SYSTEMATIC
I. CLASSIFICATION
A. WORK OF SUCCESSIVE SYSTEMATISTS
Since the time when lichens were first recognized as a separate class—as
members of the genus Lichen by Tournefort[1016] or as “Musco-fungi” by
Morison[1017],—many schemes of classification have been outlined, and
the history of the science of lichenology, as we have seen, is a record
of attempts to understand their puzzling structure, and to express that
understanding by relating them to each other and to allied classes of
plants. The great diversity of opinion in regard to their affinities is
directly due to their composite nature.
_a._ DILLENIUS AND LINNAEUS. The first systematists were chiefly
impressed by their likeness to mosses, hepatics or algae. Dillenius[1018]
in the _Historia Muscorum_ grouped them under the moss genera:—IV.
_Usnea_, V. _Coralloides_ and VI. _Lichenoides_. Linnaeus[1019]
classified them among algae under the general name _Lichen_, dividing
them into eight orders based on thalline characters in all but one
instance, the second order being distinguished from the first by bearing
scutellae. The British botanists of the latter part of the eighteenth
century—Hudson, Lightfoot and others—were content to follow Linnaeus and
in general adopted his arrangement.
_b._ ACHARIUS. Early in the nineteenth century Acharius, the Swedish
Lichenologist, worked a revolution in the classification of lichens.
He gave first place to the form of the thallus, but he also noted the
fundamental differences in fruit-formation: his new system appeared in
the _Methodus Lichenum_[1020] with an introduction explaining the terms
he had introduced, many of them in use to this day.
Diagnoses of twenty-three genera are given with their included
species. The work was further extended and emended in _Lichenographia
Universalis_[1021] and in the _Synopsis Lichenum_[1022]. In his final
arrangement the family “Lichenes” is divided into four classes, three of
which are characterized solely by apothecial characters; the fourth class
has no apothecia. They are as follows:
Class I. Idiothalami with three orders, Homogenei, Heterogenei
and Hyperogenei: the apothecia differ in texture and colouration
from the thallus: _Lecidea_, _Opegrapha_, _Gyrophora_, etc.
Class II. Coenothalami, with three orders, Phymaloidei, Discoidei
and Cephaloidei. The apothecia are partly formed from the
thallus: _Lecanora_, _Parmelia_, etc. The Pyrenolichens are also
included by him in this class, because “the thallus surrounds and
is concrete with the partly or wholly immersed apothecia.”
Class III. Homothalami with two orders, Scutellati and Peltati.
The apothecia are formed from the cortical and medullary tissue
of the thallus: _Ramalina_, _Usnea_, _Collema_, etc.
Class IV. Athalami, with but one sterile genus, _Lepraria_.
The orders are thus based on the form of the fruit; the genera in the
_Synopsis_ number 41. Large genera such as _Lecanora_ with 132 species
are divided into sections, many of which have in turn been established as
genera, by S. F. Gray in 1821, and later by other systematists.
The _Synopsis_ was the text-book adopted by succeeding botanists for some
40 years with slight alterations in the arrangement of classes, genera,
etc.
Wallroth[1023] and Meyer[1024] followed with their studies on the lichen
thallus, and Wallroth’s division into “Homoiomerous” and “Heteromerous”
was accepted as a useful guide in the maze of forms, representing as it
did a great natural distinction.
_c._ SCHAERER. This valiant lichenologist worked continuously during
the first half of the nineteenth century, but with very partial use of
the microscope. His last publication in 1850, an _Enumeration of Swiss
Lichens_, was the final declaration of the older school that relied on
field characters. His classification is as follows:
Class I. Lichenes Discoidei, with ten orders from Usneacei to
Graphidei; fruits open.
Class II. Lichenes Capitati, with three orders: Calicioidei,
Sphaerophorei and Cladoniacei; fruits stalked.
Class III. Lichenes Verrucarioidei, with three orders:
Verrucarii, Pertusarii and Endocarpei: fruits closed.
An “Appendix” contains descriptions of Crustacei and Fruticulosi, all
sterile forms, except _Coniocarpon_ and _Arthonia_, which seem out of
place, and finally a “Corollarium” of gelatinous lichens all classified
under one genus _Collema_.
_d._ MASSALONGO AND KOERBER. As a result of their microscopic studies,
these two workers proposed many changes based on fruit and spore
characters, and Koerber in the _Systema Lichenum Germaniae_ (1855)
gave expression to these views in his classification. He also made use
of Wallroth’s distinctions of “homoiomerous” and “heteromerous,” thus
dividing lichens at the outset into those mostly with blue-green and
those with bright-green gonidia.
The following is the main outline of Koerber’s classification:
Series I. Lichenes Heteromerici.
Order I. Lich. Thamnoblasti (fruticose).
Order II. Lich. Phylloblasti (foliose).
Order III. Lich. Kryoblasti (crustaceous).
Series II. Lichenes Homoeomerici.
Order IV. Lich. Gelatinosi.
Order V. Lich. Byssacei.
With the exception of Order V all are subdivided into two sections,
“gymnocarpi” with open fruits and “angiocarpi” with closed fruits, a
distinction that had long been recognized both in lichens and in fungi.
_e._ NYLANDER. The above writers had been concerned with the
interrelationships of lichens; Nylander, who was now coming forward
as a lichenologist of note, gave a new turn to the study by dwelling
on their relation to other classes of plants. Without for a moment
conceding that they were either algal or fungal, he yet insisted on
their remarkable affinity to algae on the one hand, and to fungi on the
other, and he sought to make evident this double connection by his very
ingenious scheme of classification[1025]. He began with what we may call
“algal lichens,” those associated with blue-green gonidia in the family
“Collemacei”; he continued the series to the most highly evolved foliose
forms and then wound up with those that are most akin to fungi, that
is, those with least apparent thalline formation—according to him—the
“Pyrenocarpei.”
In his scheme, which is the one followed by Leighton and Crombie, the
“family” represents the highest division; series, tribe, genus and
species come next in order. We have thus:
Fam. I. Collemacei.
Fam. II. Myriangiacei (now reckoned among fungi).
Fam. III. Lichenacei.
This last family, which includes the great bulk of lichens, is divided
into the following series: I. Epiconiodei; II. Cladoniodei; III.
Ramalodei; IV. Phyllodei; V. Placodei; VI. Pyrenodei. It is an ascending
series up to the Phyllodei, or foliaceous lichens, which he considers
higher in development than the fruticose or filamentous Ramalodei. The
Placodei include four tribes on a descending scale, the Lecanorei,
Lecidinei, Xylographidei and Graphidei. The classification is almost
wholly based on thalline form, except for the Pyrenodei in which are
represented genera with closed fruits, there being one tribe only, the
Pyrenocarpei.
Nylander claims however to have had regard equally to the reproductive
system and was the first to give importance to the spermogonia. The
classification is coherent and easy to follow, though, like all
classifications based on imperfect knowledge, it is not a little
artificial; also while magnifying the significance of spermogonia and
spermatia, he overlooked the much more important characters of the
ascospores.
_f._ MÜLLER(-ARGAU). In preparing his lists of Genevan lichens (1862),
Müller realized that Nylander’s series was unnatural, and he found as he
studied more deeply that lichens must be ranged in parallel or convergent
but detached groups. He recognized three main groups:
1. Eulichens, divided into Capitularieae, Discocarpeae and
Verrucaroideae.
2. Epiconiaceae.
3. Collemaceae.
He suggested that, in relation to other plants, Eulichens approach
Pezizae, Hysteriaceae and Sphaeriaceae; Epiconiaceae have affinity
with Lycoperdaceae, while Collemaceae are allied to the algal family
Nostocaceae. These three groups of Eulichens, he held, advanced on
somewhat parallel lines, but reached a very varied development, the
Discocarpeae attaining the highest stage of thalline form. Müller
accepted as characters of generic importance the form and structure
of the fruiting body, the presence or absence of paraphyses, and the
septation, colour, etc. of the spores.
A few years later (1867) the composite nature of the lichen thallus was
announced by Schwendener, and, after some time, was acknowledged by most
botanists to be in accordance with the facts of nature. Any system of
classification, therefore, that claims to be a natural one, must, while
following as far as possible the line of plant development, take into
account the double origin of lichens both from algae and fungi, the
essential unity and coherence of the class being however proved by the
recurring similarity between the thalline types of the different phyla.
As Müller had surmised: “they are a series of parallel detached though
convergent groups.”
_g._ REINKE. The arrangement of Ascolichens on these lines was first
seriously studied by Reinke[1026], and his conclusions, which are
embodied[1027] in the _Lichens of Schleswig-Holstein_, have been largely
accepted by succeeding workers. He recognizes three great subclasses: 1.
Coniocarpi; 2. Discocarpi; 3. Pyrenocarpi.
The Coniocarpi are a group apart, but as their fruit is at first entirely
closed—at least in some of the genera—the more natural position for them
is between Discocarpi and Pyrenocarpi. It is in the arrangement of the
Discocarpi that variation occurs. Reinke’s arrangement of orders and
families in that sub-class is as follows:
Subclass 2. Discocarpi.
Order I. _GRAMMOPHORI_: Fam. _GRAPHIDACEI_ and _XYLOGRAPHACEI_.
Order II. _LECIDEALES_: Fam. _GYALECTACEI_, _LECIDEACEI_,
_UMBILICARIACEI_ and _CLADONIACEI_.
Order III. _PARMELIALES_: Fam. _URCEOLARIACEI_, _PERTUSARIACEI_,
_PARMELIACEI_, _PHYSCIACEI_, _TELOSCHISTACEI_ and
_ACAROSPORACEI_.
Order IV. _CYANOPHILI_: Fam. _LICHINACEI_, _EPHEBACEI_,
_PANNARIACEI_, _STICTACEI_, _PELTIGERACEI_,
_COLLEMACEI_ and _OMPHALARIACEI_.
The orders represent generally the principal phyla or groups, the
families subordinate parallel phyla within the orders. The first three
orders are stages of advance as regards fruit development; the Cyanophili
are a group apart.
Wainio[1028] rendered great service to Phylogeny in his elaborate work on
Cladoniaceae, the most complicated of all the lichen phyla. He also drew
up a scheme of arrangement in his work on Brazil Lichens[1029]. There is
in it some divergence from Reinke’s arrangement, as he tends to give more
importance to the thallus than to fruit characters as a guide. He places,
for instance, Gyrophorei beside Parmelei and at a long distance from his
Lecidei. The Cyanophili group of families he has interpolated between
_Buelliae_ (Physciaceae) and _Lecideae_. Many workers approve of Wainio’s
classification but it presents some difficult problems.
_h._ ZAHLBRUCKNER. The systematist of greatest weight in recent times is
A. Zahlbruckner, who is responsible for the systematic account of lichens
in Engler and Prantl’s _Natürlichen Pflanzenfamilien_. It is difficult to
express the very great service he has rendered to Lichenology, in that
and other world-wide studies of lichens. The sketch of lichen phylogeny
as given in the present volume owes a great deal to the sound and clear
guidance of his work, though his conclusions may not always have been
accepted. The classification in the _Pflanzenfamilien_ is the one now
generally followed.
The class _Lichenes_ is divided by Zahlbruckner[1030] into two
subclasses, I. Ascolichens and II. Hymenolichens. He gives a third class,
Gasterolichens[1031], but as it was founded on error[1032], it need not
concern us here. The Ascolichens are by far the more important. These are
subdivided into:
Series 1. =PYRENOCARPEAE=, with perithecial fruits.
Series 2. =GYMNOCARPEAE=, with apothecial fruits.
These are again broken up into families, and in the arrangement and
sequence of the families Zahlbruckner indicates his view of development
and relationship. They occur in the following order:
SERIES 1. =PYRENOCARPEAE=
ALGAL CELLS PROTOCOCCACEAE OR _PALMELLA_.
I. _MORIOLACEAE._ }
}
II. _EPIGLOEACEAE._ } Thallus crustaceous, perithecia solitary.
}
III. _VERRUCARIACEAE._ }
IV. _DERMATOCARPACEAE._ Thallus squamulose or foliose.
V. _PYRENOTHAMNIACEAE._ Thallus fruticose.
ALGAL CELLS _PRASIOLA_.
VI. _MASTOIDIACEAE._
ALGAL CELLS _TRENTEPOHLIA_.
VII. _PYRENULACEAE._ }
} Thallus crustaceous, perithecia occurring
VIII. _PARATHELIACEAE._ } singly.
IX. _TRYPETHELIACEAE._ }
} Thallus crustaceous, perithecia united
X. _ASTROTHELIACEAE._ } (stromatoid).
XI. _MYCOPORACEAE._ Thallus crustaceous, perithecia in compact
groups with a common outer wall.
XII. _PHYLLOPYRENIACEAE._ Thallus minutely foliose.
ALGAL CELLS _PHYLLACTIDIUM_ OR _MYCOIDEA_.
XIII. _STRIGULACEAE._ Tropical leaf-lichens.
ALGAL CELLS _NOSTOC_ OR _SCYTONEMA_.
XIV. _PYRENIDIACEAE._ Thallus minutely squamulose or fruticose.
SERIES 2. =GYMNOCARPEAE=
Subseries 1. Coniocarpineae, with subperithecial fruits.
Subseries 2. Graphidineae, with elongate, narrow fruits.
Subseries 3. Cyclocarpineae, with round open fruits.
SUBSERIES 1. =CONIOCARPINEAE=
This is a well-defined group, peculiar in the disappearance of the asci
at an early stage so that the spores lie like a powder in the globose
partly closed fruits. Algal cells, bright-green; Protococcaceae. There
are only three families:
XV. _CALICIACEAE._ Thallus crustaceous, apothecia stalked.
XVI. _CYPHELIACEAE._ Thallus crustaceous, apothecia sessile.
XVII. _SPHAEROPHORACEAE._ Thallus foliose or fruticose, apothecia
sessile.
SUBSERIES 2. =GRAPHIDINEAE=
This subseries comes next in the form of fruit development; generally
the apothecia are elongate, with a narrow slit-like opening, so that a
transverse section shows almost a perithecial outline. Algal cells are
mostly _Trentepohlia_.
XVIII. _ARTHONIACEAE._ Thallus crustaceous, apothecia oval or linear,
flat.
XIX. _GRAPHIDACEAE._ Thallus crustaceous, apothecia linear, raised.
XX. _CHIODECTONACEAE._ Thallus crustaceous, apothecia generally
immersed in a stroma.
XXI. _DIRINACEAE._ Thallus crustaceous, corticate above, apothecia
round.
XXII. _ROCCELLACEAE._ Thallus fruticose, apothecia round or elongate.
SUBSERIES 3. =CYCLOCARPINEAE=
A large and very varied group! In most of the families the algal
cells are bright-green (Chlorophyceae), in some they are blue-green
(Cyanophyceae), these latter corresponding to Reinke’s order Cyanophili.
The apothecia, as the name implies, are round and open; the “Cyanophili”
have been placed by Zahlbruckner after those families in which the
apothecium has no thalline margin. They form a phylum distinct from those
that precede and those that follow.
The first family of the Cyclocarpineae, the Lecanactidaceae, is often
placed under Graphidineae; in any case it forms a link between the two
subseries.
1. _Lecideine group_ (apothecia without a thalline margin).
XXIII. _LECANACTIDACEAE._ Thallus crustaceous. Algal cells
_Trentepohlia._ Apothecium with
carbonaceous hypothecium or parathecium.
XXIV. _PILOCARPACEAE._ Thallus crustaceous. Algal cells
Protococcaceae. Apothecia with a dense
rather dark hypothecium.
XXV. _CHRYSOTHRICACEAE._ Thallus felted, loose in texture. Algal
cells _Palmella_, Protococcaceae or
_Trentepohlia_. Apothecia with or without
a thalline margin. The affinity of the
“Family” seems to be with Pilocarpaceae.
XXVI. _THELOTREMACEAE._ } Thallus crustaceous. Algal cells in the
XXVII. _DIPLOSCHISTACEAE._ } first _Trentepohlia_; in the second
} Protococcaceae. In both there are
} prominent double margins round the
} apothecium.
XXVIII. _ECTOLECHIACEAE._ Thallus very primitive in type. Algal cells
Protococcaceae. Apothecia with or without
a thalline margin. Nearly related to
Chrysothricaceae.
XXIX. _GYALECTACEAE._ Thallus crustaceous. Algal cells _Trentepohlia_,
_Phyllactidium_ or rarely _Scytonema_.
Apothecia biatorine, _i.e._ of soft
consistency and without gonidia.
XXX. _COENOGONIACEAE._ Thallus confusedly filamentous (byssoid).
Algal cells _Trentepohlia_ or _Cladophora_.
Apothecia biatorine.
XXXI. _LECIDEACEAE._ Thallus crustaceous or squamulose. Algal cells
Protococcaceae. Apothecia biatorine (soft), or
lecideine (carbonaceous).
XXXII. _PHYLLOPSORACEAE._ Thallus squamulose or foliose. Algal cells
Protococcaceae. Apothecia biatorine or
lecideine.
XXXIII. _CLADONIACEAE._ Thallus twofold. Algal cells Protococcaceae.
Apothecia biatorine or lecideine.
XXXIV. _GYROPHORACEAE._ Thallus foliose. Algal cells Protococcaceae.
Apothecia lecideine.
XXXV. _ACAROSPORACEAE._ Thallus primitive crustaceous, squamulose or
foliose. Algal cells Protococcaceae.
Apothecia with or without a thalline
margin; very various, but always with
many-spored asci.
2. _Cyanophili group._
In this group the classification depends almost entirely on the nature of
the algal constituents. The apothecia are in most genera provided with a
thalline margin.
_a. More or less gelatinous when moist._
XXXVI. _EPHEBACEAE._ Algal cells _Scytonema_ or _Stigonema_. Thallus
minutely fruticose or filamentous.
XXXVII. _PYRENOPSIDACEAE._ Algal cells _Gloeocapsa_ (_Gloeocapsa_,
_Xanthocapsa_ or _Chroococcus_). Thallus
crustaceous, minutely foliose or fruticose.
XXXVIII. _LICHINACEAE._ Algal cells _Rivularia_. Thallus crustaceous,
squamulose or minutely fruticose.
XXXIX. _COLLEMACEAE._ Algal cells _Nostoc_. Thallus crustaceous,
minutely fruticose, or squamulose to foliose.
XL. _HEPPIACEAE._ Algal cells _Scytonema_. Thallus generally
squamulose and formed of plectenchyma.
_b. Not gelatinous when moist._
XLI. _PANNARIACEAE._ Algal cells _Nostoc_, _Scytonema_ or rarely
bright-green, Protococcaceae. Thallus
crustaceous, squamulose or foliose.
XLII. _STICTACEAE._ Algal cells _Nostoc_ or Protococcaceae. Thallus
foliose, and very highly developed, corticate
on both surfaces.
XLIII. _PELTIGERACEAE._ Algal cells _Nostoc_ or Protococcaceae.
Thallus foliose, corticate above.
3. _Lecanorine group_ (apothecia with a thalline margin).
The remaining families have all bright-green gonidia and nearly always
apothecia with a thalline margin. The group includes several distinct
phyla:
XLIV. _PERTUSARIACEAE._ Thallus crustaceous. Apothecia, one or
several immersed in thalline tubercles;
spores mostly very large.
XLV. _LECANORACEAE._ Thallus crustaceous or squamulose. Apothecia
mostly superficial.
XLVI. _PARMELIACEAE._ Thallus foliose, rarely almost fruticose or
filamentous. Apothecia scattered over the
surface or marginal, sessile.
XLVII. _USNEACEAE._ Thallus fruticose or filamentous. Apothecia
sessile or shortly stalked.
XLVIII. _CALOPLACACEAE._ Thallus crustaceous, squamulose or minutely
fruticose. Apothecia with polarilocular
colourless spores.
XLIX. _TELOSCHISTACEAE._ Thallus foliose or fruticose. Apothecia with
polarilocular colourless spores.
L. _BUELLIACEAE._ Thallus crustaceous or squamulose. Apothecia
(lecideine or lecanorine) with two-celled,
thick-walled brown spores (polarilocular in
part).
LI. _PHYSCIACEAE._ Thallus foliose, rarely partly fruticose.
Apothecia with two-celled thick-walled brown
spores (polarilocular in part).
Subclass 2. Hymenolichens.
There are only three closely related genera of Hymenolichens, _Cora_,
_Corella_ and _Dictyonema_ with _Chroococcus_ or _Scytonema_ algae.
There is reason to dissent from the arrangement in one or two instances
which will be pointed out in the following examination of families and
genera.
B. FAMILIES AND GENERA OF ASCOLICHENS
The necessity for a well-reasoned and well-arranged system of
classification is self-evident: without a working knowledge of the plants
that are the subject of study no progress can be made. The recognition
of plants as isolated individuals is not sufficient, it must be possible
to place them in relation to others; hence the importance of a natural
system. In identifying species artificial aids, such as habitat and
substratum, are also often of great value, and a good working system
should take account of all characteristics.
Lichen development is the result of two organisms mutually affecting
each other, but as the fungus provides the reproductive system, it is
the dominant partner: the main lines of classification are necessarily
determined by fruit characters. The algae occupy a subsidiary position,
but they also are of importance in shaping the form and structure of the
thallus. The different phyla are often determined by the presence of some
particular alga; it is in the delimitation of families that the algal
influence is of most effect.
Zahlbruckner’s system gives due weight to the inheritance from both
fungus and alga with, however, the fungus as the chief factor in
development, and as his work is certain to be generally followed by
modern lichenologists, it is the one of most immediate interest. His
scheme has been accepted in the following more detailed account of
families and genera, and for the benefit of home workers those that have
not so far been recorded from the British Isles have been marked with an
asterisk.
It cannot be affirmed that nomenclature is as yet firmly established in
lichenology. Both on historical grounds and on those of convenience, the
subject is one of extreme importance, and interest in it is one of the
main avenues by which we secure continuity with the past, and by which we
are able to realize not only the difficulty, but the romance of pioneer
work. Besides, there can be no exchange of opinion between students nor
assured knowledge of plants, until the names given to them are beyond
dispute. According to the ruling of the Brussels Botanical Congress in
1910, Linnaeus’s[1033] list of lichens in the _Species Plantarum_ has
been selected as the basis of nomenclature, but since his day many new
families, genera and species have been described and often insufficiently
delimited. It is not easy to decide between priority, which appeals to
the historical sense, and recent use which is the plea of convenience.
Here also it seems there can be no rigid decision; the one aim should be
to arrive at a conclusion satisfactory to all, and accepted by all.
In the following necessarily brief account of families and genera, the
“spermogonia” or “pycnidia” have in most cases been left out of account,
as in many instances they vary within the family and occasionally even
within the genus. Their taxonomic value is not without importance,
but, in the general systematic arrangement, they are only subsidiary
characters. An account of them has already been given, and for more
detailed statements the student is referred to purely systematic works.
There are two main types of spore production in the “pycnidia” which
have been shortly described by Steiner[1034] as “exobasidial” and
“endobasidial.” In the former the sporophores are simple or branched
filaments, at the apices of which a short process grows out and buds off
a pycnidiospore; in the latter the spores are budded directly from cells
lining the walls or filling the cavity of the pycnidium. The exobasidial
type is more simply rendered in the following pages by “acrogenous,”
the endobasidial by “pleurogenous” spore production. In many cases the
“spermogonia” or “pycnidia” are still imperfectly known. In designating
the gonidial algae, the more comprehensive Protococcaceae has been
substituted for _Protococcus_, as in many cases the alga is probably not
_Protococcus_ as now understood, but some other genus of the family[1035].
SUBCLASS I. ASCOLICHENS
SERIES I. PYRENOCARPINEAE
It is on mycological grounds that Pyrenocarpineae are placed at the base
of lichen classification. There is no evidence that the series was first
in time.
I. _MORIOLACEAE_
This family was described by Norman[1036] in 1872 from specimens
collected by himself in Norway or in the Tyrol, on soil or more
frequently on trees. There seems to have been no further record, and
Zahlbruckner, while accepting the family, suggests that an examination or
revision may be necessary.
The thallus is crustaceous. The algal cells, Protococcaceae, occur either
in groups (sometimes stalked) surrounded by a plectenchymatous wall
and called by Norman “goniocysts,” or they form nests in the thallus
termed “nuclei” which are surrounded by a double wall of plectenchyma,
colourless in the interior and brown outside. Norman invented the term
“Allelositismus,” which may be rendered “mutualism,” to indicate this
peculiar form of thallus. The species of _Spheconisca_ are fairly
numerous on poplars, willows and conifers:
Algae in “goniocysts” 1. *Moriola Norm.[1037]
Algae in double-walled “nuclei” 2. *Spheconisca Norm.
II. _EPIGLOEACEAE_
The family consists of but one genus and one species, _Epigloea
bactrospora_, and, according to Zahlbruckner, further examination is
necessary to make certain as to the lichenoid nature of the plant.
Zukal[1038] found the perithecia scattered over the leaves of mosses,
and he alleges that hyphae connected with the perithecium were closely
associated with the alga, _Palmella botryoides_, and were causing it
no harm. Along with the perithecia he also found minute pycnidia. The
“thallus” is of a gelatinous nature and homoiomerous in structure;
the perithecia are soft and clear-coloured with many-spored asci and
colourless one-septate spores.
The small globose pycnidia contain simple sporophores and acrogenous
straight or slightly bent rod-like spores.
Asci many-spored; spores one-septate 1. *Epigloea Zukal.
III. _VERRUCARIACEAE_
In all the genera of this family the thallus is crustaceous, and, with
very few exceptions, the species are saxicolous or terricolous. The
thallus is variable within the crustaceous limits, and may be superficial
and very conspicuous, almost imperceptible, or wholly immersed in the
substratum. The algal cells are Protococcaceae, and in two of the genera
the green cells penetrate the hymenium and grow in rows alongside of the
asci. The perithecia are small roundish structures scattered over the
thallus, the base immersed, but the upper portion generally projecting.
An outer dark-coloured wall surrounds the whole perithecium (entire) or
only the upper exposed portion (dimidiate); it opens above by a pore or
ostiole more or less prominent.
In some of the genera the paraphyses become dissolved at an early stage,
and somewhat similar filaments near the ostiole, termed periphyses, aid
in the expulsion of the spores. The spores vary in septation, colour
and size, and these variations have served to delimit the genera which
have been formed from the original very large genus _Verrucaria_. The
ascus may be 1-, 2-, 4- or 8-spored. In only one genus is it many-spored
(_Trimmatothele_).
The genera are as follows:
Perithecia with simple ostioles.
Paraphyses disappearing early, or wanting.
Spores simple, ellipsoid 1. Verrucaria Web.
Spores simple, elongate vermiform 2. Sarcopyrenia Nyl.
Spores simple, numerous in the ascus 3. *Trimmatothele Norm.
Spores 1-3-septate 4. Thelidium Massal.
Spores muriform (with transverse and
longitudinal divisions).
Without hymenial gonidia 5. Polyblastia Massal.
With hymenial gonidia 6. Staurothele Norm.
Paraphyses present.
Spores simple.
Without hymenial gonidia 7. Thrombium Wallr.
With hymenial gonidia 8. *Thelenidia Nyl.
Spores 3-septate, broadly ellipsoid 9. *Geisleria Nitschke.
Spores acicular, many-septate 10. Gongylia Koerb.
Spores muriform 11. Microglaena Lönnr.
Perithecia with a wide ring round the ostiole.
Spores muriform; paraphyses
unbranched 12. *Aspidothelium Wain.
Spores elongate, many-septate;
paraphyses branched 13. *Aspidopyrenium Wain.
IV. _DERMATOCARPACEAE_
In this family there is a much more advanced thalline
development—generally squamulose or with some degree of foliose
structure, though in the genus _Endocarpon_, some of the species
are little more than crustaceous. The gonidia are bright-green
Protococcaceae (according to Chodat, _Coccobotrys_ in _Dermatocarpon_).
In _Endocarpon_ they appear in the hymenium.
The least developed in structure is _Normandina_: the thallus of the
single species consists of delicate shell-like squamules which are
non-corticate above and below. In the other genera there is a cortex of
plectenchyma.
The perithecia are almost wholly immersed, and open above by a straight
ostiole. The fructification of _Dacampia_ is considered by some
lichenologists to be only a parasite on the white thickish squamulose
thallus with which it is associated.
Hymenial gonidia present.
Spores muriform 1. Endocarpon Hedw.
Hymenial gonidia absent.
Thallus non-corticate 2. Normandina Wain.
Thallus corticate.
Spores simple, colourless 3. Dermatocarpon Eschw.
Spores simple, brown 4. *Anapyrenium Müll.-Arg.
Spores elongate-septate, colourless 5. *Placidiopsis Beltr.
Spores elongate-septate, brown 6. *Heterocarpon Müll.-Arg.
Spores muriform, colourless 7. *Psoroglaena Müll.-Arg.
Spores muriform, brown 8. Dacampia Massal.
V. _PYRENOTHAMNIACEAE_
Thallus more or less fruticose and corticate on both surfaces. Algal
cells Protococcaceae.
Only two genera are included in this family: _Nylanderiella_ with one
species from New Zealand, with a small laciniate thallus up to 15 mm. in
height, partly upright, partly decumbent, and attached to the substratum
by basal rhizinae; the other small genus, _Pyrenothamnia_, belongs to N.
America; the thallus has a short rounded stalk which expands above to an
irregular frond. The perithecia are immersed in the fronds.
Spores colourless, 1-septate 1. *Nylanderiella Hue[1039].
Spores brown, muriform 2. *Pyrenothamnia Tuckerm.
VI. _MASTOIDEACEAE_
A family containing one genus and one species, with a wide distribution,
having been found in Siberia, on the Antarctic continent (Graham’s Land),
as also in Tierra del Fuego, South Georgia, South Shetland Islands and
Kerguelen. The thallus is foliose, of small thin lobes, and without
rhizinae. Algal cells _Prasiola_[1040]. The perithecia are globose and
partly project from the thallus; the asci are 8-spored; the paraphyses
are mucilaginous and partly dissolving.
Spores elongate-fusiform, simple,
colourless 1. *Mastoidea Hook. and Harv.
VII. _PYRENULACEAE_
This family of crustaceous lichens differs from Verrucariaceae chiefly in
the gonidium which is a species of _Trentepohlia_. Genera and species are
largely corticolous and the thallus is inconspicuous, often developing
within the substratum. The perithecia, like those of _Verrucariae_, are
immersed or partly emergent and have an entire or dimidiate outer wall.
They are scattered over the thallus except in _Anthracothecium_ where
they are often coalescent. This genus is tropical or subtropical except
for one species which inhabits S.W. Ireland.
Paraphyses are variable, and in some species tend to disappear, but do
not dissolve in mucilage. The spores are generally colourless, only in
one monotypic genus, _Coccotrema_, are they simple. The cells into which
the spore is divided differ in form according to the genus.
Paraphyses branched and entangled or wanting.
Perithecia opening above by stellate
lobes 1. *Asteroporum Müll.-Arg.
Perithecia opening by a pore.
Spores variously septate.
Spore cells cylindrical or cuboid.
Spores colourless, elongate or
ovate 1-5-septate 2. Arthopyrenia Massal.
Spores colourless, filiform
1-multi-septate 3. Leptorhaphis Koerb.
Spores colourless, muriform 4. Polyblastropsis A. Zahlbr.
Spores brown, ovoid or elongate
2-5-septate 5. Microthelia Koerb.
Spore cells globose or lentiform,
3-multi-septate 6. *Pseudopyrenula Müll.-Arg.
Paraphyses unbranched free.
Spore cells cylindrical or cuboid.
Perithecia beset with hairs 7. *Stereochlamys Müll.-Arg.
Perithecia naked.
Asci disappearing; spores elongate
multi-septate, colourless 8. *Belonia Koerb.
Asci persistent.
Spores simple, ellipsoid,
colourless 9. *Coccotrema Müll.-Arg.
Spores elongate, 1-multi-septate,
colourless 10. Porina Müll.-Arg.
Spores elongate, 1-multi-septate,
brown 11. Blastodesmia Massal.
Spores muriform, colourless 12. *Clathroporina Müll.-Arg.
Spores elongate, 2-3-septate,
colourless 13. Thelopsis Nyl.
Spore cells globose or lentiform.
Spores elongate, 1-5-septate,
brown 14. Pyrenula Massal.
Spores muriform, brown 15. Anthracothecium Massal.
VIII. _PARATHELIACEAE_
This family is peculiar in that the perithecia open by a somewhat
elongate ostiole that slants at an oblique angle. The algal cells are
_Trentepohlia_. Genera and species are endemic in tropical or subtropical
regions of the Western hemisphere, though a species of _Pleurotrema_ has
been found in subantarctic America. They are corticolous and the thallus
is either superficial or embedded. The genera are arranged according to
spore characters:
Spores elongate, 2- or more-septate.
Spore cells cylindrical, colourless 1. *Pleurotrema Müll.-Arg.
Spore cells globose-lentiform.
Spores colourless 2. *Plagiotrema Müll.-Arg.
Spores brown 3. *Parathelium Müll.-Arg.
Spores muriform.
Spores colourless 4. *Campylothelium Müll.-Arg.
Spores brown 5. *Pleurothelium Müll.-Arg.
IX. _TRYPETHELIACEAE_
This and the following two families are distinguished by the pseudostroma
or compound fruit, a character rare among lichens, though the true stroma
is frequent in Pyrenomycetes in such genera as _Dothidea_, _Valsa_, etc.
The genera are crustaceous and corticolous and occur with few exceptions
in tropical or subtropical regions, mostly in the Western Hemisphere.
Several grow on officinal bark (_Cinchona_, etc.). Algal cells are
_Trentepohlia_. As in many tropical lichens, the spores are large. The
genera are based chiefly on spore characters, on septation, and on the
form of the spore cells:
Spore cells cylindrical or cuboid.
Spores colourless, elongate,
multi-septate 1. *Tomasiella Müll.-Arg.
Spores colourless, muriform 2. *Laurera Rehb.
Spores brown, muriform 3. *Bottaria Massal.
Spore cells globose-lentiform.
Spores colourless, elongate,
multi-septate 4. *Trypethelium Spreng.
Spores brown, elongate, multi-septate 5. Melanotheca Müll.-Arg.
X. _ASTROTHELIACEAE_
The perithecia are either upright or inclined, and occur usually in
radiate groups. They are free or united in a stroma, and the elongate
ostioles open separately or coalesce in a common canal. The genera
are all crustaceous, with _Trentepohlia_ gonidia. They are tropical
or subtropical, mostly in the Western Hemisphere; but species of
_Parmentaria_ and _Astrothelium_ have been recorded also from Australia.
The spores are all many-celled and the form of their cells is a generic
character:
Spores elongate, multi-septate.
Spore cells cylindrical 1. *Lithothelium Müll.-Arg.
Spore cells globose-lentiform.
Spores colourless 2. *Astrothelium Trev.
Spores brown 3. *Pyrenastrum Eschw.
Spores muriform.
Spores colourless 4. *Heufleria Trev.
Spores brown 5. *Parmentaria Fée.
XI. _MYCOPORACEAE_
A small family with only two genera which are found in both Hemispheres;
species of both occur in Great Britain. They are all corticolous. The
perithecia are united into a partially chambered fruiting body surrounded
by a common wall, but opening by separate ostioles. The thallus is thinly
crustaceous, with _Palmella_ gonidia in _Mycoporum_, and _Trentepohlia_
in _Mycoporellum_. The spores are colourless or brown in both genera:
Spores muriform 1. Mycoporum Flot.
Spores elongate, multi-septate 2. Mycoporellum A. Zahlbr.
XII. _PHYLLOPYRENIACEAE_
Thallus foliose with both surfaces corticate and attached by rhizinae.
Algal cells _Trentepohlia_. There is but one genus, _Lepolichen_, which
has a laciniate somewhat upward growing thallus. Two species, both from
South America, have been described, _L. granulatus_ Müll.-Arg. and _L.
coccophora_ Hue. The latter has been recently examined by Hue[1041]
who finds, on the thalli, cephalodia which are peculiar in containing
bright-green gelatinous algae either _Urococcus_ or _Gloeocystis_, one
of the few instances known of chlorophyllaceous algae forming part
of a cephalodium. _Gloeocystis_ may be the only alga present in the
cephalodium; _Urococcus_ is always accompanied by _Scytonema_.
The perithecia are immersed in thalline tubercles:
Spores colourless, simple, ovoid or
ovoid-elongate 1. *Lepolichen Trevis.
XIII. _STRIGULACEAE_
A family of epiphyllous lichens inhabiting and disfiguring coriaceous
evergreen leaves, or occasionally fern leaves in tropical or subtropical
regions. The algae associated are _Mycoidea_ and _Phycopeltis_
(_Phyllactidium_). The only truly parasitic lichen, _Strigula_, belongs
to this family: the alga precedes the lichen on the leaves and is
gradually invaded by the hyphae of the lichen and altered in character.
The small black perithecia are scattered over the surface. In _Strigula_
the lichen retains the spreading rounded form of the alga. The other
genera are more irregular.
Thallus orbicular in outline 1. *Strigula Fries.
Thallus irregular.
Perithecia without hairs.
Spores colourless.
Spores elongate, multi-septate 2. *Phylloporina Müll.-Arg.
Spores muriform 3. *Phyllobathelium Müll.-Arg.
Spores brown.
Spores simple 4. *Haplopyrenula Müll.-Arg.
Spores elongate, 1-3-septate 5. *Microtheliopsis Müll.-Arg.
Perithecia beset with stiff hairs 6. *Trichothelium Müll.-Arg.
XIV. _PYRENIDIACEAE_
The only family of Pyrenocarpineae associated with blue-green algae. The
genera of Pyrenidiaceae are all monotypic, only one is common and of wide
distribution, _Coriscium_ (_Normandina_ Nyl.). _Pyrenidium_ is the only
member that has a fruticose thallus, and that is of minute dimensions.
_Eolichen Heppii_, found and described by Zukal, is a doubtful
lichen. “_Lophothelium_” Stirton is a case of parasitism of a fungus,
_Ticothecium_, on the squamules of _Stereocaulon condensatum_.
Algal cells _Scytonema_ or _Stigonema_.
Thallus crustaceous[1042]; spores simple,
colourless 1. *Rhabdopsora Müll.-Arg.
Thallus crustaceous; spores 1-septate,
colourless 2. *Eolichen Zuk.
Thallus crustaceous; spores muriform,
brown 3. *Pyrenothrix Riddle[1043].
Thallus squamulose; spores numerous,
simple 4. *Placothelium Müll.-Arg.
Algal cells _Nostoc_.
Thallus crustaceous; spores filiform,
simple, colourless 5. *Hassea A. Zahlbr.
Thallus fruticose; spores elongate,
3-septate, brown 6. Pyrenidium Nyl.
Algal cells _Microcystis_ (_Polycoccus_).
Thallus squamulose; fructification
unknown 7. Coriscium Wainio.
SERIES II. =GYMNOCARPEAE=
SUBSERIES 1. =Coniocarpineae=
This small subseries is marked by the peculiar “mazaedium” type of
fruit with its disappearing asci. It forms a connecting link between
the families with perithecia and those with apothecia. The thallus is
crustaceous or fruticose, often poorly developed and sometimes absent.
The algal cells are Protococcaceae or rarely _Trentepohlia_.
XV. _CALICEACEAE_
The thallus is thinly crustaceous, sometimes brightly coloured, sometimes
absent, taking no part in the formation of the fruits; these have upright
stalks with a small capitulum, and often look like minute nails. One
genus, _Sphinctrina_, is parasitic on the thallus of other lichens,
mostly _Pertusariae_.
Fruits with slender stalks.
Spores simple.
Spores colourless 1. Coniocybe Ach.
Spores brown 2. Chaenotheca Th. Fr.
Spores septate, brown.
Spores 1-septate 3. Calicium De Not.
Spores 3-7-septate 4. Stenocybe Nyl.
Fruits with short thick stalks.
Spores globose, brown (parasitic) 5. Sphinctrina Fries.
Spores 1-septate, brown 6. *Pyrgidium Nyl.
XVI. _CYPHELIACEAE_
Thallus crustaceous. Algal cells Protococcaceae or _Trentepohlia_.
Apothecia sessile, more widely open than in the previous family; in
some genera the thallus forms an outer apothecial margin. The genera
_Farriola_ from Norway and _Tylophorella_ from New Granada are monotypic.
The British genus _Cyphelium_ has been known as _Trachylia_.
Thallus with Protococcaceae.
Spores colourless, simple 1. *Farriola Norm.
Spores brown, 1-3-septate (rarely simple
or muriform) 2. Cyphelium Th. Fr.
Thallus with _Trentepohlia_.
Spores simple, many in the ascus 3. *Tylophorella Wainio.
Spores 8 in the ascus.
Apothecia with a thalline margin 4. *Tylophoron Nyl.
Apothecia without a thalline margin 5. *Pyrgillus Nyl.
XVII. _SPHAEROPHORACEAE_
The most highly evolved family of the subseries, as regards the thallus.
Algal cells Protococcaceae. In _Tholurna_, a small lichen endemic in
Scandinavia, there is a double thallus: one of horizontal much-divided
squamules, the other swollen, upright, terminating in the capitulum. The
fruit is lateral in _Calycidium_, a squamulose form from New Zealand, and
in _Pleurocybe_ from Madagascar, with stiff strap-shaped fronds. All the
genera are monotypic except _Sphaerophorus_, of which genus ten species
are recorded, some of them with a world-wide distribution. The spores are
brown and simple or 1-septate.
Thallus squamulose and upright 1. *Tholurna Norm.
Thallus wholly squamulose 2. *Calycidium Stirton.
Thallus fruticose.
Fronds hollow in the centre 3. *Pleurocybe Müll.-Arg.
Fronds not hollow.
Fruit without a thalline margin 4. *Acroscyphus Lév.
Fruit inclosed in the tip of the
fronds 5. Sphaerophorus Pers.
SUBSERIES 2. =Graphidineae=
In this subseries are included five families that differ rather widely
from each other both in thallus and apothecia; the latter are more or
less carbonaceous and mostly with a proper margin only. Families and
genera are widely distributed, though most abundant in warm regions.
Algal cells mostly _Trentepohlia_.
A comprehensive study of the apothecia of this series by Bioret[1044]
gives some interesting results in regard to the paraphyses: in _Arthonia_
they are irregular in direction and much-branched; in _Opegrapha_,
the paraphyses are vertical and parallel with more regular branching;
_Stigmatidium_ (_Enterographa_) resembles _Opegrapha_ in this respect as
does also _Platygrapha_, a genus of Lecanactidaceae, while in _Graphis_
the paraphyses are vertical, unbranched and free; _Melaspilea_ paraphyses
are somewhat similar to those of _Graphis_.
XVIII. _ARTHONIACEAE_
The thallus of Arthoniaceae is corticolous with few exceptions and
is very inconspicuous, being largely embedded in the substratum. The
apothecia (ardellae) are round, irregular or stellate, without any
margin, the hymenium being protected by the dense branching of the
paraphyses at the tips.
_Arthonia_ is abundant everywhere. The species of the other genera
belong mostly to tropical or subtropical countries. _Arthoniopsis_ is
similar to _Arthonia_ in the character of the fruits, but the gonidium
is a _Phycopeltis_, and it is only found on leaves. _Synarthonia_ with
peculiar stromatoid fructification is monotypic; it occurs in Costa Rica.
Thallus with _Trentepohlia_ gonidia.
Apothecia scattered.
Spores elongate 1- or pluri-septate 1. Arthonia Ach.
Spores muriform 2. Arthothelium Massal.
Apothecia stromatoid.
Spores elongate, multi-septate 3. *Synarthonia Müll.-Arg.
Thallus with _Palmella_ gonidia.
Spores 1- or more-septate 4. Allarthonia Nyl.
Spores muriform 5. *Allarthothelium Wain.
Thallus with _Phycopeltis_ gonidia.
Spores elongate 1- or more-septate 6. *Arthoniopsis Müll.-Arg.
XIX. _GRAPHIDACEAE_
Thallus crustaceous, inconspicuous, partly immersed, mainly growing
on bark but occasionally on dead wood or stone. Algal cells chiefly
_Trentepohlia_, very rarely _Palmella_ or _Phycopeltis_ (epiphyllous).
Apothecia (lirellae) carbonaceous more or less linear, opening by a
narrow slit with a well-developed proper margin except in _Gymnographa_,
a monotypic Australian genus. In two genera, the fruit is of a compound
nature, several parallel discs occurring in one lirella: these are
_Ptychographa_ (on bark in Scotland) and _Diplogramma_ (Australia), both
are monotypic. They must not be confused with _Graphis elegans_ and
allied species in which the sterile carbonaceous margin is furrowed. Two
tropical genera associated with _Phycopeltis_ are epiphyllous.
Graphidaceae are among the oldest recorded lichens, attention having been
drawn to them since early times by the resemblance of the lirellae on the
bark of trees to hieroglyphic writing.
Thallus with _Palmella_ gonidia.
Apothecia single.
Hypothecium dark-brown.
Spores simple 1. Lithographa Nyl.
Hypothecium colourless or brownish.
Spores colourless.
Spores simple 2. Xylographa Fries.
Spores elongate 3-8-septate 3. *Aulaxina Fée.
Spores brown.
Spores 1-septate 4. Encephalographa Massal.
Spores pluri-septate, then muriform 5. *Xyloschistes Wain.
Apothecia compound.
Spores simple, colourless 6. Ptychographa Nyl.
Spores pluri-septate, colourless 7. *Diplogramma Müll.-Arg.
Thallus with _Trentepohlia_ gonidia.
Spores elongate 1-multi-septate, the cells longer than wide.
Spores brown.
Spores 1-(rarely more)-septate 8. Melaspilea Nyl.
Spores 3-septate (apothecia
rudimentary) 9. *Gymnographa Müll.-Arg.
Spores colourless.
Spores acicular, coiled (many in the
ascus) 10. *Spirographa A. Zahlbr.
Spores fusiform, straight 11. Opegrapha Humb.
Spores muriform.
Spores elongate, central cells
finally muriform 12. *Dictyographa Müll.-Arg.
Spores elongate, septate, cells wider than long.
Paraphyses unbranched, filiform.
Spores multi-septate, colourless 13. Graphis Adans.
Spores multi-septate, brown 14. Phaeographis Müll.-Arg.
Spores muriform, colourless 15. Graphina Müll.-Arg.
Spores muriform, brown 16. Phaeographina Müll.-Arg.
Paraphyses clavate, warted at tips 17. *Acanthothecium Wain.
Paraphyses branched, interwoven above 18. *Helminthocarpon Fée.
Thallus with _Phycopeltis_ gonidia (epiphyllous).
Spores elongate, 3-9-septate,
colourless 19. *Opegraphella Müll.-Arg.
Spores elongate, 1-septate, brown 20. *Micrographa Müll.-Arg.
XX. _CHIODECTONACEAE_
Specially distinguished in this subseries by the grouping of the somewhat
rudimentary apothecia in pseudostromata in which they are almost wholly
immersed. In form they are roundish or linear; the spores are septate or
muriform. The thallus is thinly crustaceous and continuous: in _Glyphis_,
_Sarcographa_ and _Sarcographina_ there is an amorphous upper cortex, the
other genera are non-corticate. Algal cells are _Trentepohlia_ with the
exception of two epiphyllous genera associated with _Phycopeltis_.
Genera and species are mostly tropical. _Sclerophyton_ with five
species is represented in Europe by a single British specimen, _S.
circumscriptum_.
The form of the paraphyses is a distinguishing character of the genera.
Thallus with _Trentepohlia_ gonidia.
Paraphyses free, unbranched.
Spore cells short or almost globose.
Spores elongate, multi-septate,
colourless 1. Glyphis Fée.
Spores elongate, multi-septate, brown 2. *Sarcographa Fée.
Spores muriform, brown 3. *Sarcographina Müll.-Arg.
Spore cells longer and cuboid.
Spores muriform, colourless 4. *Enterodictyon Müll.-Arg.
Paraphyses branched, interwoven above.
Spores elongate, multi-septate,
colourless 5. Chiodecton Ach.
Spores elongate, multi-septate, brown 6. Sclerophyton Eschw.
Spores muriform, colourless 7. *Minksia Müll.-Arg.
Spores muriform, brown 8. *Enterostigma Müll.-Arg.
Thallus with _Phycopeltis_ gonidia (epiphyllous).
Paraphyses free.
Spores unequally 2-celled,
colourless 9. *Pycnographa Müll.-Arg.
Paraphyses branched, interwoven above.
Spores elongate, multi-septate,
colourless 10. *Mazosia Massal.
XXI. _DIRINACEAE_
A small family, which is associated with and often included under
Graphidaceae. The thallus is crustaceous and corticate on the upper
surface, the cortex being formed of palisade hyphae. Algal cells
_Trentepohlia_. Apothecia are rounded or with a tendency to elongation,
and, in addition to a thin proper margin, possess a stout thalline
margin; the hypothecium is thick and carbonaceous. There are two genera:
_Dirina_ with twelve species has a wide distribution; _Dirinastrum_ is
monotypic and occurs on maritime rocks in Australia. In both the spores
are elongate-septate, differing only in colour:
Spores colourless 1. Dirina Fr.
Spores brown 2. *Dirinastrum Müll.-Arg.
XXII. _ROCCELLACEAE_
The Roccellaceae differ from the preceding Dirinaceae chiefly in the
fruticose thallus which is more or less characteristic of all the genera,
though in _Roccellographa_ it expands into foliose dimensions and in
_Roccellina_ is reduced to short podetia-like processes from a crustose
base. The fronds—mostly long and strap-shaped—are protected in most of
the genera by a cortex of compact palisade hyphae; in a few the outer
hyphae are parallel with the long axis. The medulla is of parallel
hyphae, either loose or compact. The algal cells are _Trentepohlia_.
The apothecia are lateral except in _Roccellina_ where they occur at the
tips of the short upright fronds, and only in _Roccellaria_ is there
no thalline margin. They are superficial in all of the genera except
_Roccellographa_, in which they are immersed and almost closed, recalling
the perithecia-like fruits of _Chiodecton_ (sect. _Enterographa_). The
spores are elongate, narrow, pluri-septate, and colourless or brownish,
except in _Darbishirella_ in which they are ovoid, 2-septate and brown.
The affinity of Dirinaceae and Roccellaceae with Graphidaceae was first
indicated by Reinke[1045] and elaborated later by Darbishire[1046] in
his monograph of Roccellaceae. The apothecia in some species of _Dirina_
are ellipsoid rather than round; in several genera of Roccellaceae they
are distinctly lirellate, and in _Roccella_ itself some species have
ellipsoid fruits. The fruticose thallus is predominant in Roccellaceae,
but its evolution from the crustaceous type may be traced through
_Roccellina_ which is partly crustaceous and only imperfectly fruticose.
In most of the genera only one species is recorded. _Roccella_,
represented by twelve species, is well known for its dyeing properties,
and has a wide distribution. Like other Graphidineae they are mainly
plants of warm regions, many of them exclusively maritime rock-dwellers.
The following synopsis of the genera is the one given by Darbishire in
his monograph.
Cortex fastigate, of palisade hyphae.
Spores colourless.
Hypothecium black-carbonaceous.
Apothecia round.
Thallus fruticose 1. Roccella DC.
Thallus crustaceous-fruticose 2. *Roccellina Darbish.
Apothecia lirellate 3. *Reinkella Darbish.
Hypothecium colourless.
Gonidia present under the
hypothecium 4. *Pentagenella Darbish.
Gonidia absent from hypothecium 5. *Combea De Not.
Spores brown or brownish.
Medulla of parallel somewhat loose
hyphae 6. *Schizopelte Th. Fr.
Medulla solid, black 7. *Simonyella Steiner.
Cortex fibrous, of parallel hyphae.
Apothecia round.
Hypothecium black-carbonaceous.
Apothecia with thalline margin 8. *Dendrographa Darbish.
Apothecia with proper margin 9. *Roccellaria Darbish.
Hypothecium colourless 10. *Darbishirella A. Zahlbr.
Apothecia lirellate 11. *Ingaderia Darbish.
SUBSERIES 3. =Cyclocarpineae=
This last subseries includes the remaining twenty-nine families of
Ascolichens. They are very varied both in the fungal and the algal
symbionts. The fruit is more or less a discoid open apothecium. The
gonidia belong to different genera of Myxophyceae and Chlorophyceae,
but the most frequent are Protococcaceae. Families are based largely on
thalline structure.
XXIII. _LECANACTIDACEAE_
By many systematists this family is included under Graphidineae
on account of the fruit structure which in some of the forms is
carbonaceous and almost lirellate, and also because the algal symbiont is
_Trentepohlia_. The thallus is primitive, being thinly crustaceous and
non-corticate; the apothecium has a black carbonaceous hypothecium in two
of the genera, _Lecanactis_ and _Schismatomma_ (_Platygrapha_); in the
third genus, _Melampydium_, it is colourless. The latter is monotypic,
and the spores become muriform. In the other genera they are elongate and
multi-septate.
Apothecia with prominent proper margin 1. Lecanactis Eschw.
Apothecia with thin proper margin 2. *Melampydium Müll.-Arg.
Apothecia with thalline margin 3. Schismatomma Flot.
XXIV. _PILOCARPACEAE_
A small family with but one genus, _Pilocarpon_. It is distinguished
as one of the few epiphyllous genera of lichens associated with
Protococcaceous gonidia and with a distribution extending far beyond
the tropics. The best known species, _P. leucoblepharum_, encircles the
base of pine-needles with a white felted crust, or inhabits coriaceous
evergreen leaves. Another species lives on fern leaves. The fruit is
a discoid apothecium with a dark carbonaceous hypothecium and proper
margin, and with a second thalline margin. The paraphyses are branched
and interwoven above.
Spores elongate, 3-septate, colourless 1. Pilocarpon Wain.
XXV. _CHRYSOTRICHACEAE_
This family now, according to Hue[1047], includes two genera, _Crocynia_
and _Chrysothrix_. In both there is a thallus of interlaced hyphae with
Protococcaceous algae scattered through it or in groups. The structure
is thus homoiomerous, and Hue has suggested for it a new series,
“Intertextae.” The only British species, _Crocynia lanuginosa_, first
placed by Nylander[1048] in _Amphiloma_ and later transferred by him to
_Leproloma_[1049], has a soft crustaceous lobate thallus, furfuraceous on
the surface; no fructification has been found. A West Indian species, _C.
gossypina_, has discoid apothecia with a thalline margin. There is only
one species of _Chrysothrix_, _Ch. nolitangere_, which forms small clumps
or tufts on the spines of Cactus in Chili. The structure is somewhat
similar to that of _Crocynia_.
Spores colourless, simple 1. Crocynia Nyl.
Spores colourless, 2-3-septate 2. *Chrysothrix Mont.
XXVI. _THELOTREMACEAE_
A tropical or subtropical family of which the leading characteristic is
the deeply sunk disc of the apothecium: it has a proper hyphal margin,
and, round that, an overarching thalline margin. The apothecia occur
singly, or they are united in a kind of pseudostroma: in _Tremotylium_
several grow together, while in _Polystroma_ each new apothecium develops
as an outgrowth from the thalline margin of the one already formed,
so that an upright, branching succession of fruits is built up. It is
a very unusual type of lichen fructification, with one species, _P.
Ferdinandezii_, found in Spain and in Guiana.
The thallus in all the genera is crustaceous with an amorphous
(decomposed) cortex; or it is non-corticate. The algal cells are
_Trentepohlia_ except in _Phyllophthalmaria_, an epiphyllous genus
associated with the alga _Phycopeltis_. In _Polystroma_ the alga is
unknown.
Only one genus is represented in the British Isles.
Apothecia growing singly.
Thallus with _Trentepohlia_ gonidia.
Paraphyses numerous, unbranched, free.
Spores colourless.
Spores elongate, 2- or
multi-septate 1. *Ocellularia Spreng.
Spores muriform 2. Thelotrema Ach.
Spores brown.
Spores elongate, septate 3. *Phaeotrema Müll.-Arg.
Spores muriform 4. *Leptotrema Mont.
Paraphyses scanty, branched.
Spores muriform, brown 5. *Gyrostomum Fr.
Thallus with _Phycopeltis_ gonidia 6. *Phyllophthalmaria A.
Zahlbr.
Apothecia in pseudostromata.
Apothecia united in tubercles 7. *Tremotylium Nyl.
Apothecia united by the margins 8. *Polystroma Clem.
XXVII. _DIPLOSCHISTACEAE_
Scarcely differing from the preceding family except in the gonidia which
are Protococcaceous algae. The thallus is crustaceous and non-corticate.
The apothecia have a double margin but the outer thalline margin is less
overarching than in Thelotremaceae. The spores in the two genera are
somewhat peculiar: in _Conotrema_ they are exceedingly long and divided
by parallel septa into thirty to forty small cells; in _Diploschistes_
(_Urceolaria_) they are large, muriform and brown. _Conotrema_ contains
two corticolous species; _Diploschistes_ about thirty species mostly
saxicolous. Both genera are represented in the British Isles.
Spores elongate, multi-septate,
colourless 1. Conotrema Tuck.
Spores muriform, brown 2. Diploschistes Norm.
XXVIII. _ECTOLECHIACEAE_
A family of tropical epiphyllous lichens that are associated with
Protococcaceous gonidia. The thallus is primitive in character, mostly a
weft of hyphae with intermingled algal cells, described as homoiomerous.
The apothecia are without a thalline margin, and with a scarcely
developed proper margin: their affinity is with the Lecideaceae, though
in two genera, _Lecaniella_ and _Arthotheliopsis_, there are gonidia
below the hypothecium, a character of Lecanoraceae. The genera are nearly
all monotypic; in _Sporopodium_ has been included _Lecidea phyllocharis_
Wainio (Sect. _Gonothecium_), which is distinguished by hymenial gonidia.
Apothecia at first covered by a “veil.”
Spores elongate, colourless,
septate 1. *Asterothyrium Müll.-Arg.
Apothecia uncovered from the first.
Gonidia not present below the hypothecium.
Paraphyses unbranched, free.
Spores muriform 2. *Lopadiopsis Wain.
Paraphyses branched.
Spores 1-septate 3. *Actinoplaca Müll.-Arg.
Spores elongate, multi-septate 4. *Tapellaria Müll.-Arg.
Spores muriform 5. *Sporopodium Mont.
Gonidia present below the hypothecium.
Spores elongate, 2-septate 6. *Lecaniella Wain.
Spores muriform 7. *Arthotheliopsis Wain.
XXIX. _GYALECTACEAE_
The algal cells in this family are filamentous; either Myxophyceae
(_Scytonema_) or Chlorophyceae (_Trentepohlia_ or _Phyllactidium_).
The thallus is crustaceous, and in some cases homoiomerous, as in
_Petractis_, where the alga, _Scytonema_, penetrates the substratum as
deeply as the hyphae. _Monophiale_, a tropical genus, possesses two
kinds of gonidia: the species that grow on bark or mosses are associated
with _Trentepohlia_; others that have invaded the surface of leathery
evergreen leaves resemble most epiphyllous lichens in being associated
with the leaf alga _Phyllactidium_ (_Phycopeltis_). Some species of
_Trentepohlia_ exhale when moist an odour of violets. This scent is
retained in at least one genus, _Jonaspis_.
The apothecia are superficial, and are soft, waxy and bright-coloured,
with prominent margins which are however entirely hyphal: the affinity
is therefore with Lecideaceae. In one genus, _Sagiolechia_, the fruit
is carbonaceous and dark coloured. The spores of all the genera are
colourless.