RUST, SMUT, MILDEW, & MOULD.
------------------------------------------------------------------------
LONDON:
GREAT QUEEN STREET,
LINCOLN’S-INN FIELDS, W.C.
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[Illustration:
Plate VII.
W. West imp.
]
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Rust, Smut, Mildew, & Mould.
---------------------
AN INTRODUCTION TO THE STUDY
OF
MICROSCOPIC FUNGI.
BY
M. C. COOKE,
AUTHOR OF “A PLAIN AND EASY ACCOUNT OF BRITISH FUNGI,” “INDEX
FUNGORUM BRITANNICORUM,” “A MANUAL OF BOTANIC TERMS,”
“A MANUAL OF STRUCTURAL BOTANY,” ETC.
Third Edition,
WITH NEARLY 300 FIGURES BY J. E. SOWERBY.
LONDON:
ROBERT HARDWICKE, 192, PICCADILLY.
1872.
------------------------------------------------------------------------
BY THE SAME AUTHOR.
THE BRITISH FUNGI: A Plain and Easy Account of British Fungi: with
especial reference to the Esculent and other Economic Species.
Illustrated with Coloured Plates of 40 Species. 2nd Edition. Fcap. 8vo.,
price 6s.
“The author is a thorough mycophagist, well acquainted with the peculiar
features by which the most remarkable of the edible kinds of Fungi may
be known.”—GARDENERS’ CHRONICLE.
“A very readable volume upon the lowest and least generally understood
race of plants. For popular purposes the work could not have been better
done.”—ATHENÆUM.
-------
INDEX FUNGORUM BRITANNICORUM: A Complete List of Fungi found in the
British Islands to the Present Date. Arranged so as to be applicable
either as a Check-List or for Herbarium Labels. Royal 8vo., price 2s.
6d.
Also the same Work, printed on only one side, for Herbarium Labels.
Part I. HYMENOMYCETES, 1s. Part II. GASTEROMYCETES, CONIOMYCETES,
and HYPHOMYCETES, 1s. Part III. ASCOMYCETES, 1s.
--------------
London: ROBERT HARDWICKE, 192, Piccadilly.
------------------------------------------------------------------------
PREFACE TO SECOND EDITION.
THE first edition of this Work having for some time been out of print,
and the demands of the public encouraging the publisher to proceed with
a new edition, I have added, in a second Appendix, descriptions of all
the species discovered in Britain since 1865, so far as they relate to
the Orders included in this volume. The success which has attended the
sale of this Work, and the number of fresh observers it has brought into
the field, has greatly tended to the necessity for a second Appendix. A
larger number of observers, over a still more extended area, will, it is
hoped, add further to our list; by increasing the number of known
species. Hitherto one great cause of the paucity of students of Fungi in
this country, especially of the Microscopic forms, has been the want of
text-books on the subject, containing descriptions of the species, with
figures illustrative of the genera. Although this little volume only
partly supplies that want, by including the species found on living
plants alone, it has already proved of service; this and its companion
volume, “Introduction to British Fungi,” being (with but one exception)
the only books on Fungi which have passed into a second edition in this
country; a fact which appears to prove that they have succeeded in
furnishing a desideratum, and in giving an impetus to the study. It is
hoped that similar results will follow the publication of this new
edition.
M. C. COOKE.
------------------------------------------------------------------------
CONTENTS.
CHAP. PAGE
I. CLUSTER-CUPS 1
II. SPERMOGONES 22
III. DI-MORPHISM 33
IV. MILDEW AND BRAND 45
V. COMPLEX BRANDS 67
VI. SMUTS 77
VII. COMPLEX SMUTS 90
VIII. RUSTS 95
IX. RUSTS (continued) 110
X. WHITE RUSTS 124
XI. MOULDS 138
XII. WHITE MILDEWS OR BLIGHTS 162
XIII. SUGGESTIONS 179
APPENDIX, CLASSIFICATION, AND 189
DESCRIPTIONS OF FUNGI CONTAINED
IN THIS VOLUME
APPENDIX II. 223
Index 239
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MICROSCOPIC FUNGI.
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CHAPTER I.
_CLUSTER-CUPS._
IN these latter days, when everyone who possesses a love for the
marvellous, or desires a knowledge of some of the minute mysteries of
nature, has, or ought to have, a microscope, a want is occasionally felt
which we have essayed to supply. This want consists in a guide to some
systematic botanical study, in which the microscope can be rendered
available, and in which there is ample field for discovery, and ample
opportunity for the elucidation of facts only partly revealed. Fungi,
especially the more minute epiphyllous species, present just such an
opportunity as many an ardent student would gladly take advantage of;
one great obstacle to the pursuit being hitherto found in the absence of
any hand-book to this section of the British Flora, embracing the
emendations, improvements, and additions of the past twenty-seven years
(the period at which the fifth volume of the “English Flora” made its
appearance). It would be incompatible with our object, and beyond our
limits, to introduce an entire mycological flora to our readers in these
pages; but we hope to communicate such information as will serve to
prepare the way still more for such an additional Flora, should it ever
be produced, and render the demand still wider and more general for such
an extension of our botanical literature. It is true that one work has
of late years issued from the press on this subject, but notwithstanding
its utility to scientific men as a record of species, it is practically
useless to those we address, from the absence of all specific
descriptions of microscopic fungi.
Let not the reader imagine, from what we have just stated, that it is
our intention to burden him with a dry series of botanical descriptions;
as much of this as we deem essential to render the book available to the
botanical student, we have preferred to add in the form of an Appendix.
Useful as these may be to some, we hope to be enabled to furnish for
others something more; and although we at once disclaim any intention of
including all the microscopic, or even the epiphytal fungi, in our
observations, yet we trust, by a selection of common and typical species
for illustration, and by an adherence to certain well-defined groups and
sections, to demonstrate that the microscopist will find an eligible
field for his observations in this direction, and the botanical student
may gain some knowledge of their generic and specific distinctions.
It is exceedingly difficult to give a logical definition of what
constitutes a fungus. It is no less difficult to furnish a popular
description which shall include all and nothing more. If, for example,
we particularize the spots and markings on the leaves and stems of
herbaceous plants, so commonly met with from early spring till the fall
of the last leaf, and even amongst the dead and decaying remains of the
vegetation of the year, we may include also such spots and marks as
result from insect depredations or diseased tissue. It is not always
easy, with a cursory observation under the microscope, to determine
whether some appearances are produced by fungi, insects, or organic
disease: experience is the safest guide, and until we acquire that we
shall occasionally fail.
If we take a stroll away from the busy haunts of men, though only for a
short distance,—say, for example (if from London), down to New
Cross,—and along the slopes of the railway cutting, we shall be sure to
find the plant called the goatsbeard (_Tragopogon pratensis_) in
profusion. In May or June the leaves and unopened involucres of this
plant will present a singular appearance, as if sprinkled with
gold-dust, or rather, being deficient in lustre, seeming as though some
fairy folk had scattered over them a shower of orange-coloured chrome or
turmeric powder. Examine this singular phenomenon more closely, and the
poetry about the pixies all vanishes; for the orange powder will be seen
to have issued from the plant itself. A pocket lens, or a Coddington,
reveals the secret of the mysterious dust. Hundreds of small orifices
like little yellow cups, with a fringe of white teeth around their
margins, will be seen thickly scattered over the under surface of the
leaves. These cups (called _peridia_) will appear to have burst through
the epidermis of the leaf and elevated themselves above its surface,
with the lower portion attached to the substratum beneath. In the
interior of these cup-like excrescences, or _peridia_, a quantity of the
orange-coloured spherical dust remains, whilst much of it has been shed
and dispersed over the unoccupied portions of the leaves, the stems, and
probably on the leaves of the grass or other plants growing in its
immediate vicinity. These little cups are fungi, the yellow dust the
spores,[1] or ultimate representatives of seed, and the epiphytal plants
we have here found we will accept as the type of the group or order to
which we wish to direct attention (Plate I. figs. 1-3).
[Illustration:
Plate I.
W. West imp.
]
Footnote 1:
Protospores they should be called, because, in fact, they germinate,
and on the threads thus produced the true spores, or fruit, are borne.
Amongst the six families into which fungi are divided, is one in which
the spores are the principal feature, as is the aurantiaceous dust in
the parasite of the goatsbeard. This family is named _Coniomycetes_,
from two Greek words, meaning “dust-fungi.” This group or family
includes several smaller groups, termed orders, which are analogous to
the natural orders of flowering plants. Without staying to enumerate the
characteristics of these orders, we select one in which the spores are
enclosed in a distinct peridium, as in our typical plant they are
contained within the cups. This order is the _Æcidiacei_, so called
after _Æcidium_, the largest and most important of the genera included
within this order.
The _Æcidiacei_ are always developed on living plants, sometimes on the
flowers, fruit, petioles, or stems, but most commonly on the leaves:
occasionally on the upper surface, but generally on the inferior. The
different species are distributed over a wide area; many are found in
Europe and North America, some occur in Asia, Africa, and Australia.
When the cryptogamic plants of the world shall have been as widely
examined and as well understood as the phanerogamic plants have been, we
shall be in a better position to determine the geographical distribution
of the different orders of fungi. In the present incomplete state of our
knowledge, all such efforts will be unsatisfactory.
But to return to the goatsbeard, and its cluster-cups. The little fungus
is called _Æcidium tragopogonis_, the first being the name of the genus,
and the last that of the species. Let us warn the young student against
falling into the error of supposing because in this, and many other
instances, the specific name of the fungus is derived from the plant, or
one of the plants, upon which it is found, that therefore the species
differs with that of the plant, and that, as a rule, he may anticipate
meeting with a distinct species of fungus on every distinct species of
plant, or that the parasite which he encounters on the living leaves of
any one plant is _necessarily_ specifically distinct from those found on
all other plants. One species of _Æcidium_, for instance, may hitherto
have been found only on one species of plant, whereas another _Æcidium_
may have been found on five or six different species of plants. The
mycologist will look to the specific differences in the parasite without
regard to the identity or distinctness of the plant upon which it is
parasitic.
Before the _Æcidium_ breaks through the epidermis, the under surface of
the leaves of the goatsbeard will appear to be covered with little
elevations or pustules, paler at the apex; these soon become ruptured,
and the fungus pushes its head through the opening, at the same time
bursting by radiating fissures. The teeth thus formed resemble those of
the peristome of some mosses. All around the orifice of the peridium the
teeth become recurved, and the orange spores are exposed, crowded
together within. At first, and while contained within the peridium,
these spores are concatenate or chained together, but when dispersed
they are scattered singly about the orifice, often mixed with the
colourless cells arising from the partial breaking up of the teeth of
the peridium.
Let us pause for a moment in our examination of the individual cups, to
ascertain their manner of distribution over the leaves. In this instance
they are scattered without any apparent order over the under surface,
but generally thickest towards the summit of the leaves; occasionally a
few are met with on the upper surface. Sometimes two or three touch at
the margins, but we have never met with them truly confluent; generally
there is a space greater than the width of the cups around each, the
stratum or subiculum from whence they arise is scarcely thickened, and
there are no spots or indications on the opposite surface. If a leaf be
taken fresh and the cuticle stripped off, which it will sometimes do
very readily, the orifices through which the _Æcidium_ has burst will
appear in irregular holes. If a section be made of one or two of the
fungi _in situ_, they will be seen to spring from beneath the cuticle,
the peridium to be simple, and rounded at the base, the spores clustered
at the bottom, and the fringe to be a continuation of its cellular
substance.
The spores in this species are orange, subglobose, sometimes angular,
and indeed very variable both in size and form, though the majority are
comparatively large. Each of these bodies is, doubtless, capable of
reproducing its species, and if we compute 2,000 cluster-cups as
occurring on each leaf, and we have found half as many more on an
ordinary-sized leaf, and suppose each cup to contain 250,000 spores,
which again is below the actual number, then we shall have not less than
five hundred millions of reproductive bodies on one leaf of the
goatsbeard to furnish a crop of parasites for the plants of the
succeeding year. We must reckon by millions, and our figures and
faculties fail in appreciating the myriads of spores which compose the
orange dust produced upon one infected cluster of plants of
_Tragopogon_. Nor is this all, for our number represents only the actual
protospores which are contained within the peridia; each of these on
germination may produce not only one but many vegetative spores, which
are exceedingly minute, and, individually, may be regarded as embryos of
a fresh crop of cluster-cups. And this is not the only enemy of the kind
to which this unfortunate plant is subject, for another fungus equally
prolific often takes possession of the interior of the involucre wherein
the young florets are hid, and converts the whole into a mass of
purplish black spores even more minute than those of the _Æcidium_, and
both these parasites will be occasionally found flourishing on the same
plant at the same time (Plate V. figs. 92-94).
Naturally enough, our reader will be debating within himself how these
spores, which we have seen, are shed in such profusion, can enter the
tissues of the plants which give subsequent evidence of infection; in
fact, how the yellow dust with which the goatsbeard of to-day is covered
will inoculate the young plants of next year. If one or two of these
spores are sprinkled upon the piece of the cuticle which we have
recommended to be removed from the leaf for examination, it will be seen
that they are very much larger than the stomata or breathing-pores which
stud the cuticle: hence it is clear that they cannot gain admittance
there. There remains but one other portal to the interior of the
plant—namely, the spongioles, or extremities of the roots. Here another
difficulty arises; for the spores are as large as the cells through
which they have to pass. This difficulty may be lessened when we
remember that what are termed the spores which are discharged from the
cups are not the true spores, but bodies from which smaller seed-like
vesicles are produced; yet, even then there will be much need of an
active imagination to invent hypotheses to cover the innumerable
difficulties which would encounter their passage through the vessels of
the infected plants. The Rev. M. J. Berkeley proved many years ago that
the spores of bunt, for example, may be caused to infect all the plants
the seeds of which had been placed in contact with them; but this
affection did not necessarily accrue from the absorption of the spores,
or the ultimate sporidia produced after three or four generations. It is
possible that the granular or fluid contents of the spores may be
absorbed by the plant, and as a result of this absorption, become
inoculated with the virus, which at length breaks out in fungoid
growths. Much has been done to elucidate this mystery of inoculation,
but much also remains a mystery still. There is no doubt that the
inoculation takes place at an early age,[2] probably in the seeds of
many plants; in others it may be conveyed with the moisture to the
roots; but the spores themselves have certainly not yet been traced
traversing the tissues of growing plants.
Footnote 2:
Dr. de Bary has lately shown that in many similar instances the
seed-leaves are inoculated. It will be necessary to refer more
particularly to his experiments hereafter.
If, instead of going in search of goatsbeard and its attendant fungus,
we turn our steps northward and enter one of the Highgate or Hampstead
woods, where the pretty little wood-anemone (_Anemone nemorosa_)
flourishes abundantly, and turn up the radical leaves, one by one, and
examine their under-surfaces, we shall at length be rewarded by finding
one covered with similar cluster-cups to those we have been describing
as occurring on the goatsbeard, but far less commonly. Leaf after leaf
will be found covered with the brown spots of another fungus called
_Puccinia anemones_, with which nearly every plant will be more or less
infected in the spring of the year; and at length, if we persevere, the
anemone cluster-cup (_Æcidium leucospermum_) will be our reward (Plate
I. figs. 4-6). The specific name will suggest one point of difference
between the two fungi, as in this instance the spores are white, and
somewhat elliptic. Probably this species is not common, as we have found
it but seldom, though often in search of it. A nearly allied species has
been found on _Anemones_ in gardens, having but few large teeth about
the orifice, though not constantly four, as the name would indicate (_Æ.
quadrifidum_).
A walk through almost any wood, in the spring of the year, will reward
the mycologist with another cluster-cup (_Æcidium_), in which the
peridia are scattered over the whole surface of the leaf. This will be
found on the wood spurge, giving a sickly yellowish appearance to the
leaves, on the under surface of which it is found. By experience one may
soon learn to suspect the occurrence of parasites of this nature on
leaves, from the peculiar exhausted and unhealthy appearance which they
assume as the spores ripen, and which will spare the labour of turning
over the leaves when there are no distinct spots on the upper surface.
_Æ. Euphorbiæ_ is found on several species of _Euphorbium_ or spurge,
but we have always found it most abundantly on the wood spurge in the
Kentish woods between Dartford and Gravesend. The spores in this species
are orange, and externally it bears considerable resemblance to the
goatsbeard cluster-cup, but the spores are rather smaller and paler, the
teeth are less distinct and persistent, the subiculum is more thickened,
and the peridia are more densely crowded.
There is another group of species belonging to the same genus of fungi
in which the arrangement of the peridia is different. One of the first
of our native wild flowers, in making its appearance after the departure
of frost and snow, is the little yellow celandine (_Ranunculus
ficaria_).
“Ere a leaf is on the bush,
In the time before the thrush
Has a thought about her nest,
Thou wilt come with half a call,
Spreading out thy glossy breast
Like a careless Prodigal;
Telling tales about the sun
When we’ve little warmth, or none.”
And one of the earliest parasitic fungi in spring is an _Æcidium_ which
flourishes on its glossy leaves. So common is _Æcidium ranunculacearum_
on this species of _Ranunculus_, that it can scarcely have escaped the
eye of any one who has taken the trouble to examine the plant. It
appears in patches on the under surface of the leaves or on their
petioles, in the latter case swelling and distorting them. Sometimes
these patches are nearly circular, at others of very irregular form, and
varying in size from less than one-twelfth of an inch to half an inch in
diameter. It is found on several species of _Ranunculus_, as _R. acris_,
_bulbosus_, and _repens_, but most commonly on _R. ficaria_. The leaf is
thickened at the spot occupied by the parasite, and generally without
indication on the opposite surface. Sometimes one spot, at others
several, occur on the same leaf. The peridia are densely crowded
together, often arranged in a circinate manner, _i.e._, like a
watch-spring, or the young frond of a fern. The spores are orange, but
slightly varying in tint on different species of _Ranunculus_ (Plate II.
figs. 12-14). One of the smaller clusters, when collected before the
spores are dispersed, or the teeth of the peridium discoloured, mounted
dry as an opaque object, makes a very excellent slide for an inch or
half-inch objective; and the same may be said of many others of the same
genus.
Less common than the foregoing is the species of _Æcidium_ which attacks
the violet. The sweetest of flowers as well as the earliest, in despite
both of its odour and its humility, becomes a victim to one or more of
the ubiquitous race of fungi. Thickened spots at first appear on the
leaves; the petioles, or flower stem, or even the calyx, become swollen
and distorted; and at length the cluster-cup breaks through. The spots
on the leaves upon which the peridia are scattered are yellowish,
generally larger than the clusters on the pilewort, and seldom with more
than one spot on each leaf. The peridia, or cups, are irregularly
distributed over the spots, not crowded together as in the last species;
and the teeth are large, white, and distinct. The spores are at first
orange, but at length become brownish. This species may be found in
spring, as late as June, most commonly on the dog-violet, but also on
other species of _Viola_.
It is not a very desirable occupation to search a bed of nettles, and
turn over the individual leaves to look for minute fungi. A very pretty
_Æcidium_ is nevertheless far from uncommon in such a habitat.
Fortunately it occurs very often on the petioles of the leaves and on
the stem, distorting them very much; and in such situations flourishing,
apparently, more vigorously than when occupying the under surface of the
leaves (Plate I. fig. 10). In the latter situation the clusters of
peridia are small, seldom exceeding a dozen in a spot, but several spots
may be found on the same leaf. On the stem they are clustered around for
upwards of an inch in length, and their bright orange colour in such a
situation renders them very conspicuous objects. The peridia are always
closely packed together upon a thickened base, and offer but slight
variations from the forms already enumerated, save that they widen
slightly at the mouth, so as to become nearly campanulate. The spores
are orange, and very profuse.
During the past summer we noticed, for the first time, a very pretty
little species of cluster-cup (_Æcidium_) on the wood sanicle (_Sanicula
Europæa_) in Darenth wood. It was far from uncommon, and we believe it
to be specifically distinct from its nearest ally, found on the earthnut
leaves, and those of some other umbelliferous plants. The little cups
are in small clusters of four or five together, on the under surface and
on the petioles; they are small, but the teeth are relatively large,
white, and distinct. The spores are of a pallid, yellowish colour, and
not so profuse as in the last species. A darker spot on the upper
surface of the leaf generally indicates their presence. This species was
found many years ago by Carmichael at Appin, and called by him _Æcidium
saniculæ_; but we find no notice of its occurrence since, though it
seems to be far from uncommon at Darenth, and probably elsewhere, should
the sanicle be common also.
Recently we found the bedstraw cluster-cup (_Æcidium galii_) on the
great hedge bedstraw (_Galium mollugo_), and as it has not been figured
before, we have included it amongst our illustrations (Plate II. figs.
15-17). Though very insignificant when occurring on the small leaves of
the yellow bedstraw (_Galium verum_), it is a prominent object on the
above-named species.
We received, for the first time, in July, 1864, from Mr. Gatty, student
at Winchester, a portion of a plant of _Thesium humifusum_ (which is by
no means common in Britain), covered with beautiful cluster-cups of a
species never before recorded as occurring in this country (Plate III.
figs. 50, 51) named _Æcidium Thesii_, but which is far from uncommon on
the Continent. It occurred in this instance on the Downs, in the
vicinity of Winchester.
It is unnecessary here to refer to other allied species of _Æcidium_,
except one to be presently noticed, since we have, at the end of the
volume, enumerated and given descriptions of all the species hitherto
found in Britain. Suffice it to say that the Buckthorn cluster-cups on
the alder buckthorn (_Rhamnus frangula_), is usually very common in the
Highgate and Hornsey woods, and on the common buckthorn (_Rhamnus
catharticus_) in the neighbourhood of Dartford, in Kent. That on the
honeysuckle we have found but very rarely. On the gooseberry and
red-currant leaves, commonly in some years and rarely in others; whilst
a few of those described we have never collected. The species on
different composite plants is subject to great variation, and on most
may be found in the autumn; one variety only, on the leaves of _Lapsana
communis_, we have met with in the spring.
Very few years ago farmers generally believed that the cluster-cups of
the berberry (_Berberis vulgaris_), were productive of mildew in corn
grown near them; this opinion even received the support of Sir J. Banks,
but no fungi can be much more distinct than those found on corn crops
and this species on the leaves of the berberry. In this instance the
cups are much elongated, and cylindrical, the clusters vary much in
size, and the spots on the upper surface of the leaf are reddish,
bright, and distinct. The teeth are white and brittle, and the orange
spores copious (Plate I. figs. 7-9).
There are scarcely any of the epiphyllous fungi forming equally handsome
or interesting objects for low powers of the microscope, than the genus
to which attention has just been directed; and they possess the
advantage of being readily found, for that locality must be poor indeed
which cannot furnish six species during the year. We have found half of
the number of described species within little more than walking distance
of the metropolis, within a period of little more than three months, and
should be glad to hear of the occurrence of any of the rest.
We have three species of fungi very similar in many respects to the
foregoing, but differing in others to such an extent as to justify their
association under a different genus and name. The hawthorn is a bush
familiar to all who love the “merry month of May,” but it may be that
its parasite has been unnoticed by thousands. If, for the future, our
readers will bear this subject in their minds when they stand beneath a
hawthorn hedge, they may become acquainted with clusters of singular
brown pustules on the leaves, petioles, and fruit well worthy of more
minute examination (Plate II. fig. 22). They scarcely claim the name of
cups, and their lacerated and fringed margins rather resemble the pappus
crowning the fruits of some composite plants than the cups of _Æcidium_.
The peridia are very long, and split down throughout their length into
thread-like filaments of attached cells; these gradually fall away and
break up into their component parts till but short portions remain
attached to the base of the peridia. These cells are elongated and
marked on the surface with waved lines, forming in themselves pretty
objects for a high power of the microscope (Plate II. figs. 23, 24). If
the teeth of _Æcidium_ resemble the peristome of some mosses, such as
_Splachnum_; the threads of this species of _Rœstelia_, except in not
being twisted, somewhat resemble the peristomes of other mosses of the
genus _Tortula_. The spores in this species are less conspicuous, being
of a light brown, and the whole plant, from its modest hue, may be
readily passed over without attracting attention unless occurring in
abundance.
The leaves of pear-trees afford a second species of this genus
sufficiently distinct to commend it to our notice. Sometimes it is very
common, at others but few examples are to be met with. The clusters
occur on the under surface, and consist of half-a-dozen or less of large
peridia, pointed at the apex and swelling in the middle so as to become
urn-shaped (Plate II. figs. 20, 21). These vessels or thecæ split into
numerous threads or laciniæ, which remain united together at the apex.
Like the species already noticed, this is brown and inconspicuous except
on account of its size, for it is the largest of all that we have had
occasion to notice.
The third species occurs on the under surface of the leaves of the
mountain-ash. The peridia are clustered on a rusty orange-coloured spot
which is visible on the upper surface (Plate II. figs. 18, 19). They are
long and cylindrical, with an evident tendency to curvature; the mouth
is serrated, but not split up into threads, as in the species found on
the hawthorn. There will often be found instead of well-developed
peridia, what at one time were regarded as abortive peridia, forming a
thickened orange or rust-coloured spot, studded with minute elevated
points. These spots are clusters of spermogones, which organs are
described in detail in our second chapter. The clusters and spores are
of a brighter reddish-brown than in either of the other species. All are
remarkably distinct, and perhaps the most curious and interesting of any
that we have passed in review. To botanists, the species found on the
hawthorn is known as _Rœstelia lacerata_, that on pear-leaves as
_Rœstelia cancellata_, and the one on the leaves of the mountain-ash as
_Rœstelia cornuta_.
Dr. Withering observed the spore-spots on the leaves of the
mountain-ash, but was evidently puzzled to account for them. He writes
(in his Arrangement of British Plants), “The spots on the leaves of
_Sorbus aucuparia_ consist of minute globules intermixed with wool-like
fibres. On examining many of them in different states, I at length found
a small maggot in some of the younger spots, so that the globules are
probably its excrement, and the fibres, the woody fibres of the plant
unfit for its food.” We now-a-days smile at such simple and singular
conjectures. It affords evidence of the manner in which the speculations
of one generation become follies in the next.
Only two species of cluster-cups are described in Withering’s Flora
under the genus _Lycoperdon_: one of these is now called _Æcidium
compositarum_, and is found on various composite plants; the other
includes the species found on the wood-anemone and that on the
moschatel, and also probably a species of _Puccinia_ on the wood-betony.
To render this chapter more complete, though of less importance to the
microscopist, we may allude to the other two genera comprised within
this order. _Peridermium_ is the name of one genus which contains two
British species found on the leaves and young shoots of coniferous
trees. In this genus the peridium bursts irregularly, and does not form
cups, or horns, or fringed vessels. The most common species is found on
the needle-shaped leaves of the Scotch fir (Plate II. fig. 27), and also
on the young twigs, in the latter instance larger and more prominent
than in the former. The elongated peridia burst irregularly at their
apices without forming teeth (fig. 28).
In the genus _Endophyllum_, as its name implies, the peridium is
imbedded within the substance of the succulent leaves. The only species
we possess is found rarely upon the common house-leek.
We have derived much pleasure in viewing the astonishment and delight
exhibited by friends to whom we have personally communicated specimens
of the little fungi we have enumerated for examination under the
microscope; and we recommend with confidence this group of parasitic
plants, unfortunately so little known, as well worthy of the attention
of all who are interested in the minute aspects of nature, and who can
recognize the hand—
“That sets a sun amidst the firmament,
Or moulds a dew-drop, and lights up its gem.”
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