subject to as much variation as the form. The more fine and more delicate
shades are of rose, yellow-dun or yellow, violet, ashy-grey, clear
fawn colour, yellow-orange, olive-green, brick-red, cinnamon-brown,
reddish-brown, up to sepia-black and other combinations. It is only by
the microscope and transparency that one can make sure of these tints;
upon a sufficient quantity of agglomerated spores the colour may be
distinguished by the naked eye. Colour, which has only a slight
importance when considered in connection with other organs, acquires
much in the spores, as a basis of classification.
With the growth of Agarics from the mycelium, or spawn, we are not
deficient in information, but what are the conditions necessary to
cause the spores themselves to germinate before our eyes and produce
this mycelium is but too obscure. In the cultivated species we proceed
on the assumption that the spores have passed a period of probation in
the intestines of the horse, and by this process have acquired a
germinating power, so that when expelled we have only to collect them,
and the excrement in which they are concealed, and we shall secure a
crop.[C] As to other species, we know that hitherto all attempts to
solve the mystery of germination and cultivation has failed. There are
several species which it would be most desirable to cultivate if the
conditions could be discovered which are essential to germination.[D]
In the same manner the _Boleti_ and _Hydnei_--in fact, all other
hymenomycetal fungi, with the exception of the _Tremellini_--still
require to be interrogated by persevering experiment and close inquiry
as to their mode of germination, but more especially as to the
essential conditions under which alone a fruitful mycelium is
produced.
[Illustration: FIG. 79.--(_a_) Basidia and spores of _Exidia spiculosa_;
(_b_) Germinating spore.]
The germination of the spore has been observed in some of the
_Tremellini_. Tulasne described it in _Tremella violacea_.[E] These
spores are white, unilocular, and filled with a plastic matter of
homogeneous appearance. From some portion of their surface an
elongated germ filament is produced, into which the contents of the
reproductive cell pass until quite exhausted. Other spores, perhaps
more abundant, have a very different kind of vegetation. From their
convex side, more rarely from the outer edge, these particular spores
emit a conical process, generally shorter than themselves, and
directed perpendicularly to the axis of their figure. This appendage
becomes filled with protoplasm at the expense of the spore, and its
free and pointed extremity finally dilated into a sac, at first
globose and empty. This afterwards admits into its cavity the plastic
matter contained in its support, and, increasing, takes exactly the
form of a new spore, without, however, quite equalling in size the
primary or mother spore. The spore of the new formation long retains
its pedicel, and the mother spore which produced it, but these latter
organs are then entirely empty and extremely transparent. Sometimes
two secondary spores are thus engendered from the same spore, and
their pedicels may be implanted on the same or on different sides, so
as to be parallel in the former case, and growing in opposite
directions in the latter. The fate of these secondary spores was not
determined.
[Illustration: FIG. 80.--Germinating spore and (_a_) corpuscles of
_Dacrymyces deliquescens_.]
In _Dacrymyces deliquescens_ are found mingled amongst the spores
immense numbers of small round or ovoid unilocular bodies, without
appendages of any kind, which long puzzled mycologists. Tulasne
ascertained that they are derived from the spores of this fungus when
they have become free, and rest on the surface of the hymenium. Each
of the cells of the spore emits exteriorly one or several of these
corpuscles, supported on very short slender pedicels, which remain
after the corpuscles are detached from them. This latter circumstance
evidences that new corpuscles succeed the firstborn one on each
pedicel as long as there remains any plastic matter within the spore.
The latter, in fact, in consequence of this labour of production,
becomes gradually emptied, and yet preserves the generative pedicels
of the corpuscles, even when it no longer contains any solid or
coloured matter. These pedicels are not all in the same plane, as may
be ascertained by turning the spore on its longitudinal axis; but it
often seems to be so when they are looked at in profile, on account of
the very slight distance which then separates them one from another.
It will also be remarked that they are in this case often implanted
all on the same side of the reproductive body, and most often on its
convex side. Their fecundity is exhausted with the plastic contents of
the spore. The corpuscles, when placed in the most favourable
conditions, have never given the least sign of vegetation; they have
also remained for a long time in water without experiencing any
appreciable alteration.
All the individuals of _Dacrymyces deliquescens_ do not produce these
corpuscles in the same abundance; those which bear the most are
recognizable by the pale tint of the reproductive dust with which they
are covered; in others, where this dust preserves its golden
appearance, only a few corpuscles are found. The spores which produce
corpuscles do not appear at all apt to germinate. On the other hand,
multitudes of spores will germinate which had not produced any
corpuscles. Tulasne remarks on this, that these observations would
authorize us to think that all spores, though perfectly identical to
our eyes, have not, without distinction, the same fate, nor doubtless
the same nature; and, in the second place, that these two kinds of
bodies, if they are not always isolated, yet are most frequently met
with on distinct individuals. This author claims for the corpuscles in
question that they are spermatia, and thinks that their origin is only
so far unusual in that they proceed from veritable spores.
The whole of the _Gasteromycetes_ have as yet to be challenged as to
the mode and conditions of germination and development. It is probable
that these will not materially differ from those which prevail in
_Hymenomycetes_.
The germination in _Æcidium_ has been followed out by Tulasne,[F]
either by placing the pseudospores in a drop of water, or confining
them in a moist atmosphere, or by placing the leaves on which the
_Æcidium_ flourishes upon water. The pseudospores plunged in water
germinated more readily than the others. If the conditions were
favourable, germination would take place in a few hours. _Æcidium
Ranunculacearum_, D. C., on leaves of figwort, gives rarely more than
one germinating filament, which soon attains three times the length of
the diameter of the pseudospore. This filament generally remains
simple, sometimes torulose, and distorted in a long spire. Sometimes
it has been seen divided into two branches, nearly equal to each
other. The spore in germinating empties itself of its plastic
contents, contracts, and diminishes in size. The pseudospores of
_Æcidium crassum_, P., emit three long filaments, which describe
spirals, imitating the twistings of the stem of a bean or bindweed. In
_Æcidium Violæ_, Schum, one filament is produced, which frequently
rolls up its anterior extremity into a spire, but more often this same
extremity rises in a large ovoid, irregular vesicle, which continues
the axis of the filament, or makes with it a more or less decided
angle. In whatever manner placed, this vesicle attracts to it all the
orange protoplasm, and hardly does this become settled and complete
before the vesicle becomes the starting point of a new development,
for it begins to produce at its apex a filament, more slender than the
previous one, stiff, and unbranched.
[Illustration: FIG. 81.--Germination of _Æcidium Euphorbia (sylvaticæ)_,
Tulasne.]
According to M. Tulasne, the germination of the pseudospores of
_Æcidium Euphorbiæ_ on _Euphorbia sylvatica_ differ in some respects
from the preceding. When dropped upon water these spores very soon
emit a short tube, which ordinarily curves in an arch or circle,
almost from its origin, attaining a length of from three to six times
the diameter of the spore; then this tube gives rise to four spicules,
each of which produces a small obovate or reniform sporule; the
generation of these sporules absorbs all the plastic matter contained
in the germ-tube, which permits of the observation that it was divided
into four cells corresponding with the number of spicules. These
sporules germinate very rapidly from an indefinite point of their
surface, emitting a filiform process, which is flexuous and very
delicate, not extending more in length than three times that of the
long axis of the sporule, often less, reproducing at its summit a new
sporule, differing in form and size from that which preceded it. This
sporule of the second formation becomes at its apex a vital centre,
and sprouts one or more linear buds, of which the elongation is
occasionally interrupted by the formation of vesicular swellings. As
Tulasne observes, the pseudospores of the _Æcidium_ and the greater
number of Uredines are easily wetted with water before arriving at
maturity; but when they are ripe, on the contrary, they appear to be
clothed with a greasy matter which protects them from the liquid,
forcing them almost all to rest on the surface.
The pseudospores of _Roestelia_ are produced in strings or chaplets,
as in _Æcidium_, with this difference, that instead of being
contiguous they are separated by narrow isthmuses. The ripe
pseudospores are enveloped in a thick tegument, of a dark brown
colour. They germinate readily on water, producing a filament fifteen
times as long as the diameter of the spore. This filament is sometimes
rolled or curved. Towards its extremity it exhibits protuberances
which resemble the rudiments of ramuli, or they terminate in a vesicle
which gives rise to a slender filament. The tegument of these
pseudospores, above all in those which have germinated, and have
consequently become more transparent, it is easy to see has many
pores, or round ostioles.
In _Peridermium_ the pseudospores, when dropped upon water, germinate
at any point of their surface. Sometimes two unequal filaments issue
from the same spore. After forty-eight hours of vegetation in the air,
the greater part had already emitted a multitude of thick little
branches, themselves either simple or branched, giving to the
filaments a peculiar aspect. Tulasne did not on any occasion observe
the formation of secondary spores.
In the Uredines proper the germination seems to be somewhat similar,
or at least not offering sufficient differences to warrant special
reference in _Uredo_, _Trichobasis_, _Lecythea_, &c. In _Coleosporium_
there are two kinds of spores, one kind consisting of pulverulent
single cells, and the other of elongated septate cells, which break up
into obovate joints. Soon after the maturity of the pulverulent
spores, each begins to emit a long tube, which is habitually simple,
and produces at its summit a reproductive cellule, or reniform
sporule. The orange protoplasm passes along the colourless tubes to
the terminal sporule at the end of its vegetation. The two forms of
spores in this genus are constantly found on the same leaf, and in the
same pulvinule, but generally the pulverulent spores abound at the
commencement of the summer. The reniform sporules begin to germinate
in a great number as soon as they are free; some few extend a filament
which remains simple and uniform, but more commonly it forms at its
extremity a second sporule. If this does not become isolated, to play
an independent life, the filament is continued, and new vesicles are
repeated many times.
[Illustration: FIG. 82.--Germinating pseudospores of (_b_) _Coleosporium
Sonchi_; (_s s_) secondary spores, or sporules (Tulasne).]
[Illustration: FIG. 83.--Germinating pseudospore (_b_) of _Melampsora
betulina_ (Tulasne).]
In _Melampsora_ the summer spores are of the _Lecythea_ type, and were
included in that genus till their relation with _Melampsora_ was
clearly made out. The winter spores are in solid pulvinules, and their
fructification takes place towards the end of winter or in the spring.
This phenomenon consists in the production of cylindrical tubes,
which start from the upper extremity of the wedge-shaped spores, or
more rarely from the base. These tubes are straight or twisted, simple
or bifurcated, and each of them very soon emits four monosporous
spicules, at the same time that they become septate. The sporules are
in this instance globose.
[Illustration: FIG. 84.--Germinating pseudospore of _Uromyce
appendiculatus_. (Tulasne.)]
In _Uromyces_ germination follows precisely the same type as that of
the upper cell of _Puccinia_; in fact, Tulasne states that it is very
difficult to say in what they differ from the _Pucciniæ_ which are
accidentally unilocular.
In _Cystopus_ a more complex method prevails, which will be examined
more closely hereafter.
In _Puccinia_, as already observed when describing their structure,
the pseudospores are two-celled. From the pores of each cell, which
are near the central septum, springs a clavate tube, which attains two
or three times the total length of the fruit, and of which the very
obtuse extremity curves more or less in the manner of a crozier.[G]
This tube, making a perfectly uncoloured transparent membrane, is
filled with a granular and very pale plastic matter at the expense
of the generative cell, which is soon rendered vacant; then it
gives rise to four spicules, usually on the same side, and at the
summit of these produces a reniform cellule. The four sporules so
engendered exhaust all the protoplasm at first contained in the
generative cell, so that their united capacity proves to be evidently
much insufficient to contain it, the more so as it leads to the
belief that this matter undergoes as it condenses an elaboration
which diminishes its size. In all cases the spicule originates
before the sporule which it carries, and also attains its full length
when the sporule appears. The form of the latter is at first
globular, then ellipsoid, and more or less curved. All these phases
of vegetation are accomplished in less than twelve hours, and if
the spore is mature and ready for germination, it is sufficient to
provoke it by keeping the pseudospores in a humid atmosphere.
During this process the two cells do not separate, nor does one
commence germination before the other, but both simultaneously.
When the sporules are produced, the protospore, somewhat analogous
to a prothallus, has performed its functions and decays. Towards
the time of the falling of the sporules they are nearly all divided
into four unequal cells by transverse and parallel septa. These
sporules in time produce, from any point on their surface, a
filament, which reproduces a new sporule, resembling the first, but
generally smaller. This sporule of the second generation ordinarily
detaches itself from its support before germinating.
[Illustration: FIG. 85.--Germinating pseudospore of _Puccinia Moliniæ_.
(Tulasne.)]
[Illustration: FIG. 86.--Germinating pseudospore of _Triphragmium
ulmariæ_ (Tulasne.)]
The pseudospores of _Triphragmium ulmariæ_ have been seen in April
germinating on old leaves of the meadowsweet which survived the
winter, whilst at the same time new tufts of the spores were being
developed on the leaves of the year. These fruits of the spring
vegetation would not germinate the same year. Each cell in germination
emits a long cylindrical filament, containing a brownish protoplasm,
on which four spicules, bearing as many sporules, are generated.
[Illustration: FIG. 87.--Germinating pseudospore of _Phragmidium
bulbosum_. (Tulasne.)]
The germination of the black fruits of _Phragmidium_ only appears to
take place in the spring. It greatly resembles that in _Puccinia_,
except that the filament is shorter, and the sporules are spherical
and orange-coloured, instead of being kidney-shaped and pale. In the
species found on the leaves of the common bramble, the filament
emitted by each cell attains three or four times the length of the
fruit. The granular orange protoplasm which fills it passes ere long
into the sporules, which are engendered at the extremity of pointed
spicules. After the long warty fruits are emptied of their contents
they still seem as dark as before, but the pores which are pierced in
the sides, through which the germinating filaments have proceeded, are
more distinctly visible.
It will be observed that throughout all these allied genera of
_Uromyces_, _Puccinia_, _Triphragmium_, and _Phragmidium_ the same
type of germination prevails, which confirms the accuracy of their
classification together, and renders still less probable the supposed
affinity of _Phragmidium_ with _Sporidesmium_, which was at one time
held by very astute mycologists, but which is now abandoned. This
study of germination leads also to a very definite conclusion with
regard to the genus _Uromyces_--that it is much more closely related
to _Puccinia_ and its immediate allies than to other unicellular
Uredines.
The germination of the pseudospores of the gelatinous Uredines of the
genus _Podisoma_ was studied by Tulasne.[H] These pretended spores,
he writes, are formed of two large conical cells, opposed by their
base and easily separating. They vary in length. The membrane of which
they are formed is thin and completely colourless in most of them,
though much thicker and coloured brown in others. It is principally
the spores with thin membranes that emit from near the middle very
obtuse tubes, into which by degrees, as they elongate, the contents of
the parent utricles pass. Each of the two cells of the supposed spore
may originate near its base four of these tubes, opposed to each other
at their point of origin, and their subsequent direction; but it is
rather rare for eight tubes, two by two, to decussate from the same
spore or basidium. Usually there are only two or three which are
completely developed, and these tend together towards the surface of
the fungus, which they pass, and expand at liberty in the air. The
tubes generally become thicker by degrees as they elongate, some only
slightly exceeding the length of the protospores. Others attain three
or four times that length, according to the greater or less distance
between the protospore and the surface of the plant. In the longest
tubes it is easy to observe how the colouring matter passes to their
outer extremity, leaving the portion nearest to the parent cell
colourless and lifeless. When nearly attaining their ultimate
dimensions, all the tubes are divided towards their outer extremity by
transverse septa into unequal cells; then simple and solitary
processes, of variable length and form, but attenuated upwards,
proceed from each segment of the initial tube, and produce at their
extremity an oval spore (teleutospore, Tul.), which is slightly curved
and unilocular. These spores absorb all the orange endochrome from the
original tubes. They appear in immense numbers on the surface of the
fungus, and when detached from their spicules fall upon the ground or
on any object which may be beneath them. So freely are they deposited
that they may be collected on paper, or a slip of glass, like a fine
gold-coloured powder. Again, these secondary spores (teleutospores)
are capable of germination, and many of them will be found to have
germinated on the surface of the _Podisoma_ whence they originated.
The germ filament which they produce springs habitually from the side,
at a short distance from the hilum, which indicates the point of
attachment to the original spicule. These filaments will attain to
from fifteen to twenty times the diameter of the spore in length
before branching, and are in themselves exceedingly delicate. The
tubes which issue from the primary spores (protospores, Tul.) are not
always simple, but sometimes forked; and the cells which are
ultimately formed at their extremities, though producing filiform
processes, do not always generate secondary spores (teleutospores) at
their apices. This mode of germination, it will be seen, resembles
greatly that which takes place in _Puccinia_.
[Illustration: FIG. 88.--Germinating pseudospores of _Podisoma Juniperi_.
(Tulasne)]
The germination of the Ustilagines was in part examined by Tulasne,
but since has received accessions through the labours of Dr. A.
Fischer von Waldheim.[I] Nothing, however, of any importance is added
to our knowledge of the germination of _Tilletia_, which was made
known as early as 1847.[J] After some days a little obtuse tube is
protruded through the epispore, bearing at its apex long fusiform
bodies, which are the sporules of the first generation. These
conjugate by means of short transverse tubes, after the manner of the
threads of _Zygnema_. Afterwards long elliptical sporules of the
second generation are produced on short pedicels by the conjugated
fusiform bodies of the first generation. (Fig. 89, _ss._) Ultimately
these sporules of the second generation germinate, and generate, on
short spicules, similar sporules of a third generation. (Fig. 89,
_st._)
[Illustration: FIG. 89.--Germinating pseudospore (_g_) of _Tilletia
caries_ with secondary spores in conjugation. (Tul.)]
In _Ustilago (flosculorum)_ germination takes place readily in warm
weather. The germ tube is rather smaller at its base than further on.
In from fifteen to eighteen hours the contents become coarsely
granular; at the same time little projections appear on the tube which
are narrowed at the base, into which some of the protoplasm passes.
These ultimately mature into sporules. At the same time a terminal
sporule generally appears on the threads. Secondary sporules
frequently grow from the primary, which are rather smaller, and these
occasionally give rise to a third generation.
In _Urocystis (pompholygodes)_ the germinating tubes spring
exclusively from the darker central cells of the clusters. From these
are developed at their extremity three or four linear bodies, as in
_Tilletia_, but after this no further development has as yet been
traced. It may be remarked here that Waldheim observed similar
conjugation of the sporules in some species of _Ustilago_ as have
been remarked in the sporules of the first generation in _Tilletia_.
[Illustration: FIG. 90.--Pseudospore of _Ustilago receptaculorum_ in
germination, and secondary spores in conjugation. (Tul.)]
[Illustration: FIG. 91.--Conidia and zoospores of _Cystopus candidus_;
_a._ conidium with the plasma divided; _b._ zoospores escaping; _c._
zoospores escaped from the conidium; _d._ active zoospores; _e._
zoospores, having lost their cilia, commencing to germinate.]