VUILLEMIN, P. 1891. Sur les effets du parasitisme de l'Ustilago antherarum. Comptes
Rendus, Paris 113: 662-665.
Translation of Paul Vuillemin
Botany. – On the effect of parasitism by Ustilago antherarum.
Note by Paul Vuillemin, presented by Duchartre.
It is known that the female flowers of Lychnis dioica, when invaded by Ustilago
antherarum, take on the appearance of hermaphroditic flowers. This curious phenomenon
has been described by Mr. Tulasne, Miss Becker, Mssrs. Cornu, Hoffman, Giard,
Magnin, etc. Using the nomenclature of Giard, it is an example of androgynous parasitic
castration.
The castration is indeed real; because the development of the pistil is stopped at a
stage corresponding to a length of 5-6 mm as measured on the calyx in normal flowers.
It has nevertheless been suggested that, in spite of the atrophy of the styles and the
absence of the stigmatic papillae, the parasitized flowers are often fertilized. This
supposition is based on the presence of ripe capsules, full of apparently good seeds, on
plants infected by Ustilago (Footnote 1: Magnin, Comptes rendus, 22 October 1888) and
on the generally accepted idea that no flower escapes the action of the parasite in infected
individuals. Mr. Roze already expressed some doubts on the subject of the accuracy of
this latter hypothesis, following the observation of a female stem in which one branch
carried exclusively infected flowers with a rudimentary ovary, while another branch was
loaded with ripe fruits. This idea hinges on the discovery of female stems that sometimes
carry flowers infected by Ustilago and flowers that are absolutely unaffected. I have been
able to establish that this is frequently the case. Beside an infected branch, one finds
another where the flowers are of the female type, at all stages subsequent to the rudiments
of half a millimeter just after anthesis. One stem in which the base was healthy and its
inferior branches free from the parasite, had all the flowers of the cyme invaded. In
another, the attack was limited to several branchlets, in between which the stem produced
healthy branches. It is thus certain that the disease can be local so that in the flowers
where the parasite is not directly observed, it is not possible to say that it has been there,
Angrogyny has been considered more worthy of attention than the ovary
castration. Mr. Magnin has just said “The flowers of Lychnis, which appear
hermaphroditic, are really that”. We have just seen what needs to be thought about the
fertility of partial females. That of the stamens is no less illusory.
One knows that the female flowers have a rudimentary androecium. Mr. Van
Tieghen himself showed, twenty years ago that these primordia are vascularized like the
stamens of male flowers. Since that period, their presence has not been appreciated. This
is also true for their very variable length. On the flowers of a single type (macrostyles,
for example) one finds at times anthers that are sessile, reduced at the time of anthesis, up
to the point where they are nearly imperceptible, at other times a hair-like thread reaching
1 mm and surmounted by a quite distinct anther. In very young flowers, the stamens are
much more uniform and do not differ in any way from the primordial of male flowers.
However, the pollen sacs do not form. One sometimes sees in their place large cells that
enclose a complicated deposit of calcium oxalate.
Under the influence of parasitic stimulation, these preexisting primordia
hypertrophy; the mycelium invades in the part corresponding to the pollen sacs; the
nuclei, visible in the mass for some time, disappear and the anthers in a flower of about 4
mm enclose four sporogenous clusters. The first action of the parasite, far from creating
the male elements, consists of destroying the cells destined to produce the pollen.
From the time the fungus substitutes itself for the pollen the anther partitioning
wall is reduced, as in male flowers of the same age, at the epidermis and at the base of the
outer cortex, under which nuclei of the flattened medial base are visible for quite a long
time. From this moment, the parasite and the anther sacs [‘paroi’ = cavity??] harmonize
their development by a kind of symbiosis analogous to what is found in galls, and still
more clearly in the parasitized fruits of the Vaccinias in which a Sclerotinia has replaced
the ovules; but there no example involving the stamens has been studied. Its anther sacs
increase in size as does Ustilago; the spiral ornaments [les ‘ornenments spirales’ – not
sure what these are!!] can be seen regularly in the base of the outer cortex and even in
some of the epidermal cells; the spores are formed a little later and are disseminated at
maturity by a dehiscence that is identical to that which frees the pollen. The filaments are
increased at the same time as the anther sacs.
Thus the parasite makes the rudiments of the stamens more apparent by
hypertrophying them. Its stimulating effect, acting in the same manner as that of the
normal components of the fertile stamens, reawakens in the female flower latent
tendencies which are manifested by the differentiation of the accessory characters of the
androecium. The compensatory inhibition that affects the development of the pistil
permits movable material to flow towards the location chosen by the parasite. In reality,
this male appearance is appropriated exclusively for the use of the parasite; the sex that is
normally absent is not represented any better in the parasitized flowers than in the
ordinary female flowers. Far from being truly hermaphroditic the flower invaded by
Ustilago is thus sterilized. The localization of the spores in place of the pollen allows
Ustilago to be dispersed by the normal agents of cross-fertilization. On an isolated and
perfectly healthy female stem, I have found the stigmas covered with spores of Ustilago
that were germinating on the stigmatic papillae. The sporidia that invade the ovary, the
durable spores that are disseminated with the seeds will easily infect the seedlings
[‘plantules’ = seedlings or embryo]. Moreover the spores carried by insects can land not
only on the stigmas but also on the young buds. They thereof ere result in partial
infections that appear to be as frequent as generalized attacks. These latter suppositions,
suggested by the preceding observations, can be tested experimentally. I have gathered
material necessary to carry out these experiments in the next season.
From Anon. 1892. Index to Literature. The Journal of Mycology 7:
153-194.
Entry 378., page 158.
3 7 . VUILLEMIN, PAUL. Sur les effets du parasitisme de l'Ustilago antherarum. Comptes Rendus, vol. 113, Paris, Nov.
9, 1891, pp. 662-665. It is well known that the pistillate flowers of Lychnis dioica take the appearance of hermaphrodites when
invaded by this fungus. It was formerly supposed that when any flowers of a plant were attacked all were. The author shows
that such is not the case. The flowers of a single branch may be invaded, while those of a neighboring one may escape. The
base and lower branches may escape, while all the flowers in the top of the plant are affected. In other cases some small
branches may be affected, among which the stem pushes out sound branches. Such partial attacks are common. The action of
the para-site stimulates the development of the normally abortive stamens and the smut spores take the place of pollen grains
and escape, and are distributed in the same way. The author thinks there is a symbiosis analogous to that in galls. He has
found the stigmas of isolated and healthy plants powdered with spores of Ustilago, which he believes were transplanted from
infected plants by visiting insects. (E. F. S.) (See also Nos. 379, 381, 428, 432, 443, and 450.)