Lichens form a plant group apart, as the body consists of a fungus and an alga growing together to form the lichen thallus. The exact relations between the fungus and the alga are still subjects of discussion, but the group is morphologically so distinct that it may best be treated as a separate division of the plant kingdom (LICHENES, or if you will MYCOPHYCOPHYTA!) The division is split up into subdivisions, orders, families, genera and species, the classification being based primarily on the structure of the fungal fruit, and secondarily on the nature of the alga. A few tropical genera have fungal elements belonging to the HYMENOMYCETES, but the bulk are associated with ASCOMYCETES. These ASCOLICHENES are divided into page 21 the PYRENOCARPEAE with a closed fructification (perithecium), and the (GYMNOCARPEAE) with an open fructification (apothecium).

The alga present belong either to the CHLOROPHYCEAE, “green algae”, or the MYXOPHYCEAE, “blue-green algae”. It is usually possible, simply by moistening the specimen, to decide to which group the alga of a particular lichen belongs, but in refined classifications one has to determine more closely the relationship of the lichen alga to the free-living alga.

Zahlbruckner (Pflanzenfamilien, 1926) recognised 54 families (35 in New Zealand), 375 genera (about 80 in New Zealand), and about 9700 species (over 600 in New Zealand). Very many more remain to be discovered, and probably hundreds in New Zealand.

Lichens are the most truly cosmopolitan group of plants, being absent only from areas covered by perpetual snow or water. They succumb, however, to the smoke of heavily industrialised areas. You can, if you care to risk the attention of the police, gather lichens on the walls of the Wellington Bank of New Zealand, but not on those of the London Branch. Arid deserts, humid forests, coastal spray-sprinkled rocks and ice-surrounded rocks of high mountains are all habitats yielding their species. The elegant little red thallus of Caloplaca elegans has been gathered a few feet above high-tide level on Rangitoto Island, and just below the summit of Mt. Tapuaenuku (9465 feet). The range of habitats is very great, even glass, iron, charcoal, leather, linoleum and tarred cloth are not immune. Xanthoira parietina (Fig. 38) will seize on and brighten a rock, an animal skeleton, or a tree trunk, while certain lichens are strictly confined to one particular habitat, e.g., certain species of Verrucaria do not live away from rocks periodically submerged by the tide. Limestone rocks and basaltic rocks have different assemblages of genera and species, and the ecology of lichens becomes fascinating once a reasonable knowledge of the genera and species has been gained.

The first important work on the lichens of New Zealand was that of Babington in Hooker's Flora Novae Zelandiae of 1885, based largely on collections made by Colenso and Lyall. In Hooker's “Handbook” of 1867, forty-four genera and 212 species were listed, many of which were referred to European species, but are now considered distinct. New species were described in the early volumes of the Transactions of the New Zealand Institute, especially by Knight, who built up a considerable herbarium. In 1888 Nylander published his Lichenes Novae Zelandiae, listing 371 species, 97 of which he considered to be identical with European species.

The study of our lichens then languished; meanwhile much critical work was being done in Europe and new conceptions of generic and species limits evolved. Of recent years local botanists have shown page 22 renewed interest, and in 1941 Zahlbruckner published his monograph, Lichenes Novae Zelandiae, based on collections, largely those of the late J. S. Thomson of Dunedin. At present only a very few copies of this work are available in New Zealand. Large collections of Cladonia were sent to Sandstede, the outstanding authority on this genus. As a result local botanists can now pursue their studies with more confidence.

The best book in English for any one taking up the study of lichens is “Lichens” by the late Annie Lorraine Smith, 1921, in the “Cambridge Botanical Handbooks.” This deals with all aspects of the subject, is well illustrated, and should be in the libraries of all University Colleges. A useful short work, with good keys to the genera, is that of W. Watson, “The Classification of Lichens” which appeared in the New Phytologist, Vol. 28, 1929.

Key to The Commoner Genera of N.Z. Lichens

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Key to the Groups of Stictaceae

The two genera of this family—Sticta and Lobaria, are fairly readily grouped into sub-genera, which are now often treated as genera. There are over 50 species in New Zealand, all groups being represented

The last two may each be again divided according as the pseudocyphellae are white or yellow.

Key to the Groups of Parmelia

The genus is also represented by over 50 species in New Zealand. The different groups, some often treated as separate genera, may be keyed as follows:

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Key to the Groups of Cladonia

Cladonia (Figs. 23, 29, 31) is represented by about 40 species in New Zealand, but there is considerable difference of opinion as to species limits in the genus, and some classifications would raise the number to about 70. The groups, or sub-genera, are fairly well defined as follows:

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The student must understand that the forms of Cladonia are manifold, and no manageable key will provide for all possible combinations of characters. If desired a key to the more important species will be given later.

Lichen Glossary

It is assumed that the student has a general knowledge of the structure of lichens. A rather full glossary is given, to serve the needs of subsequent articles. Illustrations will also be given with later articles.

• AMORPHOUS, of a cortex formed of indistinct hyphae with thickened walls.
• AMPHITHECIUM, thalline margin of the apothecium. (Fig. 13.)
• APOTHECIUM, an open or disc-shaped fructification. (Figs. 9, 10, 11, 13.)
• AREOLA, small space marked out by lines of chinks on the surface of the thallus.
• ASCOMYCETES, a group of fungi in which the spores (usually 8) are formed inside a more or less pyriform body the ascus. (Fig. 13.)
• ASCUS, an enlarged cell in which a definite number of spores (usually 8) are developed. (Fig. 13, E.)
• ASCYPHOUS, of podetia without SCYPHI. (Fig. 31.)
• AXIL, the inner junction of a branchlet with a branch or with another branchlet. (Fig. 28.)
• BIATORINE, of apothecia that are soft and waxy, and often brightly coloured.
• BYSSOID, slender, thread-like.
• CAPITULUM, a globose apical apothecium as in SPHAEROPHORUS.
• CEPHALODIUM, irregular outgrowth from the thallus enclosing mostly blue-green algae (the thallus itself containing blue-green algae). (Fig. 7, 14.)
• CHLOROPHYCEAE, a group of Algae in which the chloroplasts are bright green.
• CHLOROPLASTS, the individual plastids or “granules” containing chlorophyll, of an agla or a higher plant.
• CHONDROID, hard and tough like cartilage, applied to strengthening hyphal strands. (Fig. 19.)
• CILIUM, hair-like outgrowth from the surface or margin of a thallus, peculiar to the STICTACEAE. (Fig. 5.)
• DECOMPOSED, of a cortex formed of gelatinous indistinct hyphae.
• DETERMINATE, of a thallus with a definite outline.page 28
• DIMIDIATE, of a perithecium when the outer wall covers only the upper portion.
• ENDOGENOUS, produced internally, as spore in an ascus. Used also of a thallus in which the algae predominate.
• ENTIRE, of a perithecium completely surrounded by an outer wall.
• EPIPHLOEODAL, of a thallus growing on the surface of bark.
• EPITHECIUM, upper layer of the thecium. (Fig. 13, C.)
• EXOGENOUS, produced externally as spore on the tips of hyphae. (Fig. 29.) Used also of a thallus in which the fungus predominates.
• FASTIGIATE, of a cortex formed of clustered parallel hyphal branches perpendicular to the long axis of the thallus.
• FIBROUS, of a cortex formed of hyphae parallel to the long axis of the thallus.
• FOLIOSE, of lichens with a leafy form and stratose in structure. (Fig. 32.)
• FOVEOLATE, pitted. (Fig. 35.)
• FRUTICOSE, of an upright or pendulous thallus, mostly with radiate structure. (Fig. 28.)
• GONIDIA, the agal constituents of the thallus (Fig. 9); sometimes restricted to the green algae, the term for blue-green algae then being GONIMIA.
• GYROSE, curved backward and forward, used of the furrowed fruit of certain species of UMBILICARIA.
• HETEHOMEROUS, when the fungal and alga constituents are in definite strata, as in PARMELIA.
• HOLD-FAST, attachment organ of thallus. (Fig. 30.)
• HOMIOMEROUS, when the fungal and algal constituents are more or less mixed, as in COLLEMA.
• HYMENIUM, apothecial tissue consisting of asci and paraphyses. (Fig. 13.)
• HYMENOMYCETES, a group of fungi in which the spores are borne in groups of 4 on undivided basidia or stalks.
• HYPHAE, the thread-like branches of the vegetative part of a fungus.
• HYPOPHLOEODAL, of a thallus growing within the bark.
• HYPOTHALLUS, the first growth of hyphae persisting as a hypal growth at the base or margin of the thallus.
• HYPOTHECIUM, the layer below the thecium. (Fig. 13, G.)
• INTRICATE, of a cortex in which the hyphae are densely interwoven, but not coalescent.
• ISIDIA, coral like outgrowths on the thallus. (Fig. 17.)page 29
• LECANORINE, of an apothecium with a thalline margin. (Fig. 26.)
• LECIDEINE, of a thallus, usually dark coloured, without a thalline margin. (Fig. 11.)
• LEPROSE, mealy or scurfy.
• LIRELLA, a narrow long apothecium, as in the GRAPHIDACEAE.
• MAZAEDIUM, a fructification where the spores lie as a powdery mass in the capitulum, as in SHAEROPHORAS.
• MEDULLA, the loose hypal layer in a thallus. (Fig. 5.)
• MULTI-SEPTATE, of spores with numerous transverse septa.
• MURIFORM, of spores divided like a brick-work wall.
• MYXOPHYCEAE, a group of algae in which the chloroplasts are blue-green.
• NOSTOC-LIKE, resembling the more or less globular gelatinous colonies of the blue-green alga NOSTOC.
• PALISADE-CELLS, the terminal cells of hyphae forming a fastigiate cortex.
• PANNIFORM, having a felted or matted appearance.
• PARAPHYSES, the sterile filaments of the HYMENIUM. (Fig. 13.)
• PARATHECIUM, hyphal layer round the apothecium. (Fig. 13, F.)
• PELTATE, of orbicular and horizontal apothecia in the form of a shield.
• PERITHECIUM, fructification, usually roundish and with a minute apical opening or OSTIOLE. (Fig. 8.)
• PERVIOUS, of SCYPHI with an opening at the base.
• PLACODIOID, of a thallus with a squamulose determinate outline, more or less orbicular.
• PODETIUM, stalk-like or branched secondary thallus of the CLADONIACEAE. (Fig. 23.)
• POLARILOCULAR, of two-celled spores with a thick median wall, traversed by a connecting tube.
• PROPER MARGIN, the hyphal margin surrounding the apothecium. (Fig. 13, B.)
• PSEUDOCYPHELLAE, point-like eruptions, usually on the lower surface, on the thallus of certain species of STICTA, with extruded hyphal filaments.
• RADIATE, of a thallus in which the tissues radiate from a centre as in USNEA.
• RHIZINE or RHIZOID, attaching “rootlets” on the lower surface of thallus. (Fig. 24.)
• RIMOSE, cleft or chinked into AREOLAE.
• SCYPHUS, cup-like expansion of podetium in CLADONIA. (Fig. 23.)page 30
• SORALIUM, a group of soralia surrounded by a definite margin. (Fig. 16.)
• SQUAMULE, a small thalline lobe or scale. (Fig. 7, 23.)
• STRATOSE, of a thallus with the tissues arrayed in horizontal layers.
• TERETE, rounded in transverse section, as in the branches of USNEA.
• THALLINE MARGIN, of an apothecium with a margin formed of and usually coloured like a thallus. (Fig. 13, A.)
• THALLUS, the vegetative body of a lichen.
• THECIUM, a layer of tissue in the apothecium consisting of asci and paraphyses. (Fig. 13, D.)
• UMBILICUS, the lower point of attachment of a thallus attached to the substratum at a central point only.

Legends to Figures

1.	Lichina, × 5.
2.	Collema, × 20.
3.	Leptogium, × 20
4.	Peltigera, × ½.
5.	Cyphella, × 200.
6.	Pseudocyphella, × 200.
7.	Lecanona, showing lobate squamules and cephalodia, × 4.
8.	Perithecium.
9.	Apothecium, with gonidia in thalline margin.
10.	Apothecium, without gonidia in the thalline margin.
11.	Apothecium, lecideine type.
12.	Single-celled spore.
13.	Apothecium, showing (a) thalline margin; (b) proper margin; (c) epithecium; (d) thecium; (e) ascus; (f) parathecium; (g) hypothecium.
14.	Cephalodium, on normal thallus.
15.	Soredium.
16.	Soralium.
17.	Isidia.
18.	Two-celled spore.
19.	Usnea, transverse section showing central chondroid cylinder.
20.	Cortex, with hyphae parallel to surface.
21.	Cortex, with hyphae perpendicular to surface.
22.	Anzia, showing spongy outgrowth below.
23.	Cladonia, with basal squamules and podetium enlarging above into scyphus.
24.	Peltigera, under surface showing “veins” and rhizines.
25.	Cladonia (Clathrina), showing perforated branches of podetia.
26.	Apothecia of lecanorine type.
27.	Teloschistes, showing ciliate apothecia and branches.

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28.	Usnea rubescens, showing holdfast, × 2/3.
29.	Cladonia scabriuscula, × 2/3.
30.	Cladonia cornutoradiata, × 2/3.
31.	Ramalina leiodea, × 2/3.
32.	Sticta filix, × 2/3.
33.	Sphaerophorus australia, × 2/3.

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34.	Sticta coronata, × 2/3.
35.	Sticta impressa, × 2/3.
36.	Lobaria adscripta, × 2/3.
37.	Parmelia caperata, × 2/3.
38.	Xanthoria parietina, × 2/3.
39.	Collema leucocarpon, × 2/3.

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