orders of _Coniomycetes_ are produced at the apex of short threads,
either enclosed in a perithecium, or seated upon a kind of stroma.
These are exceedingly variable, sometimes large, and multiseptate, at
other times minute, resembling spermatia. In such genera as are
chiefly epiphytal, in _Septoria_, _Phyllosticta_, and their allies,
the minute spores are enclosed within membranaceous perithecia, and
when mature these are ejected from the orifice at the apex, or are
exposed by the breaking off of the upper portion of the perithecia. In
_Diplodia_ and _Hendersonia_ the spores are larger, mostly coloured,
often very fine in the latter genus, and multiseptate, escaping from
the perithecia by a terminal pore. Probably the species are only
pycnidia of _Sphæriacei_, but that is of no consequence in relation
to our present inquiry. Of stylospores which deserve mention on account
of their singularity of form, we may note those of _Dilophospora
graminis_, which are straight, and have two or three hair-like
appendages at each extremity. In _Discosia_ there is a single oblique
bristle at each end, or at the side of the septate spores, whilst in
_Neottiospora_ a tuft of delicate hairs is found at one extremity
only. The appendages in _Dinemasporium_ are similar to those of
_Discosia_. The spores in _Prosthemium_ may be said in some sort to
resemble compound _Hendersonia_, being fusiform and multiseptate, often
united at the base in a stellate manner. In this genus, as in
_Darluca_, _Cytispora_, and the most of those belonging to the
_Melanconiei_, the spores when mature are expelled from the orifice of
the perithecium or spurious perithecium, either in the form of
tendrils, or in a pasty mass. In these instances the spores are more
or less involved in gelatine, and when expelled lie spread over the
matrix, around the orifice; their ultimate diffusion being due to
moisture washing them over other parts of the same tree, since it is
probable that their natural area of dissemination is not large, the
higher plants, of which they are mostly conditions, being developed on
the same branches. More must be known of the relations between
_Melanconium_ and Tulasne's sphæriaceous genus _Melanconis_ before
we can appreciate entirely the advantage to _Melanconium_ and some
other genera, that the wide diffusion of their spores should be
checked by involving them in mucus, or their being agglutinated to the
surface of the matrix, only to be softened and diffused by rain. The
spores in many species amongst the _Melanconiei_ are remarkably fine;
those of _Stegonosporium_ have the endochrome partite and cellular.
In _Stilbospora_ and _Coryneum_ the spores are multiseptate, large,
and mostly coloured. In _Asterosporium_ the spores are stellate,
whilst in _Pestalozzia_ they are septate, with a permanent peduncle,
and crested above with two or three hyaline appendages.
[Illustration: FIG. 49.--Spore of _Hendersonia polycystis_.]
[Illustration: FIG. 50.--Spores of _Dilophospora graminis_.]
[Illustration: FIG. 51.--Spores of _Discosia_.]
[Illustration: FIG. 52.--Spore of _Prosthemium betulinum_.]
[Illustration: FIG. 53.--Spore of _Stegonosporium cellulosum_.]
[Illustration: FIG. 54.--Stylospores of _Coryneum disciforme_.]
[Illustration: FIG. 55.--Spores of _Asterosporium Hoffmanni_.]
[Illustration: FIG. 56.--Spores of _Pestalozzia_.]
[Illustration: FIG. 57.--_Bispora monilioides_.]
The _Torulacei_ externally, and to the naked eye, are very similar to
the black moulds, and the mode of dissemination will be alike in both.
The spores are chiefly compound, at first resembling septate threads,
and at length breaking up into joints, each joint of which possesses
the function of a spore. In some instances the threads are connate,
side by side, as in _Torula hysterioides_, and in _Speira_, being
concentrically arranged in laminæ in the latter genus. The structure
in _Sporochisma_ is very peculiar, the joints breaking up within an
external tube or membrane. The spores in _Sporidesmium_ appear to
consist of irregular masses of cells, agglomerated into a kind of
compound spore. Most of the species become pulverulent, and the spores
are easily diffused through the air like an impalpable dust. They form
a sort of link between the stylospores of one section of the
_Coniomycetes_, and the pseudospores of the parasitical section.
PSEUDOSPORE is, perhaps, the most fitting name which can be applied to
the so-called spores of the parasitical _Coniomycetes_. Their peculiar
germination, and the production of reproductive bodies on the germ
tubes, prove their analogy to some extent with the prothallus of other
cryptogams, and necessitate the use of some term to distinguish them
from such spores as are reproductive without the intervention of a
promycelium. The differences between these pseudospores in the
several genera are confined in some instances to their septation, in
others to their mode of development. In the _Æcidiacei_ the
pseudospores are more or less globose, produced in chains within an
external cellular peridium. In the _Cæomacei_ they are simple,
sometimes produced in chains, and sometimes free, with or without a
caduceous peduncle. In the _Ustilaginei_ they are simple, dark
coloured, and occasionally attached in subglobose masses, as in
_Urocystis_ and _Thecaphora_, which, are more or less compact. In the
_Pucciniæi_ the distinctive features of the genera are based upon the
more or less complex nature of the pseudospores, which are bilocular
in _Puccinia_, trilocular in _Triphragmium_, multilocular in
_Phragmidium_, &c. In the curious genus _Podisoma_ the septate
pseudospores are involved in a gelatinous element. The diffusion of
these fruits is more or less complete according to their compact or
pulverulent nature. In some species of _Puccinia_ the sori are so
compact that they remain attached to the leaves long after they are
dead and fallen. In the genus _Melampsora_, the wedge-shaped
winter-pseudospores are not perfected until after the dead leaves have
for a long time remained and almost rotted on the ground. It is
probable that their ultimate diffusion is only accomplished by the
rotting and disintegration of the matrix. In the _Cæomacei_,
_Ustilaginei_, and _Æcidiacei_ the pseudospores are pulverulent, as in
some species of _Puccinia_, and are easily diffused by the motion of
the leaves in the wind, or the contact of passing bodies. Their
diffusion in the atmosphere seems to be much less than in the case of
the _Hyphomycetes_. By what means such a species as _Puccinia
malvacearum_, which has very compact sori, has become within so short
a period diffused over such a wide area, is a problem which in the
present state of our knowledge must remain unsolved. It may be through
minute and plentiful secondary spores.
[Illustration: FIG. 58.--Pseudospores of _Thecaphora hyalina_.]
[Illustration: FIG. 59.--Pseudospores of _Puccinia_.]
[Illustration: FIG. 60.--Pseudospores of _Triphragmium_.]
[Illustration: FIG. 61.--Pseudospores of _Phragmidium bulbosum_.]
[Illustration: FIG. 62.--_Melampsora salicina._ (Winter fruit.)]
SPERMATIA are very minute delicate bodies found associated with many
of the epiphyllous _Coniomycetes_, and it has been supposed are
produced in conjunction with some of the _Sphæriacei_, but their real
function is at present obscure, and the name is applied rather upon
conjecture than knowledge. It is by no means improbable that spermatia
do exist extensively amongst fungi, but we must wait in patience for
the history of their relationship.
TRICHOSPORES might be applied better, perhaps, than _conidia_ to the
spores which are produced on the threads of the _Hyphomycetes_. Some of
them are known to be the conidia of higher plants; but as this is by no
means the case with all, it would be assuming too much to give the
name of conidia to the whole. By whatever name they may be called, the
spores of the _Hyphomycetes_ are of quite a different type from any yet
mentioned, approximating, perhaps, most closely to the basidiospores
of the _Hymenomycetes_ in some, and _Gasteromycetes_ in others; as,
for instance, in the _Sepedoniei_ and the _Trichodermacei_. The
form of the spores and their size differ materially, as well as the
manner in which they are produced on the threads. In many they are
very minute and profuse, but larger and less plentiful in the
_Dematiei_ than in the _Mucedines_. The spores of some species of
_Helminthosporium_ are large and multiseptate, calling to mind the
spores of the _Melanconiei_. Others are very curious, being stellate in
_Triposporium_, circinate in _Helicoma_ and _Helicocoryne_, angular in
_Gonatosporium_, and ciliate in _Menispora ciliata_. Some are produced
singly and some in chains, and in some the threads are nearly
obsolete. In _Peronospora_, it has been demonstrated that certain
species produce minute zoospores from the so-called spores. The
dissemination of the minute spores of the _Mucedines_ through the
air is undoubted; rain also certainly assists not only in the
dispersion of the spores in this as in other groups, but also in the
production of zoospores which require moisture for that purpose. The
form of the threads, and the mode of attachment of the spores, is far
more variable amongst the _Mucedines_ than the form of the spores, but
the latter are in all instances so slightly attached to their supports
as to be dissevered by the least motion. This aids also in the
diffusion of the spores through the atmosphere.
[Illustration: FIG. 63.--Spores of _Helicocoryne_.]
SPORANGIA are produced in the _Physomycetes_ usually on the tips or
branches of delicate threads, and these when mature dehisce and set
free the minute sporidia. These are so small and uniform in their
character that they require but a passing mention. The method of
diffusion agrees much with that of the _Mucedines_, the walls of the
sporangia being usually so thin and delicate as to be easily ruptured.
Other modes of fructification prevail in some species by the
production of cysts, which are the result of conjugation of the
threads. These bodies are for the most part furnished with thicker and
more resistant walls, and the diffusion of their contents will be
regulated by other circumstances than those which influence the
dispersion of the minute sporidia from the terminal cysts. Probably
they are more perennial in their character, and are assimilated more
to the oogonia of _Cystopus_ and _Peronospora_, being rather of the
nature of resting spores, inasmuch as the same threads usually bear
the terminal fruits.
[Illustration: FIG. 64.--Sporidium of _Genea verrucosa_.]
[Illustration: FIG. 65.--Alveolate sporidium of _Tuber_.]
THECASPORES is a term which may be applied generally to all sporidia
produced in asci, but these are in turn so innumerable and variable
that it will be necessary to treat of some of the groups individually.
The _Thecaspores_, for instance, of the _Tuberacei_ offer several
features whereby they may be distinguished from other thecaspores. The
asci in which these sporidia are generated mostly partake of a broadly
saccate, ovate form. The number of sporidia contained in an individual
ascus is usually less than in the majority of the _Ascomycetes_, and
the sporidia approximate more nearly to the globose form. Usually,
also, they are comparatively large. Many have been figured by Corda[C]
and Tulasne.[D] Three types of spores may be said to prevail in the
_Tuberacei_: the smooth spored, the warted or spinulose, and the
areolate. The first of these may be represented by the _Stephensia
bombycina_, in which the globose sporidia are quite smooth and
colourless. The warted sporidia may be observed in _Genea verrucosa_,
the spinulose in _Tuber nitidum_, and the areolate are present in
_Tuber æstivum_ and _Tuber excavatum_, in which the epispore is
divided into polygonal alveoli, bounded by thin, membranaceous,
prominent partitions. This form of sporidium is very beautiful. In all
no special provision is made for the dissemination of the sporidia,
as, from their subterranean habit, none would be available save the
ultimate dissolution of the external integuments. As they are greedily
devoured by several animals, it is possible that they may be dispersed
through the excrements.
In the _Perisporiacei_ the perithecium has no proper orifice, or
ostiolum, for the discharge of the mature sporidia, which are usually
small, and are disseminated by the irregular rupture of the somewhat
fragile conceptacles. The asci are usually more or less saccate, and
the sporidia approximate to a globose form. The asci are often very
diffluent. In _Perisporium vulgare_ the ovate brown sporidia are at
first, and for some time, attached together in fours in a concatenate
or beaded manner. In some species of _Erysiphei_ the conceptacle
encloses but a single sporangium, in others several, which are
attached together at the base. In some species the sporangia contain
two, in others four, in others eight, and in others numerous sporidia.
In _Chætomium_ the asci are cylindrical, and in most cases the
coloured sporidia are lemon-shaped. When the conceptacles are fully
matured, it is commonly the case that the asci are absorbed and the
sporidia are free in the interior of the conceptacles.
[Illustration: FIG. 66.--Asci, sporidia, and paraphyses of _Ascobolus_
(Boudier).]
Of the fleshy _Discomycetes_ the genus _Peziza_ may be taken as
the type. If the structure which prevails in this genus be brought
to mind, it will be remembered that the hymenium lines an expanded
cup, and that the asci are packed together, side by side, with their
apices outwards, and their bases attached to a substratum of cells
which form the inner layer of the receptacle. The sporidia are
usually eight in each ascus, either arranged in single or double
rows, or irregularly grouped together. The asci are produced in
succession; the later, pressing themselves upwards between those
previously developed, cause the rupture of the mature asci at the
apex and the ejection of the sporidia with considerable force. When
a large _Peziza_ is observed for a time a whitish cloud will be seen
to rise suddenly from the surface of the disc, which is repeated again
and again whenever the specimen is moved. This cloud consists of
sporidia ejected simultaneously from several asci. Sometimes the
ejected sporidia lie like frost on the surface of the disc.
Theories have been devised to account for this sudden extrusion of the
sporidia, in _Ascobolus_, and a few species of _Peziza_, of the asci
also, the most feasible one being the successive growth of the
asci; contraction of the cup may also assist, as well as some other
less potent causes. It may be remarked here that the sporidia in
_Peziza_ and _Helotium_ are mostly colourless, whilst in _Ascobolus_
they pass through pink to violet, or dark brown, and the epispore,
which is of a waxy nature, becomes fissured in a more or less
reticulated manner.
[Illustration: FIG. 67.--Sporidium of _Ostreichnion Americanum_.]
The sporidia in _Hysterium_ proper are usually coloured, often
multiseptate, sometimes fenestrate, and occasionally of considerable
size. There is no evidence that the sporidia are ever excluded in the
same manner as in _Peziza_, the lips closing over the disc so much as
to prevent this. The diffusion of the sporidia probably depends on the
dissolution of the asci, and hence they will not be widely dispersed,
unless, perhaps, by the action of rain.
In _Tympanis_, asci of two kinds have been observed in some species;
one kind containing an indefinite number of very minute bodies
resembling spermatia, and the other octosporous, containing sporidia
of the usual type.
The _Sphæriacei_ include an almost infinite variety in the form and
character of the sporidia. Some of these are indefinite in the number
contained in an ascus, although the majority are eight, and a few
less. In the genera _Torrubia_ and _Hypocrea_ the structure differs
somewhat from other groups, inasmuch as in the former the long
thread-like sporidia break up into short joints, and in the latter the
ascus contains sixteen subglobose or subquadrate sporidia. Other
species contain linear sporidia, which are often the length of the
ascus, and may either be simple or septate. In _Sphæria ulnaspora_ the
sporidia are abruptly bent at the second joint. Shorter fusiform
sporidia are by no means uncommon, varying in the number of septa, and
in constriction at the joints in different species. Elliptic or ovate
sporidia are common, as are those of the peculiar form which may be
termed sausage-shaped. These are either hyaline or coloured of some
shade of brown. Coloured sporidia of this kind are common in _Xylaria_
and _Hypoxylon_, as well as in certain species of the section
_Superficiales_. Coloured sporidia are often large and beautiful: they
are mostly of an elongated, elliptical form, or fusiform. As
noteworthy may be mentioned the sporidia of _Melanconis lanciformis_,
those of _Valsa profusa_, and some species of _Massaria_, the latter
being at first invested with a hyaline coat. Some coloured sporidia
have hyaline appendages at each extremity, as in _Melanconis
Berkeleii_, and an allied species, _Melanconis bicornis_, from the
United States, also some dung _Sphæriæ_, as _S. fimiseda_, included
under the proposed genus _Sordaria_.[E] Hyaline sporidia occasionally
exhibit a delicate bristle-like appendage at each extremity, as in the
_Valsa thelebola_, or with two additional cilia at the central
constriction, as in _Valsa taleola_. A peculiar form of sporidium is
present in certain species of _Sphæria_ found on dung, for which the
generic name of _Sporormia_ has been proposed, in which the sporidium
(as in _Perisporium vulgare_) consists of four coloured ovate joints,
which ultimately separate. Multiseptate fenestrate sporidia are not
uncommon in _Cucurbitaria_ and _Pleospora_, as well as in _Valsa
fenestrata_ and some other species. In the North American _Sphæria
putaminum_ the sporidia are extraordinarily large.
[Illustration: FIG. 68.--Ascus and sporidia of _Hypocrea_.]
[Illustration: FIG. 69.--Sporidium of _Sphæria ulnaspora_.]
[Illustration: FIG. 70.--Sporidia of _Valsa profusa_ (Currey).]
[Illustration: FIG. 71.--Sporidia of _Massaria foedans_. × 400.]
[Illustration: FIG. 72.--Sporidium of _Melanconis bicornis_, Cooke.]
[Illustration: FIG. 73.--Caudate sporidia of _Sphæria fimiseda_.]
[Illustration: FIG. 74.--Sporidia of _Valsa thelebola_.]
[Illustration: FIG. 75.--Sporidia of _Valsa taleola_. × 400.]
[Illustration: FIG. 76.--Sporidium of _Sporormia intermedia_.]
[Illustration: FIG. 77.--Asci and sporidia of _Sphæria_ (_Pleospora_)
_herbarum_.]
[Illustration: FIG. 78.--Sporidium of _Sphæria putaminum_. × 400.]
The dissemination of the sporidia may, from identity of structure in
the perithecium, be deemed to follow a like method in all. When
mature, they are in a great measure expelled from the mouth of the
perithecia, as is evident in species with large dark sporidia, such as
exist in the genera _Hypoxylon_, _Melanconis_, and _Massaria_. In
these genera the sporidia, on maturity, may be observed blackening the
matrix round the mouths of the perithecia. As moisture has an evident
effect in producing an expulsion of sporidia by swelling the
gelatinous nucleus, it may be assumed that this is one of the causes
of expulsion, and therefore of aids to dissemination. When _Sphæriæ_
are submitted to extra moisture, either by placing the twig which
bears them on damp sand, or dipping one end in a vessel of water, the
sporidia will exude and form a gelatinous bead at the orifice. There
may be other methods, and possibly the successive production of new
asci may also be one, and the increase in bulk by growth of the
sporidia another; but of this the evidence is scanty.
Finally, OOGONIA may be mentioned as occurring in such genera as
_Peronospora_ amongst moulds, _Cystopus_ amongst Uredines, and the
_Saprolegniaceæ_ amongst the _Physomycetes_. The zoospores being
furnished with vibratile cilia, are for some time active, and need
only water in which to disseminate themselves, and this is furnished
by rain.
We have briefly indicated the characteristics of some of the more
important types of spores to be found in fungi, and some of the
modes by which it is known, or presumed, that their dissemination
takes place. In this summary we have been compelled to rest content
with suggestions, since an exhaustive essay would have occupied
considerable space. The variability in the fruit of fungi, in so far
as we have failed to demonstrate, will be found exhibited in the
illustrated works devoted more especially to the minute species.[F]
[A] Cunningham, in "Ninth Annual Report of the Sanitary Commissioner
with the Government of India." Calcutta, 1872.
[B] See "Corda Icones," tab. 2.
[C] Corda, "Icones Fungorum," vol. vi. Prague.
[D] Tulasne, "Fungi Hypogæi." Paris.
[E] Winter, "Die Deutschen Sordarien" (1873).
[F] Corda, "Icones Fungorum," 6 vols. (1837-1842); Sturm,
"Deutschlands Flora," Pilze (1841); Tulasne, "Selecta Fungorum
Carpologia;" Bischoff, "Kryptogamenkunde" (1860); Corda,
"Anleitung zum Studium der Mykologie" (1842); Fresenius,
"Beiträge zur Mykologie" (1850); Nees Ton Esenbeck, "Das System
der Pilze" (1816); Bonorden, "Handbuch der Allgemeinen
Mykologie" (1851).
VII.
GERMINATION AND GROWTH.
In describing the structure of these organisms in a previous
chapter, the modes of germination and growth from the spores have
been purposely excluded and reserved for the present. It may be
assumed that the reader, having followed us to this point, is
prepared for our observations by some knowledge of the chief features
of structure in the principal groups, and of the main distinctions
in the classification, or at least sufficient to obviate any
repetition here. In very many species it is by no means difficult to
induce germination of the spores, whilst in others success is by no
means certain.
M. de Seynes made the _Hymenomycetes_ an especial object of study,[A]
but he can give us no information on the germination and growth of the
spore. Hitherto almost nothing is positively known. As to the form of
the spore, it is always at first spherical, which it retains for a
long time, while attached to the basidia, and in some species, but
rarely, this form is final, as in _Ag. terreus_, &c. The most usual
form is either ovoid or regularly elliptic. All the _Coprini_ have the
spores oval, ovoid, more or less elongated or attenuated from the
hilum, which is more translucent than the rest of the spore. This last
form is rather general amongst the Leucospores, in _Amanita_,
_Lepiota_, &c. At other times the spores are fusiform, with regularly
attenuated extremities, as in _Ag. ermineus_, Fr., or with obtuse
extremities, as in _Ag. rutilans_, Sch. In _Hygrophorus_ they are
rather irregular, reniform, or compressed in the centre all round.
Hoffmann[B] has given a figure taken from _Ag. chlorophanus_, and
Seynes verified it upon _Ag. ceraceus_, Sow. (See figures on page
121.)
The exospore is sometimes roughened, with more or less projecting
warts, as may be seen in _Russula_, which much resembles _Lactarius_
in this as in some other particulars. The spores of the _Dermini_ and
the _Hyporhodii_ often differ much from the sphærical form. In _Ag.
pluteus_, Fr., and _Ag. phaiocephalus_, Bull, there is already a
commencement of the polygonal form, but the angles are much rounded.
It is in _Ag. sericeus_, _Ag. rubellus_, &c., that the polygonal form
becomes most distinct. In _Dermini_ the angles are more or less
pronounced, and become rather acute in _Ag. murinus_, Sow., and _Ag.
ramosus_, Bull. The passage from one to the other may be seen in the
stellate form of the conidia of _Nyctalis_.