The Brand-Fungi (also known as USTILAGINEÆ) are Fungi with
_basidia-like conidiophores_, which, however, have not yet advanced
to a definite form or number of conidia. They are true parasites,
whose mycelium spreads itself in the intercellular spaces of Flowering
plants. The mycelium is colourless, quickly perishable, has transverse
walls at some distance from each other (Fig. 96), and sends out
haustoria into the cells of the host-plant.
[Illustration: FIG. 96.--_Entyloma ranunculi._ 1. Cross section
of a portion of a leaf of _Ficaria_ permeated by the mycelium; a
bundle of hyphæ with conidia emerging from a stoma; in one of the
cells are found four brand-spores. 2. A brand-spore developed in
the middle of a hypha.]
It most frequently happens that the germ-tube enters the host-plant at
its most tender age, that is, during the germination of the seed; the
mycelium then wanders about in the tissues of the shoot during its
growth, until it reaches that part of the plant where the spores are to
be formed. The spore-formation takes place in the same way in all those
species whose brand-spores are developed in the floral parts of the
host-plant. Many Brand-Fungi have, however, a more local occurrence,
and the mycelium is restricted to a smaller area of the leaf or stem.
Those organs of the host-plant in which the brand-spores are developed
often become strongly hypertrophied. In perennial plants the mycelium
winters very often in the rhizome.
[Illustration: FIG. 97.--_Doassansia alismatis._ 1. A fruit-body,
formed by a covering of oblong hyphæ, which encloses a mass
of brand-spores, and is embedded in the leaf-tissue of the
host-plant; 20 times natural size. 2. A germinating brand-spore,
500 times natural size. 3. Three connected resting-spores, 400
times natural size. 4. Two conidia grown together, 600 times
natural size.]
The brand-spores are the winter resting-spores of the Brand-Fungi.
They arise in the tissues of the host-plant, which is often destroyed,
and become free through the rupture of the epidermis; they are
thick-walled, generally brown or violet, and very often possess warts,
spines, or reticulate markings. Fruit-bodies, that is enclosed organs
of reproduction, are found in few genera (_Sphacelotheca_, _Graphiola_;
_Doassansia_, Fig. 97). In _Tolyposporium_, _Tuburcinia_, _Thecaphora_
(Fig. 102), etc., the brand-spores are united into a _ball of spores_.
On germination the brand-spores behave as _chlamydospores_, namely,
as the fundament of conidiophores, by emitting a short germ-tube,
_i.e._ a conidiophore (“promycelium”). The USTILAGINACEÆ (Fig. 99, 2)
have a short _transversely divided_ conidiophore, with _laterally_
developed conidia (comp. the basidia of the Protobasidiomycetes).
The conidiophores of the TILLETIACEÆ are undivided (unicellular
promycelia), and bear the conidia terminally, and so resemble the
basidia of the Autobasidiomycetes.
[Illustration: FIG. 98.--_Tuburcinia._ 1. _T. trientalis._ Hyphæ,
some of which bear conidia at the apex, forcing themselves out
between the epidermal cells on the under side of the leaf; 320
times natural size. 2. _T. trientalis._ A ball of spores in which
some of the individual brand-spores are about to germinate; 520
times natural size. 3. _T. primulicola_: various forms of conidia
(500 times natural size).]
In _Tilletia_, _Entyloma_, _Neovossia_, _Tuburcinia_, the
brand-spores germinate and form basidia-like conidiophores with
spindle-shaped conidia; their mycelium, on the other hand,
produces later only single, sickle-shaped conidia, so that
two kinds of conidia are found, as in a few Basidiomycetes.
In some species, _e.g. Ustilago hordei_, the brand-spores
only germinate vegetatively and form a mycelium. In nutritive
solutions (solutions of dung, etc.) where they live as
_saprophytes_, the brand-spores of many species emit germ-tubes,
and on these, _yeast-like conidia_ are produced by repeated
budding, which grow into mycelia only when the nutritive
solution is exhausted. These conidia have not the power of
producing alcoholic fermentation. The very numerous conidia,
which are found in the dung of herbivorous animals, are probably
the yeast-conidia of Brand-Fungi. The brand-spores, which are
eaten by animals with the grain and hay, pass into the dung
and without doubt give rise to a very rich multiplication of
yeast-conidia.
[Illustration: FIG. 99.--_Ustilago._ 1. Formation of
brand-spores. 2. Germinating brand-spore of _U. perennans_.
3. Germinating brand-spore of _U. cardui_ (after Brefeld). 4.
_U. filiformis. a_ A brand-spore with developed basidium;
_b_ another, with a conidium; _c_ with two conidia; _d_ with
two conidia placed diametrically opposite to each other; _e_,
detached conidia which are growing into hyphæ.]
[Illustration: FIG. 100.--_Tilletia tritici_: _a_ an ear of
Wheat in which all the grains are attacked by Stinkbrand;
_b_ a blighted corn surrounded by the chaff; _c_ a blighted
corn grown together with a stamen; _d_ the same cut across;
_e_ a brand-spore; _f_, _g_, _h_ germinating brand-spores;
_i_ germinating conidia; _j_ the mycelium; _k_-_k_
brand-spore-forming mycelium-threads. (_c-h_ magnified 400 times;
_i-k_ 300 times.)]
The conidia (also called “sporidia”) of many species unite
generally into an H-form (Figs. 97, 4; 100 h; 101, 4). This
union in pairs does not, however, take place with a view to
germination, there is no fusion of nuclei, and therefore in this
“fusion” there is no sexual act.
Order 1. =Ustilaginaceæ.= Conidiophores with transverse walls
and lateral conidia.--_Ustilago_ (Fig. 99) generally developes
its spores in the floral organs of its host-plant, the ovary or
anthers, where they arise from hyphæ, and form a slimy mass
which when mature becomes a black dust.
To this order belong _U. avenæ_, parasitic on Oats, _U. hordei_
and _U. nuda_ (_U. jenseni_), on Barley; these are the usual
cause of “Smut” on cereals. _U. hypodytes_ on straw of _Elymus_
and _Agropyrum_. _U. filiformis_ in the leaves of _Glyceria_.
_U. caricis_ transforms the fruits of various species of
_Carex_ into black, dusty balls. _U. violacea_ developes its
violet spore-powder in the anthers of the Caryophyllaceæ.
_U. tragopogonis_, transforms entire inflorescences of
_Tragopogon_ into a black-violet mass. Among the largest are _U.
grandis_, which causes the large swollen nodes in the stem of
_Phragmites_, and the Maize Blight, _U. maydis_, which produces
outgrowths about the size of a hand on the spadix of the Maize.
Order 2. =Tilletiaceæ.= Conidiophores undivided, generally
several conidia arise at their apices.--_Tilletia tritici_,
the _Stinkbrand on Wheat_ (Fig. 100). The mycelium lives in
Wheat-plants, producing its spores in the ovary after the whole
interior of this body has been destroyed by the mycelium, with
the exception of the external layer of the wall of the ovary,
which remains essentially unaltered and encloses the closely
packed, firm mass of spores (Fig. 100 _d_). The grains of Wheat
thus attacked are shorter and thicker than the sound ones,
and the ears show the presence of this Fungus by their erect
position, and the wide separation of the chaff (Fig. 100 _a_).
The unpleasant odour of the ovary prior to the ripening of the
spores, has given the name “Stinkbrand,” and, in like manner,
its hardness when it encloses the ripe spores, is the reason
of its being also called “Stonebrand.” On account of this
hardness, the diseased grains are readily harvested together
with the healthy ones, which become infected by the spores at
the threshing. _T. lævis_ (_T. fœtens_) also occurs on Wheat and
has smooth brand-spores.
[Illustration: FIG. 101.--_Urocystis._ 1, _U. covalloides_.
A spore-ball, magnified 450 times. 2–4, _U. anemones_: 2–3,
brand-spores which are about to germinate (magnified 450 times).
4, Conidia, the two in a state of fusion, a third with vacuoles
and division-wall, magnified 500 times.]
_Entyloma_ (Fig. 96), a genus with numerous species, which
appear in spots on the leaves of the host-plant, and
_Tuburcinia_ (Fig. 98), which makes its appearance on the
Primulaceæ, produce white conidia-spots on the surface of the
host-plant. The first-named has single spores, the latter has
its spores closely massed together.--_Urocystis_ (Fig. 101)
has its spores surrounded by a number of small and lighter
coloured barren spores. _U. occulta_, Rye-stem Blight, forms
its spores in long streaks in the stems and leaves of the Rye,
and does considerable damage. _U. cepulæ_ on Onions. _U. violæ_
forms large dark-violet swellings in the leaf-stalk and stems
of Violets.--_Thecaphora_ (Fig. 102) appears in seedlings of
_Convolvulus_ and _Astragalus_.
As a means of protection against the Smut-Fungi which make their
appearance on the different cereals, a submersion of the grains
in a solution of blue vitriol (½%) for twelve hours, or better
still, submerging for five minutes in water heated to 53–55° _C_
(Jensen’s method) is employed.
[Illustration: FIG. 102.--_Thecaphora._ 1, _T. convolvuli_, a
ball of spores, one of the brand-spores has emitted a septate
branched conidiophore (× 520). 2, _T. affinis_, a ball of spores
(× 520).]