

Another theory that presents itself is the possibility that, owing to more
recent geographical changes in the English coast-line, C. arbuscula and
P. plumosa are still advancing in the Irish and North Seas, and that they have
not yet reached their southern limit. The conditions (e.g., currents, nature of
coast, ete.) may have been less favourable to their progress than in Ireland.
This, however, is improbable, as the dispersal of marine algae by spores
appears to be an easy and comparatively rapid process. Ptilota, moreover, is
readily transported, being found washed ashore in abundance, and often in a
bleached state. Such specimens (which are possibly of distant origin)
frequently possess cystocarps containing presumably healthy spores. Currents
do not appear to offer any resistance to the southern advance of algae in the
Trish Channel.

From these considerations it is probable that the geographical theory does
not meet the case, and that ecological factors are more likely to explain it. If
this be so, the scarcity of hard rocks may have limited the range of these
boreal species in the North Sea; and a high summer temperature may have
prevented Callithamnion arbuscula from settling down on our south-west coast.
Ptilota remains a puzzle. Numerous points present themselves which would
be worthy of inquiry; but with its precise distribution in Wales and Ireland
uncertain, these must be left for future consideration.

The only geographic types recognized worthy of discussion here are the

‘The ayerage sea-temperatures for the past five years for Seafield (Co. Clare) and Plymouth
during the summer months are almost identical. But during 1911 the Plymouth average from
July 15 to September 9 was distinctly higher. The more eastern counties (Kent, Sussex) possess a
much higher sea-temperature in summer than Deyon and Cornwall.

Clare Island Survey —Marine Algae. 15 171

austral and southern elements dealt with above; but a further word may
be said as to the comparison between the east and west coasts of Ireland.
As far as can be seen from records, and from a study of herbarium material,
the east-coast flora is characterized not so much by a poverty of species
as by a smaller proportion of the austral element, and by a lack of the
special luxuriance characteristic of the west. It appears useless at present
to attempt to pronounce an opinion as to the origin of the species on
either coast. The fact that Colpomenia sinuosa can suddenly appear in
Brittany and Cornwall, and in the course of a few years be completely
naturalized over a very large area on both sides of the English Channel,
proves how quickly changes may take place, and how easily we may err in
discussing the age and history of a flora,

There remain two isolated species to be noted. Bonnemaisonia hamifera,
a fairly conspicuous and unmistakable alga, is elsewhere in Europe known
only from a few stations on either side of the English Channel. It occurs
in the North Pacific (Japan and California), and has usually been regarded as
an alien in this country. The plant is dealt with on p. 136; but nothing can be
stated as to origin in Clare Island, owing to our complete ignorance of its
range in Treland.- Codium mucronatum var. atlanticum is even more note-
worthy. So closely allied to the New Zealand form of the species as to be
almost inseparable from it, and yet unknown in the northern hemisphere
except in the British Isles, its distribution is certainly remarkable. As far as
is known, it does not occur in England, but has existed in Scotland for at
least seventy years, and in Ireland for upwards of a hundred. Its precise
range has not yet been ascertained. Until each species of our flora is
recognized, and until its range is accurately determined, plenty of work
remains for the systematic algologist. Common species need not be despised.
On Clare Island some of the most abundant and conspicuous algae have
proved the most interesting ; and yet, owing to lack of data concerning their
distribution, we are hampered in drawing theoretical conclusions.

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15 176 Proceedings of the Royal Irish Academy.

DESCRIPTION OF PLATES.
Prate I.

Porphyra umbilicalis association on south shore of Clare Island in July
(1910). The Porphyra belt at this spot takes the place of Fucus spiralis, and
occurs between the bands of Pelvetia and F, vesiculosus, var. evesiculosus. It is
thus somewhat higher than usual. The shore is exposed and rather steep.

PuateE II.

Boulder-beach between Portlea and the lighthouse, showing broken char-
acter of zones and associations. The Pelvetia belt is practically absent, and
the zones of Fucus spiralis and F. vesiculosus which follow are interrupted and
discontinuous. In the foreground Himanthalia with the usual undergrowth
of Laurencia pinnatifida is seen, and also the beginning of the /. serratus
vegetation. Gigartina joins the Laurencia band in the lower levels, and
Rhodymenia palmata hangs from the shady sides of boulders.

Priate III.

Shallow rock-pool on south shore, half-tide level. Showing more or less
continuous covering of Lithophyllum inerustans with characteristic lip-like
protuberances (centre). Several tufts of Polysiphonia fruticulosa occur, and
in the upper left-hand corner Corallina officinalis and the more southern
C. squamata ave seen together. To the extreme right is Polysiphonia Brodiaet
(upper corner). In pools of this kind small plants of Codiwm mucronatum
var. alanticum ave frequent.

Puate IV.

“Coral beaches” in Mannin Bay, Co. Galway. The white sand of the
beach is composed of finely broken fronds of Lithothamnium calearewm, which
are washed ashore from the Lithothamnium association in the Bay. In some
beaches a few rocks are present, but these are largely devoid of algae (fig. 2).
The weed washed ashore in foreground is Zostera. Photographed at low-

water by Dr. G. H. Pethybridge, October, 1911.

PLATE V.

Fic. 1.—Lithothamnium sand from Mannin Bay. Medium-grained sand
frem the middle part of the beach (nat. size). At high-water mark the sand is
very coarse, and contains shells and Zithothamnium knolls; at low-water it is
extremely fine, and its origin is hardly discernible without a microscope.

Clare Island Survey— Marine Algae. 15 177

Fic. 2—“Fueus farm” in Achill Sound. Photograph of Blind Sound
(near Darby’s Point) at low-water, showing stones with growth of Fucus. The
stones are set out (often in regular rows) by the cottagers, and become rapidly
colonized by Fueus vesiculosus, which, at the end of the second season, is cut

for use as manure.
PuaTE VI.

Fucus vesiculosus var. muscoides var. nov.

Fic. 1.—Dried specimens of individual plants (slightly less than natural
size). The specimens in the two upper rows are from the dense mossy growth
seen in fig. 2; those from the lower are from the margins of such growth,
where increased space and moisture allow of better development. In the
lowermost specimen to the right two male receptacles are recognisable.

Fig 2.—Small piece cut out from var. muscuides sward in Achill Sound.
The sward forms a narrow irregular zone in several parts of the Sound. It is
more or less mixed with Statice maritima, Glyceria maritima, Salicornia,
spp., etc., and in the month of May is particularly attractive, owing to the
bright pink flowers of the first-named. Photo by Mr. G. Massee of tuft
brought back to Kew (slightly reduced).

Puate VII.

Codium mucronatum var. atlanticum var. nov., with a fragment of
C. tomentosum (nat. size). The drawings are made from dried specimens ;
but the thick branches and robust habit of C. mucronatum are noticeable. In
the living state the plants can readily be distinguished by this character; but
in dried specimens it is necessary to examine the utricles.

PuLate VIII.
Utricles of Codium mucronatum and C. tomentoswn.

1-2. C. tomentosum. Showing short utricles with the cell-wall thickened at
the apex. (Clare Island, Oct., 1910.)

3. C. mucronatum var. atlanticum var. nov. Showing utricles double the
length of those of C. tomentosum, and considerably wider ; apex even
or mucronate ; not thickened as in C. tomentosum. (Giant's Causeway,
May, 1910.)

4. C. mucronatum vax. atlanticum var. noy. Note drumstick utricle
specially frequent in old plants. (Clare Island, April, 1909.)

5. ©. mucronatum vax. atlanticum var. noy., with gametangia (¢ ). (Roonah
Quay, June, 1910.)

R.I.A. PROC., VOL. XXXI. ZL 15

15 178 Proceedings of the Royal Irish Academy.

6.

ee)

bo

3.
4.
5.

1.

10.

11.

C. mucronatum var. Novae Zelandiae. Note similarity of utricles to those
of the Irish plant. (New Zealand, Herb. Kew.)

C. mueronatum var. tasmanicum. Apex of utricle very pointed.
(Tasmania, Herb. Kew.)

C. mucronatum var. californicum. Mucro long, blunt; often apparently
articulate. (California, Herb. Kew.)

PuatEe IX.
Ptilothamnion lucifugum sp. nov.

Decumbent and upright fronds, showing irregularly produced branches
and pinnae. (xc. 15.)

Part of a branch showing pinnae and forked pinnulae. The pinnae are
occasionally opposite; but usually the opposite pinna remains
practically undeveloped. (x 80.)

End of pinna. (x 140.)

Pinnulae with antheridia. (x 140.)

-6. Part of decumbent branch showing rhizoidal pinnae, which occasionally

terminate in a more or less discoid expansion. (x 140.)

PLATE X.
1-2. Calothrix endophytica sp. nov.

Portion of Enteromorpha frond showing Calothrix filaments within the
cavity. (x 400.) 2. Cluster of short filaments, with the basal
heterocysts (normal). (x 500.) 3. Longer filaments, with basal and
intercalary heterocysts. (x 500.)

4-9. Ascocyclus Saccharinae sp. nov.

Discoid thallus, easily separable into filaments. 5. Assimilating
filaments and young ascocysts. 6. Assimilating filaments and
young sporangia. 7. Sporangia and hairs, with basal sheath.
8. Sporangia, and two empty ascocysts. 9. Two ascocysts with
contracted contents. (x 400.)

Nitophyllum wneinatum J. Ag., showing irregular fronds and acuminate
branches. (Dried specimen, nat. size.)

NV. laceratum var. uneinatum Grev. Quite distinct from the last, bemg
merely a variety with uncinate branches of the common J. laceratum
(nat. size).

PLATE XI,

Map of the Clare Island District.

Proc. R.I.AcaD., VoL. XX XI. Par? 15, Prare [.

The Porphyra association of exposed shores, Clare Island. R. Welch, photo.

CLARE ISLAND SURVEY.—COTTON: MARINE ALGAE.

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Proc. R.I.AcAD., VOL. XXXI. PART 15, PLATE II,

(aera eR San CMe at ene och Cie cna aMI a|

Boulder Beach at Portlea, showing discontinuous zonation. R. Welch, photo.

CLARE IsLAND SURVEY.—COTTON: MARINE ALGAE.

Lani

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Proce. R.T.AcCAb., VoL. NXXIT. PART 15, PLATE IV.

Fic. 2. G. H. Pethybridge, photo

“Coral Beaches” in Mannin Bay. Sand composed of broken fronds of Lithothamnium calcarewm.

CLARE ISLAND SURVEY.—COTYON: MARINE ALGAE.

PART 15, PLATE V.

Proc. R.J.ACAD., VoL. XXXI.

G. H. Pethybridge, Ahozo.

Fic.

1.—Lithothamnium sand from beach in Mannin Bay.

T. J. Westropp, phozo.

2.—Fucus farms in Achill Sound.

Fic.

MARINE ALGAE.

CLARE IRELAND SURVEY.—COTTON:

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Proc. R.I.ACAD., VOL. XXXI. Parr 15, Prare VI.

FIG. 2: G. Massee, fho/o.

Fucus vesiculosus var. muscotdes var. nov.
Fig. 1.—Individual plants. Fig. 2.—Sward formed by the same, with scattered plants of
Statice maritima.

CLARE ISLAND SURVEY.—COVTON: MARINE ALGAE.

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Proc. R.I.AcAD., VOL. XX XI.

Part 15, Pate VIII.

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1, 2 Codium tomentosum.

3-5 C. mucronatum var, atlanticum.
© 56 on ,, Novae Zelandiae.
Wf ep 50 3 tasmanicum.
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1-3. Galothrix endophytica sp. nor.

4-9. Ascocyclus Saccharinae, sp. nor.

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10. Nitophyllum uncinatum ,

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Map of the Clare Island District.

MARINE ALGAE.

CLARE IsLAND SURVEY.—COTTON :

SMITHSONIAN
INSTITUTION

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ROYAL IRISH ACADEMY
CLARE ISLAND SURVEY
SCHEME OF PUBLICATION — ay

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Vol. XXXI of the Proceedings of the Academy. ]

Grnerat Description, anp Narrative. BR. Ll. Praeger. ane
History anp Arcuaronocy. T.J. Westropp. 78 pp. 10 plates. 4s.
Prace Names. John MacNeill. T. J. Westropp.

Gartio Puant anp Antuan Nawms. N. Colgan. 380 pp. 6d.
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Mersorotocy. W. J. Lyons.

Guotoey. J. R. Kilroe. TT. Hallissy.

Peat Deposirs. F. J. Lewis.

Tree-Growrg. A. ©. Forbes. Ses
Pzanerocama ap Preriporayra. R. Li, Praeger. 112 pp. 6 plates. 4s.
Musor. Rey. Canon Lett.
Hepatioar, Rey. Canon Lett. RR a SEK
Foner. Carleton Rea. Sir H.C. Hawley. 26 pp. 1 plate. 1s.
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Av.cas—Marme. A, D. Cotton. 178 pp. 11 plates. 5s.
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Reprmaa ano Ampusta. RB. F, Scharff. 4 pp. 6d.
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Dierera. P. H. Grimshaw.

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Coroprera—Aguatic. F. Balfour Browne. 20 pp. 6d.

Hewmerera, J, N. Halbert. 10 pp.
Oxrnorters, Prof. G, H. Carpenter. 4 pp:
; [For continuation see page 4.

| 6a,

i: om 2B rok: ed H. Carpenter. Hs
Ananerpa. 'D, R, Pack Beresford. 8 pp
Puaraneipa. D. RB. Pack Beresford. 2 PP.
Anoriscowa. James Murray. 16 pp., 8 plates)

a Psevposcorerones. H. Wallis Kew. 2pp. §

%& 391 Acarmuna: i—Hypracarmwa. J.N, Halbert.
39ii Orneg Acsnmipa. J.N. Halbert. —

% 40 Descarops. G.P.Farran. Spp. Nell ai

% 441 Sonrzoropa anp Cumacua. 'W. M. Tattersall. 10 pp.

' 2 “Ampmrropa. W. M. Tattersall.

* 43 Isopopa—Marmn. W. M. Tattersall. 6 pp. 1 Ga.

%* 4% Tsoropa—Trrnesrran. N. H. Foster. ‘4 pp.’

4§ Ewromosrraca—Maning. G, P. Farran.

% 46 Enromosraaca—Fresuwares. D. J. Scourfield, 18. pp. 1 plate
Potyowanrs anp Ancurannenipa. R. Southern.
Oxicoonsrrs. BR. Southern.

-Guenvrea, RB. Southern.

Himvowea, BR. Southern.

‘Rommera (excluding Bozxroma). OC. F ‘Ronaselot.. 10 a)
Rorirera Borinoma, James Murray. 20 pp. 1 igs
Ponyzos, A. R. Nichols. 14 pp. | 6d,

Nemarserana ann Crarrosnataa. BR. Southern. G. 0. She:
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Praryuenmra. R, Southern. 18 pp. 6d. .
Eonmwonermara. A. R, Nichols. 10 pp. - aoe
CopbLentTERata. Miss a: aegnyes 10 pp.

ieadeass I. §. Dunkerly.

Fuacetzara, J. 8. Dunkerly.

Mycrrozoa.. Miss Lister. 20:pp. 6d,

Forauinirera, Edward Heron- Allen. Arthur Bacland. as

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Nores on Manine Pranzron. G, P. yeaa
‘Summary on Magiwe Distmeunon. Re Bouthern.
Susnary ON bein 26s efunels ice

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