1865.[Y] In view of the popular belief, he determined to sow the
spores of _Puccinia graminis_ on the leaves of the berberry. For this
purpose he selected the septate resting spores from _Poa pratensis_
and _Triticum repens_. Having caused the spores to germinate in a
moist atmosphere, he placed fragments of the leaves on which they had
developed their secondary spores on young but full-grown berberry
leaves, under the same atmospheric conditions. In from twenty-four to
forty-eight hours a quantity of the germinating threads had bored
through the walls and penetrated amongst the subjacent cells. This
took place both on the upper and under surface of the leaves. Since,
in former experiments, it appeared that the spores would penetrate
only in those cases where the plant was adapted to develop the
parasite, the connection between _P. graminis_ and _Æcid. berberidis_
seemed more than ever probable. In about ten days the spermogonia
appeared. After a time the cut leaves began to decay, so that the
fungus never got beyond the spermogonoid stage. Some three-year-old
seedlings were then taken, and the germinating resting spores applied
as before. The plants were kept under a bell-glass from twenty-four to
forty-eight hours, and then exposed to the air like other plants. From
the sixth to the tenth day, yellow spots appeared, with single
spermogonia; from the ninth to the twelfth, spermogonia appeared in
numbers on either surface; and, a few days later, on the under surface
of the leaves, the cylindrical sporangia of the _Æcidium_ made their
appearance, exactly as in the normally developed parasite, except that
they were longer, from being protected from external agents. The
younger the leaves, the more rapid was the development of the
parasite, and sometimes, in the younger leaves, the luxuriance was far
greater than in free nature. Similar plants, to the number of two
hundred, were observed in the nursery, and though some of them had
_Æcidium_ pustules, not one fresh pustule was produced; while two
placed under similar circumstances, but without the application of any
resting spores, remained all the summer free from _Æcidium_. It seems,
then, indubitable so far that _Æcidium berberidis_ does spring from
the spores of _Puccinia graminis_.
It has, however, to be remarked that De Bary was not equally
successful in producing the _Puccinia_ from the spores of the
_Æcidium_. In many cases the spores do not germinate when placed on
glass, and they do not preserve their power of germinating very long.
He reverts then to the evidence of experiments instituted by
agriculturists. Bönninghausen remarked, in 1818, that wheat, rye, and
barley which were sown in the neighbourhood of a berberry bush covered
with _Æcidium_ contracted rust immediately after the maturation of the
spores of the _Æcidia_. The rust was most abundant where the wind
carried the spores. The following year the same observations were
repeated; the spores of the _Æcidium_ were collected, and applied to
some healthy plants of rye. After five or six days these plants were
affected with rust, while the remainder of the crop was sound. In
1863 some winter rye was sown round a berberry bush, which in the
following year was infested with _Æcidium_, which was mature in the
middle of May, when the rye was completely covered with rust. Of the
wild grasses near the bush, _Triticum repens_ was most affected. The
distant plants of rye were free from rust.
[Illustration: FIG. 107.--Cells and pseudospores of _Æcidium berberidis_.]
The spores of the _Æcidium_ would not germinate on berberry leaves;
the berberry _Æcidium_ could not therefore spring from the previous
_Æcidium_. The uredospores of _Puccinia graminis_ on germinating
penetrate into the parenchym of the grass on which they are sown; but
on berberry leaves, if the tips of the threads enter for a short
distance into the stomates their growth at once ceases, and the leaves
remain free from parasites.
[Illustration: FIG. 108.--Cells and pseudospores of _Æcidium graveolens_.]
Montagne has, however, described a _Puccinia berberidis_ on leaves of
_Berberis glauca_ from Chili, which grows in company with _Æcidium
berberidis_. This at first sight seems to contradict the above
conclusions; but the _Æcidium_ which from the same disc produces the
puccinoid resting spores, appears to be different from the European
species, inasmuch as the cells of the wall of the sporangium are twice
as large, and the spores decidedly of greater diameter.[Z] The resting
spores, moreover, differ not only from those of _Puccinia graminis_,
but from those of all other European species.
From this account, then, it is extremely probable that the _Æcidium_
of the berberry enters into the cycle of existence of _Puccinia
graminis_, and, if this be true, wherefore should not other species
of _Puccinia_ be related in like manner to other _Æcidia_? This is the
conclusion to which many have arrived, and, taking advantage of
certain presumptions, have, we fear, rashly associated many such
forms together without substantial evidence. On the leaves of the
primrose we have commonly a species of _Æcidium_, _Puccinia_, and
_Uromyces_ nearly at the same time; we may imagine that all these
belong to one cycle, but it has not yet been proved. Again, _Uromyces
cacaliæ_, Unger, _Uredo cacaliæ_, Unger, and _Æcidium cacaliæ_,
Thumen, are considered by Heufler[a] to form one cycle. Numerous
others are given by Fuckel,[b] and De Bary, in the same memoir from
which we have already cited, notes _Uromyces appendiculatus_, Link.,
_U. phaseolorum_, Tul., and _Puccinia tragopogonis_, Ca., as
possessing five kinds of reproductive organs. Towards the end of the
year, shortly stipitate spores appear on their stroma, which do not
fall off. These spores, which do not germinate till after a shorter
or longer winter rest, may conveniently be called resting spores, or,
as De Bary calls them, _teleutospores_, being the last which are
produced. These at length germinate, become articulated, and produce
ovate or kidney-shaped spores, which in their turn germinate,
penetrating the cuticle of the mother plant, avoiding the stomates or
apertures by which it breathes. After about two or three weeks,
the mycelium, which has ramified among the tissues, produces an
_Æcidium_, with its constant companion, spermogonia--distinct cysts,
that is, from which a quantity of minute bodies ooze out, often in
the form of a tendril, the function of which is imperfectly known at
present, but which from analogy we regard as a form of fruit,
though it is just possible that they may be rather of the nature of
spermatozoids. The _Æcidia_ contain, within a cellular membranous
sac, a fructifying disc, which produces necklaces of spores, which
ultimately separate from each other in the form of a granular powder.
The grains of which it is composed germinate in their turn, no
longer avoiding the stomates as before, but penetrating through
their aperture into the parenchym. The new resultant mycelium
reproduces the _Uredo_, or fifth form of fructification, and the
_Uredo_ spores fall off like those of the _Æcidium_, and in respect of
germination, and mode of penetration, present precisely the same
phenomena. The disc which has produced the _Uredo_ spores now gives
rise to the resting spores, and so the cycle is complete.[c]
The late Professor Oersted, of Copenhagen, was of opinion that he had
demonstrated the polymorphy of the Tremelloid Uredines, and satisfied
himself that the one condition known as _Podisoma_ was but another
stage of _Roestelia_.[d] Some freshly gathered specimens of
_Gymnosporangium_ were damped with water, and during the night
following the spores germinated profusely, so that the teleutospores
formed an orange-coloured powder. A little of this powder was
placed on the leaves of five small sorbs, which were damped and
placed under bell-glasses. In five days yellow spots were seen on
the leaves, and in two days more indications of spermogonia. The
spermatia were discharged, and in two months from the first
sowing, the peridia of _Roestelia_ appeared, and were developed.
"This trial of spores," says Oersted, "has conduced to the result
expected, and proves that the teleutospores of _Gymnosporangium_,
when transported upon the sorb, give rise to a totally different
fungus, the _Roestelia cornuta_, that is to say, that an alternate
generation comes between these fungi. They appertain in consequence
to a single species, and the _Gymnosporangium_ ceased to be an
independent species, and must be considered as synonymous with the
first generation of _Roestelia_. The spores have been transported
upon young shoots of the juniper-tree, and have now commenced to
produce some mycelium in the bark. There is no doubt that in next
spring it will result in _Gymnosporangium_."
Subsequently the same learned professor instituted similar experiments
upon other hosts, with the spores of _Podisoma_, and from thence he
concluded that _Roestelia_ and _Podisoma_, in all their known species,
were but forms the one of the other. Hitherto we are not aware that
these results have been confirmed, or that the sowing of the spores of
_Roestelia_ on juniper resulted in _Podisoma_. Such experiments should
be received always with care, and not too hastily accepted in their
apparent results as proven facts. Who shall say that _Roestelia_ would
not have appeared on _Sorbus_ within two months without the sowing of
_Podisoma_ spores?--because it is not by any means uncommon for that
fungus to appear upon that plant. It is true many mycologists write
and speak of _Roestelia_ and _Podisoma_ (or _Gymnosporangium_) as
identical; but, as we think, without the evidence being so complete as
to be beyond suspicion. It is, nevertheless, a curious fact that in
Europe the number of species of _Roestelia_ and _Podisoma_ are equal,
if one species be excluded, which is certainly not a good _Podisoma_,
for the reception of which a new genus has been proposed.[e]
Amongst the ascigerous fungi will be found a curious but interesting
genus formerly called _Cordyceps_, but for which Tulasne, in
consequence of the discovery of secondary forms of fruit, has
substituted that of _Torrubia_.[f] These curious fungi partake more
or less of a clavate form, and are parasitic on insects. The pupæ
of moths are sometimes seen bearing upon them the white branched
mould, something like a _Clavaria_ in appearance, to which the name of
_Isaria farinosa_ has been given. According to Tulasne, this is the
conidia form of the bright scarlet, club-shaped body which is also
found on dead pupæ, called _Torrubia militaris_. An American mould of
the same genus, _Isaria sphingum_, found on mature moths,[g] is in
like manner declared to be the conidia of _Torrubia sphingum_;
whereas a similar mould, found on dead spiders, called _Isaria
arachnophila_,[h] is probably of a similar nature. An allied kind
of compact mould, which is parasitic on _Cocci_, on the bark of
trees, recently found in England by Mr. C. E. Broome, and named
_Microcera coccophila_,[i] is said by Tulasne to be a condition of
_Sphærostilbe_, and it is intimated that other productions of a
similar character bear like relations to other sphæriaceous fungi.
For many species of _Torrubia_ no corresponding conidia are yet
known.
Some instances might be noted, not without interest, in which the
facts of dimorphism or polymorphism have not been satisfactorily
proved, but final judgment is held in suspense until suspicion is
replaced by conviction. Some years since, a quantity of dead box
leaves were collected, on which flourished at the time a mould named
_Penicillium roseum_. This mould has a roseate tint, and occurs in
patches on the dead leaves lying upon the ground; the threads are
erect and branched above, bearing chains of oblong, somewhat
spindle-shaped spores, or, perhaps more accurately, conidia. When
collected, these leaves were examined, and nothing was observed or
noted upon them except this _Penicillium_. After some time, certainly
between two and three years, during which period the box remained
undisturbed, circumstances led to the examination again of one or two
of the leaves, and afterwards of the greater number of them, when the
patches of _Penicillium_ were found to be intermixed with another
mould of a higher development, and far different character. This
mould, or rather _Mucor_, consists of erect branching threads, many of
the branches terminating in a delicate globose, glassy head, or
sporangium, containing numerous very minute subglobose sporidia. This
species was named _Mucor hyalinus_.[j] The habit is very much like
that of the _Penicillium_, but without any roseate tint. It is almost
certain that the _Mucor_ could not have been present when the
_Penicillium_ was examined, and the leaves on which it had grown were
enclosed in the tin box, but that the _Mucor_ afterwards appeared on
the same leaves, sometimes from the same patches, and, as it would
appear, from the same mycelium. The great difference in the two
species lies in the fructification. In the _Penicillium_, the spores
are naked, and in moniliform threads; whilst in _Mucor_ the spores are
enclosed within globose membraneous heads or sporangia. Scarcely can
we doubt that the _Mucor_ alluded to above, found thus intermixed,
under peculiar circumstances, with _Penicillium roseum_, is no other
than the higher and more complete form of that species, and that the
_Penicillium_ is only its conidiiferous state. The presumption in this
case is strong, and not so open to suspicion as it would be did not
analogy render it so extremely probable that such is the case, apart
from the fact of both forms springing from the same mass of mycelium.
In such minute and delicate structures it is very difficult to
manipulate the specimens so as to arrive at positive evidence. If a
filament of mycelium could be isolated successfully, and a fertile
thread, bearing the fruit of each form, could be traced from the same
individual mycelium thread, the evidence would be conclusive. In
default of such conclusive evidence, we are compelled to rest with
assumption until further researches enable us to record the assumption
as fact.[k]
Apropos of this very connection of _Penicillium_ with _Mucor_, a
similar suspicion attaches to an instance noted by a wholly
disinterested observer to this effect. "On a preparation preserved in
a moist chamber, on the third day a white speck was seen on the
surface, consisting of innumerable 'yeast' cells, with some filaments,
branching in all directions. On the fourth day tufts of _Penicillium_,
had developed two varieties--_P. glaucum_ and _P. viride_. This
continued until the ninth day, when a few of the filaments springing
up in the midst of the _Penicillium_ were tipped with a dewdrop-like
dilatation, excessively delicate--a mere distended pellicle. In some
cases they seemed to be derived from the same filament as others
bearing the ordinary branching spores of _Penicillium_, but of this I
could not be positive. This kind of fructification increased rapidly,
and on the fourteenth day spores had undoubtedly developed within the
pellicle, just as had been observed in a previous cultivation,
precisely similar revolving movements being also manifested."[l]
Although we have here another instance of _Mucor_ and _Penicillium_
growing in contact, the evidence is insufficient to warrant more than
a suspicion of their identity, inasmuch as the equally minute spores
of _Mucor_ and _Penicillium_ might have mingled, and each producing
its kind, no relationship whatever have existed between them, except
their development from the same matrix.
Another case of association--for the evidence does not proceed
further--was recorded by us, in which a dark-coloured species of
_Penicillium_ was closely associated with what we now believe to be a
species of _Macrosporium_--but then designated a _Sporidesmium_--and a
minute _Sphæria_ growing in succession on damp wall-paper. Association
is all that the _facts_ warrant us in calling it.
We cannot forbear alluding to one of the species of _Sphæria_ to which
Tulasne[m] attributes a variety of forms of fruit, and we do so here
because we think that a circumstance so extraordinary should be
confirmed before it is accepted as absolutely true. This refers to the
common _Sphæria_ found on herbaceous plants, known as _Sphæria_
(_Pleospora_) _herbarum_. First of all the very common mould called
_Cladosporium herbarum_ is constituted as conidia, and of this again
_Macrosporium sarcinula_, Berk., is considered to be another
condition. In the next place, _Cytispora orbicularis_, Berk., and
_Phoma herbarum_, West., are regarded as pycnidia, enclosing
stylospores. Then _Alternaria tenuis_, Pr.,[n] which is said to be
parasitic on _Cladosporium herbarum_, is held to be only a form of
that species, so that here we have (including the _perithecia_) no
less than six forms or phases for the same fungus. As _Macrosporium
Cheiranthi_, Pr., often is found in company with _Cladosporium
herbarum_, that is also open to suspicion.
We have adduced in the foregoing pages a few instances which will
serve to illustrate the polymorphism of fungi. Some of these it will
be observed are accepted as beyond doubt, occurring as they do in
intimate relationship with each other. Others are considered as
scarcely so well established, but probable, although developed
sometimes on different species of plants. Finally, some are regarded
as hitherto not satisfactorily proved, or, it may be, only suspicious.
In this latter group, however much probability may be in their favour,
it can hardly be deemed philosophical to accept them on such slender
evidence as in some cases alone is afforded. It would not have been
difficult to have extended the latter group considerably by the
addition of instances enumerated by various mycologists in their works
without any explanation of the data upon which their conclusions have
been founded. In fact, altogether this chapter must be accepted as
illustrative and suggestive, but by no means as exhaustive.
[A] De Bary, in "Quarterly German Magazine" (1872), p. 197.
[B] The method pursued by Messrs. Berkeley and Hoffmann of
surrounding the drop of fluid, in which a definite number of
spores or yeast globules had been placed, with a pellicle of
air, into which the germinating threads might pass and
fructify, is perhaps the most satisfactory that has been
adopted, though it requires nice manipulation. If carefully
managed, the result is irrefragable, though doubts have been
cast, without any reason, on their observations.
[C] De Bary, "Uber die Brandpilze" (Berlin, 1853), pl. iv. figs. 3,
4, 5.
[D] A. de Bary, on Mildew and Fermentation, in "Quarterly German
Magazine," vol. ii. 1872.
[E] Berkeley, "Introd. Crypt. Bot." p. 78, fig. 20.
[F] See also Berkeley, in "Trans. Hort. Soc. London," vol. ix. p.
68.
[G] Berkeley, in "Ann. Nat. Hist." (June, 1838), No. 116.
[H] "Grevillea," vol. i. p. 176.
[I] Tulasne, "On Certain Fungicolous Sphæriæ," in "Ann. des Sci.
Nat." 4^me sér. xiii. (1860), p. 5.
[J] "A Currant Twig, and Something on it," in "Gardener's Chronicle,"
January 28, 1871.
[K] Figs. 104 to 106 by permission from the "Gardener's Chronicle."
[L] Berkeley and Broome, in "Annals of Natural History" (1866), No.
1177, pl. v. fig. 36; Cooke, "Handbook," ii. p. 866.
[M] Cooke, "Handbook," ii. p. 853, No. 2549; specimens in Cooke's
"Fungi Britannici Exsiccati," No. 270.
[N] Berk. and Br. "Ann. Nat. Hist." (1865), No. 1096.
[O] "Ann. Nat. Hist." (1871), No. 1332, pl. xx. fig. 23.
[P] Ibid. No. 1333, pl. xxi. fig. 24.
[Q] Tulasne, "Selecta Fungorum Carpologia," ii. p. 269, pl. 29.
[R] Cooke, "Handbook," ii. p. 878; Tulasne, "Carpologia," ii. p. 120,
plate 14.
[S] Tulasne, "Selecta Fung. Carp.," ii. plate 16.
[T] Corda, "Icones Fungorum," vol. iii. fig. 91.
[U] Corda, "Icones," vol. i. fig. 25.
[V] Berk. and Br. "Ann. Nat. Hist." No. 415.
[W] Currey, in "Philosoph. Trans. Roy. Soc." (1857), pl. 25.
[X] Tulasne, "On the Reproductive Apparatus of Fungi," in "Comptes
Rendus" (1852), p. 841; and Tulasne, "Selecta Fungorum
Carpologia," vol. iii.
[Y] "Monatsbericht der Koniglichen Preuss, Acad. der Wissenschaften
au Berlin," Jan. 1865; Summary, in "Journ. Roy. Hort. Soc.,
London," vol. i. n.s. p. 107.
[Z] We have before us an _Æcidium_ on leaves of _Berberis vulgaris_,
collected at Berne by Shuttleworth in 1833. It is named by him
_Æcidium graveolens_, and differs in the following particulars
from _Æcidium berberidis_. The peridia are scattered as in _Æ.
Epilobii_, and not collected in clusters. They are not so much
elongated. The cells are larger, and the orange spores nearly
twice the diameter. There is a decided, strong, but unpleasant
odour in the fresh plant; hence the name. The above figures
(figs. 107, 108) of the cells and spores of both species are
drawn by camera lucida to the same scale--380 diameters.
[a] Freiherrn von Hohenbühel-Heufler, in "Oesterr. Botan.
Zeitschrift," No. 3, 1870.
[b] Fuckel, "Symbolæ Mycologicæ" (1869), p. 49.
[c] Almost simultaneously with De Bary, the late Professor Oersted
instituted experiments, from which the same results ensued, as
to _Æcidium berberidis_ and _Puccinia graminis_. See "Journ.
Hort. Soc. Lond." new ser. i., p. 85.
[d] "Oversigt over det Kon. Danske Videns. Selskabs" (1866), p. 185,
t. 3, 4; (1867,) p. 208, t. 3, 4; "Résumé du Bulletin de la
Soc. Roy. Danoise des Sciences" (1866), p. 15; (1867), p. 38;
"Botanische Zeitung" (1867), p. 104; "Quekett Microscopical
Club Journal," vol. ii. p. 260.
[e] This is _Podisoma foliicola_, B. and Br., or, as proposed in
"Journ. Quekett Club," ii. p. 267, _Sarcostroma Berkeleyi_, C.
[f] Tulasne, "Selecta Fungorum Carpologia," iii. p. 6, pl. i. figs.
19-31.
[g] Cramer's "Papilio Exotic" (1782), fig. 267.
[h] Cooke, "Handbook," p. 548, No. 1639.
[i] Ibid. p. 556, No. 1666.
[j] Specimens were published under this name in Cooke's "Fungi
Britannici Exsiccati," No. 359.
[k] Cooke, "On Polymorphism in Fungi," in "Popular Science Review."
[l] Lewis's "Report on Microscopic Objects found in Cholera
Evacuations," Calcutta, 1870.
[m] Tulasne, "Selecta Fungorum Carpologia," ii. p. 261.
[n] Corda, "Prachtflora," plate vii.
X.
INFLUENCES AND EFFECTS.
It is no longer doubted that fungi exercise a large and very important
influence in the economy of nature. It may be that in some directions
these influences are exaggerated; but it is certain that on the whole
their influence is far more important for evil and for good than that
of any other of the Cryptogamia. In our endeavour to estimate the
character and extent of these influences it will prove advantageous to
examine them under three sections. 1. Their influence on man. 2. Their
influence on lower animals. 3. Their influence on vegetation. Under
these sections the chief facts may be grouped, and some approximate
idea obtained of the very great importance of this family of inferior
plants, and consequently the advisability of pursuing their study more
thoroughly and nationally than has hitherto been done.
I. In estimating the influence of fungi upon man, we naturally enough
seek in the first instance to know what baneful effects they are
capable of producing on food. Although in the case of "poisonous
fungi," popularly understood, fungi may be the passive agents, yet
they cannot be ignored in an inquiry of this nature. Writing of the
Uses of Fungi, we have already shown that a large number are available
for food, and some of these real delicacies; so, on the other hand, it
becomes imperative, even with stronger emphasis, to declare that many
are poisonous, and some of them virulently so. It is not sufficient to
say that they are perfectly harmless until voluntarily introduced into
the human system, whilst it is well known that accidents are always
possible, and probably would be if every baneful fungus had the word
POISON inscribed in capitals on its pileus.
The inquiry is constantly being made as to what plain rules can be
given for distinguishing poisonous from edible fungi, and we can
answer only that there are none other than those which apply to
flowering plants. How can aconite, henbane, oenanthe, stramonium,
and such plants, be distinguished from parsley, sorrel, watercress,
or spinach? Manifestly not by any general characters, but by
specific differences. And so it is with the fungi. We must learn to
discriminate _Agaricus muscarius_ from _Agaricus rubescens_, in the
same manner as we would discriminate parsley from _Æthusa cynapium_.
Indeed, fungi have an advantage in this respect, since one or two
general cautions can be given, when none such are applicable for
higher plants. For instance, it may be said truly that all fungi
that exhibit a rapid change to blue when bruised or broken should
be avoided; that all Agarics are open to suspicion which possess an
acrid taste; that fungi found growing on wood should not be eaten
unless the species is well known; that no species of edible fungus
has a strong, unpleasant odour, and similar cautions, which, after
all, are insufficient. The only safe guide lies in mastering, one by
one, the specific distinctions, and increasing the number of one's
own esculents gradually, by dint of knowledge and experience, even as
a child learns to distinguish a filbert from an acorn, or with
wider experience will thrust in his mouth a leaf of _Oxalis_ and
reject that of the white clover.