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Lichenologist
21(3):
229-236 (1989)
MACENTINA STIGONEMOIDES
(VERRUCARIACEAE),
A NEW
LICHENIZED
SPECIES FROM GREAT BRITAIN
AND
IRELAND
A. ORANGE*
Abstract:
Macentina stigonemoides
sp.
nov. is described from trees
in
Great Britain
and Ireland;
it is
characterized
by a
filamentous
to
granular thallus with papillose
cortical cells and pale perithecia with
3-5-septate
spores.
Introduction
Since the description of the genus
Macentina
and its type species
M.
perminuta
from leaves
in
West Africa (Vezda 1973), three additional species have been
added
to
the
genus:
M.
abscondita
on
Sambucus
in south-east England (Coppins
& Vezda 1977),
M.
hepaticola
on
epiphyllous hepatics
in
Zaire (Dobbeler
&
Vezda 1982)
and M.
aurantiaca
on
Sambucus
in
Ireland (McCarthy & Vezda
1985).
The
last has been shown
to be a
species
of
Nectria
(Orange 1989).
The
present paper describes a fifth species which
is
widespread
but
overlooked
in
Great Britain and Ireland.
Materials and Methods
Material
to be
viewed
in
the SEM
was
soaked in water, dehydrated through
an
alcohol
series,
dried
in a Tousimis Samdri-780 Critical Point Drying Apparatus, coated with gold
in an
Emscope SC500
Sputter Coater, and viewed in
a
Jeol JSM-T100 scanning electron microscope.
The Species
Macentina stigonemoides A. Orange sp.
nov.
Thallus pallidus viridis, filamentosus, 50-400(-600) um altus, dense ramosus; rami cylindrici,
pseudoparenchymati, 12-35 um lati, cellulae saepe papillis conicis instructus. Rami saepe
in
granula frangentes. Perithecia sicca ovoidea vel obpyriformia, 200-340 urn lata, 230-420 urn alta,
pallide fusca,
ubi
humida ovoidea,
ad
380 um lata, 480 um alta, laevia. Involucrellum nullum.
Excipulum pallidissimum, paries 30-80 um
latus;
stratum extimum versus apicem 10-23 um latum,
cellulae isodiametricae. Paraphyses nullae. Periphyses ramosae,
c.
20-50 um longae,
1-5-2-5
um latae. Hymenium
1+
rubescens. Asci subcylindrici, octospori,
I — ,
fissitunicati,
apices incrassati. Sporae fusiformi-ellipsoideae, 3—5-septatae, hyalinae, parietibus tenuibus,
(13-)16-21 x (4-)5-6 um. Thallus K
-,
PD
-,
C
-,
KC
-,
I
-.
Typus: Cambria, [V.C.46,] Cardiganshire: prope
Aberystwyth:
2-5
km
ad septentrio-orientem
a
Comins
Coch;
Pwll
Crwn,
52°25'N,
4° 1 'W
(22/622834),
alt.
20
m, ad corticem mortuum
Ulmiglabri
in
silva humida,
15
September
1988,/!.
Orange 7314
(NMW-holotypus;
BM,
UPS-isotypi).
(Figs
1-3)
Thallus epiphloeodal, pale green, filamentous, densely branched,
the
branches more
or less
prostrate or
more
frequently ascending
(Fig.
2E),
forming
•Department of Botany, National Museum of Wales, Cardiff CF1 3NP, UK.
0024-2829/89/030229 + 08 $03.00/0
© 1989
The British Lichen Society
230THE LICHENOLOGISTVol. 21
FIG.
1.
Macentina stigonemoides
(holotype). A, Vertical section (slightly oblique) of peritheciura
( x
320);
B, detail of excipulum at base of perithecium
(
x
910);
C, detail of excipulum near apex of
perithecium
(
x
910);
D, thallus branches
(
x
450);
E, apex of thallus branch
(
x 3120).
1989Macentina stigonemoides-Orange 231
FIG.
2.
Macentina stigonemoides (Orange
7302). A, Fragment of branch (left) associated with
soredia-like
granules;
B,
soredia-like
granules,
with short branch (upper
right);
C &
D,
soredia-like
granules (all x
1300);
E, habit, with three perithecia (arrowed) ( x 40).
232THE LICHENOLOGIST
B
Vol. 21
FIG.
3. Macentina
stigonemoides
(holotype). A, Mature (left) and immature (right) asci; B,
ascospores.
Scales
=
10
um.
a turf 50-400(-600) um high, branches cylindrical, 12-25 um wide when
young, later up to 25-35 um wide, actively growing branches tapered to apex
(Fig. ID
&
E). Branches pseudoparenchymatous, cortical layer one cell thick;
cortical cells colourless, isodiametric and
4—7
um wide in surface view, usually
bearing one or more papillae 10—11 um wide and
0-7-1-3
um high (measured
on SEM photographs). Branches often breaking into soredia-like granules
(Fig. 2A-D) forming paler green areas on the thallus; rarely thallus almost
completely granular. Soredia-like granules more or less isodiametric or
somewhat irregular in shape, 14-40 x 14-35 um; surface cells bulging, fre-
quently prominent and globose and then 3-5-7 um wide and frequently with
one or more papillae.
Photobiont
green, cells isodiametric to broadly oblong,
4-5-9 x 4-5-7 um. Apex of branch with
a
single algal
cell;
this apical cell divides
transversely, forming a single row of cells one to several cells long; these cells
undergo a series of vertical and (usually later) also transverse divisions. The
method of division results in a tiered arrangement of cells within the branch.
New branches arising laterally, at first more or less perpendicular to the parent
branch, when a superficial cell of one of the tiers of algae begins to act as an
apical cell.
Conidiomata
not seen.
Ascomata
perithecioid, superficial on the surface of the bark, surrounded
to a
variable extent by the thallus branches; when dry pale brown, ovoid, or some-
what narrowed towards the apex and then obpyriform, 200-340 um wide and
1989 Macentina
stigonemoides-Orange
233
230-420 um high; when wet, up to 380 um wide and 480 um high; surface matt
when dry, more or less smooth, naked; ostiole inconspicuous or visible as a
brownish spot,
c.
20-30 urn wide. Involucrellum absent. Excipulum pale in
section, 30-80 um thick at sides and base, of two to three distinct layers (Fig. IB
& C). Outer layer 10-23 um thick near apex of perithecium, becoming thinner
and less distinct below; cells isodiametric to oblong, 4-8 x 3-6 urn, walls up
to
c.
0-5 um thick. Median layer colourless, cells tangentially compressed,
5-12 x 2-4-5 urn, walls thickened, (0-5-)l-2(-2-5) um thick. Inner layer
indistinct, apparently similar to median layer but cells narrower and thin-
walled. Paraphyses absent. Periphyses
c.
20-50 um long,
1-5-2-5
um wide.
Centrum I + red (Lugol's Iodine), I + blue after pretreatment with 10% KOH.
Asci
8-spored,
subcylindrical with rounded apex,
c.
80-90 um long, 9-12 um
wide,
I
—,
fissitunicate, wall thickened towards apex (Fig. 3A); ocular chamber
present, at first continuous with rest of epiplast, later apparently isolated (prob-
ably joined to epiplast by a narrow canal); endotunica appearing two-layered
at apex.
Ascospores
irregularly biseriate in the ascus, colourless, fusiform-
ellipsoid, widest above the middle, thin-walled, smooth, not halonate, straight
or rarely slightly curved, 3-5-septate, slightly constricted at septa, (13-)
16-21 x (4-)5-6 urn,
3-4(-5)
times as long as wide, cells containing numerous
oil-droplets when fresh (Fig. 3B).
Chemistry: thallus K
—,
PD
—,
C
—,
KC
—,
I
—;
no lichen products detected
by TLC.
Habitat
and
distribution:
Most frequent on water-retentive bark of relatively
high pH, sometimes overgrowing bryophytes. Principally on Sambucus nigra,
but also recorded on Acer
pseudoplatanus,
Quercus
sp., Salixfragilis, S. alba,
and Ulmus glabra. The species often occurs in bark fissures, though not
necessarily sheltered from rain. Most records in Wales are from relatively
sheltered and humid, and often shaded localities, including deciduous wood-
land, conifer plantations and sheltered field margins, but the species has also
been found in more exposed situations, such as in hedges and in a suburban
park.
Macentina stigonemoides mainly occurs in species-poor or bryophyte-
dominated communities. Associated lichens are few: Anisomeridium
nyssaegenum
is frequent; Candelariella reflexa, Lecanora sambuci, Lepraria
lobificans,
Leptogium
lichenoides,
Micarea prasina, Normandina pulchella and
Physcia aipolia
have been recorded rarely. Macentina
stigonemoides
frequently
occurs almost without associated species, except sometimes Trentepohlia and
other free-living algae. Associated bryophytes recorded are Brachythecium
rutabulum, B. velutinum, Bryum flaccidum, Cololejeunea minutissima,
Cryphaea
heteromalla,
Eurhynchium
praelongum,
Frullania dilatata, Hypnum
mammillatum, Metzgeria fruticulosa, M. furcata, Neckera complanata, N.
pumila, Orthotrichum diaphanum, O. pulchellum, Pylaisia polyantha, Radula
complanata, Rhynchostegium confertum, Zygodon baumgartneri, Z. conoideus,
and Z.
viridissimus.
The examination of herbarium specimens of lichens (mainly Anisomeridium
nyssaegenum)
and bryophytes known to favour
Sambucus as a
phorophyte, led to
the discovery of additional records. The species
is
now known to be widespread
234 THE LICHENOLOGIST Vol.21
in Great Britain and Ireland, and is known from vice-counties 2, 3, 5-7, 9,10,
12,13,26,27,35,36,41^6,50,52,60,65,68,73,87,88,100,103,106,
H9,
and
H28.
Fertile specimens have been seen from Wales, Perthshire, West Sussex
and Sligo. The species is frequently found in a sterile state. Its wide distri-
bution in Britain and Ireland suggests that it could be found in adjacent parts of
Europe.
Notes: In the field the thallus of M.
stigonemoides
is easily overlooked as an
alga or as moss protonemata. Granular forms may resemble other sterile
lichens; under the microscope the granules of M.
stigonemoides
are distinguish-
able by the prominent papillose globose cells on the surface of many of the
granules. Short lengths of filamentous branch often occur amongst the
granules. Very small quantities of the species growing intermixed with moss
protonemata or algal growths may be scarcely detectable in the field.
The combination of fissitunicate asci, absence of paraphyses, presence of
periphyses, and 1+ red hymenial gel, place M.
stigonemoides
in the
Verrucariaceae. The lack of dark pigment in the perithecial wall, and the corti-
colous habit (both unusual features in the Verrucariaceae), suggest that the
species might best be placed in the genus
Macentina.
The species of
Thelidium
differ in the presence of dark pigment in the perithecial wall, and in the
saxicolous or terricolous habit. Macentina
stigonemoides
resembles
Agonimia
tristicula
and A.
octospora
in the more or less superficial perithecia that lack an
involucrellum, and in the presence of papillae on the cortical
cells
of the thallus.
In other respects however, M.
stigonemoides
does not appear to be closely
related to
Agonimia.
The outer parts of the perithecial wall in
Agonimia
are
formed of isodiametric to rhomboidal thin-walled cells which are darkly pig-
mented at the surface of
the
perithecium and become gradually paler towards
the centrum. The sides and apex of the centrum are lined by a layer of in-
wardly directed periphysis-like
hyphae,
and the asci arise from
a
restricted area
at the base of the centrum (Coppins & James 1978, and pers. obs.). In M.
stigonemoides
the outer parts of
the
perithecial wall comprise two layers differ-
ing both in cell shape and cell-wall thickness, and the periphyses are restricted
to the upper part of
the
centrum; asci arise from both the sides and base of the
centrum.
Asci within the Verrucariaceae vary in shape, number of spores, presence
or absence of an ocular chamber, and presence or absence of apical struc-
tures staining in Congo Red. The subcylindrical shape of the ascus in M.
stigonemoides is
unusual for the Verrucariaceae, though elongate asci also occur
in
Catapyrenium.
The ascus wall of M.
stigonemoides
does not stain with Congo
Red in any part. In microscopical mounts (at least of fresh material), the
fissitunicate nature of the ascus is readily seen in prematurely dehiscing,
immature
asci,
where the endotunica is extruded from the ruptured apex of the
ectotunica. In normally dehisced asci no extruded endotunica has been seen;
apparently the endotunica of mature asci is delicate and rapidly dissolves after
dehiscence. An extruded endotunica is visible in dehisced asci in many other
species of Verrucariaceae, including
Verrucaria aquatilis
(Eriksson 1981), V.
hydrela, Thelidium microcarpum, T. minutulum, Polyblastia allobata and
Agonimia tristicula
(pers. obs.).
1989 Macentina
stigonemoides-Orange
235
The thallus
of M.
stigonemoides
appears
to be
unique
in the
Verrucariaceae
for
its
filamentous habit.
The
soredia-like granules occur frequently,
in
both
sterile and fertile specimens. In many cases they occur
as
small areas on
a
turf of
branched filaments, and are clearly derived from such filaments.
It
seems likely
that
in
this case
the
granules
are
derived
by
disarticulation
of
the filaments,
partly by means of the inflation of the cells which appear prominent and swollen
on
the
surface
of
the granules; such cells occasionally become free
in
micro-
scopic preparations
of
the granules. Small sterile specimens
of
the species may
consist almost entirely of granules, and
in
this case the granules are not derived
from well-formed filaments.
The four species
of
Macentina (including
M.
stigonemoides) share
the
following features: absence
of
an involucrellum, lack
of
dark pigments
in the
perithecium,
8-spored
asci, transversely-septate colourless spores which
are
relatively slender
(at
least three times
as
long
as
wide),
and a
non-saxicolous,
non-terricolous habit. Papillae occur
on the
cortical cells
of M.
stigonemoides
and
M.
hepaticola; they have been detected recently
on the
thallus
of M.
abscondita
(B.
J.
Coppins, pers. comm.).
Key to the species of Macentina
1 Thallus filamentous, often disintegrating into soredia-like granules, corti-
cal cells with papillae; perithecia 200-380 urn wide; spores 3-5-septate
M. stigonemoides
Thallus crustose, thin; perithecia less than 160 urn wide
2
2(1) Perithecia 100-160 um wide,
in
upper part with
a
ring-shaped collar
of
thick-walled hyphae; perithecial wall 2-layered,
the
outer layer
com-
posed
of
rounded cells; spores 3(-4)-septate, (16-)18-24(-26)
x4-
5
um;
thalline hyphae with conical to warty outgrowths. On epiphyllous
hepatics
in
Zaire, known from two collections
....
M. hepaticola
Perithecia without
a
collar or other
outgrowths;
perithecial wall uniform
3
3(2) Perithecia 80-120 um wide; spores (l-)3-septate, 12-20
x
3-5-4-5
um.
On
Sambucus
and Juniperus in the British Isles
M. abscondita
Perithecia 100-150 um wide; spores 3-septate, 16-23
x
3-5-4 um.
On
leaves
of
an
unidentified tree, Guinea
M. perminuta
Selected
additional
fertile specimens
examined:
V.C.13,
West
Sussex:
West Harting Down,
41/71,
on
Sambucus
nigra,
13 March 1977,
E. C.
Wallace
(NMW,
sub Zygodon
baumgartneri).
V.C.3S,
Monmouthshire: Tintern, Blackcliff Wood, 31/531987, on
Sambucus nigra
in woodland,
31
March
1986,
A.
Orange
3613 (NMW,
sub
Anisomeridium
juistense),
V.C.44, Carmarthenshire: Llandeilo,
Dinefwr Estate,
22/622221,
on
Sambucus nigra
at
woodland margin,
18
October 1988,
A.
Orange
7384 (NMW). V.C.46, Cardiganshire; Llangwyryfon, Cwm Wyre, 22/591707, on
Sambucus nigra
in woodland, 20 August 1988,
A.
Orange
7302 (NMW);—same locality
and
date as type,
on
dead
decorticate trunk
of
Sambucus nigra
by
shaded stream
in
woodland,
A.
Orange
7318
(NMW).
V.C.87, West
Perthshire:
near Gartmore, Fir
Hill,
26/5396,
on
Sambucus
nigra,
17
March
1961,
A.
C.
Crundwell
(BBSUK,
sub Zygodon
conoideus).
V.C.H28, Sligo: near Ballymote, Temple House,
13/61.18,
on
Sambucus
nigra,
4
September
1987,
A.
Orange
6362 (NMW).
I would like to thank
Dr
B.
J.
Coppins
for
examining
a
specimen, and
for
his helpful comments.
REFERENCES
Coppins,
B.
J.
&
James,
P.
W.
(1978)
New
or
interesting British lichens
II.
Lichenologist
10:
179-207.
236 THELICHENOLOGIST Vol.21
Coppins,
B.
J.
&
Vezda,
A.
(1977)
Macentina,
a
lichen
genus new to
Europe.
Lichenologist
9:47-49.
Dobbeler,
P.
&
Vezda,
A.
(1982)
Macentina
hepaticola,
eine
neueflechte
aus
Zaire.
Mitteilungen aus
der Botanischen Staatssammlung, Miinchen 18: 1—8.
Eriksson, O. (1981) The families of bitunicate
ascomycetes.
Opera botanica
60:
1-220.
McCarthy,
P.
M.
&
Vezda,
A.
(1985) Macentina
aurantiaca,
a new
lichen from the Burren, Western
Ireland.
Lichenologist
17:
289-291.
Orange, A. (1989) The identity of
Macentina aurantiaca
McCarthy & Vezda.
Lichenologist
21:
In press.
Vezda, A. (1973) Foliicole flechten aus der Republik Guinea (W. Afrika). I.
Casopis Slezskeho
musea
v
Opave,
ser. A,
22:
67-90.
Accepted for publication 22 February 1989
Note added in
proof.
Macentina
stigonemoides
has recently been collected from central and
northern France: Correze,
12
km south-east of Treignac, by junction of D16 and D177 roads,
45°28'N, 1°55'E, on
Sambucus nigra
at edge of woodland by road, 19 May 1989, A.
Orange
7689
(NMW); Orne,
8
km south-east of Pont
d'Ouilly,
Gorges de St Aubert, near
D21
road bridge over
Orne, 48°49'N, 0°20'W, on
Sambucus nigra
in woodland, 22 May
1989,
A.
Orange
7692 (NMW).
Both collections are sterile.
