Part 13

Order 6. =Bulgariaceæ.= Apothecia gelatinous under moist conditions, and horny when dried.--_Calloria fusarioides_; the red apothecia break out in the spring on the dried stalks of _Urtica dioica_; a gelatinous reproductive form of the Fungus is found before the apothecia, which consists of oidia (formerly described as “_Dacryomyces urticæ_”).--_Bulgaria inquinans_ on the living or fallen trucks of Oaks and Beeches.

Sub-Family 5. =Pezizales.=

_The apothecia are developed on the surface of the substratum and are waxy or fleshy_; at the commencement closed, and covered with a saucer- or cup-shaped, seldom flat, hymenium. The _hypothecium_ is generally well developed. This sub-family is the richest in species of the Discomycetes and contains forms of very different habit. They grow upon dead wood, upon the ground, and upon dung. A few are parasites.

Order 1. =Helotiaceæ.= Apothecia with waxy envelope of colourless, or yellowish prosenchymatous cells.--~_Chlorosplenium æruginosum_ is found on decaying wood (particularly Oak and Birch), to which it gives a green colour. _Sclerotinia_ has sclerotia which are developed upon the host-plant and from which, after a period of rest, the long, brown-stalked apothecia arise. _S. ciborioides_ (_S. trifoliorum_, Fig. 128) is parasitic on Clover; _S. sclerotiorum_, on _Daucus_-roots, _Phaseolus_, etc.; _S. baccarum_, on the berries of _Vaccinium myrtillus_; “_Botrytis cinerea_” is a common parasite and is probably the conidial form of _S. fuckeliania_ (Fig. 127).--_Helotium herbarum_ lives on dry plant stems.--_Dasyscypha willkommii_ (Fig. 129) produces Larch-canker on the bark of the Larch.~

Order 2. =Mollisiaceæ.= _Mollisia cinerea_, principally on decaying wood.

Order 3. =Pezizaceæ.= This order contains the largest and morphologically the highest forms of the _Discomycetes_. Apothecia fleshy, and in the later conditions generally saucer-shaped.

_Peziza_, with sessile apothecia, growing on the ground; _P. cochleata_ is brown, and coiled like a snail-shell; _P. coccinea_ is scarlet; _P. aurantia_ occurs as an orange-coloured expansion on the ground.

Order 4. =Ascobolaceæ.= Apothecia fleshy; in the later stages flat or convex. The asci are, comparatively speaking, large, and often contain a great number of spores which escape by the casting off of a lid on the summit of the ascus. Generally living on dung.--_Ascobolus furfuraceus_, etc.

Family 6. =Helvellales.=

These Fungi have the appearance of clubs, bells, or mushrooms, consisting of an upright _stalk_ bearing a _large and fleshy_ head, on the _exterior surface_ of which the _hymenium_ is spread. The ascocarps are probably gymnocarpic from the beginning, and on this account these plants are placed in a separate family. The development of the ascocarps is unknown. The _Morchella_ (Morell) grows on the ground; some species are edible. 1 order.

Order. =Helvellaceæ.= _Spathulea_ is yellow and club-shaped, and forms “fairy rings” in woods.--_Geoglossum_ (Earth-tongue) projects above the ground as a black tongue, or as a club-shaped body. Several species are found in meadows and on heaths.--_Helvella_ has a stalk, bearing an irregularly folded head, on the external surface of which is the hypothecium.--_Morchella_ (Morell, Fig. 130), the stalk bears on its summit the conical or spherical head, the external surface of which is reticulate and bears the asci.--_Mitrula. Verpa._

APPENDIX TO THE ASCOMYCETES:

Family 7. =Ascolichenes (Lichen-forming Ascomycetes).=

The Lichens were formerly classed among the Thallophyta as a group quite distinct from the Algæ and Fungi. Investigations during the last twenty-five years, however, have conclusively proved that the Lichens are Fungi which reproduce in the same manner as the Ascomycetes, or, more rarely, the Basidiomycetes, and have entered into a peculiar _symbiotic relation with Algæ_, especially the Cyanophyceæ and Protococcoideæ, with which they associate, and without which they would be unable to exist. The Fungus forms the largest portion of the Lichen, enclosing the Alga with which it may be said to be commensal. The Fungus especially produces reproductive bodies and absorbs the inorganic nourishment through the rhizoids, whilst the Alga supplies it with the organic materials. In consequence of this the Lichens, in contradistinction to other Fungi, need light for the development of their nutritive organs, and are therefore, in any case internally, of a more or less greenish colour. The form and condition of the thallus is unusual among the Fungi, and they can grow upon rocks and in other places where no dead organic matter, such as would be required by other Fungi, is obtainable.

Two cellular forms are therefore to be found in each Lichen:

1. The cells which belong to the Fungus. These are generally septate, branched _hyphæ_ without any trace of chlorophyll. In the thallus of the majority of Lichens there may be found a medullary layer (Fig. 131 _m_) of loosely-woven hyphæ, between which there are large air chambers; and an _external layer_ (cortex) (Fig. 131 _o_, _u_) formed of closely-woven hyphæ without any intercellular spaces. In some Lichens (Collemaceæ) the hyphæ wind about in the thallus, being equally distributed throughout, without forming any decided strata. These Lichens moreover become gelatinous when exposed to moisture (Fig. 132), on account of the swelling of the walls of the Algæ. The hyphæ contain protoplasm with drops of oil, but never starch; their walls easily swell when exposed to damp after having been dried, and in some (_e.g._ _Cetraria islandica_) they become gelatinous when cooked. Certain strata of hyphæ become blue on treatment with iodine alone, from which it is inferred that the wall is allied, in its chemical nature, to starch.

2. The enclosed Algæ, termed “gonidia.” Some belonging to the Cyanophyceæ, Protococcoideæ, (especially _Pleurococcus_) and Chroococcaceæ, are spherical and are found isolated, or in irregular _groups_ of cells (Fig. 131 _g_); some belonging to _Nostoc_ (Fig. 132 _g_), Lyngbyaceæ, etc., are placed in cell-rows. Each Lichen, as a rule, has only one definite Algal-form for its gonidium.

The gonidia either lie together in a certain stratum between the cortex and the medullary layer (Fig. 131 _g_), or are scattered irregularly throughout the entire thallus (Fig. 132). The thallus is in the first instance termed “heteromerous,” in the second instance, “homoiomerous.” The Fungal-hyphæ embrace the gonidia and apply themselves closely to, or even penetrate them, and hence it has been difficult to decide whether the one cellular form does or does not develop from the other (Figs. 134, 135).

This theory regarding the symbiosis of Fungi and Algæ to form a Lichen is termed the Schwendenerian theory, after the first scientist who advanced it with any weight. It had been already indicated by De Bary, and further arguments in its support have at a later time been adduced by Bornet, Stahl, Treub, Frank, Bonnier, Alfr. Möller and others.

The thallus of the Lichen appears mainly under three forms:--

1. The CRUSTACEOUS, which adheres firmly to the substratum (bark, stone) throughout its entire surface, without being raised into any free patches or lobes. It has, in many instances, no definite outline, and hyphal-branches from it often penetrate deeply into the substratum. It grows at the circumference and sometimes dies away in the centre (Figs. 138, 139, 140).

2. The FOLIACEOUS. This also lies flat upon the substratum, but is not firmly attached to and has a definite outline. It grows at the margin, and raises itself a little by free outgrowths and lobes (Fig. 141). The rhizoid-strands spring out from its whitish under surface (Fig. 131, _r_).

3. The FRUTICOSE, which is attached to its substratum at a small point from which it projects freely, either erect or pendulous. It is more or less tufted, in the form of a bush (Figs. 142, 143). These three thallus-forms gradually pass over by many intermediate forms into one another.

The Lichens, like other Ascomycetes, have very variously constructed ascospores (Fig. 137), which are enclosed in asci (Fig. 136), usually surrounded by paraphyses attached together. Furthermore they possess pycnidia (Fig. 141) containing numerous microconidia. These were formerly considered as organs of fructification, and were termed “spermatia,” and the pycnidia, “spermogonia.” Alfr. Möller proved, in 1887, that the microconidia are able to germinate and produce a mycelium with new conidia, just as in other Ascomycetes.

VEGETATIVE REPRODUCTION takes place by _soredia_, which to the naked eye appear as whitish powder on the surface of the thallus. They are small round bodies, formed by one or a group of gonidia, which are surrounded by a mass of felted hyphæ. After the rupture of the cortex they are set free, and readily carried by the wind to other places, where under favourable circumstances they establish a new thallus.

GEOGRAPHICAL DISTRIBUTION. The Lichens are the most hardy plants, and are the first to appear on hitherto bare rocks which they gradually disintegrate, and hence prepare the way for the growth of other plants. They are to be found from the Polar regions to the Equator; from the highest snow-free mountain-peaks down to the level of the sea; on the stems of trees; on rocks, soil, some even on inundated places; on stones in woodland streams, and on beaches; but they are never found upon rotten organic remains. Some grow gregariously in enormous masses, and form wide-stretching carpets, _e.g._ Reindeer Moss (_Cladonia rangiferina_), species of _Cetraria_ and other fruticose Lichens.

USES. On account of the cell-wall being composed of Lichenstarch (Lichenin), the Iceland-Lichen and Manna-Lichen (_Lecanora esculenta_) are used as food; the latter grows on stones, in the deserts of Asia and North Africa, and is often torn loose in large masses and carried away by the wind. The Reindeer-Lichen is not only the principal food of the reindeer, but it is also used in the manufacture of Danish brandy. _Cetraria islandica_ (Lichen islandicus) is OFFICINAL. Colouring materials (lacmus, orseille, persio) are made from several species, especially from _Roccella tinctoria_ (from the rocky coasts of the Mediterranean). _Parmelia saxatilis_ and particularly _Lecanora tartarea_ are used for colouring purposes in the Northern countries.

About 2,000 species of Lichens have been described. If we disregard the Basidiolichenes, which will be considered on page 176, the remaining Lichens (Ascolichenes) may be divided into the two following orders according to the structure of the fruit-bodies:--

Order 1. =Pyrenolichenes.= The ascocarps (apothecia) are spherical or flask-shaped, as in the Pyrenomycetes, more rarely linear (_Graphis_).

According to the nature of the thallus, these Lichens may be divided into:--

_a._ Thallus homoiomerous, but not gelatinous, branching according to the mode of growth of the Algæ: _Ephebe_ (Fig. 133), with Algæ of the genus _Stigonema_.

_b._ Thallus homoiomerous, gelatinous: _Lichina_.

_c._ Thallus heteromerous, crustaceous: _Verrucaria_, _Pyrenula_; _Graphis_ (Fig. 139), which may be considered as Hysteriaceæ with gonidia; several species of _Graphis_ are common on bark.

_d._ Thallus heteromerous, foliaceous: _Endocarpon_.

_e._ Thallus heteromerous, fruticose: _Sphærophorus_.

Order 2. =Discolichenes.= These, as in the Discomycetes, have open apothecia, which, as a rule, are cupular, more rarely hemispherical (_Cladonia_).

According to the nature of the thallus, these Lichens may be divided into:--

_a._ Thallus homoiomerous, but not gelatinous, branching according to the mode of growth of the Algæ: _Cœnogonium_.

_b._ Thallus homoiomerous, gelatinous: _Collema_ (Fig. 132), with Algæ of the genus _Nostoc_; _Leptogium_.

_c._ Thallus heteromerous, crustaceous: _Pertusaria_ (Fig. 140), _Lecidea_, with apothecia open from the beginning; _Lecanora_, with apothecia, which in the beginning are closed, later on open, but with a rim formed by the thallus (Fig. 138); _Bæomyces_, whose apothecia are borne on a stem formed by the thallus.

_d._ Thallus heteromerous, foliaceous: _Parmelia_ (_P. saxatilis_; _P. parietina_, Wall-Lichen, Fig. 141, is yellow, very frequent on tree-stems, stone-walls, tiles); _Physcia_ (_P. ciliaris_, frequent on tree-stems); _Sticta_ (_S. pulmonacea_, Lung-Lichen, on tree-stems); _Peltigera_, especially on the Moss among trees; _Umbilicaria_, on rocks.

_e._ Thallus heteromerous, fruticose: _Cetraria_ (_C. islandica_), “Iceland Moss,” with an olive-brown, flat, furrowed, fringed thallus, on heaths; _C. nivalis_, white, in the Polar regions; _Evernia_, _Ramalina_, _Usnea_ (_U. barbata_, Beard-Lichen, Fig. 143); _Roccella_, _Stereocaulon_, _Cladonia_, of which the genus _C. rangiferina_, Reindeer-Moss (Fig. 142) is important; _Cladonia_ has two kinds of thallus, one scaly and leaf-like, the other erect, which bears the apothecia and may be fruticose (Fig. 142), or cupular (Fig. 144); they grow in soil in forests and on heaths.

Sub-Class 2. =Basidiomycetes.=

This sub-class embraces the most highly developed Fungi, with large “fruit-bodies,” which in ordinary language we shortly term Funguses, Toadstools, or Mushrooms.

They have no sporangia, but reproduce only by means of basidiospores, conidia, chlamydospores and oidia. The chief characteristic of this sub-class is the _basidium_ (Fig. 145), _i.e._ the conidiophore, which has a distinctive form, and bears a definite number (generally 4) of characteristically shaped conidia (basidiospores, Fig. 145 _c_, _d_, _e_).

The summit of each basidium is produced generally into four conical points (_sterigmata_, Fig. 145 _b_), from each of which a basidiospore is abstricted. The basidia may be classified into three principal groups, each of which accompanies a distinctive conidiophore: 1, the long, filamentous, _transversely divided_ basidia, with lateral sterigmata and spores, found in the Uredinaceæ (Figs. 146 _D_, 153), Auriculariaceæ (Fig. 160 _B_), and Pilacraceæ; 2, the spherical, _longitudinally divided_ basidia of the Tremellaceæ (Figs. 160 _C d_; 161 iii. iv.); and 3, the ovoid, or cylindrical, _undivided_ basidia of the Autobasidiomycetes (Figs. 145, 163, etc.); the two last have apical sterigmata and spores.

The first two groups are the septate basidia (_protobasidia_), of the _Protobasidiomycetes_; while the unseptate basidia (autobasidia) of the _Autobasidiomycetes_ are the third group. On the formation of the basidiospores, the nucleus of the basidium divides into four nuclei, each of which is transferred to a spore.

In addition to the basidia, _simple conidiophores_ are also found. In the Protobasidiomycetes, the simple conidia are very generally found as accessory methods of reproduction in conjunction with the basidiospores; but less frequently in the Autobasidiomycetes, _e.g._ among the Dacryomycetes, Tomentellaceæ, _Heterobasidion annosum_.

The simple conidiophores vary in size, and in the number and shape of the conidia; they, however, resemble the basidia, and are doubtless an early stage in the development of the definitely formed basidia.

Finally, well-defined _chlamydospores_, formed in various ways, appear in the Basidiomycetes as supplementary reproductive bodies (compare p. 90). Among the Protobasidiomycetes, chlamydospores are at present only found among the Uredinaceæ, but in various forms; in the majority of families of the Autobasidiomycetes _oidia_ frequently occur (Fig. 162), but genuine chlamydospores seldom.

In the same species several of the known forms of reproduction may be distinguished.

The _mycelium_ is generally composed of white, branched strands, consisting of numerous felted hyphæ; in some, sclerotia are found.--The great majority are saprophytes; some (particularly all the Uredinaceæ), are parasites.

DIVISIONS OF THE BASIDIOMYCETES.

Series 1. PROTOBASIDIOMYCETES: partly gymnocarpic, partly angiocarpic. „ 2. AUTOBASIDIOMYCETES. Family 1. DACRYOMYCETES: gymnocarpic. „ 2. HYMENOMYCETES: partly gymnocarpic, partly hemiangiocarpic. „ 3. PHALLOIDEÆ: hemiangiocarpic. „ 4. GASTEROMYCETES: angiocarpic. Appended. BASIDIOLICHENES: Lichen-forming basidiomycetes.

Series I. =Protobasidiomycetes.=

To this series belong the lowest of the Basidiomycetes. The _basidia_ appear in two principal forms (1 and 2 on page 144) and are _divided_ into four cells, either transversely or longitudinally, each division forming a sterigma which abstricts a basidiospore. The first three orders, Uredinaceæ, Auriculariaceæ, and Tremellaceæ have _gymnocarpic_ fruit-bodies, while those of the Pilacraceæ, on the contrary, are _angiocarpic_.

Order 1. =Uredinaceæ (Rusts).= All the Rust-Fungi are parasites, their mycelium living in the interior of the stems and leaves of their hosts, causing red, brown, or black spots--hence their name--and malformations, sometimes of considerable size.

The Rust-Fungi are gymnocarpic and destitute of a hymenium; for these reasons they are regarded as the simplest order of the Basidiomycetes. They are entirely parasitic, and their filamentous, branched mycelium ramifies in the intercellular spaces of its host, and often protrudes haustoria into the cells. The mycelium is perennial should it enter a woody tissue; it may also hibernate in the rhizomes of perennial herbs and permeate the shoots springing from them, but in the majority of the Rust-Fungi the mycelium has a very limited growth. The chief means of reproduction of the Rust-Fungi are the _chlamydospores_, which in the more highly developed species occur in three forms, namely, the teleuto-, æcidio-, and uredo-spores. The spores, in the host, are formed immediately beneath its epidermis, which is ruptured on the ripening of the spores, with the production of “rust,” brown, red, or black spots. Those chlamydospores which produce basidia are termed _teleutospores_. The spore on germination produces a _transversely divided basidium_, “promycelium,” on which basidiospores, “sporidia,” generally four in number, are produced on lateral sterigmata. This basidio-fructification is _gymnocarpic_; the basidia neither form a hymenium nor a fruit-body (only _Cronartium_ and _Gymnosporangium_ have a slight indication of a basidio-fructification).

Many Rust-Fungi, in addition to basidiospores, have small, _unicellular conidia_, “spermatia,” which are borne in conidiocarps, “_spermogonia_.”

The ~TELEUTOSPORES~ (_Winter-spores_) may be either unicellular or multicellular; in the majority of cases they are enclosed in a hard outer cell-wall, the exospore, which in some cases is very strongly developed; they have also a long or short stalk, the remains of the spore-bearing hypha. Each cell of the teleutospore has _one germ-pore_ (a thin portion of the wall, for the protrusion of the germ-tube; in _Phragmidium_ and _Gymnosporangium_ there are, however, several germ-pores). The colour of the teleutospores is generally much darker than that of the uredospores, and it is by these that the majority of the Rust-Fungi _hibernate_.

In _Gymnosporangium_, two kinds of teleutospores are found (distinguished by their size and thickness of exospore). In many species of _Puccinia_, the form of the teleutospores varies very much, so that in the same layer spores have been observed with the characteristic form of other, allied genera.--The teleutospores of _Endophyllum_ resemble æcidiospores, since they are united in chains, whose cells are easily separated, and are produced in the interior of a “peridium.” The multicellular teleutospores of _Coleosporium_ function as basidia, and from each cell immediately produce basidiospores.--The teleutospores of _Coleosporium_ and _Chrysomyxa_, differ from other teleutospores in the absence of exospore and germ-pore.

The ÆCIDOSPORES (_Spring-spores_) are produced in chains which are generally enclosed in an _envelope_ of hyphæ, the _peridium_; the _peridium_ enclosing the spores being termed the _æcidium_. The æcidiospores are unicellular, and generally of an orange colour; they are often separated by intermediate cells which wither and so assist in the distribution of the spores. The exospore is made up of minute, radially arranged rods. _Generally germination_ proceeds _immediately_, the æcidiospore producing a germ-tube, which developes into a mycelium bearing either uredo- or teleutospores.