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plasmodia possess the power of passing into a temporary
sclerotioid or resting stage ; the preliminaries for this condition
are the breaking up of the protoplasm into innumerable roundish
or polyhedric cells with an average diameter of from 25—40 p.
In some species, as FtiUgo and Bidymium serpula, the cells
become surrounded by a distinct, colourless membrane, which
shows the reaction of cellulose with iodine and sulphuric acid or
with Schulze’s solution.
In the Acrasieae, the spores on germination give origin to
ameboid swarm-cells, ciliated cells never being produced ;
after undergoing repeated bipartitions, the swarm-cells form
dense masses, but although crowded together, do not coalesce ;
this crowding together without loss of individuality constitutes
what De Bary terms, aggregation of swarm-cells.
From the above account we learn that the coalescence of
naked, motile cells, or even the aggregation of naked motile
cells without loss of individuality, is, from De Bary’s standpoint,
the proof that the Myxogastres are not plants.
Naked or primordial cells are as a rule motile ; in fact a
considerable amount of motility is usually exhibited by protoplasm
when imprisoned in a cell-wall; "hence we may presume
that motility, being so general, is not an important factor in
the character that proves Myxogastres to be animals; in fact
De Bary admits that the differences between the Mycetozoa
and the Fungi “ would not be loss decided if the Mycetozoa wero
without their remarkable movements, for such movements are
observed in other vegetable cells which have not a firm
membrane.” The Aerasieae show that the coalescence, with
loss of individuality of the component cells, may be omitted
from the character that separates the Myxogastres from
plants; hence we find that the only point not neutralized
by De Bary’s own statements is that of naked cells; consequently
ive may, by following De Bary’s reasoning, formulate
the character that excludes the Myxogastres from the vegetable
kingdom as follows—Cells naked during the entire végétative
period.
Notwithstanding the fact that the above definition covers
the crucial point in De Bary’s characteristic work of separation,
which “ lies in the formation of plasmodia or aggregation of
swarm-cells,” it will bo well to treat individually, all the points
embodied in the original, commencing with the coalescence of
cells. This coalescence, and consequent loss of individuality
of cells to form a common mass of protoplasm capable of
spontaneous movement, is the leading characteristic of a
plasmodium ; but it is an undoubted fact that motility is to a
very considerable extent influenced by the presence or absence
of a cell-wall, or to the relative plasticity of the cell-wall when
present; and coalescence of protoplasm, even when cell-walls
intervene, is highly characteristic of fungi, and has received different
names depending on its supposed morphological or physiological
functions ; it is sufficient to name “ clamp-connections ”
characteristic of the vegetative hyphae of the Basidiomycetes ; and
the complex irregular network formed by the vegetative hyphae
of many of the forms included in the Hyphomycetes as being due
to the fusion of portions of protoplasm originally distinct. In
the above examples the component hyphae are septate ; but in
the Mueorioii, where the hyphae are entirely without septa,
there is a still nearer approach to a plasmodium.
In the last-named group, the spore on germination gives
origin to an intricately branched mycelium, the component
branches of which eventually form a dense, irregular network,
due to the numerous points at which coalescence of originally
distinct branches has taken place. If single spores, picked up
under a low magnifying power, on the point of a needle touched
with glycerine, are sown on glass slips in a thin smearing of
sterilized decoction of raisins, covered with large squares of thin
glass sterilized by passing through the flame of a spirit-lamp,
raised at one end by a strip of tracing-paper to prevent crushing
the spore, and at once sealed up with cement, it will be found
that in most cases, spores of the Hyphomyeetes or Phyeomycetes will
germinate at once, and continue to grow until a considerable
mass of mycelium is formed ; such preparations can be examined
at any moment under high powers without loss of time, and
the behaviour of the mycelium followed. A noteworthy feature