FUNGI.
THE Fungi are enormously numerous. No less than 2,000 of the highest and
most conspicuous of these plants have been figured; many more have been
described; multitudes of those inhabiting the torrid zone are unknown;
and the microscopic and parasitic tribes are innumerable. Though with a
few exceptions entirely formed of cellular tissue, the fungi resemble
animals in respiration and chemical constitution. They contain more
azote than any other of the Cryptogamia, and obtain it chiefly from
their food, which consists of animal and vegetable substances alive,
dead, or decomposed. They inhale oxygen, and exhale carbonic acid gas,
so that they never form true chlorophyll. No plants are more dependent
on heat and moisture; many perform all the functions of life and
reproduction independently of light, preferring dark and shady places to
sunshine.
The Fungi form two principal groups, distinguished by their mode of
fructification. In the higher group, _Sporiferi_, the fungus produces
naked spores either single or compound, by means of which it may be
multiplied. In the lower group, _Sporidiiferi_, the fructification
consists of sporidia, enclosed in a distinct sac. The Sporiferi include
the following orders, Hymenomycetes, Gasteromycetes, Coniomycetes, and
Hyphomycetes. The Sporidiiferi include the Ascomycetes and the
Physomycetes. These various groups we may now proceed to examine.
The most important family of Fungi is, without question, that of the
HYMENOMYCETES, the species of which far excel all others in their
richness of colouring, and beauty of form. In this group the hymenium is
free and mostly exposed. It comprises six orders, of which the Agaricini
hold the first place. The genus Agaricus alone comprises 1,000 distinct
species, which assume as many different forms and colours, with only
slight modifications of substance, and it surpasses in number of species
all the other generic groups known.
The Agaricus campestris, or common mushroom, is a type of that vast
group; it consists of two distinct parts, the nutritive and
reproductive. The nutritive part is the mycelium or mushroom spawn of
gardeners, which resembles a mass of white spider’s threads mixed in
inextricable confusion, and carries on for a time all the functions of
the plant. Mycelia may exist for years without bearing the reproductive
part, but fruit never can be produced without spawn. The mushroom
itself, which springs from the spawn, is the fruit-bearing part, in
which the spores are formed and ripened. It is distinguished by a kind
of hat or bonnet called the pileus, supported by a stem. The pileus is
lined by a number of gill-shaped plates or lamellæ radiating from a
common centre; they are the reproductive organs in which the spores are
produced by free cell formation, a process always preceded by a
concentration of the matter within the parent cell, which is then
divided into as many nuclei as there are to be spores. In the higher
fungi, the number of spores thus formed is definite; in the Agarics they
are in groups of four placed at the extremity of a stem, springing from
the summits of these reproductive gills. Most of the Agarics rise from
the ground without any cover; the pileus or cap may show every variety
from a smooth polished surface to hairs or shaggy scales, but some of
the more highly organized have a general wrapper or volva, which
encloses the whole plant, and bursting at last, it leaves some traces
behind. In others, the pileus is at first clothed with fibres, which
vanish or leave traces on its margin forming a veil or curtain. Some
have a membrane attached to the stem, either connected with the volva,
or spread under the gills when young, and, when more or less persistent,
it is called a ring.
The spawn, which is the earliest product of the spore, has a great
variety of forms. Sometimes it is filamentous, sometimes tubular,
creeping extensively, or concentrated in a felted mass, sparingly
developed, or produced in abundance. Besides, it is developed in a great
variety of situations often difficult to detect. The fructification is
alone evident, under innumerable forms, which are as rapid in their
growth as they are for the most part ephemeral in their duration. Some
species have been known to acquire several square inches of surface in a
single night; the plant, however, is often far advanced before it
appears above ground. Some Agarics grow most readily after thunder
storms and abundant rains; certain species are always single; others
grow in dense aggregations; while in several species there is a tendency
to assume a circular arrangement, and that not merely when the spawn is
perennial, but when the whole existence of the fungus is confined to a
few days or weeks.
A mass of spawn is not always produced by a single spore, but by a
collection of spores, from whence it spreads in every direction, and
forms a common belt. In the Agaricus arvensis, Marasmius Oreades, &c.,
it spreads in a circle and bears fruit; and, as it continues to spread,
the same process takes place at each circumference. In this way are
formed the Fairy Rings so frequently seen in pasture lands. The fairy
rings are sometimes of very ancient date, and attain enormous
dimensions, so as to be distinctly visible on the side of a hill from a
considerable distance. It is believed that they originate from a single
fungus, whose growth renders the soil immediately beneath unfit for its
reproduction. The spawn, however, spreads all around, and in the second
year produces a crop, whose spawn spreads outwards again, for the soil
behind forbids its return in the opposite direction. Thus the circle is
continually increased, and extends indefinitely till some foreign cause
destroys it. The manure arising from the dead fungi of the former years
makes the grass vigorous around, so as to render the circle visible even
when there is no external appearance of the fungus; and the contrast is
often the stronger from that immediately behind it being killed by the
old spawn. This mode of growth is far more common than it is supposed to
be.
The depth to which spawn penetrates and the rapidity of its growth even
in the hardest timber if exposed to damp is quite astonishing. Instances
occur in which the spawn of dry rot not only enters wood, but penetrates
solid structures of brick. It overcomes an immense resistance.
The genera of the Agaricini differ in substance; some are almost
ligneous, others leathery or tough, occasionally they are delicate and
deliquescent, and although most of them are entirely formed of cellular
tissue, the Lactarii and Russulæ form remarkable exceptions in having
laticiferous vessels mixed with their cellular structure. These vessels
exist in all parts of the plants, especially in the gills, where they
give out the liquid on the slightest touch. In the Russulæ it is watery;
but in the Lactarii, in which it is either mild or acrid, according to
the species, it is also of different colours, which sometimes change
their tint upon exposure to the air, probably from ozone. In all fungi
there is a small amount of poisonous matter, and the quantity in any
given species is extremely uncertain, so that the same fungus which may
be eaten with safety in one country, is deleterious in another.
In the dark coal mines at Dresden, luminous Fungi cover the roof and
pillars with the most dazzling phosphorescent light, which increases
with the temperature of the mine. Agaricus Gardneri, a species parasitic
on the Pintado palm in Brazil, is highly luminous; and the Agaricus
olearius in the south of France also possesses that rare quality. The
gills under the pileus shine as brightly as a glow-worm, in the dark
crevices of the olive stems in November and December. M. Tulasne found
that the light was extinguished in vacuo or non-respirable gases, whence
he concludes that it is due to a slow combustion without heat, arising
from a chemical combination of the oxygen of the atmosphere, inhaled by
the fungus, with a substance peculiar to the plant.
In a few Agarics the cells are so connected by veins or lateral
branches, that they assume the character of pores, as in the
Chantarelle, a sweet-scented lemon-coloured fungus, whose gills pass
into mere veins, and its inferior fruit-bearing surface is all but even
and uniform, so that it forms a connection between the Agarics and the
Polyporei, a most extensive order of the higher fungi, essentially
distinguished by having a multitude of pores in the smooth under-surface
of the pileus, instead of gills. The pores are generally small; in some
species they are hexagonal, and so large that they look like a
honeycomb. In all, they are the mouths of cellular tubes, packed closely
together side by side, or more closely connected, sometimes easily
separated, sometimes inseparable. They constitute the fructiferous
surface or hymenium of the fungus, and contain the spores. This
structure gives the pileus a thick heavy appearance, and a vast variety
of characters; besides, the substance itself varies in density and
colour. The stem also may be long or short, sometimes wanting
altogether, when the pileus or cap is attached to the surface on which
the fungus is growing. The growth of individual fungi, whether Polyporei
or Agarics, is centrifugal, that is, they spread from the centre of the
pileus, as in the Polyporus fraxineus, which involves every stick and
blade of grass it meets with as it increases in diameter, and continues
to increase for years, till it is occasionally a yard across.
The fructiferous surface in the higher fungi is essentially turned away
from the light, yet, although in many of the lower Agarics it is
uppermost and exposed, such is the tendency to produce the
fructification on the lower side, especially in the Polyporei, that if
the position of the plant be reversed the hymenium or fructiferous
surface is gradually obliterated and a new one is formed on the other
side.
The Polyporei abound in the tropical forests, but species are found in
all latitudes. The higher fungi are more or less plentiful in forests
everywhere, and every genus of trees seems to have one or more species
of fungus peculiar to itself. The Boleti, a genus of the Polyporei,
which are thick fleshy fungi of various forms, and for the most part
brilliantly coloured, grow under trees in the temperate zones, sometimes
in conspicuous circles. When a slice of the Boletus luridus, cyanescens,
or other species is exposed to the air, the white fleshy part acquires a
blue tint in consequence of the action of ozone upon the acetate of
aniline, which was ascertained by Dr. Phipson to be a constituent of
these fungi. According to M. Dutrochet more heat is evolved by the
Boletus æneus than by any other vegetable except the Arum.
The Polyporei destroy decaying trees and timber, and the Merulius
lacrymans or common house fungus, attacks and induces the decay of
timber previously sound. The cap is large, fleshy, spongy and moist, but
delicate and velvety on the under-side, with wide porous dentate folds.
The plant is yellow with a white woolly margin. It grows in a circle,
and its mycelium attracts moisture from the atmosphere, which falls down
in drops from the pileus. The decay of wood induced by the attacks of
this mischievous fungus, is what is called dry rot.
The four principal sub-orders of the Hymenomycetes, or highest fungi,
have a cap or pileus, and an inferior fructiferous surface characterized
by gills, pores, or tubercles, and are connected by intermediate
species; but the other two sub-orders are quite different. The Clavariei
are club-shaped, upright, branching fungi, with the fructification
surrounding the uppermost extremity of some of the stems. The finest
species grow in the Swiss forests where they form an article of food;
some are edible in Britain, but of smaller size.
The Tremellini consists of plants forming a gelatinous mass of a bright
orange, purple, or dark brown colour, which may be seen on rotten sticks
in hedges, and in enormous masses resembling the convolutions of an
animal’s brain on the stumps of dead trees, or at the base of living
ones. They are mostly plants of temperate climates, but the Exidia
Auricula Judæ, or Jew’s ear, is universal. All fungi have a mycelium,
but in this order it is not apparent. The structure of the fruit, as
determined by the microscopic observations of Mr. Berkeley and of M.
Tulasne, is unusual. The fructiferous part is very extensive, being
uppermost and spread over the surface of the gelatinous mass, so as to
follow all its inequalities. Threads rise from this fructiferous surface
bearing on their extremities globular cells exhibiting a concentration
of coloured matter generally divided into four lobes, and from the upper
surface of these globular bodies, a number of flexuous threads spring,
carrying on their tips cymbiform spores.[52]
In the preceding family (Hymenomycetes) the fruit-bearing surface has
free access to the air, but in the group of the GASTEROMYCETES, which
consists of five or six sub-orders, it has neither access to air or
light till the fruit is ripe, for the fructification is enclosed in a
rind of one or two coats, and springs without a stem from a gelatinous
thready, or cellular mycelium. The most important group, Trichogastres,
includes the puff-balls, which grow on the ground. Of these the
Lycoperdon, found everywhere on pasture grounds and meadows, is a
familiar instance. When young it has a milk-white coat filled with
closely packed cells, some of which bear naked spores set upon spicules.
When mature, the whole of the interior vanishes, leaving nothing but a
mass of threads and fruit; the coat becomes brown, bursts open at the
top, and gives vent to a cloud of microscopic spores like the finest
dust. In general the ball is sessile, or it has merely the rudiment of a
stem. The Lycoperdon giganteum, an exceedingly large species, is a
native of a warm climate. The tops of some of the branched threads of
its hymenium swell into pear-shaped cells surmounted by short spicules
ending in spores; when young it is edible, when dry it is used for
tinder and as a styptic, and when ignited its fumes possess a property
similar to that of chloroform. The Batarrea forms a contrast to the
common puff-balls, being mounted on a stem sometimes a foot and a half
high. It has several coats enclosing a thick gelatinous substance in
which the threads carrying the spores are distinctly spiral and closely
twisted.
The sub-order Hypogæi is subterranean, as the name implies. The exterior
coat of these fungi is inseparable from the internal matter, which is
for the most part fleshy. In some species it is dry, in others it
abounds in milky juice; but in all the fruit is formed in hollows
excavated in the interior mass. In some species these cavities are
traversed by threads, and in many species the spores accumulate in such
multitudes within the cavities, as to make it certain that the spicules,
on which the spores are borne, produce successive crops. They are set
free by the rupture of the rind. A species of the genus Melanogaster,
abundant in the south of England, is edible and sold as the red truffle
of Bath; but it is far inferior to the real truffle.
The order Phalloidei has a club-shaped or globose head, composed in the
interior of large cells mixed with fruit-bearing cavities. This head has
a coat consisting of a jelly inclosed between two heterogeneous strata.
The whole interior of the fungus deliquesces, changes to a mucilage, and
drips out of the exterior coat in drops dark with microscopic spores.
The colour of these fungi is often beautiful, but their smell is most
loathsome, tainting the air to a considerable distance; yet the
gelatinous volva of more than one species—an Ileodictyon—is eaten by the
New Zealanders under the name of thunder dirt, and Phallus Mokusin is an
article of food in China.
Certain species of these fungi have a rudimentary stem in their early
stages, but it becomes full of deep pits or cavities and suddenly
acquires an enormous development when the plant approaches maturity. The
cavities are at first strongly compressed, but as the stem increases,
they acquire a rounder form, till at length their vertical tendency is
so strong that the coat or volva of the fungus is ruptured, which could
only be effected by a very strong force. Moreover, the stem is fixed to
the base by so small a point that the plant could not remain erect were
it not for the tubes of the volva which contract on the stem and act as
a sustaining force. Thus these very revolting fragile plants afford a
very striking instance of mechanical power exerted by vegetable matter.
The Myxogastres are an anomalous group of fungi which often appear as
black or coloured spots on dead leaves and twigs. Sometimes their
mycelium or spawn is large and conspicuous, as that of the Reticularia
maxima, which overruns cucumber beds, choking up the breathing pores,
and killing the plants. Species of these fungi are found upon mineral
and vegetable substances dead and alive, and the same species grows upon
plants of very different affinities, so that they depend upon the
atmosphere for their nourishment, and not on their matrix. Like the
puff-balls they end their lives in myriads of microscopic dust spores,
but they begin it as a gelatinous mass, sometimes sparkling as a gem,
brilliant with the metallic tints of gold, silver, steel, or copper.
The gelatinous or creamy mucilage of which these fungi consist, forms a
mycelium which is either diffuse, or creeps over the matrix on which it
grows in anastomosing filaments like a network, or it is arranged
without any definite order. This spawn gives rise to many bodies having
an envelope of one or more concentric membranes, technically called a
peridium, enclosing a gelatinous fertile substance which, when mature,
becomes a mass of scales or threads mixed with spores; the spores are
mostly attached to short threads singly or in groups, sometimes
surrounded by a firm coat or cyst. These bodies are either sessile on
the mycelium or stalked, and are either free or confluent. In their soft
state the tissues are so delicate that they exhibit no structure, but
just as they are passing from the puffy to the dry dusty state there are
indications of it.
It would be tedious to describe the variety of forms assumed by the
fruit-bearing bodies in the different genera of these fungi, or the
manner in which they are ruptured to give egress to the spores, which
differ in colour according to the species, though they are for the most
part red. The forms of the chaffy scales and threads are equally
diversified: in the species of Trichia, the threads contain one or more
spiral filaments, a form peculiar to the vegetable kingdom.
Botanists are now generally of opinion that the Myxogastres are
vegetables, although the singular Amœba-like motions some of them
exhibit, and the nature of the motile bodies they produce, seemed to
assign them a place in the animal kingdom; indeed, even now little is
known of the reproduction and final life-history of these singular
fungi.
Motions precisely similar to those of the Amœbæ, the lowest class of
animal existences, were observed by MM. Hoffmann and Tulasne, and more
especially by M. de Bary,[53] in the Æthalium septicum. It is a yellow
pulpy mass, produced upon a spawn or mycelium consisting of semi-fluid
gelatinous anastomosing filaments, often widely spread through the moist
tan in hothouses.
M. de Bary describes the filaments of the mycelium as full of a
multitude of small colourless corpuscles mixed with large yellow ones;
moreover the branches of this mucous network are described as
continually changing their form, in a manner closely resembling the
pseudopodia of the animal Amœba. They push out new branches, others are
withdrawn, and the whole mycelium frequently advances with a creeping
motion of translation. The yellow pulpy mass produced by the mycelium is
entirely composed of similarly constituted soft filaments about the
thickness of a bristle closely interlaced. They anastomose in all
directions, in long or short meshes, and their upper free extremities
form groups of projections which bristle the exterior surface of the
pulpy mass.
When that mass is about to form spores, all the asperities on its
surface are withdrawn and replaced by a bright yellow network of
irregularly interlaced filaments, which constitutes an envelope to the
interior spore-forming part, consisting of a white central liquid or
plasma containing an innumerable multitude of colourless granules. Both
of these parts are formed at the expense of the filaments which are
decomposed, the yellow granules are absorbed in the envelope, while the
colourless granules retire with the gelatinous matter towards the centre
to constitute the plasma, which is the fruit-producing part. Transparent
globular cells containing nuclei are generated simultaneously in every
point of the plasma, round each of which a portion of the granular
matter is consolidated; it takes a dark purple colour and constitutes a
spore, myriads of which, fine as dust, are thus generated. The whole of
the plasma is consumed in the spores, except a very small quantity,
which forms the threads found mixed with the spore dust. According to M.
de Bary the complete development of the Æthalium, from the instant it
appears above the tan in a hothouse of high temperature to the maturity
of the spores, is accomplished in about fifteen hours. The rapidity of
growth of this fungus is therefore astonishing. Mr. Berkeley mentions
that a mass of it two feet long, formed of many confluent individuals,
was formed upon a piece of iron that had been red-hot twelve hours
before—a proof among many others of the meteoric nature of these fungi,
the atmosphere affording them a sufficient supply of food.
The motions of the plastic matter contained within the dust-like spores
of the Æthalium septicum exhibit amœban motions of the same character as
its mycelium. For when M. de Bary placed ripe spores of that fungus in
water, their skin burst open and the plastic granular matter was set
free under the form of a coherent globular mass without any exterior
membrane. These globular corpuscles exhibited amœba-like changes of
form; processes were pushed out, and then drawn in, till at last they
assumed an elongated cylindrical shape round at one end, prolonged at
the anterior end into a long cilium with which they turned convulsively
round their axis. At the same time vacuoles were frequently seen to
expand and contract alternately in the round extremity. Ultimately these
bodies lost their middle, and at last were divided into two equal parts,
each of which went through the same changes as the primary globule, and
at length assumed the ciliated active form. Besides these active bodies,
there were others which never acquired cilia. The motile bodies were
also discovered in other species of these fungi by M. Hoffmann; there
can be no doubt that they are either zoospores, or of the same nature as
the eel-shaped motile bodies in some of the Algæ; possibly the bodies
which never acquire cilia may be germ cells. There is still much
obscurity with regard to the Myxogastres, inasmuch as the origin of
their mycelium is unknown, whilst in all other fungi mycelium or spawn
are produced by the germination of the spores. The spiral vessels found
in the threads of the Trichia prove that the members of this singular
family are truly vegetables. Professor Fries places the geographical
maximum or centre in the temperate zone, but different species are found
from New Zealand to high northern latitudes.
The Nidulariacei constitute a beautiful order of this family of fungi.
The plants are exactly like a bird’s nest with eggs, sometimes with a
stem, sometimes without. At first the nest or cup has a cover consisting
of several coats, which either burst open with a stellate or irregular
figure, or by the separation of a little lid; then the hollow of the cup
or nest is exposed, and at the bottom are seen one or more sporangia,
that is spore cases, often immersed in jelly and either free or fixed to
the nest by an elastic string. The spore-coats at first contain a
compact circular mass, but a cavity is afterwards formed in the centre,
and the cells which terminate in the walls of the cavity bear spores on
their tips. When ripe the spore cases are ejected by elastic power. The
force with which the sporangium of the species of Sphærobolus is
ejected, far exceeds _in proportion_ the force with which a shell is
projected from a large mortar; this fungus sometimes grows in damp
hothouses.[54] Many Nidulariæ are widely spread, but they thrive best in
warm climates.
The intimate structure and fructification of the higher fungi are for
the most part microscopic but an innumerable mass of the lower fungi are
themselves invisible to the naked eye, living upon all kinds of
vegetable and animal substances, dead, alive, fresh or putrid. They
vegetate upon decayed linen, flannel, leather, and even on metallic and
poisonous solutions. They yield myriads of minute spores wafted by every
breeze. They float in the air we breathe, seeking a nidus in anything
that will supply them with suitable food. There is scarcely a spot on
the earth where these minute spores may not exist, and being insoluble,
they wait where they fall for the growth or decay of the plant or animal
which suits them. As parasites they are most destructive, producing
disintegration, disease, and even death, both in vegetables and animals.
It is the mycelium or spawn which does the mischief, by supplying the
fungus with food at the expense of the victim. The spores of the
Botrytis Bassiana find a nidus in the breathing pores which open into
the trachea of the silkworm; they develop their mycelium in the
air-tubes, which are soon filled up; it then extends into the fatty
matter under the skin, which nourishes the worm during its dormant
state, and, as soon as that matter is exhausted, the victim dies.
In autumn, the common fly, though quite dead, may be seen adhering to
many parts of a room, especially to the window glass, as if it were
alive. In this state it is always surrounded by a halo about an inch in
diameter of whitish dust, consisting of the spores of the Empusa Muscæ,
or fly fungus. The body of the fly is much distended, the rings of its
abdomen are separated by the growth of the mycelium from within, and all
the contents of the body having been consumed by the parasite, nothing
remains but a hollow shell with a thin felt-like layer of the interlaced
mycelia of innumerable fungi, for the fly fungus increases with
wonderful rapidity within the insect. Mr. Berkeley believes the fly
fungus to be merely a condition or phase of one of those anomalous
moulds which grow on dead fish, making them conspicuous as they float on
the surface of the water, by the foggy halo which surrounds them.
Different kinds of parasitic fungi may exist at the same time. Dr. Leidy
found a variety in the stomach of the Passalus cornutus, a beetle that
lives upon decayed wood. Fungi do not attack the carnivorous beetles.
Man is not exempt from these parasites. Fourteen different species of
fungi were discovered by Mr. Hogg in as many cutaneous diseases. There
cannot be the smallest doubt of cutaneous disease being induced by
inoculation with fungi; merely rubbing certain species on the skin is
sufficient. Fungi cause baldness by fixing themselves on the roots of
the hair, and destroying the internal structure of the bulb. Our eyes
are not exempt from attacks of these parasites, for in performing an
operation upon a diseased eye Dr. Hannover found several species of
fungi in it; one of them was globular, and strongly refracted the light.
There is a fungus consisting of from four to sixty-four cells united in
square groups, which infests the stomachs of men and animals, even in a
healthy state; but although fungi produce certain cutaneous diseases,
there is no proof as yet that fever, cholera, or any other epidemic, is
owing to the spores of the fungi which we inhale from the atmosphere.
The family of CONIOMYCETES consists of six groups, two of which are
parasites on living vegetables, the other four growing on those which
are dead, decaying, or dying. They are microscopic plants, and their
mycelium is filamentous, or vesicular, often obsolete; short threads
rising from it bear on their tips either septate spores, or spores like
fine dust, inclosed in oval or bottle-shaped cases, called perithecia,
or in cells united in a cell, like a necklace of beads. We are chiefly
indebted to M. Tulasne and his brother for the obscure and extraordinary
life-history of these fungi.
The parasites on living plants form the two vast groups of Epiphytes and
Entophytes. The Epiphytes exhibit their fructification on the surface of
the plant, while their mycelium penetrates the moist texture of its
interior, which feeds them. All parts are liable to be attacked by these
fungi; they may insinuate their mycelium into the leaves, stem, flowers,
stamens, anthers, and the very heart of the seeds. The mycelium is
generally annual, but sometimes it is perennial, and leaves a crop of
fungi year after year; it disintegrates the tissues of the plant on
which it feeds, and distorts or kills it. Occasionally, the chlorophyll
in the leaves is oxidized, and becomes yellow by the oxygen which the
parasite absorbs.
The Entophytes, which constitute the second group of parasites on living
plants, form microscopic congregations in the interior of the leaves and
tender shoots, the only indication of their existence being a white,
red, or orange coloured spot, which usually becomes black or brown when
the fungus attains maturity. It appears that the same individual of
these entophytes may assume two or more different forms during the
course of its life, and bear two or more totally dissimilar types of
fructification. Of these, the sub-orders Pucciniæ and Uredines furnish
many examples.
[Illustration: Fig. 32. Pucciniæi:—_a_, Aregma speciosum; _b_,
Xenodochus paradoxus; _c_, Puccinia Amorphæ; _d_, Triphragmium dubens;
_e_, Young spores of an unknown Puccinia; _f_, Puccinia lateripes.]
Fig. 32 represents various species of Pucciniæi, which consist of a
thread ending in club-shaped or elongated cells called asci, containing
a definite or indefinite number of septate conidia or spore dust cells.
Each order of plants, as the Rosaceæ, has its own form of these
entophytes. In the tissue of a rose leaf, immediately beneath a bright
golden coloured surface spot, M. Tulasne found two distinct forms of
fungi, living together in a small cavity. The forms were exactly those
of a Puccinia and Uredo. The Puccinia consisted of a short colourless
stem, ending in a club-shaped cell, containing two conidia or spore
cells. These fungi were crowded together in multitudes in a small space
so as to form a solid rounded mass, with their broad tops immediately
under the skin of the upper-side of the leaf, but sometimes they were
arranged in concentric circles. The Uredines, on the contrary, had
colourless branching stems, like threads, bearing on their tops pointed
spore sacs. In some species these Uredines are scattered through the
mass of Puccinia, in others disposed in a circle round it, or in the
centre of the concentric ring where the Puccinia takes that form. It was
long believed that these two forms of fungi living together in the same
cavity were totally different plants, but as in various instances M.
Tulasne perceived that the Uredo had sprung up, shed its spores, and
vanished before its companion had ripened its fruit, he concluded that
the two different forms are merely two states of the same plant, that
the larger spores of the Uredo thus early matured, immediately germinate
and produce the Puccinia, whose fine dust-like spores are merely the
secondary fruit of the Uredo. These minute spores issue through a pore
in the conidia or dust cell and a puncture in the upper skin of the leaf
into the air, whence they are wafted in myriads by the winds; and, if
not too late in the season, they enter into the pores of the leaves and
tender parts of the same or other plants that may suit them, and within
these they form a mycelium, and produce a young Uredo. Even if the
autumnal leaves fall in a moist place before the spores have germinated,
the entophyte will grow on the approach of spring, and ultimately send
its dust spores to enter into young leaves, and grow with their growth.
Although there cannot be a doubt of the existence of the Uredines as a
numerous natural family, M. Tulasne considers the species of certain
genera to be only secondary forms of certain genera of Pucciniæ. Many of
these minute fungi have a third and even a fourth order of fruit; the
principle being carried to a maximum in the order Cæomacei. These
entophytes have a delicate mycelium, which gives rise to short or
obsolete fertile threads, terminated by single spores or chains of
spores. These spores when they germinate produce a second order of
spores; these occasionally produce a third order, and so on successively
even to a fourth or a fifth order. It is always the last and smallest
spores which reproduce the plant. The object of the successive orders
seems to be to diminish the size of the spores and to increase their
number, that they may more easily enter the stomates of the plants they
live upon, and be more easily and widely dispersed by the winds.
The Uredo candida, or Cystopus candidus, which takes its name from the
white spot it forms on the leaves of the cabbage and other vegetables,
is found to produce both female or germ cells and spermatozoids. Long
before the white spot is formed on the leaf, the presence of the
abundant spawn may be perceived by swellings and deformities in the
victim plant. Its filaments, which creep exclusively in the
intercellular canals of the cellular tissue, are tubular, of unequal
diameter, and exceedingly branched, and are always formed of cellulose,
either thick-walled and gelatinous, or thin-walled and membranous. From
this mycelium, little threads hang down, ending in globular vesicles
containing a nearly homogeneous colourless matter, and ultimately an
aqueous liquid; they are supposed to fix the mycelium to the cells of
the victim. According to the examination of Mr. Berkeley, M. Tulasne,
and others, the branches of the mycelium accumulate in a hollow
immediately under the white spot in the skin of the leaf of the plant
attacked. From these branches spring bundles of club-shaped tubes,
directed perpendicularly towards the upper skin of the leaf, and forming
a tuft or little cushion of variable extent. The summit of each of these
club-shaped tubes is formed into a conidium, or spore dust cell, which
separates itself from that below it by taking a globular form. In the
upper end of the remainder of the tubes, new spore dust cells are
formed, and so on indefinitely. These conidia remain attached to one
another in a string by slender constrictions which become thinner, and
at last give way from above downwards, and they escape in succession
through a crack in the skin of the leaf. The quantity of spores that are
generated by the dense mass of these club-shaped tubes must be enormous.
The Cystopus has female reproductive cells, which had escaped notice
from being hid in the plastic matter which nourishes them. They appear
before the spore dust bearing cells, and are formed by terminal or
interstitial swellings in the tubes of the mycelium, which become large
oval cells, separated ultimately by a closure from the rest of the tube
that bears them; they are filled with a granular liquid mixed with large
granules of a coloured fatty matter. The tips of some branches of the
mycelium swell into oval or club-shaped cells containing spermatozoids,
which fertilize the female cells; then the matter within the latter
assumes a globular form, gets a coat of cellulose, and becomes the true
fruit of the Cystopus.
As early as the year 1807, M. B. Prévost had seen that the sporangia, or
spore cells of the entophytes produced zoospores, and recently M. de
Bary has seen them produced, during the germination of the spores,
collected within a sporangium of the Cystopus. When they came into the
water they had two cilia, one of which was short and went first, the
other was long and trailed after the zoospore. Neither M. de Bary nor M.
Tulasne have ever seen zoospores in the fungus itself, but if the drops
of rain or dew round the white spot on the leaf of a plant be examined,
empty sporangia are generally found, and spores in different states of
development.
The Puccinia Fabæ, an entophyte on the common bean, has but one spore in
its cylindrical case, and is considered identical with the Uromyces
appendiculatus. Besides male organs like those of the Æcidium, M. de
Bary found that the bean entophyte has four kinds of reproductive
organs, of which one alone reproduces the original form, while the
others present a well-marked alternation of generations. The Puccinia
forms a prothallus on which conidia, or secondary spore dust cells,
arise; these secondary spores form a mycelium, on which an Æcidium
appears, whose orange-coloured fruit gives rise to a Uredo, and the dust
spores of the Uredo enter the leaves of beans or peas, and grow into a
Puccinia. All the species of Æcidium are similar to one another, and M.
Tulasne is of opinion that they do not constitute a distinct genus, but
that, like many of the Uredines, they are merely a secondary form of
some other fungus, and inhabit the same cavity, as in the case of
Æcidium cyparissiæ and Uromyces scutellatus, Æcidium leucospermum and
Puccinia Anemones, and others.
[Illustration: Fig. 33. Puccinia Graminis.]
The order Pucciniæi comprises epiphytes, as well as entophytes. The
mildew on wheat is caused by the Puccinia Graminis (fig. 33), which
attacks the stem of the plant, and appears on its exterior in a circular
cluster of pear-shaped septate spore cases. These spore cases spring
from a filamental mycelium, whose threads interweave themselves among
the soft tissue of the stem of the wheat, and the fertile threads make
their way through the stomates to the surface. Professor Henslow has
proved that the rust which appears on the leaves and chaff scales of
wheat is owing to the Uredo linearis, a secondary form of the Puccinia
Graminis, and that rust is only an earlier form of mildew; so that the
Puccinia Graminis is a dimorphous and epiphytic fungus. It may be a
question whether the Uredo segetum, which destroys the blossom of wheat,
and reduces the ear to the sooty mass of powder called smut, may not be
the form of some other fungus. The epiphytes of the order Pucciniæi
often appear on the exterior of plants in tufts of brown, yellow,
orange-coloured, or white sporangia.
Fungi are extensively propagated by fragments of their spawn, and the
threads of the mycelia are sometimes diminished in thickness in order
that they may more easily penetrate into the stomates of the plant they
invade. This was discovered by Mr. Berkeley while investigating the
germination of the spores of bunt, a fœtid rust which attacks wheat and
other grasses. It is perfectly analogous to the diminution of the size
of the dust spores in the successive orders of fructification. It is
thought probable that in many of the parasitic fungi, new spores are
formed at the tips of the fructiferous threads of the mycelium as fast
as the ripe spores fall off, whence that enormous mass of minute spores
which a single individual is capable of producing.
Among the multitudes of known parasitic fungi, there is not one that
does not form a mycelium more or less distinct. They do not arise from a
disease in the plant they attack, though they ultimately cause disease
and often death. Each parasite has its own mode of penetrating into the
tissues, and its own manner of vegetating; they attack certain plants,
and avoid others though nearly allied.
Dust spores, single or septate, oozing out of a dark or coloured fungous
mass is characteristic of the group Melanconiei, which is more
remarkable in regard to the mode of fructification than any of the
preceding Coniomycetes, for instead of successively assuming the form
and fructification of two genera, or two orders, the plants successively
assume the form and fructification of two distinct families.
The family of the HYPHOMYCETES takes its name from its filamentous
character. The mycelium gives rise to white, dark brown, or bright
coloured threads, simple or compound, bearing naked spores on their
extremities. Of these there are five sub-orders and many genera.
The sub-order Isariacei has four genera found on the pupæ of moths, on
dead spiders, dead fungi, and dead plants respectively. The group is
characterized by compound threads ending in pulverescent spores. Most of
the caterpillars of the Bombyx Rubi, or bramble moth, fall victims to a
species of Isaria, which has several distinctly different periods and
modes of fructification, and at last assumes the form of a very
beautiful fungus belonging to a different family.
Near Paris, in the month of October, when the caterpillars of the
bramble moth seek for shelter from the cold, in the earth, or under long
grass and withered leaves, M. Tulasne and his brother found that most of
them were surrounded by tufts of a whitish down, which increased so
rapidly that it killed the caterpillars and covered the whole of their
body except the bristly hairs, and assumed characters similar to the
muscardine fungus that kills the silkworm. This down is a mycelium
composed of extremely fine branched filaments felted together, the
upright fertile branches of which bear whorls of branchlets each
terminated by chaplets of from ten to fifteen equal and spherical cells
filled with dust spores. These most minute spores germinated, and put
out filiform creeping germs which quickly emitted many branches ending
in long chaplets of fertile dust-bearing cells.
Points here and there on the felted envelope of the caterpillars became
of an orange colour, took the form of a mycelium, and produced little
orange coloured club-shaped cells which shed abundance of reproductive
dust spores from a ring of white hairs on their summit. Each caterpillar
had from ten to fifteen of these coloured clubs on its sides, which lost
their brightness when they grew old, and had shed their dust spores.
These fungi possessed all the characters of the Isaria crassa, or Isaria
farinosa of Fries.
Later in the season other caterpillars on which this club-shaped Isaria
had not been produced, but which were swollen and white with the felted
spawn of the parasite, gave out orange red club-shaped vessels of a
larger size and deeper tint than those of the nascent Isariacei. They
had no terminal ring of hairs, but some of them had a red spore
dust-bearing felt at their base. Ultimately they assumed all the
characters of the Sphæria militaris of Ehrenberg or Cordyceps militaris
of Fries, which is a bright scarlet fungus half an inch high with a
fleshy upright stem ending in a cup-shaped head containing long
cylindrical sacs called asci, in which the spore cells are so numerous
as to resemble strings of beads.[55] This fungus, therefore, begins as a
member of the family Hyphomycetes, and ends as a member of the family
Ascomycetes.
The order Stilbacei are little globose fungi with or without a stalk,
covered with semi-gelatinous spores. They are united in cushion-like
masses, on decayed wood and dead twigs. The little scarlet masses on
dead currant branches so often seen in gardens, are examples.
The order Dematiei are the black moulds found on damp paper, old damp
linen, dead wood and plants. Their spawn is seldom much developed, the
fertile threads are erect, rigid, dark brown approaching to black,
sometimes of an olive green. The spores on their tops are either simple,
in whorls, or collected into heads, which are large, septate, and even
spiral.
The Mucedines are beautiful microscopic objects both as to form and
colour; they are very numerous both in genera and species and are well
known as red, blue, or green moulds. These fungi spring from many points
of a generally abundant mycelium, in erect coloured threads, bearing on
their tips simple naked spores, spores collected into little tufts, or
spores strung together like beads forming threads either branched or
simple. In this order of fungi there are, moreover, instances of
dualism, the second order of fruit being that of the family of the
Ascomycetes.
The Botrytis, or Peronospora infestans, which causes the murrain in
potatoes, shows how destructive the Mucedines can be. Like other
entophytes, its spores enter the stomates in the leaves of the potato,
and fill the cavities of the leaves with spawn, the ramifications of
which are said to be very beautiful. This creeping spawn then insinuates
itself into the stem and tuber, and from thence it finds its way to the
exterior of the plant, or to some internal cavity, where it fructifies,
bearing large globose sessile bodies yielding fruit of the second order,
and spores on the tips of its fertile branches. The spawn of the
Botrytis spreads rapidly in a circle, and soon destroys the texture of
the leaves and stem, but although it attacks the tuber or potato
generally so called, it does not penetrate deeply. The destruction of
the potato is aided and completed by the Fusisporium Solani, a
microscopic fungus, which takes various forms according to its age and
changing conditions, the last of which seems to be partly gelatinous; it
sometimes hardens the tissues of the potato, but sometimes causes rapid
and loathsome decay.
The thread-like fibres of the spawn of the Peronospora permeate even the
branches and wood of trees. Wasps are frequently seen to frequent hollow
trees, probably in search of the mycelia of some of these parasitic
fungi, which is identical in structure with the material of which their
nests are built. Signore Panceri, professor of comparative anatomy in
the university of Naples, has discovered seven species of Mucedines in
the albumen of hens’ eggs.
Chemical changes in preserved animal and vegetable substances afford
suitable food for the Penicillia mould, if indeed they are not the
immediate cause of these changes. The threads rising from the mycelium
of these moulds terminate in bundles of branchlets carrying at their
summits strings of spores, like necklaces of small beads collected into
bunches like tassels, white, yellowish, blue or red according to their
age or kind. Figure 34 represents various species of Mucedines, in which
_c_ is the Penicillium armeniacum, and _f_ is a spore of
Helminthosporium Hoffmanni; all are magnified. Different species of the
Penicillia form the blue and brick-red moulds on cheese, and the
greenish and grey moulds on jam and preserved fruit. They appear as dry
rot, as orange coloured spots on long kept potatoes, as mildew on cloth,
silk, sugar, meat, and even on weather-beaten window glass. They can
exist in metallic and poisonous solutions by decomposing the chemical
combination, rejecting the metal or poison, and living on whatever
nutriment may be found in the remainder. Like the larger fungi, these
minute plants are sometimes poisonous; the fatal effects occasionally
produced by sausages and spoilt meat are supposed to be owing to
poisonous moulds.
The Mucedines conform to the law prevailing in other low organizations
of having their species widely distributed. The Penicillium glaucum is
found in all countries, especially in the vicinity of man; it inevitably
appears in all saccharine substances, and, according to M. Fries, it is
met with alike in the alps of Lapland and in the oasis of Jupiter Ammon
in the Lybian desert, an example which has no parallel in the
geographical distribution of the higher plants.[56] Ferment, that is to
say, the yeast plant, is a peculiar condition of certain fungi,
including the present species, and is capable of unlimited propagation.
[Illustration: Fig. 34. Mucedines:—_a_, Aspergillus glaucus; _b_,
Aspergillus dubius; _c_, Penicillium armeniacum; _d_, Sepedonium
mycophilum; _e_, Helminthosporium nodosum; _f_, Helminthosporium
Hoffmanni, spore; _g_, Zygodesmus fuscus.]
The real spore-bearing filaments of the Penicillium glaucum are only
developed in air, for when the spores of that fungus are kept submerged
in a liquid favourable for their growth, as in a saccharine solution, or
the juice of the grape, they form an aquatic mycelium on the filaments
of which cells are produced, and carbonic acid gas is given out. These
cells increase by budding or division into chains of ferment, easily
separated into single cells. The Penicillium glaucum is thus developed
in all kinds of liquids, and in almost all kinds of conditions; even the
peculiar knotty filaments observed in its submerged mycelium are not
constant in different liquids. M. Hoffmann has observed with certainty
the passage of Penicillium glaucum into Penicillium candidum, into a
sulphur-coloured Penicillium, and, lastly, into the Coremium glaucum, so
that this fungus is polymorphous, although the conditions under which
the changes take place are unknown.[57]
It appears that substances and liquids do not ferment spontaneously, for
upon examining with a microscope the dust obtained by scraping the
exterior of gooseberries, plums, vine leaves, potatoes, &c., M. Hoffmann
found the short chains of the Torula, the necklace-like ferments of the
Mucedines, and the chaplets of others. Some had already begun to
germinate, and were developed readily when put into water. They had no
doubt been carried by the wind from the dry refuse of fermented
substances which are thrown away.
[Illustration: Fig. 35. Torula Cerevisiæ, showing successive stages of
cell multiplication.]
The yeast of beer was at one time considered to consist entirely of the
cells and chains of the Torula Cerevisiæ (fig. 35). This, which is one
of the Coniomycetes of the order Torulacei, is in its early stage a
colourless transparent globe capable of endless increase by budding.
When in a liquid favourable to its growth, as the wort of malt, buds in
the form of young cells spring from the walls of the globes; these soon
become perfect and acquire buds also, so that in a few hours the parent
cells develop themselves into rows of four or five globes, which remain
in contact while the plant is growing, but separate if anything checks
the fermentation. The full development of the plant only takes place
when the fermentation is allowed to continue for some time, and then it
is capable of producing a variety of forms, which show that it has other
modes of reproduction besides budding.[58] In fact, when the
fermentation is active in the upper parts of the liquid it appears in
chaplets of from four to twelve articulations, or sometimes it ramifies
into little branches.
More recent observations show that yeast is a peculiar state of the
mycelium of various fungi, of which, as already stated, a large
proportion is believed to consist of Penicillium glaucum, though it is
known that other kinds of mould also enter into its composition. These
plants grow naturally in a state of exposure to the atmosphere, but they
have the property of also developing themselves when submerged; and as
in this unnatural condition, which they bear when developed as yeast,
they cannot produce their proper fruit, they propagate themselves by
means of shoots from the altered mycelium. It has been observed that
mechanical injury destroys the vitality of German yeast, which consists
of yeast globules in a dried state. Thus a fall on the ground, or a
bruise caused by a blow or by careless handling, will kill the plant,
and such dead yeast becomes dark-coloured and glutinous, and soon
acquires an offensive smell.
The form of Penicillium glaucum which produces acetic fermentation,
known as the vinegar plant, has a filamental submerged instead of a
vesicular mycelium.
Ferments may be formed in the wort of beer, in the solutions of grape
and cane sugar, in the juice of gooseberries, currants, &c., by means of
the submerged spores of the Uredines segetum and Rosæ, of Ascophora
elegans, Mucor Mucedo, Periconia hyalina and others. There are active
exchanges continually going on between the contents of the globules of
ferments and the exterior liquid, and therefore a continual chemical
action.[59]
M. Pasteur’s experiments on the nourishment of the Mucedines concur with
the observations of others in showing that these plants are the origin
of all fermentation properly so called. When he put a mere trace of the
beer yeast fungus into pure water holding in solution the three
crystallizable substances, sugar candy, an ammoniacal salt, and some
phosphates, the globules of yeast were seen to multiply, deriving their
nitrogen from the ammoniacal salt, their carbon from the sugar, and
their mineral material from the phosphates; at the same time the sugar
fermented. The same results were obtained from lactic yeast. M. Pasteur
now sowed the spores of the Penicillium, or of some other mucedinous
fungus in pure distilled water holding in solution the same ingredients,
except that an acid salt of ammonia was employed to prevent the
development of infusoria, which would soon have stopped the progress of
the microscopic plant by absorbing the oxygen without which fungi cannot
live. The result was the same as in the preceding case. There is
consequently a complete analogy between the ferments, the mucedines, and
plants of more complex structure. If in these experiments any one of the
principles in the solution be omitted, the vegetation is arrested. The
quantities of these substances in the air, the water, or in the spores
themselves, are not sufficient to make up for the suppression of any one
of them. For example, the carbonic acid in the air or water does not
make up for the omission of the sugar. The mucedines and fungi generally
obtain their carbon from their food and from rain water, for rain water
holds in solution nitrates and ammoniacal salts together with salts of
potash and lime, and M. Barral has ascertained the existence of
phosphates also. M. Barral found that the nitrates and ammonia disappear
under the influence of cryptogamic plants.[60]
In the genus Oidium, belonging to the Mucedines, the short threads have
a string of spores, like a necklace of beads, on their tops. Species of
this genus are found on damp paper and honeycombs; also on decayed
oranges, and other spoilt fruits.
The family of the ASCOMYCETES produces spore-bearing cells, called
sporidia, enclosed in long cylindrical sacs or asci, in the definite
numbers two, four, eight, sixteen, thirty-two, &c. The great
characteristic of this large group, consisting of six orders, is the
fleshy soft texture and the more or less complete exposure of the
fructiferous surface. In one division the asci are persistent; this
includes the Elvellacei, the Tuberacei, the Phacidiacei, and the
Sphæriacei. In the other division the asci are often evanescent, and
this includes the Perisporiacei and the Onygenei.
The genera Peziza and Helvella are the principal fungi belonging to the
order Elvellacei. The Pezizæ are a very numerous race, and consist of
brilliantly coloured little cups, with or without stems, and more or
less concave. They grow in the cooler part of the temperate zone, many
show themselves in spring, and some of the largest and most beautiful
appear during the melting of the snow.[61] A few are subterranean, and
128 species inhabit Great Britain, many growing on the ground, others on
stumps of trees, dead sticks and timber, on living plants, damp walls,
&c. They are singularly beautiful, including ‘many of the most elegant
fungi, from the little white and red Peziza elegans, which is sprinkled
over almost every fallen twig of the larch and other conifers; the pale
toothed cups of the P. coronata, which abounds on the dead stems of
herbaceous plants; the scarlet P. scutellata with its edge fringed with
tawny hairs, and the graceful mouse-grey P. macropus, to the gorgeous P.
coccinea, which attracts attention from its elegant form and bright
colours; the more irregular, but not less brilliant P. aurantia, and the
font-shaped P. acetabulum, which might form an elegant pattern for an
architect or silversmith. Fifty others might be mentioned of equal
pretensions to grace of form and brilliancy of colouring.’[62] Some of
the genus are peculiar in their fructification, for in several plants of
this group, besides asci containing eight sporidia, M. Tulasne met with
cells full of eel-shaped particles like those in the Algæ, and although
without motion he considered them to be analogous to the pollen of
flowering plants. In the Peziza aurantia, however, the particles were
staff-shaped and motile.
The genus Helvella may be regarded as Peziza with the cup inverted;
consequently, it assumes the character of a pileus or hat, like a common
mushroom, though often very different in shape, and, instead of
spore-bearing gills, it has asci containing eight sporidia sunk in its
fleshy texture. The pileus is ovate or mitre-shaped in some species and
the margin free, in others it is more or less attached to the stem. When
the pileus and stem are perfectly soldered together, we get the
club-shaped species of the group.
Some obscure forms of this group, forming the genus Ascomycetes, cause
the leaves of the peach, walnut, and pear to blister. They consist of
little more than asci, accompanied by short necklace-shaped thread.
The Morchella esculenta, which is the morel, is so plentiful in some
parts of England, that it is used for making katsup; while the Cyttaria,
which is indigenous in the southern hemisphere, is the staple food of
the Fuegians during many months of the year; its subgelatinous
consistence indicates a nutritious principle. This species has the
peculiarity of growing upon living branches, after the manner of the
jelly-like fungus of the juniper.
M. Tulasne has discovered in Peziza, and in the genus Bulgaria and
others, certain minute bodies, which he considered to be of the nature
of the eel-shaped particles or antherozoids in the Algæ. Besides, he has
shown that several species of Peziza have a second form of fruit. Fries
had long before pointed out the identity of Fusarium tremelloides and
the orange coloured Peziza common on nettle stems. Many of the larger
Pezizæ and Helvellæ eject their sporidia with great elastic force. This
is particularly remarkable in the Peziza vesiculosa, common in hot-beds,
when the sun is shining; the least agitation raises a visible cloud of
sporidia like vapour. The motions of the sporidia in the genus
Vibrissea, which grows on twigs partly immersed in water, is very
peculiar. They are exceedingly long and slender, and, when partly
ejected, they wave about in the sunshine till they are expelled.
The fungi of the order Tuberacei are nearly all subterranean, and their
fruit-bearing surface, as in the truffle, is internal. The asci are
either irregularly deposited in cavities, or in the denser tubers they
are sprinkled through a dark substance which is mottled with a paler
tissue. The truffle, which is the most important and best known of the
order, has a dark corrugated exterior, and the asci are represented by
large pyriform sacs containing sporidia covered with a reticulated or
spinose coat; but these spines are only the angles of continuous cells,
and are beautiful microscopic objects. Truffles prefer calcareous soil,
and a temperate climate. In England, they are found in Rutlandshire, and
numerous species grow in Northamptonshire, but they are smaller than the
continental truffles, which increase in abundance and size towards the
south, and have their maximum in Italy, where they grow on the roots of
trees and vines, and are hunted by dogs, or traced by the presence of a
peculiar fly, and dug up for sale. Sometimes the dogs dig them up, to
the annoyance of the proprietors of vineyards, from the mischief they do
to the roots of the vines.
The Sphæriacei, another order of Ascomycetes, are enormously numerous.
There are 1,000 well known species of this order, and probably twice as
many undetermined; for there is scarcely a twig or dry branch in the
forests, hedges, or gardens on which they may not be found. The rose
tree, the oak, and other plants harbour more than one species at a time.
The genus Cordyceps and many so-called species of Sphæria are only the
ultimate development of fungi of other families. The Cordyceps purpurea,
discovered by M. Tulasne on the ergot of wheat, has a short, upright,
slender stem, with a minute pale purple globose fruit-bearing head. In
this ergotized state the white substance of the grain is converted into
a firm mass without any appearance of meal, and having very powerful
properties. When sown, it is found to produce the Cordyceps. Mr. Currey
found the same plant on the ergot of the common reed, and there are
several other species of Cordyceps, all of which are only the second
form of ergot. To these may be added the Cordyceps militaris of
Ehrenberg, already shown (p. 283) to be the ultimate development of the
Isaria, which attacks the caterpillars of the bramble moth; and the
Cordyceps Robertsii, which grows like a bunch of rushes from the head of
the Hepialus virescens of New Zealand; whilst a kind of wasp in the West
Indies, which continues to fly about after it is attacked, is at last
killed by branching Cordyceps, which project from its head like a pair
of antlers. But the largest of all these parasites grows on an enormous
larva found on the banks of the river Murrumbidgee in Australia. It
appears that species of Sphæriæ are parasitic on insects of very
different affinities in China, America, and Europe. It may be presumed
that, like the Cordyceps militaris, they are the ultimate development of
fungi belonging to other families.
[Illustration: Fig. 36. Sphæriacei:—Sphæria Desmazierii; _a_, ascus;
_b_, sporidia; _c_, mycelium with conidia. Mucedines:—_d_, Botrytis
curta.]
In the genus Sphæria the fungus springs at once from its mycelium, and
consists of a perithecium or external case, to the internal walls of
which the asci are fixed. Each ascus contains eight sporidia or spore
cells, and when the fruit is ripe the asci are emitted through a pore or
slit in the perithecium or external coat. Fig. 36 represents the
fructification of Sphæria Desmazierii. Sphæria bombarda is like an
assemblage of minute black beads lying flat and crowded together upon
decayed wood; each bead is an oblong vesicle pierced at the apex for the
emission of the microscopic sporidia, or spore cells. The Sphæria
aquila, found upon decayed wood, has its fruit-bearing vessels seated
upon thickly matted fine threads. In some species they are in tufts;
others have bottle-shaped perithecia sunk into the stems of the
berberry, laburnum, and decayed oak palings; and lastly the candle snuff
Sphæria may frequently be seen like patches of soot at the bottom of
stakes or gate posts. More than two hundred well ascertained species of
the genus Sphæria are native in Great Britain alone.
The genus Nectria, which forms a connecting link between the genera
Peziza and Sphæria, has several interesting species, as the Nectria
Peziza, which grows in a congeries of most minute cups forming a bright
orange-coloured patch on decayed stumps of trees.
In the order Perisporacei the perithecia, or external cases, are free
and become dehiscent at last, but when young these fungi consist of
cellular jointed filaments like necklaces, rising upright from their
mycelia, and bearing reproductive bodies. In this state they constitute
the mildew on the vine, rose tree, turnip, hop, pea, &c. They are true
parasites, appropriating the juices, and filling up the breathing pores
of the leaves, so as to cause disease and often death. The vine mildew,
which has been called Oïdium Tuckeri, but which is now supposed to be an
imperfect state of Erysiphe, never advances beyond this state,
consequently it never has more than one form of fruit. Mr. Berkeley has
discovered that, on the contrary, the hop and pea mildews, which belong
to the genus Erysiphe, have five different modes of reproduction. The
destructive power of these fungi is strongly illustrated by the
extraordinary energy of their mycelia in draining the vital juices of
the plants on which they live in order to form such various kinds of
fruit; and the quantity of fruit produced is so enormous, that if the
whole were to germinate no genus of plants for which they have an
affinity could escape annihilation. Other species of Erysiphe have at
least three different modes of reproduction. The perithecia of some of
these fungi are beautiful objects for the microscope.
The Physomycetes, which form the sixth and last order of the great
fungus family, have bladder-like fertile cells scattered on threads, the
number of sporidia within the cells being indefinite. The Antennariei
are dark coloured felt-like fungi which run over the leaves of living
trees, and have fruit on black threads, which in some species, when
magnified, resemble the antennæ of certain beetles. The species of this
order are not common in Britain, and they are supposed to be only a
condition of some other fungi. They are certainly spore-bearing plants,
yet the fruit-bearing cells of the Antennaria Robinsonii sometimes
contain a ready formed miniature of the parent plant waiting to be set
free,—a singular analogy between these microscopic fungi and flowering
plants.
The order Mucorini, or moulds, has threads springing from the spawn,
bearing on their extremities large vascular sacs containing asci with
spore cells. The genus Ascophora contains several remarkable species, as
Ascophora elegans, which has two kinds of fruit, and attacks bread while
yet hot from the oven: however, the spores were probably in the dough,
for it has been ascertained that the spores of some of the lower fungi
retain their vitality after being exposed to the temperature of boiling
water. The Mucors are probably found on decayed and decaying matter all
over the world; they grow on fat, on greasy walls, and on decaying fruit
and vegetables.
The extreme minuteness of the reproductive bodies of the microscopic
fungi, many of which are not more than the 20,000th part of an inch in
diameter, and their extraordinary and varied forms even in the same
plant, have made these fungi one of the most difficult studies in the
whole science of botany. There is still some obscurity with regard to
those minute motile bodies supposed to be male particles, and their
analogues, which have not been seen, or have rarely been seen to
germinate. These bodies have been observed in comparatively few genera,
and nothing more than mere molecular motion has been observed in them.
One of the most unaccountable circumstances in the history of the lower
fungi is their sudden appearance in immense numbers, and the rapid
extension of disastrous and destructive epidemics caused by them among
plants and animals, as the potato murrain and the vine disease, which,
though widely spread through Europe and Madeira, leaves the North
American vines unscathed, whether grown at home or abroad. The black
mildews at one time raged so much in the Azores and Ceylon as to
threaten the complete annihilation of the orange and coffee plantations.
Their ravages have been scarcely less among the olive trees in some
parts of Europe; and the Lanosa nivalis, which grows in the melting snow
in spring, is supposed to be the cause in many instances of the death of
the germs of the sprouting rye. The destructive course of most of these
has abated, but the silkworm disease still continues. The fungi require
warmth and a moderate degree of moisture for their development, but the
unwonted multitudes in which the parasites occasionally appear, possibly
indicate some meteoric influences of which we are ignorant.