Huntsville gazette., 1885-06-27
THE YEAST PLANT.
Peculiarities of One of the Lowest Formf
of vegetable Life.


| Of Vegetable Life.
Yeast is substance which has long
been known by the power which it pos
sesses of exciting the process called
fermentation. Almost everybody is
familiar with the fact that in the pro-
cess of bread-making when yeast is
| added to mixture of -four and water
it causes it to ''raise," and that the
raising is attended with the production
of sour smell and the formation OF
bubbles of gas which escape from the
surface of the mixture in little puffs.
Now yeast has the power of awaken
ing this activity only by virtue of its
being living plant. When some of
| it is added to the mixture of flour and
water. the conditions of the growth OF
the plant are satisfied, it is able to get
the kind of food on which it lives, and
it is by its very rapid growth and null
tiplication that the fermenting process
is caused.
out into thin layer and placed under
the microscope, it will be found to con-
tain very many of these yeast plants.
Judging from their appearance, no
one unfamiliar with microscopic forms
of life would ever suspect them to be
plants. They are simply round or
oval transparent bodies, lying single or
associated in heaps or strings. They
are very small indeed, the largest be-
ing only about one-thouSandth
of an inch in diameter. Tx
aminingva single one of these
plants, it will be seen to consist OF
thin sac or bag. within which is con-
tanned more fluid part. In the mid
| die of the fluid sometimes small, clear
space appears, called the vacuole.
Nothing farther than this can be seen
at single examination, but If one OF
| the bodies be watched for some time, a
change in its appearance will be OBJ
served. 1t will be seen to give rise to
minute bud, which rapidly grows un-
til it has assumed the size of the parent.
1t may then detach itself, and in its
turn produce another bud, but usually
the second bud begins to grow before
the first has become detached, and in
this way the strings and heaps are
formed. Sometimes one of the plants
multiplies itself in another way. 1t
does not throw off bud, but the fluid
matter inside the sac divides into four
masses, and each of these having be-
come surrounded with a sac of its own.
the sac of the parent bursts open and
the four new plants are set free. Each
of these rapidly attains its full size, and
in its turn, either by budding or divi-
sion, gives rise to others.
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of the power of growth, are living or
ganisms, and the question arises
whether they are animals or plants.
That they belong to the plant king
dom is shown by their possession OF
two characters. In the first place, the
outer covering, or sac, contains the
substance cellulose, which is one
of the most characteristic con-
stituents of plants. Secondly, they
possess the power of living upon
Inorganic matter; they are able to sepa-
rate the flour and water into the chem
ical elements which compose them, and
out of these elements build up their
own bodies. Animals, on the other
hand, can live only upon organic mat
ter, that is, upon other animals and
plants. Yet there are two respects in
which the yeast plant differs from all
ordinary plants; it contains no green
coloring matter. or chlorophyl. and it
constantly throws off carbonic acid gas
and absorbs oxygen. In these partcu-
lars it is at one with the animals; but
as the two properties first mentioned
are of more fundamental nature than
the latter, yeast IS considered to belong
to the plant kingdom.
The vitality possessed by the yeast
plant is very remarkable. 1t is able to
keep alive in dry state for very long
time, probably many years. The con-
ditions required for its growth are heat,
moisture, and the presence of sugar, or
its chemical equivalent. AS soon as
these conditions are satisfied, it grows
and multiplies with great rapidity, so
that small quantity will in short
time produce an amount many thou
sands of times as great in bulk. 1t is
said, on good authority, that under
| favorable circumstances one plant
will produce one million in one day.
The growth of the plant is attended
with the formation of two bodies, car
bonic acid and alcohol. These sub
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the sugar contained in the matter in
which the yeast is placed. In the rails
ing of bread, the bubbles of gas formed
are carbonic acid gas, and the sour
smell generated is due to the forma-
ton of alcohol. In brewing, the grain
is first caused to sprout. this changing
its starch into sugar. The growing
process is then interfered with, and
yeast, the plant now being able to sub
sist on the sugar, is added, and fer
mentation ensues.
The yeast plant is one of the very
lowest forms of vegetable life. Like
the lowest animals, it consists of a
single simple cell. The material OF
which the cell is made, except as to the
cellulose sac, is just the same as that
of the lowest animals, viz, protoplasm.
The yeast plant is like the lower ami
mails, too, in the manner in which it
reproduces itself-by fssion and by
gemmation or budding. But it shows
its resemblance to the higher members
of the kingdom to which it belongs in