, 1891-11-28

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ing these gases were prepared and expert
ments made to illustrate the special charac-
~teristics of each. Oxygen, while not in it.
self indammable was proved to be the great
supporter of all combustion, "the spirit of
fame as it has been termed. Bits of glow
ing wood, magnesium tape. and iron wire
were separately plunged in jars of the gas
and produced striking phenomena of incan-
desence. The scintillations of the burning
iron wire were especially beautiful. although
not giving as dazzling a light as that yield
ed by the oxidation of magnesium. Hydro
gen, the lightest of all known substances
(abOut 14b times lighter than air. was next
exhibited, and the Inference between it and
oxygen pointed ont. Highly intammable. vet
Unable to support combustion, it burned at
the mouth Of an inverted jar containing the
gas, but quickly extlngulshed a lighted
match plunged into il, which, however, again
burst int flame on being withdrawn FROM
the jar. It's affinity, or liking, for oxygen
was shewn. and The two being brought to-
gether in the correct proportions and ignited
the reunion took place with All intensity
great enough to produce an explosion of
considerable force, water being produced
by the combustion.
The cellular structure of the leaf, root.
and stalk of the cane were next shewn on a.
mdSnIueu SCdIG ny Hl6dnS OI Gn6 lantern.
The difference of strength in construction
between the six-sided cells of the softer
tissues and the elongated cells of the bark
and inner bark, the beautiful arrangement
Of these in so-called spiral, ring shaped, and
dotted "veSSels,' the use of the stomata
and air spaces for afording a passage for
the admission of air to the interior of the
leaf, the process of Starch-making under the
chemical agency OF sun light were all clearly
explained by the speaker.
The tissues were comp red to a certain
building not unknown to some (i.e. prisons(
divided into compartments, and the ilAlivi-
dual cell with it's contents OF pr0toplasm,
with those other "cells" where the. occupant
was by day partly engaged in .Self-SuppOrt-
ing work de. starch maklng) as we'll as in
consuming the food thus made. For both
of them sunlight was among the necessities,
as in the dark no work could be done. From
protoplasm chIOrOphyl II or green GoloTing
matter was elaborated among other things,
and from this again starch the most import
ant food stuff OF plants was derived. With
out sunshine no starch, without starch no
food, without food no work, and consequent
~ no growth or production of sugar.
The above was shewn by the following
experiment =
Two sets OIL ayes ola growing plant, one
or Wnlcn nau been exc uded from sun
light for a few hours by simply putting a tin
over it, and the other exposed, were depriv-
ed of their green colour by sleeping in warm
alcohol the now colourIess leaves were
then dipped in a solution of Iodine, which as
is well known gives a deep blue tinge with
starch. The one leaf was stained a light
yellow only, the other nearly black very
deep blue) from the presence ofstarch, indi-
eating in the first case that none had been
produced on that day, aud also that what
was there before, had been eaten up.
Special attention was also given to two
things connected with the root first, the fact
of its being aspreading (6brous) one, made
it evident how necessary it was to put man.
ures between and not close up around the
plant where the toughened cells Of the root
tibres make absorption impossible. Secondly,
the importance of understanding the delicate
mechanism of the root-sheath which serves
to protect the growing point from injury
as it forces its way downwards, as we'll as
that of the root hairs which by the process
of osmosis or passing of crystallisable substan-
oes in a state of solution through a membrane,
enables the plant to extract from the soil
what it requires for nourishment and carry
1t further on by a similar process of diffusion
by means OF the sap to the cells of the stem
and whole plant. Paradoxioal as it may seem.
the practical lesson to be learnt from this os-
motto action of the root cap. was deem drainage