48 
the comet’s orbit to an earlier date in November, is now 
fully corroborated by the conspicuous appearance of the 
same meteor-shower which has recently appeared. Had it, 
indeed, been possible to estimate exactly the motion of 
the comet’s nodes during the interval since their pre- 
vious return, the date on which the great meteor-shower 
observed on Wednesday last occurred, might have been 
accurately foretold. The Luminous Meteor Com- 
mittee of the British Association requested observers 
to co-operate for its observation on the evenings of the 
28th to 3oth of last month, and to keep an occasional 
watch for its return from the 25th until the last day of 
November. The observations received from some of 
these observers are ample proofs of their success ; and 
among the copious descriptions of the shower which have 
appeared by many expert astronomers throughout the 
kingdom, little can be desired to increase the extent or 
accuracy of the information which has been obtained. 
Should it, however, be observed that a star shower like 
that seen by Heis, and earlier observed on the 6th and 
7th of December, is again visible on about the 5th of 
December in this year, its connection with the companion 
NATURE 
comet I., 1818, of Biela’s comet, may become a matter of 
interesting deductions from such observations, and of 
further satisfactory investigations. 
A. S. HERSCHEL 
FERMENTATION AND PUTREFACTION* 
II. 
N the interesting inquiry into the life-history of mildews, 
a well-known one, abundant wherever organic matter, 
in a somewhat inert state, is exposed to damp, Asferge/lus 
glaucus, may be taken as wellas the Mucor mucedo. This 
consists in the first place of a mass of mycelium fila- 
ments, which are formed of delicate cells in chains, that 
is to say, the fibres are divided into series of true cells 
by diaphragms. The cells are full of protoplasm, at 
first showing a distinct nucleus, and afterwards a num- 
ber of vacuoles containing water. The filaments grow 
at the ends, and new partitions there grow up—at 
first close together, and afterwards separating and becoming 
more distinct. Some of the filaments become spiral at 
the end and finally develop peculiar reproductive organs 
which will be noticed presently. <Asfergil/us frequently 
presents for long nothing but this spreading jointed myce- 
lium, feeding upon the surface, and penetrating into the 
substance of organic matter, and rotting and burning it; 
producing water, carbon dioxide, sulphuretted hydrogen, 
yarious butyric compounds, and other products of decom- 
position, without developing any special organs of its 
own. In this state it is perfectly impossible to distinguish 
it from the mycelium of many other fungi. No doubt there 
are differences—there are marked differences from some 
mycelia, for instance those of the Mucors where the filaments 
are undivided—but most have divided filaments, and these 
organs are so small, so simple, and so variable, that itis next 
to impossible to appreciate the distinctive characters, 
Under favourable circumstances, in the light and air, 
Aspergillus rises into the form of a bluish mould. This 
under the microscope shows a multitude of one-celled 
upright stalks, which form a kind of fur on the surface 
to the Botanical 
* From the Opening Address for the Session 1872-7 
yville Thomson, 
Society of Edinburgh, delivered on Nov. 14, by Prof. 
F.RS., President of the Society. Concluded from p. 62. 
| Dec. ei 1872 
which it has attacked. Each of these stalks, which — 
may be called conidia-stems, is dilated at the upper — 
end, and from this dilatation there project, bristling 
all over the knob, a number of conical protuberances — 
called sterigmata. Each sterigma becomes pointed — 
towards its free end, and at length produces at the — 
point a small round cell filled with protoplasm, which © 
remains attached to the sterigma bya fine pedicel. Behind 
this cell, between it and the end of the sterigma, another 
cell then forms, and then another, until little chains of cells — 
stand out free from the ends of the sterigmata ; and as 
all these are of the same age, they are symmetrical, and ; 
of the same length. The farthest from the sterigmata 
are, of course, the oldest, and some of these soon get dry 
and ripe ; so that an impalpable dust of these propagating — 
buds or conidia is perpetually coming off, wafted by the — 
slightest breath, or even by the imperceptible convection- — 
currents from which the air is never free, from the surface — 
of a mould patch. The conidia are buds capable of ger- 
mination, of producing plants which go through the same 
course astheir parent, but they arenot reproductiveproducts. 
At the ends of the spiral curls of the mycelium filaments — 
at certain seasons, and under favourable circumstances, 
large bodies are produced by a form of conjugation in 
which cells are multiplied till they form a mass of con- 
siderable size of a bright yellow colour, called a wévicle. 
Some of the cells composing the utricle become dissolved, 
while the greater number are developed into oval sacs 
or asci, in each of which eight spores are produced, 
These utricles are the true sexual reproductive organs. 
We have thus two kinds of spores—conidia, which are 
non-sexual buds, and asci-spores, the product of a form — 
of sexual union. Asferg7/lus often bears conidia without 
utricles, and this is always the case when the fungus is 
badly nourished. It never, apparently, bears utricles | 
without conidia, The appearance of the two modes of 
reproduction is so different, that the name Aspergillus was, p 
until lately,restricted to mycelium bearing the conidia form — 
of multiplication, while the utricle-bearing filaments and 
utricles were placed in another genus, Aurotzum. , 
When sown, say on a solution of sugar or on any other 
suitable soil, the behaviour of the two kinds of spores is” 
exactly the same. ‘The spores send out tubes, which — 
take the character of mycelium ; and whose filaments in 
either case subsequently bear conidia or utricles according — 
to circumstances. 7 
Botrytis cinerea, a fungus specially abundant on decay- 
ing vine-leaves, produces conidia in elegant panicles, and 
a utricle which assumes such large proportions, and such — 
a definite form, that it has been placed in the great genus 
Pesiza, under the name of P. fuckeliana. y 
Not to multiply examples too much, I will briefly refer _ 
to a form, the life history of which is not yet thoroughly 
known—the mould which so often occurs in sour milk, — 
though itis by no means confined to that station— Oidium 
lactis. The mycelium of Ofdium is extremely like that of 
Aspergillus glaucus, having filaments divided into distinct — 
cells by marked septa. From the mycelium long single , 
shoots rise in the air, and give off chains of conidia a 
. . 7 ~ 
each shoot representing one of the sterigmata of Asfer- 
gillus with its progeny. Oédium attacks all kinds o 
