Part 14

The æcidia of many Rust-Fungi were formerly considered as distinct genera. The æcidia of _Phragmidium_, _Triphragmium_, and _Melampsora_, in which the _peridium is wanting_, were in part considered as _Cæoma_. The æcidia with fimbriate edge, or those of _Gymnosporangium_ with longitudinal lattice-like splits, were considered as “_Rœstelia_” (Lattice-Rust); large, sac-shaped æcidia on the Coniferæ were known as _Peridermium_.

The ~UREDOSPORES~ (_Summer-spores_) are unicellular and arise singly, seldom in chains (_Coleosporium_). Their colourless, warty exospore bears, _in the equatorial plane_, 2–8 _germ-pores_. In the majority, _germination_ proceeds _immediately_, and a mycelium is produced which at first gives rise to uredospores and afterwards to teleutospores.

The uredospore-formations of _Melampsorella_ and _Cronartium_ are enclosed in an _envelope_, and hence resemble æcidia.--Between the uredospores sterile, unicellular hyphæ (paraphyses) may be found.

The _spermogonia_ are spherical or pear-shaped _conidiocarps_, generally embedded in the substratum, and are produced before the æcidia, before or simultaneously with the uredospores, or before the teleutospores. The conidia, as far as observations go, do not generally germinate under ordinary conditions.

Among the Rust-Fungi some species are found which only form basidiospores and teleutospores (_Puccinia malvacearum_, _Chrysomyxa abietis_). Other species have in addition uredospores; others spermogonia and uredospores; others spermogonia and æcidia; others spermogonia, uredospores and æcidia. Those species in which all the methods of reproduction are not developed must not be considered as incomplete forms.

As a rule the mycelium, which is produced from the basidiospores, developes æcidia; in the species, however, without æcidia, it developes the uredo-form, and when the uredospores are also absent, the teleutospore-form. It has been established in some species of _Puccinia_ and _Uromyces_ that the formation of æcidia can be suppressed, and it is not a necessary part of the cycle of development of the species.

The majority of Rust-Fungi hibernate in the teleutospore-form. Many species are able to hibernate in the uredospore-form (_Coleosporium senecionis_). Others pass the winter in the æcidio-form, and develope æcidia on new hosts (_Uromyces pisi_, on _Euphorbia cyparissias_; _Phragmidium subcorticium_, on _Rosa_; _Æcidium elatinum_, on _Abies alba_). In _Chrysomyxa abietis_, the mycelium, developed from the basidiospores, survives the winter.

Among the Rust-Fungi, with several forms of reproduction, there are about sixty whose development can only be completed by an _alternation of hosts_, that is, on one host only uredo-and teleutospores are produced, while the further development of the germinating basidiospores, and the formation of the æcidia and spermogonia from its mycelium, can only take place on a second quite distinct and definite host (_heterœcious_ or _metoxenous_ Fungi). Those Fungi which have all their forms of reproduction on the same host are termed _autœcious_ or _autoxenous_. It is not, however, always necessary that the heterœcious Rust-Fungi should regularly change their hosts; for example, _Puccinia graminis_ can hibernate in the uredo-form on the wild Grasses, and in the spring can distribute itself again in the same form.

As a consequence of the alternation of hosts the various forms of development were considered as independent genera (_Uredo_, _Æcidium_, _Rœstelia_, _Cæoma_, _Peridermium_), until De Bary and Oersted established, about the same time (1865), the mutual connection of some forms, and paved the way for the right conception of these Fungi.

As an example of one of the most highly developed species, _Puccinia graminis_, the “Rust of Wheat,” holds a prominent position. Its uredospores and teleutospores are produced (Fig. 146) on Grasses (on cereals, especially Wheat, Rye, Oats, and many wild Grasses), while the æcidia and spermogonia are confined to the Berberidaceæ. The teleutospores, developed on the Grasses, hibernate on the dried portions of their host, and in the succeeding year each of the two cells of the teleutospore may develop a _basidium_ with four basidiospores (Fig. 146 _D_, _c_). The basidiospores are distributed by the wind, germinate quickly, and only proceed to further development on _Berberis_ or _Mahonia_. The germ-tube _bores through the epidermis_ of the Barberry-leaf, and forms a mycelium in its interior, its presence being indicated by reddish-yellow spots on the leaf. After 6–10 days the flask-shaped _spermogonia_ appear (Fig. 147 _B_; _C_, _a_; conidia in Fig. 147 _D_) and a few days later the cup-shaped _æcidia_ (Fig. 147 _A_; _C_, _c_, _d_, _e_). The former are generally on the _upper_, and the latter on the _under side_ of the leaf. The orange-coloured æcidiospores scatter like dust, and germinate only on Grasses; the germination takes place in about two days when placed on any green part of a Grass. The germ-tube enters the Grass-leaf through a stoma; a mycelium is developed in the leaf, giving rise to a small, oval, rust-coloured spot (Fig. 146 _A_); in about 6–9 days the epidermis is ruptured over the red spot, and numerous reddish-yellow _uredospores_, formed on the mycelium, are set free. The uredospores (Fig. 146 _B_) are scattered by the wind, and can germinate should they fall on the green portions of other Grasses: they then emit 2–4 germ-tubes through the equatorially-placed germ-pores. The germ-tubes enter a leaf through a stoma, a new mycelium is then developed, and in about eight days a fresh production of uredospores takes place, which germinate as before. The uredospore-mycelium very soon produces, in addition, the brown _teleutospores_, which give a brown colour to the rust-coloured spots, the familiar uredospores on the cereals being quite suppressed towards the close of the summer (Fig. 146 _C, D_). The “Rust of Wheat” hibernates on some wild Grasses in the uredospore-form.

GENERA. _Puccinia_ (Fig. 146, 147) has bicellular teleutospores, each having a germ-pore, and the æcidia when present have an indented peridium; some species, as exceptions, have 1–3-celled teleutospores. Many species are HETERŒCIOUS, for example, _P. graminis_, described above; _P. rubigo_, which also infests various Grasses, but whose æcidia appear on _Anchusa_; the masses of teleutospores are small; they contain paraphyses, and are for a long time covered by the epidermis. _P. coronata_, on Oats and Rye Grass; its æcidia on _Rhamnus_; the teleutospores are surmounted by a crown--“coronate processes.” _P. phragmitis_, on Reeds; æcidia on species of _Rumex_ and _Rheum_. _P. moliniæ_, on _Molinia cœrulea_; the æcidia on Orchids. _P. poarum_, on Meadow-Grass; æcidia on _Tussilago_. Various Puccinias growing on species of _Carex_ have their æcidia on _Urtica_, _Lysimachia_, _Cirsium_, _Pedicularis_, etc.--Of those AUTŒCIOUS species, which have all their generations on the same host, may be noted:--_P. galii_, _P. menthæ_, _P. violæ_, _P. epilobii_, _P. asparagi_, which grow on the hosts from which they have taken their specific names.--As representative of a group which have spermogonia, uredo-and teleutospores on the same host, but on different individuals, _P. suaveolens_, on the Field-Thistle, may be mentioned. The spermogonia have a strong odour.--A peculiar group (_Leptopuccinia_) has only teleutospores, which germinate immediately, and whilst still attached to their living host. To this group belong _P. arenariæ_, on a number of Caryophyllaceæ; and _P. malvacearum_, on various Malvaceæ, introduced in 1873 from South America to Europe, where it soon proved very destructive to Hollyhocks.

_Uromyces_ (Fig. 149) differs only from _Puccinia_ in always having unicellular teleutospores. Among this genus both heterœcious and autœcious species are found. To the first group belong _U. pisi_, whose æcidia are found on _Euphorbia cyparissias_, and _U. dactylidis_, whose æcidia appear on _Ranunculus_; to the second group belong _U. betæ_, _U. phaseoli_, _U. trifolii_.

_Triphragmium_ has teleutospores with three cells (one below and two above), on _Spiræa ulmaria_.

_Phragmidium_ (Fig. 150) has teleutospores consisting of a row of cells (3–10) arranged in a straight line; the upper cell has one germ-pore and the others four germ-pores placed equatorially. Both this and the preceding genus have large, irregular æcidia without peridia, but often with bent, club-like paraphyses (150 _b_ and _c_); they are all autœcious, and are only found on the Rosaceæ.

_Endophyllum_ (see above, under teleutospores, p. 147) on species of _Sempervivum_.

_Gymnosporangium_ (Figs. 152, 154) has bicellular teleutospores collected in large, gelatinous masses formed by the swelling of the long spore-stalks; in each cell 2–4 germ-pores are found. Uredospores are wanting. All the species are heterœcious; the teleutospores appear on _Juniperus_, the æcidia (_Rœstelia_) on the Pomaceæ. _G. sabinæ_, on _Juniperus sabina_, _J. virginiana_, etc., has the æcidia (“_Rœstelia cancellata_”) on _Pyrus communis_ (Figs. 152, 148); _G. juniperinum_, on _Juniperus communis_ with “_Rœstelia cornuta_” (Fig. 154 _a_) on _Sorbus aucuparia_, _Aria nivea_ (_S. aria_) and _Malus communis_; _G. clavariæforme_ on _Juniperus communis_, the æcidium belonging to it (“_Rœstelia lacerata_”) on _Cratægus oxyacantha_.

_Melampsora_ has prismatic teleutospores placed parallel to each other and forming a crustaceous layer; in many species they are divided longitudinally into several cells (Fig. 151). The æcidia, without peridium, belonged to the old genus _Cæoma_. _M. caprearum_, on Willows, has the æcidia (_Cæoma euonymi_) on _Euonymus_. _M. hartigii_, on Osiers; the æcidium on _Ribes_. _M. mixta_, on _Salix repens_ and Orchids. _M. pinitorqua_, on leaves of the Aspen, æcidia on Pine branches (Pine shoot fungus); _M. populina_ on _Populus monilifera_ and _nigra_; _M. betulina_ (Fig. 153), on Birch leaves; _M. padi_ (Fig. 151), on leaves of _Prunus padus_, developes teleutospores in the epidermal cells; _M. lini_ is the cause of injury to the Flax; _M. agrimoniæ_.

_Calyptospora gœppertiana_; teleutospores on _Vaccinium vitis idæa_; spermogonia and æcidia on _Abies alba_ (Firneedle-Rust).

_Coleosporium_ (Fig. 155) forms its uredospores in reddish-yellow chains; for the teleutospores, see page 147. _C. senecionis_, on the Groundsel; its æcidium (_Peridermium wolffii_) on Pine-leaves (Fig. 155 a). Other species on _Sonchus_, _Petasites_, _Campanula_, _Rhinanthaceæ_.

_Chrysomyxa_ (Fig. 156) has bright red, branched teleutospore-chains; each spore developes a 4-celled basidium. _C. ledi_, on _Ledum palustre_; its æcidia on the leaves of the Fir. _C. abietis_ (Fig. 156), without uredo-and æcidiospores; teleutospores on the leaves of the Fir. In the first summer, yellow bands are formed on the leaves, and in the following spring the red cushions of spores.

_Cronartium_ (Figs. 157, 159) has unicellular teleutospores united in numbers to form erect threads or columns; the uredospores are enclosed in a “peridium”; _C. ribicola_ (Fig. 157), on leaves of Ribes (especially Black Currants); its æcidia (_Peridermium strobi_, or _P. klebahni_) on the stems and branches of _Pinus strobus_ (Fig. 159), on which it causes great damage; _C. asclepiadeum_, on _Vincetoxicum officinale_; its æcidia (_Peridermium cornui_) on the stems and branches of _Pinus silvestris_.

To the Fungi of which the æcidium is known, whilst the remaining forms are still undetermined, but which are without doubt heterœcious, belong _Æcidium elatinum_, which produces the enormous “witches’ brooms” and barrel-shaped swellings on stems and branches of _Abies alba_; and _Æcidium strobilinum_ (Fig. 158), which attacks Fir-cones, causing all the scales to become covered with clusters of æcidia opening by a lid. _Hemileia vastatrix_ destroyed the coffee plantations in Asia.

Order 2. =Auriculariaceæ.= The _long, transversely divided_ basidia bear laterally 4 _long sterigmata_ with basidiospores (Fig. 160 _B_) and are united to form an _hymenium_ on the surface of the fruit-body. Parasites or saprophytes.

_Auricularia sambucina_ (_Auricula judæ_), Judas’-ear, has large fruit-bodies, which may attain the size of several inches, resembling an ear or a mussel shell. In the moist condition they are flesh-coloured, tough and gelatinous, but when dried, become hard, grey and wrinkled; the exterior is covered with short hairs; while the internal surface bears the hymenium. Habitat: stems and branches of old Elder-trees (_Sambucus_).

Order 3. =Tremellaceæ.= The _round, pear-shaped, longitudinally divided basidia_ bear 4 _elongated sterigmata_, situated apically, and 4 basidiospores (Fig. 160 _C_, _D_), and are united into the _hymenium_ on the surface of the fruit-body. The fruit-bodies are frequently gelatinous and quivering; similar fruit-bodies are also found in the Dacryomycetaceæ and Hydnaceæ. Simple conidiophores, which appear not infrequently in the basidiocarps, before the basidia, are known in many species. Saprophytes.

_Exidia_ has kidney-shaped, oblong basidiospores, and small, hook-like conidia; _E. glandulosa_, _E. albida_, etc., on wood.--_Craterocolla_ has conidiocarps; _C. cerasi_ on Cherry-wood.--_Sebacina incrustans_; the yellow, fleshy, or cartilaginous fruit-bodies are found in autumn covering the ground in moist woods.--_Tremella_ has round basidiospores; _T. mesenterica_ has irregularly-folded, quivering, orange fruit-bodies, about one inch in breadth; _T. lutescens_ (Fig. 161) has orange-yellow conidial-and yellow basidial-layers; _T. frondosa_ has fruit-bodies upwards of a foot in breadth.

Order 4. =Pilacraceæ.= The _transversely divided basidia_ have _no sterigmata_, but sessile basidiospores, and fill up the cavity of a _closed_ (_angiocarpic_) _fruit-body_ as a gleba without a regular arrangement (hymenium wanting).

_Pilacre fagi_ on the old stems of the Copper-Beech; _P. petersii_, on dried branches of the Hornbeam, has stalked, capitate fruit-bodies.

Series 2. =Autobasidiomycetes.=

This second and larger part of the Basidiomycetes is characterised by its more highly differentiated, _undivided_, club-shaped, or cylindrical basidia, which generally bear 4 (seldom 2, 6, 8) apically-placed sterigmata and basidiospores (Fig. 145). The fruit-bodies are partly _gymnocarpic_ (in the first 3 orders and in some Agaricaceæ), partly _hemiangiocarpic_ (in orders 3–6 of the Hymenomycetes and in the Phalloideæ, the fruit-bodies in these orders are in the young conditions more or less angiocarpic, but later on generally open below and bear the hymenium on the under surface of the fruit-body), partly also _angiocarpic_ (in the Gasteromycetes).

Family 1. =Dacryomycetes.=

The _long, club-shaped basidia_ bear _two tapering sterigmata_, which develope remarkably large basidiospores (Fig. 162 II, XI) and form _gymnocarpic_ fruit-bodies with hymenium. 1 order:

Order 1. =Dacryomycetaceæ.= This order comprises 4 genera of which the first two develope the hymenium on the whole surface of the fruit-body, but the two last only on its apex.

_Dacryomyces_: the folded, gelatinous, _Tremella_-like fruit-bodies break out in winter on dried wood (hedges) in the form of red or yellow drops. _D. deliquescens_ is very common (Fig. 121). The following genera have cartilaginous fruit-bodies.--_Calocera_ (Fig. 162), with club-like, simple, or branched, _Clavaria_-like, fruit-bodies; the orange coloured fruit-bodies of _C. viscosa_ grow aggregated together on the wood of Conifers.--_Guepinia_ resembles a _Peziza_, and has the hymenium only on the hollow upper surface.--_Dacryomitra_ resembles a _Mitrula_ (Fig. 162).

Family 2. =Hymenomycetes.=

This family is very rich in species (more than 8000 have been described), and to it belong all the “Mushrooms” and “Toadstools.” The _fruit-bodies_ present very various forms; they are generally fleshy, very perishable, seldom leathery or corky, in the last case often perennial. The _basidia_ are more or less _cylindrical_ and bear _generally_ 4 (seldom 2, 6 or 8) _sterigmata and basidiospores_. The hymenium in the fully-formed fruit-bodies lies free on the surface: in orders 1 and 2 and a portion of order 6 it is from the commencement exposed, fruit-bodies _gymnocarpic_; orders 3–6 have _hemiangiocarpic_ fruit-bodies (p. 157). In the first order the basidia (or the hymenium) are developed immediately from the mycelium (Fig. 163); the fruit-bodies of orders 2 and 3 present a higher grade of development, and have between the mycelium and hymenium a special hyphal-tissue, a _stroma_, which is crustaceous, club-like, or coralloid, etc., and in general bears the hymenium on the largest part of the free, smooth surface. In the forms most highly developed (orders 4–6) a new tissue--the _hymenophore_--is introduced between the stroma and hymenium, which appears on the under side of the fruit-body in the form of warts, projections, tubes, folds or lamellæ (Figs. 166, 167, 174 _bc_). _Paraphyses_ are frequently found in the hymenium, among the basidia. In the Hymenomycetes few examples of _conidia_ can be recognised at first. More frequently _chlamydospores_ are found, particularly _oidia_. The _mycelium_ is richly branched, generally colourless, often perennial; it lives in humus or decaying wood, and is seldom parasitic. The hyphæ generally have clamp-connections and unite, sometimes, to form a rhizomorpha (Fig. 177) or sclerotia with coloured, pseudo-parenchymatous covering.

Order 1. =Tomentellaceæ.= To this order belong the simplest of the Hymenomycetes. The basidia (Fig. 145) arise free and irregularly from the mycelium; a _hymenium_ is _entirely absent_ or _very slightly formed_ (in _Corticium_ it attains its highest development); _fruit-bodies_ are _also wanting_.--In general they form flaky, membranous or leathery coverings on bark and wood. Some are parasites.

_Hypochnus_ without conidia.--_Tomentella_ with conidiophores; growing on wood or earth.--_Exobasidium vaccinii_ (Fig. 163), a parasite on _Vaccinium_, _Andromeda_, _Arctostaphylos_, and _Rhododendron_, forms flaky-powdery, white or red coverings and may cause hypertrophy of the parts attacked. _E. warmingii_ is parasitic on _Saxifraga_; _E. lauri_ causes outgrowths on the stem of _Laurus canariensis_ as long as a finger, which formerly were regarded as aerial roots.--_Corticium_ forms membranous to leathery layers or crusts; _C. quercinum_ on wood and bark, particularly Oak, is flesh-coloured; _C. cæruleum_ has a blue hymenium; _C. giganteum_ on the bark of fallen Pine-trees.